GEOLOGY AND EXPLORATION - library.aimehq.orglibrary.aimehq.org/library/books/Volume 1 - Mining and...structure, and probable time of mineralization. The theories developed to explain

SECTION 11

GEOLOGY AND EXPLORATION

Chapter 3

STRUCTURAL LINEAMENTS AND MINERAL DEPOSITS,

EASTERN UNITED STATES

by Frank G. Snyder

Consulting Geologist, Wheaton, Ill.

INTRQDUCTION

Numerous deposi ts of l a d and zinc su l f ides , of ten accompanied by b a r i t e and f l u o r i t e , occur i n carbonate host rocks throughout cen t r a l and a s t e r n United States . So s imi lar a r e the deposi ts i n broad general cha rac t e r i s t i c s t h a t they long have been c l a s s i f i ed a s Mississippi Valley type. They d i f f e r widely, however, i n de- tails such a s metal r a t i o s , age of host rock, type of ore-bearing s t ruc ture , and probable time of mineralization.

The theor ies developed t o explain the source and t ranspor t of t he metals a r e m y and a r e known t o all. The deposi ts have been termed telethe- on the bs is of t h e i r presumably shallow occurrence and the attempt t o r e l a t e t he metals t o the c l a s s i c hydro- thermal sequence. It i s now recognized that deposi ts of t h i s type can occur a t any depth; the only depth l imi ta t ion is thickness of t he sedimentary section. Ideas on the source of the metals a l s o have changed. A rapidly growing body of evidence suggests t h a t the metals were brought by concentrated brines f r o m nearby sedimentary basins.

The hypothesis preferred today by many geologists postulates that the metals were deposited during the course of nornnl sedimentation i n deposi t ional &sins of miogeosynclinal o r orthogeosynclinal type. A t some time a f t e r deposition of the sediments, t he metals were ca r r i ed out of the kasins by migrating brines; t he brines moved l a t e r a l l y and upward in to s t ruc tu ra l ly high areas ; they entered any reservoir- l ike s t ruc ture , e i t he r primary o r secondary i n origin, t h a t happened t o be avai lable; i n t h i s reservoir , possibly i n a sulfur-r ich environment, the metals were precipi tated as ore minerals.

STRUCTURAL LINEAMENTS, MINERAL DEPOSITS, EASTERN U.S. 77

Considerable uncertainty still e x i s t s as t o the s t a t e in which the metals were transported and how and why they were precipi tated, but progress is being Illad= i n reseerch on these subjects. The g rea t gaps in theory a t present are: (1) the source of heat t o bring the ore so lu t ions t o t h e measured temperatures of mineral fornat ion and (2) t he mechanism t h a t t r i gge r s the migration of t he metal-bearing so lu t ions out of the basins.

To those of u s involved i n exploration, mineralization theory not only should explain the f a c t s of ore occurrence we observe, it a l s o should a i d in defining new t a rge t a r eas of high potential . Present theory can define a r e a s of potent ia l i n t e r e s t only i n t he broadest sense such as t h e r i m of a l a rge basin o r t he flank of a major up l i f t .

Two s e t s of fea tures widespread in cen t r a l and eastern United S ta t e s , when corre la ted with mineral d i s t r i c t s , suggest a source of heat that may have i n i t i a t e d movement of the ore solut ions, brought the br ines t o the required temperatures, and provided the l o c i f o r mineral deposition. The fea tures a r e cryptoexplosion s t ruc tu re s and a l k a l i c igneous rocks. Judicious use of these f ea tu re s combined with knowledge of o re occurrence may point speci- f i c a l l y t o new areas of exploration in t e re s t s .

MINERAL DISTRICTS

The more important lead-zinc occurrences a r e shown on Figure 1. Included a r e the major d i s t r i c t s , minor d i s t r i c t s that have had some production, and a r e a s t h a t contain numerous prospects and scat tered widespread minerslization. Many other minor occurrences a r e known; those shown represent most of t he ones that can be termed s igni f icant concentrations of introduced metals.

The major cha rac t e r i s t i c s of deposi ts of t h i s type a r e summarized i n %ble I. The d i s t r i c t s , where paleogeologic fea tures have not been obscured by l a t e r s t ruc tu ra l events, a r e located on the r i m s of major basins and over o r on the f lanks of Paleozoic s t ruc tu ra l highs ( ~ i ~ . 1) . The pa t te rn and time of a c t i v i t y of the in t r a - cratonic t a s i n s varied considerably during Paleozoic time; t o be exact each d i s t r i c t should be considered i n r e l a t ion t o its struc- t u r a l environment a t the time of mineralization.

Each d i s t r i c t d i f f e r s from others i n d e t a i l s of its geologic s e t t i n g and character of its ore t raps. The Southeast Missouri Lead D i s t r i c t revea ls pronounced f a c i e s changes i n the carbonate host t h a t a r e re la ted t o basement topography (1, p. 329). The Bonneterre F o m t i o n is coarse-grained dolomite, or ig ina l ly lime sand, near t he anc ient shoreline. Basinward, t h i s grades i n t o a dolomite zone containing extensive l a t e r a l and v e r t i c a l f a c i e s

changes, including alp91 reef . S t i l l f a r t h e r outward t h i s dolomite zone grades in to limestone. The dolomitic reef zone, including a variety of l i t ho log ie s associated with and above and below the reef i s the mineralized part of t he formation.

