Orogenic Gold Andes

Paleozoic orogenic gold deposits in the eastern Central Andes and

its foreland, South America

Yves Haeberlin*, Robert Moritz, Lluıs Fontbote

Section des Sciences de la Terre, Universite de Geneve, Rue des Maraıchers 13, 1211 Geneva 4, Switzerland

Received 14 January 2002; accepted 22 August 2002

Abstract

In the eastern Central Andes and its foreland (6j–34jS), abundant quartz veins emplaced along brittle–ductile deformation

zones in Ordovician to Carboniferous granites and gneisses and in saddle-reefs in lower Paleozoic turbidites represent a

coherent group of middle to late Paleozoic structurally hosted gold deposits that are part of three major Au (F SbFW)

metallogenic belts. These belts, extending from northern Peru to central Argentina along the Eastern Andean Cordillera and

further south in the Sierras Pampeanas, include historical districts and mines such as Pataz–Parcoy, Ananea, Santo Domingo,

Yani–Aucapata, Amayapampa, Sierra de la Rinconada and Sierras de Cordoba. On the basis of the available isotopic ages, two

broad mineralization epochs have been identified, with Devonian ages in the Sierras Pampeanas Au belt (26j to 33j30VS), andCarboniferous ages for the Pataz–Maranon Valley Au-belt in northern Peru (6j50V to 8j50VS). The absolute timing of the

southeastern Peruvian, Bolivian and northwestern Argentinian turbidite-hosted lodes, which form the Au–Sb belt of the

southern Eastern Andean Cordillera (12j to 26jS), is poorly constrained. Field relationships suggest overlap of gold veining

with Carboniferous deformation events. The northernmost belt, which includes the Pataz province, is over 160-km-long and

consists of sulfide-rich quartz veins hosted by brittle–ductile shear zones that have affected Carboniferous granitic intrusions.

Gold mineralization, at least in the Pataz province, occurred a few million years after the emplacement of the 329 Ma host

pluton and an episode of molassic basin formation, during a period of rapid uplift of the host units. The two southern belts are

associated with syn- to post-collisional settings, resulting from the accretion of terranes on the proto-Andean margin of South

America. The Au–Sb belt of the southern Eastern Andean Cordillera presumably formed in the final stages of the collision of

the Arequipa–Antofalla terrane and the Sierras Pampeanas Au belt is considered concurrent with the late transpressional

tectonics associated with the accretion of the Chilenia terrane.

The three Devono–Carboniferous Andean belts are the South American segments of the trans-global orogenic gold

provinces that were formed from Late Ordovician to Middle Permian in accretionary or collisional belts that circumscribed the

Gondwana craton and the paleo-Tethys continental masses. A paleogeographic map of the Gondwana supercontinent in its

Middle Cambrian configuration appears as a powerful tool for predicting the location of the majority of the Paleozoic orogenic

gold provinces in the world, as they develop within mobile belts along its border. The three South American belts are sited in the

metallogenic continuation of the Paleozoic terranes that host the giant eastern Australian goldfields, such as Bendigo–Ballarat

and Charters Towers, with which they share many features. When compared to deposits in the French Massif Central, direct

counterparts of the Andean deposits such as Pataz and Ananea–Yani are respectively the Saint Yrieix district and the Salsigne

deposit. Considering the ubiquity of the Au (F SbFW) vein-type deposits in the Eastern Cordillera and Sierras Pampeanas,

0169-1368/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved.

PII: S0169 -1368 (02 )00108 -7

* Corresponding author.

E-mail address: [email protected] (Y. Haeberlin).

www.elsevier.com/locate/oregeorev

Ore Geology Reviews 22 (2002) 41–59

and the relatively little attention devoted to them, the Devonian and Carboniferous orogenic gold deposits in the eastern section

of the Central Andes constitute an attractive target for mineral exploration.

D 2002 Elsevier Science B.V. All rights reserved.

Keywords: Orogenic gold deposits; Paleozoic; Eastern Central Andes; Peru; Bolivia; Argentina

1. Introduction

In the earth’s history, giant orogenic gold deposits

formed predominantly during four periods, Late

Archean, Early Proterozoic, middle to late Paleozoic,

and Mesozoic –Cenozoic, when plate tectonics

resulted in the accretionary assembly of superconti-

nents (Kerrich and Cassidy, 1994; Goldfarb et al.,

2000, 2001). The formation of lode-gold deposits in

Paleozoic times corresponds to a major epoch of

continental growth that started during the Late Ordo-

vician and continued until the Middle Permian, culmi-

nating with the formation of Pangea (Bierlein and

Crowe, 2000). During this period, the tectonic and

thermal evolution of the convergent plate boundaries

in accretionary and collisional orogen resulted along

the margins of Gondwana and of the peri-Tethys in the

concentration of one billion or more of gold ounces,

deposited in particular in the giant deposits, such as

Bendigo–Ballarat in eastern Australia, and Muruntau

and Kumtor in the Tien Shan (Bierlein and Crowe,

2000). Elsewhere and around-the-world, middle to late

Paleozoic orogenic phases were responsible for the

formation of abundant gold deposits, in the Southern

Appalachians, the Meguma terrane in Nova Scotia and

Newfoundland, the British Caledonides, the European

Variscides, the Inner Mongolia in China, the Buller

Terrane in New Zealand and southern South America

(Bierlein and Crowe, 2000; Goldfarb et al., 2000,

2001). The Paleozoic Andean belts, despite the com-

mon metallogenic heritage of the proto-Pacific margin

of Gondwana from eastern Australia via New Zealand

and Antarctica to South America (Sillitoe, 1992), are

commonly overlooked. Even in recent syntheses (Ker-

rich and Cassidy, 1994; McCuaig and Kerrich, 1998;

Goldfarb et al., 1998, 2001; Groves et al., 1998;

Bierlein and Crowe, 2000), only little attention has

been devoted to the orogenic gold class in the Andes.

Only Sillitoe (1992), in his notes on the gold and

copper metallogeny of the Central Andes, and Noble

and Vidal (1994), in their reinterpretation of the

historical auriferous deposits of Santo Domingo and

Ananea in Peru, draw attention to the existence of large

orogenic gold provinces in the Paleozoic rocks of the

Andes. More recently, the comprehensive re-evalua-

tion of several deposits, such as the numerous Bolivian

Sb–(Au) sediment-hosted mineralizations (Dill et al.,

1997; Dill, 1998), the Peruvian batholith-hosted Pataz

gold lodes (Haeberlin et al., 1999, 2000; Macfarlane et

al., 1999; Haeberlin, 2002), and the Au–Ag–W veins

in the Argentinian Sierras Pampeanas (Skirrow et al.,

2000), highlights that the exposures of early to middle

Paleozoic mobile belts, presumably from northern

Peru to central Argentina, are in fact host of a con-

tinent-scale series of belts of orogenic gold deposits

with subsidiary antimony and tungsten.

