Estudio de la Geoquímica, la Estructura y el Metamorfismo en el

Universidad Nacional Autónoma de México

Centro de Geociencias

Programa de Posgrado en Ciencias de la Tierra

Estudio de la Geoquímica, la Estructura y elMetamorfismo en el Este del Complejo

Acatlán: Implicaciones Tectonicas yPaleogeograficas

——Continental arc development along the periphery of

Pangea: Late Paleozoic pluton emplacement and basinevolution in a transtensional setting, eastern Acatlán

Complex, Mexico

Moritz Kirsch

Tesis sometida en cumplimiento parcialde los requisitos para el grado de

Doctor en Ciencias de la Tierra

ASESORES:Dr. J. Duncan KeppieDr. J. Brendan Murphy

JURADO EXAMINADOR:Dra. Elena Centeno-García

Dr. Peter SchaafDr. J. Duncan Keppie

Dr. Luca FerrariDr. Michelangelo Martini

Juriquilla, Qro, México Agosto, 2012

Moritz Kirsch: Estudio de la Geoquímica, la Estructura y el Metamorfismo enel este del Complejo Acatlán: Implicaciones Tectonicas y Paleogeograficas, TesisDoctoral c© Agosto, 2012

En memoria cariñosa de mis abuelos Otto y Ruth Kirsch, y mi abueloSiegfried Schröder.

R E S U M E N

En el sector este del Complejo Acatlán, sur de México, se encuentra unconjunto de rocas de edad Paleozoico tardío, compuesto por un cuerpo in-trusivo de la asamblea gabro-diorita-tonalita-trondhjemita (plutón Totolte-pec) y una secuencia clástica-calcárea de bajo grado de metamorfismo (for-mación Tecomate). Estas rocas fueron emplazadas y depositadas despuésde la orogenia colisional asociada a la formación de Pangea. Por lo tanto, elárea de estudio ofrece la oportunidad de investigar procesos geológicos endiferentes niveles corticales de un arco magmático en la periferia de Pangeadurante el tiempo crucial entre amalgación y rotura del supercontinente.

El plutón Totoltepec con una superficie de afloramiento de 15 × 5 km estálimitado por dos fallas Pérmicas dextrales con orientación N–S, al sur poruna cabalgadura E–W con buzamiento norte, y al norte por una falla normalE–W. El plutón está compuesto por rocas máficas–ultramáficas subordina-das (306 ± 2 Ma; análisis concordante de U-Pb en circón) que afloran enel margen de la intrusión máfica–felsica principal (289 ± 2 Ma). La geoquí-mica de las rocas marginales muestra una afinidad toleítica a calco-alcalinacon alto LILE/HFSE (elementos litófilos de radio iónico grande/elementosde alto potencial iónico), tierras raras de espectro plano y valores inicialesde εNd entre +1.3 y +3.3. Los elementos traza de la fase plutónica másjoven describen una afinidad calco-alkalina con espectros de tierras rarasmoderadamente fraccionados y valores iniciales de εNd entre -0.8 a +2.6,lo cual también sugiere un ambiente de arco para su formación. Datos ter-mobarométricos indican que el cuerpo principal del plutón fue emplazadoa 620 km de profundidad y una temperatura de >700

◦C, y fue exhumadoa 11 km y 400

◦C en 4 ± 2 Ma. Se ha documentado la siguiente secuenciaintrusiva: (i) la fase máfica del margen norte de 306 Ma, (ii) la fase principaltrondhjemítica de 287 Ma, y (iii) diques subverticales de approx. 289–283

Ma que varian desde (a) N39◦E, no-deformados con crecimiento de cris-

tales perpendiculares a las márgenes, a (b) approx. N50–73◦E, foliados y

plegados con indicadores cinemáticos sinistrales, hasta (c) N73–140◦E con

estructuras tipo boudinage. La obliquidad del límite entre los diques ple-gados y estirados en relación a fallas dextrales de rumbo N-S sugiere unemplazamiento secuencial en un ambiente transtensional con 20 % de ex-tensión con dirección E-W, pasando por un campo de acortamiento bajodiferentes grados de rotación en sentido horario, acompañado por cizalla-miento lateral izquierdo, a un campo de extensión. La intrusión de approx.289–287 Ma contiene una foliación subvertical de rumbo ENE y un linea-miento que varia de subhorizontal a muy inclinada, probablemente debidoal emplazamiento en un ambiente de deformación triclínica. Se infiere queel magmatismo cesó cuando un componente de movimiento fue transferidode la falla del límite occidental a la falla del límite oriental, resultando en

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un cabalgamiento a lo largo del límite sur del plutón. Este mecanismo pue-de explicar el rápido levantamiento y exhumación del plutón entre approx.287 y 283 Ma.

La formación Tecomate se define actualmente como un compuesto deunidades de litología similar, depositadas desde el Carbonífero hasta el Pér-mico en múltiples cuencas limitadas por fallas. Al sur del plutón Totoltepec,la edad de depositación de la formación Tecomate está bien definida en ∼300

Ma en una sección, y entre ∼288 y ∼263 Ma en otra. Las rocas de la forma-ción Tecomate están interpretadas como derivados de un arco magmáticodel Paleozoico tardío, basandose en (i) su geoquímica de afinidad de arco,(ii) valores εNd(t) entre -5.6 a +0.3 (t = 288 Ma) que traslapan los del plu-tón Totoltepec, y (iii) una población dominante de circones con edades quevarian de Carbonífero a Pérmico. Las unidades de Totoltepec y Tecomateen el área de estudio forman parte de un arco continental que se extiendedesde Guatemala hasta California, lo cual implica subducción del paleo-Pacífico bajo el margen occidental en una configuración paleogeográfica dePangea-A.

A B S T R A C T

In the eastern Acatlán Complex of southern Mexico, a Late Paleozoicassemblage comprising a gabbro-diorite-tonalite-trondhjemite suite (Totol-tepec pluton) and clastic-calcareous metasedimentary rocks (Tecomate For-mation), post-dates collisional orogeny that resulted in the amalgamationof Pangea. This region offers a rare opportunity to examine assemblagesdeveloped at different crustal levels of a magmatic arc along the peripheryof Pangea at the critical stage between amalgamation and breakup.

The 15 x 5 km Totoltepec pluton is bounded by two N–S Permian dex-tral faults, an E–W thrust to the south, and an E–W normal fault to thenorth. The pluton consists of minor mafic–ultramafic rocks (306 ± 2 Ma;concordant U-Pb zircon analysis) that are marginal to the main mafic–felsicintrusion (289 ± 2 Ma). Geochemistry of the marginal rocks indicates anarc tholeiitic to calc-alkaline character with high LILE/HFS, flat REE pat-terns and initial εNd values of +1.3 to +3.3. The younger Totoltepec phaseexhibits a calc-alkaline trace element geochemistry with flat to moderatelyfractionated LREE enriched patterns, and initial εNd values of -0.8 to +2.6,which are also consistent with an arc environment. Thermobarometric dataindicate that the main, ca. 289–287 Ma part of the pluton was emplaced at620 km depth and >700

◦C, and was exhumed to 11 km and 400◦C in 4

± 2 Ma. The following intrusive sequence is documented: (i) the 306 Manorthern marginal mafic phase; (ii) the 287 Ma main trondhjemitic phase;and (iii) ca. 289–283 Ma subvertical dikes that vary from (a) N39

◦E, unde-formed with crystal growth perpendicular to the margins, through (b) ca.N50–73

◦E, foliated and folded with sinistral shear indicators, to (c) N73–140◦E and boudinaged. The obliquity of the boundary between the folded

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and stretched dikes relative to the N-S dextral faults suggests sequential em-placement in a transtensional regime (with 20 % E–W extension), followedby different degrees of clockwise rotation passing through a shortening fieldaccompanied by sinistral shear into an extensional field. The ca. 289–287 Maintrusion also contains a steep ENE-striking foliation, and hornblende linea-tions varying from subhorizontal to steeply plunging, probably the result ofemplacement in a triclinic strain regime. We infer that magmatism ceasedwhen some of the dextral motion was transferred from the western to theeastern bounding fault, causing thrusting to take place along the southernboundary of the pluton. This mechanism is also invoked for the rapid upliftand exhumation of the pluton between ca. 287 and 283 Ma.

The Tecomate Formation, as currently defined, is a composite of lithologi-cally similar strata deposited in several fault-bounded basins ranging fromCarboniferous to Early Permian in age. To the south of the Totoltepec plu-ton, the depositional age of the Tecomate Formation is tightly constrained inone section to ∼300 Ma but in another section it is between ∼288 and ∼263

Ma. The Tecomate Formation rocks are interpreted to have been derivedfrom a Late Paleozoic arc based on (i) its arc-related geochemistry, (ii) εNd(t)values ranging from -5.6 to +0.3 (t = 288 Ma) that overlap those of the Totol-tepec pluton, and (iii) detrital zircons with predominantly Carboniferous–Permian ages. The Totoltepec and Tecomate units in the study area formpart of a continental arc extending from Guatemala to California, whichnecessitates subduction of the paleo-Pacific oceanic lithosphere beneath thewestern margin of a Pangea-A configuration.

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Oh du schönes, o du wunderschönes,uraltes, sagen- und liederreiches Land Mexiko!

Desgleichen gibt es nicht wieder auf dieser Erde.

— B. Traven

A G R A D E C I M I E N T O S

Me gustaría reconocer a J. Duncan Keppie y J. Brendan Murphy por susupervisión, paciencia, motivación y financiación. Me siento tremendamen-te afortunado de haber tenido la oportunidad de venir a México y traba-jar con ustedes. Además de la geología espectacular que me tocó estudiar,realmente fue una experiencia cultural, tal como se había prometido. Heaprendido mucho de ustedes dos en estos cuatro años—Brendan, me ense-ñaste la importancia de principios y procesos en la redacción científica, noperder nunca vista del panorama completo, hacer mil cosas al mismo tiem-po, mantener impulso, estar pendiente de muestras y atar cabos sueltos, serarticulado y organizado. Duncan, tu experiencia geológica y sentido de laorientación en el campo, tu humor, tu parsimonia y eficiencia en todas lascuestiones científicas y burocráticas eran una verdadera inspiración. Estoyconvencido de que me han preparado bien para una carrera como geólogohard-rock.

Además de los asesores de mi tesis, quisiera dar las gracias a todas lasdemás personas que han contribuido de una manera u otra a este trabajo.Maria Helbig, Mario A. Ramos-Arias, Gonzalo Galaz, y Domingo Schieve-nini donaron su tiempo y esfuerzo para asistirme en el campo y ayudar-me con la preparación de muestras. Luigi Solari, Consuelo Macías Romo,Carlos Linares, Carlos Ortega-Obregón, Ofelia Pérez-Arvizu, Aldo Izagui-rre, Alex Iriondo, y Harald N. Böhnel brindaron asistencia invaluable enel laboratorio. He beneficiado mucho de la colaboración y las conversacio-nes inspiradoras con Maria Helbig, Luigi Solari, James K. W. Lee, FraserKeppie, Uwe Kroner, Fernando Ortega-Gutiérrez, R. Damien Nance, CecilioQuesada, Roberto S. Molina-Garza, Barbara M. Martiny, James Sears, ChrisSmith, y Axel Renno. También me gustaría agradecer a los miembros de micomité tutoral: Luigi Solari, Fernando Ortega-Gutiérrez, Duncan Keppie,y Brendan Murphy, así como el comité de mi examen predoctoral: ElenaCenteno-García, Peter Schaaf, Gustavo Tolson, y Dante J. Morán Zentenopor su tiempo y el asesoramiento profesional. Peter Schaaf, Bodo Weber,Luca Ferrari, W. Gary Ernst, y dos revisores anónimos son reconocidos porproporcionar revisiones constructivas de los manuscritos de los artículosque forman parte de esta tesis. Gracias a Roberto S. Molina-Garza y MaríaClara Zuluaga Velez por tomarse el tiempo para corregir la versión españolade la tesis.

Deseo extender un agradecimiento especial a la secretaria académica Mar-ta Pereda Miranda y la abogada Lic. Ana Paola González Cruz del Centro

vii

de Geociencias. Sin su ayuda competente me hubiera perdido en la junglade la burocracia académica.

Agradezco al Consejo Nacional de Ciencia y Tecnología y a la DirecciónGeneral de Estudios de Posgrado de la UNAM por las becas otorgadaspara la realización de mis estudios de doctorado. Además agradezco laCoordinación de Posgrado por el apoyo financiero brindado en la impresiónde la tesis.

Por último, deseo expresar mi profundo y sincero agradecimiento a mispadres, Bettina y Frank-Michael, y sus respectivas parejas Michael Freitagy Heike Kirsch, mi hermana Steffi, mis abuelos Ruth y Otto, y Brigitta ySiegfried, que me han aconsejado y apoyado a lo largo de mi educación.Gracias también a los padres de María, Martina y Johannes Helbig, por sugenerosidad y su perspectiva fresca. A mis amigos, tanto aquí en México– Domingo, María de la O, Oscar, Lina, Lariza, Gianluca, Daniele, Matteo,Ramón, Alma, Mario, Fabián, y el equipo de básquet INDEREQ – como losamigos de mi tierra: Martin, Matt, Bob, Mathias, Mel, Paul, Jo, y Nadja: lesdebo demasiado. Gracias por todos los buenos momentos! Estoy especial-mente agradecido a mi novia Maria, por su amor, aliento y su compañía enesta aventura mexicana. Tú eres la luz de mi vida.

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Í N D I C E G E N E R A L

1 introducción 1

1.1 Marco geológico . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Motivación, objetivos y metodología . . . . . . . . . . . . . . . 5

2 geoquímica y geocronología de las unidades del carbo-nífero–pérmico 10

3 historia estructural del plutón totoltepec 33

4 eventos del paleozoico tardío hasta el mesozoico tem-prano en la periferia de pangea 58

5 resumen y conclusión 76

a métodos analíticos 80

a.1 Geocronología U-Pb . . . . . . . . . . . . . . . . . . . . . . . . 80

a.2 Geoquímica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

a.3 Geocronología 40Ar-39Ar . . . . . . . . . . . . . . . . . . . . . 81

b tablas geocronología u-pb 83

c tablas geoquímica 117

d tablas análisis de microsonda 138

e tablas geocronología40

ar/39ar 146

bibliografía 148

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1I N T R O D U C C I Ó N

Esta tesis se concentra en el estudio del plutón Totoltepec de edad Carbo-nífero–Pérmico y sus rocas encajonantes (parte del Complejo Acatlán), conénfasis en la geoquímica y el control estructural en el emplazamiento delplutón. A pesar de que la geoquímica publicada (basada en 6 muestras: Ma-lone et al., 2002) muestra una afinidad de arco, estos datos no fueron sufi-cientes para distinguir entre magmas formados en una zona de subduccióny magmas contaminados por la corteza continental (Pearce y Peate, 1995;Turner et al., 1996; Kuscu et al., 2010). Un muestreo más amplio y un conjun-to más exhaustivo de los elementos y los isótopos analizados constituyenla base para este estudio. Se obtuvieron datos geocronológicos adicionalesde U-Pb para determinar la edad y duración del evento de intrusión, com-plementándose con edades de 40Ar/39Ar para conocer también la historiatectono-térmica. El estudio además incluye análisis geocronológicos y geo-químicos de las rocas sedimentarias contemporáneas a la intrusión para loscuales no existían ningunos datos de este tipo. Aunque estudios anterioreshan sugerido que el emplazamiento del plutón Totoltepec fue sintectónico,los controles estructurales no eran conocidos. La base de datos mejoradaque aporta este estudio permite el desarrollo de un modelo estructural parael emplazamiento del plutón. Estas conclusiones se utilizan para documen-tar el desarrollo de un arco regional y para diferenciar entre los diferentesmodelos paleogeográficos para el Complejo Acatlán con respecto a Pangea(Keppie et al., 2010; Vega-Granillo et al., 2009; Böhnel, 1999).

1.1 marco geológico

Con una extensión superficial que supera los 10,000 km2, el ComplejoAcatlán de edad Ordovícico al Pérmico Medio constituye el basamento delterreno Mixteca y el mayor afloramiento de rocas paleozoicas en México(Ortega-Gutiérrez, 1978; Campa y Coney, 1983; Sedlock et al., 1993; Keppie,2004). Las rocas expuestas en la región de Acatlán registran una historiapaleozoica tectonotermal muy compleja que refleja la apertura y el cierrede una o más cuencas oceánicas y sus consiguientes interacciones continen-tales que culminaron en la amalgamación de Pangea (por ejemplo, Nanceet al., 2006). Estos eventos fueron acompañados por subducción durante elDevónico hasta el Pérmico a lo largo del sur de México (Keppie et al., 2008).

El Complejo Acatlán está limitado al este por la falla de Caltepec, una zo-na de cizalla con dirección N–S y mecanismo dextral, que lo separa de losgneises en facies de granulita de ∼1.0 Ga del Complejo Oaxaqueño (Elías-Herrera y Ortega-Gutiérrez, 2002). Al sur, está limitado por la falla Cenozoi-ca La Venta-Chacalapa (Tolson, 2007; Solari et al., 2007), que lo yuxtapone

1

1.1 marco geológico 2

contra las rocas plutónicas y metamórficas de alto grado del Complejo Xo-lapa (Pérez-Gutiérrez et al., 2009). Hacia el oeste, sobreyace en forma de ca-balgadura sobre carbonatos cretácicos de la plataforma Guerrero-Morelos,que están expuestos entre el Complejo Acatlán y el terreno compuesto deGuerrero (Centeno-García et al., 2008; Ramos-Arias y Keppie, 2011). Haciael norte, se encuentra cubierto discordantemente por rocas sedimentariasde origen continental y marino de edad Pérmico Superior–Jurásico Medio(Morán-Zenteno et al., 1993; Centeno-García et al., 2009), así como por rocasvolcánicas y volcaniclásticas del Mioceno Medio y Tardío de la Faja Volcá-nica Transmexicana (Ferrari et al., 1999).

El área de estudio se encuentra en la parte oriental del Complejo Acatlán,a unos 30 km al este de Acatlán de Osorio (estado de Puebla). Está limitadode forma aproximada por los pueblos Xayacatlán de Bravo al oeste, SantoDomingo Tianguistengo al este y San José Chichihualtepec al sur. Las ro-cas estudiadas ocurren en el bloque tectónico Tonahuixtla (Morales-Gámezet al., 2009), que está limitado en ambos lados por fallas normales-dextralesde rumbo N–S. En base a los mapas geológicos publicados (Ortega-Gutiérrez,1978; Malone et al., 2002; Keppie et al., 2004a), la estratigrafía del área de es-tudio está conformada por las siguientes unidades litotectónicas: el plutónTotoltepec, la Formación Tecomate y la Formación Cosoltepec. A continua-ción se resumen los datos publicados sobre cada una de estas unidades yse identifican las problemáticas científicas que se tratan de resolver en esteestudio.

El plutón Totoltepec, con una superficie de afloramiento de 15 × 5 km,constituye la parte central del área de estudio. El cuerpo intrusivo fue nom-brado por Fries et al. (1970) y primero cartografiado por Ortega-Gutiérrez(1975), como parte de su trabajo pionero en el Complejo Acatlán. De acuer-do con Ortega-Gutiérrez (1978), el plutón está en contacto intrusivo conrocas del Subgrupo Acateco y la Formación Cosoltepec (Grupo Petlalcingo,Fig. 1). Por otro lado, Malone et al. (2002) y Keppie et al. (2004a) ubican elplutón Totoltepec en el bloque cabalgante de una gran falla, estructuralmen-te sobreyaciendo las formaciones Tecomate y Cosoltepec. Hacia el norte, elplutón está sobreyacido discordantemente por capas rojas deformadas, perosin metamorfismo, de edad inferida jurásica (Malone et al., 2002).

El plutón Totoltepec está conformado principalmente por diorita de horn-blenda, trondhjemita y tonalita (Malone et al., 2002). Las fracciones de cir-cón de una fase félsica han dado una edad concordante U-Pb TIMS de 287

± 2 Ma (Yañez et al., 1991), mientras que una fase máfica de la parte surdel plutón dio una edad U-Pb TIMS de 289 ± 1 Ma (Keppie et al., 2004a).Ortega-Gutiérrez (1975) ha documentado cuerpos de gneises máficos de es-tructura migmática y bandeada en el margen norte del plutón Totoltepec,que Calderón-García (1956) sospecha pertenecen al basamento de la zona.La edad de estas rocas máficas marginales y su significado geodinámico esdesconocido.

Una cantidad limitada de datos estructurales del plutón (Malone et al.,2002; Morales-Gámez et al., 2009) sugieren la presencia de una foliación de


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299

318

359

385

398

416428423444

461

472488501

510521

542

245235

Fm. CosoltepecFm. Xay-acatlán

FormaciónPatlanoaya(Dev. tardío –Pérmico medio)

GrupoPatlanoaya

& Fm.Tecomate

Fm. Chazumba

Gru

po P

iaxt

la

Mig. Magdalena

Orogenia Acateca(facies eclogita)

Fm. TecomategranitoidesEsperanza

PlutónLa Noria

(337±34 Ma)

PlutónTotoltepec (287±2 Ma)

PlutónTotoltepec

Orogenia Mixteca(facies esquisto verde)

Exumaciónde rocas de alta presión

(facies eclogita)

Evento Orogénico(facies esquisto verde)

Ortega-Gutiérrez et al. (1999)

Huerta, Amate, Las

Minas

magmatismobimodal

(480–440 Ma)

Nance et al. (2006)Keppie et al. (2008)

Unidad Salada ,

Cosoltepec

(440±14 Ma)

Grupo

Petlalcingo

P

C

D

S

O

_

^

Figura 1: Diagrama de relaciones espaciales y temporales que muestra la tectono-estratigrafía tradicional (izquierda) y revisada (derecha) del ComplejoAcatlán. Figura modificada de Ortega-Gutiérrez et al. (1999); Nance et al.(2006); Keppie et al. (2008).

rumbo norte y buzamiento de alto ángulo, así como pliegues de direcciónN–S, por cual la foliación se encuentra plegada a nivel local. Además, Malo-ne et al. (2002) sugieren que el emplazamiento del plutón puede haber sidosintectónico con respecto a la deformación regional.

Datos geoquímicos de un estudio de reconocimiento de rocas del putónTotoltepec reflejan una afinidad calco-alcalina (Malone et al., 2002). Isotópi-camente, el plutón Totoltepec ha dado valores de εNd(t) más positivos yedades modelo TDM más jóvenes (Yañez et al., 1991) en comparación a plu-tones contemporáneos en el sur de México, lo que indica que proviene deuna fuente de carácter más juvenil. La intrusión ha sido interpretada comoparte de un arco continental Pérmico–Triásico que se extiende a lo largo deMéxico centro-oriental (Torres et al., 1999; Malone et al., 2002; Keppie et al.,2004a). Alternativamente, de acuerdo con su modelo paleogeográfico, Vega-Granillo et al. (2009) consideran el plutón como un producto de la colisióncontinental y una expresión local de la orogenia Ouachita-Alleganiana.

La Formación Tecomate, originalmente definida por Rodríguez-Torres(1970), es una unidad clástica ligeramente metamorfoseada, pero intensa-mente deformada que consiste en alternancias de rocas psammiticas-pelíti-cas, mármoles y conglomerados de cantos rodados, así como rocas volcáni-cas que principalmente están formadas por flujos y tobas con escasas unida-des félsicas (Ortega-Gutiérrez, 1993; Sánchez-Zavala et al., 2000). En su áreatipo, la Formación Tecomate ocurre en una zona de cizalla subvertical deorientación N–S situado entre la ciudad de Acatlán de Osorio y el pueblode El Tecomate (Ortega-Gutiérrez, 1975), pero rocas correlacionables con la


Formación Tecomate también afloran localmente en los sectores norte y es-te (por ejemplo, Ortega-Gutiérrez et al., 1999), así como el sector oeste delComplejo Acatlán (Talavera-Mendoza et al., 2005; Vega-Granillo et al., 2009).Según mapas geológicos publicados de la zona de estudio, la FormaciónTecomate está en contacto con el plutón Totoltepec en su margen sur y este(Ortega-Gutiérrez et al., 1999), así como en sus bordes suroriente y oeste(Keppie et al., 2004a).

La edad de depositación de la Formación Tecomate es sujeto de controver-sia. Originalmente, se infirió como Devónica (Fig. 1) basada principalmenteen la presencia de equinodermos, crinoides, blastoideos y micromoluscosde edad pre-Carbonífero obtenidos en esta unidad (Ortega-Gutiérrez, 1993)y en la interpretación de que la formación está intruida por el granito LaNoria (Ortega-Gutiérrez et al., 1999), de los cuales datos U-Pb (circón) in-dicaban una edad Devónico Tardío. Sin embargo, más recientemente, lafauna recuperada de tres horizontes diferentes de mármol ha permitidoprecisar una edad pérmica temprana a media para la depositación de laFormación Tecomate en el área tipo (Keppie et al., 2004b). Estas restriccio-nes paleontológicos han sido corroboradas por edades U-Pb SHRIMP deaproximadamente 320–264 Ma de circones separados de cantos de granitoen los metaconglomerados de la Formación Tecomate en la parte orientaldel Complejo Acatlán. Sin embargo, datos geocronológicos publicados dela Formación Tecomate (Keppie et al., 2004b; Sánchez-Zavala et al., 2004;Talavera-Mendoza et al., 2005) sugieren que la unidad, como se define ac-tualmente, puede ser de diferentes edades en diferentes lugares.

La Formación Tecomate ha sido interpretada como un sedimento sino-rogénico depositado posterior al emplazamiento de una capa cabalgante(Ortega-Gutiérrez, 1993; Weber et al., 1997), una secuencia turbidítica rela-cionada a un arco volcánico depositado en la zona frontal de una colisiónde arco-continente (Sánchez-Zavala et al., 2000), un depósito de arco y deextensión intracontinental (Talavera-Mendoza et al., 2005) y un sedimentomarino somero de ante-arco (Keppie et al., 2004b).

Basado en el traslape de las edades de depósito y similitudes faunísticas,la Formación Tecomate se ha correlacionado con la Formación San SalvadorPatlanoaya de edad Devónico Superior a Pérmico Inferior en la parte nortedel Complejo Acatlán (Keppie et al., 2004b). Sin embargo, a diferencia de laFormación Tecomate que ha sido deformada en forma penetrativa y afecta-da por metamorfismo en facies del esquisto verde, la Formación Patlanoayano está metamorfoseada y casi no ha sido deformada.

Mediciones de la forma de clastos en metaconglomerados de la Forma-ción Tecomate en el área de estudio cerca de San José Chichihualtepec handado esferoides alargados, con dimensiones típicos de la deformación trans-tensional (Morales-Gámez et al., 2009). Una edad 40Ar/39Ar de 263 ± 3 Mapara una filita sericítica de la Formación Tecomate adyacente a la zona deestudio ((Morales-Gámez et al., 2009) define el límite de edad de esta de-formación. Adicionalmente, se ha documentado cizallamiento lateral N–Sentre aproximadamente 307 y 269 Ma a lo largo de la falla Caltepec (Elías-

1.2 motivación, objetivos y metodología 5

Herrera y Ortega-Gutiérrez, 2002; Elías-Herrera et al., 2005). El significadodel mecanismo y los límites temporales de la deformación con respecto a laconfiguración paleogeográfica regional y su papel en el emplazamiento delplutón Totoltepec permanecen inexplorados.

Se ha reportado que la Formación Cosoltepec aflora en la parte sur dela zona de estudio, donde está en contacto con el plutón Totoltepec en susmárgenes sur y oeste (Ortega-Gutiérrez, 1978; Ortega-Gutiérrez et al., 1999;Malone et al., 2002). En el mapa geológico de Keppie et al. (2004a), las rocasde la Formación Cosoltepec sólo afloran en una zona estrecha a lo largodel límite suroeste del plutón Totoltepec. La Formación Cosoltepec está de-finida como una secuencia monótona de metapelitas y metapsamitas conescasas intercalaciones de anfibolita. Originalmente la unidad fue incluidaen el Grupo Petlalcingo de edad Cámbrico–Ordovícico (Ortega-Gutiérrez,1978), pero trabajos geocronológicos recientes han identificado grupos decircones detríticos más jóvenes de edad Ordovícico (∼455 Ma: Keppie et al.,2004a, 2006), Devónico-Carbonífero (∼410 y/o ∼374 Ma: Talavera-Mendozaet al., 2005), o de edad Carbonífero (∼352 Ma: Morales-Gámez et al., 2008)en las unidades asignadas originalmente a la Formación Cosoltepec; estoindica que está compuesta por diferentes unidades. El ambiente tectónicopara la depositación de las rocas de la Formación Cosoltepec sigue siendoparte de la discusión en curso, ya que la unidad ha sido interpretada co-mo un prisma de acreción (Ortega-Gutiérrez et al., 1999), una secuencia delmargen pasivo (Talavera-Mendoza et al., 2005; Vega-Granillo et al., 2007) oun depósito de la eminencia continental (Keppie et al., 2006).

1.2 motivación, objetivos y metodología

Basado en una serie de estudios de reconocimiento del área (por ejem-plo, Yañez et al., 1991; Malone et al., 2002; Keppie et al., 2004a,b), el plutónTotoltepec y la Formación Tecomate son propuestos como pertenecientes aun arco magmático continental del Pérmico–Triásico que se extiende desdeel suroeste de los Estados Unidos y continua a lo largo de México centro-oriental (Centeno-García y Silva-Romo, 1997; Torres et al., 1999; Dickinsony Lawton, 2001). Sin embargo, la existencia de este arco se basa en (i) unacantidad limitada de datos geocronológicos, la mayoría de los cuales se hanobtenido utilizando métodos isotópicos K-Ar y Rb-Sr (por ejemplo, Torreset al., 1999; Schaaf et al., 2002; Yañez et al., 1991) que son conocidos por serindicadores menos confiables para establecer la edad de cristalización de unplutón en comparación a la geocronología U-Pb de circones (por ejemplo,Steiner y Walker, 1996), y (ii) escasos datos geoquímicos de rocas ígneas delPaleozoico tardío en México (Torres et al., 1999; Solari et al., 2001; Maloneet al., 2002; Rosales-Lagarde et al., 2005; Arvizu et al., 2009). Por otra parte,una firma geoquímica de arco en las rocas ígneas de composición félsicae intermedia suele interpretarse como una evidencia directa de magmatis-mo de arco contemporáneo. Sin embargo, modelos para la generación demagma intermedio y silícico incluyen tanto la diferenciación de magmas


máficos derivados del manto por cristalización fraccionada dentro de lacorteza o el manto superior (por ejemplo, Gill, 1981), como la fusión parcialde rocas de la corteza pre-existente (por ejemplo, Thompson, 1982). Por lotanto, una firma geoquímica de arco en rocas ígneas de composición félsi-ca o intermedia puede ser adquirido como resultado de la subducción delitosfera oceánica (por ejemplo, Pearce y Peate, 1995), o por la fusión dela corteza continental que ha sido generada por procesos de subducción(por ejemplo, Turner et al., 1996; Kuscu et al., 2010). La composición isotópi-ca y/o la abundancia de xenolitos de granulita en las rocas ígneas que seutilizaron para definir el arco magmático continental del Pérmico–Triásicoindican que están significativamente contaminados por la corteza continen-tal. El terreno Oaxaquia, que incluye rocas de aproximadamente 1.0 Ga delnúcleo cristalino de México, registra un episodio de magmatismo de arcoentre aproximadamente 1300 y 1200 Ma (Keppie y Ortega-Gutiérrez, 2010).Por lo tanto, las abundancias de los elementos exhibidos por las rocas dearco principalmente félsicas, derivados de la corteza o contaminados queintruyen el basamiento de tipo Oaxaquia, puede reflejar una herencia enlugar de una firma de arco original. Antes de poder utilizar estas rocaspara reconstruir la evolución de un arco magmático, el origen de la firmageoquímica con respecto a la generación de magmas félsicos tiene que serevaluado críticamente. Se necesitan más datos y una evaluación rigurosade éstos para demostrar de manera incuestionable la existencia de un arcoregional del Paleozoico tardío. En este estudio, datos geocronológicos, geo-químicos y estructurales del plutón Totoltepec son combinados con datosgeoquímicos y geocronológicos de rocas volcaniclásticas contemporáneasde la Formación Tecomate, para proporcionar un modelo de los procesosrelacionados con la subducción en diferentes niveles de la corteza y ade-más refinar las características temporales y espaciales, así que la evolucióndel arco propuesto.

En cinturones orogénicos el plutonismo granitoide se presenta con fre-cuencia asociado espacial y temporalmente con sitios de deformación acti-va (Hutton, 1988), donde el ascenso y el emplazamiento de magma puedenser controlados por zonas de cizallamiento de niveles corticales profundos(Brown y Solar, 1998). En un estudio de reconocimiento, Malone et al. (2002)observaron que los diques que cortan la foliación de forma oblicua en el plu-tón Totoltepec contienen una foliación interna paralela a sus márgenes deldique, lo que sugiere un posible emplazamiento sintectónico con respec-to a la deformación regional. Sin embargo, no existen datos estructuralesdefinitivos que establezcan los plazos de la deformación en relación al es-tado de cristalización del plutón (siguiendo los criterios de, por ejemplo,Blumenfeld y Bouchez, 1988; Paterson et al., 1989, 1991; Miller y Paterson,1994) para sustanciar la naturaleza sin-cinemática de intrusión. Mostrar queel emplazamiento del plutón fue acompañado por deformación regional esde suma importancia, ya que los plutones sintectónicos bien datados sepueden utilizar para evaluar la temporalidad, el mecanismo y la historiatérmica de la deformación regional (por ejemplo, Ingram y Hutton, 1994;


Tribe y D’Lemos, 1996). Teniendo en cuenta los trabajos anteriores, que hanrelacionado el plutón Totoltepec con un arco magmático regional, un plutónemplazado sintectónicamente marcaría un lugar excepcionalmente adecua-do para investigar la cinemática y el desarollo geodinámico de un sistemade falla en un arco continental antiguo y explorar la relación entre el mag-matismo granitoide y la deformación en un margen de placa convergente.Este estudio demuestra que el emplazamiento fue contemporáneo con la de-formación, proporciona límites en cuanto a profundidad de emplazamiento,tasa de exhumación e historia de enfriamiento del plutón, empleando unacombinación de geocronología U-Pb y 40Ar/39Ar, el análisis de meso y mi-crofábrica y de termobarometría de aluminio en hornblenda. Además, elestudio identifica el desarrollo de las fábricas, la secuencia temporal y losmecanismos de emplazamiento de las diversas fases intrusivas. Por otraparte, se desarrolla un modelo que pretende explicar el emplazamiento delplutón en el contexto de fallamiento regional de orientación N–S y meca-nismo transcurrente-dextral. Estos datos ayudan a entender la cinemáticadel sistema de fallas que permitió el emplazamiento y la exhumación delplutón como un medio para reconstruir la evolución geodinámica del arcomagmático del Paleozoico tardío.

Existen dos modelos en competencia concernientes a la posición paleo-geográfica del terreno Mixteco en relación a la configuración de Pangea enel Paleozoico. Keppie et al. (2010) y Weber et al. (2007) ubican el terreno Mix-teca en el margen activo occidental de Pangea, mientras que Vega-Granilloet al. (2009) consideran que el terreno se ubicó en la zona de colisión en-tre Gondwana y Laurentia. Un tercer modelo, que se basa en un modeloalternativo de Pangea (Pangea-B, Irving, 1977; Morel y Irving, 1981) invo-cando un mega-sistema de cizallamiento dextral, coloca el terreno Mixtecafrente al nordeste de Canadá en el Jurásico (Böhnel, 1999). Por lo tanto,la ubicación del terreno Mixteca en el sur de México en las reconstruccio-nes paleogeográficas del Paleozoico tardío tiene implicaciones profundaspara las hipótesis Pangea-A y -B. En este estudio, se evalúan los diferen-tes escenarios; la evaluación se basa en determinar la fuente de magmay el mecanismo de emplazamiento del plutón Totoltepec, así como el am-biente tectónico y la procedencia de la Formación Tecomate. A su vez, es-to permite evaluar el significado geodinámico de estas rocas en relacióncon la amalgamación y la desintegración de Pangea. Dependiendo de si laubicación paleogeográfica del terreno Mixteca en el Paleozoico tardío eraperiférica o interna con respecto a Pangea, el magmatismo y los procesosde formación de cuenca caracterizados por el plutón Totoltepec y la For-mación Tecomate representan eventos relacionados a la subducción en unorógeno periférico del tipo andino, o eventos colisionales parecidos a las dela orogenia Ouachita-Alleganiana en el sur de los Apalaches. Estos procesosdel Paleozoico tardío en cualquier de los dos ambientes tectónicos posiblesson pertinentes a un proceso importante de escala global que involucra latransferencia de las zonas de subducción desde el interior de Pangea a laperiferia (por ejemplo, Murphy y Nance, 2008; Murphy et al., 2009).


En la primera sección de este trabajo se presentan los datos geológicos decampo, petrografía, geocronología U-Pb de circones y geoquímica de ele-mentos mayores y trazas, así como geoquímica isotópica de Sm-Nd parael plutón Totoltepec y la Formación Tecomate de la zona de estudio. Lasdescripciones detalladas de las metodologías están incluidas en el Apén-dice A.1. Las edades de cristalización de las fases plutónicas y las edadesdetríticas de las rocas metasedimentarias fueron obtenidas por medio de laablación láser (LA-ICP-MS) en el Laboratorio de Estudios Isotópicos (LEI),Centro de Geociencias, UNAM. Los granos de circón fueron separados utili-zando diferentes protocolos analíticos con el fin de maximizar la pureza delconcentrado obtenido, así como minimizar cualquier sesgo. Se realizaronobservaciones por catodoluminiscencia (CL) antes de los análisis LA-ICP-MS para ayudar a la selección de puntos y para aumentar la interpretabi-lidad geológica de los resultados. Los datos de edad son utilizados paraestablecer la secuencia de intrusión del plutón Totoltepec, la edad máximade sedimentación y la procedencia de la Formación Tecomate en el área deestudio. Los datos geoquímicos (véase el Apéndice A.2 para detalles me-todológicos), obtenidos del Regional Geochemical Centre de Saint Mary’sUniversity en Nueva Escocia, Canadá, se utilizan para evaluar el ambientetectónico del plutón Totoltepec y la Formación Tecomate. Datos isotópicosde Sm-Nd, adquiridos del Atlantic Universities Regional Isotopic Facility(AURIF), Memorial University en Terranova, Canadá, se emplean como tra-zador tectónico para investigar la fuente de magma del plutón Totoltepec ypara proporcionar información sobre la procedencia de las rocas de la For-mación Tecomate; éstos complementan los datos geocronológicos. Tambiénse incluye una revisión de los datos geocronológicos, geoquímicos e isotó-picos de los sistemas magmáticos aproximadamente coetáneos en México yGuatemala así como propios datos geoquímicos e isotópicos de los plutonesCozahuico y La Carbonera en el Complejo Oaxaqueño.

La segunda sección de la tesis contiene datos meso- y micro-estructurales,petrográficos, de microsonda, termobarométricos y geocronológicos del plu-tón Totoltepec; éstos se utilizan para investigar la historia de emplazamientodel plutón y su significado en el desarrollo geodinámico del arco continen-tal del Paleozoico tardío en el sur de México. Se llevó a cabo un extensotrabajo de campo para documentar las relaciones de contacto internos yexternos al plutón, recabar datos estructurales, así como muestrear parasecciones delgadas, análisis de microsonda y análisis geocronológicos. Lasobservaciones petrográficas de láminas delgadas y los análisis de microson-da se utilizan para examinar la asociación de fases y para determinar lacomposición de algunos minerales. La historia de la deformación del plu-tón está reconstruida sobre la base de microestructuras distintivas que sedesarrollan por diferentes mecanismos de recristalización dinámica. Con elfin de obtener una estimación de la profundidad del emplazamiento y latasa de exhumación, se emplea una combinación de termobarometría Al-en-hornblenda y dataciones por el método 40Ar/39Ar. Los datos químicosde plagioclasa y hornblenda coexistente fueron obtenidos mediante micro-


sonda electrónica y espectrometría de dispersión por longitud de onda enel Laboratorio Universitario de Petrología (LUP) del Instituto de Geofísica(UNAM) en la Ciudad de México. Los fechamientos de moscovita median-te 40Ar/39Ar se llevaron a cabo por un procedimiento de calentamientoen pasos con láser en el Geochronology Research Laboratory de Queen’sUniversity en Kingston, Canadá (véase el Apéndice A.3 para las especifica-ciones técnicas y detalles del método analítico). En conjunto, estos datos seutilizan para explicar la intrusión, deformación y exhumación del plutónen el contexto del marco estructural regional.

La tercera sección está constituida por una guía de una excursión geo-lógica, publicada como parte del Programa Internacional de CorrelaciónGeológica Proyecto 597 (IGCP—amalgamación y ruptura de Pangea) y la108

a Reunión Anual de la Sección Cordillerana del GSA en Querétaro, Mé-xico (28 a 31 marzo 2012). La guía da una visión general de los eventos delPensilvánico–Jurásico en la periferia de Pangea. El capítulo correspondientea la zona de estudio describe las relaciones de campo en una serie de aflo-ramientos considerados principales y resume datos publicados. Además,contiene datos nuevos de geocronología U-Pb y 40Ar/39Ar, geoquímica ygeoquímica isotópica Sm-Nd.

2G E O Q U Í M I C A Y G E O C R O N O L O G Í A D E L A S U N I D A D E SD E L C A R B O N Í F E R O – P É R M I C O

Artículo: Kirsch, M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permi-an–Carboniferous arc magmatism and basin evolution along the westernmargin of Pangea: geochemical and geochronological evidence from theeastern Acatlán Complex, southern Mexico: Geological Society of AmericaBulletin, en prensa, doi: 10.1130/B30649.1.

Contribuciones individuales de los autores:

Moritz Kirsch: concepción y diseño del estudio; trabajo de campo elcual incluye mapeo, selección de puntos de muestreo y toma de mues-tras para análisis de geoquímica y geocronología U-Pb; adquisición delos datos LA-ICP-MS, incluyendo la separación de circones y catodo-luminiscencia; revisión de literatura; análisis e interpretación de datos;redacción del artículo.

J. Duncan Keppie: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.

J. Brendan Murphy: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.

Luigi A. Solari: participación en la interpretación de datos y en la revi-sión del artículo remitido; responsable de las instalaciones de análisisLA-ICP-MS.

10

Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea: Geochemical and geochronological

evidence from the eastern Acatlán Complex, southern Mexico

Moritz Kirsch1,†, J. Duncan Keppie2, J. Brendan Murphy3, and Luigi A. Solari1

1Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, QRO, Mexico2Departamento de Geología Regional, Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México D.F., Mexico3Department of Earth Sciences, St. Francis Xavier University, Antigonish, Nova Scotia B2G 2W5, Canada

ABSTRACT

In the Acatlán Complex of southern Mex-ico, a late Paleozoic assemblage, consisting of a gabbro-diorite-tonalite-trondhjemite suite (Totoltepec pluton) and clastic-calcareous metasedimentary rocks (Tecomate Forma-tion), postdates collisional orogeny that re-sulted in the amalgamation of Pangea. This region offers a rare opportunity to examine assemblages developed at different crustal levels along the periphery of Pangea at the critical stage between amalgamation and breakup. The Totoltepec pluton consists of minor mafi c-ultramafi c rocks (306 ± 2 Ma; concordant U-Pb zircon analysis) that are marginal to the main mafi c-felsic intrusion (289 ± 2 Ma). Geochemistry of the marginal rocks indicates an arc tholeiitic to calc-alka-line character with high large ion litho-phile elements (LILEs)/high fi eld strength elements (HFSEs), fl at rare earth element (REE) patterns, and initial εNd values of +1.3 to +3.3. The younger Totoltepec phase exhibits a calc-alkaline trace-element geo-chemistry with fl at to moderately fraction-ated light (L) REE–enriched patterns and initial εNd values of –0.8 to +2.6, which are also consistent with an arc environment. The Sm-Nd isotopic signature is more primitive compared to contemporaneous arc-related igneous rocks in southern Mexico, suggest-ing the pluton was emplaced in a less ma-ture, outboard part of the arc, and/or along a fault conduit. The Tecomate Formation, as currently defi ned, is a composite of lithologi-cally similar strata deposited in several fault-bounded basins ranging from Carboniferous to Early Permian in age. To the south of the

Totoltepec pluton, the depositional age of the Tecomate Formation is tightly constrained in one section to ca. 300 Ma, but in another sec-tion, it is between ca. 288 and ca. 263 Ma. The Tecomate Formation rocks are interpreted to have been derived from a late Paleozoic arc based on (1) arc-related geochemistry, (2) εNd(t) values ranging from –5.6 to +0.3 (t = 288 Ma) that overlap those of the Totoltepec pluton, and (3) detrital zircons with predomi-nantly Carboniferous–Permian ages. The Totoltepec and Tecomate units in the study area form part of a continental arc extending from Guatemala to California, which neces-sitates subduction of the paleo-Pacifi c oce-anic lithosphere beneath the western margin of a Pangea-A confi guration.

INTRODUCTION

Although it is accepted that Pangea had largely been assembled by the Carboniferous–Permian, two competing models have been proposed for the late Paleozoic confi guration of the supercontinent: Pangea-A, essentially the “Wege nerian” fi t (Bullard et al., 1965; Smith and Hallam, 1970), and Pangea-B (Irving, 1977; Morel and Irving, 1981; Muttoni et al., 2003), which is based on the paleomagnetic data in which Gondwana is positioned ~3000 km farther east relative to Laurasia. In paleogeo-graphic reconstructions of Pangea-A, southern Mexico occupies a position similar to its present location relative to North America (Figs. 1A and 1B; e.g., Fang et al., 1989; Alva-Valdivia et al., 2002), whereas in reconstructions of Pangea-B, southern Mexico is placed off eastern Canada during the Jurassic (Fig. 1C; Böhnel, 1999). There are also variants of the Pangea-A recon-struction, in which southern Mexico is either peripheral (Keppie, 2004; Keppie et al., 2008a, 2010; Fig. 1A) or internal to Pangea, between

the Maya terrane and the southern United States (Talavera-Mendoza et al., 2005; Vega-Granillo et al., 2007, 2009; Fig. 1B).

Based on reconnaissance studies (e.g., Keppie et al., 2004a), the Totoltepec pluton and the Tecomate Formation in the eastern Acatlán Complex (Mixteca terrane) of southern Mexico are inferred to be part of a late Paleozoic con-tinental arc assemblage that extended from the south ern United States through Mexico to the northern Andes (Torres et al., 1999; Dickinson and Lawton, 2001). Alternatively, in accordance with their hypothesized within-Pangea location, Vega-Granillo et al. (2009) attributed late Paleo-zoic tectonothermal events in southern Mexico (including the eastern Acatlán Complex) to be related to continental collision (Alleghanian orogeny). In order to test the validity of these contrasting models, we investigated the tectonic setting of the Totoltepec pluton and Tecomate Formation using a combination of new geo-chemical, isotopic, and geochronological data. Examining magmatic systems in conjunction with sedimentary rocks enables the expression of tectonic events at different crustal levels to be documented.

Almost all of the crystallization ages of plu-tons used by Torres et al. (1999) to constrain the age of the hypothesized magmatic arc were obtained using K-Ar or Rb-Sr isotopic methods, which are known to be susceptible to postcrystallization processes and hence may be less precise than U-Pb zircon geochronology in obtaining ages of magmatic crystallization. The central phase in the Totoltepec pluton has been investigated by reconnaissance U-Pb geo-chronology (Yañez et al., 1991; Keppie et al., 2004a). However, mafi c igneous rocks at the margin of the Totoltepec pluton have not been dated, so the age range of the pluton is not con-strained, and its regional signifi cance is unclear. Although the existence of a Permian–Triassic

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GSA Bulletin; September/October 2012; v. 124; no. 9/10; p. 1607–1628; doi:10.1130/B30649.1; 15 fi gures; 1 table; Data Repository item 2012220.

†E-mails: [email protected]; [email protected]

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Kirsch et al.

1608 Geological Society of America Bulletin, September/October 2012

arc in Mexico has been proposed (e.g., Torres et al., 1999; Dickinson and Lawton, 2001; Centeno-García, 2005), geochemical data of late Paleozoic igneous rocks that would test this pro-posal are scarce (Torres et al., 1999; Solari et al., 2001; Malone et al., 2002; Rosales-Lagarde et al., 2005; Arvizu et al., 2009). Thus, neither the age nor the geochemistry of the magmatism, which are both crucial in assessing its potential geodynamic connection to the evolution of Pan-gea, is precisely constrained. We present U-Pb geochronology coupled with geochemical and Sm-Nd isotopic data to refi ne the age range of the hypothesized late Paleozoic arc in southern Mexico and to assess its geo dynamic signifi -cance relative to the amalgamation and breakup of Pangea.

Sedimentary sequences containing detritus from an orogenic source provide complemen-tary data that can be used to constrain the role of basin formation as well as uplift and exhuma-tion of the crust during orogenesis. Conglomer-ates in the Tecomate Formation in the study area contain granitic pebbles (Keppie et al., 2004b), suggesting a potential linkage between magma-tism and basin evolution. However, based on the available data, it is unclear whether the Teco-mate Formation, which has been mapped on the basis of lithologic comparison, is the same age in different locations. In this paper, we investi-gate this possibility by providing U-Pb laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) age data of single detrital zircon grains to help constrain the depo-sitional age of the Tecomate Formation in the study area as well as enable a comparison with the equivalent data from the type area in the cen-tral Acatlán Complex. In addition, we combine these data with petrographic, geochemical, and Sm-Nd isotopic evidence to assess the prov-

enance and tectonic setting of these metasedi-mentary rocks.

Taken together, the data from the Totoltepec pluton and the Tecomate Formation constrain processes operating at different crustal levels at a critical time in the evolution of Pangea. These data also bear on the Pangea-A versus Pangea-B controversy and on the location of southern Mexico in reconstructions of Pangea. If indeed southern Mexico was in a periph-eral position with respect to Pangea in the late Paleo zoic (Pangea-A confi guration), then this region offers a rare opportunity to examine the subduction-related magmatic and basin-forming events after continental collision. If, on the other hand, the magmatism and basin for-mation refl ect collisional orogenesis (Pangea B confi guration), this region provides a record of these processes that can be compared with the Alleghanian orogeny in the Southern Appala-chians. Our results indicate that the Totoltepec pluton and Tecomate Formation were both situated on the outboard part of a regionally extensive Pennsylvanian–Permian continental arc, consistent with subduction of paleo-Pacifi c oceanic lithosphere beneath the western margin of North America in a Pangea-A confi guration.

GEOLOGICAL SETTING

The Acatlán Complex in southern Mexico is tectonically bounded to the east by the Permian Caltepec fault zone, which separates it from the ca. 1 Ga Oaxacan Complex (Elías-Herrera and Ortega-Gutiérrez, 2002), and to the south by the Cenozoic La Venta and Chacalapa faults (Tolson, 2007; Solari et al., 2007), juxtaposing it against the Xolapa Complex (Fig. 2). To the west, the Acatlán Complex is thrust over Cre-taceous platformal carbonates, located between the exposed Acatlán Complex and the emplaced

Guerrero terrane (Centeno-García et al., 2008; Ramos-Arias and Keppie, 2011). To the north, the complex is unconformably overlain by Meso zoic rocks and the Cenozoic Trans-Mexi-can volcanic belt (Ferrari et al., 1999).

The geological history of the Acatlán Com-plex was recently summarized by Keppie et al. (2008a) and Vega-Granillo et al. (2009) and is not repeated here. Despite differences in the interpretation of this history, all authors agree that the late Paleozoic events involved subduc-tion-related tectonothermal events; however, the polarity of subduction is debated, either eastward beneath Pangea (Keppie et al., 2008a) or northward beneath Laurentia (Vega-Granillo et al., 2009).

The Totoltepec pluton and the Tecomate For-mation both occur within the Tonahuixtla fault block (Morales-Gámez et al., 2009), which is bounded in the west by the N-S–trending dex-tral San Jerónimo fault (Fig. 3; Morales-Gámez et al., 2008), where the Tecomate Formation is tectonically juxtaposed against the Carbon-iferous Salada unit along N-striking, dextral-normal faults and above N-dipping shear zones (Morales-Gámez et al., 2008). In the east, the Totoltepec pluton and Tecomate Formation are delimited by the Tianguistengo normal fault (Fig. 3; Servicio Geológico Mexicano, 2001). Along its southern margin, the Totoltepec plu-ton is thrust over metasedimentary rocks of the Tecomate Formation (Malone et al., 2002). The southern limit of the Tecomate Formation is not exposed in the study area, but the unit is inferred to structurally overlie rocks of the Cosoltepec Formation further south (Malone et al., 2002). The Cosoltepec Formation was originally thought to have been deposited in the Cam-brian–Ordovician (Ortega-Gutiérrez, 1978), but recent geochronological data indicate that it is a composite of both Cambrian–Ordovician and

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A B CFigure 1. Paleogeographic reconstructions showing the location of the Mixteca terrane (Mx) in different confi gurations: (A) at the western margin of Pangea-A (modifi ed after Weber et al., 2007), (B) within Pangea-A (modifi ed after Vega-Granillo et al., 2009), or (C) off eastern Canada in the Jurassic (Pangea-B; modifi ed after Böhnel, 1999). Oax—Oaxaquia terrane; Coa—Coahuila terrane; CM—Chiapas Massif; CA—Colombian Andes.


Permian–Carboniferous arc magmatism and basin evolution along the western margin of Pangea

Geological Society of America Bulletin, September/October 2012 1609

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Kirsch et al.


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Devonian–Carboniferous units (Talavera-Men-doza et al., 2005; Keppie et al., 2006, 2008b; Morales-Gámez et al., 2008; Ortega-Obregón et al., 2009). To the northeast, an unnamed amphibolites-facies unit (consisting of garnet schist and quartzite with rare amphibolite dikes) is in tectonic contact with the Totoltepec pluton and the Tecomate Formation (Fig. 3). An uncon-formity, locally modifi ed by normal faulting, marks the northern contact between the pluton and overlying red beds of inferred Jurassic age (Malone et al., 2002).

The Totoltepec pluton is compositionally diverse, ranging from hornblendite and horn-blende gabbro through diorite to tonalite, trondhjemite, granodiorite, monzogranite, and quartz-rich granitoid. The petrography of these rocks is described in detail in Kirsch et al. (2012). Plagio clase-rich cumulates are found lo-cally in the central part of the pluton. The horn-blendite and hornblende gabbro occur only in three 0.2–0.6 km2 lens-shaped bodies along the northeastern margin of the pluton that coincide with relatively high-amplitude magnetic anom-alies (Servicio Geológico Mexicano, 2004a, 2004b). Although the exposed contacts between the main and marginal phases are faults, the mar-ginal bodies are cut by trondhjemitic dikes iden-tical to those in the main phase, implying that the faults have limited displacement. Only the trond-hjemite and diorite were dated, and they yielded ages of 287 ± 2 Ma and 289 ± 1 Ma, respectively (U-Pb thermal ionization mass spectrometry [TIMS] zircon ages; Yañez et al., 1991; Keppie et al., 2004a). Within the pluton, a locally devel-oped, subvertical fabric is defi ned by fl attened quartz and feldspar grains as well as by aligned hornblende. Al-in-hornblende thermobarometric data from the main phase (Kirsch et al., 2012) indicate that the pluton was emplaced into mid-crustal levels (~20 km).