It must be recognized that the carbonate sediments of the South- ea s t Missouri d i s t r i c t a r e those of the shallow shel f environment modified and control led by proximity t o an i r r egu la r ksement surface. Other lead-zinc d i s t r i c t s occur i n similar shallow-water, shelf carbonates with sedimentation i n each case control led by and ref lec t ing the conditions peculiar t o t h a t area.

In most of t he d i s t r i c t s fau l t ing and/or f rac tur ing played a major ro l e i n guiding and control l ing mineralization. A e i n using the Southeast Missouri d i s t r i c t as an example. we f ind the

Fig. 1--Regional s t ruc ture and Pb-Zn d i s t r i c t s . (Hachure-ksin , Line-arch o r u p l i f t , Black-mineral d i s t r i c t , ~ - ~ r o s ~ e c t ) .


TABLE I. Charac ter i s t ics of Mississippi Valley Type Deposits

Ore occurrence in host rock Shallow water marine carbonates On s t ruc tu ra l high Unconformities above, below, o r within host Unconformity o r aqui fer below ore A t o r near limestone/dolomite i n t e r f ace A t any depth

Ground Preparation D i s t r i c t a t o r near major s t ruc tu ra l in tersec t ion Open space increased by di latancy o r dissolut ion

Ore-bearing Structure S t ra t igraphic t r a p s Organic r e e f s and associated s t m c t u r e s Breccias

Subrmrine s l i d e Solution co l l a s e Pseudobreccia fd iasolu t ion) B u l t

Fissures Mineralogical Character

Simple mineralogy Reversals and r epe t i t i ons in paragenetic order Low temperature of formation Concentrated Na, Ca , K br ines i n l i qu id inclusions Mostly open space f i l l i n g i n dolomites, replacement

in limestones

i n t he d i rec t ion of fau l t ing (1, p. 346). Intensive f rac tur ing along and between major breaks provided the plumbing f o r easy movement of ore solut ions (1, p. 347).

Variations on t h i s f r ac tu re control a r e present i n o ther dis- t r i c t s . The productive Picher f i e l d i n t h e Tri-State d i s t r i c t is a t t h e in tersec t ion of two major s t ruc tures , t he M i a m i and Bendelari troughs (2, p. 405); c ross sec t ions of ore bodies in the Cave-In- Rock area of t he Illinois-Kentucky d i s t r i c t show that o r e t r aps were developed along minor f a u l t s (3, P. 381) I stope pa t te rns in the Jefferson City mine in t h e &st Tennessee d i s t r i c t show a palal lel ism of ore bodies t h a t can be a t t r i bu ted only t o f rac ture control (4, p. 991). Addi t ioml examples showing the nra j o r r o l e played by f rac tur ing and f au l t i ng could be c i t ed f o r other d i s t r i c t s .

The locat ion of mineral d i s t r i c t s i n fractured and faul ted zones along the edges of deposi t ional bssins on the flanks o r over structural highs is a prime f ac to r i n defining exploration targets .

CRYFT0EXPIX)SION STRUCTURES

Cryptoexplosiorl s t ruc tures a r e t he roughly c i r cu la r f ea tu re s up t o 20 miles i n diameter that usually exhibi t upl i f ted , intensely brecciated cores, concentric fo ld pat terns, and annular and r ad ia l faul t ing. These fea tures a r e la rge ly confined t o cratonic a reas and a r e sharply discordant with t h e i r structurally-simple geologic set t ings. The s t ruc tures have been interpreted as being formed by forces from within the ear th i n which case they a r e termed cryptovolcanic i n origin or t o e x t r a t e r r e s t r i a l forces i n which case they a r e termed meteorite impact i n or ig in and a r e ca l led as t ro- blemes.

Students of the meteorite impact school base t h e i r interpreta- t i on la rge ly on the presence of s h a t t e r cones and coesi te , a high pressure form of s i l i ca . Both indica te tremendous pressure, but do not i n themselves indica te the source of the pressure. Each s t ruc ture must be interpreted a s a part of i t s t o t a l geologic s e t t i ng , not as an i so la ted event completely unrelated t o i t s environment.

Numerous cryptoexplosion s t ruc tures occur throughout cent ra l United S ta t e s (fig. 2). Many of the s t ruc tures can be seen i n outcrop, although a few a r e known only from drill hole information. The fea tures d i f f e r i n s ize , i n i n t ens i ty of explosive a c t i v i t y , and i n depth of truncation by erosion. The Wells Creek basin with a diameter of approximately eight miles (5) i s one of the l a rges t exposed, but the Manson s t ruc ture which i s covered by g l ac i a l d r i f t is reported t o be 20 miles i n diameter (6). Most of them appear t o range between two and f i v e miles i n diameter. Age of the s t ruc tures ranges from a t l e a s t ear ly Middle Ordovician t o Tertiary.