The scope of this article is to provide an overall

frame to the poorly known gold deposits related with

the middle to late Paleozoic evolution of the proto-

Andean margin. Several Mesozoic and Cenozoic

orogenic gold belts occur elsewhere along the Andean

Cordillera, e.g. in the Antioquia region in Colombia

(Utter, 1984; Shaw, 2000) and close to Nazca in Peru

(Noble and Vidal, 1994), but they are not considered

here. The first part of this paper is dedicated to the

Pataz–Maranon Valley Au belt, that is currently the

focus of extensive fieldwork, dating and geochemical

studies (Haeberlin et al., 1999, 2000; Macfarlane et

al., 1999; Haeberlin, 2002). In a second part, two

other geographically and tectonically disconnected

metallogenic belts are documented, the Peruvian–

Bolivian–Argentinian Au–Sb belt of the Eastern

Andean Cordillera (12j to 26jS), where only little

information is available relative to the large number of

occurrences, and the Argentinian Sierras Pampeanas

Au belt (26j to 33j30VS), in which combined

regional and metallogenic investigations were carried

out (Skirrow et al., 2000). For these two belts, we

present a geological and structural overview of the

different mines and districts as well as syntheses of

Y. Haeberlin et al. / Ore Geology Reviews 22 (2002) 41–5942

the mineralization styles, ore and alteration para-

geneses, and, if available, the fluid inclusion and

isotopic data. What is known about the timing and

the tectonic setting of the three auriferous belts is

reviewed, followed by a critique of the existing

genetic models. As synthesis, comparisons and con-

trasts are highlighted between the Andean belts and

the aforementioned peri-Gondwanian orogenic gold

provinces, and some perspectives are exposed for

future exploration and research.

For sake of simplicity, we adopt in this paper as well

as in the author citations the term ‘‘orogenic gold de-

posits’’ as defined by Bohlke (1982) and Groves et al.

(1998), instead of the mesothermal, shear zone-hosted,

structurally hosted, or lode-gold terms.

2. The Pataz–Maranon Valley Au belt

The Pataz–Maranon Valley Au belt is situated in the

Eastern Cordillera of the northern Peruvian Andes

(Fig. 1). This mineralized belt, mostly hosted in gran-

itic rock covers at least a 160-km-long region (7j20V–8j50VS), extending first along the eastern side of the

Fig. 1. Situation of the Pataz province in the frame of the orogenic gold belts of the Eastern Andean Cordillera and Sierras Pampeanas.

Y. Haeberlin et al. / Ore Geology Reviews 22 (2002) 41–59 43

Maranon Valley from the Bolıvar to the Pataz district

(Schreiber, 1989; Schreiber et al., 1990; Haeberlin et

al., 1999, 2000; Haeberlin, 2002), then striking to the

southeast to the Parcoy (Vidal et al., 1995; Macfarlane

et al., 1999) and Buldibuyo districts. The later three

districts are part of the Pataz province (Fig. 2). A

northern extension of this belt is likely into the Balsas

district (6j50VS), where similar gold deposit occurren-

ces are documented (Sanchez, 1995). The poorly

known deposits in the Ongon area (8j10VS) southeastof Pataz and in the Huachon area (10j40VS) east ofCerro de Pasco (Noble and Vidal, 1994) could

also belong to this belt, although they are preferen-

tially hosted in metasedimentary rocks.

The Pataz province (Fig. 2) includes numerous

quartz–sulfide veins, located to the east of a major

NNW-striking lineament within a 1- to 5-km-wide

corridor, formed by the western margin and, in the

Parcoy district, also the eastern margin of the Mis-

sissippian calc-alkaline Pataz Batholith at the contact

with Upper Proterozoic to Ordovician volcano-sedi-

mentary rocks. Over the past 100 years, more than 16

underground mines, distributed over the entire prov-

ince produced a total of 6 million ounces of gold (Moz

Fig. 2. Schematic geological map of the Pataz gold province with the location of the main deposits.


Au), mainly from 1925 to 1960 and from 1980

onward. In 2000, the production of the province

amounted to 380,000 oz, which represents about 9%

of the gold produced in Peru. Grades in the mined ore

shoots vary between 7 and 15 g/t Au, and locally

reach about 120 g/t Au. Further resources are esti-

mated at >40 Moz Au for the 160-km-long mineral-

ized belt.

The auriferous veins of the Pataz province share

several typical field characteristics (Table 1), includ-

ing:

(1) Strong lithological and in particular rheological

control; they occur as continuous up to 5-km-long

quartz veins within or along the margin of the

Pataz Batholith, or as smaller, branching ore

shoots within folded Ordovician slates/hornfels.

(2) Constant vein strikes, in particular within the

batholith, where the quartz veins are emplaced

along N- to NW-striking brittle–ductile deforma-

tion zones, dipping 30j to 60j to the east to

northeast, and within reverse fractures. Three

subordinate vein sets include (i) E–W-striking,

shallow-dipping extensional veins, (ii) veinlets

concordant to bedding in the limbs of fold hinges

in the Ordovician slates/hornfels, and (iii) weakly

mineralized lenses within roughly E–W-striking

vertical faults with sinistral displacements.

(3) Consistent Au, Ag, As, Fe, Pb, Zn, FCu, F Sb,

F (Bi–Te–W) metal association, and a two-stage

ore sequence, with a first paragenesis composed

of milky quartz, pyrite, arsenopyrite and ankerite,

and a second assemblage synchronous with a

brittle fracturing event composed of blue-grey

microgranular quartz, galena, sphalerite, chalco-

pyrite, Sb–sulfosalts, electrum and native gold. A

final post-sulfide paragenesis with calcite, dolo-

mite and white quartz in veinlets crosscuts the

earlier parageneses.

(4) Hydrothermal alteration of the wallrock, with

intense bleaching of plutonic wallrocks, due to

pervasive sericitization with minor chloritization,

carbonitization, and pyritization, and almost

invisible to weak sericitization and chloritization

in sedimentary host rocks.

The overall uniformity in H, O, C, S, and Pb isotope

composition of the ore, gangue and alteration minerals

within the entire province (Table 2) is consistent with a

large-scale fluid migration over several tens to hun-

dreds of kilometers (Haeberlin, 2002). Lead isotopes

suggest that the hydrothermal fluids acquired most of

their metal contents through interaction with the con-

duits and host rocks, in particular the Pataz Batholith,

and a non-negligible part from lower crustal rocks.