The Tecomate Formation adjacent to the Totoltepec pluton consists of greenschist-facies metapelite, feldspar-bearing metapsammite with local intercalations of metaconglomer-ate, unfossiliferous marble horizons, and rare very fi ne-grained, green, tuffaceous layers. The metapsammites are made up of quartz, plagio-clase, and K-feldspar, phyllosilicates (white mica, biotite partially altered to chlorite), and opaque minerals, as well as secondary carbon-ate and epidote. Relict feldspar porphyroclasts in the metapsammites are angular to subrounded and display a wide range of grain sizes. Pebble- to cobble-sized clasts in the metaconglomerate are composed of trondhjemite, vein quartz, and metapsammite. Marble horizons, a distinctive feature of the Tecomate Formation, occur as intensely deformed, 1–2-m-thick tabular bodies that are occasionally boudinaged. Apart from

abundant quartz veins, thin granitoid dikes are localized to an area south of Santo Domingo Tonahuixtla. Though lithologically identical to the Tecomate Formation type area in the cen-tral Acatlán Complex (Ortega-Gutiérrez, 1978), reconnaissance geochronological analyses of Tecomate Formation metasedimentary rocks from the fi eld and the type area, respectively (Keppie et al., 2004b; Sánchez-Zavala et al., 2004), have yielded distinct detrital zircon age populations, suggesting contrasting sources for the two units.

U-Pb GEOCHRONOLOGY

Analytical Methods

Seven samples (see Table A1a1 and Fig. 3 for locations) were collected for U-Pb zircon dat-ing by LA-ICP-MS at the Laboratorio de Estu-dios Isotópicos (LEI), Centro de Geociencias, Universidad Nacional Autónoma de México, Mexico. Zircons were extracted using standard mineral separation techniques, as described by Solari et al. (2007). For details on the analytical procedure, see GSA Data Repository fi le 1 (see footnote 1).

In fi gures, tables, and results, 206Pb/238U ages are quoted for zircons younger than 1.0 Ga, whereas older grains are quoted using their 207Pb/206Pb ages (e.g., Gehrels et al., 2006). The latter ages become increasingly imprecise younger than 1.0 Ga due to small amounts of 207Pb. Zircon analyses with <10% normal and <5% reverse discordance are considered to be geologically meaningful (e.g., Harris et al., 2004; Dickinson and Gehrels, 2008; Gehrels, 2012) and are used to date the time of intrusion in igneous rocks or the maximum age of deposi-tion in metasedimentary rocks. The latter is con-sidered robust if it belongs to a cluster of three of more zircons with similar ages (e.g., Gehrels et al., 2006).

Results

Totoltepec PlutonA sample of hornblende gabbro from one

of the lens-shaped bodies at the northeastern margin of the Totoltepec pluton (TT-72) is com-posed of hornblende, plagioclase, epidote, and chlorite, as well as accessory zircon, apatite, and opaque minerals (Table A1a [see footnote 1]). Zircons from the marginal mafic phase are ≤370 µm in length and exhibit uniform igne-ous oscillatory- and sector-zoning patterns. The

analyses yielded 34 concordant 206Pb/238U ages (Table A1b [see footnote 1]; Figs. 4A and 4B) ranging from 299 ± 4 Ma to 311 ± 6 Ma. The TuffZirc (Ludwig and Mundil, 2002) 206Pb/238U age calculated from a coherent group of 25 zir-con analyses is 306 ± 2 Ma.

The quartz diorite sample from the central part of the Totoltepec pluton (TT-76B) consists of oligoclase, quartz, muscovite, and chlorite, with accessory apatite, zircon, and magnetite (Table A1a [see footnote 1]). Zircons separated from the dioritic phase are relatively small (≤200 µm in length) and possess a complex in-ternal texture with partially resorbed cores and zircon overgrowths, as revealed by cathodolu-minescence (CL) imaging. Zircon data (Table A1c [see footnote 1]; Figs. 4C and 4D) range from 278 ± 2 Ma to 310 ± 4 Ma, exhibiting a slightly right-skewed distribution. The TuffZirc algorithm yields a 206Pb/238U age of 289 ± 2 Ma for a coherent group of 22 analyses.

Interpretation. The TuffZirc age of 306 ± 2 Ma is interpreted as the time of intrusion of the Totoltepec hornblende gabbro. The other two marginal bodies (Fig. 3), which are spa-tially proximal to the one dated and have similar dimensions and petrologic characteristics, are inferred to be coeval. The TuffZirc age of 289 ± 2 Ma is interpreted as the crystallization age of the quartz diorite, corroborating earlier U-Pb dating by Yañez et al. (1991) and Keppie et al. (2004a), who reported concordant U-Pb zircon ages of 287 ± 2 Ma and 289 ± 1 Ma for the intru-sion of the Totoltepec pluton near Tonahuixtla, respectively.

Tecomate FormationThree metasedimentary samples from the

Tecomate Formation (TT-486A, TT-81, TT-82), one sample from metasedimentary rocks previ-ously mapped as the Cosoltepec Formation by Ortega-Gutiérrez (1978) (TT-612), and a sam-ple of a thin granitoid dike (TT-615) intruding these metasedimentary rocks were collected for geochronological analysis (Table A1a [see footnote 1]; Fig. 3). Zircons from the psammitic sample TT-486A (consisting of quartz, musco-vite, K-feldspar, and opaque minerals) from the Tecomate Formation in the northwestern part of the study area, in the hanging wall just above the fault contact with the Salada Unit (Fig. 3), yielded only Proterozoic ages (Figs. 5A–5B; Table A1d [see footnote 1]). Results show that 75% of the 99 concordant zircon analyses fall in the age range between ca. 1014 and 1368 Ma. The second-largest population consists of 17 zir-cons of early Mesoproterozoic age between ca. 1407 and 1629 Ma. The weighted mean age (in-corporating both internal analytical and external systematic error) of the youngest cluster over-

1GSA Data Repository item 2012220, analytical methods and tables of LA-ICP-MS geochronologi-cal and geochemical data, is available at http://www.geosociety.org/pubs/ft2012.htm or by request to [email protected].


Kirsch et al.


lapping in age at 2σ, calculated using the DZ Age Pick program developed at the LaserChron Center of the University of Arizona (www.geo.arizona.edu/alc), is 1005 ± 17 Ma (three grains).

A metapsammite assigned to the Tecomate Formation in the eastern part of the fi eld area (TT-81) is composed mainly of quartz, plagio-clase, muscovite, and opaque minerals. Zircons separated from this sample yielded 79 concor-dant analyses ranging from 273 ± 10 Ma to 1796 ± 34 Ma (Figs. 5C–5D; Table A1e [see footnote 1]). The most prominent population is defi ned by 50 grains between the ages of ca. 277 and ca. 332 Ma. Three smaller populations are defi ned by ages of ca. 400–570 Ma, ca. 780–845 Ma, and ca. 925–1240 Ma, respectively. The youngest cluster overlapping in age at 2σ

error yields a weighted mean value of 288 ± 3 Ma (eight grains).

A metapelite sample (TT-82) from the same area as TT-81 contains quartz, chlorite, and muscovite, as well as accessory miner-als. Ninety-seven concordant zircons from this sample display an age span of 282 ± 2 Ma to 2621 ± 42 Ma (Figs. 5E–5F; Table A1f [see footnote 1]), where a group of 16 grains with ages between ca. 293 and ca. 313 Ma defi nes the largest probability peak at ca. 303 Ma. Ages be-tween ca. 905 Ma and 1230 Ma defi ne another signifi cant age cluster, whereas age populations of ca. 470–570 Ma and ca. 655–720 Ma are rep-resented by 10 and 4 zircons, respectively. Two zircon analyses with ages between ca. 362 and ca. 385 Ma indicate a subordinate Devonian

source. The youngest cluster overlapping in age at 2σ yields a weighted mean age of 299 ± 3 Ma (six grains).

The metapsammite (TT-612) collected south of Santo Domingo Tonahuixtla from a unit originally mapped as the Cosoltepec Forma-tion is primarily made up of quartz, plagioclase, K-feldspar, and muscovite. Zircon analyses from this sample (Figs. 5G–5H; Table A1g [see footnote 1]) yielded 90 concordant ages rang-ing from 289 ± 2 Ma to 2708 ± 22 Ma. The most dominant zircon population is made up of ages between ca. 299 and ca. 326 Ma, yield-ing a probability peak at ca. 309 Ma. Another major age population is defi ned by ages of ca. 950–1340 Ma. A smaller population has ages between ca. 420 and ca. 605 Ma, and includes

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285 ± 2 Ma

278 ± 1 Ma

289 ± 2 Ma286 ± 2 Ma286 ± 2 Ma286 ± 2 Ma

100 µm

294 ± 2 Ma

100 µm100 µmm

301 ± 2 Ma301 ± 2 Ma301 ± 2 Ma

309 ± 2 Ma309 ± 2 Ma309 ± 2 Ma

306 ± 2 Ma306 ± 2 Ma306 ± 2 Ma

309 ± 2 Ma309 ± 2 Ma309 ± 2 Ma

2σ error ellipses

2σ error ellipses

290290290300300300310310310320

19.2 19.6 20.0 20.4 20.8 21.2 21.6 22.0

280280280290290290300300300310310310320

19 20 21 22 23

0.062

0.058

0.054

0.050

0.046

0.064

0.060

0.056

0.052

0.048

207 P

b/20

6 Pb

207 P

b/20

6 Pb

238U/206Pb

Fre

quen

cy

0

5

10

15

Age (Ma)270 280 290 300 310 320

TuffZirc 206Pb/238U age

(94.8% conf, n = 22)280

290

300

310

TuffZirc 206Pb/238U age

(95.7% conf, n = 25)290

300

310

320

306 –1/+2 Ma

289 +1/–2 Ma

Figure 4. Histograms (A, C) as well as Tera-Wasserburg diagrams (B, D) for U-Pb laser ablation–inductively coupled plasma–mass spec-trometry (LA-ICP-MS) zircon analyses of Totoltepec pluton rocks; mean 206Pb/238U age calculated by TuffZirc age algorithm of Ludwig and Mundil (2002). Black error bars are for the arguably syngenetic zircons, gray error bars for zircons likely to be xenocrystic, and white error bars indicate analyses ignored due to anomalously high errors. Also displayed are cathodoluminescence images of representative zircon crystals from dated rock samples.




TT-81 Metapsammiten = 79

90–105% conc.

C D309

288

400–570

780–845

925–1240

Fre

quen

cy

0

10

20

30

40


TT-82 Metapeliten = 97

90–105% conc.

E F303

282

342

470–570

655–720

905–1230Fre

quen

cy

0

10

20

30

40


TT-486A Metapsammiten = 99

90–105% conc.1150

1265

1430–1590Fre

quen

cy0

10

20

30

40


TT-612 Metapsammiten = 90

90–105% conc.

G

A

H

B

309

420–605 950–1340

Fre

quen

cy

0

10

20

30


400

600

800

1000

1200

1400

1600

1800

0 4 8 12 16 20 24 28

0.12

0.10

0.08

0.06

0.04

0.068

0.064

0.060

0.056

0.052

0.048

207 P

b/20

6 Pb

207 P

b/20

6 Pb

207 P

b/20

6 Pb

207 P

b/20

6 Pb

600

1000

1400

1800

0 4 8 12 16 20 24 28

0.20

0.16

0.12

0.08

0.04

0.13

0.11

0.10

0.09

0.08

0.07

0.06

0.20

0.16

0.12

0.08

0.04

600

1000

1400

1800

0 4 8 12 16 20 24 28

2σ error ellipses

2σ error ellipses

2σ error ellipses

2σ error ellipses

}}

}

} }}}

}

}

Age (Ma)0 500 1000 1500 2000 2500 238U/206Pb

0.062

0.060

0.058

0.056

0.054

0.052

0.050

0.064

0.060

0.056

0.052

0.084

0.080

0.076

0.072

800

1000 1000 1000

1200 1200 1200

1400 1400 1400

1600 1600 1600

1800 1800 1800

2 4 6 8 10

0

5

10

290 300 310 320 330 340

0

5

10

15

270 280 290 300 310 320 330 340

19.8 20.2 20.6 21.0 21.4 21.8 22.2

290 290 290 300 300 300 310 310 310 320 320 320

19.5 20.5 21.5 22.5

270 270 270 280 280 280 290 290 290 300 300 300 310 310 310 320 320 320 330 330 330

19 20 21

290 290 290 300 300 300 310 310 310 320 320 320 330 330 330 340 340 340

960 960 960

1000 1000 1000

1040 1040 1040

1080 1080 1080

5.4 5.6 5.8 6.4

I J

2σ error ellipses

207 P

b/20

6 Pb

0.20

0.16

0.12

0.08

0.04

TT-615 Granitoid diken = 57

90–105% conc.323

303

505–635 985–1310Fre

quen

cy

0

10

20


600

1000

1400

1800

0 4 8 12 16 20 24

} }

0.068

0.064

0.060

0.056

0.052

0

2

4

6

8

290 300 310 320 330 340

19 20 21

290 290 290 300 300 300 310 310 310 320 320 320 330 330 330 340 340 340

Weighted mean age = 288 ± 3 Ma





0

5

10

280 300 320 340 360

635

Figure 5. Relative age probabil-ity and histogram plots (A, C, E, G, I) as well as Tera-Wasserburg concordia diagrams (B, D, F, H, J) for U-Pb laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zir-con analyses of Chichihualtepec Tecomate Formation metasedi-mentary rocks and a granitoid dike. Black error ellipses in am-plifi ed concordia plot were used for weighted mean age calcula-tion of the youngest age group. Histograms indicate number of analyses within 100 m.y. inter-val; histograms of the youngest age group have a 10 m.y. bin width.


Kirsch et al.


a single Ordovician zircon of 469 ± 4 Ma. The weighted mean of the youngest age cluster over-lapping at 2σ error is 303 ± 3 Ma (fi ve grains).

A sample of a thin granitoid dike (TT-615) intruding the TT-612 Tecomate metapsammites is principally composed of quartz, plagioclase, and muscovite. In total, 57 concordant zircon analyses exhibit an age range from 290 ± 2 Ma to 2614 ± 22 Ma (Figs. 5I–5J; Table A1h [see footnote 1]). The two most prominent probabil-ity peaks are defi ned by a group of 16 grains with ages of ca. 294–316 Ma and by a group of 11 zircons with ages of ca. 318–335 Ma, followed by smaller age populations between ca. 505 and 635 Ma and between ca. 985 and 1310 Ma. The youngest zircons that overlap within 2σ error give a weighted mean age of 298 ± 3 Ma (fi ve grains).

Interpretation. The ca. 1005 Ma age for the youngest detrital zircons in sample TT-486A, located near the stratigraphic base of the Teco-mate Formation, suggests that this part of the unit was deposited at a time when late Paleo-zoic igneous sources were not exposed. Simi-larly, the type Tecomate Formation yielded no zircons younger than ca. 1.0 Ga (Sánchez-Zavala et al., 2004).

U-Pb ages of detrital zircon grains in the other samples are used to constrain the maximum depo-sitional age of the Tecomate Formation in the study area (e.g., Dickinson and Gehrels, 2009). Of the three metasedimentary samples from the Tecomate Formation south of the Totoltepec pluton, TT-81 yields the youngest weighted mean age (288 ± 3 Ma, Lower Permian), which is taken to represent the maximum depositional age in that locality. A 40Ar/39Ar whole-rock age of 263 ± 3 Ma (Morales-Gámez et al., 2009) from a Tecomate sericitic phyllite northwest of the Totoltepec pluton provides a younger age limit for the deposition of the Tecomate Forma-tion as well as the age of metamorphism.

In another locality within the study area, the depositional age of the Tecomate Formation is more tightly constrained to ca. 300 Ma. Sample TT-612 contains detrital zircons of Permian age, so it is assigned to the Tecomate Forma-tion rather than the Devonian–Carboniferous Cosoltepec Formation, with which it was origi-nally associated (Ortega-Gutiérrez, 1978). This conclusion is consistent with fi eld observations. The weighted mean of the youngest age cluster in sample TT-612 is 303 ± 3 Ma, which is simi-lar within error to the weighted mean age of the youngest zircon cluster from the granitoid dike (298 ± 3 Ma) at the same locality, suggesting that the host metapsammite in this locality was deposited at ca. 300 Ma and intruded very soon afterward. This depositional age is older than the maximum depositional age obtained from

sample TT-81. The ca. 298 Ma age falls between the 306 ± 2 Ma age of the marginal gabbro and the 289 ± 2 Ma of the central Totoltepec pluton, suggesting that the dike is either a late phase of the marginal gabbro or an early phase of the main Totoltepec intrusion.

Whereas deposition of the Tecomate Forma-tion south of the Totoltepec pluton occurred at ca. 300 Ma in one location and between ca. 288 and ca. 263 Ma in another, fossiliferous lime-stone horizons in the type Tecomate Formation in the central Acatlán Complex range from latest Pennsylvanian to early Middle Permian (Keppie et al., 2004b) and middle Pennsylvanian (Kazi-movian = 306–304 Ma) to Early Permian. Thus, the Tecomate Formation may be a composite unit, collectively spanning the middle Penn-sylvanian–Early Permian, but of different ages in different locations. Nevertheless, these data suggest that some of the Tecomate Formation in the type area as well as in the study area was deposited before intrusion and exhumation of the Totoltepec pluton. To avoid confusion with rocks in the type area, in this paper, the Teco-mate Formation south of the Totoltepec pluton is informally designated Chichihualtepec Teco-mate Formation (CTF; Fig. 3).

Provenance of the Chichihualtepec Teco-mate Formation. Taken together, there are 144 zircon grains in the age range between ca. 344 and ca. 273 Ma in analyzed samples from the Chichihualtepec Tecomate Formation. A com-pilation of these ages (Fig. 6), including sensi-tive high-resolution ion microprobe (SHRIMP) data of a sample from granite cobbles in Chichi-hualtepec Tecomate Formation metaconglomer-ates (Keppie et al., 2004b), shows that (1) the distribution and range of ages are more or less continuous, and (2) there is a signifi cant overlap between the detrital zircon age spectra and ages obtained from samples of the Totoltepec pluton. The measured Th/U ratios (Table A1 [see foot-note 1]), which are >0.01, support a magmatic origin of these zircons (e.g., Rubatto, 2002). However, the Totoltepec pluton cannot be a source of these zircons, as thermobarometric data suggest that the pluton was at a depth of ~20 km at ca. 289 Ma, and 40Ar/39Ar data indi-cate it did not cool through the muscovite clo-sure temperature until 283 ± 1 Ma (Kirsch et al., 2012). Assuming this uplift rate of ~1.4 mm/yr was maintained, the Totoltepec pluton was not exposed until ca. 275 Ma. Zircons of Carbon-iferous–Permian age in parts of the Chichihual-tepec Tecomate Formation that were deposited before ca. 275 Ma therefore cannot have been derived from the Totoltepec pluton, and are in-terpreted to have been derived from the regional arc edifi ce and from epizonal plutons exposed during the Pennsylvanian and Early Permian.

All of the U-Pb samples from the Chichi-hualtepec Tecomate Formation contain major detrital zircon age peaks between ca. 920 and 1250 Ma, which are within the range of ages documented from the adjacent Oaxacan Com-plex (Keppie et al., 2001, 2003; Solari et al., 2003). Whereas ca. 600 Ma, 1500–1600 Ma, 1750–1900 Ma, and 2100–2500 Ma zircons could have been derived from Amazonia, Oaxa-quia, and/or Laurentia, those with 800–950 Ma ages can come only from Amazonia (Keppie et al., 2008a) or Oaxaquia (e.g., the ca. 917 Ma Etla pluton; Ortega-Obregón et al., 2003). The source for the fi ve zircons with ages between 454 and 476 Ma may be the rift-related gran-itoid plutons within the Acatlán Complex, which have yielded ages between 440 and 480 Ma (Keppie et al., 2008b). Five detrital zircons in the samples from the Chichihualtepec Tecomate Formation are Devonian–Mississippian, span-ning ages of 357–402 Ma. A postulated arc on the western margin of the Mixteca terrane, most of which was subsequently removed by subduc-tion erosion (Keppie et al., 2008a, 2010), may have been the source for these zircons.

GEOCHEMISTRY

Analytical Methods

In order to determine the tectonic setting for the igneous and metasedimentary rocks in the Totoltepec area, 34 samples from the Totolte-pec pluton and 41 metasedimentary rocks of the Tecomate Formation were analyzed for major and selected trace elements (Fig. 3) by X-ray fl uorescence at the Regional Geochemi-cal Centre , St. Mary’s University, Canada (for details of analytical methods, see Dostal et al., 1994). Of these, 15 representative samples from the Totoltepec pluton and 7 from the Teco-mate Formation were selected for analysis of addi tional trace elements (rare-earth elements [REEs], Y, Zr, Nb, Ba, Hf, Ta, and Th) by ICP-MS according to methods described in Jenner et al. (1990). Sm-Nd isotopic compositions of these 15 samples were determined in order to characterize the source regions and tectonic his-tory of the respective geological units according to the method described in Kerr et al. (1995). For details on the analytical procedures, see GSA Data Repository fi le 1 (see footnote 1).

Results

Results of the geochemical analyses are pre-sented in Table A2 (see footnote 1). The samples are affected to varying degrees by secondary processes, including low-grade metamorphism and deuteric alteration. These secondary proc-esses have modifi ed their primary chemical




composition, resulting in a scatter on diagrams featuring alkali and alkaline earth elements and elevated loss on ignition (LOI) values. Hence, inferences about the petrogenesis of the rocks are largely based on high fi eld strength elements (HFSEs) and rare earth elements (REEs), which are considered to be relatively “immobile” dur-ing alteration processes (e.g., Winchester and Floyd, 1977), and should refl ect original magma chemistry for the igneous rocks as well as prov-enance compositions of the sedimentary rocks (Taylor and McLennan, 1985).

Totoltepec PlutonGeochronological data indicate that the

Totoltepec pluton was formed in two distinct intrusive events. Hence, geochemical data for rocks from the ca. 306 Ma marginal bodies and for rocks from the ca. 289 Ma main body of the pluton are presented separately.

Older (ca. 306 Ma) Totoltepec rocks. Samples from the older marginal bodies of the Totoltepec pluton range from hornblende gabbro to horn-blendite with SiO

2 (LOI-free) between 41.9 and

51.1 wt%. These mafi c to ultramafi c rocks have relatively wide ranges in TiO

2 (0.19–0.99 wt%),

Fe2O

3 (2.89–12.6 wt%), MgO (2.45–11.3 wt%),

Cr (38–313 ppm), V (66–434 ppm), Co (11–

47 ppm), and Ni (21–163 ppm) (Fig. 7; Table A2a [see footnote 1]). The samples have low Nb/Y (0.03–0.15) and Zr/Ti (0.002–0.009), which is typical of subalkaline basaltic rocks (Fig. 8). The rocks are characterized by low Th/Yb and Ta/Yb and highly variable Th/Hf ratios. On discrimina-tion diagrams using these parameters, the data straddle the boundary between calc-alkaline and island-arc tholeiitic fi elds (Figs. 9A and 9B).

The hornblende gabbros exhibit relatively fl at chondrite-normalized REE patterns (Fig. 10A; average [La/Yb]n = 1.8) with ΣREE of 3–13 times chondrite, and positive Eu anomalies (up to Eu/Eu* = 2.6) that decrease with increasing SiO

2.

The presence of pronounced positive Eu anoma-lies in some gabbro samples suggests plagio-clase accumulation. The hornblendite sample is characterized by a concave-upward REE pattern ([La/Sm]n = 0.4; [Gd/Yb]n = 1.7), indicative of the dominance of cumulus amphibole.

The mid-ocean-ridge basalt (MORB)–nor-malized multi-element plot of the ca. 306 Ma marginal rocks (Fig. 10B) shows enrichment in large ion lithophile elements (LILEs; Cs, Rb, Ba, U, K, Pb, and Sr), moderate depletion in the less incompatible elements (Zr, Hf, Ti, middle to heavy REEs), and strong depletion in the HFSEs Nb and Ta. This signature refl ects

derivation from a mantle wedge affected by slab fl uxing processes, i.e., patterns that are typical of subduction-related magmas (e.g., Saunders et al., 1988; McCulloch and Gamble, 1991).

Sm-Nd isotope analyses on the older marginal Totoltepec rocks yield initial εNd ranging from +1.3 to +3.3 and 147Sm/144Nd ratios from 0.15 to 0.24 with a TDM model age (147Sm/144Nd < 0.165; Stern, 2002) of 0.84 Ga (Table 1; Fig. 11). The 306 Ma sample (TT-72) with the lowest εNd(i) plots well above the mantle depletion-enrich-ment array in Figure 9A and toward the Th apex in Figure 9B, indicating contamination by a crustal or a subduction component. Accord-ingly, on the εNd(t) versus 147Sm/144Nd diagram (Fig. 11B), this sample lies on a curve repre-senting assimilation and fractional crystalliza-tion (DePaolo, 1981) between one of the more juvenile 306 Ma samples and the average com-position of the Oaxacan Complex (Ruiz et al., 1988). By contrast, the Sm-Nd isotopic signa-ture of the other hornblende gabbro samples as well as the hornblendite is similar to Ordovician mafi c rocks within the Mixteca terrane (Murphy et al., 2006; Ortega-Obregón et al., 2010), which are interpreted to have been derived from a ca. 1.0 Ga subcontinental lithospheric mantle. The 306 Ma gabbro and hornblendite may hence

TT-81Metapsammite

TT-82Metapelite

TEC-10 Granite cobble

metaconglomerate(Keppie et al., 2004b)

270

280

290

300

310

320

Age

(M

a)

330

340

350

Ea

rly

Pe

rmia

nP

en

nsy

lva

nia

nM

issi

ssip

pia

n

CA

RB

ON

IFE

RO

US

PE

RM

IAN

Totoltepec plutonca. 289 Ma Qz diorite

Totoltepec plutonca. 306 Ma Hbl gabbro

TT-612 Metapsammite

TT-615 Granitoid dike

Frequency0 25 50

Rel. prob

n = 162

Figure 6. A 2σ error bar plot showing concordant 206Pb/238U ages of detrital zircons from the Chichihualtepec Tecomate Formation metased-imentary rocks. Data also include inherited zircons extracted from a granitoid dike intruding Chichihualtepec Tecomate Formation metapsammites as well as U-Pb sensitive high-resolution ion microprobe (SHRIMP) analyses of zircons separated from Chichihualtepec Tecomate Formation metaconglomerate granitoid cobbles (Keppie et al., 2004b). Diagonally hatched regions and histograms represent U-Pb age data from Totoltepec pluton rocks. Gray shaded histogram on the right-hand side shows the age distribution of all detrital zircon data featured in this diagram. Qz—quartz; Hbl—hornblende.


Kirsch et al.


be derived from the same subcontinental litho-spheric mantle as the Ordovician mafi c rocks. Mafi c rocks with similar isotopic compositions also occur along other parts of the Gondwanan margin (Avalonia: e.g., Murphy and Dostal , 2007; Iberia-western Europe: e.g., Murphy et al., 2008; Keppie et al., 2011), suggesting the

subcontinental lithospheric mantle that underlay the area in the late Paleozoic may have been re-gionally widespread.

Main-phase (ca. 289 Ma) Totoltepec rocks. Totoltepec pluton samples of ca. 289 Ma age consist of hornblende diorite, tonalite, quartz diorite, trondhjemite, quartz-rich granitoid, and

plagioclase-rich cumulates from the main body of the pluton. Trondhjemite dikes that intrude the ultramafi c and mafi c marginal bodies of the pluton are included in the ca. 289 Ma Totoltepec rocks based on matching petrographic and geo-chemical characteristics. The samples display a wide range in chemistry, with an SiO

2 content

15

20

25

30

0

0.2

0.4

0.6

0.8

1.0

0

5

10

15

Low K

Medium K

High K

0.1

1

10

100

SiO2 (wt%)

45 50 55 60 65 70 75

1

10

SiO2 (wt%)

45 50 55 60 65 70 75

TiO2 (wt%)

CaO (wt%)

Zr (ppm)

Al2O3 (wt%)

K2O (wt%)

(La/Yb)n

Quartz-rich granitoidTrondhjemitePlag-rich cumulateTonalite

289

Ma

306

Ma

Quartz dioriteHornblende diorite

Hornblende gabbroHornblendite

Cozahuico granite (270 Ma)

Chiapas Massif (272–251 Ma)

La Carbonera (275 Ma)

Tuzancoa (290–260 Ma)

Cuchumatanes (318–313 Ma)

A B

C D

E F

Figure 7. Variation diagrams for selected major elements, high fi eld strength trace elements, and ratios of Totoltepec pluton rocks and cor-relative Carboniferous–Permian igneous suites (labeled in part F). Division lines in K2O plot are from Le Maitre et al. (2002). Included in the comparison (from north to south) are geochemical data from (1) andesitic to basaltic lava fl ows from the 290–260 Ma Tuzancoa Forma-tion in the Sierra Madre terrane (Rosales-Lagarde et al., 2005); (2) the 270 ± 3 Ma Cozahuico granite (this paper), which intrudes the N-S dextral transpressive Caltepec fault zone (CFZ); (3) the 275 ± 4 Ma La Carbonera stock, which intrudes the northern Oaxacan Complex (Solari et al., 2001; this paper); (4) ca. 272–251 Ma orthogneisses of the Chiapas Massif (Maya block; Weber et al., 2005); and (5) ca. 318–313 Ma plutons in the Altos Cuchumatanes Range, Guatemala (Maya block; Solari et al., 2010; Solari, 2012, personal commun.).




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siti

onal

; A

LK

—al

kalin

e; C

A—

calc

-al

kalin

e; S

HO

—sh

osho

niti

c. C

ompo

siti

ons o

f nor

mal

mid

-oce

an-r

idge

bas

alt (

N-M

OR

B),

enri

ched

(E) M

OR

B, a

nd o

cean

-isl

and

basa

lt (O

IB) a

re a

fter

Sun

and

McD

onou

gh (1

989)

; (B

) Th-

Hf/

3-Ta

dis

crim

inat

ion

diag

ram

aft

er W

ood

et a

l. (1

979)

. MM

—m

antl

e so

urce

; UC

—up

per

crus

t; L

C—

low

er c

rust

; SZ

—su

bduc

tion

com

pone

nt. (

C) Y

b ve

rsus

Ta

diag

ram

fo

r fe

lsic

roc

ks (a

fter

Pea

rce

et a

l., 1

984)

. VA

G—

volc

anic

arc

gra

nite

s; s

yn-C

OL

G—

sync

ollis

ion

gran

ites

; WP

G—

wit

hin-

plat

e gr

anit

es; O

RG

—oc

ean-

ridg

e gr

anit

es.


Kirsch et al.


(LOI-free) spanning 51.6–77.7 wt% and Mg# (100 × Mg/[Mg + Fe] molar) of 21–63. With increasing silica, the samples show a decrease in TiO

2, Al

2O

3, CaO (Fig. 7), and Ni, suggest-

ing that these rocks may represent a comag-matic series with fractionating plagioclase and hornblende. When plotted against SiO

2, P

2O

5,

Zr, Nb, and Ce display convex-upward patterns,

indicating fractionation of apatite, zircon, and other accessory phases. The 289 Ma Totoltepec rocks are characterized by low abundances of Cr (≤27 ppm), V (≤288 ppm), Co (≤29 ppm), and Ni (≤19 ppm). On the Zr/TiO

2-SiO

2 diagram

(Fig. 8A; Winchester and Floyd, 1977; Pearce, 1996), the samples are classifi ed as mafi c to felsic in composition, and their low Zr/Ti ratios

are typical of subalkaline mafi c to intermediate rocks (Fig. 8B). Their subalkaline character is also indicated by their low Nb/Y (0.02–0.49) values as well as their position above the mantle array in the Ta/Yb versus Th/Yb plot (Fig. 9A). A volcanic arc origin is indicated on the Th-Hf-Ta and Yb versus Ta diagrams (Figs. 9B and 9C), and by Zr/Nb (~30), Ce/Yb (~12), and

Sample / chondrite1

10

100

Quartz-rich granitoidTrondhjemitePlag-rich cumulateTonaliteQuartz dioriteHornblende diorite


289

Ma

306

Ma

Cozahuico granite 270 Ma

Chiapas Massif 272–251 Ma

La Carbonera 275 Ma

Tuzancoa 290–260 Ma

Cuchumatanes 318–313 MaSam

ple

/ cho

ndrit

e

1

10

100

Sample / chondrite1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Sam

ple

/ NM

OR

B

0.001

0.01

0.1

1

10

100

1000

Sam

ple

/ NM

OR

B

0.001

0.01

0.1

1

10

100

1000

Sam

ple

/ NM

OR

B

0.001

0.01

0.1

1

10

100

1000

Cs Rb Ba Th U Nb Ta K La Ce Pb Pr Sr P Nd Zr Hf Sm Eu Ti Dy Y Yb Lu

A B

D

F

C

E

Figure 10. Chondrite-normalized rare earth element (REE) patterns (A, C, E) and normal mid-ocean-ridge basalt (N-MORB)–normalized multi-element plots (B, D, F) for Totoltepec pluton rocks and comparative igneous suites (see caption of Fig. 7 for references). Normalizing values are from Sun and McDonough (1989).




La/Nb (~3) ratios, which are typical of modern calc-alkaline suites (Gill, 1981; Pearce, 1982; Cabanis and Lecolle, 1989). However, some of the samples exhibit a more primitive tholeiitic character due to lower Th/Yb (Fig. 9A) and higher Hf/Th (Fig. 9B) ratios.

The chondrite-normalized REE patterns of the ca. 289 Ma diorite and tonalite samples (Fig. 10C) are characterized by fl at light (L) REEs (aver age [La/Sm]n = 1.5), fl at to moderately fractionated heavy (H) REEs ([Gd/Yb]n = 1.1–3.3), small neg-ative to small positive Eu anomalies (Eu/Eu* = 0.7–1.4), and ΣREE abundances of 12–21 times chondrite. Chondrite-normalized REE patterns of the trondhjemites, and samples of quartz-rich granitoid and plagioclase-rich cumu late (Fig. 10E) are typifi ed by an LREE enrichment (aver-age [La/Sm]n = 2.7; average [La/Yb]n = 4.6), fl at HREE patterns (average [Gd/Yb]n = 1.2), nega-tive to positive Eu anomalies (Eu/Eu* = 0.5–2.9), and low ΣREE. The general trend for these sam-ples is a decrease in ΣREE with increasing SiO

2,

which may be an effect of accessory phase frac-tionation (Miller and Mittlefehldt, 1982).

Multi-element patterns for diorite and tonalite normalized to N-MORB (Fig. 10D) show en-richment in LILEs (Cs, Ba, K, Pb, and Sr) and moderate depletion in the HFSEs Ta and Ti. Abundances of Nb, Zr, and Hf as well as the middle REEs are similar to N-MORB. The heavy REEs are depleted in all but one tonalite sample, which exhibits HREE values identical to N-MORB. Trace-element profi les (Fig. 10F) for the Totoltepec trondhjemites, and samples of quartz-rich granitoid and plagioclase-rich cumulate are enriched in strongly incom pati-ble elements (Cs, Rb, Ba, Th, U), moderately depleted in the less incompatible elements (middle to heavy REEs, Ti, Y), and show strong Nb and Ta negative anomalies. These patterns are a characteristic feature of arc magmas (e.g., Pearce and Peate, 1995).

The Sm-Nd isotopic data for the ca. 289 Ma Totoltepec rocks yield initial εNd values between

–0.8 and +2.6 and 147Sm/144Nd ratios from 0.12 to 0.20 (Table 1; Fig. 11). Rocks with 147Sm/144Nd < 0.165 yield TDM ages of 0.93–1.16 Ga. Although considerably less radiogenic than the contempo-rary depleted mantle, one of the ca. 289 Ma to-nalite samples (εNd[i] = 2.6) and the hornblende diorite (εNd[i] = 2.5) have similar isotopic com-positions to those of the ca. 306 Ma mafi c rocks, suggesting derivation from the same subconti-nental lithospheric mantle. The other ca. 289 Ma Totoltepec rocks exhibit lower εNd(i) and higher TDM values. These rocks could not have origi-nated by simple differentiation of a Totoltepec pluton mafi c parent, because simple fractional crystallization should not affect the 143Nd/144Nd ratio. Their position along assimilation and frac-tional crystallization (AFC) trajectories in the εNd(t) versus 147Sm/144Nd diagram (Fig. 11B) suggests that their isotopic signature may be an effect of mixing between a basaltic magma (P) and crustal melts (C) derived from Oaxacan Complex basement.

TABLE 1. Sm-Nd ISOTOPIC DATA FOR SAMPLES FROM THE TOTOLTEPEC AREA, ACATLÁN COMPLEX, MEXICO

Sample Rock typeNd

(ppm)Sm

(ppm) Sm/Nd 147Sm/144Nd 143Nd/144Nd 2σT(i)(Ma) εNd(0)* εNd(i)

TDM†

(Ga)Totoltepec plutonCa. 306 Ma marginal rocksTT-24 Hornblende gabbro 1.77 0.60 0.340 0.2054 0.512811 10 306 3.4 3.0 –TT-26A Hornblende gabbro 1.58 0.40 0.256 0.1548 0.512722 20 306 1.6 3.3 0.84TT-26B Hornblende gabbro 2.07 0.71 0.344 0.2077 0.512813 10 306 3.4 3.0 –TT-28 Hornblendite 4.44 1.74 0.391 0.2365 0.512858 6 306 4.3 2.7 –TT-72 Hornblende gabbro 6.45 1.86 0.288 0.1743 0.512659 7 306 0.4 1.3 (1.47)

Ca. 289 Ma rocksTT-12§ Quartz-rich granitoid 1.06 0.04 0.035 0.0213 0.512523 8 289 -2.2 4.2 (0.42)

90.15.11.09825246215.08751.0162.089.185.7etilanoTA31-TTTT-13B Tonalite 10.23 3.08 0.301 0.1821 0.512677 7 289 0.8 1.3 (1.74)TT-14 Hornblende diorite 10.05 2.60 0.259 0.1562 0.512690 7 289 1.0 2.5 0.94TT-16 Trondhjemite 2.03 0.47 0.233 0.1405 0.512561 7 289 –1.5 0.6 1.00TT-22 Trondhjemite 7.51 1.64 0.219 0.1322 0.512528 6 289 –2.1 0.2 0.97TT-27 Trondhjemite 1.23 0.40 0.327 0.1973 0.512747 8 289 2.1 2.1 (2.89)TT-52 Plagioclase-rich cumulate 1.90 0.44 0.234 0.1416 0.512492 7 289 –2.8 –0.8 1.16TT-74 Trondhjemite 3.07 0.61 0.199 0.1202 0.512458 4 289 –3.5 –0.7 0.96

39.06.20.19827196215.06551.0752.073.222.9etilanoT87-TT

Chichihualtepec Tecomate Formation (CTF)TT-5A Metapsammite 13.62 3.13 0.230 0.139 0.512520 7 288 –2.3 –0.2 1.07TT-6 Metapelite 22.03 5.14 0.233 0.1411 0.512396 8 288 –4.7 –2.7 1.35TT-7B Metapsammite 23.25 4.96 0.213 0.129 0.512299 6 288 –6.6 –4.1 1.33TT-36 Metapsammite 16.81 4.06 0.241 0.1459 0.512558 7 288 –1.6 0.3 1.09TT-39 Metapsammite 26.36 4.80 0.182 0.0988 0.512168 4 288 –9.2 –5.6 1.16TT-61A Metapsammite 39.88 7.74 0.194 0.1173 0.512308 5 288 –6.4 –3.5 1.16TT-67 Meta-arkose 16.91 3.51 0.208 0.1255 0.512319 8 288 –6.2 –3.6 1.25

Cozahuico granite91.17.3–3.6–0727313215.06021.0002.020.180.5etinarG065-TT73.10.3–0.5–0727483215.01141.0332.046.110.7etinarG365-TT

TT-564 Granite 10.82 1.79 0.166 0.1002 0.512287 7 270 –6.8 –3.5 1.02

La Carbonera Stock31.16.3–5.6–5727303215.09311.0881.043.317.71etiroiDA565-TT02.14.3–9.5–5727633215.03421.0602.088.427.32etiroiDB565-TT

TT-568 Gabbro 71.64 18.70 0.261 0.1578 0.512338 7 275 –5.9 –4.5 1.91TT-569 Granodiorite 22.29 3.782 0.170 0.1026 0.512311 6 275 –6.4 –3.1 1.00

Note: Analyses were performed at the Atlantic Universities Regional Isotopic Facility, Memorial University of Newfoundland. For details on analytical procedures, see GSA Data Repository File 1 (see text footnote 1).

*εNd values are relative to 143Nd/144Nd = 0.512638 and 147Sm/144Nd = 0.196593 for present-day chondrite uniform reservoir (CHUR; Jacobsen and Wasserburg, 1980) and λ147Sm = 6.54 × 10–12/yr (Steiger and Jäger, 1977).

†Depleted mantle model ages (TDM) were calculated using the depleted mantle model of DePaolo (1981). Values in parentheses denote model ages that may be unreliable due to high 147Sm/144Nd (>0.165; Stern, 2002).

§Sample has anomalously low Sm and Nd concentrations and is thus excluded from further consideration.


Kirsch et al.


Comparative GeochemistryIn order to evaluate their regional signifi-

cance, we compare the Totoltepec rocks to other Permian to Carboniferous igneous suites along the North American Cordillera for which ages have been determined by U-Pb geochronology

(Figs. 2 and 7). Some of these suites form part of the putative late Paleozoic continental magmatic arc extending along the length of Mexico (e.g., Torres et al., 1999; Centeno-García, 2005).

Harker diagrams display considerable over-lap between the Totoltepec pluton and the com-

parative suites for major elements TiO2, Al

2O

3,

Fe2O

3, and CaO (Fig. 7), but the Cozahuico gran-

ite, La Carbonera stock, and igneous rocks from the Chiapas Massif and the Altos Cuchumatanes exhibit consistently higher SiO

2 and K

2O. The

more felsic and more alkalic character of these

Figure 11. (A) εNd(t) versus time plot comparing Sm-Nd isotopic data of the Totoltepec pluton (vertically hatched) and the Chichihualtepec Tecomate Formation metasedimentary rocks (diagonally hatched) with metasedimentary rocks from the Tecomate Formation type area (Yañez et al., 1991), rocks from the Oaxacan Complex (Ruiz et al., 1988), and Ordo-vician amphibolites from the Asis area (Murphy et al., 2006). Modern depleted mantle com-position is from DePaolo (1988). (B) 147Sm/144Nd versus εNd(t) diagram for Totoltepec pluton rocks as a means to evaluate crustal contamination. Fields cor-respond to Sm-Nd data from the Cozahuico granite (this paper; Elías-Herrera et al., 2005; Torres et al., 1999), the La Car-bonera stock (this paper), the Altos Cuchumatanes granitoids (Solari, 2012, personal com-mun.), the Tuzancoa Formation volcanic rocks (Rosales-Lagarde et al., 2005), and Ordovician amphibolites from the Asis lithodeme (Murphy et al., 2006) and the Olinalá area (Ortega-Obregón et al., 2010). For comparison, εNd(t) data for all samples are shown at t = 289 Ma. The black curves show trends for assimilation and fractional crystallization (AFC; DePaolo, 1981) in which crust (C—aver-age composition of the Oaxacan Complex calculated from Ruiz et al., 1988) is assimilated by a basaltic parent magma (P—average composition of four most juvenile 306 Ma marginal ultra mafi c to mafi c rocks of the Totoltepec pluton). Values for r (rate of assimilation relative to fractional crystallization) are indicated adjacent to AFC lines. For r ≥ 1, curves extend to values of F (fraction of remaining liquid) = 5; for r < 1, curves end at F = 0.1. Partition coeffi cients are from Arth (1976). Composition of depleted mantle is from DePaolo (1988). Gray arrows indicate trends for pure fractional crystallization of olivine (Ol), pyroxene (Px), hornblende (Hbl), plagioclase (Plag), apatite (Ap), zircon (Zrc), and K-feldspar (K-fsp).

r = 0.25

r = 0.75

r = 2

r = 10

Ord. amphibolites Asis (Murphy et al., 2006)

Ord. amphibolites Olinalá (Ortega-Obregon et al., 2010)

Totoltepec pluton trondhjemite(Martiny-Kramer, 2008)

Depletedmantle

OaxacanComplex

εN

d(t =

289

Ma)

-8

-6

-4

-2

0

2

4

6

8

147Sm/144Nd

0.10 0.12 0.14 0.16 0.18 0.20 0.22 0.24

PlagOl, Px, Hbl

C

P

Ol, Px, Ap, Zrc K-fsp, Plag

Cozahuico granite 270 Ma

La Carbonera 275 Ma

Cuchumatanes 318–313 Ma

A

B

Depletedmantle

ε Nd(

t)

10

5

0

5

t (Ga)

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Totoltepec pluton

Chichihualtepec Tec. Fm.

Asis amphibolites

Tecomate Fm. type area

Oaxacan Complex

MetapeliteMetapsammiteMeta-arkose

TrondhjemitePlag-rich cumulateTonalite

289

Ma

306

Ma

Quartz dioriteHornblende diorite





suites is also apparent in the rock classifi cation diagrams (Fig. 8), where they plot mainly in the fi elds of (trachy-)andesite, rhyolite, and trachyte. Lavas from the Tuzancoa Formation overlap the composition of Totoltepec pluton tonalite and quartz diorite. Tectonic discrimination diagrams (Fig. 9) classify the majority of the samples from the comparative igneous suites as calc-alkaline arc rocks, but they show higher Ta and Yb abun-dances as well as higher Ta/Yb and Th/Yb ratios than rocks of the Totoltepec pluton. Chondrite-normalized REE patterns of comparative igne-ous suites are more fractionated (higher[La/Yb]n ratios; Figs. 7F, 10A, 10C, and 10E), and they display higher total REE abundances than most samples of the Totoltepec pluton. The MORB-normalized spidergrams of comparative igneous suites (Figs. 10B, 10D, and 10F) are similar to those of rocks from the Totoltepec pluton, showing a jagged pattern with positive LILE enrichment and negative HFSE anomalies, typi-cal of arc-derived rocks. On average, however, the Totoltepec rocks have lower abundances of Nb, Ta, Zr, and LREE, and are less enriched in LILEs (Rb, Th, K) than comparative Carbon-iferous–Permian igneous rocks. The Sm-Nd isotopic signature of the Coza huico, La Carbo-nera, and the Altos Cuchumatanes rocks is less radiogenic than that of the Totoltepec pluton, displaying initial εNd values between –4.9 and –3.0, TDM model ages from 1.1 to 2.2 Ga, and 147Sm/144Nd ratios between 0.10 and 0.16 (Fig. 11; this paper : Table 1; Torres et al., 1999; Elías-Herrera et al., 2005; Solari, 2012, personal com-mun.). The Tuzancoa Formation volcanic rocks

exhibit an εNd(t) value of –1.3 (t = 275) and a TDM model age of 1.4 Ga (recalculated from Rosales-Lagarde et al., 2005). These values, which are less radiogenic than Totoltepec pluton rocks with similar SiO

2 content, suggest deriva-

tion by melting of older continental crust. This conclusion is consistent with an abundance of inherited zircons and/or crustal xenoliths docu-mented in these rocks (Elías-Herrera et al., 2005; Solari et al., 2001, 2010). Other plutonic rocks, for which their late Paleozoic ages are based on K-Ar or Rb-Sr dating (not shown), as well as sedimentary rocks of Permian–Carboniferous age exhibit εNd(i) values similar to the Coza-huico and La Carbonera stocks (Torres et al., 1999; Schaaf et al., 2002; Yañez et al., 1991) and therefore are in broad agreement with this interpretation.

Chichihualtepec Tecomate FormationSamples from the Chichihualtepec Tecomate

Formation collected for geochemistry include 16 metapsammites, 11 metapelites, 12 meta-arkoses , and 2 metaconglomerates. The major-element abundances of these metasedimentary rocks lie in the range of typical shales, sand-stones, and graywackes, with their SiO

2 content

ranging from 56.4 to 76.9 wt% and Al2O

3 values

from 11 to 21 wt% (LOI-free basis). SiO2 dis-

plays negative correlations with Al2O

3 (correla-

tion coeffi cient r = –0.84), Fe2O

3 (r = –0.92), Co

(r = –0.84), and V (r = –0.80), respectively, which refl ect the different proportions of clay/mud-rich and quartz-rich components, as documented in other sedimentary sequences (e.g., Bhatia, 1983).

The range of Al2O

3/TiO

2, Cr/Th, Th/Co,

Cr/V, and V/Ni ratios in the Chichihualtepec Tecomate Formation rocks suggests that the majority of samples are derived from felsic sources (Taylor and McLennan, 1985; Cullers, 1994; Girty et al., 1996), which is consistent with the low average MgO, Fe

2O

3, Cr, Ni, and

Co abundances. Incompatible elements such as Zr, Nb, Hf, Ta, Y, Th, and U have higher abun-dances in the Chichihualtepec Tecomate For-mation rocks than they display in sedimentary suites derived from mafi c sources (Feng and Kerrich, 1990). Similarly, Hf and La/Th charac-teristics of the Chichihualtepec Tecomate For-mation rocks (Floyd and Leveridge, 1987; Fig. 12A) indicate an acid arc to mixed felsic-basic source with a minor infl uence of older sedimen-tary components.

Chondrite-normalized REE patterns of the Chichihualtepec Tecomate Formation (Fig. 13A) are characterized by a moderate en-richment in LREE ([La/Yb]n = 3.0–7.1), fl at HREE ([Gd/Yb]n = 1.0–1.5), and negative Eu anomalies (Eu/Eu* = 0.62–0.82). These fea-tures suggest that the source of the clastic rocks was fractionated with respect to plagioclase (Slack and Stevens, 1994). One metapsammite sample exhibits a greater REE fractionation (LREE/HREE = 16.9, [La/Yb]n = 25.0) and a slightly steeper HREE slope ([Gd/Yb]n = 2.5). Total REE abundances for all samples range be-tween 20 and 150 times chondrite.

The Sm-Nd isotopic compositions for Chi-chihualtepec Tecomate Formation samples are highly variable (Fig. 11A), with εNd(t) values

BA MetapeliteMetapsammiteMeta-arkoseMetaconglomerateUpper continental crustNorth American Shale CompositePost Archean Australian Shale

Tholeiitic oceanicarc source

Andesiticarc source

Mixed felsic-basic sourceMixed felsic-basic sourceMixed felsic-basic source

Acid arc source

OIA – Oceanic island arcCA – Continental island arcACM – Active continental marginPM – Passive margin

Increasing old sediment component

Passivemarginsource

La/T

h

0

2

4

6

8

10

12

14

Hf (ppm)

0 2 4 6 8 10 12 14

PM

ACM

CA

OIA

Al 2O

3 / S

iO2 (

wt%

)

0

0.05

0.10

0.15

0.20

0.25

0.30

0.35

(Fe2O3+MgO) (wt%)

0 2 4 6 8 10 12 14 16

Figure 12. Discrimination diagrams for the metasedimentary rocks of the Chichihualtepec Tecomate Formation. (A) Hf versus La/Th diagram after Floyd and Leveridge (1987); (B) (Fe2O3 + MgO) versus (Al2O3/SiO2) diagram after Bhatia (1983). Post-Archean Australian Shale, upper continental crust (Taylor and McLennan, 1985), and North American Shale Composite (Gromet et al., 1984) are shown for comparison.


Kirsch et al.


ranging from –5.6 to +0.3 (t = 288 Ma) and de-pleted mantle model ages (TDM) between 1.07 and 1.35 Ga. These data represent the weighted average of Sm-Nd isotopic compositions for all the detrital contributions from the source area (Arndt and Goldstein, 1987; Murphy and Nance, 2002). The εNd(t) evolution lines of the Chichihualtepec Tecomate Formation rocks lie between, and partially intersect, the Sm-Nd envelopes of both the Oaxacan Complex rocks and the Totoltepec pluton, suggesting compo-nents of both these sources in the clastic rocks. This interpretation is consistent with detrital zircon geochronological data, which indicate that the Oaxacan Complex and the regional

Carboniferous–Permian arc are the two main contributing source areas. In contrast to the data presented herein, the Tecomate Formation in the type area (Yañez et al., 1991) lacks a contribu-tion from the regional Carboniferous–Permian arc, as their εNd(t) values closely correspond with the Sm-Nd isotopic composition of the Oaxacan Complex (Fig. 11A). This inference is supported by U-Pb geochronological data of metasedimentary rocks from the Tecomate type area (Sánchez-Zavala et al., 2004), which yielded detrital zircon populations of Ordovi-cian and Mesoproterozoic age.

Upper continental crust–normalized trace-element patterns of the Chichihualtepec

Teco mate Formation (Fig. 13B) rocks are char-acterized by positive Cs, Ba, and U anomalies for some samples and a strong depletion in HFSEs, particularly Nb and Ta. This signature suggests that the Chichihualtepec Tecomate Formation was deposited in a sedimentary basin that formed in an arc environment. An arc-re-lated provenance is also indicated on the Hf ver-sus La/Th plot (Floyd and Leveridge, 1987; Fig. 12A) and the (Fe

2O

3 + MgO) versus Al

2O

3/SiO

2

ratio diagram (Bhatia, 1983; Fig. 12B). A lim-ited range in Ti/Zr ratios and the petrographic observations, such as the high modal abundance of feldspar, a wide range of grain sizes, and the angularity of relict porphyro clasts, point to a compositionally immature, poorly sorted sedi-ment that was only transported over a short dis-tance (Garcia et al., 1994).

SUMMARY AND DISCUSSION

Our results indicate that the late Paleozoic Totoltepec pluton and the metasedimentary Chichihualtepec Tecomate Formation postdate collisional orogenesis and developed at differ-ent crustal levels along the periphery of Pangea. The Totoltepec pluton consists of minor mafi c-ultramafi c rocks (306 ± 2 Ma) that are marginal to the main felsic-mafi c intrusion (289 ± 2 Ma). Both intrusive phases have an arc geochemistry but are more primitive than contemporaneous arc complexes in southern Mexico. The Chi-chihualtepec Tecomate Formation was derived from a late Paleozoic arc.

Along-Arc Variation

Whereas Torres et al. (1999) advocated the presence of a Permian–Triassic arc, the ca. 306 Ma age and the arc geochemistry of the gabbroic component of the Totoltepec pluton provide fi rm evidence of magmatic arc activity in the Pennsylvanian. Other igneous rocks of a similar age in the southern part of the North American Cordillera (Fig. 2) include the Cua-naná plutonic complex (Vega-Carrillo et al., 1998), which yielded a SHRIMP U-Pb age of 307 ± 2 Ma (Elías Herrera et al., 2005), and ca. 313–318 Ma granitic to dioritic intrusions in the Altos Cuchumatanes, Guatemala (Solari et al., 2010). Further north, the Aserradero rhyolite in the Sierra Madre terrane yielded a U-Pb TIMS age of 334 ± 39 Ma (Stewart et al., 1999), and in the Coahuila terrane, the La Pezuña rhyolite was dated at 331 ± 4 Ma (Lopez et al., 1996). However, due to the lack of geochemical data, an arc association of these Carboniferous rocks can only be substantiated for the Totoltepec plu-ton and the Altos Cuchumatanes granitoids.

The overall spatial, geochemical, and iso topic similarity of the ca. 289 Ma main body of the

Sample / chondrite

1

10

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

B

A

Samples / upper continental crust

0.1

1

10

Cs Rb Ba Th U Nb Ta K La Ce Pr Sr Nd Zr Sm Eu Ti Dy Y Yb Lu Hf Tb Tm Gd Ho Er

UC (Taylor and McLennan,1985)

Metapsammite

Meta-arkose

Metapelite

Figure 13. (A) Chondrite-normalized rare earth element (REE) plot (normalizing values from Sun and McDonough, 1989); and (B) upper continental (UC) crust–normalized trace-element diagram (normalizing values from Taylor and McLennan, 1995) of Chichihualtepec Tecomate Formation metasedimentary rocks.