The Clasford, I l l i n o i s , s t ruc ture is covered by approximately 1200 f e e t of unbroken sediments with the Maquoketa shale r e s t ing d i r ec t ly on brecciated older formations (7). The Weaubleau, M i s - souri , s t ruc ture containing brecciated Mississippian formations was covered by Pennsylvanian sediments and i s now only p a r t i a l l y de-roofed (8). The exposed breccia and complex f au l t s , termed in t e r th rus t s by Beveridge ( 9 ) . represent the surface expression of the Weaubleau event. Some s t ruc tu re s l i k e Crooked Creek, Wells Creek, and Flynn Creek a r e deeply truncated. A sumwry of t he major fea tures of these s t ruc tures is shown i n Table 11.

Included with the cryptoexplosion s t ruc tures , although s t r i c t l y speaking it does not fit the type def in i t ion , i s the Tiptonvil le Dome formed by the New Madrid earthquake of modern time.

The tremendous force that formed these s t ruc tures is indicated by the charac-tter of the breccia blocks found i n them. A t t he


Decaturville s t ruc ture , a block of Precambrian m i t e pegmatite some 50 f e e t i n diameter has been shot upwards through over a thousand f e e t of Upper Cambrian sediments. A t Rose Dome a l a r g e r block of Precambrian grani te i s enclosed in Mississippian formations far above basement. A t Hicks Dome fragments of basement grani te have been ca r r i ed upward i n breccia d ikes through a t least 8000 f e e t of Paleozoic formations. Some of t he s t ruc tures reveal evidence of two o r more stages of brecciation.

Almost a l l of the cryptoexplosion fea tures occur on pre-existing s t ruc tures , usual ly a t in tersec t ions of east-west and northwest - o r northeast-trending faults o r folds. The cryptoexplosion struc- t u r e s where overlying beds have been removed reveal nothing concern- ing post-explosion s t ruc tu ra l history. The Glasford s t ruc ture formed i n ear ly Middle Ordovician shows continued r e l a t i v e u p l i f t throughout the Paleozoic (7) although the I l l i n o i s basin i n which it is located was continuously subsiding during t h a t time, suggest- ing t h a t t he forces t h a t formed the explosion s t ruc ture continued t o exer t a qu ie t , steady, upward pressure f o r a long period a f t e r t he explosive event. Many of t he cryptoexplosive s t ruc tures a r e expressed as snnll gravity lows.

Fig. 2--Cryptoexplosion s t ruc tu re s (see Table I1 f o r name).

MINING AND CONCENTRATING OF AD AND ZINC

TABLE 11. Cryptoexplosion S t r u c t u r e s

Observed Observ. D i s d . S t r u c t u r e Dialp Old. f m . Y o u n ~ f m . Ft. Up Ft.-Down

1. Crooked Creek 4 Up. Camb. L. Ord. 1000 250 2. Deca tu rv i l l e 3' Precamb. S i l . 1200 400 3. Des P l a i n e s 4 L. Ord. Miss. 600 700 4. Flynn Creek 2 M. O r d . 5. Galena (?) 1 M. O r d . 6. Glasford 2e U. Camb. 7. Glover Bluf f 1 U. Camb. 8. Hicks Dome 10 Precamb. 9. Howell 1 M. O r d .

10. Jeptha Knob 2 U. Ord. 11. Kentland 5 L. O r d . 12. Kilmichael 6 13. Manson 20 Precamb. 14. Middlesboro 4 L. Penn. 15. Muldraugh 16. Rose Dome 3 Precamb. 17. Serpent Mound 4 U. O r d . 18. T i p t o n v i l l e 10 (?) 19. V e r s a i l l e s 1 M. Ord. 20. Weaubleau 7 ( ? ) L o r d . 21. Wells Creek 8 L. O r d . 22. Wiley Dome 5 O r d . 23. Douglas Dam L. O r d .

M. Ord.

M. Ord. L. ord. Penn. L. Miss. M. S i l . M. O r d . Eocene L. Cret. Penn.

Penn . La Miss. Recent u. ord. Miss. Miss. Penn . L. O r d .

Space precludes d e t a i l e d d e s c r i p t i o n s o f i n d i v i d u a l s t r u c t u r e s f t h e r e a d e r ' s a t t e n t i o n is d i r e c t e d t o re fe rences 5 through 13.

ALKALIC IGNEOUS ROCKS

Small igneous bodies of post-Precambrian a g e occur a t numerous p laces throughout c e n t r a l and e a s t e r n United S t a t e s ( f ig . 3). They range i n a g e from Late Cambrian t o Eocene (14) and i n d i c a t e t h a t i n t e r m i t t e n t vulcanism occurred throughout t h e region dur ing most o f t h e post-Precambrian e r a (Table 111).

The igneous bodies range i n composition from s y e n i t e t o per i - d o t i t e and inc lude k imber l i t e , lamprophyre, mica p e r i d o t i t e , per i - d o t i t e , and a v a r i e t y of exo t ic s y e n i t i c types. The d i k e s and p ipes f requen t ly have extremely i r r e g u l a r wal ls ; they r e v e a l l i t t l e wallrock a l t e r a t i o n ; and they apparen t ly were emplaced i n a highly f l u i d s t a t e (8). Zartmen, e t a1 (14, P. 849) s t a t e s t h a t " the v o l a t i l e con ten t o f t h e i n t r u s i o n was high and t h a t rmny were a c t u a l l y produced by a two-phase gas-sol id mixture."