Similarly, Sr isotopes point to the involvement of a

radiogenic Sr source external to the pluton, either

leached from the Precambrian basement or from

deep-seated gneissic rocks. Fluid inclusion studies

(Table 1) indicate that the ore fluids related to the

early pyrite–arsenopyrite stage are CO2-free brines,

and they post-date low-salinity aqueous carbonic flu-

ids (1–8 wt.% NaCl equivalent) associated with quartz

formation. The decrease of the fluid salinities (from 15

to 5 wt.% NaCl equivalent) with a concomitant drop of

the homogenization temperatures (from 270 to 140 jC)during the gold stage reveals the ingress of a third

and dilute fluid in the hydrothermal system, most

likely downward migrating surface waters. This dilu-

tion and the associated drop in sulfur activity are

interpreted as the main mechanisms responsible for

gold precipitation. Gold deposition occurred at

330F 50 jC according to oxygen and sulfur isotope

geothermometry (Haeberlin, 2002).

2.1. Age, geotectonic setting and genetic hypotheses

In the Pataz province, three mineral separates

from the sericite alteration intimately associated

with the gold-bearing lodes yield overlapping40Ar/39Ar plateau ages between 314 and 312 Ma

that are interpreted as the closest approximation,

although they are minima, of the mineralization age

(Haeberlin et al., 1999; Haeberlin, 2002). The 325–

322 Ma 40Ar/39Ar plateau dates obtained for mus-

covite and biotite separates from an aplite dyke, i.e.

the youngest magmatic pulse of the Pataz Batholith,

represent the upper age limit of the mineralization

(Haeberlin, 2002). The main host rock and major

component of the Pataz Batholith, the granodiorite,

has a U/Pb zircon age of 329F 1 Ma near Parcoy

(Vidal et al., 1995), and two consistent 40Ar/39Ar

biotite plateau ages of 329.2F 1.4 and 328.1F1.2

Ma near Pataz (Haeberlin, 2002). To the north, the

prolongation of the Pataz Batholith, the Callangate

pluton near Bolıvar and the Balsas pluton near Balsas


Table 1

Geological setting, structural characteristics, ore, gangue and alteration parageneses, and fluid inclusion data of the main Paleozoic orogenic gold deposits in the eastern Central Andes

and its foreland

Belts Pataz–Maranon Valley Southern Eastern Andean Cordillera Sierras Pampeanas

Northern Peru Southeastern Peru

(Cordillera de Carabaya)

North Bolivia

(Cordillera Real)

Central and

South Bolivia

Northwestern

Argentina

West-central

Argentina

Major district(s) Balsas, Bolıvar,

Pataz, Parcoy,

Buldibuyo

La Rinconada,

Santo Domingo

placers: Madre de

Yani–Aucapata

placers: Beni basin

Antofagasta,

Amayapampa,

Santa Rosa de

Capasirca,

Cebadillas,

Candelaria, Sucre

Incahuasi

(Catamarca),

Sierra de la

Rinconada–Sto.

Domingo–Farillon

(Jujuy)

Sierra de la

Culampaja

(Catamarca),

Sierra de las

Minas–Ulapes

(La Rioja),

Rıo Candelaria–

San Ignacio

Dios basin (Cordoba)

Host rock(s) Carboniferous granitoids,

Ordovician slates,

Upper Proterozoic

phyllites

lower Paleozoic

turbiditic sequences

Ordovician shales

and sandstones

lower Paleozoic

turbiditicsequences

Ordovician shales

and quartzites

Cambrian paragneiss

and migmatites,

Ordovician granites,

Devonian mylonites

Age of veining z 314–312 Ma

(40Ar/39Ar sericite)

VCarboniferous

folding

VCarboniferous

folding

VCarboniferous

folding

VCarboniferous

folding

Sierra de las Minas:

393–382 Ma,

>238 Ma old

(Lancelot et al., 1978)

>226 Ma old

(Farrar et al., 1990)

Sierras de Cordoba:

378–351 Ma

Coasa Batholith Zongo intrusion (40Ar/39Ar sericite)

Tectonic setting close to NNW-striking

first-order structures

close to a NW-striking

first-order structure

related to

anticlines

related to

anticlines

close to first-order

structures, locally in

mylonite zone

Structural style brittle–ductile

quartz veins,

bedding-concordant

vein(let)s

brittle quartz veins,

stockworks, bedded

massive sulfide layers,

stockworks

ductile quartz vein(let)s,

saddle reefs, bedded

massive sulfide layers

saddle reefs,

brittle–ductile

quartz vein(let)s

brittle–ductile

quartz veins,

saddle reefs

brittle–ductile

quartz veins,

shear zones,

stockworks, en

echelon gash veins

Y.Haeberlin

etal./Ore

GeologyReview

s22(2002)41–59

46

Ore mineralsa I: py–asFwf I: py–po–as–sch I: py–as–sch–Au I: py–as I: as–py–po–el Au–el–pyF cp–

II: gn–sl–py–as–

AuF cp–po–el– fh

II: cp–sl–gn–ant–

AuF fh–mo

II: gn–sl–cp–po–

AuF el

IIa: ant–sl – jm–cp–

AuFwf–gn

II: gn–sl–py–

cp–po–sfs–Au

gn–sl–as–po

IIb: ant– jm–py–

AuF sfs

III: ant–sfs

Economic metal(s) AuFAg Au–Sb Au–W Sb–Au Au AuFAgFCu

Au grades 5–30 g/t 10–25 g/t, up to

2 kg/t

up to 300 g/t 2–15 g/t, often as

by-product

0.5–40 g/t 0.2–25 g/t,

up to 180 g/t

Gold production 380,000 oz/year 500,000 oz/year

(including placers)

100,000 oz/year

(placers)

? f 100 oz/year ?

Gangueb milky qz I, grey-blue

qz II, ser, chl, fuch,

ank, dol, ca, sp

white qz I, blue-grey

qz II, chl, ser, ep,

sp, ank

milky qz I, grey-blue

qz II, chl, alb, sidF bar

milky qz, sid, ank,

caF bar

qz I, qz II, chl,

ser, ank, gr

milky qz,

grey qz, ca

Wallrock

alteration

sericitization,

chloritization,

pyritization,

silicification

chloritization,

silicification,

sericitization,

pyritization

silicification,

chloritization

sericitization,

chloritization

chloritization,

sericitization

sericitization,

chloritization,

pyritization

Fluid inclusions early: H2O–NaCl–CO2

(1–8 wt.% NaCl

equivalent) and

syn: H2O–NaCl

(5–15 wt.% NaCl

equivalent)

H2O–NaCl

(18–30 wt.% NaCl

equivalent) and

H2O–CO2FNaCl

H2O–NaClFCO2

(5–15 wt.% NaCl

equivalent) and

H2O–CO2

H2O–NaCl–CO2

(6–18 wt.%

NaCl equivalent)

References Schreiber (1989);

Schreiber et al. (1990);

Vidal et al. (1995);

Macfarlane et al. (1999);

Haeberlin et al.