Totoltepec pluton with the precursor 306 Ma gabbroic rocks suggests that regional arc ac-tivity continued into the Early Permian. Other evidence for Early Permian arc magmatism in southern Mexico (Figs. 2 and 14) includes the 270 ± 3 Ma Cozahuico granite (Elías-Herrera and Ortega-Gutiérrez, 2002; Elías-Herrera et al., 2005), the 275 ± 4 Ma La Carbonera stock (Solari et al., 2001), a 272 ± 10 Ma tonalitic gneiss in the Xolapa Complex (Ducea et al., 2004), and an arc-related orthogneiss in the Chiapas Mas-sif that yielded a U-Pb SHRIMP age of 272 ± 3 Ma (Weber et al., 2007). Arc-related ca. 270–280 Ma granitoid plutons intruding Caborca ter-rane basement in northwestern Mexico (Arvizu et al., 2009; Riggs et al., 2009, 2010) indicate that Early Permian arc magmatism extended into the North American craton.

Arc magmatism in southern Mexico is likely to have continued into the Middle to Early Permian , as suggested by an arc-related ortho gneiss of 258 ± 2 Ma age in the Chiapas Massif (Weber et al., 2005) and by a crystallization age of 254 ± 7 Ma for the Mixtequita stock in the Maya ter-rane (Murillo-Muñeton, 1994). The northern extension of the Early to Middle Permian con-

tinental arc into terranes of the North Ameri-can craton is represented by ca. 258 Ma to ca. 266 Ma arc-related granites and granodiorites in the Sierra Pinta (Arvizu et al., 2009).

This fragmentary record of late Paleozoic arc magmatism is in broad agreement with a num-ber of Permian K-Ar and Rb-Sr ages of igne-ous rocks in Mexico (Fig. 2; Ruiz-Castellanos, 1979; Damon et al., 1981; Torres et al., 1999; Grajales-Nishimura et al., 1999).

The Chichihualtepec Tecomate Formation strata, containing interstratifi ed arc-derived vol-canic and clastic rocks, provide complementary data on the nature of the late Paleozoic evolu-tion of the shallow crust. Much of the Chichi-hualtepec Tecomate Formation was deposited before the Totoltepec pluton was exposed. De-trital zircon, geochemical and Sm-Nd isotopic data, together with the presence of plutoniclastic conglomerate, indicate that the Chichihualtepec Tecomate Formation was largely derived from a regional arc. The local abundance of thin gran-itoid dikes and very fi ne-grained, green, tuffa-ceous strata in the Chichihualtepec Tecomate Formation suggests that arc activity was con-temporaneous with Chichihualtepec Tecomate

Formation deposition. Evidence of arc activity in southern Mexico (Figs. 2 and 14) may also be preserved in (1) the latest Pennsylvanian to Middle Permian Tecomate Formation type area, which contains mafi c fl ows, tuffs, and rare fel-sic units (Keppie et al., 2004b; Sánchez-Zavala, 2008), (2) the Middle Permian Los Hornos For-mation (Ramírez et al., 2000; Vachard et al., 2004), and (3) the uppermost Devonian to Lower Permian Patlanoaya Group, which con-tains intercalations of bentonite horizons repre-senting ash-fall deposits (Vachard et al., 2000; Vachard and de Dios, 2002). The un deformed Olinalá Formation of Middle to Upper Permian age (Buitrón et al., 2005) is potentially also partially correlative with the Chichihualtepec Tecomate Formation strata, although volcanic rocks have not been described in this unit. Fur-ther north, the magmatic arc is characterized by (1) the Early to Middle Permian Tuzancoa For-mation (Sierra Madre terrane), which contains andesitic to basaltic lava fl ows and felsic tuffs (Rosales-Lagarde et al., 2005), (2) the Early Permian bentonite-bearing Guacamaya Forma-tion in the Sierra Madre terrane (Gursky and Michalzik , 1989), (3) the late Mississippian to

PE

RM

IAN

CA

RB

ON

IFE

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US

MISSIS-

SIPPIAN

PENNSYL-

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L

M

E

251

260

271

299

Age

(M

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318

359

Mixteca Oaxaquia Maya SierraMadre

Coahuila Xolapa Chihuahua Caborca

Toto

ltepe

c

Cuanana

Cozahuico

La Carbonera

Igneous arc-related rocksdated by U-Pb geochronology

Sedimentary arc-assemblagescontaining intercalated arc-related volcanic rocks

AltosCuchumatanes

La Pezuña

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mat

e F

m./

CT

FP

atla

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a G

roup

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ncoa

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.G

uaca

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Las

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icia

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m.

Aserradero

TonaliticgneissChiapas

Massiforthogneiss

ChiapasMassif

orthogneiss

Mixtequita

Sierra Pinta

Los Tanques

Sonoyta

Toto

ltepe

c

Figure 14. Correlation chart of various arc-related igneous and sedimentary suites of Carboniferous to Permian age sorted according to their location in the various tectonostratigraphic terranes of Mexico. For references see text.


Kirsch et al.


Middle Permian Las Delicias Formation in the Coahuila terrane (McKee et al., 1999), which contains interstratifi ed rhyolites, and (4) the Early Permian, bentonite-bearing Rara Forma-tion of the Sierra del Cuervo in the southern ex-tension of the North American craton (Handschy and Dyer, 1987).

As one of the samples from near the strati-graphic base of the Chichihualtepec Tecomate Formation does not contain any Carboniferous–Permian zircons, this regional magmatic arc in southern Mexico is inferred to have started developing during Chichihualtepec Tecomate Formation deposition (Figs. 15A and 15B). The Totoltepec pluton did not become a source for the Chichihualtepec Tecomate Formation until ca. 275 Ma, by which time a signifi cant amount of the arc crust had been removed to expose the pluton (Fig. 15C). Although the population peak of the late Paleozoic detrital zircon record of the Chichihualtepec Tecomate Formation occurs at an age of ca. 307 Ma (Fig. 6), the detrital zir-con record extends back to ca. 344 Ma without any signifi cant gaps, suggesting that regional magmatic arc activity may have initiated in the Mississippian.

Taken together, the data suggest that arc mag-matism had commenced in some of the southern to central Mexican continental blocks by Mis-sissippian times, whereas it probably did not become established in the Laurentian (northern) part of Mexico until the Early Permian (Fig. 14).

Across-Arc Variation

There are subtle differences in the geochemi-cal and isotopic compositions between the various magmatic arc suites of southern Mexico and Guatemala. For rocks with the same SiO

2

content, the Totoltepec pluton exhibits lower HFSE (Nb, Ta, LREEs, Zr) and LILE (Rb, Th, K) abundances and more radiogenic Sm-Nd iso-topic compositions relative to the intermediate to felsic suites in both Oaxaquia and the Maya block, which also contain evidence of substan-tial crustal contamination. As certain southern Mexican arc suites of different age show simi-lar geochemical characteristics and certain arc suites of roughly the same age show different geochemical characteristics, the compositional differences cannot be ascribed to temporal variations in arc magmatism. Instead, observed contrasts in composition between the individual arc suites considered in this paper are attributed to spatial intra-arc variation.

In general, arc rock compositions vary both in time and with distance from the active trench, refl ecting increasing degrees of AFC as mag-mas pass through thicker crust, and a change from subduction-enriched to within-plate man-

Pre-arcca. 330 Ma (?)

Arcdevelopment

ca. 300 Ma

Late arc:Tt exhumation

ca. 270 Ma

Tt—TotoltepecCz—CozahuicoCu—CuananáCa—La CarboneraTz—TuzancoaCh—Chiapas MassifAc—Altos Cuchumatanes

ctf/tf—Chichihualtepec Tecomate/ Tecomatepa—Patlanoayagu/dm—Guacamaya/ Del Monte

Plutons

Lava flowMX—Mixteca terraneOAX—Oaxaquia terraneMAYA—Maya block

A

B

C

+++

v vv

Basement

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Sedimenttransport

+ +++

+

Tt

Cu

pa

ctf/tf

Ac

++

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++

MX OAX MAYA

pa

ctf/tf

pagu/dm

ctf/tf

sea level

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Fault, inferred

Tt CzCa

Tz

Ch

+++++

+ +++ ++

+ + ++

sea level

+ ++Ac

++ Cu

vv v

sea level

?

?

?

exposedbasement

50 km

Figure 15. Generalized sections across the active western margin of Pangea in the late Paleo-zoic, showing arc development and the relative locations of the various magmatic arc assem-blages in southern Mexico and Guatemala.




tle sources (e.g., Brown et al., 1984). Typical transverse geochemical variations include a systematic increase in LILEs, HFSEs, and al-kalis and a decrease in LILE/HFSE ratios and εNd values from the front to the rear of the arc (Kimura et al., 2010, and references therein). Hence, in order to account for the more juvenile composition of the Totoltepec pluton in com-parison to other Carboniferous–Permian arc suites in Mexico and Guatemala, the Totoltepec pluton is inferred to have been emplaced into a more primitive, less mature location within the Carboniferous–Permian arc. In this model, the pluton would constitute a more trenchward part of the arc, lying to the west (modern coor-dinates) of the more mature arc suites inferred to represent a more inboard location (Figs. 15B and 15C). Assuming that the southern Mexican crustal blocks, in which the Mixteca terrane oc-cupies the western, most outboard position rela-tive to Oaxaquia and the Maya block (Fig. 1A), were only involved in lateral translation relative to each other along transcurrent faults trend-ing along strike of the arc (e.g., Dickinson and Lawton, 2001), the position of the Totoltepec pluton relative to the other southern Mexican arc suites should not have changed substantially since the late Paleozoic. Hence, the increased arc maturity is consistent with models that ad-vocate an eastward polarity of subduction (e.g., Centeno-García, 2005; Keppie et al., 2008a). An alternative (but not necessarily mutually exclusive) model to explain the geochemical differences between the Totoltepec pluton and contemporaneous arc-related plutonic rocks in southern Mexico involves the emplacement of the Totoltepec pluton along a fault in the arc that facilitated its ascent and made it less prone to contamination. This model is consistent with transtensional kinematics associated with strike-slip faulting documented in Chichihual-tepec Tecomate Formation metaconglomerates (Morales-Gámez et al., 2009) and evidence for the syntectonic emplacement of the Totoltepec pluton (Kirsch et al., 2012).

Pangea Implications

Late Carboniferous continental collision in Mexico was a key event in the amalgamation of Pangea and is expressed by a southerly source for fl ysch deposits in the Ouachitan orogeny in the Mississippian (Arbenz, 1989) and by the ap-pearance of early Mississippian fossils in Oaxa-quia with Midcontinent (U.S.) faunal affi ni ties (Navarro-Santillán et al., 2002). Because Car-boniferous to Permian continental arc mag-matism recorded by the Totoltepec pluton, the Chichihualtepec Tecomate Formation, and cor-relative rocks elsewhere in the belt postdates the

amalgamation of Pangea, a location of the Mix-teca terrane adjacent to a subducting part of the Panthalassa Ocean on the periphery of Pangea-A seems most likely (Fig. 1A). Such a location is preferable to models that assign the Mixteca terrane to a position within Pangea, either off northeastern Canada (Fig. 1C; Böhnel, 1999) or in the Gulf of Mexico, ~2000 km inland from the western margin of Pangea (Vega-Granillo et al., 2009; Fig. 1B), because these locations lie too far from any potential subducting ocean.

ACKNOWLEDGMENTS

We acknowledge the Consejo Nacional de Cien-cia y Tecnología (CONACyT; Project CB-2005-1: 24894), Programa de Apoyo a Proyectos de In-vestigación e Innovación Tecnológica (PAPIIT: IN100108-3), and a Natural Sciences and Engineer-ing Research Council of Canada Discovery grant to Murphy for funds to support the fi eld work and geochemical and isotopic analyses. Carlos Ortega-Obregón and Ofelia Pérez-Arvizu provided technical assistance in the Laboratorio de Estudios Isotópicos, Centro de Geociencias. Kirsch is grateful to Maria Helbig for help in the fi eld and with fi gure prepara-tion. We thank Associate Editor Luca Ferrari, and re-viewers Peter Schaaf and Bodo Weber, as well as two anonymous reviewers, for constructive comments on this and a previous version of the manuscript. This is a contribution to International Geological Correlation Project 597.

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SCIENCE EDITOR: NANCY RIGGS

ASSOCIATE EDITOR: LUCA FERRARI

MANUSCRIPT RECEIVED 23 NOVEMBER 2011REVISED MANUSCRIPT RECEIVED 13 FEBRUARY 2012MANUSCRIPT ACCEPTED 18 MARCH 2012

Printed in the USA


3H I S T O R I A E S T R U C T U R A L D E L P L U T Ó N T O T O LT E P E C

Artículo: Kirsch, M., Keppie, J.D., Murphy, J.B., y Lee, J.K.W., Arc plu-tonism in a transtensional regime: the Late Palaeozoic Totoltepec pluton,Acatlán Complex, southern Mexico: International Geology Review, en pren-sa, doi: 10.1080/00206814.2012.693247.


Moritz Kirsch: concepción y el diseño del estudio; trabajo de campoel cual incluye mapeo, obtención de datos estructurales, selección depuntos de muestreo y toma de muestras para el análisis de petrografíay de microsonda, así como la geocronología 40Ar/39Ar; adquisiciónde datos de microsonda; revisión de literatura; análisis y interpreta-ción de datos; redacción del artículo.

J. Duncan Keppie: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.

J. Brendan Murphy: contribución a la concepción y el diseño; supervi-sión de las actividades de campo; participación en la interpretación delos datos y en la revisión del artículo remitido; adquisición de fondos.

James K.W. Lee: participación en la interpretación de datos y en la re-visión del artículo sometido; encargado de las instalaciones de análisis40Ar/39Ar.

33

International Geology ReviewiFirst, 2012, 1–24

Arc plutonism in a transtensional regime: the late Palaeozoic Totoltepec pluton, AcatlánComplex, southern Mexico

Moritz Kirscha*, J. Duncan Keppieb , J. Brendan Murphyc and James K.W. Leed

aCentro de Geociencias, Universidad Nacional Autónoma de México, 76230 Querétaro, Mexico; bDepartamento de Geología Regional,Instituto de Geología, Universidad Nacional Autónoma de México, 04510 México D.F., Mexico; cDepartment of Earth Sciences,

St. Francis Xavier University, Antigonish, NS, Canada; dDepartment of Geological Sciences and Geological Engineering, Queen’sUniversity, Kingston, ON K7L 3N6, Canada

(Accepted 9 May 2012)

The ENE-trending, ca. 306–287 Ma, Totoltepec pluton is part of a Carboniferous–Permian continental magmatic arc onthe western Pangaean margin. The 15 km × 5 km pluton is bounded by two N–S Permian dextral faults, an E–W thrustto the south, and an E–W normal fault to the north. Thermobarometric data indicate that the main, ca. 289–287 Ma, partof the pluton was emplaced at ≤20 km depth and ≥700◦C and was exhumed to 11 km and 400◦C in 4 ± 2 million years.We have documented the following intrusive sequence: (1) the 306 Ma northern marginal mafic phase; (2) the 287 Mamain trondhjemitic phase; and (3) ca. 289–283 Ma sub-vertical dikes that vary from (a) N39E, undeformed with crystalgrowth perpendicular to the margins, through (b) ca. N50–73E, foliated and folded with sinistral shear indicators, to (c)N73–140E and boudinaged. The obliquity of the boundary between the folded and stretched dikes relative to the N–S dextralfaults suggests sequential emplacement in a transtensional regime (with 20% E–W extension), followed by different degreesof clockwise rotation passing through a shortening field accompanied by sinistral shear into an extensional field. The ca.289–287 Ma intrusion also contains a steep ENE-striking foliation and hornblende lineations varying from sub-horizontalto steeply plunging, probably the result of emplacement in a triclinic strain regime. We infer that magmatism ceased whensome of the dextral motion was transferred from the western to the eastern bounding fault, causing thrusting to take placealong the southern boundary of the pluton. This mechanism is also invoked for the rapid uplift and exhumation of the plutonbetween ca. 287 Ma and 283 Ma. The distinctive characteristics of the Totoltepec pluton should prove useful in identifyingsimilar tectonic settings within continental arcs.

Keywords: emplacement; syntectonic pluton emplacement; magmatic arc; transtension; Acatlán Complex; Mexico; Pangaea

Introduction

Calc-alkaline magmatism at convergent plate margins iscommonly associated with strike–slip faulting (e.g. Fitch1972; Jarrard 1986; Glazner 1991; Tobisch and Cruden1995; Gibbons and Moreno 2002), which provides conduitsfor magma ascent, accommodates pluton emplacement(Tikoff and Teyssier 1992; Grocott et al. 1994; Grocottand Taylor 2002), and facilitates the exhumation of deepercrustal sections (Crawford et al. 1999; Žák et al. 2005).Due to the complex interaction between thermal and struc-tural effects of plutonism and regional-scale deformation,the mechanisms responsible for pluton emplacement incontinental magmatic arcs have attracted much attention.

We present a case study of the mechanisms control-ling the emplacement of the ca. 306–287 Ma, supra-subduction zone Totoltepec pluton in the eastern AcatlánComplex, southern Mexico. This pluton is representativeof a Pennsylvanian to Early Permian arc assemblage

*Corresponding author. Email: [email protected]

along the western margin of Pangaea that developedsoon after Pangaea formed (e.g. Torres et al. 1999;Dickinson and Lawton 2001; Centeno-García 2005). A pre-vious contribution (Kirsch et al. 2012) documented thegeochemical/isotopic characteristics and age of the plu-ton, and indicates that the body is a composite intrusionwith mantle and crustal sources, emplaced along an imma-ture, trenchward part of the late Palaeozoic continentalarc. In this article, we use a combination of meso- andmicrofabric analyses, Al-in-hornblende thermobarometryand 40Ar/39Ar geochronology, which provide evidence for(1) the incremental assembly of the pluton (e.g. Colemanet al. 2004; Glazner et al. 2004; de Saint Blanquat et al.2006; Pignotta et al. 2010), (2) sequential injection ofsheets (Miller and Paterson 2001; Mahan et al. 2003),(3) progressive fabric development during crystallizationof the pluton in a strain field (e.g. Paterson et al. 1989,1998; Tribe and D’Lemos 1996; Barros et al. 2001), and

ISSN 0020-6814 print/ISSN 1938-2839 online© 2012 Taylor & Francishttp://dx.doi.org/10.1080/00206814.2012.693247http://www.tandfonline.com

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(4) intrusion in a transtensional environment (Petford andAtherton 1992; Paterson and Fowler 1993; Hanson andGlazner 1995; Kratinová et al. 2007). Given the plutonlocation, our data also provide insights into the geody-namic evolution of the late Palaeozoic magmatic arc thatdeveloped along the periphery of Pangaea.

Geological setting

The Totoltepec pluton is well-exposed in the eastern partof the Palaeozoic Acatlán Complex (Figure 1A; Mixtecaterrane) and is one of several Carboniferous to Permianintrusions associated with a continental magmatic arcthat formed as a consequence of subduction along thepalaeo-Pacific margin of Pangaea (Torres et al. 1999;Keppie et al. 2004a; Kirsch et al. 2012). The AcatlánComplex is tectonically bound to the south by theCenozoic La Venta/Chacalapa Fault (Solari et al. 2007;Tolson 2007), juxtaposing it against the Xolapa Complex(Figure 1A). To the west, the Acatlán Complex is thrustover Cretaceous platformal carbonates, located betweenthe exposed Acatlán Complex and the accreted Guerreroterrane (Centeno-García et al. 2008; Ramos-Arias andKeppie 2011). To the north, the complex is uncon-formably overlain by Mesozoic rocks and the CenozoicTrans-Mexican Volcanic Belt (Ferrari et al. 1999). To theeast, the Acatlán Complex is bounded by the >150 km-long, N–S-striking, dextral Caltepec Fault Zone (CFZ),which separates it from the ∼1 Ga Oaxacan Complex(Elías-Herrera and Ortega-Gutiérrez 2002). White micafrom a mylonitic mica schist in the CFZ yielded a40Ar/39Ar age of ca. 269 million years (Elías-Herreraet al. 2005). However, two syntectonic plutons – the ca.307 Ma Cuananá plutonic complex and the ca. 270 MaCozahuico granite – attest to tectonomagmatic activityalong this fault during late Pennsylvanian to Early Permiantimes.

The Totoltepec pluton is approximately elliptical inmap view; its long axis (15 km) trends roughly WNW–ENE (Figure 1B) and it crops out over an area of 68 km2

with a relief of 490 m. External contacts between theTotoltepec pluton and the surrounding strata are eithernon-conformable or tectonic (Malone et al. 2002), i.e.none of the original contact relationships are preserved.Along its southern margin, the Totoltepec pluton is thrustover intensely deformed, lower greenschist-facies metased-imentary rocks of the Pennsylvanian to Middle PermianTecomate Formation (Keppie et al. 2004b; Kirsch et al.2012). To the east, an unnamed, medium-grade metamor-phic unit consisting of garnet schist and quartzite with rareamphibolite dikes is faulted against the Totoltepec plu-ton (Kirsch et al. 2012). To the north, the granitoid bodyis unconformably overlain by and faulted against redbedsof inferred Jurassic age (Malone et al. 2002). The N–Strending, dextral San Jerónimo fault (Morales-Gámez et al.

2009) separates the pluton from the Tecomate Formationand Jurassic redbeds along its western margin.

Field relationships and geochronological data indicatethat the Totoltepec pluton was emplaced over a ca. 19 mil-lion year period involving at least two discrete intrusions,i.e. (1) 306 ± 2 Ma, mafic–ultramafic intrusive bodiesof hornblende-rich gabbros and hornblendites that occuras three minor (0.2–0.6 km2), elongate, fault-boundedbodies distributed along the northern and northeasternmargin of the pluton (Kirsch et al. 2012), and (2) themain body, making up approximately 98% of the exposedarea, dated at 287 ± 2 Ma (trondhjemite: Yañez et al.1991), 289 ± 1 Ma (diorite: Keppie et al. 2004a), and289 ± 2 Ma (quartz diorite: Kirsch et al. 2012), rang-ing in composition (in order of decreasing proportion)from trondhjemite (hornblende-rich) tonalite, and dioriteto quartz granitoid, granodiorite, monzogranite, and rareplagioclase-rich (cumulate?) layers.

Geochemistry of the older marginal Totoltepec mafic–ultramafic rocks indicates an arc tholeiitic to calc-alkalineaffinity characterized by high LILE/HFSE ratios, flat REEpatterns, and initial εNd values of +1.3 to +3.3 (t =306 Ma). The younger Totoltepec main body exhibits acalc-alkaline trace-element geochemistry with flat to mod-erately fractionated LREE-enriched patterns, and initialεNd values of –0.8 to +2.6 (t = 289 Ma; Kirsch et al.2012). Although minor degrees of crustal assimilation andfractionation processes are detected by simple isotopicmodelling, the isotopic data plot within the evolutionaryenvelope defined by Ordovician mafic rocks of the Mixtecaterrane interpreted to have been derived from a ca. 1.0 Gasubcontinental lithospheric mantle (Murphy et al. 2006;Ortega-Obregón et al. 2010).

Lithological units and internal contacts

The oldest, ca. 306 Ma gabbros and minor hornblenditesoccur in three fault-bounded, lenticular bodies along thenorthern and northeastern margin of the pluton. Thesemafic to ultramafic rocks are massive to weakly foliatedand, in places, possess a compositional banding. Locally,they are intruded by steep, <1 m-wide, intensely deformed,locally disrupted felsic dikes (Figure 2A) of inferred289–287 Ma age (Kirsch et al. 2012). The ca. 289–287 Marocks from the main body of the pluton have two modesof occurrence: (1) hornblende-bearing mafic to interme-diate rocks, which occur as sheets consisting of compo-sitionally banded, foliated, locally mylonitic, fine grainedto megacrystic hornblende diorite, quartz diorite, andtonalite and (2) felsic rocks, forming the interior andlargest proportion of the Totoltepec pluton, chiefly com-posed of equigranular, weakly to moderately foliatedtrondhjemite.

The mafic–intermediate sheeted domain occurs assmaller bodies along the southern margin of the pluton

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International Geology Review 3

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FoliationLineationContactContact, inferred Strike–slip faultNormal faultThrust fault

U/Pb and Ar/Ar ages Microprobe sampling pts.

CretaceousJurassic

ChichihualtepecTecomate Fm.Unnamed Unit

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Granodiorite, monzo-graniteTrondhjemite

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Figure 1. (A) Location of the study area (box) with respect to the principal geologic features of southern Mexico (modified from Keppieet al. 2008). (B) Simplified geological map and (C) interpretative cross section of the Totoltepec pluton and surrounding country rocks.Short, heavy dashes represent locations of measured foliations; crosses are interpreted foliation patterns.

and in a larger, margin-parallel, lenticular, sigmoidal zone(Figures 1B and 3). These zones are composed of steeplydipping to sub-vertical, aplitic to coarse-grained sheets,

or dikes of centimetre to several tens(?) of metres widthdisplaying variable degrees of pinch-and-swell undula-tions (Figure 2D). Locally, dikes occur as swarms of

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(A)

(D)

(B) (C)

(E)

(F) (G) (H)

(I) (J) (K)

Figure 2. Diking in the Totoltepec pluton. (A) Disaggregated felsic dike in marginal hornblende gabbro. (B) Swarm of parallel, narrow,interconnected mafic dikes that locally display tapering terminations. (C) Boudinaged composite dike with a felsic interior and a maficmargin. (D) Sequence of pinching and swelling dikes composing the mafic–intermediate sheeted domain in the southern part of thepluton. (E) Gently folded pegmatite dike, and (F) fabric-discordant late felsic dike in the sheeted zone. (G) Close-up of Figure 2E,showing elongate, sigmoidal quartz grains growing perpendicular to the dike margin. (H) Sigmoidal internal fabric of a felsic dike inthe mafic–intermediate sheeted zone. (I) Deflection of amphibole into the plane of cross-cutting dikes. (J) Aplitic dike cross-cutting thefabric of megacrystic diorite. Note the dike-internal foliation parallel to the dike margin. (K) Trondhjemite dike in the felsic interior of thepluton.

many parallel, narrow (2–15 cm wide), steep, anasto-mosing sheets that locally show tapering terminations(Figure 2B), or as 10–15 cm-wide composite dikes with a

felsic, pegmatitic interior and a mafic margin (Figure 2C).Dikes of trondhjemitic or quartz-rich granitoid compo-sition, which are inferred to be co-magmatic with the

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felsic pluton interior based on matching petrographic andgeochemical characteristics (Kirsch et al. 2012), intrudethe mafic–intermediate sheeted domain and are commonlylaterally traceable for several metres along strike. Thesefelsic dikes are generally steep and either (1) fabric-discordant, around 10 cm wide, and undeformed to gen-tly folded (Figures 2E and 2F) or (2) fabric-concordant,5–40 cm wide, and exhibiting pinch-and-swell as well asboudinage structures (e.g. Figure 3D). The felsic dikes varyfrom fine grained to pegmatitic. The transition betweenthe mafic–intermediate sheeted zone and the more felsicpluton interior is characterized by the gradual decrease inthe occurrence of mafic dikes.

Compared with the mafic–intermediate sheeteddomain, the felsic interior part of the pluton is compo-sitionally and texturally more homogeneous. In certainlocations, however, the felsic interior exhibits elevatedmodal plagioclase or biotite, with subordinate granodioriteand monzogranite occurring near the northern boundaryof the pluton. Moreover, although less conspicuous dueto their compositional similarity, felsic dikes intrudetrondhjemite in the main body of the pluton (Figure 2K).

Enclaves in the Totoltepec pluton are very rareand heterogeneously distributed (Figure 4). In themafic–intermediate sheeted domain, these includecentimetre- to decimetre-sized, rounded to elongate,foliated microgranular enclaves (autoliths) of dioriticcomposition (Figure 4A), whose contacts with the igneoushost are defined by chilled margins or dark, hornblende-rich reaction rims (Figure 4B). Elongate enclaves arecommonly oriented parallel to the foliation in the hostrock (Figure 4C). Locally, within the mafic–intermediatesheeted domain, 5–15 cm-long, partly disaggregated clotsof hornblende can be observed (Figure 4D). The interiorfelsic domain locally contains (1) isolated, centimetre-sized, ovoid globules made up of coarse-grained biotite(Figure 4E) and (2) strongly sheared, fault-bounded micro-dioritic enclaves of 25 cm length (Figure 4F). No xenolithsderived from the surrounding country rocks have beenrecognized in the Totoltepec pluton, consistent with theabsence of xenocrystic zircons (Kirsch et al. 2012).

Locally within the mafic–intermediate sheeted domain,a steeply dipping textural and compositional banding isdeveloped, made up of alternating coarse-grained and fine-grained bands that coincide with subtle differences inthe relative proportions of hornblende and plagioclase.This banding is most conspicuous in an outcrop east ofSanto Domingo Tonahuixtla (Figures 1B and 3), whereindividual layers are continuous for several metres alongstrike. In diorite, the banding is irregularly spaced, consist-ing of a few millimetres to about 1.5 cm-wide leucocraticand relatively coarse-grained bands, and approximately0.5–3.5 cm, locally bifurcating, dark (fine-grained) bands(Figure 3H). In tonalite, dark and light bands have a sim-ilar average width of about 3 cm (Figure 3I). In bothlithologies, light bands exhibit a porphyritic grain-size

distribution, containing hornblende (diorite) or plagioclase(tonalite) phenocrysts of up to 0.5–1 cm length in a fine-grained matrix. Dark bands are composed of small grainswith roughly equal grain size. The transition between lightand dark layers is generally sharp and the rocks tend tosplit along this anisotropy plane. Locally, within bandedtonalite, however, plagioclase phenocrysts are observedto grow across the boundaries between fine-grained andcoarse-grained domains.

Petrography

The ca. 306 Ma marginal mafic–ultramafic bodies of theTotoltepec pluton are dominated by hornblende gabbro,with averages of 53% modal plagioclase (labradorite), 37%amphibole, and 10% other phases including magnetite,ilmenite, chalcopyrite, muscovite, titanite, and zircon, aswell as secondary minerals epidote, chlorite, sericite, andantigorite. Locally, the gabbro grades into hornblendite,which is characterized by approximately 90% modalamphibole.

The ca. 289–287 Ma main body of the pluton pre-dominantly consists of trondhjemite, whose average modalcomposition is 54% plagioclase (oligoclase), 35% quartz,and 11% other constituents, including primary muscovite,biotite, apatite, magnetite, titaniferous magnetite, ilmenite,and zircon, as well as rare K-feldspar and titanite.Secondary minerals include albite (after oligoclase),sericite, chlorite, epidote, antigorite, haematite, andcalcite. Mafic–intermediate rocks in the southern partof the pluton are composed of hornblende-rich tonalite(32% andesine, 38% amphibole, 23% quartz, and 7%of other phases), hornblende-rich diorite (40% andesine,53% amphibole, and 7% other), and quartz-diorite (80%andesine, 15% quartz, and 5% other). Rare leucocraticfelsic dikes (see above) intruding this mafic–intermediatedomain have a composition corresponding to eithertrondhjemite or quartz-rich granitoid (68% quartz, 30%albite, and 2% other). East of the town of Totoltepec deGuerrero (Figure 1B), plagioclase-rich rocks (93% albite,3% quartz, and 4% other) and biotite trondhjemite (55%oligoclase, 35% quartz, 7% biotite, and 3% other) arethe predominant lithologies. Towards the northern marginof the pluton, the felsic rocks locally contain abundantpotassium feldspar (up to 40%) and are classified as gran-odiorite and monzogranite according to the nomenclatureof Streckeisen (1976).

Plagioclase is the predominant mineral of theTotoltepec pluton, occurring as subhedral to euhedralgrains varying in size from 2 mm to 6 mm. Dependingon lithology, plagioclase varies in composition from albite,through oligoclase to labradorite. In tonalite, diorite, andgabbro, plagioclase exhibits normal compositional zoning(Table DR-1; see supplementary material at http://dx.doi.org/10.1080/00206814.2012.693247). Biotite occurs asisolated, tabular grains or as inclusions in plagioclase.

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Figure 3. Subset of Figure 1B showing detailed structural information as well as photographs and pictograms of the most intriguingstructures within the high-strain zone in the southern part of the Totoltepec pluton. Stereograms show foliations and dike orientationplotted as great circles (continuous and dashed lines, respectively), lineations as filled triangles (+ shear sense if kinematic indicatorsfound). (A) C’ type shear band fabric indicating sinistral shear. Angle between shear band cleavage and shear zone boundary (SBZ) is15–35◦ (Blenkinsop and Treloar 1995). (B) Sigma-type hornblende porphyroclasts indicating sinistral kinematics. (C) Randomly orientedhornblende on the foliation plane. (D) Foliation-parallel shearband boudins of a felsic dike indicating left-lateral shear. (E) Curvatureof foliation indicating sinistral shear. (F) Lens-shaped boudins of a mafic dike with sinistral kinematics. (G) Strong mineral lineation inmegacrystic hornblende diorite indicating top-to-SSE thrusting. (H–I) Compositional/textural banding in hornblende diorite and tonalitedefined by variation in grain size and modal proportions of feldspar and hornblende. Note the growth of plagioclase phenocrysts acrosslayer boundaries in Figure 3I.

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(A)

(D)

(B)

(C)

(E) (F)

Figure 4. Magmatic enclaves in the Totoltepec pluton. (A) Foliated, rounded microgranular enclaves in hornblende diorite. (B)Hornblende-rich reaction rim marking the contact between a microgranular enclave and diorite host. (C) Elongate microgranular enclavealigned parallel to foliation of host diorite. (D) Disaggregated clot of hornblende in diorite. (E) Ovoid biotite globule in trondhjemite. (F)Strongly sheared, fault-bounded microdioritic enclave in trondhjemite.

Amphibole is by far the most abundant mafic min-eral in the Totoltepec pluton. It occurs as subhedralto euhedral, prismatic grains, 1–3 mm in length, andlocally as megacrysts up to 4 cm in length. It com-monly exhibits simple {100} twinning and commonly

contains inclusion of quartz, plagioclase, apatite, and titan-ite. In some thin sections, amphibole occurs as coarse,lath-shaped oikocrysts poikilitically enclosing euhedralplagioclase or subhedral to euhedral, oriented quartzgrains. In tonalite, quartz diorite, hornblende gabbro, and

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Magnesio-hornblende

Ferro-hornblende

Tschermakite

Ferro-tschermakitichornblende

Tschermakitichornblende

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6.06.16.26.36.46.56.66.76.86.97.0

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TT-13a,Tonalite (intermediate)TT-55, Tonalite (mafic)TT-54, Tonalite (mafic)TT-14, Qtz Diorite (mafic)TT-17, Hbl Gabbro (mafic)TT-28, Hornblendite (ultramafic)

Mainbody

Mar-ginal

Figure 5. Electron microprobe major-element data for amphiboles from the Totoltepec pluton (grey symbols – cores; black symbols –rims). (A) Mg/(Mg + Fe2+) vs. Si classification after Leake (1978) and Leake et al. (1997, 2004). (B) Plot of A-site occupancy against Si.Nomenclature after Leake (1978). (C) Six-fold Al plotted against 4-fold Al. Al determined according to the calculation scheme of Leake(1978) and Leake et al. (2004). Solid black line denotes slope of 1. Locations for different amphibole end-member compositions are fromLaird and Albee (1981). Mineral abbreviations after Whitney and Evans (2010).

hornblendite, amphiboles are calcic (i.e. have (Ca + Na)B

≥ 1.00 and NaB < 0.50 atoms per formula unit) (Leakeet al. 2003; Table DR-2; see supplementary material athttp://dx.doi.org/10.1080/00206814.2012.693247). On theMg/(Mg + Fe2+) vs. Si classification diagram (Figure 5A),

they range from (ferrian- to ferri-) tschermakite totschermakitic hornblende and magnesio-hornblende incomposition. A few amphiboles in the tonalite and horn-blendite have (Na + K)A ≥ 0.50, corresponding to hast-ingsite to magnesio-hastingsite. On the (Na + K)A vs.

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Si classification diagram (Figure 5B), the samples fall inthe field of hornblende, tschermakitic hornblende, parg-asitic hornblende, and tschermakite. Aluminium prefer-entially resides in the tetrahedral position (Figure 5C),which suggests the dominance of high-T edenite-type((Na, K)A AlIV = [ ]A Si) substitution. Si in all investi-gated amphiboles varies between 6.0 and 6.8. These overallcompositional characteristics are typical of igneous amphi-boles (Leake 1971; Leake et al. 2003). Although opticallycontinuous, most investigated amphiboles are zoned, andmost cores contain higher AlIV and (Na + K)A and lowerSi and Mg/(Mg + Fe2+) than rims.

Quartz generally occurs as interstitial, anhedral aggre-gates of variable grain size. The shapes of individual quartzclusters range from subspherical to lenticular. In places,quartz is present as hexagonal, equigranular, polygonizedgrains. It is also found as a vermicular intergrowth inplagioclase (myrmekite).

Biotite occurs as small euhedral inclusions in plagio-clase and more rarely as subhedral grains in the matrix.It is generally, partially, or entirely replaced by chlorite.In the area east of Totoltepec de Guerrero (Figure 1B),modal biotite is as high as 7%. Muscovite is ubiquitousin trondhjemite, occurring as large, discrete grains up to1.5 mm wide or as foliated aggregates wrapping aroundhornblende or plagioclase phenocrysts. Si contents ofinvestigated muscovite grains reach values of 3.17 performula unit (Table DR-3; see supplementary materialat http://dx.doi.org/10.1080/00206814.2012.693247), indi-cating the presence of a minor phengitic component (e.g.Massonne and Schreyer 1987).

Potassium feldspar occurs as rare interstitial, fine- tomedium-grained crystals of microcline. In granodiorite andmonzogranite near the northern margin, orthoclase formssubhedral phenocrysts up to 3 mm in diameter containingflame-shaped albite lamellae.

Opaque phases include (titaniferous) magnetite,ilmenite, and minor secondary pyrite and chalcopyrite(Table DR-4; see supplementary material at http://dx.doi.org/10.1080/00206814.2012.693247). Magnetite is spa-tially related to the main mafic minerals. It is dominantlysubhedral or euhedral with a diameter of up to 0.5 mm,containing lamellae of ilmenite, which are interpreted asoxidation–exsolution intergrowths. Two diorite samplesfrom the main body of the pluton contain ovoid interstitialintergrowths of ilmenite with euhedral apatite. Ilmeniteis also observed to form broad lamellae in sandwich-likeintergrowths with an impure Ti-Fe-Al bearing silicatephase.

Meso- and microstructures

Marginal, ultramafic–mafic plutonic phase (ca. 306 Ma)

Mesoscopic structures in the older, ultramafic–mafic rocksof the pluton are preserved in one of the gabbroic

bodies along the northern margin. Here, a weak magmaticfoliation, defined by the preferred orientation of prismaticto tabular amphibole, is steeply dipping to sub-vertical andappears to be folded about a steeply, westerly plungingfold axis (Figure 6F). An associated moderately plung-ing to sub-horizontal mineral lineation is locally definedby the alignment of sub- to euhedral, elongate amphibole.Dike orientations in this part of the marginal plutonic phaseare highly variable and can be explained by folding aboutan axis that coincides with the fold axis derived from thefoliation plane distribution. This suggests that the foliationand the dikes had similar pre-folding orientations.

Microstructures in the older, marginal phase of theTotoltepec pluton record magmatic through incipient solid-state deformation at high temperature. Magmatic texturesare typified by large, euhedral to subhedral, unstrained,and evenly distributed amphibole and plagioclase set ina feldspathic matrix that lacks evidence of plastic defor-mation. Plagioclase has a typically igneous composition(An54–57; Table DR-1) and is characterized by a nor-mal growth zoning. The amphibole also has an igneouscomposition (Figure 5) and occurs as independent, stubbyto lath-shaped crystals (Figure 7A) or as undeformedpoikilitic grains around plagioclase. Some thin sectionsfrom two of the ultramafic–mafic bodies at the north-eastern margin (Figure 8) contain textures indicative ofminor subsolidus deformation at high temperature, suchas (1) albite twins within plagioclase sub-grains that aremisoriented with respect to the host grain (Figure 7E), sug-gesting progressive sub-grain rotation recrystallization thatoccurred at temperatures above upper greenschist-faciesconditions (Fitz Gerald and Stünitz 1993; Rosenberg andStünitz 2003), and (2) evidence of myrmekite replacementat plagioclase grain peripheries, which has been interpretedto reflect deformation temperatures in excess of 500◦C(Menegon et al. 2006, and references therein).

Main, mafic–felsic plutonic phase (ca. 289–287 Ma)

The main body of the Totoltepec pluton contains amesoscopic foliation and lineation of variable intensity,which formed under a variety of temperature conditions.Foliations that are interpreted to reflect deformation inthe magmatic state or in a high-temperature solid stateare defined by the preferred orientation of elongate,undeformed, magmatic amphibole in mafic–intermediatelithologies. Commonly, amphibole is randomly distributedon the foliation plane (Figure 3C). Locally, however, asub-horizontal to sub-vertical lineation is defined by thealignment of sub- to euhedral amphibole laths within thefoliation plane. In the more leucocratic rocks, deforma-tion at magmatic to high-temperature, solid-state condi-tions is indicated by sub- to euhedral plagioclase andinterstitial quartz that define a weak planar grain-shapepreferred orientation as well as a poorly developed

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(A) (B)

(C) (D)

Mag

mat

ic d

omai

n

Hig

h-te

mpe

ratu

reso

lid-s

tate

dom

ain

Mod

erat

e-te

mpe

ratu

reso

lid-s

tate

dom

ain

Dik

e o

rien

tati

on

s

Low

-tem

pera

ture

solid

-sta

te d

omai

n

n(S) = 13n(L) = 1

n(S) = 51n(L) = 13

n = 58

n(S) = 26n(L) = 8

n(S) = 174n(L) = 34

n(S) = 8n(L) = 3n(D) = 6

(E)

MA

IN B

OD

YM

AR

GIN

AL B

OD

IES

Poles to foliationMineral lineation

(F)

FoliationDikes

Calculatedfold axisS

imp

lesh

ear

73°

39°

Undeformed/folded

Extended/boudinaged

Unclassified

Trans tens io nTr anspressio

Figure 6. Mesoscopic structural data from the Totoltepec pluton. (A–D) Foliation and lineation data for the magmatic as well as high-temperature, moderate-temperature, and low-temperature solid-state domains in the main body of the pluton. (E) Lower hemisphere, equalangle projection of dike orientations in the main phase of the pluton. 39◦ corresponds to the minimum clockwise (interpreted as initial)dike angle; 78◦ marks the clockwise angle of transition between folded dikes, and dikes that show pinch-and-swell and/or boudinage.Grey lines and arrows indicate the theoretical transitions between the field of finite shortening, and the field of finite shortening followedby extension based on forward modelling along a vertical, dextral N–S-striking shear zone boundary (modified after Kuiper and Jiang(2010)). See text for details. (F) Orientation of structural elements in the marginal mafic–ultramafic bodies of the Totoltepec pluton. Allstereograms (except Figure 6E) are equal-area, lower-hemisphere projections. Contours were drawn according to the method of Kamb(1959) using a 3σ significance level and a 2σ contour interval.

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(A) (B)

(D)(D)

0.1 mm

(H) (I)

0.75 mm 0.75 mm

0.75 mm 0.25 mm 0.1 mm

0.25 mm 0.25 mm0.75 mm

(C)

(D) (E)

(G)

(F)

Figure 7. Photomicrographs of characteristic textures in the magmatic domain (m), as well as high-T (hss), medium-T (mss), and low-T(lss) solid-state domains of the Totoltepec pluton. (A) Euhedral, randomly distributed amphibole (m). (B) Quartz with chess-board sub-grain pattern (hss). (C) Rectangular, mosaic-like contours in quartz (hss). (D) Equigranular, polygonal quartz grains (hss). (E) Sub-grainrotation in plagioclase (hss). (F) Myrmekite formation in plagioclase at the boundary with K-feldspar (hss). (G) Glide twins in plagioclase(mss). (H) Quartz aggregate recrystallized by sub-grain rotation (mss). (I) Fractured plagioclase grain with development of new grains bymicrocracking and bulging-recrystallization (lss).

1 2 3 4 5 km

Magmatic

High-temperature solid state

Moderate-temperature solid state

Low-temperature solid state

Figure 8. Spatial distribution of microstructural types within the Totoltepec pluton based on thin section analyses using criteria outlinedby Blumenfeld and Bouchez (1988), Paterson et al. (1989), Miller and Paterson (1994), and Büttner (1999).

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lineation. Locally, in the mafic–intermediate sheeteddomain, the foliation is defined by primary igneouscompositional banding (Figures 3H and 3I).

Mesoscopic fabrics of tectonic origin occur withina high-strain zone in the southern part of the pluton(Figure 3) and show pervasive recrystallization under sub-solidus conditions. In this zone, the foliation is definedby the preferred orientation of amphibole and plagioclase,as well as mica. An associated linear fabric is definedby the alignment of stretched amphibole and plagioclase(Figure 3G), which show evidence of straining (both ductilerecrystallization and fracturing) in a section perpendicularto the foliation and parallel to the lineation. The com-positions of recrystallized amphibole and plagioclase aresimilar to those of igneous grains.

In agreement with the range of observed mesoscopicfabrics, the younger, main phase of the Totoltepec plutonshows a continuum from primary igneous (i.e. pre-fullcrystallization) microstructures to those corresponding todeformation in the solid state (i.e. subsolidus). Criteriaoutlined by Blumenfeld and Bouchez (1988), Patersonet al. (1989), Miller and Paterson (1994), and Büttner(1999) allow the distinction of four microstructural types:(1) magmatic, (2) high-temperature (>500◦C) solid state,(3) moderate-temperature (450–500◦C) solid state, and(4) low-temperature solid state.

Magmatic microstructures in the main body of thepluton are predominantly encountered in the northeast-ern part and locally within the mafic–intermediate sheeteddomain near the southern margin of the pluton (Figure 8).They are characterized by coarse-grained plagioclase andamphibole laths with angular outlines surrounded bya largely isotropic matrix composed of ovoid, intersti-tial, optically continuous quartz, smaller grains of ran-domly distributed plagioclase, and decussate, undeformedmuscovite, and/or biotite. The plagioclase has a typicallyigneous composition (An30–45; Table DR-1), shows normalcompositional zoning, and commonly displays grain aggre-gation (synneusis) textures. Igneous amphibole (Figure 5)occurs as single subhedral poikilitic grains or as euhedralinclusions in plagioclase.

The majority of samples in the main ca. 289–287 Mabody of the pluton exhibit microstructures consistentwith high-temperature subsolidus deformation (Figure 8).Quartz shows (1) basal and prismatic (chess-board)sub-grain patterns (Figure 7B), indicating deformationat temperatures of about 650–750◦C (Mainprice et al.1986; Kruhl 1996), (2) lobate grain boundaries typicalof recrystallization by grain boundary migration (Hirthand Tullis 1992), (3) rectangular, mosaic-like contours(Figure 7C), suggesting strong crystallographic controlon grain boundary orientations under high-temperaturedeformation (Gapais and Barbarin 1986), and (4) astrain-free, equigranular, polygonal texture, characteris-tic of recovery and recrystallization processes above

epidote-amphibolite facies conditions (Figure 7D; Simpson1985). Plagioclase grains locally show evidence of sub-grain rotation recrystallization and myrmekitic intergrowth(Figure 7F).

Microstructural features diagnostic of moderate-temperature solid-state deformation mostly occur in sam-ples of high-strain zones in the southern part of thepluton (Figure 8) and include plagioclase showing a sweep-ing undulatory extinction, bent or tapering twin lamellae(Figure 7G), as well as internal fracturing (Fitz Geraldand Stünitz 1993). Locally, plagioclase is recrystallizedalong its margins, forming core-and-mantle structures.Muscovite occurs as kinked or bent grains, and as alignedfine-grained anastomosing laths that enclose relict phe-nocrysts. K-feldspar exhibits abundant perthite flames(Pryer 1993). Quartz is characterized by large relict grainsexhibiting patchy, undulose extinction passing laterallyinto polycrystalline quartz aggregates with irregular grainboundaries developed predominantly by sub-grain rotationrecrystallization (Figure 7H).

Low-temperature, solid-state microstructures in main-phase rocks of the Totoltepec pluton are also locally presentin high-strain zones near the southern margin of the pluton(Figure 8) and are characterized by a pervasive cataclas-tic texture (Figure 7I). The presence of angular plagioclasegrains and a wide range of grain sizes suggest that grain-size reduction in feldspar is achieved by microcrackingand comminution (Tullis and Yund 1987). Quartz exhibitsdeformation lamellae transected by bands of small, newgrains formed by bulging recrystallization (Hirth and Tullis1992). Feldspar and amphibole are almost entirely replacedby chlorite, sericite, epidote, and antigorite, indicatingfluid-enhanced deformation under lower greenschist-faciesconditions.

Overall, the orientations of the foliation in the mainpart of the pluton vary from (1) moderately northerly dip-ping in the southern part of the pluton, (2) sub-vertical,E–W striking in the centre, to (3) steeply southerly dip-ping in the northern part, defining a fan-like pattern inN–S cross section (Figure 1C). There is a close agree-ment in the orientation of foliations over the entire rangeof deformation temperatures (Figures 6A–6D). Moderate-to low-temperature foliations tend to be less steeply dip-ping, because these occur mainly in the southern part ofthe pluton.

The foliation within the mafic–intermediate, sheetedzone is deformed into intrafolial, mesoscopic, recum-bent, tight to isoclinal, predominantly S-shaped folds(Figure 9). Regional variations in the trend of foliationplanes throughout the pluton are attributed to map-scale, open, upright, gently northerly plunging folds,about which the southern thrust contact is also folded(Figure 1B).

Lineations show a variation in orientation fromsub-horizontal to down-dip (Figures 3G and 6A–6D).

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(A)

(B)

N

NFigure 9. Photographs of tight to isoclinal intrafolial folds in the mafic–intermediate sheeted domain of the Totoltepec pluton.

Sigma-type hornblende porphyroclasts in mylonitictonalite and diorite indicate sinistral to top-to-SSE kine-matics (Figure 3B). Further evidence for sinistral shearis provided by C’-type shear bands (Figure 3A), asym-metrically boudinaged mafic and felsic dikes (Figures 3Dand 3F), and foliation deflection patterns (Figures 2G–2Iand 3E).

The predominant orientation of dikes in the main bodyof the pluton is concordant with respect to the foliation(Figure 6E). However, the overall range in the orientationsof individual dikes and the variations in the amount ofstrain they display indicate the occurrence of several gen-erations of dikes. Undeformed or gently folded dikes aresteeply dipping and have typical strikes of 36◦–67◦ (mea-sured clockwise from north), typically cutting the fabricdeveloped in the earlier intrusive phases (Figures 2E, 2Fand 2J), whereas dikes exhibiting pinch-and-swell struc-tures or boudinage commonly occur at a low angle toor in the foliation plane and have strikes of 71◦–136◦(Figures 2D, 2H, and 6E). Many dikes in the mafic–intermediate sheeted domain contain a foliation that iseither sigmoidal or parallel with respect to dike margins,irrespective of the orientation of the dikes relative to the

foliation of the surrounding rocks (Figures 2G, 2H, and 2J).In a section perpendicular to the foliation and parallelto the local sub-horizontal lineation, amphibole is locallyobserved to be deflected into the plane of cross-cuttingdikes (Figure 2I).

Some areas in the Totoltepec pluton, particularly nearthe contacts, exhibit brittle features (Figure 10), includ-ing tension gashes, faults, and associated brecciationzones, jointing, small-scale horst-and-graben structures,and quartz-carbonate veins that are attributed to hydraulicfracturing and fluid mobilization late in the coolinghistory of the pluton, and to episode(s) of regionalpost-emplacement deformation. N-dipping fault planesand associated N-plunging slickensides within the plutonare consistent with top-to-the-S thrusting of the plutonover metasedimentary rocks of the Tecomate Formationas implied by the regional map (Figure 1B; Maloneet al. 2002). Muscovite from the low-angle, brittle–ductilethrust contact between the Totoltepec pluton and theTecomate Formation yields a mid-Triassic age (Kirschet al. 2012). Locally, this shear zone is associated witha Fe-P-REE deposit containing the mineral associationmagnetite, apatite, barite, chlorite, quartz, chalcopyrite, and

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NN

Trondhjemite

Gabbro

(A)

(D)

(B)

(C)

(E) (F)

Figure 10. Late- to post-emplacement brittle features in the Totoltepec pluton. (A) Fault contact between marginal gabbro and main bodytrondhjemite. (B) Small-scale, horst-and-graben structure in diorite. (C) Pegmatitic quartz-carbonate vein. (D) Jointing. (E) Myloniticthrust contact between the Totoltepec pluton and Tecomate Formation. (F) S-C fabrics in Tecomate Formation metasedimentary rocksindicating top-to-S thrusting.

a cerium mineral (Table DR-4; see supplementary mate-rial at http://dx.doi.org/10.1080/00206814.2012.693247).The mineralization is confined to two discrete, elongatedbodies of about 100 m length coinciding with strongaeromagnetic anomalies (Servicio Geológico Mexicano2004a,b).

Al-in-hornblende thermobarometry

Five samples of the Totoltepec pluton (one from the older,marginal bodies and four from the younger, main body)were selected for hornblende thermobarometry in orderto obtain an estimate of the emplacement temperaturesand pressures. For this purpose, coexisting hornblende and

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plagioclase were analysed by electron microprobe wave-length dispersive spectrometry (WDS) at the LaboratorioUniversitario de Petrología (LUP), Instituto de Geofísica,UNAM, Mexico City, Mexico. Representative analyticaldata are presented in Tables 1, DR-1, and DR-2.

As one of the only available means of calculatingemplacement temperatures in calc-alkaline igneous rocks,Blundy and Holland (1990) suggested that amphibole-plagioclase mineral pairs in equilibrium could be used asa geothermometer. Accounting for non-ideal amphibolesolid-solutions, the geothermometer was later extended byHolland and Blundy (1994), using two different exchangereactions: (A) edenite + 4 quartz = tremolite + albite,and (B) edenite + albite = richterite + anorthite. Whereasthermometer A is only applicable to quartz-bearing rocks,thermometer B can also be used for silica undersaturatedassemblages, but is restricted to temperatures in the rangeof 500–900◦C and plagioclase with XAn between 0.1 and0.9 as well as hornblende with XNa(M4) > 0.03, AlIV <

1.8 atoms per formula unit (pfu), and Si in the range of6.0–7.7 pfu. The precision of both thermometers is ±40◦Cat 1–15 kbar (Holland and Blundy 1994).

The selected samples satisfy all compositionalconstraints with respect to temperature and oxygenfugacity, so the geothermometers of Holland and Blundy(1994) are applicable. Because independent pressure dataare not available for the Totoltepec pluton, emplacementtemperatures were calculated at pressures ranging from0 kbar to 15 kbar using the HB-PLAG program devel-oped by Holland and Powell (http://www.esc.cam.ac.uk/research/research-groups/holland/hb-plag). Minimumand maximum pressures determined by the differentnon-temperature-corrected Al-in-hornblende barometers(Table 1) were used to define a narrow pressure interval,from which average temperature values were calculated.For sample TT-14 (gabbro from the older, marginal body),which does not contain quartz and thus does not fulfil theprerequisites of an Al-in-hornblende barometer, pressurelimits were adopted from the quartz-bearing tonalitesamples.