Many of the igneous bodies contain brecciated sedimentary fxag- ments. A t Avon, Missouri, th ree types of d ikes were recognized by Kidwell (15). These include pe r ido t i t e s consist ing only of igneous material, kimberlite conb in ing fragments of sedimentary f o r m t i o n s i n a matrix of igneous material, and pipes containing only brecci- a t e d f h q p e n t s of pre-existing rocks i n a matrix of rock flour. Similar types a r e found a t Hicks Dome, I l l i n o i s (16) and E l l i o t t County, Kentucky. The i n t i m t e re la t ionship of t he i p e o u s material and the brecciated older rock suggest t h a t both are phases of a s ingle event.

Fig. 3--Alkalic igneous rocks (See Table I11 f o r name).

TABLE 111. Post-Precambrian Igneous Rocks

Youngest (14) Pro tab le Location Litholoh~y

1. Highland Co. A lb i t e F e l s i t e 2. Rose Dome area Pe r ido t i t e 3. West. Ark. Perid.,Volc.Br. 4. Magnet Cove Alk. Syen. 5. Murf2reesboro Perid. ,Kimber. 6. L i t t l e Rock Alk. Syen. 7. Riley Co. Pe r ido t i t e 8. Manheim Kimberlite 9. I thaca Kimberlite

10. Grand I s l e Iamprophyre 11. Staunton Neph . -Perid. 12. McDonald Co. 13. 111.-Ky. Kimb. ,Mica Per. 14. E l l i o t t Co. Kirnb.,Mica Per. 15. Norris Mica Perid. 16. Avon Kimb.,Mica Per. 17. Beemerville Alk. Syen. 18. Furnace Creek I a p i l l i 19. Dent Blanch I a p i l l i Tuff 20. Bee Fork I a p i l l i 21. Hazel Green Tuff 22. Masontown Kimberlite 23. l ake Co. Mica Perid.

- . Fm. cu t Age, may. Age Dev. 37 Eocene Penn . 90 Low. Cret. Miss. 97 Low. Cret. Low. Cret. Perm. LON. Dev. 118 Mid. Dev. 136 O r d o 126 O r d . 149 Miss. Penn. 267 Penn. 269 Chattan. Up. Camb. 390 up. O r d . 434 Up. Camb. Up. Camb. Up. Camb. Up. Camb. Up. Penn. Up. Camb.

Up. Cret. Up. Cret. Up. Cret. Up. Cret. Up. Cret. Post-Perm. Low. Cret. Up. Jur. Up. Jur. Up. J ~ r o Post-Miss. LOU. Perm. Low. Perm. Po st-Dev. Mid Dev. Up. O r d . Up. Camb. Up. Camb. Up. Camb. Up. Camb. Post-Penn.

explosive gas phase a c t i v i t y may have taken place without i n j ec t i on of a l i qu id magm phase.

Several occurrences of mafic volcanic rocks i n Upper Cambrian formations i n Missouri ind ica te t h a t magmatic mater ial eru t e d a t surface with explosive force during that period (8, 13, 177.

LINEAMENTS

Introductory

Examined individual ly, each cryptoexplosion s t ruc ture , each igneous i n t ru s ive and each mineral d i s t r i c t appears t o be a unique event, anomalous t o i ts geologic se t t ing . The mineral d i s t r i c t s show many s i m i l a r i t i e s and many differences. The cryptoexplosion s t ruc tu re s appear $0 be randomly d i s t r i bu t ed throughout cen t r a l United S ta tes , and studied as i n d i v i d u l , i so la ted f ea tu r e s each appears t o be unrelated t o i ts environment and t o o the r similar structures . The numerous igneous events a l s o shou an apparently random sca t t e r i ng both in place and i n time.

STRUCTURAL LINEAMENTS, MINERAL DEPOSITS, EASTERN U.S.

Considered as expressions of a s ingle s e t of forces and processes deep w i t h i n t he ear th , t he three phenomena, a l k a l i c igneous rocks, cryptoexplosion structures, and mineral d i s t r i c t s appear t o be c lose ly related. They represent re lease along major c r u s t a l breaks in termi t ten t ly throughout geologic time of magma, @gs, and heat f r o m the loner c r u s t o r upper m n t l e . Magma so released formed t h e a l k a l i c igneous bodies. Escaping gases resu l ted i n t he violent upheavals t h a t we recognize as cryptoexplosion structures. H e a t , r i s i n g from the same deep-seated source, raised the g e o t h e m l gradient i n i t i a t i n g migration of metal-carrying br ines from nearby basins i n t o t h e heated zones where the metals were deposited t o f orm mineral d i s t r i c t s .

The observable common bond between the three types of fea tures is t h e i r c lose s p a t i a l re la t ionship along well-defined east-west lineaments.

The 38th Pa ra l l e l Lineament

Features along the 38th Pa ra l l e l Lineament have been described by numerous authors (8, 18). Hey1 (19) r e l a t ed several mineral d i s t r i c t s t o a deep-seated r i g h t l a t e r a l wench fault along t h i s l ine.