(1999, 2000);

Haeberlin (2002)

Fornari et al. (1988);

Clark et al. (1990);

Fornari and Herail

(1991)

Tistl (1985);

Fornari and Herail

(1991)

Lehrberger (1992);

Richings (2000);

for Sb-deposits:

Ahlfeld and

Schneider-Scherbina

(1964); Dill et al.

(1997); Dill (1998)

Sureda et al.

(1986);

Zappettini and

Segal (1998)

Lazarte (1992);

Rıos Gomez

et al. (1992);

Lyons et al. (1997);

Pieters et al. (1997);

Sims et al. (1997);

Skirrow et al.

(2000)

a Ore mineral abbreviations: as = arsenopyrite, ant = antimonite, Au = native gold, cp = chalcopyrite, el = electrum, fh = fahlore, gn = galena, jm = jamesonite, mo =molybdenite,

po = pyrrhotite, py = pyrite, sch = scheelite, sfs = sulfosalts, sl = sphalerite, wf =wolframite.b Gangue mineral abbreviations: alb = albite, ank = ankerite, bar = barite, ca = calcite, chl = chlorite, dol = dolomite, ep = epidote, fuch = fuchsite, gr = graphite, kf = k-feldspar,

qz = quartz (I: early, II: syn-gold), ser = sericite (hydrothermal muscovite), sid = siderite, sp = sphene.

Y.Haeberlin

etal./Ore

GeologyReview

s22(2002)41–59

47

yielded K/Ar biotite ages for granodiorites and gran-

ites ranging between 347F 7 and 329F 10 Ma

(Sanchez, 1995). The combination of these isotopic

ages (Fig. 3) suggests that the short-lived Au miner-

alization event post-dates the studied main magmatic

differentiation products of the Pataz Batholith (Hae-

berlin, 2002). This assumption, if confirmed region-

ally by supplementary U/Pb zircon ages, would

imply that there is no genetic link between gold-

bearing veining and the Pataz Batholith. This view is

consistent with the field and geochemical data sum-

marized above, and questions the magmatic models

proposed by Schreiber et al. (1990), Vidal et al.

(1995), Sillitoe and Thompson (1998), and Macfar-

lane et al. (1999). Similarly, neither volcanic record,

nor any regional metamorphism coincides in space

and time with the hydrothermal gold mineralization

event (Fig. 3).

At Pataz, and presumably in the Eastern Cordillera

north of 12jS, the regional setting prevailing during theMississippian immediately before gold ore formation is

characterized by widespread calc-alkaline plutonism

and molasse-type sedimentation in transtensional

basins with sporadic basaltic and gabbroic magmatic

episodes. The gold mineralization event occurred

after the igneous activity, during a period of rapid

uplift of the host basement. Indirect observations

supporting the uplift tectonics are the early deposi-

tion of eroded granitic clasts in the Mississippian

basins, following the denudation of the calc-alkaline

intrusions, and an emersion gap in the lower Penn-

sylvanian sedimentary sequences of the northern

Peruvian Eastern Cordillera (Haeberlin, 2002). This

interpretation is confirmed by the fluid inclusion

history and in particular the isochore calculations,

that indicate a sudden decompression during vein

Table 2

Stable and radiogenic isotope compositions of the ore, gangue and alteration minerals for the main Paleozoic orogenic gold deposits in the

eastern Central Andes and its foreland

Belts Pataz–Maranon Valley

Northern Peru

Southern Eastern Andean Cordillera

Central and South Bolivia

Sierras Pampeanas

West-central Argentina

Studied district(s) Pataz, Parcoy Antofagasta, Cebadillas, Santa

Rosa de Capasirca, Candelaria,

Sucre

Sierra de las Minas–Ulapes (La

Rioja), Rıo Candelaria–San

Ignacio (Cordoba)

dD (SMOW, x) sericite � 60 to � 39 (n= 12) sericite � 125 to � 86 (n= 5)

d18O (SMOW, x) quartz 10.9 to 14.2 (n= 10) quartz 12.0 to 17.6 (n= 14)

sericite 7.3 to 9.9 (n= 8) sericite 8.4 to 13.4 (n= 5)

ankerite 8.9 to 9.8 (n= 5) ankerite 12.8 to 17.9 (n= 11)

siderite 14.5 to 19.2 (n= 6)

d13C (PDB, x) ankerite � 5.6 to � 5.2 (n= 5) ankerite � 16.5 to � 7.9 (n= 11)

siderite � 14.8 to � 6.6 (n= 6)

d34S (CDT, x) sulfide mineralsa � 1.7 to 3.7 (n= 44) sulfide mineralsb 1.5 to 10.0 (n= 8)

Pb isotopes 206Pb/204Pb galena 18.35–18.46 (n= 21)207Pb/204Pb 15.62–15.69208Pb/204Pb 38.26–38.50

Sr isotopes 87Sr/86Sr ankerite 0.7096–0.7146 (n= 5)

References Vidal et al. (1995); Haeberlin (2002) Lehrberger (1992) Skirrow et al. (2000)

a Sulfide minerals: arsenopyrite, chalcopyrite, galena, pyrite, sphalerite.b Sulfide minerals: galena, pyrite, sphalerite, sulfosalt.

Fig. 3. Timing of Paleozoic orogenic gold deposits in the eastern Central Andes and its foreland relative to the main orogenies and intrusions in

the three defined belts. Mineralization ages are derived from 40Ar/39Ar dates of the sericite alteration associated to the gold lodes for the Pataz–

Maranon Valley Au belt and the Sierras Pampeanas Au belt, and are on account of field relationships for the Au–Sb belt of the southern Eastern

Andean Cordillera.



formation that can be related to a rapid uplift of the

host units (Haeberlin, 2002).