Geothermometric data yield essentially magmatic tem-peratures of mineral equilibration in all samples, rangingfrom 716◦C to 788◦C for thermometer A and 719◦Cto 843◦C for thermometer B. Using thermometer B,which according to Anderson (1996) yields more accu-rate results, the calculated median value of samples fromthe main body of the pluton is 762 ± 40◦C, whereas thehornblende gabbro from the northern marginal body yieldsa slightly higher median temperature of 807 ± 40◦C. Thesetemperatures are broadly consistent with temperatures cal-culated from the Ti-in-zircon geothermometer of Watsonet al. (2006), yielding 713 ± 76◦C (1σ error) for zir-cons of a quartz diorite from the main body of the plutonand 731 ± 49◦C for zircons from a marginal hornblende

gabbro sample (Table DR-6; see supplementary material athttp://dx.doi.org/10.1080/00206814.2012.693247).

Hammarstrom and Zen (1986) and Hollister et al.(1987) were the first to conduct empirical studies that sug-gested a relationship between the total Al-content of calcicamphiboles and the confining pressure. Subsequent exper-imental studies (Johnson and Rutherford 1989; Thomasand Ernst 1990; Schmidt 1992) confirmed this correla-tion. Based on these experiments, a number of calibrationsfor Al-in-hornblende barometry have been developed, withwhich an intrusion depth can be calculated from micro-probe measurements of amphiboles in granitoids. TheseAl-in-hornblende barometers only consider the pressure-dependent Tschermak substitution as an influence on theAl-content of hornblende. Their application, therefore,requires the presence of an appropriate buffer assemblage(Qz-Kfs-Pl-Hbl-Bt-Tit/Mag and fluid melt) to limit thethermodynamic degrees of freedom (Hammarstrom andZen 1986). Another important prerequisite is that anor-thite compositions of coexisting plagioclase should rangebetween 25% and 35% (Hollister et al. 1987).

Anderson and Smith (1995) recognized that tempera-ture also strongly influences the Al-content in hornblende(edenite substitution), developing a new formula that isbased on calibrations of Johnson and Rutherford (1989)and Schmidt (1992), but introducing a temperature-correction term to the pressure estimates. Apart from thelimitations mentioned above, the application of the Al-in-hornblende barometer of Anderson and Smith (1995) isfurthermore restricted to amphiboles that crystallized athigh f O2, i.e. have Fe# ≤ 0.65 and Fe3+/(Fe3++Fe2+) ≥0.25.

Hornblende crystallization pressures of the Totoltepecpluton were calculated with the calibration of Andersonand Smith (1995) and compared to the pressuresderived from Al-in-hornblende barometer calibrationsof Hammarstrom and Zen (1986), Hollister et al.(1987), Johnson and Rutherford (1989), and Schmidt(1992). The precision of these barometers is estimatedat ±0.5 to ±0.6 kbar (2σ ). All samples exhibit Fe#and Fe3+/(Fe3++Fe2+) ratios that indicate crystalliza-tion conditions under high oxygen fugacity, conformingto the requirements of the method. However, all of theselected samples from the Totoltepec pluton lack potassiumfeldspar, and most of them do not contain biotite or titanite(Table 1), so the calculated pressures should be consid-ered maximum values (Anderson and Smith 1995). Threesamples contain plagioclase with a higher An content thanrecommended, which may lead to lower Al content inhornblende and thus yield pressures that are lower thantheir true value (Anderson and Smith 1995). Temperaturecorrections were applied using median temperature valuescalculated by the amphibole-plagioclase thermometer ofHolland and Blundy (1994) (see above).

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Tabl

e1.

Res

ults

ofA

l-in

-hor

nble

nde

geot

herm

obar

omet

ry.

Lat

/L

onA

ge(d

ecim

alR

ock

type

Pair

PI

An

Am

pA

IP

Hzb

PH

olP

JRP

Sch

PA

Sc

Pav

gD

epth

dD

epth

T(e

dtr

)eT

(ed-

tr)f

Tav

gS

ampl

e(M

a)de

gree

s)as

sem

blag

eaA

mp-

PI

(%)

(tot

al)

(kba

r)(k

bar)

(kba

r)(k

bar)

(kba

r)(k

bar)

(km

)av

g(k

m)

(◦ C)

(◦ C)

(◦ C)

TT-

1428

9±

218

.208

433

Hbl

dior

ite

A1-

P1

44.1

1.72

14.

664.

873.

765.

183.

794.

1813

.715

.280

783

683

3−9

7.89

087

Hbl

PIM

sMag

lim

A2-

P3

45.2

1.90

05.

585.

894.

536.

034.

54±

16.5

±82

884

3±

A3-

P2

42.7

1.83

35.

245.

514.

245.

724.

260.

3915

.41.

480

382

211

TT-

13a

289

±2

18.2

1403

3To

nali

teA

1-P

131

.71.

992

6.06

6.43

4.93

6.47

4.93

5.29

18.0

19.3

788

780

755

−97.

8838

5H

blP

IQzB

tIIm

A2-

P3

32.5

2.12

96.

767.

215.

527.

125.

51±

20.1

±71

671

9±

A3-

P2

34.9

2.11

36.

667.

105.

447.

055.

440.

3119

.81.

176

576

632

TT-

5528

9±

218

.215

866

Tona

lite

A1-

P2

40.7

2.11

96.

667.

105.

447.

085.

475.

7919

.821

.174

375

575

5−9

7.88

085

Hbl

PIQ

zTiM

agA

2-P

341

.02.

379

7.97

8.57

6.54

8.31

6.56

±23

.8±

741

752

±A

3-P

140

.72.

104

6.60

7.04

5.39

7.01

5.40

0.65

19.6

2.4

750

757

3T

T-54

289

±2

18.2

2078

3To

nali

teA

1-P

129

.62.

327

7.74

8.31

6.34

8.07

6.35

6.03

23.1

22.0

757

752

762

−97.

8785

7H

blP

IMsQ

zIIm

A2-

P2

34.1

2.25

17.

347.

876.

017.

706.

02±

21.9

±78

878

8±

A3-

P3

29.3

2.18

37.

017.

505.

737.

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Hornblende diorite and marginal hornblende gabbroapparently yield much lower pressures than the other sam-ples of the Totoltepec pluton, because both of these sampleshave plagioclase compositions well outside the recom-mended range and, in addition, the diorite lacks quartz.They are thus omitted from further consideration. The aver-age hornblende Altot-content in tonalite from the mainbody of the pluton is 2.177 ± 0.122. Resulting pres-sures calculated with calibrations without a temperaturecorrection term range from 5.3 to 7.9 kbar (Table 1).The lowest values are obtained by the Al-in-hornblendebarometer of Johnson and Rutherford (1989), whereasthe formula of Hollister et al. (1987) yields the highestvalues. Because the amphibole-plagioclase thermometerof Holland and Blundy (1994) generates temperatureswell above the solidus of wet tonalite (Schmidt 1993), atemperature correction according to Anderson and Smith(1995) is reasonable. For samples within the recommendedcompositional range of plagioclase as well as tonalite sam-ple TT-55 with a slightly higher average XAn of 0.41,an average pressure of 5.7 ± 0.6 kbar is obtained. Thispressure value is equivalent to the average pressure calcu-lated with the Johnson and Rutherford (1989) barometer,which is attributable to the fact that the experiments con-ducted by Johnson and Rutherford (1989) were calibratedat temperatures between 720◦C and 780◦C, correspond-ing to the crystallization temperatures of hornblende fromthe Totoltepec pluton. The calculated emplacement pres-sure of 5.7 ± 0.6 kbar for tonalite from the main body ofthe pluton translates into a maximum emplacement depthof 20.7 ± 2.2 km, assuming an average crustal densityof 2.8 g/cm3. In summary, the main, ca. 289–287 Ma,body of the Totoltepec pluton was emplaced at mod-erate temperatures (762 ± 40◦C) and middle to highpressures (≤5.7 ± 0.6 kbar) into middle crustal levels(around 20 km).

40Ar/39Ar geochronology

Foliation-parallel muscovite between 180 and 250 μm insize was separated from a Totoltepec pluton trondhjemitesample E of Santo Domingo Tonahuixtla (TT-57: 18◦ 12′30′′ N, 97◦ 52′ 50′′ W). The mineral concentrate wasloaded into Al-foil packets and irradiated together withthe hb3gr hornblende standard (1072 ± 11 Ma) as a neu-tron flux monitor at the McMaster University researchreactor in Hamilton, Ontario, Canada. 40Ar/39Ar anal-yses were performed at the 40Ar/39Ar GeochronologyResearch Laboratory at Queen’s University in Kingstonby a laser step-heating procedure using a a 30W NewWave Research MIR 10–30 CO2 laser and a MAP216 mass spectrometer. The data, corrected for blanks,mass discrimination, and neutron-induced interferences,are presented in Table DR-5; see supplementary materialat http://dx.doi.org/10.1080/00206814.2012.693247 and in

AOR-1107 /TT-57Totoltepec pluton trondhjemiteMuscovite

2σ errors

Plateau age283 ± 1 Ma

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aren

t age

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a)

220

240

260

280

300

Fraction 39Ar (%)

0 10 20 30 40 50 60 70 80 90 100

Figure 11. 40Ar/39Ar age spectrum for foliation-parallelmuscovite from Totoltepec pluton trondhjemite. For sample loca-tion see Figure 1B.

Figure 11. The plateau age and mean square of theweighted deviates (MSWD) are obtained based on the fol-lowing criteria, i.e. when the apparent ages of at least threeconsecutive steps, comprising a minimum of 50% of thetotal 39Ar released, agree within 2σ error with the inte-grated age of the plateau segment (e.g. McDougall andHarrison 1999; Baksi 2006). All age errors are quoted atthe 2σ level.

Muscovite from sample TT-57 yields an excellentplateau age of 283 ± 1 million years (MSWD = 0.248),defined by 11 fractions and representing 99.2% of the total39Ar released (Figure 11). The first step, comprising 31%of atmospheric argon, is associated with a small amountof contaminating phases as indicated by the correspondingCa/K ratio (Table DR-6). Assuming a relatively high cool-ing rate of 50◦C/million years, consistent with the plateauage spectrum, the closure temperature for muscovite fromthis sample is calculated to be 390–400◦C, using the equa-tion developed by Dodson (1973). These data suggest thatby 283 ± 1 Ma, the main body of the Totoltepec plutonhad cooled through 390–400◦C. Assuming a geothermalgradient of 35◦C/km, which is consistent with modelledvalues for active portions of continental magmatic arcs(e.g. Rothstein and Manning 2003), the calculated clo-sure temperature for muscovite corresponds to a depth of11.1–11.4 km. Given that barometric data indicate that themain phase of the pluton was emplaced at around 20 km,the 40Ar/39Ar data require a substantial and rapid upliftand exhumation of the pluton between ca. 287 and 283 Ma(around 2.25 km/million years).

Discussion

Structural context

The Totoltepec pluton is a component of a regionalCarboniferous–Permian continental arc extending from

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Guatemala to the southern USA (Kirsch et al. 2012). In thesouthern Mexican portion of this arc, ca. 307–269 Madextral shear along the >150 km-long, N–S-striking CFZthat separates the Acatlán Complex from the OaxacanComplex (Figure 1A) has been well-documented (Elías-Herrera and Ortega-Gutiérrez 2002; Elías-Herrera et al.2005). The significance of dextral shear along N–S-strikingfaults within the Mexican Carboniferous–Permian con-tinental arc is further supported by the presence of aS-directed, dextral, sub-vertical, ca. 330–300 Ma fault(Dowe et al. 2005) that separates the Palaeozoic GranjenoSchist (a correlative of the Acatlán Complex; e.g. Nanceet al. 2007) from the ca. 1 Ga Novillo Gneiss (a correlativeof the Oaxacan Complex; e.g. Ortega-Gutiérrez et al. 1995)in northeastern Mexico. In addition, the Totoltepec plu-ton is bounded to the W by the N–S dextral San Jerónimofault. Muscovite from the N–S Las Ollas fault lying to thewest yielded a 40Ar/39Ar age of 278 ± 2 million years(Morales-Gámez et al. 2009).

The emplacement history of the Totoltepec plutoncan be explained within this regional context. The plutonoccurs in a crustal block bounded by two N–S-strikingdextral faults – the San Jerónimo fault to the west andthe Caltepec fault to the east (Figure 12). Dextral shearalong these boundary faults is inferred to have led to

the development of an intervening, sub-vertical, SW–NEextensional fault (Figure 12A), which may have controlledthe emplacement of the Totoltepec pluton. Progressivedextral movement on the bounding faults would have ledto clockwise rotation of NE–SW lines and objects in theintervening block.

Interpretation of dike orientations

The systematic variation in dike orientation with progres-sive strain (Figure 6E) is consistent with the hypothesisthat the Totoltepec pluton was emplaced during defor-mation. The younger dikes, as identified by cross-cuttingrelationships, are steeply dipping to vertical, undeformedto gently folded, and are discordant with respect to thefoliation. These dikes exhibit a minimum clockwise angleof 39◦ with respect to the N–S boundary faults, which isinferred to represent the initial dike orientation. The per-pendicular orientation of plagioclase and quartz adjacentto the margins of late SW–NE pegmatitic dikes in the mainphase of the pluton (Figure 2G) attests to the orthogo-nal dilation accompanying initial intrusion. A permissivemechanism of pluton emplacement along extensional frac-tures is also supported by the relatively minor crustal con-tamination of the mantle-derived, ultramafic–intermediate

entrainedblocks

trond-hjemite

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thrust

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ca. 289 Ma

CFZSJF

ca. 287 Ma

CFZSJF

ca. 283 Ma

39°?

A’

A

B’

B

D’

D

(A) (B)

C’

C

(D)(C)

Figure 12. Plan-view structural models and hypothetical cross-sections illustrating the emplacement of the Totoltepec pluton. (A)Intrusion of early mafic to ultramafic magma along a lineament in the transfer zone between the dextral, N–S-striking San JerónimoFault (SJF) and the Caltepec Fault Zone (CFZ). (B) Ascent of several sheet-like mafic to intermediate magma batches during regionaltranstension along a vertical, initially extensional SW–NE fault that became a WSW–ENE, sinistral cross-fault, rotating clockwise dueto dextral displacement on N–S boundary faults. (C) Synkinematic emplacement of a larger, more felsic batch of melt during continuedclockwise rotation of a cross-fault in the regional transtension zone. (D) Transference of dextral motion on the SJF to the CFZ, resultingin south-southeastward thrusting of the pluton and rapid uplift/exhumation.

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rocks and the lack of xenoliths or xenocrystic zircon inmarginal and main phases of the pluton (Kirsch et al.2012).

In contrast, older, sub-vertical dikes are folded, vari-ably sheared, foliation-concordant bodies that appear tohave been reoriented during progressive dextral shear. Withprogressive dextral shear on the bounding faults, theseNE-striking dikes would have initially rotated clockwiseinto a sector involving sinistral shear (Figure 12B), whichis consistent with the orientation of the sigmoidal inter-nal fabric of some dikes (Figures 2G and 2H) and thelocally observed deflection of amphibole into dike planes(Figure 2I). Further clockwise rotation of the dikes led tothe development of extensional structures, such as boudi-nage and pinch-and-swell.

In order to assess the significance of the dike array interms of the strain regime that accompanied its emplace-ment, we compare the dike patterns in the Totoltepecpluton to theoretical finite strain geometries and pre-dicted material line sectors for simple shear, transpression,and transtension (Figure 6E). The present surface of theTotoltepec pluton limits the strain analysis to 2D ratherthan a comprehensive 3D analysis (Kuiper and Jiang 2010).The ca. 307–269 Ma dextral shear along bounding verti-cal N–S faults was synchronous with emplacement of theTotoltepec pluton. If the movement on the N–S faults waspurely strike–slip, the transition from the shortening to theextensional field of the finite strain ellipse, i.e. between theorientation of folded dikes, and dikes that have been foldedand subsequently boudinaged, should occur at angles of 90◦to the N–S Caltepec and San Jerónimo faults. However,in the Totoltepec pluton, this transition occurs at angles of73◦, i.e. before the clockwise rotation reaches 90◦ relativeto the N–S-striking shear zone boundaries. This geometri-cal distribution pattern of material line sectors is indicativeof transtensional deformation (Figure 6E; Kuiper and Jiang2010).

Transtensional strain within the crustal block thatcontains the Totoltepec pluton is consistent with theprolate spheroid shapes in pebbles of metaconglom-erates in the Pennsylvanian–Middle Permian TecomateFormation north and south of the Totoltepec pluton(Morales-Gámez et al. 2009). The long axes of theseclasts are oriented parallel to the shallow NNE-plungingstretching lineation in the metasedimentary rocks ofthe Tecomate Formation. A sericitic phyllite from theTecomate Formation northwest of the Totoltepec plutonyielded a 40Ar/39Ar whole-rock age of 263 ± 3 millionyears (Morales-Gámez et al. 2009) and may record syn-tectonic growth of sericite. However, earlier transtensionaldeformation is indicated by the ca. 306 million year ageof the mafic part of the Totoltepec pluton, suggestingthat dextral movement along N–S striking faults in theregional arc was long-lived. Three components of strainare documented in the Totoltepec pluton: (1) NW–SE

extension, as indicated by the orientation of late pegmatiticdikes; (2) sub-vertical emplacement, as indicated bydown-dip hornblende mineral elongation lineations; and(3) sub-horizontal, WSW–ENE-directed sinistral shear, asindicated by along-strike mineral lineations and a rangeof different kinematic indicators. As there is no evidencefor one set of lineations overprinting another, and as bothsets of lineations are defined by magmatic hornblende, i.e.formed during the early stages of pluton crystallization,these three components of shear are inferred to belong to asingle episode of deformation. Although only 2D data areavailable for the Totoltepec pluton, the vorticity axis wasprobably oblique to these axes, indicating triclinic defor-mation (e.g. Jiang and Williams 1998; Lin et al. 1999).In this context, the relative predominance of lineations withshallow and steep plunges in different parts of the mafic–intermediate sheeted domain may be attributed to eitherdeformation-path partitioning into simple shear-dominatedand pure shear-dominated movement components acrossthe shear zone (Lin and Jiang 2001), or superimpositionof the sinistral shear component on vertical emplacement.The latter is consistent with the clockwise rotation of thepluton, and the lack of significant lateral displacement inthe 2D outcrop shape of the pluton, suggesting that thesinistral component during emplacement was minor com-pared with the amount of vertical extension. The amount ofvertical emplacement is constrained by thermobarometricand geochronological data, which indicate a rapid (around2.25 km/million years) exhumation of the pluton betweenca. 287 Ma and ca. 283 Ma. Using the present horizon-tal width of the main plutonic phase (around 4 km) as ameasure for NW–SE extension yields around 20% of E–Wextension across the zone. More structural data are requiredto more rigorously quantify the strain in the pluton.

Ascent/emplacement mechanism

Geochronological data indicate that the Totoltepec plutonwas assembled by at least two magmatic episodes separatedby around 17 million years. According to thermal mod-elling results (e.g. Stimac et al. 2001), this time span ofpluton construction exceeds the thermal lifetime of a largemagma reservoir, indicating that the compositional vari-ability between the main and marginal phase of the plutonis not due to in situ differentiation of a steady-state magmachamber, but represents at least two compositionally dis-tinct magma pulses.

Field evidence indicates that the younger intrusionwas also generated by a series of different magma batchesranging from felsic to mafic in composition. Physicalinteraction between magmatic increments of this mainplutonic phase is indicated by the occurrence of autoliths,microgranular enclaves, and composite dikes. The crys-tallization ages obtained for various phases of the mainplutonic body are the same within error (Yañez et al. 1991;

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Keppie et al. 2004a; Kirsch et al. 2012). However, contactsbetween undated individual sheets, dikes, and enclavesare usually sharp and locally show chilled margins orreaction rims, suggesting that magmatic injections weresufficiently spaced in time for preceding increments to cooland solidify. On the other hand, within the compositionallybanded zone, which on the basis of its field relationships,steepness of banding, and lack of ‘sedimentary’ structures(e.g. Barbey 2009), is interpreted as having originated bymultiple dike injections, feldspar phenocrysts grow acrossdike margins, suggesting that some magmatic incrementswere intruded before the igneous host was completelycrystallized.

These relationships suggest that diking was an impor-tant emplacement mechanism, at least for the highlyheterogeneous mafic–intermediate sheeted zone in thesouthern part of the pluton, where individual narrow,sub-vertical sheets can be traced for tens of metres alongstrike and locally show tapering terminations (e.g. Patersonand Miller 1998; Petford et al. 2000). An emplacementmechanism involving magma migration through propagat-ing dike conduits is consistent with the regional structuralcontext indicating extension oblique to strike–slip faults,which favours the emplacement of plutons as multipleinjections with thin, dike-like geometry (e.g. Pitcher andBerger 1972). Trondhjemitic rocks in the interior of thepluton are more voluminous and more homogeneous incomposition with the marginal mafic–intermediate sheetedzone. This outcrop pattern agrees with thermal modelsthat predict a transitory sheeted-dike phase followed bythe formation of an ephemeral, central magma cham-ber (Hanson and Glazner 1995; Coleman et al. 2004).However, the identification of rare felsic dikes and thepresence of different microstructural types within thisdomain suggest that the trondhjemitic part of the plutonmay also have an episodic emplacement history. Moregenerally, Bartley et al. (2008) point out that intrusivecontacts between magmatic increments may be morenumerous than is apparent in the field because internalcontacts may have become cryptic due to recrystallizationprocesses related to the extended periods of high tem-peratures that accompany slow incremental growth of apluton.

Synthesis/intrusive sequence

Geochronological (Kirsch et al. 2012), combined withthermobarometric, structural, and kinematic data, lead usto propose the following sequence of intrusive events.Early mafic–ultramafic rocks were emplaced at ca. 306 Maalong a crustal lineament (Figure 12A). At ca. 289 Ma,renewed magmatic activity in a transtensional regimewithin the regional magmatic arc led to several successivesheet-like intrusions of dike-fed, mafic–intermediate mag-mas (Figure 12B). Heat provided by mafic–intermediate

magma and regional arc activity (Solari et al. 2001; Elías-Herrera et al. 2005; Rosales-Lagarde et al. 2005; Solariet al. 2010) may have led to crustal melting and theformation of felsic magma at ca. 287 Ma. The stabiliza-tion of partially molten pathways (e.g. Miller and Paterson2001) potentially allowed for these voluminous, more fel-sic batches of melt to become wedged between the oldermafic–intermediate rocks (Figure 12C). Parts of the oldermafic–ultramafic phase may have become entrained in therising felsic melts, physically disaggregated by diking,rotated and dispersed along the margin of the pluton.Entrainment of the mafic–ultramafic phase is consistentwith (1) the presence of inherited zircons of ca. 306 Ma agein ca. 289 Ma rocks from the pluton interior (Kirsch et al.2012), suggesting that these older mafic–ultramafic blockswere partly assimilated; (2) the scattered spatial distribu-tion of the marginal bodies; and (3) the visible evidencethat the marginal bodies are intruded by felsic dikes. Theoccurrence of undated boundinaged folded dikes, foldeddikes, and undeformed dikes suggests that dike intrusionstarted with, and continued after, intrusion of the mainphase. Immediately following intrusion, clockwise rota-tion of the main phase of the pluton into its currentWSW–ENE orientation produced a vertical foliation andhorizontal lineation as well as intrafolial folds in the pluton.Fabric development occurred synchronously with defor-mation over a large temperature range from magmatic tolow-temperature conditions and was spatially diachronous.This is consistent with the continuum from magmatic tosolid-state foliations and the parallelism between theserespective fabrics (e.g. Paterson et al. 1989; Vernon et al.1989; Miller and Paterson 1994; Tribe and D’Lemos 1996).With decreasing temperature, the plutonic body may havebecome increasingly coupled to the country rocks (e.g.Tribe and D’Lemos 1996; Barros et al. 2001), which ledto the overprinting of igneous structures by solid-statefabrics. Deformation was concentrated in zones of compe-tency contrast, i.e. the mafic–intermediate sheeted domainnear the pluton margin, where it produced discrete mylonitezones (Figure 3).

Structural evidence within these mylonite zones, suchas the local development of tectonic down-dip lineationswith kinematic indicators of top-to-SSE transport, sug-gests that in the last stages of the emplacement history,thrusting may have developed locally within the regionaltranstensional environment. Thrusting may be associatedwith a decrease of slip along the San Jerónimo fault andresulting transfer of dextral displacement onto the Caltepecfault (Figure 12C). This transfer may have led to (1) termi-nation of magma supply by truncating the magma conduit,although regional magmatism occurred elsewhere in thearc and (2) substantial (around 2.25 km/million years)uplift of the pluton between ca. 287 Ma and ca. 283 Ma asinferred by Al-in-hornblende thermobarometry combinedwith 40Ar/39Ar geochronology.

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Regional significance

Transtensional deformation is a common feature ofmagmatic arcs, resulting from oblique convergence andstrain partitioning at plate margins (e.g. Teyssier et al.1995; Dewey 2002). The southern Mexican portion of theextensive Carboniferous–Permian continental arc exhibitsa well-pronounced arc-parallel structure of N–S ori-ented, dextral strike–slip faulting and synkinematic plutonsemplaced along these faults. The Totoltepec pluton is inter-preted to have been emplaced along a SW–NE extensionalfault that was synchronous with the dextral shear alongN–S fault zones, and is thus an example of arc-transversestrike–slip tectonics in the southern Mexican arc. Thegeochemistry of the Totoltepec pluton, which is isotopi-cally more primitive than coeval igneous rocks elsewherein the regional magmatic arc (Kirsch et al. 2012), andthe intrusive history involving the incremental injectionof several sheet-like magma batches into mid-crustal lev-els during transtensional deformation, followed by localthrusting resulting in uplift and exhumation, may be char-acteristic of pluton emplacement in such a specializedtectonic environment and may be utilized in identifyingsimilar tectonic settings within continental arcs.

AcknowledgementsMK thanks Maria Helbig for invaluable assistance in the field andsupport throughout the writing process. MK also acknowledgesthe helpful discussions with Uwe Kroner, Luigi Solari, FernandoOrtega-Gutiérrez, Harald Böhnel, Axel Renno, and Ángel F. NietoSamaniego. Carlos Linares provided technical assistance duringmicroprobe work at the Laboratorio Universitario de Petrología,UNAM. This study was funded by CONACyT and PAPIITgrants to JDK, and by NSERC discovery grants to JBM andJKWL.

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4E V E N T O S D E L PA L E O Z O I C O TA R D Í O H A S TA E LM E S O Z O I C O T E M P R A N O E N L A P E R I F E R I A D EPA N G E A

Guía de la excursión geológica: Keppie, J.D., Galaz-Escanilla, G., Helbig,M., y Kirsch, M. (2012). Late Paleozoic–Early Mesozoic of the Acatlán andAyú complexes, southern Mexico: events on the periphery of Pangæa syn-chronous with amalgamation and breakup. GSA Cordilleran Section, 108thAnnual Meeting, Field Trip 1, 31 March – 4 April, Geological Society ofAmerica, IGCP Project 597, 17 p.


J. Duncan Keppie: líder y organizador de la excursión; concepción ydiseño de la guía de excursión.

Gonzalo Galaz-Escanilla: co-líder de la excursión; descripción de lasparadas 3-1 a 3-7; redacción de las figuras 7 y 8.

Maria Helbig: co-líder de la excursión; descripción de las paradas 1-1a 1-6; redacción de las figuras 3, 4 y 5.

Moritz Kirsch: co-líder de la excursión; descripción de las paradas 2-1 a 2-8; elaboración de la figura 6; con respecto a los nuevos datosde una unidad metamórfica del Misisipiense en la parte oriental delárea de estudio: trabajo de campo incluyendo mapeo y muestreo parala geocronología 40Ar/39Ar; análisis geoquímico e isotópico; adquisi-ción de datos de los análisis 40Ar/39Ar incluyendo la separación deminerales, el análisis y la interpretación de datos.

58

GSA Cordilleran Section, 108th Annual MeetingField Trip 1

31 March–4 April 2012

Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle

International Geological Correlation Program Project #597: Late Paleozoic–Early Mesozoic of the Acatlán and Ayu complexes, southern Mexico: events on the periphery of Pangæa synchronous with amalgamation and breakup

J. Duncan KeppieGonzalo Galaz-Escanilla

Departamento de Geología Regional, Insituto de Geología, Universidad Nacional Autónoma de México, 04510 Mexico, D.F.Maria HelbigMortiz Kirsch

Centro de Geociencias, Universidad Nacional Autónoma de México, Campus Juriquilla, 76230 Querétaro, QRO, Mexico

INTRODUCTION

There is widespread acceptance that between 300 and 200 million years ago, all of the Earth’s continental land masses were assembled into a giant supercontinent, Pan-gæa, surrounded by a superocean, Panthalassa. However, different confi gurations have been proposed, e.g., Pangæa A1, A2, B, and C (Fig. 1A). Reconstructions based on Mexican paleomagnetic data have been used to support both A and B models:

(a) PANGEA-A. A Permo-Triassic Pangea-A reconstruction where southern Mexico lies approximately in its present location relative to North America (Fang et al., 1989, Alva-Valdivia et al., 2002);

(b) PANGEA-B. A Pangea-B reconstruction placing southern Mexico off eastern Canada during the Jurassic (Fig. 1B: Böhnel, 1999).

There are also Middle American variants of the Pangea-A reconstruction:(i) southwestern Mexico is placed either along the western margin of Pan-

gea (Fig. 1C and 1D: Keppie, 2004, Keppie et al., 2008, 2010), or within Pangea between the Maya terrane and southern USA (Fig. 1E: Talavera-Mendoza et al.,2005, Vega-Granillo et al., 2007, 2009);

(ii) the Yucatan block is placed either within Pangea along the southern mar-gin of USA (Fig. 1F: Pindell and Dewey, 1982), or on the western margin of Pangea during the mid-late Permian migrating into the Gulf of Mexico by the Middle Jurassic (Steiner, 2005);

(iii) the Chortis block has generally been placed off southwestern Mexico on the western marin of Pangea (Fig. 1E)(e.g., Pindell and Dewey, 1982), or within the within Pangea along the eastern margin of Mexico (Fig. 1G: Keppie and Keppie, in review).

On this fi eld trip we will examine the evidence for subduction-related tectonics during the Pennsylvanian-Jurassic in the Ayu and Acatlán complexes, which suggests proximity to an ocean that is more consistent with the Pangea-A model (Fig. 2).

1

AB

C350–330 Ma 300–270 Ma

D

E

FG

Figure 1. Reconstructions of Pangea by various authors.

2 Keppie et al.

Figure 2. (A) Terranes of Middle America (after Keppie, 2004); (B) Ages od units in the Acatlán Complex; (C) Map of the Acatlán Complex (modifi ed after Keppie et al., 2010) showing the fi eld trip route.

Amalgamation and Breakup of Pangæa: the type example of the supercontinent Cycle 3

DAY 1Maria Helbig and J. Duncan Keppie

The Triassic-Jurassic Ayú Complex Southern Mexico: Evidence for Deposition on the Proximal Margin of a Backarc Basin, Underthrusting and Extrusion into the Acatlán Complex during the Breakup of Pangea-A

Helbig, M, Keppie, J.D., Murphy, J.B., and Solari, L.A., in press. U-Pb geochonological constraints on the Triassic–Jurassic Ayú Complex southern Mexico: derivation from the western margin of Pangea: Gondwana Research.

ABSTRACT

Rocks of the newly designated Ayú Complex are located in the eastern Mixteca terrane (southern Mexico), and comprise polyphase-deformed turbiditic rocks (Chazumba Lithodeme) that are intercalated with boudinaged ortho-amphibolites. In the south, the metasedimentary sequence is affected by partial melting and grades into the ~171 Ma Magdalena Migmatite. Migmatitzation was accompanied by 171–168 Ma granitoid minor intrusions and pegmatites with inherited zircon popula-tions of ca. 260–290, 320–360, 420–480, 880–990, and 1080–1250 Ma that are also found in the Chazumba Lithodeme. Detrital U/Pb zircon ages from the migmatized and unmigma-tized Chazumba Lithodeme yielded clusters of ca. 297, 266, 250, 214, 198, and 192 Ma, suggesting Upper Triassic—Lower Jurassic deposition. The MORB tholeiitic geochemistry of the amphibolites within the Chazumba Lithodeme indicates a back-arc environment with sedimentation occurring along the inboard rifted passive margin, the Upper Triassic–Lower Jurassic detrital zircons being derived from a contemporane-ous, outboard magmatic arc. These characteristics suggest cor-relation with the lens-shaped Central terrane typifi ed by the Potosi turbiditic fan in the rift-passive margin of Pangea that is absent west of the Mixteca terrane. The presence of this arc requires deposition adjacent to a subducting ocean and thus supports a Pangea-A reconstruction. Early Jurassic fl attening of the subduction zone is inferred to have led telescoping of the Triassic–Early Jurassic back arc basin, during which the Chazumba Lithodeme was thrust beneath the Pangean margin where it was metamorphosed under amphibolite facies meta-morphic conditions. It is further inferred that Middle-Upper Jurassic steepening of the subducting zone led to tectonic exhumation of the Chazumba Lithodeme by normal faulting along the reactivated Providencia Shear Zone. Deposition, underthrusting and exhumation of the Chazumba Lithodeme are synchronous with the breakup of Pangea and the opening of the Gulf of Mexico.

STOP 1-1 (W97.78834, N17.9387426: Fig. 3)Location: Road between Sta. María Ayú and Ahuehuetitlán, riverbed of Río La Peña.

Micaceous schists and garnet-biotite gneisses are inter-calated with boudinaged amphibolites, that underwent migmati-zation at ~171 Ma (leucosome dated by Keppie et al., 2004) and formed a mappable unit, called the Magdalena Migmatite. This tectonothermal event was accompanied by syntectonic intrusion of granitic, granodioritic and dioritic dikes and sheets (Yañez et al., 1991). A granite dike that cuts the paleosome yielded only one igneous zircon of 171 ± 4 (Middle Jurassic), whereas the rest of the dated grains are inherited zircons. Two paleosome samples of the Magdalena Migmatite yielded youngest detrital zircons of ~198 Ma (Early Jurassic) and 214 Ma (Late Triassic ), respectively. Amphibolites were previously dated by Keppie et al. (2004) and showed 40Ar/39Ar cooling ages of 150 ± 2 Ma for biotite and 136 ± 2 for hornblende, suggesting rapid exhuma-tion. Geochemically, amphibolites sampled across the Ayú Com-plex are MORB-like, rift-related tholeiites (Helbig et al., 2010). The majority of the ortho-amphibolites have jagged NMORB-normalized REE patterns that imply contamination either by a crustal and/or subduction component and suggest a formation in a back-arc basin.

STOP 1-2 (W97.807052°°, N17.9987634°°: Fig. 3)Location: short road stop east of Tetaltepec.

Structural relationships in the Magdalena Migmatite: Large scale, close to open, upright to gently inclined parasitic fold (F

4)

that folds the leucosome and boudinaged S3-parallel granite

sheets.

STOP 1-3 (W97.830789°°, N18.036058°°: Fig. 3)Location: Riverbed, south of San Miguel Ixtápan.

Partially molten, and strongly deformed metasedimentary rocks that are intruded by granodiorites and pegmatites. Xeno-liths are probably the metasedimentary host rock and show in-ternal foliation as well as partial melting of the fertile domains. 40Ar/39Ar dating of a pegmatite and a granitic sheet yielded 167 ± 2 Ma for muscovite, and 155 ± 5 Ma for biotite (Keppie et al., 2004).

STOP 1-4 (W97.832239°°,N18.0421378°°: Fig. 3)Location: Road section, south of San Miguel Ixtapan.

Outcrop exhibits a dike that cuts across the micaceous schists and feeds a granite sheet. The emplacement of the granite sheet is parallel to the main foliation, infl ating the surrounding metapelitic host rock. The dike continues its way into the hang-ing metasedimentary host rock. Where in the contact with the host rock, the dike is overprinted by the same fabric as in the metasedimentary rocks. The rock is affected by later brittle nor-mal block faulting. The fabric-parallel granite sheets show sharp contacts with the metapelites and exhibit minor pinch-and-swell structures and a distinct tectono-magmatic foliation at their mar-gins suggesting stress-related emplacement.

4 Keppie et al.

X

X –97°54′

18°1

2′18

°06′

18°0

0′

–97°48′ –97°42′

X′

X′

Figure 3. Geological map and section of the Totoltepec-Ayu area, southern Mexico showing fi eld trip stops (modifi ed after Helbig et al., in press).


STOP 1-5 (W97.828639°°, N18.0526397°°: Fig. 4)Location: Foothills of the Cerro de La Peña (Cenozoic volcanic plug), north of Tejepillo; San Miguel Ixtapan road exit to Tultitlán.

Micaceous schists intercalated with minor quartzites are in-truded by granites, leucogranitic and aplitic dikes. A granite dike cuts a tight, recumbent E-trending F

3 fold in the metasedimentary

host rock. Small leucogranite veins that probably originate from the dike are parallel to the folded S

2 fabric. These relationships

suggest that the intrusion was syn- to late-tectonic with respect to F

3. The granite is characterized by zircon inheritance and the

crystallization age is inferred from the youngest grain with an age of 168 Ma. U-Pb detrital zircon analyses of a psammitic and a pelitic mica schist yielded maximum depositional ages of ~269 Ma and ~263 Ma (Middle Permian), respectively.

In the hanging wall, the mafi c-ultramafi c Tepejillo lens lies structurally as a nappe above the Chazumba Lithodeme (Keppie et al., 2004) and consists of four bodies that crop out along the foothills of Cenozoic volcanic plug (C. La Peña). The Tepejillo lens comprises coarse crystalline ultramafi c (mainly dunite) to gabbroic rocks that are cut by diabase dikes. Geochemically, they are interpreted as part of a cumulatic body intruded into the lower continental crust (Keppie et al., 2004). The contact be-tween the metasedimentary rocks of the Chazumba Lithodeme and the Tepejillo lens has been mapped as a folded thrust (Kep-pie et al., 2004). The Tultitán lens, 4 km to the northeast of the Tepejillo lens, consists of massive amphibolite and a core of metamorphosed norite. One concordant U-Pb LA-ICP-MS analysis of a prismatic tip of a euhedral zircon from a metanorite yielded an age of 174 ± 1 Ma, which is interpreted as age of intrusion for both lens (Keppie et al., 2004). Biotite from a gab-broic dike of the Tepejillo lens yielded a 40Ar/39Ar cooling age of 166 ± 2 Ma, whereas muscovite from a granite dike yielded a 40Ar/39Ar age of 161 ± 2 Ma (Keppie et al., 2004), suggesting excess argon in the biotite. Lower power increments of Late Cre-taceous to Tertiary age can be observed in almost all 40Ar/39Ar analyses, implying that the Ayú Complex was affected by a later deformational event.

STOP 1-6 (W97.899842°°, N18.113004°°: Fig. 5)Location: road section near the town La Providencia, on the road between Petlalcingo and Tonhuixtla.

Reactivation of a Triassic S-vergent thrust fault as a lis-tric normal fault in the Middle-Late Jurassic. The Providencia shear zone forms a major structural feature between rocks of the Acatlán Complex (Tecomate Formation and Cosoltepec Forma-tion) and the Ayú Complex and comprises weathered mylonites.

A micaceous metapsammite just south of the shear zone yielded only seventeen concordant analyses. Relatively narrow age spectra ranging from 194 to 339 Ma were obtained with the two youngest grains (190 ± 4, 193 ± 4 Ma) forming a mean of 192 ± 19 Ma (Early Jurassic). To the north of the shear zone, a

mylonitic phyllite yielded a youngest detrital zircon age of 314 ± 4 Ma, which lies within the error of the mean of the three young-est grains with an age of 321 ± 30 Ma (Late Mississippian/Early Pennsylvanian). A graphite- and feldspar-bearing mylonitic metasedimentary rock, yielded two youngest detrital zircon ages of 281 ± 4 Ma and 295 ± 8 Ma with a mean age of 284 ± 71 Ma (Early Permian).

The presence of a major shear zone (Providencia Shear Zone) that separates the Acatlán Complex from the Ayú Complex was previously mapped as a thrust based on s-c fabrics in the hang-ing block (Malone et al., 2002; Keppie et al., 2004). However, 40Ar/39Ar cooling ages for amphibole of an amphibolite lens and muscovite from micaceous schists, north of the shearzone yielded cooling ages of ~214 Ma and ~224 Ma, respectively (Keppie et al., 2004). These fabrics are Late Triassic, and thus developed before or during the deposition of the Chazumba Lithodeme. It is envisaged that this Triassic shear zone was reactivated during or after the Middle Jurassic as a listric normal fault and formed the upper boundary of the exhuming Chazumba Lithodeme.

DAY 2Moritz Kirsch and J. Duncan Keppie

Lower Permo-Carboniferous Arc Magmatism and Sedimentation on the Margin of Pangea-A

Kirsch, M., Keppie, J.D., Murphy, J.B., and Solari, L.A. in press. Permian-Carboniferous arc magmatism and basin evolution along the western margin of Pangea: geochemical and geochronological evidence from the eastern Acatlán Complex, southern Mexico: GSA Bulletin.

ABSTRACT

The Late Paleozoic evolution of Mexico records part of a continental arc that extends along the western margin of Pan-gea from western USA to the northern Andes. In the Acatlán Complex of southern Mexico, an arc assemblage consisting of a Permo-Carboniferous intrusion (Totoltepec pluton) and Permian sedimentary rocks (Tecomate Formation) offers a rare opportunity to examine events along the periphery of Pangea at the critical stage of fi nal amalgamation.

The Totoltepec pluton ranges in composition from horn-blendite and hornblende gabbro through diorite to tonalite, trondhjemite, granodiorite and monzo-granite. U-Pb LA-ICP-MS zircon analyses yield concordant ages of 306 ± 2 Ma in minor marginal mafi c to ultramafi c rocks and 289 ± 2 Ma for the main, more voluminous mafi c to felsic intrusion. Major and trace element geochemistry of the Totoltepec rocks exhibit a tholeiitic to calc-alkaline character, high LILE/HFSE and fl at REE patterns, which is typical of arc-related magmas. The pre-cursor gabbroic rocks display εNd(t) values ranging from +1.3 to +3.3 (t = 306 Ma), whereas rocks from the main body of the pluton have εNd(t) values between −0.8 and +2.6 (t = 289 Ma).

6 Keppie et al.

B

A

B′

A′

B′B

A′

A

Figure 4. Stop 1-5: geological map, age data, and section of the Tepejillo ultramafi c lens (after Keppie et al., 2004).


14

00m

1 40

0

m

1450

m

1450m

1500

m

–97°

54′3

0″

18°06′30″18°07′00″18°07′30″

–97°

54′0

0″–9

7°53

′30″

Figu

re 5

. Sto

p 1-

6: g

eolo

gica

l map

and

geo

chro

nolo

gy o

f th

e L

a Pr

ovid

enci

a sh

ear

zone

(m

odifi

ed a

fter

Hel

big

et a

l., in

pre

ss)

8 Keppie et al.

All of the samples are variably affected by wall rock assimi-lation, mixing and fractionation processes, but are more juve-nile compared to contemporaneous arc-related igneous rocks in southern Mexico, suggesting the pluton was emplaced into thinner crust in a less mature part of the arc or along a fault that acted as a conduit for mantle-derived melts.

The Tecomate Formation consists of low-grade, poorly sorted, compositionally immature and largely unweathered metapsammites and metapelites. Several factors indicate deri-vation from the Permo-Carboniferous arc: (i) an arc-related geochemistry, (ii) εNd(t) values ranging from −5.7 to +0.3 (t = 280 Ma) that overlap those of the Totoltepec pluton, and (iii) detrital zircons with predominantly Permo-Carboniferous ages. The depositional age of the Tecomate Formation is con-strained between the youngest detrital zircon population (ca. 280 Ma) and a published Ar/Ar age of 263 ± 3 Ma from the Teco-mate Formation in the adjacent area. However, a metapsammite sample from the base of the Tecomate Formation yielded only Proterozoic zircons, indicating that deposition may have initi-ated earlier. Possible correlative sequences that may have been deposited in a similar peri-arc setting include the latest Pennsyl-vanian to Middle Permian Tecomate Formation type area, the latest Devonian to Lower Permian Patlanoaya Group, the Early to Middle Permian Tuzancoa Formation, the Middle Permian Los Hornos Formation, and the Olinalá Formation of Middle to Upper Permian age.

Kirsch, M., Keppie, J.D., Murphy, J.B. and Lee, J.K.W., in preparation. Structural history of the arc-related Totoltepec pluton, Acatlán Complex, southern Mexico: Syntectonic emplacement along a mid-crustal transpressional shear zone.

ABSTRACT

The 306–289 Ma tholeiitic to calc-alkaline Totoltepec plu-ton in the eastern Acatlán Complex, southern Mexico, is part of a Permo-Carboniferous continental magmatic arc along the western margin of Pangea. The pluton is a well-exposed, com-posite, felsic to ultramafi c intrusive suite containing a conspicu-ous mesoscopic fabric, making it an ideal place to study the relationship between tectonic processes in magmatic arcs and pluton emplacement.

We use an integrated approach combining fi eld observa-tions, structural measurements, analysis of micro-fabrics, as well as Al-in-hornblende thermobarometry and 40Ar/39Ar thermo-chronology to decipher the structural evolution of the Totolte-pec pluton. The data suggest that the pluton was emplaced in ~20 km depth and rapidly uplifted to allow it to cool to ~400 °C within 6 ± 2 Ma. The elongate pluton shape, parallel, decreas-ing temperature fabrics, similar crystallization and deformation ages and the rapid exhumation of the pluton speak for a syn-tectonic emplacement. A subvertical, fanning foliation and sub-horizontal to subvertical lineations as well as the presence of internal, margin-parallel sinistral shear zones suggest emplace-

ment along a transpressional fault. Hornblende-bearing diorites and tonalites within the low to medium-temperature solid-state domain in the southern part of the pluton exhibit a composi-tional and textural banding that is interpreted to have formed by a combination of steep igneous layering, layer-parallel dike injection and melt-enhanced deformation.

Although we were unable to document any regional-scale structures that may have controlled its intrusion, the timing and emplacement mechanism of the Totoltepec pluton is similar to that reported for syn-tectonic Late Carboniferous to Early Permian plutons along the Caltepec Fault zone that separates the Mixteca terrane from the Oaxacan Complex. Strike-slip tec-tonism along this fault may be associated with oblique subduc-tion of the paleo-Pacifi c beneath the western margin of Pangea.

STOP 2-1. (W97.88385°°, N18.214033°°: Fig. 6)

Transpressional shear zone within the Totoltepec pluton near Santo Domingo Tonahuixtla. Here, strongly banded and foliated hornblende-bearing diorite and tonalite is intruded by felsic and mafi c dikes at low angles to the WSW-striking planar fabric. Hornblende fi sh and asymmetrically boudinaged dikes consis-tently display sinistral kinematics. The crystallization age of the mafi c rocks give an age of 289 ± 2 Ma (Keppie et al., 2004), whereas foliation-parallel muscovite in trondhjemite (1 km due SE) yield a 40Ar/39Ar age of 283 ± 1 Ma.

STOP 2-2 (W97.890711°°, N18.208455°°: Fig. 6)

Aplitic dikes intruding megacrystic hornblende diorite/tonalite north of Santo Domingo Tonahuixtla. Dikes are mostly foliation-parallel, but are locally observed to cut the foliation at low angles. Some dikes contain an internal tectono-magmatic fabric parallel to the dike wall and dike-host contacts are sharp to irregular suggesting dike emplacement was syntectonic and occurred prior to complete crystallization of the host. The mega-crystic hornblende-bearing rocks are laterally traceable. Whereas at this location, lineations are weakly developed or subhori zontal with sinistral kinematics, further east, between the villages of Tonahuixtla and Totoltepec, the rocks possess a strong down-dip mineral lineation and sigma-shaped tails on hornblende porphyro-blasts suggest thrusting toward the south.

STOP 2-3 (W97.874964°°, N18.207481°°: Fig. 6)

Compositional/ textural banding in hornblende-bearing tonal-ites east of Tonahuixtla. Rocks at this stop have a mylonitic fab-ric and contain a conspicuous banding defi ned by a more or less rhythmic variation in grain size and modal proportions of feldspar and hornblende. Locally, these rocks exhibit gentle, ca. 2 m wave-length, fold-like structures resembling trough-banding characteris-tic of layered intrusions. These features indicate that the banding may have a complex, multi-stage history of development, involv-ing magma chamber, injection as well as tectonic processes.


SubalkalineBasalt

Andesite

RhyodaciteDacite

Rhyolite

BasaniteTrachybasaniteNephelinite

Phonolite

Trachyte

Com/Pan

TrAn

Alkali Basalt

SiO

[wt %

]

40

50

60

70

80

Zr/TiO

0.001 0.01 0.1 1

quartz-rich granitoidtrondhjemiteplag-rich cumulatetonalite

289

Ma

306

Ma

quartz dioritehornblende diorite

hornblende gabbrohornblendite

C

2-8

2-7

2-6

2-52-4

2-32-2

2-1

Chichihualtepec


Santo Domingo Tonahuíxtla

San Jerónimo de Xayacatlán

Santo Domingo Tianguistengo

97°48′0″W97°50′0″W97°52′0″W97°54′0″W

18°16′0″N

18°14′0″N

18°12′0″N

0 1 20.5km

Scale 1:65,000

CretaceousJurassicTecomate FormationAmarillo UnitSalada Unit

Totoltepec Pluton

granodiorite, monzo-granitetrondhjemitediorite, tonalite, felsic and mafic dikeshornblende gabbro, hornblendite

ContactContact, inferredStrike-slip FaultNormalfaultThrustfault

Hbl Gabbro306 ± 2 Ma

2σ error ellipses

290300310320

19.2 19.6 20.0 20.4 20.8 21.2 21.6 22.0

0.064

0.060

0.056

0.052

0.048

207 P

b/20

6 Pb

238U/206Pb

TuffZirc 206Pb/238U age306 –1 +2 Ma

(95.7% conf, n=25)290

300

310

320

Qtz Diorite289 ± 2 Ma

2σ error ellipses

280290300310320

19 20 21 22 23

0.062

0.058

0.054

0.050

0.046

207 P

b/20

6 Pb

238U/206Pb

TuffZirc 206Pb/238U age289 +1 –2 Ma

(94.8% conf, n=22)280

290

300

310

TT-81Metapsammite

TT-82Metapelite

TEC-10 Granite cobble

Metacongl.(Keppie et al., 2004)

270

280

290

300

310

320

330

340

350

Ea

rly

Pe

rmia

nP

en

nsy

lva

nia

nM

issi

ssip

pia

n

CA

RB

ON

IFE

RO

US

PE

RM

IAN

Totoltepec Pluton~289 Ma Qz Diorite

Totoltepec Pluton~306 Hbl Gabbro

TT-612 Metapsammite

TT-615Granite veinlet

(detrital zircons)

Frequency

0 25 50

Rel. Prob

n = 162

B

t [Ga]

D DepletedMantle

Nd(t

)

10

5

0

5

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

Totoltepec pluton

Tonahuixtla Member

Asis amphibolites

Tecomate Fm. type area

Oaxacan Complex

metapelitemetapsammitemetaarkose

A

Figure 6. Stops 2-1 to 2-8: geological map of the Totoltepec pluton (after Kirsch et al., in press) showing fi eld trip stops.

10 Keppie et al.

STOP 2-4 (W97.86816°°, N18.218361°°: Fig. 6)

Hornblende gabbro at the northern margin of the Totoltepec pluton in contact with Jurassic redbeds. This outcrop is located in one of three ca. 0.2–0.6 km2, fault-bounded, precursor (306 ± 2 Ma) gabbroic phase, which is distributed along the northern and north-eastern margin of the pluton. Locally, these rocks are intruded by intensely deformed felsic dikes. To the north, the pluton is unconformably overlain by redbeds of inferred Jurassic age, which sit steeply against the pluton buttress due to a subse-quent period of normal faulting.

STOP 2-5 (W97.851633°°, N18.2581°°: Fig. 6)

Amarillo Unit (new name), SE of Santo Domingo Tian-guistengo. This unit is characterized by medium- to high-grade metasedimentary rocks locally intruded by amphibolite dikes. Youngest detrital zircons from a garnet schist sample indicate a maximum depositional age of 337 ± 4 Ma (Mississippian). The amphibolite dikes exhibit a MORB-like geochemistry with εNd(i) values of +5.2 to +7.6 and TDM model ages between 333 and 433 Ma. These features are very similar to those documented in the Salada Unit (Morales-Gámez et al., 2008), on the western side of the Totoltepec pluton.

STOP 2-6 (W97.776016°°, N18.257016°°: Fig. 6)

Thrust contact between the Totoltepec pluton and the Teco-mate Formation metasedimentary rocks. The exposed contact is a low-angle brittle-ductile thrust. At another location, this thrust is mylonitic and yielded a Middle Triassic 40Ar/39Ar age on mus-covite. The contact is furthermore associated with a Fe-P-REE deposit containing the mineral association magnetite, apatite, barite, chlorite, quartz, chalcopyrite, and a cerium mineral. The mineralization is confi ned to two discrete, elongated bodies of ~100 m length coinciding with strong aeromagnetic anomalies.

STOP 2-7 (W97.794857°°, N18.262697°°: Fig. 6)

S-C fabrics in the Tecomate Formation ~1 km south of the margin of the Totoltepec pluton, indicating top-to-the-south thrusting. Thermochronological data from this area as well as other samples from the Tecomate Formation and Amarillo Unit reveal a regionally significant tectonothermal event of mid-Triassic age.

STOP 2-8 (W97.892266°°, N18.190066°°: Fig. 6)

Pebble metaconglomerates of the Tecomate Formation near Chichihualtepec. The pebbles from this outcrop, which are petro-graphically similar to the Totoltepec pluton trondhjemite, yielded zircons with ages between 320 and 264 Ma (Keppie et al., 2004). Morales-Gámez et al. (2009) conducted strain measurements in these rocks, documenting prolate spheroids typical of transten-

sional deformation. Rotated pebbles with asymmetric tails show top-to-the-south shear, which is consistent with other kinematic indicators in this area.

DAY 3Gonzalo Galaz-Escanilla and J. Duncan Keppie

A High Pressure Zone within the Acatlán Complex: Uppermost Devonian: Lower Carboniferous Subduction and Extrusion under Extension during the Initial Stages of Pangea Amalgamation

Center of High Pressure Zone

Keppie, J.D., Nance, R.D., Dostal, J., Lee, J.K.W., and Ortega-Rivera, A. 2011 Constraints on the subduction erosion/extrusion cycle in the Paleozoic Acatlán Complex of southern Mexico: geochemistry and geochronology of the type Piaxtla Suite. Gondwana Research, doi:10.1016/j.gr.2011.07.020

ABSTRACT

The type high-pressure (HP) Piaxtla Suite in the Acatlán Complex of southern Mexico consists of retrogressed eclogite (amphibolite), megacrystic granitoids and high-grade meta-sedimentary rocks. Exhumation of these HP rocks has recently been interpreted as the result of extrusion into the upper plate, rather than by return fl ow up the subduction zone. Geochemical analyses of the retrograde eclogites indicate that they have a rift tholeiitic-transitional alkalic composition. These are closely associated with a megacrystic meta-granitoid that has yielded an intrusive age of 452 ± 6 Ma (concordant U-Pb zircon analy-ses) with inherited zircon populations at ca. 800–950 Ma and 1000–1200 Ma derived from the underlying basement, prob-ably the Oaxacan Complex which borders the Acatlán Complex to the east. The bimodal nature of these igneous rocks and their close association with continentally-derived sedimentary rocks is similar to most HP rocks in the Acatlán Complex derived from a rifted passive margin. The youngest detrital zircon population in a metapsammite sample yielded an U-Pb age of 365 ± 15 Ma with older analyses distributed along a chord with an upper intercept of 1287 ± 29 Ma. The ca. 365 Ma age pro-vides a maximum age for the time of deposition of this sample. 40Ar/39Ar ages from the retrogressed eclogites provided horn-blende plateau ages of 342 ± 2 Ma and 344 ± 2 Ma, whereas muscovite from the granitoid and metapsammite yielded 334 ± 2 Ma plateau ages. These data constrain the subduction erosion-extrusion cycle to ≤35 my during which the rocks were taken to a depth of ca. 40 km at a rate of 2.7 km/my and back to the surface at 2.4 km/my. Such exhumation rates are slower than those in continent-continent collision zones, but similar to those in the Iberia-Czech Variscan belt where tectonic interpretation also suggests extrusion into the upper plate.