The 38th Pa ra l l e l lineament is marked by 26 dist.J.net f ea tu re s (Fig. 4). These include e ight rniheral d i s t r i c t s , ten a reas of igneous a c t i v i t y , and e ight cryptoexplosion structures. The mineral d i s t r i c t s occur i n rocks ranging i n age from Upper Cambrian t o Upper Mississippian: dated igneous events range f r o m Upper Cambrian t o Eocene; t h e youngest rocks involved in the cryptoexplosive fea- t u r e s range from Lower Ordovician a t Crooked Creek t o Pennsylvanian a t Hicks Dome.

Over p a r t of its length, t he lineament i s marked by t h e exposed Pain t Creek-Rough Creek-Cottage Grove-Palmer f a u l t zone. Over the western p a r t of t he zone no east-west surfacd f a u l t is known, but t he alignment of mineral d i s t r i c t s , igneous events, and cryptoexplosion s t ruc tu re s suggest a basement f a u l t t h a t is not expressed i n the Paleozoic cover.

1 The Tennessee Lineament

To my lmowledge no a t t en t ion has been directed i n the l i t e z a t u r e t o t h e alignment of fea tures here tenned the Tennessee Lineament. The zone, l y ing a shor t dis tance north of the 36th Pa ra l l e l , includes ten mineral d i s t r i c t s , th ree igneous events, four explosion fea tures , and the Tiptonvil le dome which uas formed immediately Af t e r t he New Madrid earthquake (Fig. 5). I

The mineral d i s t r i c t s on t h i s lineament a r e well known. O f the

t h r e e igneous events only the Norris, Tennessee, pe r ido t i t e has been described previously (20) 8 The Iake County, Tennessee, igneous occurrence cons i s t s of mica pe r ido t i t e similar t o t h a t a t Avon a t depths of 2400 t o 2800 f e e t i n Upper Cambrian formations seen i n o i l well cut t ings. This locat ion is t h e s i t e of t h e d i s ~ s t r o u s New Madrid earthquake. L i t t l e i s known about t he McDonald County, Missouri, occurrence. It cons i s t s of coarse mica f l a k e s in well cu t t i ngs i n Mississippian fonmt ions i n an area of poor outcrop.

The cryptoexplosion f ea tu r e s include t h e well known Uel l s Creek and Flynn Creek s t ruc tures , t h e l a t t e r within t h e Central Tennessee d i s t r i c t . The Douglas D a m s t ruc ture , previously regarded as a sink hole, conta ins shock-brecciated dolomite ind ica t ive of a cryptoexplosive or ig in (first recognized by J. W. Odell). The Tip tonvi l le Dome, formed as an aftermath of a v io len t earthquake, i n an a r ea of o lder i n t ru s ive a c t i v i t y must be regarded as an event comparable t o t h e formation of Hicks Dome.

The Galena Lineament

The 38th P a r a l l e l and t h e Tennessee Lineaments a r e well documented by numemus events. Each appears t o mark a d e f i n i t e zone of weakness i n t h e ear th ' s crust . Although some of t h e events described here have long been known, it is only within t h e last severa l yefirs that enough f ea tu r e s have been defined t o e s t ab l i sh spec i f ic trends. On t he 38th Pa ra l l e l , t h r ee explosion s t ruc tures , whubleau, Muldraugh, and Versa i l l es , and four i h e o u s events,

\ --.-.--____ I

'7

/

------. _____ I-------

7- -- -- Scok in Miles.

i i.--.T----r- Fig. 4--38th paral le l ' ~ ineament

Mineral imtion (M) 1 ~ n e o u s ( D I Explosion (E) 1. Timberville Staunton, Va. Versa i l l es 2. Central Ky. Highland Co. Va. Jeptha Knob 3. 111.-Ky. E l l i o t t Co., Ky. Nuldraugh 4. S. E. Mo. 111.-Ky. Hicks Dome 5. Indian Creek Avon, Mo. Crooked Creek 6. Viburnum Funace Creek D e c a t w i l l e 7. Centml Mo. Dent Branch W eaubleau 8. West, Kansas Bee Fork Rose Dome 9- Hazel Green

10 . Rose Dome


Furnace Creek, Hazel Green, Dent Branch, and Bee Fork, have been reported since the ear ly 1960's. On t h e Tennessee Lineament, Douglas D a m , Tiptonvil le Dome, t he Iake County in t rus ive , and the apparent i n t rus ive i n McDonald County, are reported here f o r t h e first time as fea tures on a m j o r lineament, Without these recent ly recognized fea tures events on the Tennessee Lineament, other than the mineml d i s t r i c t s , would include only t h e Wells Creek and Flynn Creek s t ruc tu re s and the Norris peridoti te . The va l id i ty of both lineaments is i n la rge p a r t due t o recent work and t o recog- n i t i on of f ea tu re s t h a t define the eones of c r u s t a l weakness.

In addit ion t o indica t ing a probable genetic re la t ionship between the three types of features, the established lineaments suggest what appears t o be a major east-west s t ruc tu ra l trend in cen t r a l and eastern United States . This east-west trend can be used t o recognize and define lineaments t h a t may be l e s s w e l l documented o r may be suggested by only a few events.