3. The Au–Sb belt of the southern Eastern Andean

Cordillera

The Au–Sb belt situated along the Eastern Andean

Cordillera from the north of Cuzco in Peru to the

south of Salta in northwestern Argentina (12j to

26jS, Table 1 and Fig. 1) includes lode-gold and

antimony deposits, generally hosted by lower Paleo-

zoic turbiditic sequences. The intrusion-related Sn–

W–Au vein-type deposits in southeastern Peru (Clark

et al., 1990) and epithermal Sb mineralization in

Bolivia (Dill et al., 1995, 1997) are not considered,

since they belong to Triassic–Early Jurassic and

Tertiary metallogenic epochs, respectively. Reported

and documented gold deposits and mines in the Au–

Sb belt of the southern Eastern Andean Cordillera

include Ananea and Santo Domingo in southeastern

Peru (Soler et al., 1986; Fornari et al., 1988; Clark et

al., 1990; Fornari and Herail, 1991), Yani–Aucapata

in the Bolivian Cordillera Real (Tistl, 1985; Fornari

and Herail, 1991), Amayapampa (Richings, 2000),

Antofagasta, Cebadillas, Santa Rosa de Capasirca,

Candelaria and Sucre (Lehrberger, 1992) in central

and southern Bolivia, Sierra de la Rinconada in north-

western Argentina (Sureda et al., 1986; Zappetini and

Segal, 1998), and Bolivian antimony vein-type depos-

its, such as San Bernardino, San Luıs, Virgina, Chur-

quini, Huarojla, Chichena, San Carlos (Ahlfeld and

Schneider-Scherbina, 1964; Lehrberger, 1992; Dill et

al., 1997; Dill, 1998). Most of these deposits were

initially mined on a very small scale by the indigenous

population prior to the Spaniard conquest, and small-

scale mining continued through the Spanish colonial

period and then until modern times. The historic Santo

Domingo mine was one of the richest deposits, with

reported free gold wires and grades up to 2 kg/t Au

(Fornari et al., 1988). To our knowledge, corporate

mining is presently restricted to the Ananea region,

where both vein-type ores and fluvioglacial placers

are exploited (f 100,000 oz/year, of which one-

eighth comes from the bedrock), and to the Amaya-

pampa area, where feasibility studies are in progress

(Richings, 2000). Furthermore, these primary deposits

are likely the dominant gold sources for the large

placer deposits of the Subandean Madre de Dios and

the Beni basins (Fornari et al., 1988; Sillitoe, 1992).

Yearly production from these placer deposits amounts

to f 400,000 oz in Peru and f 100,000 oz in

Bolivia, respectively.

At a regional scale, the turbidite-hosted deposits

generally occupy the flanks of regional anticlines or

subsidiary thrust faults close to major tectonic boun-

daries. The mineralized bodies show very different

geometries relative to folds, including straight cross-

cutting brittle–ductile veins and veinlets, saddle-reefs,

bedding-concordant veins, locally known as ‘‘man-

tos’’, and disseminated ores. In many places, the Au–

Sb mineralization appears to be in close spatial

relationship with dark layered rocks interpreted either

as black carbonaceous shales or chlorite-rich mylon-

ites (Fornari et al., 1988; Fornari and Herail, 1991;

Lehrberger, 1992; Dill et al., 1997; Dill, 1998). Con-

trasting with the multiple shapes of the deposits, their

mineralogy is rather uniform with two to three suc-

cessive events in the ore paragenesis, consisting of

early pyrite–arsenopyrite and minor W-bearing min-

erals with milky quartz, and gold occurring as crack

fillings in the second stage with Pb–Zn–Cu-bearing

sulfide minerals, Sb-bearing minerals and blue-grey

microgranular quartz (Table 1). In most Bolivian

occurrences, antimony is the dominant metal and

stibnite, falhore, berthierite, and jamesonite, were

formed either towards the end of the second stage

and/or during a low-temperature third stage (Lehr-

berger, 1992; Dill et al., 1997; Dill, 1998). This Sb–

Au association, typical of shallow-level deposits

(McCuaig and Kerrich, 1998), has been widely docu-

mented in other Paleozoic orogenic gold belts, such as

in the French Massif Central (Bouchot et al., 1997), in

the Meguma terrane of Nova Scotia (Kontak et al.,

1996) and in the New England fold belt of eastern

Australia (Ashley and Craw, 2000). The presence of

scheelite-only deposits in the Yani district (Tistl,

1985) suggests that, in southeastern Peru and northern

Bolivia, deeper and higher-temperature parts of the

mineralized systems are also preserved. Nonetheless,

as shown by the homogeneous alteration styles and

assemblages, that consist of almost invisible to mod-

erate sericitization and chloritization (Clark et al.,

1990; Fornari and Herail, 1991), most of the Au

deposits are emplaced under lower greenschist con-

ditions. Interestingly, and similarly to Pataz, the pres-


ence of abundant blue-grey fine-grained quartz is the

best guide for high-grade gold ores (Tistl, 1985;

Fornari et al., 1988; Clark et al., 1990; de Montreuil,

1995). Fluid inclusions have been studied in the Au–

Sb Bolivian deposits by Tistl (1985), Lehrberger

(1992), Dill et al. (1997) and Dill (1998). They have

described H2O–NaCl–CO2, CO2-rich, and H2O–

NaCl fluids (Table 1). However, it is unclear from

these contributions which inclusion type represents

the hydrothermal fluid responsible for the gold min-

eralization. Finally, carbon and oxygen isotope data

on late ferroan carbonates (Table 2) from five central

and southern Au–Sb Bolivian deposits suggest con-

tributions to the hydrothermal fluids of isotopically

light biogenic CO2 according to Lehrberger (1992),

possibly derived from organic matter trapped in the

neighboring sedimentary rocks.


There is no radiometric dating available yet on the

Au–Sb belt of the southern Eastern Andean Cordil-

lera, except an ambiguous 227 Ma K/Ar age from the

Yani district mentioned in Fornari and Herail (1991).

This age, measured on muscovite coming from a mine

in the contact aureole of the Zongo intrusion, coin-

cides with two essentially identical U/Pb zircon ages

for the intrusion of 226 and 222 Ma (Farrar et al.,

1990). Therefore, it remains unclear whether it repre-

sents the age of the thermal metamorphism or that of

the hydrothermal event. The subsequent age discus-

sion is henceforth exclusively on account of indirect

arguments (Fig. 3).

Clark et al. (1990) noted that the slate-hosted Au–

Sb deposits in the Ananea region are locally over-

printed by Sn–W–Au intrusion-related mineraliza-

tions. The latter are dated at 143F 10 Ma by K/Ar

in the Gavilan de Oro deposit. Therefore, Clark et al.