Western Boundary of High Pressure Zone: A High-Pressure Folded Klippe Explaced during the Lower Carboniferous at TehuitzingoGalaz E., Gonzalo, et al., in press. A high-pressure folded klippe at Tehuizingo on the western margin of an extrusion zone, Acatlán Complex, southern Mexico

ABSTRACT

The Acatlán Complex is divided into two blocks of low-grade metamorphic rocks by a central belt of high-pressure (HP) rocks, which at Tehuitzingo is composed of metabasites, serpen-tinite, granite and mica schist. 580–430 Ma detrital zircon ages indicate that these rocks were deposited adjacent or very close to the Gondwana supercontinent during the Early Paleozoic and are more consistent with a development on the southern margin of the Rheic Ocean rather than the Iapetus Ocean. These rocks were then removed by a subduction-erosion to depths of ~50km, reaching a metamorphic peak of ~16 kbar and 750 °C (eclogite facies). The HP rocks underwent rapid extrusion during a major Late Devonian-Pennsylvanian tectonothermal event indicated by 40Ar/39Ar analyses, which yielded ages of ~373 Ma (hornblende in metabasite) and of 328–317 Ma (muscovite in granite, mica schist and metabasite) that indicate cooling through ~570 °C and ~350 °C respectively, indicating a very high cooling rate of ~4.9–3.9 °C/m.y. During the extrusion process these rocks were affected by retrogression to amphibolite-epidote and green schist facies, and fi nally emplaced as a klippe on a greenschist facies psammite-pelite unit that constitutes the western block of the Acatlán Complex. Petrologic, deformational and geothermo-barometric data suggest that west and east blocks belong to the same terrane, indicating that a subduction-erosion process and subsequent extrusion is more consistent with the genesis of the HP central belt than a collisional event as has been proposed. The P-T-t pattern of these HP rocks is consistent with subduc-tion environments reported elsewhere in the world and suggests a serpentinite extrusion channel on the western margin of Pangea.

Eastern Boundary of High Pressure Zone: A Listric Normal Shear Zone Synchronous with Deposition of the Uppermost Devonian–Lower Permian Patlanoaya Group

Keppie, J.D., Nance, R.D., Ramos-Arias, M.A., Lee, J.K.W., Dostal, J., Ortega-Rivera, AQ., and Murphy, J.B. 2010. Late Paleozoic subduction and exhumation of Cambro-Ordovician passive margin and arc rocks in the northern Acatlán Complex, southern Mexico: geochronological constraints. Tectonophysics, v. 495, p. 213–229.

ABSTRACT

The origin and age of high pressure (HP) rocks is crucial for paleogeographic reconstruction because they either mark an oceanic suture or an extrusion zone within the upper plate. HP

rocks in the San Miguel Las Minas area in the northern part of the complex has been inferred to be of early Paleozoic age and to mark oceanic sutures. However, blueschists in the northern part of the Acatlán Complex in southern Mexico have yielded Mis-sissippian 40Ar/39Ar plateau ages of 344 ± 5 Ma for glaucophane and 338 ± 3 Ma and 337 ± 2 Ma for muscovite. These ages are slightly younger than recently published ages: a U-Pb zircon age of 353 ± 1 Ma from associated eclogite, and a 347 ± 3 Ma muscovite age from the tectonically overlying, greenschist facies Las Minas Unit. Taken together, these data indicate rapid cooling between 700° and 340°C in ca. 17 Myr. On the other hand, asso-ciated Ordovician Anacahuite Amphibolite cooled through ca. 500°C at 299 ± 6 Ma (40Ar/39Ar on hornblende) suggesting a sec-ond, Permian period of exhumation. Protoliths of the high grade rocks include Cambrian-Ordovician, rift-passive margin, psam-mites, pelites, and tholeiitic dykes, an Ordovician mafi c intrusion (Anacahuite Amphibolite dated at 470 ± 10 Ma: U-Pb zircon) and megacrystic granite (dated at 492 ± 12 Ma: U-Pb zircon), and arc-related mafi c rocks of unknown age. These upper plate rocks are inferred to have been removed by subduction erosion and taken to depths between 35 and 55 km where they underwent blueschist-eclogite facies metamorphism. This was followed by rapid extrusion along a channel bounded by an easterly dipping, Mississippian, listric normal shear zone, and a thrust modifi ed by a Permian dextral fault. Rocks above and below the extrusion zone are mainly Cambro-Ordovician rift-passive margin units, but a small vestige of the arc preserved as dikes cutting rocks lying unconformably beneath the fossiliferous latest Devonian-Lower Permian Patlanoaya Group. Since faunal data indicate that Pangea had amalgamated by the Mississippian, at which time the Acatlán Complex lay 1500–2000 km south of the Ouachita col-lisional orogen between Gondwana and Laurentia, it is inferred that subduction and extrusion of the high pressure rocks occurred on the active western margin of Pangea.

Ramos-Arias, M., Keppie, J.D., Ortega-Rivera, A., and Lee, J.W.K. 2008. Extensional late Paleozoic deformation on the western margin of Pangea, Patlanoaya area, Acatlán Complex, southern Mexico. Tectonophysics, v. 448, p. 60–76.

ABSTRACT

New mapping in the northern part of the Paleozoic Acatlán Complex (Patlanoaya area) records several ductile shear zones and brittle faults with normal kinematics (previously thought to be thrusts). These movement zones separate a variety of units that pass structurally upwards from: (i) blueschist-eclogitic meta-morphic rocks (Piaxtla Suite) and mylonitic megacrystic granites (Columpio del Diablo granite ≡ Ordovician granites elsewhere in the complex); (ii) a gently E-dipping, listric, normal shear zone with top to the east kinematic indicators that formed under upper greenschist to lower amphibolite conditions; (iii) the Middle-Upper Ordovician Las Minas quartzite (upper greenschist facies psammites with minor interbedded pelites intruded by mafi c dikes

12 Keppie et al.

and a leucogranite dike from the Columpio del Diablo granite) unconformably overlain by the Otate meta-arenite (lower green-schist facies psammites and pelites): roughly temporal equiva-lents are the Middle-Upper Ordovician Mal Paso unit and pre-latest Devonian Ojo de Agua unit (interbedded metasandstone and slate, and metapelite and mafi c minor intrusions, respectively)—the Otate and Mal Paso units are intruded by the massive, 461 ± 2 Ma, Palo Liso megacrystic granite: decussate, contact metamor-phic muscovite yielded a 40Ar/39Ar plateau age of 440 ± 4 Ma; (iv) a steeply-moderately, E-dipping normal fault; (v) uppermost Devonian-Lower Permian sedimentary rocks (Patlanoaya Group: here elevated from formation status). The upward decrease in metamorphic grade is paralleled by a decrease in the number of penetrative fabrics, which varies from (i) three in the Piaxtla Suite, through (ii) two in the Las Minas unit (E-trending sheath folds deformed by NE-trending, subhorizontal folds with top to the southeast asymmetry, both associated with a solution cleav-age), (iii) one in the Otate, Mal Paso, and Ojo de Agua units (steeply SE-dipping, NE-SW plunging, open-close folds), to (iv) none in the Patlanoaya Group. 40Ar/39Ar analyses of muscovite from the earliest cleavage in the Las Minas unit yielded a plateau age of 347 ± 3 Ma and show low temperature ages of ~260 Ma. Post-dating all of these structures and the Pat lanoaya Group are NE-plunging, subvertical folds and kink bands. An E-W, vertical normal fault juxtaposes the low-grade rocks against the Anaca-huite amphibolite that is cut by megacrystic granite sheets, both of which were deformed by two penetrative fabrics. Amphibole from this unit has yielded a 40Ar/39Ar plateau age of 299 ± 6 Ma, which records cooling through ~490 °C and is probably related to a Permo-Carboniferous reheating event during exhumation. The extensional deformation is inferred to have started in the latest Devonian (~360 Ma) during deposition of the basal Patlanoaya Group, lasting through the rapid exhumation of the Piaxtla Suite at ~350–340 Ma synchronous with cleavage development in the Las Minas unit, deposition of the Patlanoaya Group with active fault-related exhumation suggested by Mississippian and Early Permian conglomerates (~340 and 300 Ma, respectively), and continuing at least into the Middle Permian (≡ 260 Ma muscovite ages). The continuity of Mid-Continent Mississippian fauna from the USA to southern Mexico suggests that this extensional defor-mation occurred on the western margin of Pangea after closure of the Rheic Ocean.

STOP 3-1 (N18°° 11.728′, W98°° 14.690′ to N18°° 11.652′, W98°° 15.065′: Fig. 2)

Contact between a deformed, Ordovician megacrystic grani-toid, a Tertiary dike, and the HP Piaxtla Suite at Piaxtla.

STOP 3-2 (UTM: 1405110/2023872: Fig. 7)

Thrust contact between Tehuitzingo serpentinite and polydeformed psammitic-pelitic rocks at Solozuchitl near Atopoltitlan.

The Piaxtla serpentinites are composed almost entirely of secondary minerals. Decussate, acicular and fi brous crystals serpentine aggregates make up 95% of the rock, magnetite, cal-cite, white mica and talc, and accessory chromite, clinochlore, undulose quartz, amphibole and epidote. This serpentinite are thrust over the low grade psammite-pelite unit along a gently NW-dipping thrust (320/15°), on which there are striae that plunge westwards (290/12°): associated recumbent folds, S-C fabrics and thrust horses indicate thrusting toward the west. Cut-ting across this thrust zone are several N-S vertical faults with subhorizontal striae.

The low grade psammite-pelite unit (498 ± 2 Ma, U-Pb de-trital zircon; Galaz-Escanilla et al., in press) is composed mainly of primary minerals such as quartz, feldspar and zircon (acces-sory), which suggests a medium-grained quartz-arenitic (0.25–0.5 mm) and shaly (<0.06 mm grain size) protoliths respectively. The equilibrium secondary mineralogy is composed of quartz, albite (Ab

99–100), Mg-Fe-chlorite (ripidolite type), phengite, epidote,

calcite and leucoxene, whose geothermobarometry indicated P-T conditions of ~2.7 kbar and ~350 °C (greenschist facies; Galaz-Escanilla and Keppie, in press).

STOP 3-3 (UTM: 140571085/2023811: Fig. 7)

Serpentinite, amphibolite, metabasite, Ordovician granitic and psammitic-pelitic rocks along the eastern margin of the Tehuit zingo serpentinite at Tecolutla.

In Tecolutla area outcrop a HP unit (eclogitic facies) that mainly consists of serpentinized harzburgite with small marginal fault blocks of metabasite, metagranitoid (485 ± 3 Ma, U-Pb zircon age: Galaz-Escanilla et al., in press) and mica schist (433 ± 3 Ma, U-Pb detrital zircon: Galaz-Escanilla et al., in press) juxta-posed by N-S structures. The serpentinized harzburgites contain elliptical meta basite lenses up to several meters in size, which have fi ne grained margins that may refl ect an original intrusive relationship. The long axes of the elliptical lenses are parallel to the foliation indi cat ing ductile deformation. On the other hand, the high-grade metasediments have a composite foliation where S

1 is parallel to a second S-C foliation with the S

2 planes sub-

parallel to the border of the block and oriented ~128/27° (dip direction/dip angle), and C

2 planes oriented ~147/58°.

The HP unit is tectonically juxtaposed against a low grade psammite-pelitic unit along N-S structures. This unit has a planar fabric composed mainly of white mica and chlorite evidencing a low-temperature (greenschist) ductile deformation.

The geothermobarometry suggests a common prograde meta morphic history for the Tehuitzingo HP rocks: (a) a metamor-phic peak eclogite facies of zoisite-amphibole, with a tempera-ture of ~750 °C and a pressure of ~16 kbar; (b) retrogression to amphibolite-epidote facies, with a temperature of ~472 °C and variable pressures between ~7.1–3.4 kbar; (c) retrogression to green-schist facies with a temperature of ~360 °C and whose pressures were not obtained (Galaz-Escanilla et al., in press). The Piaxtla serpentinite contains three types of serpentine group minerals :


Figure 7. Stops 3-2 and 3-3: geological map, structural data, and section (after Galaz-Escanilla et al., in press).

14 Keppie et al.

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re 8

. Sto

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-5, 3

-6 a

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chrysotile, lizardite and antigorite. Based on the stability fi eld of the latter was estimated a P-T peak of ~550 °C and ~9 kbar (González-Mancera, 2001), however, has been reported in sub-duction zones antigorite reaching ~720 °C and high pressures of ~20 kbar (Ulmer and Trommsdorff, 1995).

The geochemistry data of the eclogitic mafi c rocks indicate that these rocks have an arc affi nity (author´s unpublished data). The P-T-t pattern of these rocks is consistent with subduction environments and serpentinite subduction channel exhumation (e.g., Guillot et al. 2009), where the driving forces for exhuma-tion are a combination of buoyancy and channel fl ow coupled with underplating of slabs.

STOP 3-4 (N18°° 31.051′, W98°° 19.733′: Fig. 8)

Listric normal shear zone between megacrystic, Columpio del Diablo granitoid and Ordovician Las Minas unit.

The Columpio del Diablo megacrystic granite (492 ± 12 Ma, U-Pb zircon age: Keppie et al., 2010) consists of blastomylonitic granite containing quartz, K-feldspar (perthitic orthoclase), white mica, chlorite, epidote, and accessory opaque minerals. The megacrystic granite is cut by thin leucogranite sheets that consist mainly of quartz and potassium feldspar and are inferred to be a late differentiates of the granite. Structurally, the gran-ite varies from an L-tectonite to an L-S tectonite with kinematic indicators, such as σ fabrics associated with the feldspars and generally vertical, extensional, quartz-fi lled fractures within the feldspars that indicate top-to-east movement along the contact with the Las Minas Unit: a minor, brittle fault has been super-imposed on the contact. The Las Minas unit consists predomi-nantly of polydeformed, low-grade psammites interbedded with thin pelitic phyllites, and intruded by many tholeiitic mafi c dikes and sills (Keppie et al., 2008). The psammites consist mainly of quartz with minor muscovite, chlorite, and K-feldspar, and ac-cessory zircon, whereas the phyllites are composed of muscovite, chlorite, quartz, and opaque minerals. The youngest concordant detrital zircon is dated at 496 ± 25 Ma (Keppie et al., 2008) The mafi c intrusions contain amphibole (tremolite-actinolite), chlo-rite, epidote, quartz, plagioclase, muscovite, and accessory cal-cite, and opaque minerals. 40Ar/39Ar analyses of muscovite from the earliest cleavage in the Las Minas unit yielded a plateau age of 347 ± 3 Ma (Mississippian) and show low temperature ages of ~260 Ma.

STOP 3-5 (N18°° 30.351′, W98°° 17.57′: Fig. 8)

The Cerro Puntiagudo Formation of Strunian age (latest Devo nian) is 63 m thick and consists of shale, sandstone, and limestone. It is overlain by conglomerates of the Potrerillo Formation (124 m thick) that consists of red sandstone with Oseagean fossils and conglomerate with large K-feldspar clasts: these clasts are inferred to have been derived from the nearby megacrystic granitoids. The Cerro Puntiagudo Formation rests unconformably upon the Ojo de Agua unit, which consists of

fi nely bedded, black pelitic rocks intruded by green, fi ne grained, mafi c dikes with an arc-related chemistry. These latter rocks are deformed by isoclinal, upright-steeply inclined, NE- and SE- trending, subhorizontal folds. The youngest detrital zircons in this unit are 466 ± 25 Ma (Keppie et al., 2008), abd 471 ± 9 Ma (Keppie et al., 2010).

STOP 3-6 (N18°° 30.66′ W98°° 17.78′: Fig. 8)

The La Junta Formation is a 126 m thick shale unit contain-ing Missourian fossils; the Tepazulco Formation (193 m thick) is made up of interbedded limestone, shale, and sandstone and con-tains Virgilian-Missourian fossils. An Ordovician plug is faulted against the Patlanoaya Group at this locality.

STOP 3-7 (N18°°31′, W°°16.79′: Fig. 8)

The Lower Permian La Mesa, La Cuesta and La Cueva For-mations consist of a conglomerate (45 m thick) and calcareous sandstone unit containing Wolfcampian fossils; interbedded shale and limestone with mid-Wolfcampian to middle Leonardian fos-sils; and sandstone (>280 m thick) containing late Leonardian fossils at its base.

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5R E S U M E N Y C O N C L U S I Ó N

Este trabajo documenta el desarrollo de un sistema de arco Carbonífero-Pérmico a lo largo del margen occidental de Pangea junto a una zona desubducción del océano Paleo-Pacífico. Se proporciona información detalla-da sobre la relación entre el plutonismo, la formación de cuencas y la defor-mación a escala regional en un orógeno periférico. Las principales conclu-siones son las siguientes:

a. La cartografía geológica detallada de la zona en combinación con losdatos de la geocronología U-Pb de circones da como resultado la mo-dificación de la distribución espacial y las relaciones de contacto de lasunidades litotectónicas previamente mapeadas en el área de estudio.Los contactos externos entre el plutón Totoltepec y las rocas circun-dantes son o no conformables, o son tectónicos (es decir, ninguna delas relaciones de contacto originales son preservadas). Sin embargo, laedad de diques graníticos delgados que ocurren dentro de la Forma-ción Tecomate sugieren que pueden ser comagmáticos con el plutónTotoltepec, lo que implica una relación originalmente intrusiva entreel plutón y la Formación Tecomate.

b. Rocas clásticas al suroeste del plutón Totoltepec que fueron asignadosoriginalmente a la Formación Cosoltepec contienen circones detríti-cos de edad Pérmico y por lo tanto se consideran equivalentes a laFormación Tecomate. Esta interpretación es coherente con la presen-cia de metaconglomerados y mármoles en esta parte de la zona decampo. Además, en la parte oriental del área de estudio se identificauna unidad metamórfica de grado medio y edad Misisipiense (artícu-lo en preparación), que consiste en cuarcitas y esquistos de granatecon escasos diques de anfibolita; esto limita la distribución espacialde la unidad previamente mapeada como la Formación Tecomate. Launidad Misisipiense está en contacto de falla con el plutón Totolte-pec, cabalgando en dirección sur sobre la Formación Tecomate y estásobreyacida por capas rojas del Jurásico hacia el norte. Con base endatos isotópicos y geoquímicos, las rocas de esta unidad Misisipiensese pueden correlacionar con las de la Unidad Salada del Carbonífe-ro (Morales-Gámez et al., 2008) que afloran en el lado occidental delplutón Totoltepec.

c. Circones detríticos extraídos de rocas de la Formación Tecomate en elárea de estudio en combinación con datos publicados de 40Ar/39Arproporcionan límites temporales de depositación a alrededor de 300

Ma en un nivel estratigrafico, y a entre 288 ± 3 Ma y 263 ± 3 Ma en

76

resumen y conclusión 77

otro. Estos datos coinciden con la edad bioestratigráficamente deter-minada en el área tipo de la Formación Tecomate (Keppie et al., 2004b)e indican que la formación, como se define actualmente de maneracolectiva se extiende desde el Pensilvánico medio hasta el PérmicoInferior, pero puede haber sido depositada en distintas sub-cuencasde diferentes edades. Una de las muestras analizadas, que provienede cerca de la base estratigráfica de la Formación Tecomate, produjosolamente circones de edad Proterozoica, lo cual sugiere que esta par-te de la unidad fue depositada cuando fuentes ígneas paleozoicas noestaban expuestas o no fueron muestreadas por el sistema de drena-je local. La última explicación también podría aclarar la discrepanciaentre las edades de las poblaciones más jóvenes de circones detríti-cos de la zona de estudio y el área tipo de la Formación Tecomate(Sánchez-Zavala et al., 2004), respectivamente.

d. La secuencia intrusiva del plutón Totoltepec se establece mediante ladocumentación del rango composicional, los contactos internos y laedad de las fases magmáticas; esto se basa en el análisis petrográficoy trabajo de campo detallado, complementado por la geocronología deU-Pb y 40Ar/39Ar. Estos datos sugieren que el plutón es una intrusióncompuesta, formado por (i) tres cuerpos discretos, alargados e inten-samente fallados de 306 ± 2 Ma, que consisten en gabro hornblendicoy hornblendita, aflorando a lo largo del margen norte del plutón; (ii)trondhjemita de 287 ± 2 Ma, la litología predominante del plutón, lo-calmente mostrando una mayor abundancia de biotita o plagioclasa ytransformándose a una composición granodiorítica y monzograníticacerca del margen norte; y, (iii) cuerpos intrusivos de tonalita y dioritahornblendica junto con diques félsicos que se presentan en el partesur del plutón, los cuales fueron emplazados secuencialmente entre289 ± 2 y 283 ± 1 Ma.

e. Tanto la fase marginal (gabróica) como la fase principal (trondhjemita-tonalita-diorítica) del plutón Totoltepec muestran una afinidad geo-química toleítica a calco-alcalina, típico de magmas asociados consubducción. Estos datos proporcionan evidencia de un manto litos-férico subcontinental hidratado por fluidos de subducción ya en 306

Ma aproximadamente, mucho antes de lo que varios estudios pro-ponen. Datos isotópicos de Sm-Nd indican una relación genética deasimilación-cristalización fraccionada (AFM) por cantidades menoresentre la fase marginal y principal del plutón. Plutones coetáneos delarco Carbonífero–Pérmico en el sur de México y Guatemala son másfélsicas y más alcalinas en composición, muestran patrones de tierrasraras más diferenciados y tienen una firma isotópica de Sm-Nd menosradiogénico; esto indica una mayor contaminación cortical en compa-ración con el plutón Totoltepec y sugiere que el plutón fue emplazadoen una parte más primitiva, más cercana a la trinchera del arco y/o alo largo de una falla que facilitó su ascenso.


f. Las rocas de la Formación Tecomate en el área de estudio son deriva-das del edificio del arco regional y de plutones epizonales expuestosdurante el Carbonífero y el Pérmico Inferior, lo cual es indicado por:(i) la ocurrencia de estratos intercalados de rocas volcánicas y clásti-cas que son derivados de un arco; (ii) la inmadurez composicional ytextural de los sedimentos; (iii) la firma geoquímica de arco de lasrocas clásticas; (iv) composiciones isotópicas de Sm-Nd relativamenteradiogénicos que sugieren un componente de procedencia juvenil; y,(v) el predominio de circones detríticos del Carbonífero–Pérmico pro-cedentes de una fuente ígnea. Por lo tanto, circones detríticos de laFormación Tecomate complementan el registro detrítico fragmentadode la actividad del arco magmático regional en el sur de México. Enconjunto con otras rocas ígneas y sedimentarias relacionadas con elarco en México y Guatemala, cuya edad también está bien definidapor bioestratigrafía o por geocronología U-Pb, los datos sugieren quela actividad de arco ya había iniciado en el Misisípico en los bloquesmás al sur y probablemente no fue establecido en los terrenos delnorte de México hasta el Pérmico Inferior.

g. La historia estructural para la fase principal del plutón Totoltepec deaproximadamente 289–287 Ma, como se infiere a partir de la termoba-rometría Al-en-hornblenda y la geocronología 40Ar/39Ar involucróel emplazamiento de magma en niveles medianos de la corteza (unos20 km de profundidad) y un levantamiento rápido hasta aproximada-mente 11 km en 4 ± 2 Ma. La forma superficial elíptica del plutón,una progresión de una fábrica de flujo magmático a una fábrica deestado sólido de baja temperatura, así como el paralelismo entre lasfoliaciones de temperaturas distintas indican que el emplazamientode la fase principal del plutón fue controlada tectónicamente. La in-trusión principal contiene una foliación subvertical paralela al eje lar-go del plutón, y una lineación mineral que varia desde subhorizontalcon cinemática sinistral hasta muy inclinada con indicadores de cabal-gamiento de vergencia sur. La variación en la orientación y el gradode deformación manifestado por las diferentes poblaciones de diquessugieren que los diques fueron emplazados secuencialmente y fueronsometidos a diferentes grados de rotación en sentido horario.

h. En el marco del arco regional que está dominado por cizallamientodextral a lo largo de fallas N–S, el emplazamiento del plutón Totol-tepec se infiere haber tenido lugar a lo largo de un sistema de fallastransversales al arco de extensión oblicua y dirección NE en un ré-gimen general de transtensión. El magmatismo puede haber cesadoen la zona cuando una parte del cizallamiento dextral de la falla de-limitante del oeste fue trasladado a la falla delimitante del este, queculminó en cabalgamiento cerca del margen sur del plutón. Por úl-timo, como parte de un evento importante de deformación regionalen el Triásico Medio a Tardío, que se registra en las rocas tanto de


la Formación Tecomate como de la unidad Misisipiense sin nombre(artículo en preparación), el plutón fue cabalgado sobre las rocas me-tasedimentarias de la Formación Tecomate.

i. Este estudio documenta la evolución geodinámica de un arco conti-nental del Paleozoico tardío en el Complejo Acatlán. Los datos sugie-ren subducción oblicua de litosfera oceánica hacia el este, por debajodel terreno Mixteco, que produjo el desarrollo de fallas laterales N–Sparalelas a la trinchera y fallas antitéticas de orientación NE que pro-movió el plutonismo y dio lugar a la formación de múltiples cuencaspull-apart. Esta situación tectónica es más compatible con una ubica-ción paleogeográfica del terreno Mixteco en el margen de Pangea queuna posición en el Golfo de México, varios miles de kilómetros haciael interior, o incluso una ubicación frente al noreste de Canadá.

AM É T O D O S A N A L Í T I C O S

A.1 y A.2: Material suplementario publicado en línea como parte del ar-tículo: Kirsch, M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permian–Carboniferous arc magmatism and basin evolution along the western mar-gin of Pangea: geochemical and geochronological evidence from the easternAcatlán Complex, southern Mexico: Geological Society of America Bulletin,en prensa, doi: 10.1130/B30649.1.

a.1 geocronología u-pb

About 70 grains for igneous analyses and 150 grains in case of detritalzircon analyses were handpicked and mounted on double-sided adhesivetape. To avoid introducing bias into sample preparation, no selection wasmade on the basis of optical and physical characteristics. The mount wasthen cast in epoxy resin, ground with sandpaper to expose the crystals andpolished. Cathodoluminescence imaging was performed using an ELM-3Rluminoscope, to reveal internal zoning of the zircons, helping with the spotselection and aiding the geological age interpretation. The isotopic analy-ses were performed with a Resolution LPX220 ArF Excimer laser ablationsystem coupled to a Thermo Xii series quadrupole ICP-MS (Solari et al.,2010) installed in the Laboratorio de Estudios Isotópicos (LEI), Centro deGeociencias, UNAM. A 34 µm spot was used for all the analyses performedduring the current work. Repeated standard measurements of the Plešovicestandard zircon, (Sláma et al., 2008) enabled mass-bias correction, as well asdownhole and drift fractionation corrections. The analytical routine inclu-des a standard glass (normally NIST 610 is analyzed), 5 standard zircons,5 unknown zircons, and then 1 standard zircon every 5 unknowns, endingwith 2 standard zircons. The same analytical protocol is employed (timing,energy density, laser frequency, spot size) for all the analyses, both stan-dard and unknowns. NIST standard glass analyses are used to recalculatethe zircons trace element concentrations. Time-resolved analyses are thenreduced off-line using an in-house developed sofware written in R (Solariy Tanner, 2011), and the output is then imported into Excel, where the con-cordia as well as age-error calculations are obtained using Isoplot v. 3.70

(Ludwig, 2008), while the probability density distribution and histogramplots are produced using AgeDisplay (Sircombe, 2004). During the analyti-cal sessions in which the data presented in this paper were measured at LEI,UNAM, the observed uncertainties (1σ relative standard deviation) on the206Pb/238U, 207Pb/206Pb and 208Pb/232Th ratios measured on the Plešo-vice standard zircon were 0.6, 0.9 and 1.1 % respectively. Those errors arequadratically added to the quoted uncertainties observed on the measured

80

A.2 geoquímica 81

isotopic ratios of the unknown zircons. This last factor takes into accountthe heterogeneities of the natural standard zircons. 204Pb, which would beused to correct for initial common Pb, is not measured because its tiny sig-nal is swamped by 204Hg, normally present in the He carrier gas. CommonPb is thus evaluated using the 207Pb/206Pb ratio, carefully graphing all theanalyses on Tera y Wasserburg (1972) diagrams. Correction, if needed, isthen performed with the algebraic method of Andersen (2002).

a.2 geoquímica

Major and certain trace elements (V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr,Nb, Ba, La, Pb, Th, U, Ce, Nd, Cs) were determined by X-ray fluorescen-ce spectrometry (XRF) at the Regional Geochemical Centre at Saint Mary’sUniversity, Nova Scotia. Precision and accuracy are generally within 5 % formost major elements, and within 5–10 % for minor and trace elements. De-tails of the analytical procedures are given in Dostal et al. (1986, 1994). REEsand selected trace elements were analyzed by inductively coupled plasmamass spectrometry (ICP-MS) at Memorial University, Newfoundland. Theaccuracy and precision of these data are better than 10 %; the analytical pro-cedure is detailed in Longerich et al. (1990). Sm-Nd isotopic analyses wereperformed at the Atlantic Universities Regional Isotopic Facility (AURIF),Memorial University, Newfoundland. Sm and Nd concentrations as well asisotopic compositions and ratios were measured by isotope dilution thermalionization mass spectrometry (ID-TIMS) after chemical separation of Ndand Sm by ion exchange chromatography (see Kerr et al., 1995). Instrumen-tal mass fractionation of Nd isotopes is corrected relative to 146Nd/144Nd= 0.7219 (O’Nions et al., 1977) using a Raleigh fractionation law. Externalprecision is assessed by replicate analyses of the JNdi-1 standard (Tana-ka et al., 2000). The difference between the certified value (143Nd/144Nd =0.512115) and the mean (0.512101 ± 0.000008 [n = 45]) is added to the measu-red value for 143Nd/144Nd after it has been spike-corrected. Errors quotedin Table 1 represent standard errors of individual 143Nd/144Nd measure-ments at the 95 % confidence level. εNd parameters were calculated relativeto 143Nd/144Nd = 0.512638 for CHUR (Goldstein et al., 1984). For initial va-lues, 147Sm/144Nd = 0.1967 (Jacobsen y Wasserburg, 1980) and λ147Sm =6.54 x 10

−12 yr−1 (Steiger y Jäger, 1977) were used. Depleted mantle modelages (TDM) are calculated in two ways: TDM(1) using the depleted mantlemodel of DePaolo (1981, 1988), and TDM(2) which assumes a linear evolu-tion of the depleted mantle between a value of +10 (present day) and 0 at4.5 Ga (Goldstein et al., 1984). TDM(1) values are quoted in the text.

a.3 geocronología40

ar-39ar

Los separados de minerales y los monitores de flujo (estándares) fueronenvueltos en papel de aluminio y apilados verticalmente en una cápsula deirradiación 8.5 cm de largo y 2.0 cm de diámetro. Esta se irradió con neutro-

A.3 geocronología40

ar-39ar 82

nes rápidos en la posición 5C del Reactor Nuclear de McMaster (Hamilton,Ontario) para una duración de 24 h (a 2.5 MWh). Los paquetes de monitoresde flujo se encuentran a intervalos de aprox. 1 cm a lo largo del contenedorde irradiación y valores de J para las muestras individuales se determinaronpor interpolación polinómica de segundo orden entre los análisis repetidospara cada posición del monitor en la cápsula. Típicamente, valores de J va-rían menos que 10 % a lo largo de la cápsula. No se controlan gradienteshorizontales de flujo ya que se consideran ser de menor importancia en elnúcleo del reactor.

Para la fusión total de los monitores y el calentamiento por pasos utili-zando un láser, las muestras se colocan en un portamuestras de cobre, pordebajo del viewport ZnS de una celda de acero inoxidable conectado a unsistema de la purificación del vacío ultra-alto. Para el calentamiento por pa-sos se utilizó un láser New Wave Research MIR 10-30 de CO2 con potenciasde hasta 30W y una lente de facetas. Los periodos de calefacción son aprox.3 minutos por cada incremento de energía (2 % a 20 %; diámetro del haz 3.8mm). El gas liberado, después de la purificación mediante un getter SAESC50 (unos 5 minutos), es conducido a un espectrómetro de masas MAP 216

con una fuente Bäur Signer y un multiplicador de electrones (ajustado auna ganancia de 100 por el detector de copa de Faraday). Posteriormente,los análisis rutinarios del blanco se restan de las fracciones de gas de lasmuestras. Los blancos de extracción son típicamente <10 × 10

−13, <0.5 ×10

−13, <0.5 × 10−13, y <0.5 × 10

−13 cm−3 STP para las masas 40, 39, 37, y36, respectivamente.

Mediciones de los picos de los isótopos de argón son extrapolados altiempo cero, normalizados a la relación 40Ar/36Ar atmosférica (295.5) utili-zando los valores obtenidos para el argón atmosférico, y corregidos a 40Arproducido por potasio, 39Ar y 36Ar por calcio, y a 36Ar producido por cloroRoddick (1983). Las fechas y los errores se calcularon utilizando el procedi-miento de Dalrymple et al. (1981) y las constantes de Steiger y Jäger (1977).La meseta e la inversa correlación de las fechas isotópicas se calcularon uti-lizando ISOPLOT v. 3.60 (Ludwig, 2008). Una meseta se define aquí como3 o más etapas contiguas que contienen >50 % del 39Ar liberado, con unaprobabilidad de ajuste >0.01 y un promedio ponderado de las desviacionescuadráticas <2. Si los pasos contiguos contienen <50 % del 39Ar liberado,se conoce como un segmento de meseta.

Los errores citados en la tabla y en los espectros de edad representan laprecisión analítica a 2σ, suponiendo que los errores en las edades de losmonitores de flujo son cero. Esto es adecuado para comparar la variacióndentro del espectro y determinar cuáles pasos forman una meseta (por ejem-plo, McDougall y Harrison (1988), p. 89). Una estimación conservadora deeste error en el valor de J es de 0.5 %; este se puede agregar para la compa-ración entre muestras. Las fechas están referenciadas a hornblenda Hb3Grde 1072 Ma (Turner et al., 1971; Roddick, 1983).

BTA B L A S G E O C R O N O L O G Í A U - P B

Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permian–Carboniferousarc magmatism and basin evolution along the western margin of Pangea:geochemical and geochronological evidence from the eastern Acatlán Com-plex, southern Mexico: Geological Society of America Bulletin, en prensa,doi: 10.1130/B30649.1.

Tabla 1: Description of samples for LA-ICP-MS U-Pb geochronology from the Totol-tepec area, Acatlán Complex.

Sample Latitude Longitude Rocktype Mineralogy Age

(◦N) (◦W) Primary Secondary Accessory (Ma)*

Permian granitoids (Totoltepec pluton)

TT-72 18.2581000 97.85163333 Hbl gabbro Hbl+Pl Ep+Chl Ap+Zrn+Op 306±2

TT-76b 18.2286500 97.86343333 Qz diorite Pl+Qz+Ms Chl Ap+Zrn+Op 289±2

Permian low-grade metasedimentary rocks

TT-81 18.25146667 97.78271667 Metaps. Qz+Kfs+Ms Chl Zrn+Op 288±3

TT-82 18.25058333 97.78281667 Metapel. Qz+Ms Chl+Ser Zrn+Op 299±3

TT-612 18.1912838 97.898541 Metaps. Qz+Kfs+Ms Chl Zrn+Op 303±3

TT-486A 18.2840884 97.9111441 Metaps. Qz+Kfs+Ms Chl Zrn+Op 1005±17

Thin dikes intruding Carboniferous–Permian low-grade metasedimentary rocks

TT-615 18.1908117 -97.8990905 Granitoid Qz+Pl+Ms Zrn+Op 298±3

Abbreviations: Qz–quartz, Kfs–K-feldspar, Pl–plagioclase, Hbl–hornblende, Bt–biotite, Ms–muscovite, Ser–sericite, Ep–epidote, Chl–chlorite, Ap–apatite, Grt-garnet, Tnt–titanite, Zrn–zircon, Op–opaque minerals* LA-ICP-MS U-Pb zircon ages representing the age of crystallization in igneous rocks andan average of the youngest detrital zircon cluster in metasedimentary rocks, respectively(see text for details).

83

tablas geocronología u-pb 84

Tabl

a2

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Toto

ltep

ecpl

uton

horn

blen

dega

bbro

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_31

_04

30

.49

0.0

58

91

2.2

10

.34

26

52

.34

0.0

42

24

0.8

00.3

32

67

22

99

65

64

47

26

72

Zrc

_19

_02

90

.54

0.0

53

32

2.1

00

.34

85

32

.18

0.0

47

48

0.5

90.2

72

99

23

04

63

42

46

299

2Z

rc_2

1_0

32

0.3

90

.05

30

63

.20

0.3

45

50

3.4

50

.04

74

41

.31

0.3

72

99

43

01

93

31

71

299

4Z

rc_2

4_0

35

0.4

80

.05

30

42

.39

0.3

47

32

2.4

80

.04

75

70

.61

0.2

63

00

23

03

63

31

53

300

2Z

rc_0

2_0

09

0.6

10

.05

22

02

.30

0.3

44

37

2.4

10

.04

78

80

.73

0.3

03

01

23

00

62

94

50

301

2Z

rc_0

9_0

17

0.6

00

.05

49

32

.60

0.3

61

84

2.6

90

.04

78

30

.71

0.2

63

01

23

14

74

09

56

301

2Z

rc_0

5_0

12

0.4

20

.05

76

92

.89

0.3

81

16

3.0

10

.04

80

40

.81

0.2

83

02

23

28

85

18

62

302

2Z

rc_1

0_0

18

0.4

20

.05

58

82

.70

0.3

69

09

2.7

90

.04

79

50

.71

0.2

53

02

23

19

84

48

58

302

2Z

rc_1

7_0

27

0.5

40

.05

32

62

.29

0.3

51

47

2.3

90

.04

79

60

.65

0.2

93

02

23

06

63

40

50

302

2Z

rc_0

1_0

08

0.5

20

.05

34

52

.51

0.3

54

38

2.6

00

.04

80

60

.71

0.2

63

03

23

08

73

48

54

303

2Z

rc_0

3_0

10

0.5

50

.05

49

42

.29

0.3

62

74

2.4

10

.04

80

60

.73

0.3

13

03

23

14

74

10

50

303

2Z

rc_3

8_0

50

0.5

10

.05

17

32

.20

0.3

42

35

2.2

60

.04

81

00

.52

0.2

23

03

22

99

62

73

49

303

2Z

rc_0

4_0

11

0.5

50

.05

38

62

.10

0.3

58

98

2.2

20

.04

83

10

.72

0.3

33

04

23

11

63

65

46

304

2Z

rc_3

5_0

46

0.5

30

.05

21

32

.09

0.3

47

37

2.1

90

.04

83

60

.62

0.3

03

04

23

03

62

91

47

304

2Z

rc_3

2_0

44

0.5

50

.05

42

52

.19

0.3

61

86

2.3

00

.04

84

60

.68

0.3

13

05

23

14

63

81

48

305

2Z

rc_3

4_0

45

0.4

50

.05

20

92

.30

0.3

46

87

2.4

10

.04

84

10

.70

0.2

93

05

23

02

62

89

51

305

2Z

rc_0

7_0

15

0.5

30

.05

36

52

.11

0.3

58

74

2.2

30

.04

86

30

.74

0.3

33

06

23

11

63

56

46

306

2Z

rc_0

8_0

16

0.4

30

.05

33

32

.91

0.3

55

95

2.9

80

.04

85

60

.68

0.2

23

06

23

09

83

43

64

306

2

Con

tinue

don

next

page

...


Tabl

a2

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Toto

ltep

ecpl

uton

horn

blen

dega

bbro

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_12

_02

10

.50

0.0

54

11

2.2

00

.36

17

22

.29

0.0

48

61

0.6

20.2

73

06

23

13

63

76

48

306

2Z

rc_1

6_0

26

0.4

60

.05

49

12

.60

0.3

68

24

2.7

00

.04

86

40

.74

0.2

63

06

23

18

74

09

56

306

2Z

rc_2

2_0

33

0.4

00

.05

21

12

.71

0.3

48

04

2.7

80

.04

85

60

.66

0.2

33

06

23

03

72

90

60

306

2Z

rc_2

7_0

38

0.6

10

.05

43

02

.39

0.3

62

95

2.4

80

.04

85

40

.64

0.2

63

06

23

14

73

84

53

306

2Z

rc_1

3_0

22

0.5

50

.05

41

82

.49

0.3

64

20

2.5

90

.04

87

20

.70

0.2

83

07

23

15

73

79

54

307

2Z

rc_2

8_0

39

0.4

70

.05

19

63

.00

0.3

50

12

3.1

10

.04

88

90

.82

0.2

63

08

23

05

82

84

67

308

2Z

rc_2

9_0

40

0.4

00

.05

12

12

.89

0.3

45

82

2.9

80

.04

89

40

.65

0.2

43

08

23

02

82

50

65

308

2Z

rc_3

7_0

49

0.4

90

.05

33

42

.10

0.3

59

55

2.2

10

.04

89

20

.67

0.3

13

08

23

12

63

43

46

308

2Z

rc_3

9_0

51

0.3

70

.05

34

13

.30

0.3

56

17

3.8

60

.04

89

12

.00

0.5

23

08

63

09

10

34

67

330

86

Zrc

_20_0

30

0.4

10

.05

44

13

.11

0.3

66

35

3.1

90

.04

91

00

.75

0.2

33

09

23

17

93

88

68

309

2Z

rc_3

0_0

41

0.4

20

.05

28

32

.31

0.3

57

07

2.3

80

.04

91

40

.61

0.2

43

09

23

10

63

22

51

309

2Z

rc_3

6_0

48

0.4

90

.05

28

72

.10

0.3

57

70

2.2

20

.04

91

70

.71

0.3

23

09

23

10

63

23

47

309

2Z

rc_0

6_0

14

0.3

00

.05

84

13

.41

0.3

94

74

3.5

20

.04

92

00

.91

0.2

53

10

33

38

10

54

57

231

03

Zrc

_26_0

37

0.3

00

.05

69

53

.11

0.3

85

95

3.1

90

.04

93

10

.73

0.2

23

10

23

31

94

90

67

310

2Z

rc_4

1_0

53

0.4

80

.05

32

72

.59

0.3

59

62

2.7

20

.04

92

50

.79

0.3

03

10

23

12

73

40

57

310

2Z

rc_1

1_0

20

0.5

90

.05

45

62

.20

0.3

71

71

2.3

00

.04

95

00

.69

0.3

03

11

23

21

63

94

48

311

2Z

rc_1

5_0

24

0.3

40

.05

52

93

.60

0.3

75

43

3.7

00

.04

94

40

.87

0.2

33

11

33

24

10

42

47

831

13


Tabl

a3

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Toto

ltep

ecpl

uton

quar

tzdi

orit

e.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_56

_07

40

.01

0.0

51

90

1.4

30

.31

57

81

.59

0.0

44

13

0.4

80

.40

27

81

27

94

28

13

327

81

Zrc

_81

_10

40

.65

0.0

52

71

1.9

00

.32

36

82

.15

0.0

44

61

1.0

10

.47

28

13

28

55

31

64

328

13

Zrc

_52

_06

91

.19

0.0

52

39

1.2

00

.32

62

11

.33

0.0

45

15

0.5

80

.42

28

52

28

73

30

22

628

52

Zrc

_57

_07

50

.27

0.0

52

94

1.9

10

.32

93

91

.99

0.0

45

17

0.6

00

.28

28

52

28

95

32

64

028

52

Zrc

_47

_06

30

.63

0.0

52

01

1.5

00

.32

58

81

.57

0.0

45

43

0.4

60

.30

28

61

28

64

28

63

228

61

Zrc

_76

_09

80

.27

0.0

53

01

2.2

10

.33

20

02

.28

0.0

45

42

0.6

20

.26

28

62

29

16

32

95

028

62

Zrc

_79

_10

10

.29

0.0

54

52

2.4

90

.34

05

22

.57

0.0

45

32

0.6

00

.24

28

62

29

87

39

35

628

62

Zrc

_59

_07

70

.42

0.0

53

76

1.9

00

.33

77

82

.00

0.0

45

56

0.6

10

.31

28

72

29

55

36

14

028

72

Zrc

_66

_08

60

.52

0.0

53

34

1.5

90

.33

56

11

.70

0.0

45

60

0.5

70

.35

28

72

29

44

34

33

428

72

Zrc

_70

_09

00

.35

0.0

52

70

1.7

10

.33

23

81

.78

0.0

45

70

0.5

00

.27

28

81

29

14

31

63

928

81

Zrc

_74

_09

50

.62

0.0

51

59

1.6

10

.32

50

91

.69

0.0

45

72

0.5

20

.30

28

81

28

64

26

73

728

81

Zrc

_42

_05

70

.72

0.0

54

44

1.6

00

.34

36

51

.69

0.0

45

84

0.5

50

.33

28

92

30

04

38

93

328

92

Zrc

_46

_06

20

.28

0.0

52

58

2.2

10

.33

11

42

.30

0.0

45

81

0.6

80

.29

28

92

29

06

31

14

728

92

Zrc

_49

_06

50

.29

0.0

49

66

2.5

00

.31

35

12

.60

0.0

45

82

0.7

00

.27

28

92

27

76

17

95

428

92

Zrc

_64

_08

30

.32

0.0

54

26

1.8

10

.34

36

51

.91

0.0

45

91

0.6

30

.32

28

92

30

05

38

23

828

92

Zrc

_69

_08

90

.53

0.0

53

37

1.5

00

.33

76

11

.61

0.0

45

87

0.5

90

.36

28

92

29

54

34

53

428

92

Zrc

_78

_10

00

.39

0.0

54

12

1.9

00

.34

12

12

.00

0.0

45

83

0.6

30

.31

28

92

29

85

37

64

328

92

Zrc

_72

_09

30

.35

0.0

51

70

1.8

00

.32

82

51

.86

0.0

45

99

0.5

00

.26

29

01

28

85

27

24

129

01

Con

tinue

don

next

page

...


Tabl

a3

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Toto

ltep

ecpl

uton

quar

tzdi

orit

e.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_82

_10

50

.59

0.0

52

44

1.3

90

.33

35

91

.48

0.0

46

06

0.5

00

.35

29

01

29

24

30

53

129

01

Zrc

_48

_06

40

.32

0.0

52

29

1.8

00

.33

26

91

.93

0.0

46

16

0.6

90

.37

29

12

29

25

29

83

829

12

Zrc

_55

_07

20

.34

0.0

53

02

1.7

90

.33

71

11

.90

0.0

46

10

0.6

10

.34

29

12

29

55

33

03

829

12

Zrc

_65

_08

40

.56

0.0

52

52

1.8

10

.33

40

41

.93

0.0

46

20

0.6

90

.35

29

12

29

35

30

83

829

12

Zrc

_58

_07

60

.62

0.0

52

38

1.3

90

.33

41

11

.51

0.0

46

27

0.5

60

.39

29

22

29

34

30

23

029

22

Zrc

_67

_08

70

.33

0.0

52

96

1.7

00

.33

88

11

.79

0.0

46

36

0.5

60

.31

29

22

29

65

32

73

829

22

Zrc

_44

_05

90

.61

0.0

52

45

1.5

10

.33

59

71

.60

0.0

46

44

0.5

60

.34

29

32

29

44

30

53

229

32

Zrc

_68

_08

80

.40

0.0

52

66

1.9

00

.33

86

12

.00

0.0

46

58

0.6

20

.32

29

32

29

65

31

44

329

32

Zrc

_75

_09

60

.38

0.0

53

14

1.9

00

.34

07

01

.97

0.0

46

51

0.5

20

.26

29

31

29

85

33

54

329

31

Zrc

_77

_09

90

.52

0.0

52

05

1.5

00

.33

41

51

.57

0.0

46

53

0.4

70

.31

29

31

29

34

28

83

429

31

Zrc

_80

_10

20

.26

0.0

52

78

2.1

00

.33

93

82

.20

0.0

46

65

0.6

40

.29

29

42

29

76

31

94

729

42

Zrc

_50

_06

60

.35

0.0

53

05

2.5

10

.34

10

32

.61

0.0

46

81

0.7

50

.28

29

52

29

87

33

15

329

52

Zrc

_53

_07

00

.40

0.0

51

74

2.2

00

.33

47

02

.28

0.0

46

85

0.6

00

.26

29

52

29

36

27

44

729

52

Zrc

_54

_07

10

.27

0.0

50

76

2.0

10

.32

71

42

.12

0.0

46

80

0.6

80

.31

29

52

28

75

23

04

329

52

Zrc

_43

_05

80

.40

0.0

51

67

1.9

90

.33

45

82

.10

0.0

47

02

0.6

40

.32

29

62

29

35

27

14

329

62

Zrc

_71

_09

20

.33

0.0

52

91

2.1

00

.34

41

12

.24

0.0

47

20

0.7

60

.35

29

72

30

06

32

54

729

72

Zrc

_51

_06

80

.27

0.0

52

25

2.7

90

.34

30

22

.90

0.0

47

64

0.7

60

.27

30

02

29

98

29

66

030

02

Zrc

_62

_08

10

.25

0.0

51

76

6.3

90

.34

10

96

.70

0.0

47

80

0.9

00

.24

30

13

29

81

72

75

13

630

13

Con

tinue

don

next

page

...


Tabl

a3

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Toto

ltep

ecpl

uton

quar

tzdi

orit

e.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_63

_08

20

.38

0.0

56

26

2.2

00

.37

22

12

.37

0.0

47

94

0.9

00

.37

30

23

32

17

46

34

630

23

Zrc

_60

_07

80

.44

0.0

52

40

1.7

00

.34

82

21

.79

0.0

48

22

0.5

60

.31

30

42

30

35

30

33

630

42

Zrc

_73

_09

40

.36

0.0

51

90

1.9

10

.34

84

61

.98

0.0

48

70

0.5

50

.27

30

72

30

45

28

14

330

72

Zrc

_45

_06

00

.58

0.0

53

61

2.8

00

.36

25

62

.87

0.0

49

23

0.6

50

.23

31

02

31

48

35

55

931

02

Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_06

_01

40

.55

0.0

68

02

1.7

11

.06

95

01

.94

0.1

13

98

0.9

30

.47

69

66

73

81

08

69

35

696

6Z

rc_5

7_0

75

0.3

80

.07

09

80

.85

1.5

24

90

0.9

20

.15

60

00

.34

0.3

89

35

39

40

69

57

17

935

3Z

rc_1

3_0

22

0.0

20

.07

16

50

.75

1.6

18

10

0.8

40

.16

39

80

.36

0.4

49

79

39

77

59

76

14

979

3Z

rc_8

1_1

04

0.3

80

.07

20

81

.53

1.6

69

74

1.7

30

.16

80

20

.45

0.3

71

00

14

99

71

19

88

31

1001

4Z

rc_8

4_1

07

0.3

60

.07

28

70

.84

1.6

78

10

0.9

10

.16

72

40

.36

0.4

09

97

31

00

06

10

10

17

1010

17Z

rc_3

9_0

53

0.1

80

.07

40

80

.86

1.7

43

20

0.9

40

.17

08

40

.37

0.3

91

01

73

10

25

61

04

41

610

4416

Zrc

_21

_03

20

.43

0.0

74

74

0.8

31

.87

92

00

.91

0.1

82

65

0.3

70

.41

10

81

41

07

46

10

62

15

1062

15Z

rc_0

8_0

16

0.4

80

.07

49

11

.29

1.7

65

60

1.3

80

.17

13

80

.46

0.3

41

02

04

10

33

91

06

62

610

6626

Con

tinue

don

next

page

...


Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_93

_11

80

.38

0.0

74

92

1.0

91

.79

30

01

.15

0.1

73

88

0.3

50

.32

10

33

31

04

38

10

66

22

1066

22Z

rc_6

7_0

87

0.1

20

.07

60

61

.00

2.2

56

70

1.0

80

.21

54

50

.41

0.3

81

25

85

11

99

81

09

72

010

9720

Zrc

_97

_12

30

.26

0.0

76

51

1.0

11

.70

04

01

.89

0.1

60

53

1.6

00

.85

96

01

41

00

91

21

10

82

011

0820

Zrc

_54

_07

10

.32

0.0

76

86

1.7

01

.92

07

01

.76

0.1

81

36

0.4

50

.25

10

74

41

08

81

21

11

83

111

1831

Zrc

_25

_03

60

.39

0.0

77

08

1.6

01

.74

46

01

.70

0.1

64

36

0.5

70

.34

98

15

10

25

11

11

23

29

1123

29Z

rc_1

5_0

24

0.2

20

.07

73

01

.20

1.9

37

10

1.2

80

.18

20

90

.45

0.3

51

07

84

10

94

91

12

92

211

2922

Zrc

_16

_02

60

.81

0.0

77

30

1.2

01

.93

71

01

.28

0.1

82

09

0.4

50

.35

10

78

41

09

49

11

29

22

1129

22Z

rc_7

2_0

93

0.2

20

.07

74

50

.98

1.9

79

50

1.1

00

.18

57

70

.49

0.4

41

09

85

11

09

71

13

31

911

3319

Zrc

_05

_01

20

.48

0.0

77

48

0.8

32

.04

26

00

.90

0.1

91

38

0.3

40

.39

11

29

41

13

06

11

34

15

1134

15Z

rc_1

9_0

29

0.5

30

.07

76

61

.70

2.0

72

40

1.8

40

.19

40

90

.71

0.3

91

14

37

11

40

13

11

38

31

1138

31Z

rc_7

8_1

00

0.4

70

.07

77

30

.81

2.0

24

00

0.8

90

.18

90

40

.36

0.4

01

11

64

11

24

61

14

01

611

4016

Zrc

_83

_10

60

.06

0.0

77

81

0.8

72

.09

84

00

.93

0.1

95

76

0.3

40

.35

11

53

41

14

86

11

42

17

1142

17Z

rc_4

7_0

63

0.2

80

.07

78

40

.87

2.0

86

20

0.9

50

.19

45

10

.35

0.3

91

14

64

11

44

71

14

31

611

4316

Zrc

_55

_07

20

.51

0.0

77

83

1.9

01

.88

79

01

.97

0.1

76

50

0.5

20

.26

10

48

51

07

71

31

14

33

511

4335

Zrc

_70

_09

00

.44

0.0

77

90

1.0

02

.14

20

01

.07

0.1

99

67

0.3

80

.35

11

74

41

16

27

11

44

20

1144

20Z

rc_9

9_1

25

0.3

10

.07

79

00

.95

2.1

38

90

1.0

30

.19

92

70

.41

0.4

01

17

14

11

61

71

14

41

911

4419

Zrc

_07

_01

50

.34

0.0

77

93

0.8

92

.13

66

01

.01

0.1

98

94

0.4

70

.48

11

70

51

16

17

11

45

17

1145

17Z

rc_6

3_0

82

0.7

80

.07

80

10

.79

2.1

65

40

0.8

70

.20

14

40

.35

0.4

11

18

34

11

70

61

14

71

611

4716

Con

tinue

don

next

page

...


Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_94

_11

90

.26

0.0

78

06

0.9

92

.09

03

01

.08

0.1

94

44

0.4

20

.40

11

45

41

14

67

11

48

19

1148

19Z

rc_5

3_0

70

0.6

40

.07

81

31

.42

2.0

88

83

1.7

40

.19

39

00

.51

0.4

91

14

25

11

45

12

11

50

26

1150

26Z

rc_5

8_0

76

0.4

80

.07

82

81

.00

2.1

20

90

1.0

80

.19

66

90

.40

0.3

81

15

84

11

56

71

15

41

911

5419

Zrc

_98

_12

40

.44

0.0

78

29

0.8

82

.23

18

01

.08

0.2

07

11

0.6

30

.58

12

13

71

19

18

11

54

17

1154

17Z

rc_7

6_0

98

0.4

80

.07

83

71

.30

1.9

89

10

1.4

10

.18

43

60

.55

0.3

91

09

15

11

12

10

11

56

25

1156

25Z

rc_9

6_1

22

0.5

10

.07

84

30

.92

2.1

35

40

1.0

00

.19

76

00

.39

0.4

01

16

24

11

60

71

15

81

811

5818

Zrc

_45

_06

00

.36

0.0

78

54

0.7

82

.17

93

00

.85

0.2

01

34

0.3

30

.40

11

83

41

17

46

11

61

14

1161

14Z

rc_3

1_0

44

0.7

10

.07

86

11

.00

2.1

56

20

1.2

10

.19

92

10

.68

0.5

61

17

17

11

67

81

16

21

811

6218

Zrc

_65

_08

40

.23

0.0

78

59

0.8

92

.13

31

00

.96

0.1

97

02

0.3

50

.36

11

59

41

16

07

11

62

17

1162

17Z

rc_0

4_0

11

0.1

40

.07

86

20

.83

2.2

23

90

0.9

00

.20

54

10

.35

0.4

01

20

44

11

89

61

16

31

511

6315

Zrc

_46

_06

20

.33

0.0

78

64

1.0

02

.11

06

01

.07

0.1

94

93

0.3

90

.35

11

48

41

15

27

11

63

18

1163

18Z

rc_6

4_0

83

0.3

80

.07

86

30

.86

2.1

58

70

0.9

20

.19

93

10

.34

0.3

51

17

24

11

68

61

16

31

711

6317

Zrc

_82

_10

50

.27

0.0

78

65

1.2

82

.17

27

91

.47

0.2

00

37

0.4

60

.40

11

77

51

17

21

01

16

32

511

6325

Zrc

_80

_10

20

.31

0.0

78

77

1.2

12

.14

52

01

.29

0.1

97

85

0.4

80

.36

11

64

51

16

49

11

66

23

1166

23Z

rc_7

4_0

95

0.7

10

.07

88

90

.93

2.1

19

20

1.0

00

.19

50

00

.38

0.3

91

14

84

11

55

71

16

91

811

6918

Zrc

_51

_06

80

.32

0.0

78

93

0.9

52

.14

82

01

.04

0.1

97

59

0.4

30

.41

11

62

51

16

47

11

70

17

1170

17Z

rc_6

6_0

86

0.1

80

.07

89

31

.20

2.3

63

60

1.3

40

.21

73

20

.60

0.4

41

26

87

12

32

10

11

70

23

1170

23Z

rc_2

7_0

39

0.2

20

.07

90

50

.83

2.1

81

30

0.9

30

.20

05

10

.39

0.4

31

17

84

11

75

61

17

31

511

7315

Con

tinue

don

next

page

...


Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_14

_02

30

.39

0.0

79

08

1.4

02

.22

39

01

.49

0.2

04

51

0.5

00

.33

12

00

51

18

91

01

17

42

511

7425

Zrc

_24

_03

50

.40

0.0

79

57

1.2

82

.17

30

01

.49

0.1

98

06

0.4

20

.35

11

65

51

17

21

01

18

62

311

8623

Zrc

_29

_04

10

.69

0.0

79

55

1.1

12

.12

06

01

.15

0.1

93

66

0.3

40

.28

11

41

41

15

68

11

86

20

1186

20Z

rc_3

6_0

50

0.5

10

.07

95

51

.29

2.2

07

40

1.3

80

.20

15

40

.45

0.3

41

18

45

11

83

10

11

86

23

1186

23Z

rc_5

2_0

69

0.7

20

.07

96

61

.00

2.2

21

20

1.0

70

.20

22

70

.37

0.3

41

18

84

11

88

71

18

91

811

8918

Zrc

_86

_11

00

.58

0.0

79

90

1.2

02

.15

90

01

.28

0.1

96

17

0.4

40

.34

11

55

51

16

89

11

95

23

1195

23Z

rc_1

2_0

21

0.3

20

.08

00

91

.10

2.2

61

30

1.2

00

.20

50

50

.48

0.4

01

20

25

12

00

81

19

92

011

9920

Zrc

_09

_01

70

.48

0.0

80

24

1.5

02

.17

78

01

.56

0.1

97

09

0.4

10

.27

11

60

41

17

41

11

20

32

912

0329

Zrc

_22

_03

30

.40

0.0

80

44

0.9

22

.25

65

01

.00

0.2

03

88

0.4

00

.40

11

96

41

19

97

12

08

17

1208

17Z

rc_5

0_0

66

0.3

30

.08

04

90

.99

2.1

93

40

1.0

80

.19

80

00

.42

0.4

01

16

54

11

79

81

20

91

812

0918

Zrc

_35

_04

80

.51

0.0

80

59

1.9

12

.31

16

02

.19

0.2

08

03

0.5

00

.34

12

18

61

21

61

61

21

23

512

1235

Zrc

_75

_09

60

.37

0.0

80

71

1.4

02

.16

76

01

.50

0.1

95

19

0.5

30

.35

11

49

61

17

11

01

21

42

712

1427

Zrc

_43

_05

80

.28

0.0

80

76

0.9

92

.33

12

01

.06

0.2

09

62

0.3

90

.37

12

27

41

22

28

12

16

18

1216

18Z

rc_5

9_0

77

0.3

50

.08

10

81

.10

2.3

32

10

1.1

80

.20

88

50

.43

0.3

71

22

35

12

22

81

22

32

112

2321

Zrc

_88

_11

20

.59

0.0

81

19

1.3

12

.34

13

01

.42

0.2

09

14

0.5

70

.39

12

24

61

22

51

01

22

62

512

2625

Zrc

_23

_03

40

.36

0.0

81

98

1.0

02

.28

86

01

.11

0.2

02

79

0.4

90

.44

11

90

51

20

98

12

45

18

1245

18Z

rc_6

0_0

78

0.2

90

.08

23

41

.51

2.2

84

00

1.5

70

.20

16

70

.48

0.2

91

18

45

12

07

11

12

54

29

1254

29Z

rc_4

4_0

59

0.0

80

.08

25

91

.30

2.4

54

10

1.4

60

.21

58

30

.67

0.4

61

26

08

12

59

11

12

60

23

1260

23

Con

tinue

don

next

page

...


Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_85

_10

80

.28

0.0

82

62

0.9

22

.34

64

00

.99

0.2

06

02

0.3

60

.36

12

08

41

22

67

12

60

18

1260

18Z

rc_3

3_0

46

0.3

60

.08

29

61

.10

2.3

08

10

1.1

70

.20

21

10

.41

0.3

61

18

74

12

15

81

26

82

012

6820

Zrc

_28

_04

00

.33

0.0

83

00

0.8

92

.38

37

01

.00

0.2

08

66

0.4

50

.45

12

22

51

23

87

12

69

16

1269

16Z

rc_6

1_0

80

0.5

30

.08

29

71

.21

2.2

91

40

1.2

90

.20

03

80

.48

0.3

61

17

75

12

10

91

26

92

312

6923

Zrc

_18

_02

80

.54

0.0

83

18

1.0

02

.34

66

01

.09

0.2

04

93

0.4

30

.40

12

02

51

22

78

12

73

18

1273

18Z

rc_3

8_0

52

0.0

20

.08

32

30

.83

2.4

92

60

1.0

20

.21

73

70

.59

0.5

81

26

87

12

70

71

27

51

512

7515

Zrc

_56

_07

40

.03

0.0

83

30

1.2

02

.25

62

01

.27

0.1

96

93

0.4

30

.34

11

59

51

19

99

12

76

21

1276

21Z

rc_0

3_0

10

0.4

40

.08

34

91

.40

2.3

11

80

1.5

40

.20

13

90

.63

0.4

11

18

37

12

16

11

12

81

25

1281

25Z

rc_1

0_0

18

0.2

50

.08

36

10

.80

1.9

64

30

1.0

70

.17

03

10

.71

0.6

61

01

47

11

03

71

28

31

412

8314

Zrc

_77

_09

90

.53

0.0

84

32

1.0

02

.60

86

01

.08

0.2

24

64

0.4

20

.40

13

06

51

30

38

13

00

19

1300

19Z

rc_2

6_0

38

0.4

30

.08

46

01

.50

2.5

02

80

1.5

60

.21

50

70

.44

0.2

81

25

65

12

73

11

13

06

27

1306

27Z

rc_4

8_0

64

1.5

30

.08

45

90

.93

2.5

74

70

1.0

10

.22

10

00

.39

0.3

81

28

75

12

93

71

30

61

713

0617

Zrc

_69

_08

90

.35

0.0

84

94

0.7

72

.59

93

00

.83

0.2

22

09

0.3

40

.39

12

93

41

30

06

13

14

15

1314

15Z

rc_1

1_0

20

0.6

40

.08

51

11

.10

2.6

97

40

1.2

00

.23

00

50

.48

0.3

91

33

56

13

28

91

31

81

913

1819

Zrc

_37

_05

10

.20

0.0

85

11

0.8

02

.71

16

00

.87

0.2

31

17

0.3

50

.40

13

41

41

33

26

13

18

14

1318

14Z

rc_7

1_0

92

0.2

50

.08

51

70

.79

2.6

86

20

0.8

50

.22

88

00

.32

0.3

91

32

84

13

25

61

31

91

513

1915

Zrc

_01

_00

80

.27

0.0

85

43

1.5

32

.66

92

41

.66

0.2

26

60

0.4

50

.34

13

17

51

32

01

21

32

52

713

2527

Zrc

_87

_11

10

.50

0.0

85

65

1.0

02

.87

22

01

.09

0.2

43

41

0.4

30

.39

14

04

51

37

58

13

30

19

1330

19

Con

tinue

don

next

page

...


Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_02

_00

90

.26

0.0

87

51

1.1

02

.83

16

01

.20

0.2

35

09

0.4

80

.41

13

61

61

36

49

13

72

19

1372

19Z

rc_9

5_1

20

0.2

70

.08

98

30

.83

2.9

28

00

0.9

50

.23

65

50

.46

0.4

81

36

96

13

89

71

42

21

614

2216

Zrc

_42

_05

70

.40

0.0

90

45

0.7

82

.65

16

00

.89

0.2

12

79

0.4

00

.46

12

44

51

31

57

14

35

14

1435

14Z

rc_3

0_0

42

0.4

00

.09

06

70

.92

3.1

29

70

0.9

90

.25

05

30

.37

0.3

81

44

15

14

40

81

44

01

614

4016

Zrc

_41

_05

60

.27

0.0

90

89

0.8

33

.20

96

00

.93

0.2

56

43

0.4

20

.46

14

72

61

45

97

14

44

14

1444

14Z

rc_4

0_0

54

0.2

00

.09

18

50

.87

2.9

41

67

1.0

70

.23

22

70

.45

0.4

81

34

65

13

93

81

46

41

514

6415

Zrc

_62

_08

10

.29

0.0

92

49

0.9

93

.37

91

01

.05

0.2

65

25

0.3

60

.33

15

17

51

50

08

14

77

19

1477

19Z

rc_2

0_0

30

0.1

90

.09

26

90

.83

3.3

63

60

0.9

20

.26

34

80

.39

0.4

21

50

85

14

96

71

48

21

414

8214

Zrc

_91

_11

60

.17

0.0

93

03

0.8

93

.43

71

00

.98

0.2

68

25

0.4

20

.42

15

32

61

51

38

14

88

17

1488

17Z

rc_7

3_0

94

0.3

70

.09

36

30

.85

3.2

23

80

0.9

60

.24

98

20

.45

0.4

61

43

86

14

63

71

50

11

615

0116

Zrc

_34

_04

70

.34

0.0

95

27

0.8

93

.36

21

01

.07

0.2

56

26

0.5

90

.55

14

71

81

49

68

15

33

15

1533

15Z

rc_1

00

_12

60

.22

0.0

95

44

1.0

53

.57

21

81

.17

0.2

71

46

0.4

10

.45

15

48

61

54

39

15

37

18

1537

18Z

rc_9

2_1

17

0.5

30

.09

67

20

.78

3.5

54

00

0.8

50

.26

67

50

.33

0.4

01

52

44

15

39

71

56

21

415

6214

Zrc

_49

_06

50

.21

0.0

98

35

0.9

93

.75

92

01

.06

0.2

77

68

0.3

90

.38

15

80

51

58

49

15

93

17

1593

17Z

rc_7

9_1

01

0.4

60

.09

84

00

.80

3.6

77

80

0.8

80

.27

13

30

.37

0.4

11

54

85

15

67

71

59

41

515

9415

Zrc

_89

_11

30

.38

0.0

98

64

0.8

13

.81

13

00

.88

0.2

80

37

0.3

50

.39

15

93

51

59

57

15

99

15

1599

15Z

rc_1

7_0

27

0.6

20

.09

89

20

.97

3.9

33

80

1.1

60

.28

86

00

.63

0.5

41

63

59

16

21

91

60

41

716

0417

Zrc

_90

_11

40

.32

0.0

99

48

1.0

03

.91

22

01

.09

0.2

85

72

0.4

40

.41

16

20

61

61

69

16

14

18

1614

18

Con

tinue

don

next

page

...


Tabl

a4

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-4

86

A.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_32

_04

50

.55

0.1

10

98

0.7

54

.99

47

00

.93

0.3

26

76

0.5

50

.59

18

23

91

81

88

18

16

12

1816

12

Tabl

a5

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-8

1.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_44

_05

91

.73

0.0

85

70

2.2

10

.40

64

72

.37

0.0

35

12

0.8

80

.37

22

32

34

67

13

31

41

22

32

Zrc

_90

_11

40

.44

0.0

57

25

5.4

00

.34

15

76

.14

0.0

43

27

1.7

30

.32

27

35

29

81

65

01

11

827

35

Zrc

_06

_01

40

.52

0.0

53

63

2.2

90

.32

90

22

.37

0.0

44

51

0.5

80

.25

28

12

28

96

35

65

128

12

Zrc

_67

_08

70

.34

0.0

54

10

13

.11

0.3

34

03

14

.03

0.0

44

78

1.4

30

.25

28

24

29

33

63

75

28

528

24

Zrc

_23

_03

40

.72

0.0

52

80

1.5

90

.32

86

21

.70

0.0

45

03

0.5

80

.35

28

42

28

94

32

03

628

42

Zrc

_65

_08

40

.44

0.0

52

80

2.2

90

.32

90

42

.39

0.0

45

18

0.6

40

.28

28

52

28

96

32

05

128

52

Zrc

_05

_01

20

.49

0.0

53

60

2.2

90

.33

55

22

.39

0.0

45

30

0.6

60

.28

28

62

29

46

35

45

128

62

Zrc

_34

_04

70

.63

0.0

48

62

10

.02

0.3

04

53

10

.44

0.0

45

43

0.9

00

.10

28

63

27

02

51

29

21

02

86

3

Zrc

_03

_01

00

.56

0.0

57

14

1.5

10

.36

11

21

.58

0.0

45

73

0.5

00

.31

28

81

31

34

49

73

328

81

Zrc

_51

_06

80

.46

0.0

54

92

6.9

90

.34

67

17

.35

0.0

45

78

0.8

10

.21

28

92

30

21

94

09

15

428

92

Zrc

_36

_05

00

.79

0.0

56

94

2.7

90

.36

39

02

.95

0.0

46

40

0.9

30

.32

29

23

31

58

48

96

129

23

Con

tinue

don

next

page

...


Tabl

a5

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-8

1.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_52

_06

90

.51

0.0

56

31

1.9

00

.36

37

12

.13

0.0

46

38

0.9

70

.45

29

23

31

56

46

54

129

23

Zrc

_54

_07

10

.44

0.0

55

80

2.0

10

.35

72

12

.09

0.0

46

35

0.6

00

.28

29

22

31

06

44

44

329

22

Zrc

_83

_10

60

.34

0.0

56

39

2.5

00

.36

38

12

.58

0.0

46

81

0.6

20

.24

29

52

31

57

46

85

529

52

Zrc

_09

_01

70

.50

0.0

51

39

2.8

00

.33

19

72

.91

0.0

46

98

0.7

90

.27

29

62

29

17

25

86

429

62

Zrc

_38

_05

20

.33

0.0

53

32

2.0

10

.34

74

22

.20

0.0

47

10

0.9

10

.41

29

73

30

36

34

24

529

73

Zrc

_88

_11

20

.11

0.0

54

14

2.2

00

.35

30

82

.29

0.0

47

25

0.6

60

.29

29

82

30

76

37

74

929

82

Zrc

_58

_07

60

.13

0.0

53

30

1.8

00

.34

92

11

.87

0.0

47

40

0.5

10

.27

29

91

30

45

34

23

929

91

Zrc

_72

_09

30

.34

0.0

52

47

1.9

40

.34

32

62

.33

0.0

47

44

0.7

20

.50

29

92

30

06

30

64

329

92

Zrc

_11

_02

00

.60

0.0

52

30

1.4

00

.34

65

31

.48

0.0

48

02

0.4

80

.33

30

21

30

24

29

93

130

21

Zrc

_04

_01

10

.60

0.0

53

07

1.5

10

.35

46

51

.56

0.0

48

36

0.4

30

.26

30

41

30

84

33

23

430

41

Zrc

_12

_02

10

.35

0.0

52

70

2.5

00

.35

14

62

.57

0.0

48

31

0.6

20

.23

30

42

30

67

31

65

630

42

Zrc

_02

_00

90

.59

0.0

52

86

1.6

10

.35

51

31

.69

0.0

48

60

0.5

30

.30

30

62

30

94

32

33

830

62

Zrc

_85

_10

80

.28

0.0

59

94

1.8

00

.40

24

01

.88

0.0

48

56

0.5

40

.28

30

62

34

35

60

13

83

06

2

Zrc

_95

_12

00

.30

0.0

52

84

1.6

10

.35

53

31

.70

0.0

48

66

0.5

80

.32

30

62

30

95

32

23

630

62

Zrc

_40

_05

40

.52

0.0

52

45

1.9

10

.35

33

92

.01

0.0

48

74

0.6

60

.32

30

72

30

75

30

54

230

72

Zrc

_63

_08

20

.75

0.0

53

95

2.3

00

.36

38

42

.40

0.0

48

71

0.6

80

.28

30

72

31

56

36

95

030

72

Zrc

_92

_11

70

.47

0.0

57

74

1.7

00

.38

77

91

.79

0.0

48

70

0.5

50

.31

30

72

33

35

52

03

730

72

Zrc

_14

_02

30

.56

0.0

53

49

1.7

90

.36

14

31

.90

0.0

48

91

0.5

90

.32

30

82

31

35

35

04

030

82

Con

tinue

don

next

page

...


Tabl

a5

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-8

1.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_27

_03

90

.37

0.0

51

48

2.1

00

.34

80

32

.21

0.0

48

97

0.6

90

.32

30

82

30

36

26

24

830

82

Zrc

_75

_09

60

.58

0.0

54

56

3.7

40

.36

86

64

.20

0.0

49

01

0.9

00

.29

30

83

31

91

23

94

83

308

3Z

rc_8

7_1

11

0.5

30

.05

60

81

.60

0.3

79

35

1.7

20

.04

89

40

.63

0.3

73

08

23

27

54

56

35

308

2Z

rc_2

0_0

30

0.3

60

.05

19

91

.50

0.3

52

53

1.5

70

.04

90

90

.47

0.2

93

09

13

07

42

85

34

309

1Z

rc_2

9_0

41

0.4

80

.05

34

62

.10

0.3

62

49

2.1

80

.04

90

80

.57

0.2

83

09

23

14

63

48

47

309

2Z

rc_5

0_0

66

0.5

50

.05

44

12

.79

0.3

67

85

2.8

90

.04

90

50

.69

0.2

53

09

23

18

83

88

61

309

2Z

rc_1

5_0

24

0.3

90

.05

27

32

.60

0.3

57

94

2.6

90

.04

92

10

.67

0.2

63

10

23

11

73

17

59

310

2Z

rc_3

5_0

48

0.5

10

.05

19

11

.60

0.3

53

81

1.7

00

.04

94

10

.59

0.3

43

11

23

08

52

81

36

311

2Z

rc_1

8_0

28

0.5

00

.05

12

01

.60

0.3

50

85

1.7

00

.04

96

00

.58

0.3

43

12

23

05

42

50

36

312

2Z

rc_2

6_0

38

0.6

10

.05

40

12

.50

0.3

68

69

2.6

00

.04

95

70

.73

0.2

83

12

23

19

73

71

56

312

2Z

rc_5

3_0

70

0.5

20

.05

21

31

.59

0.3

58

58

1.7

00

.04

98

30

.58

0.3

53

13

23

11

52

91

35

313

2Z

rc_8

1_1

04

0.3

90

.05

28

61

.89

0.3

65

16

1.9

90

.04

99

00

.60

0.3

23

14

23

16

53

23

42

314

2Z

rc_7

1_0

92

0.7

80

.05

19

71

.50

0.3

59

29

1.5

90

.05

00

30

.54

0.3

43

15

23

12

42

84

34

315

2Z

rc_0

1_0

08

0.4

40

.05

23

21

.80

0.3

62

58

1.9

30

.05

02

10

.70

0.3

63

16

23

14

52

99

43

316

2Z

rc_8

2_1

05

0.2

70

.05

34

72

.00

0.3

71

95

2.0

90

.05

03

60

.62

0.3

03

17

23

21

63

49

45

317

2Z

rc_2

1_0

32

0.5

20

.05

23

31

.80

0.3

61

50

3.0

00

.05

05

42

.39

0.8

03

18

73

13

83

00

40

318

7Z

rc_5

6_0

74

0.4

30

.05

56

81

.90

0.3

88

48

1.9

70

.05

05

40

.51

0.2

63

18

23

33

64

40

41

318

2Z

rc_5

9_0

77

0.3

50

.05

38

72

.41

0.3

75

36

2.7

80

.05

05

40

.77

0.3

53

18

23

24

83

66

53

318

2

Con

tinue

don

next

page

...


Tabl

a5

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-8

1.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_70

_09

00

.28

0.0

53

84

2.1

50

.37

51

92

.39

0.0

50

54

0.6

50

.31

31

82

32

37

36

44

831

82

Zrc

_93

_11

80

.45

0.0

52

89

1.8

00

.36

98

31

.90

0.0

50

64

0.5

90

.32

31

82

32

05

32

44

031

82

Zrc

_07

_01

50

.55

0.0

55

20

2.5

70

.39

13

22

.92

0.0

51

41

0.7

60

.38

32

32

33

58

42

05

732

32

Zrc

_91

_11

60

.33

0.0

54

03

1.7

00

.38

34

71

.78

0.0

51

42

0.5

30

.29

32

32

33

05

37

23

832

32

Zrc

_33

_04

60

.69

0.0

55

94

2.0

90

.39

99

12

.31

0.0

51

76

0.9

50

.42

32

53

34

27

45

04

632

53

Zrc

_41

_05

60

.72

0.0

53

70

1.8

10

.38

55

92

.00

0.0

51

98

0.8

80

.43

32

73

33

16

35

83

932

73

Zrc

_42

_05

70

.39

0.0

60

44

6.6

30

.43

57

16

.92

0.0

52

28

0.7

10

.13

32

92

36

72

16

20

14

13

29

2

Zrc

_61

_08

00

.33

0.0

57

08

2.5

90

.41

12

82

.73

0.0

52

28

0.8

40

.32

32

93

35

08

49

55

532

93

Zrc

_94

_11

90

.44

0.0

60

11

5.1

90

.47

21

17

.14

0.0

56

97

2.7

60

.68

35

71

03

93

23

60

71

12

357

10Z

rc_7

4_0

95

0.1

90

.05

78

81

.83

0.5

13

17

2.0

00

.06

43

00

.58

0.3

14

02

24

21

75

25

39

402

2Z

rc_3

2_0

45

1.2

10

.05

56

41

.20

0.5

61

24

1.3

10

.07

30

20

.52

0.3

94

54

24

52

54

38

26

454

2Z

rc_1

9_0

29

0.3

30

.06

29

11

.61

0.6

38

35

2.4

10

.07

33

01

.80

0.7

54

56

85

01

10

70

53

445

68

Zrc

_89

_11

30

.43

0.0

70

07

1.8

00

.77

36

23

.24

0.0

77

38

2.7

00

.83

48

01

35

82

14

93

03

64

80

13

Zrc

_45

_06

00

.26

0.0

56

89

1.3

00

.60

98

11

.41

0.0

77

57

0.5

40

.38

48

23

48

35

48

72

848

23

Zrc

_66

_08

60

.31

0.0

68

34

2.4

00

.80

17

74

.00

0.0

80

10

3.2

00

.80

49

71

55

98

18

87

94

84

97

15

Zrc

_69

_08

90

.24

0.0

63

60

1.7

90

.73

05

82

.11

0.0

81

11

1.1

00

.53

50

35

55

79

72

83

750

35

Zrc

_68

_08

80

.27

0.0

67

36

2.8

10

.78

27

83

.18

0.0

83

62

1.4

90

.47

51

87

58

71

48

49

57

51

87

Zrc

_43

_05

80

.19

0.0

58

97

1.4

90

.68

33

81

.57

0.0

83

91

0.4

60

.31

51

92

52

96

56

63

151

92

Con

tinue

don

next

page

...


Tabl

a5

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-8

1.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_16

_02

60

.88

0.0

59

09

1.6

90

.75

45

21

.79

0.0

92

49

0.5

50

.32

57

03

57

18

57

03

657

03

Zrc

_76

_09

80

.25

0.0

62

04

2.0

00

.84

77

72

.90

0.0

93

77

2.1

00

.72

57

81

26

23

14

67

64

257

812

Zrc

_60

_07

80

.18

0.0

67

70

1.3

01

.06

17

01

.59

0.1

13

01

0.9

20

.58

69

06

73

58

85

92

669

06

Zrc

_47

_06

30

.57

0.0

66

74

2.0

81

.18

94

42

.46

0.1

29

25

0.6

70

.41

78

45

79

61

48

30

42

784

5Z

rc_8

0_1

02

0.2

80

.07

04

51

.41

1.2

81

80

1.7

00

.13

08

50

.96

0.5

67

93

78

38

10

94

22

879

37

Zrc

_73

_09

40

.22

0.0

67

87

1.1

11

.25

74

01

.70

0.1

33

23

1.3

00

.76

80

61

08

27

10

86

52

280

610

Zrc

_10

_01

80

.05

0.0

72

58

0.9

91

.35

90

91

.11

0.1

35

82

0.5

20

.43

82

14

87

16

10

02

20

821

4Z

rc_3

1_0

44

0.3

90

.06

89

01

.20

1.3

38

10

1.3

10

.14

05

50

.52

0.3

98

48

48

62

88

96

24

848

4Z

rc_8

6_1

10

0.3

50

.06

94

91

.42

1.4

90

16

1.6

90

.15

55

40

.55

0.4

39

32

59

26

10

91

32

993

25

Zrc

_55

_07

20

.42

0.0

71

51

1.9

61

.60

30

42

.26

0.1

62

59

0.6

20

.37

97

16

97

11

49

72

39

971

6Z

rc_1

7_0

27

0.3

90

.07

31

41

.09

1.7

88

50

1.1

90

.17

70

70

.45

0.3

91

05

14

10

41

81

01

82

210

1822

Zrc

_13

_02

20

.35

0.0

73

65

1.4

01

.76

04

01

.52

0.1

73

11

0.5

90

.39

10

29

61

03

11

01

03

22

810

3228

Zrc

_39

_05

30

.26

0.0

74

16

1.2

91

.75

82

11

.60

0.1

71

96

0.6

20

.51

10

23

61

03

01

01

04

62

510

4625

Zrc

_49

_06

50

.32

0.0

75

08

1.2

01

.84

75

01

.35

0.1

77

78

0.6

10

.46

10

55

61

06

39

10

71

23

1071

23Z

rc_3

0_0

42

0.2

30

.07

65

11

.01

1.9

10

90

1.0

80

.18

06

90

.41

0.3

61

07

14

10

85

71

10

82

011

0820

Zrc

_96

_12

20

.37

0.0

78

10

1.2

01

.94

18

01

.48

0.1

79

28

0.8

70

.58

10

63

91

09

61

01

14

92

311

4923

Zrc

_10

0_1

26

0.1

00

.08

14

80

.99

1.8

95

50

1.1

10

.16

78

70

.48

0.4

41

00

04

10

80

71

23

31

912

3319

Zrc

_57

_07

50

.60

0.0

82

36

2.0

02

.33

51

02

.15

0.2

05

46

0.8

00

.37

12

05

91

22

31

51

25

43

812

5438

Con

tinue

don

next

page

...


Tabl

a5

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-8

1.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_25

_03

60

.30

0.0

82

99

1.1

02

.41

16

01

.18

0.2

10

17

0.4

40

.38

12

30

51

24

69

12

69

21

1269

21Z

rc_3

7_0

51

0.3

70

.08

93

31

.00

2.9

17

70

1.1

00

.23

62

50

.45

0.4

21

36

76

13

87

81

41

11

914

1119

Zrc

_46

_06

20

.92

0.1

09

79

0.9

64

.84

97

01

.09

0.3

19

58

0.5

10

.48

17

88

81

79

49

17

96

17

1796

17

Tabl

a6

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apel

ite

TT-8

2.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_19

_02

90

.07

0.0

51

17

1.5

00

.31

54

41

.56

0.0

44

70

0.4

30

.26

28

21

27

84

24

83

428

21

Zrc

_53

_07

20

.83

0.0

53

51

2.6

90

.33

30

12

.80

0.0

45

17

0.7

50

.28

28

52

29

27

35

06

028

52

Zrc

_14

_02

30

.89

0.0

53

08

1.8

10

.33

86

21

.88

0.0

46

28

0.5

60

.28

29

22

29

65

33

24

029

22

Zrc

_09

_01

70

.45

0.0

51

75

1.7

00

.33

43

11

.94

0.0

46

92

0.9

40

.48

29

63

29

35

27

43

829

63

Zrc

_99

_12

70

.64

0.0

55

70

3.5

90

.36

20

03

.85

0.0

47

13

0.6

20

.29

29

72

31

41

04

41

77

297

2Z

rc_3

3_0

48

1.0

90

.05

31

41

.39

0.3

47

30

1.4

50

.04

73

90

.38

0.2

92

98

13

03

43

35

31

298

1Z

rc_9

7_1

25

0.7

10

.05

28

81

.70

0.3

46

72

1.7

80

.04

75

20

.53

0.2

92

99

23

02

53

24

37

299

2Z

rc_3

7_0

53

0.7

90

.05

28

52

.50

0.3

46

77

2.5

90

.04

77

00

.67

0.2

63

00

23

02

73

22

56

300

2Z

rc_9

3_1

20

0.3

70

.05

42

02

.90

0.3

57

77

3.0

00

.04

78

60

.75

0.2

63

01

23

11

83

79

63

301

2

Con

tinue

don

next

page

...


Tabl

a6

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apel

ite

TT-8

2.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_77

_10

10

.77

0.0

54

44

1.5

10

.36

05

01

.56

0.0

47

98

0.4

20

.25

30

21

31

34

38

93

430

21

Zrc

_40

_05

60

.47

0.0

51

43

2.5

10

.34

07

22

.58

0.0

48

05

0.6

20

.23

30

32

29

87

26

05

730

32

Zrc

_13

_02

20

.44

0.0

52

81

2.4

00

.35

09

32

.47

0.0

48

26

0.5

80

.23

30

42

30

57

32

15

330

42

Zrc

_69

_09

10

.58

0.0

52

23

1.9

00

.34

73

11

.98

0.0

48

21

0.5

60

.29

30

42

30

35

29

54

230

42

Zrc

_68

_09

00

.39

0.0

52

79

2.6

00

.35

25

62

.71

0.0

48

53

0.7

60

.29

30

52

30

77

32

05

730

52

Zrc

_79

_10

30

.68

0.0

52

98

1.7

00

.35

57

51

.76

0.0

48

68

0.4

50

.26

30

61

30

95

32

83

930

61

Zrc

_25

_03

80

.62

0.0

55

21

3.1

00

.36

98

13

.19

0.0

48

76

0.7

60

.24

30

72

32

09

42

16

730

72

Zrc

_73

_09

60

.60

0.0

53

06

2.6

00

.35

83

62

.70

0.0

49

12

0.7

10

.26

30

92

31

17

33

15

930

92

Zrc

_87

_11

30

.83

0.0

52

83

1.5

00

.35

78

21

.56

0.0

49

07

0.4

30

.28

30

91

31

14

32

23

430

91

Zrc

_65

_08

60

.91

0.0

54

56

1.7

00

.37

16

01

.78

0.0

49

34

0.5

10

.28

31

02

32

15

39

43

731

02

Zrc

_23

_03

60

.62

0.0

57

01

4.1

40

.39

52

44

.41

0.0

50

28

0.5

60

.26

31

62

33

81

34

92

89

316

2Z

rc_5

2_0

71

0.5

70

.05

61

41

.91

0.3

89

37

1.9

60

.05

03

60

.48

0.2

33

17

13

34

64

58

42

317

1Z

rc_9

2_1

19

0.4

90

.05

44

71

.60

0.3

78

27

1.6

50

.05

03

70

.42

0.2

63

17

13

26

53

91

35

317

1Z

rc_1

6_0

26

0.7

10

.05

57

74

.27

0.4

04

19

4.6

70

.05

25

60

.80

0.2

43

30

33

45

14

44

39

233

03

Zrc

_78

_10

20

.42

0.0

53

71

1.9

90

.38

89

52

.07

0.0

52

49

0.5

30

.28

33

02

33

46

35

94

533

02

Zrc

_70

_09

20

.87

0.0

58

08

2.7

00

.42

25

13

.03

0.0

52

76

0.5

90

.24

33

12

35

89

53

35

833

12

Zrc

_80

_10

40

.44

0.0

73

03

2.6

20

.53

70

42

.96

0.0

53

33

0.8

30

.41

33

53

43

61

01

01

55

33

35

3

Zrc

_98

_12

60

.93

0.0

51

58

2.0

00

.38

06

12

.07

0.0

53

54

0.5

20

.26

33

62

32

76

26

74

433

62

Con

tinue

don

next

page

...


Tabl

a6

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apel

ite

TT-8

2.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_67

_08

90

.60

0.0

55

89

1.8

10

.41

57

71

.87

0.0

53

69

0.5

00

.26

33

72

35

36

44

83

933

72

Zrc

_75

_09

80

.75

0.0

54

34

2.1

00

.40

56

12

.16

0.0

54

08

0.5

20

.24

34

02

34

66

38

54

734

02

Zrc

_47

_06

50

.08

0.0

52

53

1.4

10

.39

52

61

.45

0.0

54

55

0.3

80

.24

34

21

33

84

30

93

234

21

Zrc

_64

_08

50

.49

0.0

55

12

2.0

00

.41

85

82

.23

0.0

54

85

0.9

80

.44

34

43

35

57

41

74

334

43

Zrc

_27

_04

10

.76

0.0

54

56

2.1

10

.42

41

12

.37

0.0

56

05

1.1

10

.46

35

24

35

97

39

44

635

24

Zrc

_63

_08

40

.62

0.0

56

49

2.8

00

.45

35

32

.88

0.0

57

78

0.6

70

.24

36

22

38

09

47

26

036

22

Zrc

_88

_11

40

.24

0.0

54

87

1.2

90

.46

72

41

.40

0.0

61

60

0.5

00

.37

38

52

38

95

40

72

938

52

Zrc

_57

_07

70

.35

0.0

58

98

2.1

00

.58

51

33

.04

0.0

69

04

2.2

00

.72

43

09

46

81

15

66

45

430

9Z

rc_4

5_0

62

0.8

30

.05

60

31

.61

0.5

85

22

1.6

70

.07

57

20

.48

0.2

74

71

24

68

64

54

35

471

2Z

rc_4

2_0

59

0.2

40

.05

63

61

.40

0.5

96

44

1.4

60

.07

67

00

.40

0.2

74

76

24

75

64

67

31

476

2Z

rc_0

6_0

14

0.3

10

.05

87

31

.80

0.6

43

66

1.8

70

.07

95

30

.49

0.2

54

93

25

05

75

57

38

493

2Z

rc_2

2_0

35

0.6

80

.05

80

11

.40

0.6

84

03

1.4

70

.08

54

70

.44

0.3

15

29

25

29

65

30

30

529

2Z

rc_2

1_0

34

0.4

10

.05

87

81

.80

0.6

96

53

1.8

50

.08

59

70

.43

0.2

25

32

25

37

85

59

38

532

2Z

rc_1

0_0

18

0.3

70

.05

84

11

.51

0.6

97

67

1.6

80

.08

63

90

.75

0.4

45

34

45

37

75

45

32

534

4Z

rc_0

8_0

16

0.3

60

.07

08

52

.10

0.8

46

27

2.3

90

.08

66

30

.70

0.3

45

36

46

23

11

95

34

25

36

4

Zrc

_36

_05

20

.41

0.0

64

99

1.4

90

.80

32

01

.86

0.0

88

11

1.1

00

.60

54

46

59

98

77

43

154

46

Zrc

_18

_02

81

.01

0.0

59

62

1.3

90

.74

14

51

.53

0.0

89

94

0.6

30

.42

55

53

56

37

59

02

955

53

Zrc

_34

_04

90

.38

0.0

59

90

1.9

00

.76

13

71

.95

0.0

92

33

0.4

30

.21

56

92

57

59

60

04

156

92

Con

tinue

don

next

page

...


Tabl

a6

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apel

ite

TT-8

2.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_05

_01

20

.35

0.0

60

38

1.7

10

.89

49

01

.77

0.1

07

54

0.5

10

.28

65

83

64

99

61

73

665

83

Zrc

_11

_02

00

.03

0.0

61

23

1.3

10

.94

42

71

.35

0.1

11

80

0.3

60

.25

68

32

67

57

64

72

768

32

Zrc

_91

_11

80

.97

0.0

61

69

1.3

00

.95

91

41

.38

0.1

12

67

0.4

50

.33

68

83

68

37

66

32

768

83

Zrc

_43

_06

00

.67

0.0

62

29

1.6

11

.01

45

01

.68

0.1

18

17

0.5

10

.29

72

03

71

19

68

43

472

03

Zrc

_03

_01

00

.40

0.0

66

63

2.0

01

.28

23

02

.09

0.1

39

42

0.6

00

.29

84

15

83

81

28

26

40

841

5Z

rc_3

1_0

46

0.3

30

.06

99

02

.40

1.4

50

90

2.5

50

.15

05

00

.85

0.3

39

04

79

10

15

92

54

990

47

Zrc

_83

_10

80

.06

0.0

72

80

1.3

01

.51

86

01

.36

0.1

51

15

0.4

00

.28

90

73

93

88

10

08

26

907

3Z

rc_6

0_0

80

0.3

10

.06

94

51

.50

1.4

95

30

1.5

60

.15

60

50

.44

0.2

99

35

49

28

10

91

23

093

54

Zrc

_02

_00

90

.27

0.0

69

11

1.7

91

.50

93

01

.92

0.1

58

40

0.6

60

.35

94

86

93

41

29

02

36

948

6Z

rc_9

4_1

21

0.4

50

.06

99

01

.40

1.5

90

10

1.4

50

.16

48

00

.38

0.2

69

83

39

66

99

25

28

983

3Z

rc_7

1_0

94

0.2

30

.07

23

81

.20

1.7

77

00

1.2

90

.17

77

20

.46

0.3

51

05

54

10

37

89

97

24

997

24Z

rc_5

5_0

74

0.4

10

.07

26

01

.50

1.8

06

90

1.5

80

.18

02

90

.51

0.3

21

06

95

10

48

10

10

03

30

1003

30Z

rc_7

2_0

95

0.2

40

.07

30

51

.40

1.8

32

10

1.4

70

.18

18

80

.45

0.3

11

07

74

10

57

10

10

15

27

1015

27Z

rc_3

0_0

44

0.5

70

.07

31

01

.50

1.9

50

00

1.5

70

.19

33

60

.46

0.2

81

14

05

10

98

11

10

17

30

1017

30Z

rc_3

9_0

55

0.3

40

.07

33

71

.89

1.7

76

80

2.0

00

.17

58

80

.62

0.3

21

04

46

10

37

13

10

24

38

1024

38Z

rc_4

4_0

61

0.3

00

.07

33

81

.70

1.8

69

50

1.7

70

.18

47

70

.48

0.2

61

09

35

10

70

12

10

24

34

1024

34Z

rc_3

5_0

50

0.2

40

.07

33

91

.40

1.8

03

10

1.4

80

.17

83

70

.48

0.3

21

05

85

10

47

10

10

25

28

1025

28Z

rc_5

9_0

79

0.3

50

.07

35

31

.50

1.8

08

20

1.5

60

.17

81

10

.43

0.2

91

05

74

10

48

10

10

29

30

1029

30

Con

tinue

don

next

page

...


Tabl

a6

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apel

ite

TT-8

2.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_54

_07

30

.37

0.0

73

74

1.5

11

.85

49

01

.56

0.1

82

38

0.4

40

.27

10

80

41

06

51

01

03

43

010

3430

Zrc

_04

_01

10

.34

0.0

73

97

1.7

01

.86

69

01

.81

0.1

82

75

0.6

10

.33

10

82

61

06

91

21

04

13

310

4133

Zrc

_29

_04

30

.28

0.0

74

00

1.5

01

.82

73

01

.56

0.1

79

06

0.4

30

.28

10

62

41

05

51

01

04

12

910

4129

Zrc

_85

_11

00

.37

0.0

74

02

1.5

01

.66

50

01

.58

0.1

63

03

0.5

00

.32

97

45

99

51

01

04

23

010

4230

Zrc

_46

_06

40

.37

0.0

74

28

1.6

01

.87

25

01

.68

0.1

82

53

0.5

20

.31

10

81

51

07

11

11

04

93

210

4932

Zrc

_10

0_1

28

0.1

80

.07

42

91

.31

1.8

22

90

1.3

50

.17

77

20

.37

0.2

61

05

54

10

54

91

04

92

510

4925

Zrc

_76

_10

00

.26

0.0

74

46

1.4

01

.81

37

01

.51

0.1

76

51

0.5

70

.38

10

48

61

05

01

01

05

42

810

5428

Zrc

_07

_01

50

.26

0.0

74

59

1.6

01

.83

18

01

.71

0.1

78

14

0.6

00

.36

10

57

61

05

71

11

05

73

110

5731

Zrc

_96

_12

40

.48

0.0

74

87

1.5

01

.95

14

01

.57

0.1

88

67

0.4

80

.31

11

14

51

09

91

11

06

52

910

6529

Zrc

_15

_02

40

.14

0.0

75

03

1.3

12

.06

56

01

.37

0.1

99

65

0.4

40

.31

11

73

51

13

79

10

69

26

1069

26Z

rc_0

1_0

08

0.2

80

.07

62

11

.40

2.0

55

60

1.4

60

.19

56

50

.42

0.2

81

15

24

11

34

10

11

01

27

1101

27Z

rc_4

8_0

66

0.6

40

.07

71

41

.59

2.0

20

90

1.6

80

.18

98

90

.51

0.3

11

12

15

11

23

11

11

25

32

1125

32Z

rc_2

4_0

37

0.3

80

.07

74

01

.78

1.9

73

96

1.9

80

.18

49

60

.49

0.3

41

09

45

11

07

13

11

32

34

1132

34Z

rc_3

2_0

47

0.3

80

.07

75

01

.30

2.1

12

10

1.3

90

.19

75

90

.49

0.3

51

16

25

11

53

10

11

34

26

1134

26Z

rc_1

7_0

27

0.3

90

.07

75

41

.70

2.1

15

60

1.7

70

.19

78

20

.50

0.2

81

16

45

11

54

12

11

35

33

1135

33Z

rc_4

9_0

67

0.3

30

.07

78

21

.40

2.1

40

40

1.4

50

.19

92

30

.39

0.2

71

17

14

11

62

10

11

42

28

1142

28Z

rc_4

1_0

58

0.4

30

.07

80

51

.40

2.1

89

60

1.4

60

.20

34

30

.43

0.3

01

19

45

11

78

10

11

48

27

1148

27Z

rc_5

6_0

76

0.5

10

.07

82

41

.30

2.1

63

20

1.3

50

.20

03

10

.38

0.2

71

17

74

11

69

91

15

32

611

5326

Con

tinue

don

next

page

...


Tabl

a6

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apel

ite

TT-8

2.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_62

_08

30

.47

0.0

78

33

1.4

02

.20

26

01

.47

0.2

03

82

0.4

40

.29

11

96

51

18

21

01

15

52

711

5527

Zrc

_12

_02

10

.26

0.0

78

68

1.3

02

.19

53

01

.37

0.2

02

32

0.4

30

.32

11

88

51

18

01

01

16

42

511

6425

Zrc

_38

_05

40

.39

0.0

78

69

1.5

02

.17

29

01

.56

0.2

00

03

0.4

10

.26

11

75

41

17

21

11

16

42

911

6429

Zrc

_66

_08

80

.31

0.0

78

70

1.3

02

.27

64

01

.35

0.2

09

49

0.3

60

.28

12

26

41

20

51

01

16

52

511

6525

Zrc

_86

_11

20

.29

0.0

79

59

1.2

92

.22

04

01

.36

0.2

01

87

0.4

10

.31

11

85

41

18

71

01

18

72

611

8726

Zrc

_28

_04

20

.33

0.0

80

41

1.8

02

.29

12

01

.88

0.2

05

96

0.5

50

.29

12

07

61

21

01

31

20

73

512

0735

Zrc

_50

_06

80

.30

0.0

80

71

1.3

02

.44

49

01

.39

0.2

19

48

0.4

90

.35

12

79

61

25

61

01

21

42

512

1425

Zrc

_51

_07

00

.27

0.0

81

67

1.8

02

.41

27

01

.89

0.2

14

20

0.5

70

.30

12

51

61

24

61

41

23

83

512

3835

Zrc

_61

_08

20

.26

0.0

81

68

1.3

02

.53

49

01

.36

0.2

25

02

0.4

00

.30

13

08

51

28

21

01

23

82

512

3825

Zrc

_74

_09

70

.26

0.0

82

29

1.4

02

.50

11

01

.46

0.2

20

14

0.4

10

.29

12

83

51

27

21

11

25

22

712

5227

Zrc

_82

_10

70

.18

0.0

82

43

1.3

02

.48

27

01

.63

0.2

17

78

0.9

80

.60

12

70

11

12

67

12

12

56

25

1256

25Z

rc_9

0_1

16

0.5

20

.08

38

21

.40

2.3

88

40

1.4

70

.20

64

30

.45

0.3

11

21

05

12

39

11

12

88

26

1288

26Z

rc_9

5_1

22

0.4

20

.08

50

41

.51

2.7

68

00

1.5

70

.23

59

80

.48

0.2

91

36

66

13

47

12

13

16

28

1316

28Z

rc_8

1_1

06

0.3

50

.08

60

81

.41

2.7

71

00

1.4

90

.23

33

40

.52

0.3

41

35

26

13

48

11

13

40

27

1340

27Z

rc_2

6_0

40

0.4

30

.09

43

61

.20

3.5

92

80

1.2

80

.27

65

20

.44

0.3

51

57

46

15

48

10

15

15

22

1515

22Z

rc_5

8_0

78

0.8

90

.09

61

51

.30

3.8

26

70

1.3

60

.28

84

20

.41

0.3

01

63

46

15

98

11

15

51

24

1551

24Z

rc_8

9_1

15

0.1

70

.13

69

11

.20

7.9

07

40

1.2

50

.41

83

50

.36

0.2

92

25

37

22

21

11

21

88

20

2188

20Z

rc_2

0_0

30

0.4

70

.17

66

31

.30

12

.36

60

01

.36

0.5

07

43

0.3

90

.28

26

46

82

63

31

32

62

12

126

2121


Tabl

a7

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-6

12

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_72

_09

30

.21

0.0

53

89

1.2

10

.33

88

51

.27

0.0

45

84

0.4

80

.32

28

91

29

63

36

62

528

91

Zrc

_16

_02

60

.20

0.0

55

18

2.5

90

.35

04

22

.63

0.0

46

27

1.6

20

.18

29

21

30

57

42

05

729

21

Zrc

_04

_01

10

.36

0.0

57

27

4.3

00

.36

89

74

.33

0.0

46

85

1.6

60

.12

29

51

31

91

25

02

95

295

1Z

rc_4

6_0

62

0.2

80

.05

42

91

.81

0.3

56

68

1.8

70

.04

78

80

.52

0.2

63

01

13

10

53

83

41

301

1Z

rc_7

5_0

96

0.5

80

.05

63

32

.70

0.3

70

81

2.7

80

.04

79

50

.60

0.2

43

02

23

20

84

65

56

302

2Z

rc_3

8_0

52

0.5

00

.05

77

84

.29

0.3

81

98

4.3

40

.04

80

90

.77

0.1

53

03

23

28

12

52

19

530

32

Zrc

_54

_07

10

.44

0.0

58

99

3.3

10

.38

84

53

.36

0.0

48

08

0.6

20

.18

30

32

33

31

05

67

72

303

2Z

rc_3

0_0

42

0.4

60

.05

98

35

.20

0.3

97

36

5.2

50

.04

82

31

.22

0.1

43

04

23

40

15

59

71

12

30

42

Zrc

_53

_07

00

.64

0.0

53

65

1.3

00

.35

67

81

.36

0.0

48

45

0.4

30

.29

30

51

31

04

35

62

930

51

Zrc

_71

_09

20

.49

0.0

57

18

3.3

90

.37

90

93

.45

0.0

48

56

0.6

80

.18

30

62

32

61

04

99

70

306

2Z

rc_9

0_1

14

0.8

90

.05

73

42

.30

0.3

82

20

2.3

40

.04

86

50

.49

0.1

93

06

13

29

75

05

47

306

1Z

rc_6

5_0

84

0.8

40

.05

54

51

.70

0.3

71

43

1.7

80

.04

88

50

.41

0.3

03

07

23

21

54

30

35

307

2Z

rc_1

8_0

28

0.8

00

.05

61

72

.71

0.3

77

13

2.7

30

.04

89

60

.47

0.1

43

08

13

25

84

59

59

308

1Z

rc_5

5_0

72

0.5

80

.05

63

42

.59

0.3

77

82

2.6

60

.04

88

60

.51

0.2

33

08

23

25

74

66

58

308

2Z

rc_7

0_0

90

0.9

40

.05

37

21

.51

0.3

61

64

1.5

80

.04

91

00

.45

0.3

03

09

23

13

43

59

32

309

2Z

rc_8

5_1

08

0.9

50

.05

60

61

.80

0.3

76

98

1.8

50

.04

90

90

.45

0.2

23

09

13

25

54

55

37

309

1Z

rc_8

2_1

05

0.3

00

.05

50

41

.71

0.3

71

61

1.7

70

.04

92

00

.53

0.2

53

10

13

21

54

14

36

310

1Z

rc_9

_01

70

.69

0.0

56

49

2.0

00

.38

19

72

.05

0.0

49

32

0.4

90

.22

31

01

32

86

47

24

131

01

Con

tinue

don

next

page

...


Tabl

a7

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-6

12

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_96

_12

20

.87

0.0

54

27

1.3

10

.36

64

81

.38

0.0

49

21

0.3

90

.31

31

01

31

74

38

22

731

01

Zrc

_3_0

10

0.8

40

.05

93

72

.80

0.4

04

03

2.8

50

.04

94

81

.52

0.2

03

11

23

45

85

81

60

311

2Z

rc_3

5_0

48

0.7

20

.06

16

69

.78

0.4

19

89

10

.40

0.0

49

39

0.3

40

.14

31

13

35

63

16

62

21

63

11

3

Zrc

_17

_02

70

.41

0.0

58

18

2.7

00

.39

69

62

.76

0.0

49

73

0.6

40

.21

31

32

33

98

53

75

831

32

Zrc

_27

_03

90

.73

0.0

55

89

1.5

00

.38

22

31

.56

0.0

49

83

0.4

20

.26

31

31

32

94

44

83

331

31

Zrc

_05

_01

20

.41

0.0

58

60

3.6

00

.40

37

93

.67

0.0

50

14

1.1

80

.19

31

52

34

41

15

52

79

315

2Z

rc_0

8_0

16

0.8

20

.06

04

62

.50

0.4

17

20

2.5

60

.05

01

00

.96

0.2

13

15

23

54

86

20

50

31

52

Zrc

_29

_04

10

.64

0.0

58

62

3.5

10

.40

48

13

.84

0.0

50

09

0.2

00

.22

31

52

34

51

15

53

71

315

2Z

rc_1

0_0

18

0.4

70

.05

42

91

.60

0.3

74

29

1.6

90

.05

01

60

.50

0.3

23

16

23

23

53

83

35

316

2Z

rc_4

8_0

64

0.5

70

.05

87

23

.00

0.4

05

09

3.0

70

.05

02

10

.68

0.2

23

16

23

45

95

57

66

316

2Z

rc_5

6_0

74

0.4

80

.06

27

14

.10

0.4

32

88

4.1

50

.05

02

51

.23

0.1

63

16

23

65

13

69

88

13

16

2

Zrc

_14

_02

30

.54

0.0

57

46

3.1

00

.39

80

63

.14

0.0

50

55

0.7

70

.17

31

82

34

09

50

96

731

82

Zrc

_66

_08

60

.58

0.0

60

54

3.0

40

.42

15

43

.38

0.0

50

50

0.2

00

.28

31

82

35

71

06

23

61

31

82

Zrc

_57

_07

50

.48

0.0

56

53

2.0

00

.39

30

22

.09

0.0

50

65

0.6

70

.29

31

92

33

76

47

34

131

92

Zrc

_76

_09

80

.66

0.0

54

42

1.4

00

.37

88

71

.46

0.0

50

81

0.4

10

.30

31

91

32

64

38

82

931

91

Zrc

_31

_04

40

.83

0.0

55

24

1.5

00

.39

01

91

.56

0.0

51

53

0.4

10

.26

32

41

33

54

42

23

432

41

Zrc

_58

_07

61

.08

0.0

58

31

1.7

00

.41

37

71

.85

0.0

51

76

0.6

60

.40

32

52

35

26

54

13

532

52

Zrc

_59

_07

70

.79

0.0

53

39

1.5

90

.37

96

11

.67

0.0

51

88

0.4

40

.30

32

61

32

75

34

53

432

61

Con

tinue

don

next

page

...