A zone i n northern United States , here ca l led the Galena Linea- ment, i s indicated by the alignment of three a reas of mineralization, one igneous event, and two and possibly three explosion s t m c t u r e s

The areas of mineralization a r e Orange County, N. Ye [:5: %kLay Arch ( l s ) , and the Upper Mississippi Valley d i s t r i c t ; the igneous event i s the Beemerville, N. J., syenite (14); the two known cryptoexplosion s t ruc tures a r e Des Pla ines and Manson. A possible t h i r d cryptoexplosion s t ruc tu re ca l led t h e Galena c i r c l e

i I

Stole in Milcc. I

-.- -i i \ 1- \ I

Fig. +-Tennessee Lineament '#

Mineralization (MZ Igneous (D) Explosion (E) 1. Austinvil le Norris Middlesboro 2. Embreeville b k e Co. Douglas Dam 3. Del Rio McDonald Co. Flynn Creek 4. Fla t Gap Wells Creek 5. Mascot-Jeff. City Tiptonvil le 6. Powell ~b 7. Central Tenn. 8. N. E. Ark. 9. NO. Ark.

10. Tri-State

was recently recognized on a e r i a l photos by T. H. Pullen. It con- sists of a nearly perfect topogzaphic c i r c l e about one mile i n diameter located south of Galena, I l l i n o i s r A preliminary gzavity survey reveals a small gravi ty low over t he c i r c l e ,

The seven events do not c l ea r ly es tab l i sh a major lineament, but t he alignment of fea tures suggests t h a t t h i s may be one.

Other Possible Lineaments

Other east-west lineaments a r e suggested by study of maps. One of these, located approximately along the 41st Pa ra l l e l , includes the Friedensvil le d i s t r i c t , the B la i r County, Pa. PbZn veins (22), and the Kentland and Glasford explosion structures. Hey1 (18) lists several other minor metal occurrences on t h i s l ine .

Numerous possible lineaments a r e suggested by the east-west align.ments of other features.

A s t r ik ing f a c t is tha t the well-documented 38th Pa ra l l e l and Tennessee Lineaments, where numerous f ea tu re s a r e exposed i n outcrop, l i e south of t he area of Pleistocene g l a c i a l deposi ts and north of t he area of Cretaceous and Tert iary cover. The scat- te red a reas of explosive o r igneous a c t i v i t y and mineralization north and south of the exposed Paleozoic may suggest major l ineaments of exploration in teres t .

O R I G I N OF LINEAMENTS

During the past decade grea t advances have been made i n under- standing processes within the c rus t and mantle, Mantle currents , mid-ocean r idges mrking rifts in the ear th ' s c rus t , and grea t t ranscurrent faults in ocean b s i n s a r e receiving de ta i led study (23). Dickinson (24) r epor t s t h a t a t a recent conference on global tec tonics most par t ic ipants accepted the concepts of continental d r i f t and sea floor spreading; the major question appears t o be

Fig. 6--Galena Lineament Mineralization (M) Igneous (D) Explosion (E) 1. Orange Co., N. Y. Beemerville Des P h i n e s 2. Findlay Arch Galena Circ le 3. Upper Miss. Valley Man son


t h e extent t o which s t ruc tu ra l f ea tu re s on the continents a r e influenced by events in the ocean basins.

A number of faults with general east-west s t r i k e have been recognized and surveyed i n t h e no-east Pacific. Vacquier and o thers (25) have measured displacement on a hdt zone located approximately along the 39th and 40th Para l le l s . The zone cons i s t s of two major breaks, t he Mendocino and Pioneer faults. Left l a t e r a l displacement is about 850 miles. The authors s t a t e (24, p. 1253) "there is evidence from magnetics that the Mendocino fea ture may extend eastward from the ( ~ a l i f o r n i a ) coast a t l e a s t 100 miles. There i s no d i r e c t evidence of horizontal displacements, but s trong lineaments and changes of magnetic character a r e present."

Zei tz and o thers (26) reviewed magnetic and gravity data and s t a t e t h a t in p a r t s of t h e midcontinent anomalies t rend east-west. The U.S.G.S. Upper Mantle s tud ie s (27) ind ica te t h a t numerous east-west t rends a r e present. Space l imi t a t ions preclude review of t h e data, but it appears l i ke ly t h a t major s t ruc tu ra l e f f e c t s a r e present on the continent as a r e s u l t of the grea t l a t e r a l d is - placements that occurred i n the ocean hsins. L i t t l e i s known about mantle cur rents below the continents and the possibie e f fec t of such currents upon c r u s t a l s t ructure.

So far as presently known, t h e lineaments do not appear t o represent great l a t e r a l movement of c r u s t a l blocks. A lineament appears t o be a zone of discontinuous breaks. The zone m y be expressed i n Paleoaoic formations, l i k e the eastern par t of the 38th P a r a l l e l Lineament, by a %one of interconnected and branching faults: more commonly, lineaments appear t o have no surface fault expression. Rather than a d i s t i n c t f a u l t zone, the lineament appears t o be a zone of neakness reaching t o t h e upper m t l e . In termi t ten t l oca l f a i l u r e along the lineament, as a r e s u l t of s t r e s ses i n i t i a t e d in the ocean f loor , permitted escape of magma, gas, o r heat i n t o the upper crust.