(1990) also favor a cogenetic interpretation, that is, a

Jurassic age for the Au–Sb lodes. As stated by Tistl

(1985) in the neighboring Yani district, the restriction

of these Au–Sb deposits to the Siluro–Ordovician

turbidites, and their total absence in nearby Permo-

Triassic and Jurassic (Lancelot et al., 1978; McBride et

al., 1983, 1987; Farrar et al., 1990) intrusive bodies,

makes a Jurassic age unlikely. We share this interpre-

tation and consider the Au–Sb deposits, from south-

eastern Peru to northwestern Argentina, to be

synchronous with, or to post-date the regional folding

and metamorphism affecting the Siluro–Ordovician

units (Fig. 3). In Peru and North Bolivia, these

deformations have been attributed on account of strati-

graphic constraints to the Late Devonian–early Mis-

sissippian ‘‘Eohercynian’’ orogeny (Laubacher, 1978;

Martinez, 1980; Dalmayrac et al., 1980). A 40Ar/39Ar

whole rock age of 347 Ma for a slate (McBride et al.,

1987) is in agreement with this interpretation. In

southern Bolivia, recent K/Ar determinations from

phyllosilicates of the Ordovician slates have provided

younger ages within the 320–290 Ma interval, indi-

cating a late ‘‘Hercynian’’ orogeny (Jacobshagen et al.,

2002). Since the emplacement of the Au–Sb ores

overlaps in many deposits the waning stages of the

regional deformation and metamorphism (Lehrberger,

1992; Dill et al., 1997), the mineralizing event may be

mostly Carboniferous in age (Fig. 3). This orogenic

phase is related to the final collision of the Arequipa–

Antofalla terrane on the Amazonian craton (Martinez,

1980; Dalmayrac et al., 1980; Forsythe et al., 1993).

Accurate timing of the mineralizing event(s) requires

testing by isotopic dating.

Because of the age ambiguity, the formation of the

Au–Sb belt of the southern Eastern Andean Cordillera

is the subject of an ongoing controversy, analogous to

the conflicting ideas about sediment-hosted gold prov-

inces elsewhere. On account of their geographic but in

our view possible fortuitous spatial association,

Petersen (1960) initially proposed a genetic relation-

ship between the distal Au–Sb veins of Ananea and

the proximal Sn–W–Au granite-related veins of Con-

doriquena in an intrusion centered-system. Corrobo-

rating this idea, Clark et al. (1990) estimated that the

gold-bearing fluids of the SE Peruvian deposits were

derived from granitoid magmas or from extensive

metamorphic aureoles surrounding batholiths. In con-

trast, French authors, influenced by the prevailing

genetic interpretations about the Salsigne deposit in

the early 1980s (Bonnemaison et al., 1986), postulated

that the Ananea deposits were syngenetic and exhala-

tive-sedimentary deposits (Fornari and Bonnemaison,

1984; Fornari and Herail, 1991). According to the later

authors, the so-called ‘‘auriferous massive sulfides’’ or

‘‘mantos’’ were related to submarine hydrothermal

sources in an aborted rift environment. Tistl (1985),

although noting similarities with orogenic gold depos-

its in greenstone belts, suggested that the formation of


the neighboring Yani lodes were due to remobilization

of sulfide mineral layers during contact metamor-

phism. For the central and southern Bolivian Sb–Au

deposits, Lehrberger (1992) adopted a comparable

metallogenic model, to account for the apparent asso-

ciation with black shales, invoking the mobilization of

metals by hydrothermal convective systems from

metal-enriched horizons, and their later precipitation

in structural traps. Dill et al. (1997) proposed for the

Bolivian sediment-hosted Sb deposits their generation

through metamorphogenic processes remobilizing pre-

concentrated Sb in the host environment, and further

classified them as a subgroup of the orogenic gold

class. Finally, accepting the genetic model proposed in

Fornari and Bonnemaison (1984), Zappettini and

Segal (1998) interpreted the Au saddle-reefs of the

Sierra de la Rinconada as resulting from exhalative

processes. The aforementioned genetic hypotheses are

not entirely satisfactory. The discordant geometries of

the mineralizations and the alteration overprints are not

compatible with the sedimentary-exhalative models.

Age constraints are not well established, but if our

interpretation about the middle to late Paleozoic age

for the mineralization is correct, it has the consequence

that the plutonic and contact metamorphic models are

questionable, since the intrusions are Triassic to Juras-

sic in age (Lancelot et al., 1978; McBride et al., 1983,

1987; Farrar et al., 1990; Fig. 3).

4. The Sierras Pampeanas Au belt

The Sierras Pampeanas in west-central Argentina

(26j to 33j30VS) have been a historical producer of

Au and W, yet the subject of few published studies on

their ore deposits. In the first major synthesis, Skirrow

et al. (2000) present a comprehensive metallogenic

framework based on a multidisciplinary approach,

including detailed mapping, and focus on the nature

of the abundant lode-gold deposits and occurrences. In

this Au belt, the main documented districts (Table 1

and Fig. 1) are from north to south, Sierra de la

Culampaja in Catamarca Province (Lazarte, 1992),

Rıo Candelaria and San Ignacio (Sierras de Cordoba)

in Cordoba Province (Lyons et al., 1997; Gonzalez

and Mas, 1998; Skirrow et al., 2000), Sierra de las

Minas in La Rioja Province (Rıos Gomez et al., 1992;

Cangialosi and Baldis, 1995; Pieters et al., 1997;

Skirrow et al., 2000), and Santo Domingo in San Luıs

Province (Sims et al., 1997; Skirrow et al., 2000).

Resources from the Candelaria and San Ignacio dis-

tricts are estimated at 60,000 and 40,000 oz of gold,

respectively (Skirrow et al., 2000).

In summary, and following essentially the field

observations presented in Skirrow et al. (2000), most

of the gold occurrences are situated in shear or

mylonitic zones within Cambrian to Devonian gneis-

sic and granitic rocks, generally in the vicinity of

transpressional structures. The deposits display a

diversity of structural styles, with mainly quartz veins

in brittle–ductile deformation zones, and subsidiary

stockworks, en-echelon gash veins and siliceous

zones. The mineralized structures show uniformly

low- to moderate-temperature alterations, with a prox-

imal intense sericitization and distal propylitization

and chloritization. The mineral assemblages consist

systematically of abundant milky and blue-grey

quartz, pyrite, gold/electrum, minor carbonate miner-

als, and in places minor chalcopyrite, galena, sphaler-

ite, arsenopyrite and rare pyrrhotite. In the southern

Sierras Pampeanas, fluid inclusion studies indicate

that H2O–CO2–NaCl and H2O–NaCl fluids are

involved in the gold ore precipitation (Gonzalez and

Mas, 1998; Skirrow et al., 2000). Deuterium and

oxygen isotope compositions (Table 2) reveal the

contribution to the hydrothermal fluids of either

Deuterium-depleted meteoric waters that have reacted

extensively with metasedimentary rocks, or fluids

derived from degassed magmas, or a mixture of both,

and oxygen isotope geothermometry indicate ore for-

mation temperatures around 300 jC (Skirrow et al.,

2000).