Tabl

a7

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-6

12

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_50

_06

60

.17

0.0

54

92

2.0

20

.40

18

32

.27

0.0

53

07

0.2

30

.37

33

32

34

37

40

94

633

32

Zrc

_81

_10

40

.59

0.0

60

33

2.7

00

.44

03

62

.79

0.0

53

21

0.6

00

.24

33

42

37

19

61

55

433

42

Zrc

_78

_10

00

.37

0.0

57

69

1.9

90

.43

18

22

.07

0.0

54

58

0.6

80

.27

34

32

36

46

51

84

134

32

Zrc

_02

_00

90

.07

0.0

57

68

3.6

90

.43

40

93

.76

0.0

54

86

3.7

40

.19

34

42

36

61

25

18

80

344

2Z

rc_2

8_0

40

0.1

80

.05

83

12

.09

0.5

43

41

2.1

60

.06

79

00

.87

0.2

54

23

24

41

85

41

45

423

2Z

rc_6

3_0

82

0.8

00

.05

85

11

.01

0.6

06

60

1.0

80

.07

55

30

.38

0.3

74

69

24

81

45

49

20

469

2Z

rc_2

1_0

32

0.6

80

.05

95

71

.49

0.6

68

55

1.5

80

.08

16

60

.47

0.3

35

06

25

20

65

88

32

506

2Z

rc_8

6_1

10

0.1

70

.05

80

11

.29

0.6

49

89

1.3

80

.08

16

80

.59

0.3

45

06

25

08

65

30

26

506

2Z

rc_9

1_1

16

0.8

60

.06

14

21

.81

0.7

33

27

1.8

90

.08

70

30

.47

0.3

05

38

35

58

86

54

36

538

3Z

rc_4

0_0

54

0.1

70

.06

38

42

.30

0.8

39

05

2.3

60

.09

58

21

.34

0.2

15

90

36

19

11

73

64

959

03

Zrc

_97

_12

30

.95

0.0

63

20

2.1

00

.83

16

52

.19

0.0

96

25

0.4

70

.28

59

24

61

51

07

15

41

592

4Z

rc_4

5_0

60

0.8

60

.06

12

10

.78

0.8

19

20

0.9

70

.09

74

10

.40

0.5

95

99

36

08

46

47

17

599

3Z

rc_1

9_0

29

0.9

30

.06

05

81

.40

0.8

18

73

1.4

60

.09

84

60

.58

0.2

86

05

26

07

76

24

30

605

2Z

rc_3

9_0

53

0.1

40

.06

07

71

.00

0.8

26

30

1.0

70

.09

89

40

.59

0.3

46

08

26

12

56

31

22

608

2Z

rc_7

4_0

95

1.1

00

.06

20

81

.30

0.8

58

90

1.3

80

.10

09

20

.41

0.3

26

20

36

30

66

77

26

620

3Z

rc_0

1_0

08

0.8

10

.06

15

51

.80

0.8

65

68

1.8

60

.10

23

40

.43

0.2

36

28

36

33

96

59

38

628

3Z

rc_4

4_0

59

0.1

60

.07

16

81

.31

1.1

61

40

1.8

80

.11

75

20

.32

0.6

77

16

77

83

10

97

72

771

67

Zrc

_84

_10

70

.47

0.0

65

05

0.8

11

.05

84

00

.92

0.1

18

45

0.4

10

.46

72

23

73

35

77

61

672

23

Con

tinue

don

next

page

...


Tabl

a7

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-6

12

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_61

_08

00

.42

0.0

65

32

2.0

11

.09

07

02

.07

0.1

21

69

0.4

40

.25

74

04

74

91

17

85

39

740

4Z

rc_9

5_1

20

0.0

90

.07

17

20

.73

1.5

63

30

0.8

40

.15

88

30

.51

0.5

09

50

49

56

59

78

14

950

4Z

rc_3

4_0

47

0.1

80

.07

14

70

.80

1.5

97

00

1.1

00

.16

25

30

.70

0.6

99

71

79

69

79

71

16

971

7Z

rc_2

2_0

33

0.2

70

.07

30

20

.97

1.8

31

30

1.0

70

.18

24

60

.42

0.4

21

08

04

10

57

71

01

51

910

1519

Zrc

_77

_09

90

.34

0.0

73

04

1.0

01

.67

33

01

.10

0.1

66

88

0.4

10

.42

99

54

99

87

10

15

19

1015

19Z

rc_1

00

_12

60

.29

0.0

73

65

1.1

01

.74

53

01

.18

0.1

72

76

0.4

00

.37

10

27

41

02

58

10

32

22

1032

22Z

rc_8

0_1

02

0.6

00

.07

36

90

.83

1.7

39

70

0.9

00

.17

20

40

.37

0.4

01

02

33

10

23

61

03

31

610

3316

Zrc

_87

_11

10

.17

0.0

74

70

3.7

61

.65

14

83

.97

0.1

60

35

0.2

30

.21

95

96

99

02

51

06

07

010

6070

Zrc

_49

_06

50

.29

0.0

74

86

1.4

01

.84

82

01

.46

0.1

79

87

0.5

30

.28

10

66

41

06

31

01

06

52

810

6528

Zrc

_89

_11

30

.08

0.0

75

11

0.6

71

.74

22

30

.80

0.1

68

23

0.1

20

.52

10

02

41

02

45

10

71

12

1071

12Z

rc_3

6_0

50

0.2

50

.07

54

21

.50

1.8

51

00

1.7

00

.17

85

90

.60

0.4

81

05

98

10

64

11

10

80

30

1080

30Z

rc_1

1_0

20

0.4

00

.07

56

21

.90

1.6

77

20

1.9

40

.16

15

80

.58

0.1

99

66

31

00

01

21

08

53

810

8538

Zrc

_07

_01

50

.25

0.0

76

34

0.8

12

.05

10

00

.92

0.1

95

39

0.4

40

.46

11

51

51

13

36

11

04

15

1104

15Z

rc_9

3_1

18

0.1

90

.07

64

51

.50

1.8

84

60

1.5

80

.18

00

00

.67

0.3

11

06

75

10

76

11

11

07

28

1107

28Z

rc_9

9_1

25

0.0

80

.07

66

14

.33

1.6

92

31

4.6

50

.16

02

20

.37

0.2

59

58

81

00

63

01

11

18

011

1180

Zrc

_62

_08

10

.30

0.0

76

67

1.7

01

.91

84

01

.77

0.1

82

39

0.5

80

.29

10

80

51

08

81

21

11

33

211

1332

Zrc

_69

_08

90

.27

0.0

76

79

0.7

61

.85

84

00

.92

0.1

76

28

0.3

90

.57

10

47

51

06

66

11

16

14

1116

14Z

rc_3

7_0

51

0.5

60

.07

69

11

.00

2.0

36

80

1.0

90

.19

27

50

.40

0.3

91

13

64

11

28

71

11

92

011

1920

Con

tinue

don

next

page

...


Tabl

a7

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-6

12

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_06

_01

40

.44

0.0

77

45

1.3

91

.93

08

01

.51

0.1

81

42

0.6

00

.39

10

75

61

09

21

01

13

32

611

3326

Zrc

_92

_11

70

.26

0.0

77

64

1.8

01

.91

53

01

.90

0.1

79

86

0.7

20

.32

10

66

61

08

61

31

13

83

311

3833

Zrc

_25

_03

60

.14

0.0

77

95

1.1

02

.06

24

01

.16

0.1

92

70

1.3

60

.32

11

36

41

13

68

11

46

22

1146

22Z

rc_8

3_1

06

0.3

90

.07

80

91

.10

1.8

55

20

1.1

70

.17

29

80

.40

0.3

41

02

94

10

65

81

14

92

011

4920

Zrc

_68

_08

80

.31

0.0

78

36

1.6

01

.98

34

01

.67

0.1

84

31

0.7

40

.30

10

90

51

11

01

11

15

62

911

5629

Zrc

_15

_02

40

.14

0.0

78

68

1.1

92

.22

34

01

.28

0.2

05

89

0.8

60

.36

12

07

51

18

89

11

64

23

1164

23Z

rc_2

6_0

38

0.7

70

.07

88

90

.99

2.1

62

10

1.0

60

.19

93

60

.37

0.3

71

17

24

11

69

71

16

91

911

6919

Zrc

_41

_05

60

.69

0.0

80

34

1.1

02

.24

59

01

.18

0.2

03

70

0.4

80

.37

11

95

51

19

68

12

05

22

1205

22Z

rc_5

2_0

69

0.2

10

.08

03

60

.71

2.3

20

90

0.8

10

.21

01

30

.38

0.4

81

23

04

12

19

61

20

61

412

0614

Zrc

_13

_02

20

.32

0.0

80

93

0.8

02

.33

51

00

.88

0.2

09

85

0.3

70

.41

12

28

41

22

36

12

20

16

1220

16Z

rc_2

4_0

35

1.2

50

.08

11

81

.40

2.3

07

70

1.4

90

.20

68

10

.36

0.3

31

21

26

12

15

11

12

26

27

1226

27Z

rc_5

1_0

68

0.3

00

.08

14

90

.99

2.1

99

90

1.0

90

.19

66

00

.43

0.4

11

15

75

11

81

81

23

32

012

3320

Zrc

_79

_10

10

.27

0.0

81

64

0.7

52

.46

65

00

.84

0.2

20

16

0.3

70

.46

12

83

41

26

26

12

37

14

1237

14Z

rc_4

2_0

57

0.4

60

.08

32

01

.90

2.3

57

50

1.9

60

.20

63

20

.66

0.2

61

20

96

12

30

14

12

74

37

1274

37Z

rc_9

4_1

19

0.3

20

.08

33

11

.30

2.4

85

07

1.6

00

.21

63

40

.17

0.5

21

26

27

12

68

12

12

77

23

1277

23Z

rc_6

7_0

87

0.3

90

.08

67

11

.20

2.7

58

30

1.2

90

.23

16

40

.42

0.3

71

34

36

13

44

10

13

54

22

1354

22Z

rc_2

3_0

34

0.1

60

.08

70

70

.88

2.9

60

60

0.9

80

.24

75

40

.52

0.4

31

42

65

13

98

71

36

21

713

6217

Zrc

_60

_07

80

.29

0.0

88

38

1.1

02

.94

34

01

.20

0.2

42

81

0.6

00

.40

14

01

61

39

39

13

91

20

1391

20

Con

tinue

don

next

page

...


Tabl

a7

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

met

apsa

mm

ite

TT-6

12

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_43

_05

80

.58

0.0

97

20

0.6

93

.75

43

00

.78

0.2

81

04

0.3

50

.46

15

97

51

58

36

15

71

13

1571

13Z

rc_6

4_0

83

0.4

00

.09

76

40

.76

3.5

53

00

0.9

40

.26

50

80

.43

0.5

91

51

67

15

39

71

58

01

315

8013

Zrc

_47

_06

30

.36

0.1

12

27

0.8

05

.04

42

00

.94

0.3

26

37

0.3

70

.53

18

21

81

82

78

18

36

15

1836

15Z

rc_3

2_0

45

0.1

80

.13

57

30

.71

5.9

67

11

0.9

60

.31

88

40

.16

0.6

41

78

49

19

71

82

17

31

221

7312

Zrc

_98

_12

40

.48

0.1

86

09

0.7

21

2.1

05

00

0.9

10

.47

39

80

.36

0.6

12

50

11

22

61

39

27

08

11

2708

11

Tabl

a8

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

gran

ite

dike

TT-6

15

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_24

_03

50

.46

0.0

61

40

2.3

10

.38

56

02

.57

0.0

45

55

0.5

30

.40

28

71

33

17

65

34

82

87

1

Zrc

_6_0

14

0.7

40

.05

49

71

.80

0.3

49

50

1.8

70

.04

60

70

.50

0.2

72

90

13

04

54

11

36

290

1Z

rc_3

1_0

44

0.5

20

.06

01

71

.65

0.3

83

66

2.0

10

.04

62

50

.65

0.4

32

91

23

30

66

10

35

29

12

Zrc

_36

_05

00

.26

0.0

55

40

2.4

70

.35

68

02

.69

0.0

46

71

0.6

40

.30

29

42

31

07

42

85

529

42

Zrc

_11

_02

00

.33

0.0

54

86

2.2

10

.35

65

62

.27

0.0

47

07

0.5

50

.23

29

72

31

06

40

74

829

72

Zrc

_02

_00

90

.25

0.0

52

87

1.1

00

.34

62

11

.20

0.0

47

39

0.4

60

.40

29

81

30

23

32

32

429

81

Zrc

_29

_04

10

.49

0.0

58

33

4.9

20

.38

24

95

.26

0.0

47

56

0.8

60

.24

30

03

32

91

55

42

10

730

03

Con

tinue

don

next

page

...


Tabl

a8

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

gran

ite

dike

TT-6

15

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_71

_09

10

.33

0.0

59

19

2.5

00

.38

82

53

.07

0.0

47

57

1.0

50

.59

30

03

33

39

57

45

330

03

Zrc

_35

_04

81

.37

0.0

55

02

1.1

10

.36

30

61

.56

0.0

47

85

1.1

10

.70

30

13

31

44

41

32

430

13

Zrc

_66

_08

60

.53

0.0

51

40

1.1

10

.34

08

01

.18

0.0

47

95

0.4

20

.33

30

21

29

83

25

92

330

21

Zrc

_45

_06

00

.52

0.0

52

04

1.1

90

.34

56

91

.28

0.0

48

12

0.4

40

.36

30

31

30

13

28

72

730

31

Zrc

_51

_06

80

.51

0.0

53

38

0.9

40

.35

61

71

.01

0.0

48

29

0.3

90

.38

30

41

30

93

34

51

930

41

Zrc

_46

_06

20

.44

0.0

54

72

2.2

50

.36

61

12

.45

0.0

48

53

0.5

40

.24

30

52

31

77

40

15

030

52

Zrc

_15

_02

40

.69

0.0

56

25

1.3

00

.38

05

21

.37

0.0

49

02

0.4

50

.32

30

91

32

74

46

22

830

91

Zrc

_25

_03

60

.49

0.0

59

70

1.8

90

.40

50

82

.19

0.0

49

12

1.1

00

.51

30

93

34

56

59

34

03

09

3

Zrc

_16

_02

60

.53

0.0

57

38

4.9

80

.39

12

05

.20

0.0

49

45

0.5

50

.12

31

12

33

51

55

06

10

731

12

Zrc

_17

_02

70

.52

0.0

58

39

3.1

00

.39

83

33

.30

0.0

49

48

0.5

70

.20

31

12

34

01

05

44

65

311

2Z

rc_5

7_0

75

0.6

60

.06

15

42

.39

0.4

20

05

2.6

60

.04

95

00

.65

0.3

03

11

23

56

86

58

46

31

12

Zrc

_60

_07

80

.95

0.0

61

24

1.5

00

.41

79

31

.56

0.0

49

40

0.4

50

.28

31

11

35

55

64

82

93

11

1

Zrc

_05

_01

20

.46

0.0

60

45

9.7

80

.41

31

21

0.0

80

.04

95

70

.99

0.1

23

12

33

51

30

62

01

92

31

23

Zrc

_65

_08

40

.59

0.0

56

90

3.0

10

.38

82

33

.05

0.0

49

56

0.5

20

.17

31

22

33

39

48

86

031

22

Zrc

_18

_02

80

.69

0.0

62

30

2.3

00

.42

64

82

.50

0.0

49

69

0.9

70

.39

31

33

36

18

68

44

73

13

3

Zrc

_38

_05

20

.71

0.0

52

99

1.4

00

.36

57

61

.45

0.0

49

95

0.3

60

.27

31

41

31

74

32

83

131

41

Zrc

_50

_06

60

.56

0.0

56

92

1.7

00

.39

46

31

.77

0.0

50

32

0.5

00

.27

31

62

33

85

48

83

431

62

Zrc

_64

_08

30

.53

0.0

61

88

4.0

20

.43

07

14

.23

0.0

50

48

0.7

30

.21

31

72

36

41

36

70

78

31

72

Con

tinue

don

next

page

...


Tabl

a8

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

gran

ite

dike

TT-6

15

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_37

_05

10

.58

0.0

53

77

1.3

00

.37

55

51

.35

0.0

50

57

0.3

60

.26

31

81

32

44

36

12

931

81

Zrc

_56

_07

40

.63

0.0

61

85

2.3

90

.43

47

12

.48

0.0

51

00

0.6

10

.26

32

12

36

78

66

94

63

21

2

Zrc

_44

_05

90

.51

0.0

59

50

1.3

90

.42

04

71

.49

0.0

51

21

0.5

10

.35

32

22

35

64

58

53

032

22

Zrc

_63

_08

20

.51

0.0

57

59

1.6

00

.40

73

91

.67

0.0

51

19

0.4

70

.29

32

21

34

75

51

43

232

21

Zrc

_62

_08

10

.74

0.0

55

46

1.1

00

.39

39

51

.18

0.0

51

43

0.4

30

.36

32

31

33

73

43

12

232

31

Zrc

_01

_00

80

.45

0.0

52

39

1.3

00

.37

29

21

.36

0.0

51

57

0.4

10

.30

32

41

32

24

30

22

932

41

Zrc

_28

_04

00

.98

0.0

59

60

4.6

50

.42

40

65

.11

0.0

51

61

0.8

30

.26

32

43

35

91

55

89

10

032

43

Zrc

_39

_05

30

.93

0.0

54

45

1.8

90

.38

78

01

.95

0.0

51

56

0.4

50

.25

32

41

33

36

39

04

232

41

Zrc

_59

_07

70

.42

0.0

56

63

3.0

00

.40

52

03

.14

0.0

51

89

0.6

00

.21

32

62

34

59

47

76

032

62

Zrc

_33

_04

60

.57

0.0

59

57

4.1

80

.43

25

74

.45

0.0

52

66

0.7

40

.19

33

12

36

51

45

88

90

331

2Z

rc_3

4_0

47

0.6

40

.05

34

61

.50

0.3

89

54

1.5

90

.05

27

70

.53

0.3

43

32

23

34

53

48

33

332

2Z

rc_2

1_0

32

1.0

60

.05

51

31

.40

0.4

05

22

1.6

20

.05

33

30

.81

0.5

03

35

33

45

54

17

30

335

3Z

rc_5

4_0

71

0.7

10

.07

70

01

1.8

70

.56

71

71

2.4

40

.05

34

21

.55

0.1

83

35

54

56

46

11

21

21

63

35

5

Zrc

_43

_05

80

.70

0.0

59

97

1.8

00

.47

70

91

.93

0.0

57

50

0.7

10

.37

36

02

39

66

60

33

936

02

Zrc

_30

_04

20

.65

0.0

61

72

1.3

00

.69

83

61

.42

0.0

81

96

0.5

60

.40

50

83

53

86

66

42

750

83

Zrc

_32

_04

50

.37

0.0

63

81

1.3

00

.76

54

81

.35

0.0

86

90

0.3

80

.28

53

72

57

76

73

52

753

72

Zrc

_08

_01

60

.60

0.0

61

04

1.0

00

.75

04

71

.06

0.0

89

05

0.3

60

.34

55

02

56

85

64

12

155

02

Zrc

_03

_01

00

.19

0.0

60

81

1.9

10

.76

64

91

.98

0.0

91

49

0.5

50

.26

56

43

57

89

63

34

156

43

Con

tinue

don

next

page

...


Tabl

a8

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

gran

ite

dike

TT-6

15

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_26

_03

80

.28

0.0

63

85

1.1

00

.80

77

91

.18

0.0

91

58

0.4

40

.38

56

52

60

15

73

72

356

52

Zrc

_58

_07

60

.56

0.0

61

91

1.1

00

.82

18

81

.17

0.0

96

14

0.4

10

.35

59

22

60

95

67

12

159

22

Zrc

_20

_03

00

.21

0.0

61

62

0.8

60

.88

17

40

.94

0.1

03

65

0.3

80

.40

63

62

64

24

66

11

863

62

Zrc

_52

_06

90

.44

0.0

79

66

1.4

11

.42

97

01

.59

0.1

29

52

0.7

50

.47

78

56

90

19

11

89

25

78

56

Zrc

_69

_08

90

.18

0.0

71

76

0.7

21

.44

98

30

.83

0.1

46

52

0.3

20

.42

88

13

91

05

97

91

488

13

Zrc

_41

_05

60

.15

0.0

72

33

1.3

01

.64

72

01

.37

0.1

64

83

0.4

40

.32

98

44

98

89

99

52

698

44

Zrc

_10

_01

80

.07

0.0

70

42

0.7

01

.60

68

00

.75

0.1

65

12

0.3

00

.38

98

53

97

35

94

11

498

53

Zrc

_04

_01

10

.42

0.0

74

60

1.3

01

.82

97

01

.35

0.1

77

37

0.3

70

.27

10

53

41

05

69

10

58

26

1058

26Z

rc_2

2_0

33

0.5

50

.07

46

81

.10

1.8

99

70

1.1

90

.18

42

70

.46

0.3

91

09

05

10

81

81

06

02

110

6021

Zrc

_48

_06

40

.12

0.0

75

09

1.3

11

.85

50

01

.38

0.1

79

00

0.4

50

.32

10

62

41

06

59

10

71

24

1071

24Z

rc_4

7_0

63

0.2

70

.07

93

60

.84

2.2

60

80

0.9

10

.20

61

80

.32

0.3

71

20

84

12

00

61

18

11

511

8115

Zrc

_09

_01

70

.25

0.0

79

48

0.8

12

.25

32

00

.91

0.2

05

12

0.4

20

.47

12

03

51

19

86

11

84

16

1184

16Z

rc_5

5_0

72

0.2

70

.07

97

90

.95

2.2

50

60

1.0

10

.20

41

60

.33

0.3

21

19

84

11

97

71

19

21

711

9217

Zrc

_72

_09

20

.33

0.0

79

80

1.0

02

.18

68

01

.09

0.1

98

36

0.4

40

.40

11

67

51

17

78

11

92

19

1192

19Z

rc_1

3_0

22

0.4

80

.08

00

80

.87

2.2

10

90

0.9

50

.19

98

70

.39

0.4

01

17

54

11

84

71

19

91

711

9917

Zrc

_42

_05

70

.35

0.0

80

19

1.4

02

.19

08

01

.58

0.1

98

15

0.4

90

.34

11

65

51

17

81

11

20

22

712

0227

Zrc

_70

_09

00

.24

0.0

80

88

1.2

21

.99

66

51

.37

0.1

79

04

0.4

70

.35

10

62

51

11

49

12

19

24

1219

24Z

rc_2

3_0

34

0.3

00

.08

12

00

.76

2.4

88

90

0.8

20

.22

19

80

.30

0.3

61

29

24

12

69

61

22

61

412

2614

Con

tinue

don

next

page

...


Tabl

a8

:LA

-IC

P-M

SU

-Pb

isot

opic

data

for

Teco

mat

eFo

rmat

ion

gran

ite

dike

TT-6

15

.

Spot

nam

eT

h/U

Isot

opic

rati

os(e

rror

sin

%)

Age

s(M

a)

207

Pb/206

Pb1σ

207

Pb/235

U1σ

206

Pb/238

U1σ

Rho

206

Pb/238

U1σ

207

Pb/235

U1σ

207

Pb/206

U1σ

Best

age1σ

Zrc

_53

_07

00

.29

0.0

81

42

1.4

12

.22

24

31

.58

0.1

97

96

0.5

60

.40

11

64

61

18

81

11

23

22

512

3225

Zrc

_40

_05

40

.36

0.0

81

71

0.7

32

.45

49

00

.81

0.2

17

45

0.3

50

.42

12

68

41

25

96

12

39

14

1239

14Z

rc_4

9_0

65

0.1

00

.08

52

50

.75

2.5

68

50

1.2

60

.21

85

10

.96

0.7

91

27

41

11

29

29

13

21

13

1321

13Z

rc_6

1_0

80

0.7

80

.08

61

41

.20

2.1

86

40

1.3

10

.18

37

60

.53

0.4

11

08

75

11

77

91

34

12

113

4121

Zrc

_12

_02

10

.65

0.0

94

30

0.8

03

.48

90

00

.87

0.2

67

89

0.3

50

.41

15

30

51

52

57

15

14

14

1514

14Z

rc_1

4_0

23

0.5

40

.15

20

30

.63

8.4

84

73

0.8

80

.40

47

60

.45

0.6

02

19

18

22

84

82

36

91

023

6910

Zrc

_27

_03

90

.21

0.1

75

80

0.7

01

0.5

93

97

0.8

60

.43

70

70

.43

0.5

22

33

88

24

88

82

61

41

126

1411

Tabl

a9

:Ti-

in-z

irco

nth

erm

omet

ryfo

rro

cks

ofth

eTo

tolt

epec

plut

on.

Sam

ple

Age

Con

cord

ance

Ti(p

pm)

log(

Ti)

T(◦

C)

Sam

ple

Age

Con

cord

ance

Ti(p

pm)

log(

Ti)

T(◦

C)

TT-7

6B(Q

uart

zD

iori

te)

TT-7

2(H

ornb

lend

eG

abbr

o)

Zrc

_56_0

74

278

0.3

621

.18

1.3

3811

.54

Zrc

_19_0

29

299

1.6

43

.25

0.5

1651

.04

Zrc

_52_0

69

285

0.7

013

.42

1.1

3767

.48

Zrc

_21_0

32

299

0.6

65

.97

0.7

8697

.61

Zrc

_57_0

75

285

1.3

81

.20

0.0

8583

.65

Zrc

_02_0

09

301

-0.3

318.9

71

.28

800

.54

Zrc

_47_0

63

286

0.0

06

.01

0.7

8698

.13

Zrc

_05_0

12

302

7.9

39

.13

0.9

6733

.02

Con

tinue

don

next

page

...


Tabl

a9

:Ti-

in-z

irco

nth

erm

omet

ryfo

rro

cks

ofth

eTo

tolt

epec

plut

on.

Sam

ple

Age

Con

cord

ance

Ti(p

pm)

log(

Ti)

T(◦

C)

Sam

ple

Age

Con

cord

ance

Ti(p

pm)

log(

Ti)

T(◦

C)

TT-7

6B(Q

uart

zD

iori

te)

TT-7

2(H

ornb

lend

eG

abbr

o)

Zrc

_76_0

98

286

1.7

21

.52

0.1

8598

.65

Zrc

_10_0

18

302

5.3

34

.22

0.6

3670

.43

Zrc

_79_1

01

286

4.0

33

.00

0.4

8645

.14

Zrc

_17_0

27

302

1.3

15

.65

0.7

5693

.14

Zrc

_59_0

77

287

2.7

12

.01

0.3

0617

.09

Zrc

_01_0

08

303

1.6

214

.03

1.1

5771

.62

Zrc

_70_0

90

288

1.0

33

.66

0.5

6659

.74

Zrc

_03_0

10

303

3.5

06

.08

0.7

8699

.05

Zrc

_74_0

95

288

-0.7

09.1

30

.96

733

.04

Zrc

_38_0

50

303

-1.3

413.4

71

.13

767

.85

Zrc

_46_0

62

289

0.3

46

.88

0.8

4709

.09

Zrc

_04_0

11

304

2.2

57

.18

0.8

6712

.65

Zrc

_64_0

83

289

3.6

712

.41

1.0

9760

.32

Zrc

_35_0

46

304

-0.3

35.6

60

.75

693

.29

Zrc

_69_0

89

289

2.0

320

.83

1.3

2809

.86

Zrc

_32_0

44

305

2.8

74

.94

0.6

9682

.53

Zrc

_78_1

00

289

3.0

21

.01

0.0

1573

.16

Zrc

_07_0

15

306

1.6

14

.33

0.6

4672

.41

Zrc

_72_0

93

290

-0.6

97.6

20

.88

717

.59

Zrc

_08_0

16

306

0.9

715

.85

1.2

0783.1

2

Zrc

_48_0

64

291

0.3

414

.48

1.1

6774

.61

Zrc

_12

_021

306

2.2

45

.51

0.7

4691.1

2

Zrc

_55_0

72

291

1.3

622

.78

1.3

6818

.88

Zrc

_16_0

26

306

3.7

77

.75

0.8

9719.0

1

Zrc

_58_0

76

292

0.3

42

.04

0.3

1618

.06

Zrc

_22_0

33

306

-0.9

99.6

10

.98

737.4

7

Zrc

_68_0

88

293

1.0

19

.14

0.9

6733

.16

Zrc

_27_0

38

306

2.5

510

.19

1.0

1742.6

5

Zrc

_75_0

96

293

1.6

86

.04

0.7

8698

.49

Zrc

_13_0

22

307

2.5

416

.04

1.2

1784.2

9

Zrc

_77_0

99

293

0.0

012

.04

1.0

8757

.58

Zrc

_29_0

40

308

-1.9

98.9

00

.95

730.8

2

Con

tinue

don

next

page

...


Tabl

a9

:Ti-

in-z

irco

nth

erm

omet

ryfo

rro

cks

ofth

eTo

tolt

epec

plut

on.

Sam

ple

Age

Con

cord

ance

Ti(p

pm)

log(

Ti)

T(◦

C)

Sam

ple

Age

Con

cord

ance

Ti(p

pm)

log(

Ti)

T(◦

C)

TT-7

6B(Q

uart

zD

iori

te)

TT-7

2(H

ornb

lend

eG

abbr

o)

Zrc

_80_1

02

294

1.0

14

.03

0.6

1666

.95

Zrc

_37_0

49

308

1.2

814

.40

1.1

6774

.04

Zrc

_50_0

66

295

1.0

18

.88

0.9

5730

.61

Zrc

_20_0

30

309

2.5

27

.94

0.9

0721

.05

Zrc

_53_0

70

295

-0.6

82.3

80

.38

628

.83

Zrc

_30_0

41

309

0.3

214

.84

1.1

7776

.91

Zrc

_71_0

92

297

1.0

010

.61

1.0

3746

.19

Zrc

_36_0

48

309

0.3

214

.88

1.1

7777

.18

Zrc

_51_0

68

300

-0.3

36.1

30

.79

699

.74

Zrc

_06_0

14

310

8.2

87

.37

0.8

7714

.83

Zrc

_62_0

81

301

-1.0

120.0

91

.30

806

.24

Zrc

_26_0

37

310

6.3

411

.12

1.0

5750

.38

Zrc

_73_0

94

307

-0.9

91.0

30

.01

574

.06

Zrc

_41_0

53

310

0.6

416

.02

1.2

0784

.18

Zrc

_45_0

60

310

1.2

712

.45

1.1

0760

.62

Zrc

_11_0

20

311

3.1

21

.25

0.1

0586

.28

Zrc

_15_0

24

311

4.0

110

.26

1.0

1743

.27

MED

IAN

713.

34M

EDIA

N73

0.82

STD

EV76

.04

STD

EV48

.77

CTA B L A S G E O Q U Í M I C A

Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Solari, L.A., 2012, Permian–Carboniferousarc magmatism and basin evolution along the western margin of Pangea:geochemical and geochronological evidence from the eastern AcatlánComplex, southern Mexico: Geological Society of America Bulletin, enprensa, doi: 10.1130/B30649.1.

117

tablas geoquímica 118

Tabl

a1

0:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t1

/3).

Nam

eT

T-11

TT-

12T

T-13

AT

T-13

BT

T-14

TT-

15T

T-16

TT-

18T

T-20

TT-

22T

T-24

Lat

18.2

28

36

61

8.2

14

11

61

8.2

14

03

31

8.2

14

03

31

8.2

08

43

31

8.2

23

06

61

8.2

22

76

61

8.2

57

38

31

8.2

60

23

31

8.2

63

01

61

8.2

78

83

3

Lon

-97.8

59

43

-97.8

83

7-9

7.8

83

85

-97.8

83

85

-97.8

90

86

6-9

7.8

99

78

3-9

7.9

00

5-9

7.8

505

33

-97

.83

86

33

-97.8

32

43

3-9

7.7

99

4

Lith

olog

ytr

ondh

j.Q

zgr

anit

oid

tona

l.to

nal.

hbld

iori

teto

nal.

tron

dhj.

tron

dhj.

tron

dhj.

tron

dhj.

hblg

abbr

o

Age

(Ma)

28

92

89

28

92

89

28

92

89

28

93

06

28

930

63

06

SiO2

(wt%

)7

0.6

77

.56

0.2

55

.45

1.1

52.3

73

.17

0.1

71

.767

.64

6.0

TiO2

0.2

30

.10

0.6

10

.76

0.7

80.7

20

.19

0.2

40

.17

0.3

10

.31

Al 2

O3

16.8

13

.91

6.3

15

.82

3.6

16.2

15

.01

6.7

15

.316

.12

1.3

Fe2

O3

1.6

60

.17

8.2

21

1.6

5.7

01

1.4

0.9

21.6

01.1

02.9

58

.13

MnO

0.0

30

.02

20.1

47

0.2

25

0.0

71

0.1

90

.04

10

.036

0.0

41

0.0

76

0.1

49

MgO

0.7

00.1

12

.79

3.9

82

.43

6.1

30

.54

0.6

70

.33

1.8

48

.36

CaO

2.6

92.1

96

.69

7.0

39

.65

4.6

21.0

62.3

02

.40

2.2

38

.63

Na 2

O5.4

95.4

43

.72

3.6

25

.22

4.1

26.2

05

.97

5.5

55

.48

1.9

9

K2

O0.7

00.2

50

.48

0.4

20

.22

1.1

41.2

81

.00

0.7

61

.16

1.3

5

P 2O5

0.0

70.0

10

.10

0.0

90

.25

0.1

00.0

60

.07

0.0

50

.11

0.0

1

LOI

1.0

70.3

20.7

51

.02

1.0

21

.28

1.2

21

.71

2.6

02

.16

3.7

7

Tota

l1

00.0

10

0.0

10

0.0

10

0.0

10

0.0

98.2

99.5

10

0.4

100

.01

00

.01

00

.0

Mg#

42.9

53.5

37.7

37

.94

3.2

48

.95

1.1

42

.734

.852

.66

4.7

V(p

pm)

29

10

16

62

88

11

12

72

82

42

26

51

50

Cr

10

15

20

71

21

01

61

32

72

63

Co

41

17

27

13

45

34

84

3

Ni

55

78

95

56

51

07

6

Cu

21

10

45

81

11

21

16

23

Zn

41

76

81

04

55

43

39

19

21

51

66

Ga

18

15

14

16

26

18

18

15

15

16

14

Con

tinue

don

next

page

...


Tabl

a1

0:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t1

/3).

Nam

eT

T-11

TT-

12T

T-13

AT

T-13

BT

T-14

TT-

15T

T-16

TT-

18T

T-20

TT-

22T

T-24

Lat

18.2

28

36

61

8.2

14

11

61

8.2

14

03

31

8.2

14

03

31

8.2

08

43

31

8.2

23

06

61

8.2

22

76

61

8.2

57

38

31

8.2

60

23

31

8.2

63

01

61

8.2

78

83

3

Lon

-97.8

59

43

-97.8

83

7-9

7.8

83

85

-97.8

83

85

-97.8

90

86

6-9

7.8

99

78

3-9

7.9

00

5-9

7.8

505

33

-97

.83

86

33

-97.8

32

43

3-9

7.7

99

4

Lith

olog

ytr

ondh

j.Q

zgr

anit

oid

tona

l.to

nal.

hbld

iori

teto

nal.

tron

dhj.

tron

dhj.

tron

dhj.

tron

dhj.

hblg

abbr

o

Age

(Ma)

28

92

89

28

92

89

28

92

89

28

93

06

28

930

63

06

Rb

14

39

80

27

27

30

17

25

28

Sr7

08

33

12

87

26

51

12

96

91

62

93

28

32

356

94

01

Y4

39

266

42

88

75

Zr

73

4259

4869

73

754

54

657

3

Nb

0.0

0.1

2.0

3.6

1.3

0.0

1.1

0.0

0.0

2.4

0.1

Ba

52

712

426

118

211

55

59

400

78

047

714

0483

6

Cs

0.0

1.8

4.3

0.3

0.0

1.8

0.0

0.0

0.0

0.0

8.7

La1.

54.

46.

43.

51.

86.

30.

9

Ce

11.8

2.7

9.7

15.4

8.9

9.0

3.7

12.4

6.6

12.8

1.9

Pr0.

31.

22.

21.

50.

41.

60.

3

Nd

0.9

6.1

9.5

8.7

1.6

7.1

1.2

Sm0.

21.

42.

82.

10.

51.

80.

6

Eu0.

20.

60.

80.

90.

20.

40.

4

Gd

0.3

2.0

4.0

1.9

0.5

1.4

0.6

Tb

0.07

0.26

0.69

0.26

0.09

0.22

0.13

Dy

0.4

1.9

4.7

1.3

0.5

1.3

1.0

Ho

0.09

0.39

1.03

0.23

0.11

0.28

0.19

Er0.

41.

23.

10.

60.

20.

90.

6

Tm

0.06

0.18

0.49

0.08

0.07

0.09

0.08

Yb

0.4

1.2

3.1

0.5

0.3

0.8

0.8

Con

tinue

don

next

page

...


Tabl

a1

0:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t1

/3).

Nam

eT

T-11

TT-

12T

T-13

AT

T-13

BT

T-14

TT-

15T

T-16

TT-

18T

T-20

TT-

22T

T-24

Lat

18.2

28

36

61

8.2

14

11

61

8.2

14

03

31

8.2

14

03

31

8.2

08

43

31

8.2

23

06

61

8.2

22

76

61

8.2

57

38

31

8.2

60

23

31

8.2

63

01

61

8.2

78

83

3

Lon

-97.8

59

43

-97.8

83

7-9

7.8

83

85

-97.8

83

85

-97.8

90

86

6-9

7.8

99

78

3-9

7.9

00

5-9

7.8

505

33

-97

.83

86

33

-97.8

32

43

3-9

7.7

99

4

Lith

olog

ytr

ondh

j.Q

zgr

anit

oid

tona

l.to

nal.

hbld

iori

teto

nal.

tron

dhj.

tron

dhj.

tron

dhj.

tron

dhj.

hblg

abbr

o

Age

(Ma)

28

92

89

28

92

89

28

92

89

28

93

06

28

930

63

06

Lu0.

040.

140.

480.

070.

040.

080.

10

Hf

3.9

1.2

1.3

1.5

1.7

1.3

0.1

Ta0.

000.

050.

100.

030.

030.

040.

00

Pb0.2

10.5

12.1

9.3

0.0

0.0

0.0

2.0

5.0

4.4

11.2

Th

0.3

0.5

1.4

0.1

0.2

1.0

0.0

U0.0

0.8

1.5

1.7

0.0

0.3

0.0

0.2

1.9

0.0

0.0

Tabl

a1

1:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t2

/3).

Nam

eT

T-25

TT-

26A

TT-

26B

TT-

27T

T-28

TT-

49T

T-50

TT-

51T

T-52

TT-

53T

T-54

Lat

18.2

66

66

61

8.2

59

71

8.2

59

71

8.2

60

51

8.2

60

11

61

8.2

29

31

61

8.2

32

68

31

8.2

35

43

31

8.2

29

218.2

20

31

8.2

20

78

3

Lon

-97.7

88

78

3-9

7.7

81

15

-97.7

81

15

-97

.78

27

33

-97.7

83

45

-97.8

05

51

6-9

7.8

12

46

6-9

7.8

265

5-9

7.8

38

38

3-9

7.8

78

51

6-9

7.8

78

56

6

Lith

olog

ytr

ondh

j.hb

lleu

coga

bbro

hblg

abbr

otr

ondh

j.H

bl-i

tetr

ondh

j.tr

ondh

j.Pl

cum

ul.

Plcu

mul

.tr

ondh

j.to

nal.

Age

(Ma)

28

93

06

30

63

06

30

62

89

28

92

89

28

92

89

28

9

SiO2

(wt%

)7

1.6

44.7

47.3

75.7

40

.76

8.3

69

.166

.46

2.7

69.1

52.2

TiO2

0.1

80.1

80.2

40

.11

0.9

60.2

40

.21

0.2

50

.26

0.2

60.6

7

Al 2

O3

15.7

29.5

19.1

14.6

18

.71

6.2

16

.419.6

18

.617.1

17.5

Fe2

O3

1.1

92.7

97

.55

0.2

81

2.3

1.6

01

.26

1.0

51

.22

1.8

01

1.1

Con

tinue

don

next

page

...


Tabl

a1

1:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t2

/3).

Nam

eT

T-25

TT-

26A

TT-

26B

TT-

27T

T-28

TT-

49T

T-50

TT-

51T

T-52

TT-

53T

T-54

Lat

18.2

66

66

61

8.2

59

71

8.2

59

71

8.2

60

51

8.2

60

11

61

8.2

29

31

61

8.2

32

68

31

8.2

35

43

31

8.2

29

218.2

20

31

8.2

20

78

3

Lon

-97.7

88

78

3-9

7.7

81

15

-97.7

81

15

-97

.78

27

33

-97.7

83

45

-97.8

05

51

6-9

7.8

12

46

6-9

7.8

265

5-9

7.8

38

38

3-9

7.8

78

51

6-9

7.8

78

56

6

Lith

olog

ytr

ondh

j.hb

lleu

coga

bbro

hblg

abbr

otr

ondh

j.H

bl-i

tetr

ondh

j.tr

ondh

j.Pl

cum

ul.

Plcu

mul

.tr

ondh

j.to

nal.

Age

(Ma)

28

93

06

30

63

06

30

62

89

28

92

89

28

92

89

28

9

MnO

0.0

29

0.0

57

0.1

65

0.0

18

0.1

80

0.0

32

0.0

29

0.0

22

0.0

44

0.0

39

0.2

16

MgO

0.5

92.3

79

.79

0.2

41

0.9

50

.33

0.2

10.2

11

.06

0.7

44.7

9

CaO

1.6

11

4.4

89.0

50

.88

11

.34.6

43

.54

0.4

82

.14

3.2

97.9

3

Na 2

O5

.41

1.3

41

.96

5.8

31

.35

5.0

15

.83

11.2

81

0.3

35.6

03.7

7

K2

O0.9

71

.27

1.3

01

.93

0.6

80.4

00

.47

0.2

50

.22

0.7

70.5

3

P 2O5

0.0

50

.03

0.0

10

.05

0.0

20.0

70

.06

0.0

70

.08

0.0

80.0

8

LOI

2.6

43

.32

3.5

50

.38

2.8

73

.27

2.9

80.4

93

.29

1.2

41.2

7

Tota

l1

00.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

100

.01

00.0

10

0.0

10

0.0

Mg#

46.9

60

.26

9.8

60

.46

1.4

26

.92

2.9

26.3

60

.84

2.3

43.6

V(p

pm)

21

66

11

41

04

34

29

28

27

32

30

27

0

Cr

12

10

33

13

16

64

81

36

13

10

5

Co

11

13

60

47

42

11

32

4

Ni

64

31

63

36

24

64

76

13

Cu

22

23

82

97

32

12

45

0

Zn

73

17

78

63

33

19

422

49

98

Ga

13

18

14

15

15

19

16

15

13

19

18

Rb

18

44

35

32

22

81

07

61

51

1

Sr3

48

56

95

15

16

82

70

59

15

39

198

21

38

74

22

9

Y3

25

410

52

52

53

8

Zr

52

24

1111

72

58

70

857

84

4

Con

tinue

don

next

page

...


Tabl

a1

1:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t2

/3).

Nam

eT

T-25

TT-

26A

TT-

26B

TT-

27T

T-28

TT-

49T

T-50

TT-

51T

T-52

TT-

53T

T-54

Lat

18.2

66

66

61

8.2

59

71

8.2

59

71

8.2

60

51

8.2

60

11

61

8.2

29

31

61

8.2

32

68

31

8.2

35

43

31

8.2

29

218.2

20

31

8.2

20

78

3

Lon

-97.7

88

78

3-9

7.7

81

15

-97.7

81

15

-97

.78

27

33

-97.7

83

45

-97.8

05

51

6-9

7.8

12

46

6-9

7.8

265

5-9

7.8

38

38

3-9

7.8

78

51

6-9

7.8

78

56

6

Lith

olog

ytr

ondh

j.hb

lleu

coga

bbro

hblg

abbr

otr

ondh

j.H

bl-i

tetr

ondh

j.tr

ondh

j.Pl

cum

ul.

Plcu

mul

.tr

ondh

j.to

nal.

Age

(Ma)

28

93

06

30

63

06

30

62

89

28

92

89

28

92

89

28

9

Nb

0.0

0.2

0.2

0.4

0.4

0.0

0.0

0.0

0.4

0.0

3.9

Ba

66

281

293

679

256

23

95

34

886

705

61

65

7

Cs

3.8

7.2

10

.31

.50.0

1.5

3.1

3.5

3.6

4.6

6.9

La1.

30.

81.

00.

91.

9

Ce

15

.52.

72.

02.

53.

21

0.1

2.6

12

.34.

11

1.1

9.5

Pr0.

30.

30.

30.

60.

5

Nd

1.2

1.5

1.1

3.8

2.0

Sm0.

40.

40.

41.

60.

4

Eu0.

30.

30.

10.

70.

3

Gd

0.4

0.8

0.5

2.1

0.6

Tb

0.05

0.13

0.07

0.33

0.05

Dy

0.4

0.9

0.7

2.2

0.4

Ho

0.11

0.19

0.15

0.42

0.12

Er0.

40.

60.

51.

10.

3

Tm

0.06

0.08

0.06

0.18

0.04

Yb

0.3

0.5

0.5

1.0

0.4

Lu0.

040.

080.

080.

130.

05

Hf

0.1

0.2

0.5

0.6

2.4

Ta0.

000.

000.

010.

000.

01

Pb3.3

4.9

0.0

13.1

6.6

0.0

10

.96.7

1.5

0.0

6.0

Con

tinue

don

next

page

...


Tabl

a1

1:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t2

/3).

Nam

eT

T-25

TT-

26A

TT-

26B

TT-

27T

T-28

TT-

49T

T-50

TT-

51T

T-52

TT-

53T

T-54

Lat

18.2

66

66

61

8.2

59

71

8.2

59

71

8.2

60

51

8.2

60

11

61

8.2

29

31

61

8.2

32

68

31

8.2

35

43

31

8.2

29

218.2

20

31

8.2

20

78

3

Lon

-97.7

88

78

3-9

7.7

81

15

-97.7

81

15

-97

.78

27

33

-97.7

83

45

-97.8

05

51

6-9

7.8

12

46

6-9

7.8

265

5-9

7.8

38

38

3-9

7.8

78

51

6-9

7.8

78

56

6

Lith

olog

ytr

ondh

j.hb

lleu

coga

bbro

hblg

abbr

otr

ondh

j.H

bl-i

tetr

ondh

j.tr

ondh

j.Pl

cum

ul.

Plcu

mul

.tr

ondh

j.to

nal.

Age

(Ma)

28

93

06

30

63

06

30

62

89

28

92

89

28

92

89

28

9

Th

0.0

0.1

0.4

0.1

0.3

U0.0

4.2

0.0

2.3

2.0

0.0

0.7

1.3

3.0

0.0

0.1

Tabl

a1

2:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t3

/3).

Nam

eT

T-55

TT-

56T

T-57

TT-

59T

T-60

TT-

72T

T-73

TT-

74T

T-76

BT

T-77

TT-

78T

T-79

Lat

18.2

15

86

61

8.2

16

31

61

8.2

08

31

61

8.2

07

43

31

8.2

00

56

61

8.2

58

11

8.2

50

21

8.2

39

418.2

286

518

.22

31

66

18.2

18

65

18.2

20

95

Lon

-97.8

80

85

-97.8

80

55

-97.8

80

45

-97.8

74

9-9

7.8

86

95

-97.8

51

63

3-9

7.8

49

71

6-9

7.8

50

45

-97.8

63

43

3-9

7.8

68

-97.8

68

06

6-9

7.8

88

3

Lith

olog

yto

nal.

tron

dhj.

tron

dhj.

tona

l.to

nal.

hblg

abbr

otr

ondh

j.tr

ondh

j.qu

artz

dior

ite

tron

dhj.

tona

l.qu

artz

dior

ite

Age

(Ma)

28

92

89

28

92

89

28

93

06

28

92

89

28

92

89

28

92

89

SiO2

(wt%

)5

1.9

66

.86

9.1

54

.34

9.8

48

.07

2.9

69

.96

8.6

68.6

52

.56

9.8

TiO2

0.7

70

.35

0.2

60

.71

0.8

60

.79

0.2

00.2

30

.26

0.2

70

.67

0.2

4

Al 2

O3

22.7

17

.51

7.5

17

.22

0.6

17

.51

6.3

16.5

16

.51

7.4

23

.41

7.0

Fe2

O3

5.8

82

.43

1.8

49

.68

6.6

91

0.5

0.5

61.5

31

.86

1.8

65

.37

1.5

6

MnO

0.0

81

0.0

43

0.0

37

0.1

85

0.0

74

0.1

31

0.0

17

0.0

29

0.0

33

0.0

41

0.0

75

0.0

34

MgO

3.1

01

.36

0.7

24

.20

3.8

05.2

20.2

20.2

10

.95

0.9

72

.17

0.7

4

CaO

7.3

83

.33

3.7

76

.23

7.2

57.8

50.2

43.0

22

.53

2.9

68

.29

1.8

5

Na 2

O5

.53

5.6

95

.39

2.7

66

.47

3.4

47

.83

5.4

76

.46

5.4

75

.45

6.5

0

Con

tinue

don

next

page

...


Tabl

a1

2:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t3

/3).

Nam

eT

T-55

TT-

56T

T-57

TT-

59T

T-60

TT-

72T

T-73

TT-

74T

T-76

BT

T-77

TT-

78T

T-79

Lat

18.2

15

86

61

8.2

16

31

61

8.2

08

31

61

8.2

07

43

31

8.2

00

56

61

8.2

58

11

8.2

50

21

8.2

39

418.2

286

518

.22

31

66

18.2

18

65

18.2

20

95

Lon

-97.8

80

85

-97.8

80

55

-97.8

80

45

-97.8

74

9-9

7.8

86

95

-97.8

51

63

3-9

7.8

49

71

6-9

7.8

50

45

-97.8

63

43

3-9

7.8

68

-97.8

68

06

6-9

7.8

88

3

Lith

olog

yto

nal.

tron

dhj.

tron

dhj.

tona

l.to

nal.

hblg

abbr

otr

ondh

j.tr

ondh

j.qu

artz

dior

ite

tron

dhj.

tona

l.qu

artz

dior

ite

Age

(Ma)

28

92

89

28

92

89

28

93

06

28

92

89

28

92

89

28

92

89

K2

O0.5

70

.50

0.5

00

.58

0.1

20

.42

0.4

80

.58

0.5

30.8

40

.28

0.9

3

P 2O5

0.3

00

.11

0.0

80

.14

0.3

30

.10

0.0

50.0

60

.08

0.0

90

.26

0.0

7

LOI

1.8

11

.86

0.7

93

.99

4.0

23

.07

1.2

02.4

82

.20

1.5

11

.55

1.3

6

Tota

l1

00.0

10

0.0

10

0.0

10

0.0

10

0.0

97.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

Mg#

48.4

49

.94

1.1

43

.65

0.3

47

.04

1.2

19.6

47

.64

8.2

41

.94

5.8

V(p

pm)

11

65

03

02

44

11

62

57

22

30

30

33

96

28

Cr

41

11

00

14

38

15

91

211

51

0

Co

16

64

28

29

30

24

46

95

Ni

11

74

11

19

21

56

55

10

5

Cu

16

12

51

35

90

13

43

3

Zn

66

42

37

97

83

11

15

23

42

46

61

38

Ga

25

21

19

16

17

13

16

17

18

21

27

19

Rb

81

07

19

23

41

31

21

318

52

4

Sr1

12

27

01

73

23

68

62

83

35

19

55

58

604

66

29

93

64

2

Y8

54

21

914

62

24

63

Zr

71

67

73

37

27

444

964

72

71

846

8

Nb

0.0

0.0

0.0

3.9

1.2

2.1

0.0

0.4

0.0

0.0

1.4

0.0

Ba

20

53

22

42

25

21

42

1042

20

546

740

85

07

119

46

3

Cs

1.3

3.1

1.2

4.0

0.0

1.5

3.7

1.9

2.2

5.0

4.9

0.0

La4.

53.

03.

7

Con

tinue

don

next

page

...


Tabl

a1

2:C

hem

ical

resu

lts

for

rock

sof

the

Toto

ltep

ecPl

uton

.Aca

tlán

Com

plex

,Pue

bla,

Mex

ico

(par

t3

/3).

Nam

eT

T-55

TT-

56T

T-57

TT-

59T

T-60

TT-

72T

T-73

TT-

74T

T-76

BT

T-77

TT-

78T

T-79

Lat

18.2

15

86

61

8.2

16

31

61

8.2

08

31

61

8.2

07

43

31

8.2

00

56

61

8.2

58

11

8.2

50

21

8.2

39

418.2

286

518

.22

31

66

18.2

18

65

18.2

20

95

Lon

-97.8

80

85

-97.8

80

55

-97.8

80

45

-97.8

74

9-9

7.8

86

95

-97.8

51

63

3-9

7.8

49

71

6-9

7.8

50

45

-97.8

63

43

3-9

7.8

68

-97.8

68

06

6-9

7.8

88

3

Lith

olog

yto

nal.

tron

dhj.

tron

dhj.

tona

l.to

nal.

hblg

abbr

otr

ondh

j.tr

ondh

j.qu

artz

dior

ite

tron

dhj.

tona

l.qu

artz

dior

ite

Age

(Ma)

28

92

89

28

92

89

28

93

06

28

92

89

28

92

89

28

92

89

Ce

11.0

18

.83

.51

3.0

6.9

9.9

7.3

6.5

4.9

5.0

9.0

4.2

Pr1.

30.

81.

4

Nd

6.0

3.4

8.3

Sm1.

50.

71.

8

Eu0.

60.

20.

9

Gd

2.1

0.5

1.9

Tb

0.38

0.07

0.20

Dy

2.3

0.4

1.2

Ho

0.54

0.08

0.24

Er1.

60.

20.

6

Tm

0.26

0.04

0.09

Yb

1.5

0.2

0.5

Lu0.

260.

050.

08

Hf

1.0

1.8

1.9

Ta0.

070.

010.

02

Pb0.0

0.0

3.2

0.0

1.7

7.4

6.1

0.4

13.5

0.0

0.0

0.6

Th

1.5

0.5

0.1

U0.5

0.0

0.0

0.0

0.0

0.0

1.9

0.0

0.2

0.0

0.0

0.0


Tabl

a1

3:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t1

/4.)

Nam

eT

T-5A

TT-

5BT

T-6

TT-

7AT

T-7B

TT-

8AT

T-8B

TT-

32T

T-33

TT-

34A

TT-

34B

TT-

35

Lat

18.2

00

11

61

8.2

00

11

61

8.1

99

55

18.2

07

51

61

8.2

07

51

61

8.2

12

18

.21

21

8.2

56

03

31

8.2

55

81

8.2

422

16

18

.24

22

16

18.2

44

31

6

Lon

-97.8

16

66

6-9

7.8

16

66

6-9

7.8

16

86

6-9

7.8

21

61

6-9

7.8

21

61

6-9

7.8

33

85

-97.8

33

85

-97

.77

74

66

-97.7

77

9-9

7.7

889

66

-97.7

88

96

6-9

7.7

87

58

3

Lith

olog

ym

etap

s.m

etap

s.m

etap

el.

met

apel

.m

etap

s.m

etap

s.m

etap

s.m

etap

s.m

etap

s.m

etap

el.

met

apel

.m

etap

el.