The lineaments a r e not a r e s u l t of d r i f t i n g apa r t of the North American and European continents. The lineaments nere a c t i v e a t l e a s t as ear ly as Upper Cambrian: r i f t i n g and continental d r i f t occurred mostly during t h e Kate Jurass ic and Cretaceous (28).

THE ROLE OF LINEAMENTS I N MINERALIZATION

Studies of recent metal deposi ts i n the Red Sea r i f t valley (29) reveal a history of c i rcu la t ion of metal-bearing brines and t h e deposition of metals i n geotherrrally heated areas. Sea f l o o r spreading i s occurring a t the r a t e of about 1.6 cm/yr. Oceanic lasalt r i s i n g i n t o the r i f t zone is the source of heat. Some volcanic g l a s s has been found i n sea bottom cores.

Temperatures of b r ines i n l o c a l deeps reach as high as 56OC. Sea water c i r cu l a t ed downward through evapori te sediments south of t h e a r ea dissolving s a l t s from t h e evapor i tes and metals from shales. Geothermal gradient was ra i s ed by recen t ly emplaced basa l t s . The decreased dens i ty of t h e heated br ines causes them t o r i s e and they are discharged i n t o t h e bottom of t h e Red Sea. The evidence i nd i ca t e s that t h e br ines and t he metals a r e derived from t h e sediments; t h e rift supplied t h e heat necessary t o s e t up t h e c i rcu la - t i o n system, t o r a i s e t h e temperature of t h e br ines , and t o increase t h e i r d i sso lv ing power.

Several au thors have sug@~isted that t h e geo the rml grad ien t i n con t inen ta l United S t a t e s may have been r a i s ed i n t h e past by in t rus ives , deep-seated o r otherwise. However, i n most midcontinent d i s t r i c t s , geophysical s t ud i e s do no t i nd i ca t e t h e presence o f post-Precambrian i n t ru s ive s l a r g e enough t o have developed t h e necessary geotherrml gradient .

Movement o f magma within t he upper nan t le where temperatures may remain above t he Curie point could provide a source from which hea t could escape that would not be detected by magnetic methods. S t ruc tu r a l responses a long t he rnajor east-west l ineaments could be t h e l o c i f o r t h e escape i n t o t he upper c r u s t of hea t so generated. Z i e t z and o thers (26) s t a t e that hea t flow data ava i l ab l e f o r t he United S t a t e s i nd i ca t e considerable regional var ia t ion by a f a c t o r of as much a s three. The r i s e i n geothermal gradient a long that par t of t he lineament a c t i va t ed would i n i t i a t e by pressure d i f - f e r e n t i a l t h e migration o f b r ines ou t of a nearby sedimentary basin i n t o t h e heated a rea .

If s t r u c t m l responses i n t h e sedimentary cover a l s o o c c w e d t h e e f f e c t s of d i la tancy would g r ea t l y enhance t h e e f f e c t s of geo- t h e m 1 gradient. The presence of f au l t i ng accompanying minerali- za t ion o r of complex brecciat ion h i s to ry i n some d i s t r i c t s asc r ibed so l e ly t o so lu t ion co l lapse suggests that t h i s may have occurred frequent ly .

LINEAIQ3NTS AND EXPLORATION

There i s no d i r e c t connection between cryptovolcanic s t r uc tu r e s , a l k a l i c igneous rocks and mineral d i s t r i c t s except f o r t he occurrence & al l t h r ee along east-west lineaments. Each is an inde- pendent event. A segment o f a lineament apparent ly can be a c t i v e on more than one occasion and could contain a l l t h r ee types of fea tures .

The only r o l e played by t h e i n t ru s ive and explosive events, so far as explorat ion is concerned, is t o def ine t h e posi t ion o f lineaments. The lineaments, together with a s u i t a b l e she l f

STRUCTURAL LINEAMENTS, MINERAL DEPOSITS, EASTERN U.S.

carbonate f a c i e s and a sone o f ground preparat ion provide t h e parameters t o def ine areas of explorat ion i n t e r e s t .

Po t en t i a l lineaments, suggested by two o r t h r ee events, projected t o a r e a s t h a t have t h e favorable she l f environments appear t o represent prime explorat ion ta rge t s . More than a n y o the r f e a t u r e they appear t o def ine t h a t par t of a basin r i m o r s t r u c t u r a l high most favorable f o r base metal deposi ts .

SUMMARY

Major east-west l ineaments inf luencing t h e l o c a l i r a t i o n of lead- z inc d i s t r i c t s i n shallow-water, shelf carbonate host rocks a r e suggested by alignment of mineral occurrences, a l k a l i c i n t ru s ions , and cryptoexplosion s t ruc tures .

The cryptoexplosion s t r u c t u r e s a r e c i r c u h r f e a tu r e s up t o 20. miles i n diameter t h a t exh ib i t annular fo ld ing and f a u l t i n g and in tense ly brecciated cores. The igneous rocks range i n composition from syen i t e t o pe r i do t i t e and i n age from Upper Cambrian t o Eocene. They occur as bosses, pipes, dikes , and d ike swarms and include pebble breccia and k imber l i t e as well as normal c r y s t a l l i z a t i o n textures .