In addition to the lode-gold-bearing deposits,

three main styles of middle to late Paleozoic tung-

sten-bearing mineralizations, locally with significant

gold content, have been recognized in the southern

Sierras Pampeanas: (1) quartz–muscovite–tourma-

line veins containing wolframite, scheelite and sul-

fide minerals, (2) scheelite associated with calc-

silicate rocks, and (3) disseminated scheelite with

quartz veins in metasedimentary sequences (de

Brodtkorb and Brodtkorb, 1977; Skirrow et al.,

2000). Finally, Ag–Pb–Zn veins belonging to the

same metallogenic epoch are described in the El

Guaico district in Cordoba Province (Sureda, 1978;

Skirrow et al., 2000).



The 40Ar/39Ar step-heating ages of the sericite

alteration associated with the gold-bearing deposits

in the Sierra de las Minas and Rıo Candelaria/San

Ignacio districts are in the range 393–382 and 378–

351 Ma, respectively (Skirrow et al., 2000; Fig. 3).

The younger gold metallogenic epoch overlaps

the f 365 Ma muscovite ages of WFCu-bearing

vein- and replacement-type mineralizations in the

Aguas de Ramon district in Cordoba Province, and

the El Morro district in San Luıs Province. At a

regional scale, the later Au and W deposits post-date

by 20 to 30 m.y. (see Goldfard et al., 2001) the 404 to

382 Ma (Stuart-Smith et al., 1999) peraluminous to

metaluminous granites, whereas the gold lodes in the

Sierras de las Minas are apparently a disconnected

event, broadly synchronous with this felsic magma-

tism (Fig. 3). The younger mineralizing event occurs

during the final stages of the Devonian Achalian

orogeny, an inferred collisional event resulting from

the accretion of the Chilenia terrane on the proto-

Andean margin (Sims et al., 1998; Stuart-Smith et al.,

1999). The second Au- and W-bearing veining over-

laps the 40Ar/39Ar age determinations from phyllosi-

licates of shear zones presented in Sims et al. (1998),

which yielded ages within the 376–351 Ma interval

for the thrust and sinistral, strike-slip shearing tecton-

ics (Fig. 3). Based on the event chronology, the

collisional context, and the structural styles, most of

the gold could be attributed to the orogenic deposit

class. Exceptions are the Cu-rich Au deposits in the

Sierra de las Minas district, which, given their slightly

older ages overlapping with the intrusion ages, the

presence of significant Cu, and higher fluid salinity,

may represent a hybrid style with characteristics of

both the orogenic gold style and intrusion-driven

systems (Skirrow et al., 2000).

5. Discussion

5.1. Summary of the unifying features

The middle to late Paleozoic lode-gold deposits

with subsidiary Sb and W in the eastern Central Andes

and its foreland represent a coherent group of oro-

genic gold deposits with common regional, structural

and temporal features irrespective of the host terranes.

The documented deposits in the Pataz province, the

southern Eastern Andean Cordillera and the Sierras

Pampeanas formed late in the orogenic history, and

are hosted by subsidiary thrust faults in the hanging

wall of lithospheric-scale structures or within regional

anticlines. Small changes in the nature and style of the

individual deposits may reflect the local influence of

the host rocks, and in particular their rheological

properties and geochemical compositions. Thus, com-

petent granitic plutons host regular brittle–ductile

quartz veins, while anisotropic low-metamorphic tur-

biditic sequences present a variety of deposit geo-

metries, such as saddle-reefs, bedding-concordant

veins, stockworks and disseminated ores. Similarly,

the metal associations of the mineralized lodes are

also controlled by the host lithology, with preferen-

tially an Au, Ag, Pb, Zn, Cu, As (Pataz) and W

(Sierras Pampeanas) assemblage in granites, and an

Au, Sb, W assemblage in turbidites. In most of the

Andean deposits, as in the majority of Phanerozoic

deposits worldwide (Bierlein and Crowe, 2000),

arsenopyrite and minor scheelite and wolframite

appear early in the quartz–carbonate–pyrite veins,

gold and silver precipitate with the second-stage

galena–sphalerite–chalcopyrite paragenesis, and a

late stage stibnite and Sb–sulfosalt paragenesis typi-

cally in the shallower parts of the mineralizing sys-

tems. Alteration patterns with variable degrees of

sericitization, carbonitization and chloritization devel-

oped within narrow aureoles surrounding the gold-

bearing structures, indicating that these deposits

formed under lower- to mid-greenschist conditions.

The documented Andean deposits display many

characteristics, in particular their structural style, para-

genesis, metal association and alteration, similar to

other major Paleozoic orogenic gold provinces, such

as the Australian Lachlan and Thomson fold belts

(Solomon and Groves, 1994; Foster et al., 1998;

Ramsay et al., 1998; Bierlein et al., 2000), the French

Massif Central (Bouchot et al., 1997), and the Cana-

dian Meguma terrane (Ryan and Smith, 1998). In our

view, analogues of the Pataz deposits may be the Saint

Yrieix district in the French Massif Central (Bouchot

et al., 1989) and the Charters Towers–Etheridge ore-

field in eastern Australia (Peters and Golding, 1989;

Bain et al., 1998). Similarly the Ananea district and

the neighboring southern Yani district can be com-


pared to the Salsigne deposit in France (Lescuyer et

al., 1993).

5.2. Timing of mineralization

According to relative ages of the collisional events,

and isotopic ages of intrusions and ore-related alter-

ations, two broad episodes of gold veining are recog-

nized during Paleozoic times in the eastern Central

Andes, and are consistent with the separate tectonic

evolution of the main cordilleran domains, whereby

the ages become younger to the north: Devonian in

the southern Sierras Pampeanas Au belt and Carbon-

iferous for the northern Pataz–Maranon Valley Au

belt (Fig. 3). A third episode, mostly Carboniferous,

was inferred on account of field relationships for the

Au–Sb belt of the southern Eastern Andean Cordil-

lera (Fig. 3). The northernmost deposits at Pataz were

formed in an uplifting region characterized by calc-

alkaline plutonism and molasse-type sedimentation in

transtensional basins. The two southern belts formed

within collisional settings related to terrane accretions

onto Precambrian to early Paleozoic cratons to the

east. Despite the broad spatial relationship between

felsic intrusions and a large number of the Central

Andean orogenic gold deposits, there is no evidence

in most documented deposits for a genetic link

between both events. With the possible exception of

the small Au–Cu deposits in the Sierra de las Minas,

the available data indicate that the plutons either pre-

or post-date the lode-gold mineralizations, and gen-

erally only served as a favorable rheological host for

extensive vein opening. In fact, all three Andean gold

belts, despite their separate histories, were formed

during or shortly after the late stages of the evolution

of orogens (Fig. 3), coevally with either regional uplift

or transpressional strike–slip tectonics (Skirrow et al.,

2000; Haeberlin, 2002). This late-kinematic timing

and the convergent plate boundary location are fully

consistent with the orogenic gold class concept as

defined in Groves et al. (1998).