SiO2

(wt%

)7

1.5

68

.86

4.1

64

.36

5.2

66

.86

4.5

67.1

61

.95

7.0

53.5

58.8

TiO2

0.3

90

.40

0.6

00

.68

0.6

60

.50

0.5

40.5

10

.64

0.8

30

.52

0.8

1

Al 2

O3

11.7

11

.31

6.6

16

.41

5.1

14

.71

3.3

13.1

15.7

18

.31

6.9

20.3

Fe2

O3

3.7

34

.16

6.5

87

.05

5.4

34.3

04

.61

3.6

15.7

47

.69

9.0

67.7

5

MnO

0.0

64

0.0

94

0.0

66

0.0

70

0.0

60

0.0

56

0.0

59

0.0

80

0.0

72

0.0

97

0.1

34

0.1

06

MgO

1.6

11

.59

2.5

62

.41

2.0

62.0

01

.85

1.3

42

.46

5.7

4.8

72.0

7

CaO

3.4

34

.68

1.1

90

.84

3.1

92.7

34

.83

4.2

33

.60

0.7

65

.67

0.3

4

Na 2

O3.2

03

.57

2.7

93

.83

3.7

44.4

82

.62

4.8

52

.73

1.3

03

.79

0.5

1

K2

O0.6

90

.55

1.4

11

.00

1.0

30.7

71

.43

0.6

71

.71

3.0

40

.42

4.7

0

P 2O5

0.0

50

.06

0.1

40

.18

0.1

30.1

40

.13

0.1

00.1

60

.17

0.0

30.2

0

LOI

3.7

34

.82

3.8

93

.33

3.5

03.5

86

.12

4.4

85

.29

5.0

75

.17

4.4

5

Tota

l1

00.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

100

.010

0.0

10

0.0

10

0.0

Mg#

43

.54

0.5

40

.93

7.9

40

.34

5.3

41

.73

9.8

43.3

56

.94

8.9

32.2

V(p

pm)

10

61

15

16

11

58

13

59

41

08

11

11

58

18

51

80

18

1

Cr

21

19

75

80

53

13

65

34

68

36

81

09

10

1

Co

88

17

17

15

91

67

16

32

33

22

Ni

12

11

26

38

27

10

28

17

27

20

74

04

8

Cu

91

03

13

62

22

41

333

21

52

67

Zn

54

48

10

21

21

85

69

10

26

213

01

26

78

13

4

Ga

14

11

19

20

16

15

17

12

18

27

19

29

Rb

30

24

65

47

52

33

66

32

81

11

71

22

06

Con

tinue

don

next

page

...


Tabl

a1

3:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t1

/4.)

Nam

eT

T-5A

TT-

5BT

T-6

TT-

7AT

T-7B

TT-

8AT

T-8B

TT-

32T

T-33

TT-

34A

TT-

34B

TT-

35

Lat

18.2

00

11

61

8.2

00

11

61

8.1

99

55

18.2

07

51

61

8.2

07

51

61

8.2

12

18

.21

21

8.2

56

03

31

8.2

55

81

8.2

422

16

18

.24

22

16

18.2

44

31

6

Lon

-97.8

16

66

6-9

7.8

16

66

6-9

7.8

16

86

6-9

7.8

21

61

6-9

7.8

21

61

6-9

7.8

33

85

-97.8

33

85

-97

.77

74

66

-97.7

77

9-9

7.7

889

66

-97.7

88

96

6-9

7.7

87

58

3

Lith

olog

ym

etap

s.m

etap

s.m

etap

el.

met

apel

.m

etap

s.m

etap

s.m

etap

s.m

etap

s.m

etap

s.m

etap

el.

met

apel

.m

etap

el.

Sr1

59

17

12

20

17

17

21

29

42

39

33

723

39

13

07

12

2

Y20

25

303

324

19

28

18

29

38

29

36

Zr

125

98

179

16

030

01

37

21

61

56

157

22

44

42

25

Nb

5.3

1.7

9.7

9.1

9.4

2.4

7.3

0.4

5.9

15.6

0.0

16

.7

Ba

234

18

646

74

13

582

33

56

01

32

84

17

76

64

99

86

7

Cs

5.4

2.2

1.1

5.0

3.6

1.9

7.5

0.0

6.0

6.3

4.9

8.0

La13

.320

.322

.9

Ce

26.7

26.3

41.1

42.8

45.8

31

.15

0.3

31.3

52

.49

6.7

4.8

63.9

Pr3.

45.

46.

2

Nd

13.3

22.8

24.0

Sm3.

25.

44.

7

Eu0.

71.

21.

1

Gd

3.3

5.4

4.9

Tb

0.51

0.86

0.79

Dy

3.5

5.8

4.9

Ho

0.77

1.24

1.01

Er2.

23.

42.

9

Tm

0.38

0.50

0.44

Yb

2.4

3.2

2.7

Lu0.

380.

510.

43

Hf

3.3

3.9

6.8

Con

tinue

don

next

page

...


Tabl

a1

3:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t1

/4.)

Nam

eT

T-5A

TT-

5BT

T-6

TT-

7AT

T-7B

TT-

8AT

T-8B

TT-

32T

T-33

TT-

34A

TT-

34B

TT-

35

Lat

18.2

00

11

61

8.2

00

11

61

8.1

99

55

18.2

07

51

61

8.2

07

51

61

8.2

12

18

.21

21

8.2

56

03

31

8.2

55

81

8.2

422

16

18

.24

22

16

18.2

44

31

6

Lon

-97.8

16

66

6-9

7.8

16

66

6-9

7.8

16

86

6-9

7.8

21

61

6-9

7.8

21

61

6-9

7.8

33

85

-97.8

33

85

-97

.77

74

66

-97.7

77

9-9

7.7

889

66

-97.7

88

96

6-9

7.7

87

58

3

Lith

olog

ym

etap

s.m

etap

s.m

etap

el.

met

apel

.m

etap

s.m

etap

s.m

etap

s.m

etap

s.m

etap

s.m

etap

el.

met

apel

.m

etap

el.

Ta0.

190.

370.

36

Pb1

5.5

07

.01

6.9

22

.98.1

8.5

10.7

11.1

18.6

17

.85.4

13

.2

Th

3.3

6.8

6.6

U2.2

2.2

2.4

4.1

0.6

0.0

0.0

2.4

4.5

1.4

2.5

2.5

Tabl

a1

4:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t2

/4.)

Nam

eT

T-36

TT-

37A

TT-

37B

TT-

38A

TT-

38B

TT-

39T

T-40

BT

T-43

TT-

61A

TT-

61B

TT-

62T

T-63

A

Lat

18.2

44

03

31

8.2

45

58

31

8.2

45

58

31

8.2

47

01

61

8.2

47

01

61

8.2

47

96

61

8.2

48

51

61

8.2

53

81

8.1

962

18.1

962

18

.19

67

83

18.1

93

65

Lon

-97.7

87

43

3-9

7.7

86

1-9

7.7

86

1-9

7.7

85

83

3-9

7.7

85

83

3-9

7.7

85

48

3-9

7.7

84

1-9

7.7

80

46

6-9

7.8

946

16

-97.8

94

61

6-9

7.8

93

68

3-9

7.8

94

2

Lith

olog

ym

etap

s.m

etap

s.m

etap

el.

met

aps.

met

apel

.m

etap

s.m

etap

el.

met

apel

.m

etap

s.m

etap

s.m

etap

s.m

eta-

ark.

SiO2

(wt%

)6

6.4

66.9

58

.76

7.9

59

.36

8.0

67.3

61

.87

2.1

70.6

71.2

56.1

TiO2

0.5

10.4

70

.76

0.4

50

.73

0.3

80.6

60

.61

0.3

50.3

70

.54

1.7

0

Al 2

O3

14.5

13.4

17

.61

5.0

14

.31

5.1

15.8

14

.51

4.2

14.0

13.4

16.4

Fe2

O3

5.2

04.5

27

.24

4.5

97

.03

3.0

25.1

15

.77

1.3

01.9

73

.31

11.3

MnO

0.0

82

0.0

74

0.0

62

0.0

72

0.1

20

0.0

66

0.0

56

0.0

79

0.0

18

0.0

23

0.0

16

0.1

82

MgO

2.4

92.1

43

.36

1.7

33

.77

1.1

91

.81

2.7

14.7

65.7

42

.79

3.4

4

CaO

2.5

63

.25

1.8

32.0

85

.51

2.2

90

.65

4.1

70.0

80.1

50

.54

2.4

8

Na 2

O3.8

14

.57

1.6

76.1

03

.88

4.4

72

.89

1.9

40.1

40.1

14

.35

2.0

6

Con

tinue

don

next

page

...


Tabl

a1

4:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t2

/4.)

Nam

eT

T-36

TT-

37A

TT-

37B

TT-

38A

TT-

38B

TT-

39T

T-40

BT

T-43

TT-

61A

TT-

61B

TT-

62T

T-63

A

Lat

18.2

44

03

31

8.2

45

58

31

8.2

45

58

31

8.2

47

01

61

8.2

47

01

61

8.2

47

96

61

8.2

48

51

61

8.2

53

81

8.1

962

18.1

962

18

.19

67

83

18.1

93

65

Lon

-97.7

87

43

3-9

7.7

86

1-9

7.7

86

1-9

7.7

85

83

3-9

7.7

85

83

3-9

7.7

85

48

3-9

7.7

84

1-9

7.7

80

46

6-9

7.8

946

16

-97.8

94

61

6-9

7.8

93

68

3-9

7.8

94

2

Lith

olog

ym

etap

s.m

etap

s.m

etap

el.

met

aps.

met

apel

.m

etap

s.m

etap

el.

met

apel

.m

etap

s.m

etap

s.m

etap

s.m

eta-

ark.

K2

O0.9

50.6

93

.45

0.4

60

.62

.85

2.9

22

.32

3.6

03.3

61

.25

1.2

7

P 2O5

0.1

10.1

00

.21

0.1

90

.27

0.1

60.1

70

.17

0.0

50.0

90

.12

0.3

0

LOI

3.4

43.8

95

.07

1.4

64

.52

2.5

02.7

15

.93

3.4

03.6

32

.54

4.8

3

Tota

l1

00.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

Mg#

46

.04

5.8

45

.34

0.2

48

.94

1.2

38.7

45

.68

6.7

83.8

60.0

35

.2

V(p

pm)

12

91

15

18

03

87

45

81

02

15

015

40

51

19

8

Cr

46

49

97

21

17

11

47

08

75

10

33

7

Co

13

13

17

92

44

14

12

41

21

41

6

Ni

19

17

39

89

11

03

33

47

91

32

6

Cu

20

19

38

10

20

11

15

33

113

82

8

Zn

79

67

14

35

26

25

99

81

34

35

71

09

Ga

15

14

23

16

15

18

22

18

15

14

14

21

Rb

37

29

11

38

14

78

10

28

469

78

27

77

Sr2

91

25

91

45

30

94

11

25

31

73

20

011

11

96

13

5

Y25

25

27

22

29

123

63

133

38

35

34

Zr

143

11

91

78

12

61

71

175

20

51

66

291

324

20

51

21

Nb

5.9

0.9

11

.72.8

6.7

13.5

15.5

7.2

11.9

11.7

6.9

10.2

Ba

364

24

89

15

24

33

21

951

75

27

52

600

18

00

48

65

28

Cs

5.7

3.8

5.4

0.0

0.5

4.6

6.3

2.0

8.7

0.0

0.5

2.8

La13

.940

.739

.6

Ce

28.8

22.7

66

.62

9.1

37

.779

.38

1.2

43.0

74.6

66.7

52.6

47

.7

Con

tinue

don

next

page

...


Tabl

a1

4:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t2

/4.)

Nam

eT

T-36

TT-

37A

TT-

37B

TT-

38A

TT-

38B

TT-

39T

T-40

BT

T-43

TT-

61A

TT-

61B

TT-

62T

T-63

A

Lat

18.2

44

03

31

8.2

45

58

31

8.2

45

58

31

8.2

47

01

61

8.2

47

01

61

8.2

47

96

61

8.2

48

51

61

8.2

53

81

8.1

962

18.1

962

18

.19

67

83

18.1

93

65

Lon

-97.7

87

43

3-9

7.7

86

1-9

7.7

86

1-9

7.7

85

83

3-9

7.7

85

83

3-9

7.7

85

48

3-9

7.7

84

1-9

7.7

80

46

6-9

7.8

946

16

-97.8

94

61

6-9

7.8

93

68

3-9

7.8

94

2

Lith

olog

ym

etap

s.m

etap

s.m

etap

el.

met

aps.

met

apel

.m

etap

s.m

etap

el.

met

apel

.m

etap

s.m

etap

s.m

etap

s.m

eta-

ark.

Pr3.

88.

98.

9

Nd

14.8

32.7

39.3

Sm4.

05.

17.

1

Eu0.

91.

11.

4

Gd

4.1

3.5

6.5

Tb

0.70

0.49

0.95

Dy

4.6

2.6

6.1

Ho

0.96

0.47

1.28

Er3.

11.

34.

0

Tm

0.46

0.17

0.57

Yb

3.3

1.2

4.0

Lu0.

460.

190.

64

Hf

3.4

4.1

7.6

Ta0.

210.

470.

51

Pb1

5.1

10.6

89

.41

7.3

3.1

24.4

15

.01

9.7

6.4

2.2

7.7

14.5

Th

4.8

15.2

6.6

U3.4

4.5

3.6

0.0

3.0

7.7

0.6

4.8

4.2

3.1

0.7

2.3


Tabl

a1

5:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t3

/4.)

Nam

eT

T-63

BT

T-65

TT-

66T

T-67

TT-

68T

T-69

TT-

70T

T-83

AT

T-84

TT-

85T

T-86

TT-

87

Lat

18.1

93

65

18

.18

98

51

8.1

90

11

8.1

90

21

8.1

90

68

31

8.1

91

46

61

8.1

91

85

18.2

00

11

618

.19

38

16

18.1

894

18.1

77

61

61

8.1

77

9

Lon

-97.8

94

2-9

7.8

99

56

6-9

7.8

99

33

3-9

7.8

99

16

6-9

7.8

98

88

3-9

7.8

98

3-9

7.8

97

85

-97.8

16

66

6-9

7.8

93

26

6-9

7.8

92

25

-97.8

87

9-9

7.8

87

Lith

olog

ym

etap

el.

met

a-ar

k.m

eta-

ark.

met

a-ar

k.m

eta-

ark.

met

a-ar

k.m

etap

el.

met

a-co

ngl.

met

a-ar

k.m

eta-

ark.

met

aps.

met

a-co

ngl.

SiO2

(wt%

)6

0.3

72

.97

2.2

70

.07

2.1

68

.96

0.5

72

.863

.170.3

64

.17

4.0

TiO2

0.8

80.4

20

.39

0.6

20

.44

0.5

00.6

40.2

20.7

20

.47

0.5

90.3

4

Al 2

O3

19.3

12.8

12

.91

3.1

13

.51

4.2

14.4

10.7

17.9

12

.61

5.2

11.7

Fe2

O3

7.3

03.5

83

.40

4.5

53

.89

5.0

96.1

61.5

96.6

64

.48

6.0

62.4

3

MnO

0.1

09

0.0

85

0.1

02

0.0

81

0.0

90

0.1

03

0.0

77

0.0

65

0.0

78

0.0

91

0.0

83

0.0

65

MgO

2.1

51.3

11

.74

1.5

21

.58

1.8

82.7

20.7

22.3

51

.94

2.8

90.7

2

CaO

0.3

61.8

91

.43

2.2

11

.13

1.9

04.7

34.5

20.5

22

.18

2.2

92.5

6

Na 2

O0.8

43.4

74

.06

3.7

84

.23

3.5

01.5

75.1

20.8

63

.27

3.2

95.7

6

K2

O4.1

11.1

21

.01

1.0

41

.01

1.1

92.6

10.2

54.3

11

.03

1.3

00.2

6

P 2O5

0.1

80.0

90

.08

0.0

70

.10

0.1

00.1

60.0

30.1

80

.06

0.1

30.0

7

LOI

4.5

32.3

32

.75

3.0

62

.00

2.5

76.3

83.9

93.2

83

.55

4.0

22.1

2

Tota

l1

00

.01

00

.01

00

.01

00

.01

00

.01

00.0

10

0.0

10

0.0

100

.01

00.0

10

0.0

10

0.0

Mg#

34.4

39.5

47

.73

7.3

42

.03

9.7

44.0

44.7

38.6

43

.64

5.9

34.6

V(p

pm)

13

86

55

71

08

74

10

61

42

38

130

113

15

33

4

Cr

10

02

01

83

02

62

39

21

386

41

74

13

Co

18

75

94

81

73

16

11

15

5

Ni

41

13

10

14

15

13

43

737

17

27

6

Cu

24

10

10

11

91

12

61

132

93

33

3

Zn

11

44

44

16

74

85

31

36

19

75

64

10

72

1

Ga

27

13

12

13

14

16

19

12

26

13

18

8

Rb

18

84

23

54

74

14

89

65

12

94

35

45

Con

tinue

don

next

page

...


Tabl

a1

5:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t3

/4.)

Nam

eT

T-63

BT

T-65

TT-

66T

T-67

TT-

68T

T-69

TT-

70T

T-83

AT

T-84

TT-

85T

T-86

TT-

87

Lat

18.1

93

65

18

.18

98

51

8.1

90

11

8.1

90

21

8.1

90

68

31

8.1

91

46

61

8.1

91

85

18.2

00

11

618

.19

38

16

18.1

894

18.1

77

61

61

8.1

77

9

Lon

-97.8

94

2-9

7.8

99

56

6-9

7.8

99

33

3-9

7.8

99

16

6-9

7.8

98

88

3-9

7.8

98

3-9

7.8

97

85

-97.8

16

66

6-9

7.8

93

26

6-9

7.8

92

25

-97.8

87

9-9

7.8

87

Lith

olog

ym

etap

el.

met

a-ar

k.m

eta-

ark.

met

a-ar

k.m

eta-

ark.

met

a-ar

k.m

etap

el.

met

a-co

ngl.

met

a-ar

k.m

eta-

ark.

met

aps.

met

a-co

ngl.

Sr4

79

59

81

34

90

12

02

16

15

96

41

39

20

71

21

Y4

73

22

917

32

33

34

67

38

23

30

40

Zr

20

61

32

11

429

01

43

12

71

59

15

91

87

17

01

63

19

5

Nb

20.3

5.5

3.3

8.7

3.5

3.0

9.1

3.4

16

.42.7

5.4

2.9

Ba

92

44

26

35

136

63

08

41

67

39

74

689

420

46

92

13

Cs

7.7

2.3

0.3

0.0

1.6

5.5

6.6

5.9

2.6

3.6

2.9

0.6

La17

.2

Ce

10

1.0

29.6

35

.535

.32

9.8

31

.26

4.1

46.3

82.2

28

.23

6.6

22.5

Pr4.

3

Nd

16.8

Sm3.

6

Eu0.

9

Gd

3.4

Tb

0.50

Dy

3.5

Ho

0.74

Er2.

1

Tm

0.32

Yb

2.6

Lu0.

40

Hf

6.6

Con

tinue

don

next

page

...


Tabl

a1

5:C

hem

ical

resu

lts

for

the

Teco

mat

eFo

rmat

ion.

Aca

tlán

Com

plex

,Pue

bla/

Oax

aca,

Mex

ico

(par

t3

/4.)

Nam

eT

T-63

BT

T-65

TT-

66T

T-67

TT-

68T

T-69

TT-

70T

T-83

AT

T-84

TT-

85T

T-86

TT-

87

Lat

18.1

93

65

18

.18

98

51

8.1

90

11

8.1

90

21

8.1

90

68

31

8.1

91

46

61

8.1

91

85

18.2

00

11

618

.19

38

16

18.1

894

18.1

77

61

61

8.1

77

9

Lon

-97.8

94

2-9

7.8

99

56

6-9

7.8

99

33

3-9

7.8

99

16

6-9

7.8

98

88

3-9

7.8

98

3-9

7.8

97

85

-97.8

16

66

6-9

7.8

93

26

6-9

7.8

92

25

-97.8

87

9-9

7.8

87

Lith

olog

ym

etap

el.

met

a-ar

k.m

eta-

ark.

met

a-ar

k.m

eta-

ark.

met

a-ar

k.m

etap

el.

met

a-co

ngl.

met

a-ar

k.m

eta-

ark.

met

aps.

met

a-co

ngl.

Ta0.

33

Pb2

3.9

12

.91

2.2

13

.16

.51

2.9

14

.34

2.0

10

.810.5

15

.11

8.6

Th

4.8

U8.6

2.3

3.3

0.0

4.0

3.7

0.0

6.1

3.7

3.2

4.4

3.1


Tabla 16: Chemical results for the Tecomate Formation. AcatlánComplex, Puebla/Oaxaca, Mexico. (part 4/4)

Name TT-88 TT-89 TT-90 TT-91 TT-486B

Lat 18.178133 18.1788 18.179283 18.176533 18.28409

Lon -97.886583 -97.887366 -97.8867 -97.88415 -97.91114

Lithology meta-ark. meta-ark. meta-ark. meta-ark. metaps.

SiO2 (wt %) 65.7 64.2 71.2 71.1 75.16

TiO2 0.57 0.61 0.43 0.46 0.853

Al2O3 13.3 16.1 13.4 13.3 11.31

Fe2O3 4.30 6.12 3.72 3.99 3.92

MnO 0.100 0.083 0.067 0.068 0.053

MgO 1.82 2.99 1.53 1.64 0.97

CaO 4.02 1.80 2.08 1.96 1.07

Na2O 4.30 3.14 4.71 4.13 2.18

K2O 1.08 1.69 0.70 0.88 2.16

P2O5 0.14 0.15 0.08 0.10 0.124

LOI 4.70 3.16 2.04 2.44 2.26

Total 100.0 100.0 100.0 100.0 100.06

Mg# 43.0 46.5 42.3 42.3

V (ppm) 113 144 84 83 77.4

Cr 42 86 25 43 49.3

Co 13 14 10 13 10.5

Ni 24 27 12 21 19.4

Cu 22 29 20 11 35.9

Zn 74 112 52 60 47.1

Ga 15 19 14 15 16.6

Rb 51 70 23 39 77.9

Sr 277 216 237 217 127.2

Y 19 28 24 19 40.8

Zr 146 162 105 130 459.3

Nb 4.0 7.7 2.9 4.2 18.3

Ba 614 633 363 309 786

Cs 5.6 1.6 3.0 3.1 4.3

La

Ce 36.8 42.3 24.7 39.1 66.1

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

Hf

Ta

Pb 16.5 14.3 99.6 67.7 8

Th 14.8

U 3.0 2.5 2.4 3.3 1.8


Tabl

a1

7:C

hem

ical

resu

lts

for

the

Coz

ahui

cogr

anit

eas

wel

las

LaC

arbo

nera

stoc

k,Pu

ebla

/Oax

aca,

Mex

ico.

Coz

ahui

cogr

anit

eLa

Car

bone

rast

ock

Nam

eT

T-55

8T

T-55

9T

T-56

0T

T-56

1T

T-56

2T

T-56

3T

T-56

4T

T-56

5AT

T-56

5BT

T-56

6T

T-56

8T

T-56

9

Lat

18.1

26

19

32

18

.12

68

12

71

8.1

27

82

42

18

.19

57

65

18

.19

57

82

21

8.1

95

40

56

18

.20

19

81

31

7.2

99

66

217

.299

66

21

7.2

997

66

91

7.2

99

98

66

17.2

99

93

34

Lon

-97.4

50

30

84

-97.4

49

79

7-9

7.4

50

55

66

-97.5

00

51

7-9

7.5

01

70

58

-97.5

00

97

34

-97.5

13

28

29

-97.0

10

95

35

-97.0

10

95

35

-97.0

116

32

6-9

7.0

12

57

95

-97.0

11

31

75

Lith

olog

ygr

anit

egr

anit

egr

anit

egr

anit

egr

anit

egr

anit

egr

anit

edi

orit

edi

orit

edi

orit

ega

bbro

gran

odio

rite

SiO2

(wt%

)7

0.5

71

.37

0.6

77

.47

5.5

76

.47

3.1

58.9

57

.45

7.0

48.6

67.1

TiO2

0.1

60

.15

0.1

60

.17

0.3

30.4

20.2

30.5

50.7

90.8

41.5

40.2

9

Al 2

O3

16.9

16

.61

6.8

13

.71

2.6

12.6

15.2

21.2

18.2

18.4

11.6

17.8

Fe2

O3

1.0

00

.80

0.9

10

.97

2.2

30.7

31.0

63.6

58.0

27.7

61

9.1

3.3

7

MnO

0.0

16

0.0

15

0.0

20

.00

10.0

40

0.0

26

0.0

34

0.0

50.1

50.1

40.2

10.0

4

MgO

0.3

0.3

30.2

90

.15

0.1

80.0

60.1

60.8

31.8

32.2

05.6

20.4

1

CaO

1.6

91

.28

1.9

30

.28

0.7

0.6

70.7

17.0

36.4

67.0

68.2

94.1

8

Na 2

O5.9

05

.74

5.7

24

.58

2.9

52.8

64.1

54.4

43.5

33.6

11.9

64.6

3

K2

O2.7

52

.76

2.6

72

.11

5.0

15.4

94.3

11.5

31.7

71.5

61.5

41.7

7

P 2O5

0.0

50

.04

0.0

50

.04

0.0

40.0

40.0

70.1

90.4

60.5

60.5

50.1

0

LOI

1.2

91

.16

1.1

51

.16

1.0

50.9

81.4

40.7

71.0

01.0

11.0

50.5

6

Tota

l1

00.5

10

0.2

10

0.3

10

0.6

10

0.6

10

0.3

10

0.4

99

.19

9.6

100

.21

00.0

10

0.3

Mg#

37.3

45

.03

8.7

23

.51

3.8

14.0

23.0

31.1

31.1

36.0

36.9

19.4

V(p

pm)

11

11

13

13

14

11

16

14

39

55

20

36

Cr

00

00

00

00

04

10

90

Co

10

12

30

13

810

34

2

Ni

42

45

44

35

56

42

1

Cu

63

16

16

23

13

68

39

43

5

Zn

37

37

32

82

08

12

74

12

51

21

21

86

5

Con

tinue

don

next

page

...


Tabl

a1

7:C

hem

ical

resu

lts

for

the

Coz

ahui

cogr

anit

eas

wel

las

LaC

arbo

nera

stoc

k,Pu

ebla

/Oax

aca,

Mex

ico.

Coz

ahui

cogr

anit

eLa

Car

bone

rast

ock

Nam

eT

T-55

8T

T-55

9T

T-56

0T

T-56

1T

T-56

2T

T-56

3T

T-56

4T

T-56

5AT

T-56

5BT

T-56

6T

T-56

8T

T-56

9

Lat

18.1

26

19

32

18

.12

68

12

71

8.1

27

82

42

18

.19

57

65

18

.19

57

82

21

8.1

95

40

56

18

.20

19

81

31

7.2

99

66

217

.299

66

21

7.2

997

66

91

7.2

99

98

66

17.2

99

93

34

Lon

-97.4

50

30

84

-97.4

49

79

7-9

7.4

50

55

66

-97.5

00

51

7-9

7.5

01

70

58

-97.5

00

97

34

-97.5

13

28

29

-97.0

10

95

35

-97.0

10

95

35

-97.0

116

32

6-9

7.0

12

57

95

-97.0

11

31

75

Lith

olog

ygr

anit

egr

anit

egr

anit

egr

anit

egr

anit

egr

anit

egr

anit

edi

orit

edi

orit

edi

orit

ega

bbro

gran

odio

rite

Ga

19

19

19

17

17

12

21

22

21

21

17

20

Rb

32

31

31

46

77

79

13

32

535

27

25

22

Sr8

98

76

79

72

11

68

61

15

18

41

03

770

37

24

25

07

03

Y5

54

23

57

47

162

857

4

Zr

16

01

45

105

11

63

54

459

140

367

130

123

273

175

Nb

1.7

1.8

1.5

7.0

2.5

4.3

5.9

5.9

6.9

9.2

155.

9

Ba

14

67

11

88

1603

40

21

00

411

9740

911

4612

368

71

1057

1546

Cs

1.2

0.7

La5.

46.

714

.418

.719

.329

.321

.2

Ce

22.2

20

.910

.73

9.2

53

.811

.225

.737

.440

.54

9.6

85.1

42.5

Pr1.

41.

53.

04.

795.

3314

.55.

32

Nd

4.4

5.9

5.4

14

.61

8.0

6.4

10.8

19.2

22.8

37.0

073

.021

.0

Sm1.

11.

61.

83.

614.

6218

.13.

54

Eu0.

41.

40.

51.

791.

662.

851.

31

Gd

0.7

1.3

0.9

2.06

3.50

14.8

1.65

Tb

0.10

0.24

0.14

0.30

0.56

2.27

0.23

Dy

0.6

1.6

0.8

1.70

3.23

13.1

1.04

Ho

0.12

0.32

0.16

0.27

0.58

2.30

0.14

Er0.

40.

90.

50.

691.

565.

840.

35

Tm

0.06

0.12

0.07

0.08

0.22

0.75

0.05

Con

tinue

don

next

page

...


Tabl

a1

7:C

hem

ical

resu

lts

for

the

Coz

ahui

cogr

anit

eas

wel

las

LaC

arbo

nera

stoc

k,Pu

ebla

/Oax

aca,

Mex

ico.

Coz

ahui

cogr

anit

eLa

Car

bone

rast

ock

Nam

eT

T-55

8T

T-55

9T

T-56

0T

T-56

1T

T-56

2T

T-56

3T

T-56

4T

T-56

5AT

T-56

5BT

T-56

6T

T-56

8T

T-56

9

Lat

18.1

26

19

32

18

.12

68

12

71

8.1

27

82

42

18

.19

57

65

18

.19

57

82

21

8.1

95

40

56

18

.20

19

81

31

7.2

99

66

217

.299

66

21

7.2

997

66

91

7.2

99

98

66

17.2

99

93

34

Lon

-97.4

50

30

84

-97.4

49

79

7-9

7.4

50

55

66

-97.5

00

51

7-9

7.5

01

70

58

-97.5

00

97

34

-97.5

13

28

29

-97.0

10

95

35

-97.0

10

95

35

-97.0

116

32

6-9

7.0

12

57

95

-97.0

11

31

75

Lith

olog

ygr

anit

egr

anit

egr

anit

egr

anit

egr

anit

egr

anit

egr

anit

edi

orit

edi

orit

edi

orit

ega

bbro

gran

odio

rite

Yb

0.4

0.9

0.5

0.70

1.51

4.64

0.20

Lu0.

070.

140.

090.

100.

240.

680.

03

Hf

2.8

10.0

3.7

6.48

2.96

6.85

3.94

Ta0.

080.

210.

330.

220.

290.

390.

19

Pb0.0

03

.40

.01

0.0

12

.51

0.3

9.4

0.0

05.5

00.2

09.7

00.0

0

Th

0.5

0.2

5.3

2.59

2.09

3.09

2.16

U0.7

0.7

0.0

5.0

0.2

2.7

1.4

0.0

01.7

00.8

03.6

02.1

0

DTA B L A S A N Á L I S I S D E M I C R O S O N D A

Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Lee, J.K.W., Arc plutonism in atranstensional regime: the Late Palaeozoic Totoltepec pluton, AcatlánComplex, southern Mexico: International Geology Review, en prensa, doi:10.1080/00206814.2012.693247.

138

tablas análisis de microsonda 139

Tabl

a1

8:A

vera

gepl

agio

clas

eco

mpo

siti

ons

ofro

cks

from

the

Toto

ltep

ecpl

uton

.

Sam

ple

TT-

14T

T-14

TT-

14T

T-13

aT

T-13

aT

T-13

aT

T-55

TT-

55T

T-55

TT-

54T

T-54

TT-

54T

T-17

TT-

17Sp

ecim

enP1

P3P2

P1P3

P2P2

P3P1

P1P2

P3P1

P2

wt.

%Si

O2

57

.66

58

.12

59

.06

61.2

56

0.0

45

9.7

75

8.3

55

8.6

45

8.6

56

0.6

16

0.2

36

2.7

75

5.6

55

6.0

3

TiO2

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

Al 2

O3

27

.38

27

.41

26

.31

24.3

32

5.2

22

5.0

82

6.6

72

6.4

22

6.2

82

4.6

62

5.1

12

4.2

82

8.4

72

8.3

2

FeO

0.0

60

.06

0.0

30.0

50

.04

0.0

50

.04

0.0

40

.04

0.0

40.0

20

.07

0.0

70

.10

MgO

0.0

00

.00

0.0

00.0

10

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

CaO

9.0

19

.30

8.7

16.5

56

.70

7.2

78

.45

8.4

28

.32

6.1

27.1

46

.17

11

.63

11

.03

Na 2

O6

.29

6.2

06

.43

7.7

57

.66

7.4

46

.78

6.6

66

.68

7.9

57.5

88

.18

4.9

35

.25

K2

O0

.04

0.0

50

.05

0.1

00

.05

0.1

00

.05

0.0

40

.03

0.1

40.0

70

.08

0.0

40

.06

SrO

0.0

50

.03

0.0

70

.00

0.0

00

.02

0.0

40

.02

0.0

40.0

00.0

00

.02

0.0

00

.01

NiO

0.0

10

.00

0.0

00

.00

0.0

00

.00

0.0

20

.00

0.0

10.0

00.0

10

.00

0.0

10

.01

BaO

0.0

00

.02

0.0

00

.00

0.0

10

.01

0.0

10

.01

0.0

10.0

20.0

00

.00

0.0

30

.01

Tota

l1

00

.50

10

1.2

01

00

.66

10

0.0

49

9.7

49

9.7

51

00.4

11

00

.25

10

0.0

79

9.5

41

00.1

71

01

.56

10

0.8

21

00

.83

Num

ber

ofio

nson

the

basi

sof

8ox

ygen

atom

sSi

2.5

72

.57

2.6

22

.72

2.6

82

.67

2.6

02

.61

2.6

22.7

12.6

82

.74

2.4

92

.50

Ti0

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

Al

1.4

41

.43

1.3

81

.27

1.3

31

.32

1.4

01

.39

1.3

81.3

01.3

21

.25

1.5

01

.49

Fe2+

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00.0

00

.00

0.0

00

.00

Con

tinue

don

next

page

...


Tabl

a1

8:A

vera

gepl

agio

clas

eco

mpo

siti

ons

ofro

cks

from

the

Toto

ltep

ecpl

uton

.

Sam

ple

TT-

14T

T-14

TT-

14T

T-13

aT

T-13

aT

T-13

aT

T-55

TT-

55T

T-55

TT-

54T

T-54

TT-

54T

T-17

TT-

17Sp

ecim

enP1

P3P2

P1P3

P2P2

P3P1

P1P2

P3P1

P2

Mg

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

Ca

0.4

30

.44

0.4

10.3

10

.32

0.3

50

.40

0.4

00

.40

0.2

90.3

40

.29

0.5

60

.53

Na

0.5

40

.53

0.5

50.6

70

.66

0.6

40

.59

0.5

80

.58

0.6

90.6

50

.69

0.4

30

.45

K0

.00

0.0

00

.00

0.0

10

.00

0.0

10

.00

0.0

00

.00

0.0

10.0

00

.00

0.0

00

.00

Sr0

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

Ni

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

Ba0

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00

.00

0.0

00.0

00

.00

0.0

00

.00

Tota

l4

.99

4.9

84

.97

4.9

84

.99

4.9

94

.99

4.9

84

.98

4.9

94.9

94

.98

4.9

84

.98

mol

%A

n4

4.1

45

.24

2.7

31

.73

2.5

34

.94

0.7

41

.04

0.7

29.6

34.1

29

.35

6.5

53

.5A

b5

5.7

54

.55

7.0

67

.86

7.2

64

.55

9.0

58

.75

9.1

69.6

65.5

70

.24

3.3

46

.1O

r0

.30

.30

.30.5

0.3

0.6

0.3

0.2

0.2

0.8

0.4

0.5

0.2

0.3

Tota

l1

00

.01

00

.01

00

.01

00.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0

10

0.0


Tabl

a1

9:A

vera

geam

phib

ole

com

posi

tion

sof

rock

sfr

omth

eTo

tolt

epec

plut

on.

Sam

ple

TT-

14T

T-14

TT-

14T

T-13

aT

T-13

aT

T-13

aT

T-55

TT-

55T

T-55

TT-

54T

T-54

TT-

54T

T-28

TT-

28T

T-28

TT-

17T

T-17

TT-

17

Spec

imen

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

wt.

%

SiO2

45.0

14

3.5

14

3.9

34

2.7

24

2.1

34

2.8

54

3.9

94

2.5

14

4.1

54

1.5

24

1.4

84

2.3

34

3.4

144.6

343.6

14

6.7

84

6.3

14

6.0

7

TiO2

0.9

20

.97

1.0

40.7

20.7

10.6

60

.62

0.5

00.6

10.5

60.6

00.6

41.4

91.2

31.5

21.2

81.3

31.1

8

Al 2

O3

10.0

91

1.0

11

0.6

01

1.4

41

1.9

01

2.1

81

2.3

01

3.6

31

2.2

81

3.2

81

2.8

41

2.5

211

.92

12.0

91

2.3

08

.17

8.1

08.4

4

FeO

15.2

41

6.1

71

5.5

21

9.2

71

9.0

11

9.6

11

6.5

31

7.1

21

6.4

61

8.9

21

8.6

81

8.6

112.5

213.3

412.8

31

7.5

31

7.6

61

6.9

4

MgO

13.1

21

2.0

51

2.3

49.5

58.2

29.0

01

0.8

69

.78

11

.08

8.9

99

.47

9.5

313.3

012.5

213.0

01

1.5

31

1.4

81

1.7

8

MnO

0.8

30.7

90.7

31.5

01.2

01

.41

0.7

40

.59

0.6

81.1

81

.27

1.1

30.5

20

.46

0.5

10.9

61

.05

0.9

0

CaO

10.9

81

0.9

61

0.8

91

1.1

81

1.1

51

1.2

51

0.8

01

0.8

81

1.1

21

1.1

61

1.0

01

1.1

811.5

111.8

211

.51

11.4

41

1.2

51

1.4

3

Na 2

O1

.69

1.7

91.7

11

.90

1.9

41

.81

1.9

31.9

91.9

51.9

21.9

41.8

42.1

72.0

42.1

31.1

31.1

11.1

3

K2

O0.1

70.2

10.1

80

.74

0.7

30.7

50

.20

0.2

20.2

10

.73

0.6

70.6

60

.25

0.2

10.2

60

.73

0.7

20.5

5

Tota

l9

8.0

59

6.1

09

6.9

49

9.0

29

6.9

89

9.5

59

7.9

69

7.2

29

8.6

79

8.2

29

7.9

59

8.4

39

7.0

89

6.1

09

7.6

89

9.5

69

9.0

19

8.4

2

Form

ula

c.f.

Hol

land

and

Blun

dy(1

994)

T-si

tes

Si6.5

16.3

76.4

46

.31

6.4

06.3

06

.43

6.2

96.4

26

.17

6.1

76.2

66

.34

6.4

66.3

36

.79

6.7

66.7

3

AlIV

1.4

91.6

31

.56

1.6

91

.60

1.7

01.5

71.7

11.5

81.8

31.8

31.7

41.6

61.5

41.6

71.2

11.2

41.2

7

Sum

T8.0

08.0

08

.00

8.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

08.0

0

M1–

3si

tes

AlVI

0.2

30.2

70.2

80

.30

0.5

20.4

20.5

50.6

70

.52

0.5

00.4

20

.44

0.3

90.5

20

.44

0.1

90.1

60

.18

Ti0.1

00.1

10.1

10

.08

0.0

80.0

70.0

70.0

60

.07

0.0

60.0

70

.07

0.1

60.1

30

.17

0.1

40.1

50

.13

Fe3+

0.9

31.0

10.9

40

.89

0.5

10.8

20.7

40.7

10

.73

0.8

60.9

70

.86

0.6

00.4

30

.57

0.6

10.6

50

.73

Mg

2.8

32.6

32.7

02

.10

1.8

61.9

72

.36

2.1

62.4

01.9

92.1

02.1

02.8

92.7

02.8

12.4

92.5

02.5

6

Mn

0.1

00

.10

0.0

90.1

90.1

50.1

80

.09

0.0

70.0

80.1

50.1

60.1

40.0

60.0

60.0

60.1

20.1

30.1

1

Con

tinue

don

next

page

...


Tabl

a1

9:A

vera

geam

phib

ole

com

posi

tion

sof

rock

sfr

omth

eTo

tolt

epec

plut

on.

Sam

ple

TT-

14T

T-14

TT-

14T

T-13

aT

T-13

aT

T-13

aT

T-55

TT-

55T

T-55

TT-

54T

T-54

TT-

54T

T-28

TT-

28T

T-28

TT-

17T

T-17

TT-

17

Spec

imen

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

Fe2+

0.8

10

.89

0.8

81.4

31.8

71.5

41

.19

1.3

31.2

01.4

41.2

91.3

90.8

91.1

60.9

41.4

51.4

21.2

9

Sum

M1–3

5.0

05

.00

5.0

05.0

05.0

05.0

05

.00

5.0

05.0

05.0

05.0

05.0

05.0

05.0

05.0

05.0

05.0

05.0

0

M4

site

Fe0.1

10.0

80.0

80.0

50.0

30.0

50

.09

0.0

80.0

70.0

50

.06

0.0

50.0

40

.02

0.0

40.0

60

.08

0.0

5

Ca

1.7

01.7

21.7

11.7

71.8

11.7

71

.69

1.7

21.7

31.7

81

.75

1.7

71.8

01

.83

1.7

91.7

81

.76

1.7

9

Na

0.1

90.2

00.2

10.1

80.1

50

.17

0.2

20

.20

0.2

00.1

70

.18

0.1

70.1

60

.14

0.1

60.1

60

.16

0.1

6

Sum

M4

2.0

02.0

02.0

02.0

02.0

02

.00

2.0

02.0

02.0

02.0

02.0

02.0

02.0

02.0

02.0

02.0

02.0

02.0

0

A-s

ite

Na

0.2

80.3

10.2

80

.37

0.4

20

.34

0.3

30.3

70.3

50.3

80.3

70.3

50.4

50.4

30.4

40.1

60.1

60.1

6

K0

.03

0.0

40.0

30

.14

0.1

40.1

40

.04

0.0

40.0

40.1

40.1

30.1

20.0

50.0

40.0

50.1

40.1

30.1

0

Sum

A0.3

20.3

40.3

20

.51

0.5

60.4

80

.37

0.4

10.3

90

.52

0.5

00.4

80

.50

0.4

70.4

80

.30

0.2

90.2

6

Sum

cati

on1

5.3

21

5.3

41

5.3

21

5.5

11

5.5

61

5.4

81

5.3

71

5.4

11

5.3

91

5.5

21

5.5

01

5.4

81

5.5

01

5.4

71

5.4

81

5.3

01

5.2

91

5.2

6

Al(

tota

l)1.7

21.9

01.8

31

.99

2.1

32.1

12.1

22.3

82.1

02.3

32.2

52.1

82.0

52.0

62.1

11.4

01.3

91.4

5


Tabla 20: Mica compositions of rocks from the Totoltepec pluton, Puebla, Mexico.

Sample TT-13a TT-13a TT-14 TT-14 TT-54 TT-54 TT-54 TT-54 TT-28 TT-28

Specimen Mc-1 Mc-2 Mc-1 Mc-2 Mc-1 Mc-2 Mc-3 Mc-4 Mc-1 Mc-2

wt. %SiO2 46.58 46.32 42.53 43.10 35.42 33.83 35.44 35.44 42.90 42.38

TiO2 0.07 0.08 0.03 0.28 0.05 0.01 0.11 0.12 0.00 0.02

Al2O3 31.44 32.13 32.37 32.34 28.24 28.51 27.94 27.91 34.32 35.18

FeO 3.92 3.83 3.15 2.72 1.80 1.72 1.87 1.89 0.93 0.76

MgO 1.46 1.25 0.81 0.90 1.06 1.05 0.94 0.97 0.12 0.00

MnO 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00

CaO 0.00 0.02 0.02 0.05 0.00 0.01 0.01 0.03 0.00 0.00

Na2O 0.86 0.92 1.19 1.45 0.90 0.89 0.96 0.94 0.26 0.23

K2O 10.41 10.43 10.53 10.12 6.64 7.59 6.57 6.68 12.60 12.66

Cr2O3 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

NiO 0.00 0.00 0.02 0.01 0.03 0.01 0.01 0.00 0.00 0.01

Total 94.75 94.98 90.66 90.99 74.14 73.60 73.85 73.97 91.13 91.24

Formula calculated on the basis of 11 oxygen atoms

T-siteSi 3.17 3.14 3.04 3.05 3.02 2.93 3.03 3.03 3.03 2.99

AlIV 0.83 0.86 0.96 0.95 0.98 1.07 0.97 0.97 0.97 1.01

Sum T 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00 4.00

M-siteAlVI 1.69 1.71 1.76 1.75 1.86 1.85 1.85 1.84 1.89 1.91

Mg 0.15 0.13 0.09 0.10 0.14 0.14 0.12 0.12 0.01 0.00

Fe 0.22 0.22 0.19 0.16 0.13 0.12 0.13 0.13 0.05 0.04

Ti 0.00 0.00 0.00 0.01 0.00 0.00 0.01 0.01 0.00 0.00

Mn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Ca 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Cr 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Ni 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Sum M 2.06 2.06 2.04 2.03 2.12 2.11 2.11 2.11 1.96 1.96

A-siteNa 0.11 0.12 0.17 0.20 0.15 0.15 0.16 0.16 0.04 0.03

K 0.90 0.90 0.96 0.91 0.72 0.84 0.72 0.73 1.14 1.14

Sum A 7.08 7.08 7.16 7.14 7.00 7.10 6.99 7.00 7.13 7.13


Tabl

a2

1:E

nerg

y-di

sper

sive

x-ra

ysp

ectr

osco

py(E

DX

)re

sult

sof

sele

cted

min

eral

sfr

omTo

tolt

epec

plut

onro

cks.

Sam

ple

TT-

514

TT-

514

TT-

514

TT-

514

TT-

514

TT-

14T

T-14

TT-

14T

T-14

TT-

13a

TT-

13a

TT-

13a

TT-

54

Spec

imen

#1#2

#3#4

#5O

p1#1

Op1

#2O

p2#1

Op2

#2Pl

1#1

Pl1#

2Pl

1#3

Am

p3#1

wt.

%Si

O2

1.5

73

0.0

00

30

.61

70

.00

00

.00

00

.00

00

.18

82

5.5

61

0.0

00

0.2

51

0.1

77

0.5

81

0.0

00

TiO2

0.0

00

0.1

08

0.0

45

n.d.

n.d.

46

.78

44

3.3

29

16.8

61

52.6

60

13

.91

14

9.7

79

0.2

14

49

.92

5

Al 2

O3

1.1

94

0.0

00

19

.55

80

.00

00

.00

00

.28

70

.00

09.2

27

0.0

00

0.0

00

0.0

35

0.2

34

0.2

48

FeO

93.9

73

0.1

92

29

.78

70

.00

00

.18

85

1.7

72

55

.05

72

7.1

68

46.5

28

84

.64

84

6.5

62

97

.42

04

3.6

23

MgO

0.7

96

0.1

00

16

.54

40

.00

00

.89

10

.00

00

.46

76.9

15

0.0

00

0.0

00

0.0

00

0.0

00

0.3

10

MnO

0.0

14

0.0

00

1.4

35

0.5

26

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.7

64

1.9

78

0.4

76

4.3

04

CaO

0.1

39

46.9

11

0.1

29

0.0

65

15

.65

60

.13

60

.18

41

3.9

44

0.5

91

0.0

00

0.0

57

0.5

88

0.3

91

Na 2

O2

.16

40.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.0

13

0.6

69

0.0

06

0.9

95

K2

O0

.11

50.0

48

0.0

00

0.0

00

0.0

00

0.0

00

0.0

00

0.3

24

0.0

00

0.1

66

0.0

85

0.0

00

0.0

00

Cr 2

O3

0.0

00

0.0

00

0.4

50

0.0

00

0.0

00

0.1

05

0.5

37

0.0

00

0.0

13

0.0

96

0.2

34

0.4

81

0.0

00

NiO

0.0

00

0.4

88

0.0

00

0.1

14

0.7

83

0.6

13

0.2

36

0.0

00

0.0

31

0.1

51

0.4

25

0.0

00

0.2

04

CuO

0.0

00

0.0

00

0.1

03

0.5

15

0.0

00

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

SO3

0.0

30

0.2

80

0.5

93

32

.64

80

.65

10

.30

30

.00

00.0

00

0.1

77

n.d.

n.d.

n.d.

n.d.

P 2O5

n.d.

51.8

74

0.7

40

0.0

00

1.3

79

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

BaO

n.d.

n.d.

n.d.

66.1

32

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

n.d.

Ce 2

O3

n.d.

n.d.

n.d.

n.d.

80

.45

2n.

d.n.

d.n.

d.n.

d.n.

d.n.

d.n.

d.n.

d.

Tota

l9

9.9

98

10

0.0

01

10

0.0

01

10

0.0

00

10

0.0

00

10

0.0

00

99

.99

81

00.0

00

10

0.0

00

10

0.0

00

10

0.0

01

10

0.0

00

10

0.0

00

Min

eral

Mag

Ap

Chl

Brt

Ce-

carb

onat

eIl

mIl

mTi

-Fe-

Silic

ate

Mag

Ti-M

agIl

mM

agIl

m

n.d.

–no

tde

term

ined

Min

eral

abbr

evia

tion

saf

ter

Whi

tney

yEv

ans

(20

10).


Tabla 21: Energy-dispersive x-ray spectroscopy (EDX) results of selectedminerals from Totoltepec pluton rocks. (cont.)

Sample TT-17 TT-17 TT-17 TT-28 TT-28Specimen Amp2#1 Amp2#2 Amp3#1 Amp1#1 Amp3#1

wt. %SiO2 0.000 3.223 31.016 24.43 0.000

TiO2 0.966 76.356 0.000 43.656 0.000

Al2O3 0.734 0.136 17.259 1.135 0.171

FeO 96.814 16.289 34.596 0.35 25.213

MgO 0.046 0.000 16.141 0 0.000

MnO 0.149 0.465 0.416 0 0.000

CaO 0.000 2.801 0.078 29.921 0.000

Na2O 0.335 0.482 0.139 0 0.000

K2O 0.120 0.000 0.000 0 0.031

Cr2O3 0.836 0.250 0.356 0.466 0.096

NiO 0.000 0.000 0.000 0 0.000

CuO n.d. n.d. n.d. 0 29.630

SO3 n.d. n.d. n.d. 0.042 44.858

P2O5 n.d. n.d. n.d. n.d. n.d.BaO n.d. n.d. n.d. n.d. n.d.Ce2O3 n.d. n.d. n.d. n.d. n.d.Total 100.000 100.002 100.001 100.000 99.999

Mineral Mag Ilm Chl Ttn Ccp

n.d. – not determinedMineral abbreviations after Whitney y Evans (2010).

ETA B L A S G E O C R O N O L O G Í A 40A R / 39A R

Material suplementario publicado en línea como parte del artículo: Kirsch,M., Keppie, J.D., Murphy, J.B., y Lee, J.K.W., Arc plutonism in atranstensional regime: the Late Palaeozoic Totoltepec pluton, AcatlánComplex, southern Mexico: International Geology Review, en prensa, doi:10.1080/00206814.2012.693247.

Tabla 22: 40Ar/39Ar analysis of muscovite sample TT-57 from the Totoltepec pluton.

Step Laser Isotope Volumes∗

Power 40Ar 2σ 39Ar 2σ 38Ar 2σ 37Ar 2σ 36Ar 2σ Ca/K

1 0.5 115.453 0. 411 8.798 0.145 0.260 0.045 0.572 0.769 0.121 0.019 0.119

2 <0.75> 724.844 1.276 61.362 0.364 0.827 0.071 0.849 0.883 0.155 0.020 0.025

3 <1.00> 1717.235 3.381 148.840 0.853 1.923 0.143 0.835 1.480 0.212 0.036 0.010

4 <1.25> 1538.433 2.489 135.730 0.714 1.720 0.133 0.953 1.115 0.104 0.030 0.013

5 <1.50> 1568.868 2.644 137.229 0.853 1.755 0.108 0.941 1.226 0.162 0.033 0.013

6 <1.75> 1326.309 1.736 116.912 0.650 1.494 0.117 0.446 0.767 0.088 0.024 0.007

7 <2.00> 1551.918 3.273 137.506 0.810 1.759 0.104 0.994 1.431 0.087 0.029 0.013

8 <2.25> 614.138 1.157 54.235 0.286 0.680 0.061 0.568 0.585 0.028 0.022 0.019

9 <2.50> 512.826 1.202 45.257 0.348 0.589 0.065 0.276 0.879 0.031 0.017 0.011

10 <2.69> 773.110 1.389 68.506 0.478 0.869 0.060 0.565 0.578 0.051 0.019 0.015

11 <2.86> 824.468 1.242 73.204 0.368 0.941 0.059 0.373 0.885 0.035 0.017 0.009

12 <3.02> 647.662 1.231 57.382 0.355 0.723 0.058 0.584 0.885 0.030 0.019 0.019

13 <7.00> 1349.433 2.196 120.344 0.687 1.573 0.104 1.475 1.034 0.038 0.029 0.022

Note: J-Value = 0,015342± 0,000046∗ Measured volumes are 1× 1012cm3 NTP

146

tablas geocronología40

ar/39ar 147

Tabl

a2

2:40

Ar/39

Ar

anal

ysis

ofm

usco

vite

sam

ple

TT-5

7fr

omth

eTo

tolt

epec

plut

on.(

cont

.)

Step

Lase

rIs

otop

eC

orre

lati

onD

ata

Pow

er%

40

Ar a

tm

%39

Ar

40

Ar/

39

ArK

2σ

Age

(Ma)†

2σ

36

Ar/

40

Ar

2σ

39

Ar/

40

Ar

2σ

r

10

.53

1.0

20

.75

9.0

20.6

72

33

.91

6.3

0.0

01

05

30.0

00

16

90.0

76

37

20.0

01

29

60.0

04

2<

0.7

5>

6.3

16

.02

11.0

40.1

22

82

.22

.90

.00

02

14

0.0

00

02

80.0

84

87

10.0

00

52

70.0

03

3<

1.0

0>

3.6

41

8.7

91

1.0

90.1

02

83

.42

.30

.00

01

23

0.0

00

02

10.0

86

90

10.0

00

52

80.0

04

4<

1.2

5>

1.9

93

0.4

41

1.0

80.0

92

83

.22

.20

.00

00

68

0.0

00

02

00.0

88

46

20.0

00

48

80.0

01

5<

1.5

0>

3.0

54

2.2

21

1.0

50.1

02

82

.62

.40

.00

01

03

0.0

00

02

10.0

87

70

10.0

00

56

60.0

02

6<

1.7

5>

1.9

65

2.2

51

1.0

90.0

92

83

.52

.10

.00

00

66

0.0

00

01

80.0

88

38

30.0

00

50

60.0

01

7<

2.0

0>

1.6

56

4.0

51

1.0

70.0

92

83

.02

.20

.00

00

56

0.0

00

01

90.0

88

84

10.0

00

55

80.0

02

8<

2.2

5>

1.3

46

8.7

01

1.1

40.1

32

84

.73

.20

.00

00

45

0.0

00

03

50.0

88

54

60.0

00

49

70.0

00

9<

2.5

0>

1.7

97

2.5

81

1.1

00.1

42

83

.73

.40

.00

00

61

0.0

00

03

30.0

88

48

50.0

00

71

40.0

00

10

<2

.69>

1.9

67

8.4

61

1.0

30.1

22

82

.12

.70

.00

00

66

0.0

00

02

50.0

88

84

80.0

00

64

20.0

01

11

<2

.86>

1.2

38

4.7

41

1.0

90.0

92

83

.62

.20

.00

00

42

0.0

00

02

10.0

89

02

80.0

00

46

90.0

00

12

<3

.02>

1.3

88

9.6

61

1.1

00.1

22

83

.72

.90

.00

00

47

0.0

00

03

00.0

88

83

60.0

00

57

70.0

00

13

<7

.00>

0.8

39

9.9

91

1.0

90.1

02

83

.52

.30

.00

00

28

0.0

00

02

20.0

89

42

10.0

00

53

20.0

00

†In

tegr

ated

Age

=282

,85±1

,10Ma

;Is

otop

eC

orre

lati

onA

ge=283

,41±3

,68Ma

(99.2

%of39

Ar,

step

sm

arke

dby<

);Pl

atea

uA

ge=283

,22±

1,10Ma

(99.2

%of39

Ar,

step

sm

arke

dby>

);M

SWD

=0.2

48

B I B L I O G R A F Í A

Andersen, T. Correction of common lead in U–Pb analyses that do notreport 204Pb. Chemical Geology 192(1-2):59–79 (2002)

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