5.3. The circum-Gondwana orogenic gold belt

On the basis of recent advances in isotopic dating

of the deposits, Bierlein and Crowe (2000) and Gold-

farb et al. (2001) pointed out that the circum-Gond-

wana margin and the continental masses around the

closing paleo-Tethys Ocean account for the location

of most of the middle to late Paleozoic gold orogenic

provinces in the world. These include gold districts in

the Lachlan, New England, Hodgkinson and Thomson

fold belts in eastern Australia, Westland in New

Zealand, the Southern Appalachians, the Meguma

province in Nova Scotia and Newfoundland, the

British Caledonides, the European Variscides with

the Iberian, French Central and Bohemian Massifs,

the Tien Shan in Central Asia and the Inner Mongolia

in Northeast China. The tectono-thermal processes

generating gold deposits in these provinces took place

from the Late Ordovician to the Middle Permian, a

long period characterized by global continental

growth on the Gondwana supercontinent and on the

paleo-Tethys continental masses (Goldfarb et al.,

2001). In this perspective, the auriferous belts of the

Pataz–Maranon Valley, the southern Eastern Andean

Cordillera and the Sierras Pampeanas are the South

American pieces of this trans-global belt of orogenic

gold deposits (Fig. 4).

A paleogeographic reconstruction of the Gond-

wana supercontinent in its Cambrian configuration

(Fig. 4) reveals, at a very large scale, the regions that

are the most prospective hosts of middle to late

Paleozoic orogenic gold provinces, since these will

develop subsequently within terranes along its margin.

Most of the major known middle to late Paleozoic

orogenic gold provinces in the world, with the notable

exception of the Uralides, which resulted from the

collision of Kazakstania and Euamerica, and other

East Russian provinces (Goldfarb et al., 2001), can be

placed on the reconstruction of Fig. 4. The paleogeo-

graphical reconstruction of the Gondwana superconti-

nent during Cambrian times may be used as a

predictive tool for locating previously unrecognized

orogenic gold provinces and districts that may have

form during Paleozoic times. Based on this recon-

struction, the Ross Orogen in the Antarctic continent,

the Mauritanides in Northwest Africa, Indochina and

Burma appear potentially among the most prospective

regions for the discovery of new Paleozoic orogenic

gold resources (Fig. 4).

5.4. Exploration and research perspectives

Unlike epithermal systems, relatively little atten-

tion has been devoted in the Andes to the attractive


potential of the Devonian and Carboniferous oro-

genic gold belts. Considering the ubiquity of the Au

(F SbFW) lodes, some of them known since the

Inca epoch (15th–16th centuries) or even earlier, it

should be emphasized that the eastern section of the

Central Andes offer stimulating perspectives for the

discovery of new deposits and for the re-evaluation

of old mining areas, either in Peru, Bolivia or

western Argentina. For mineral exploration, the

brittle–ductile quartz veins in Ordovician to Car-

boniferous batholiths and the saddle-reefs in the

lower Paleozoic anticlines represent the most prom-

ising targets for high-grade orogenic gold deposits

with subsidiary antimony and tungsten. From an

economic point of view, the relatively high-grade

intrusion-hosted deposits are suited to selective

mining (e.g. Pataz), and perhaps the large-tonnage

turbidite-hosted deposits, even in disseminated form,

could represent targets for bulk mining (e.g.

Amayapampa).

In view of the paucity of the regional and

metallogenic studies in the Paleozoic Bolivian and

Peruvian Andes, we are aware that the aforemen-

tioned models, in particular for the Au–Sb belt of

Fig. 4. Paleogeographic sketch of the Gondwana supercontinent at Middle Cambrian times after Courjault-Rade et al. (1992), with the circum-

Gondwana and peri-Tethys location of the mobile belts that will host major middle to late Paleozoic orogenic gold provinces. The ages of the

gold belts are after Goldfarb et al. (1998, 2001) and Groves et al. (1998). Other prospective areas are highlighted with question marks.


the southern Eastern Andean Cordillera, are inevi-

tably fragmentary and poorly constrained, and

should be considered merely as preliminary working

hypotheses. A better understanding of the origin and

of the geodynamic environment of the Andean

orogenic gold deposits requires far more detailed

and multidisciplinary approaches with geological

and structural mapping, geophysical surveys, metal-

logenic studies as well as efficient dating of the

metamorphic, igneous and hydrothermal events.

Additional support for unraveling the histories of

the Andean deposits may be provided by the

features common to many Paleozoic orogenic gold

belts worldwide.

6. Conclusions

Significant lode-gold resources with subsidiary

antimony and tungsten occur in the eastern Central

Andes and its foreland (6–34jS) either along

brittle–ductile deformation zones in Ordovician to

Carboniferous granites and gneisses, or as saddle-

reefs in lower Paleozoic turbiditic sequences. These

auriferous mineralizations represent a coherent ser-

ies of belts of middle to late Paleozoic orogenic

gold deposits, among which Pataz, Ananea, Yani

and Amayapampa are the best known examples,

which extend from northern Peru to central Argen-

tina along the Eastern Andean Cordillera and fur-

ther south in the Sierras Pampeanas. Two broad

mineralization epochs have been identified, with

Devonian ages in the Sierras Pampeanas Au belt

(26j to 33j30VS), and Carboniferous ages for the

Pataz–Maranon Valley Au belt in northern Peru

(6j50V to 8j50VS). The absolute timing of the

southeastern Peruvian, Bolivian and northwestern

Argentinian turbidite-hosted lodes, which form the

Au–Sb belt of the southern Eastern Andean Cor-

dillera (12j to 26jS), is poorly constrained. Field

relationships suggest some overlap of gold veining

with Carboniferous deformation events. These

Andean belts are the South American segments of

trans-global orogenic gold provinces that were

formed from the Late Ordovician to the Middle

Permian in accretionary or collisional belts that

circumscribed the Gondwana craton and the paleo-

Tethys continental masses.

Acknowledgements

The research on the Pataz gold deposits was

launched in 1996 under the proposal of W. Sologuren,

and benefited from the assistance of the Peruvian

mining company Cıa Minera Poderosa S.A., Lima.

This work was also supported by grants Nos. 20-

47260.96 and 20-54150.98 of the Swiss National

Science Foundation. We are especially grateful to V.

Bouchot and R. Goldfarb for their valuable comments

on an early version of the manuscript. We also thank

V. Maksaev and R. Skirrow for their helpful and

constructive reviews, which led to a substantial

improvement of our manuscript.

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Orogenic Gold Andes