Two well-defined east-west l ineaments are indicated. One, termed t h e 38th P a r a l l e l Lineament, shows an alignment o f e i gh t mineral d i s t r i c t s , t e n igneous events, and e igh t explosion s t r u c t u r e s a long a 1200 mile length. Another termed t h e Tennessee Lineament, shows an alignment of t en mineral d i s t r i c t s , t h r e e igneous events, and f i v e explosion s t r u c t u r e s a long an 800 mile length.

A l e s s well-known lineament i s suggested by t he alignment o f seven f ea tu r e s including t h e Upper Mississ ippi Valley d i s t r i c t . S imi la r even ts suggest o the r poss ib le l ineaments i n areas o f poor outcrop o r of cover by Pleis tocene g l a c i a l depos i t s o r Cretaceous and Te r t i a ry sediments.

The lineaments a r e believed t o be cont inen ta l e f f e c t s of major t ranscur ren t f a u l t s i n t he ocean bssin o r rmntle cu r r en t s beneath t he continent. It is suggested t h a t t he lineaments extend t o t he upper mantle and t h a t mgma, gas, and heat a r e re leased from t h e upper mantle i n t o segments of t h e lineaments.

H e a t r i s i n g from t h e mantle increased t h e geothermal g rad ien t a long lineaments. D i f f e r en t i a l pressure between t he heated zone and ad jacen t sedimentary bas ins i n i t i a t e d movement of metal-bearing so lu t i ons ou t of b s s in s i n t o t h e zone of e levated tempersture.

The lineaments appear t o o f f e r a u s e m t o o l in def in ing

explorat ion ta rge t s . Project ion of alignments of igneous bodies and cryptoexplosion s t r uc tu r e s i n t o areas of su i t ab l e f a c i e s and s t r u c t u r a l c h a r s c t e r i s t i c s i nd i ca t e s t a r g e t areas f o r base metal exploration.

1. Snyder, Frank G., and Gerdemann, Paul E., "Geology of t h e South- east Missouri Lead D i s t r i c t " , Ore Deposits i n t h e United S t a t e s , Ridge, J. D., ed., AIME, New YKork, 1968, pp. 327-358.

2. Brockie, D. C., Hare, E. H., Jr., Dingess, P. R e , "The Geology and Ore Deposits of t h e Tri-State D i s t r i c t of Missouri, Kansas, and Oklahoma," Ore D e ~ o s i t s i n t h e United S ta tes , Ridge, J. D. , ed., AIME, N ~ N York, 1968, pp, 400-430.

3. Grogam, R. M., and Bradbury, J, C., "Fluorite-Zinc-Lead Deposits of t h e Illinois-Kentucky Mining D i s t r i c t , " Ore D e ~ o s i t s i n t h e United S t a t e s , Ridge, J. D., ed., AIME, ~ e w v - 399.

4. Kendell, David L., "Ore Deposits and Sedimentary Features Jefferson Ci ty Mine, Tennessee," Economic Geology, Vol. 55, Aug. 1960, pp. 985-1003.

5. Wilson, C. W., Jr., and S t eams , R. C., "Geology of t h e Wells Creek S t ruc ture , Tennessee," Tennessee Division of Geology, Bull. 68, 1968, pp. 1-236.

6. Hoppin, R. A., and Dryden, J. E., "An Unusual Occurrence of Precambrian Crys ta l l ine Rocks Beneath Glac ia l Drift Near Manson, Iowa," Jour. of Geology, Vol. 66, Nov. 1958, pp. 694-699.

7. Buschbzch, T. C., and Ryan, Robert, "Ordovician Explosion S t ruc tu r e a t Glasford, I l l i n o i s , " Bull. AAPG, Vol. 47, Dec. 1963, pp. 2015-2022.

8. Snyder, Fa G I , and Gerdemann, P. E., "Explosive Igneous Acki- v i t y Along a n Illinois-Missouri-Kansas A x i s , " Amer. Jour. Science, Vol. 263, June 1965, pp. 465-1493.

9. Beveridge, Thomas R., "The Geology of t h e Weaubleau Creek A r e a , " Missouri Geological Survey and Water Resources, Vol. 32, 2nd Ser ies , 1951, pp. 1-111.

10. Bucher, Walter H., "Cryptowlcanic S t ruc tures i n t h e United S ta tes , " I n t . Geol. Congress, 16th Session, 1933, Vol. 2 , 1936, pp. 1-30.


11. Bucher, Walter H e , "Cryptoexplosion Structures Caused From Without o r From Within the Earth? ("~stroblemes" o r "Geoblemes"), Amer. Jour. Science, Vol. 261, Summer 1963, pp. 597-649.

12. Hendriks, Herbert E., "The Geology of t he S tee lv i l l e Quad- rangle Missouri," Missouri Geological Survey and Water Resources, Vol. 36, 2nd Series , 1954, pp. 1-88.

13. Snyder, M n k G I , W i l l i a m s , J. H., e t a l , "Cryptoexploeive St ruc tures I n Missouri," Missouri Geological Survey and Water Resources, R. I. NO. 30, Nova 1965, pp. 1-73.

14. a r t m a n , R. E., Brock, M. R., Heyl, A. V., and Thorns, H. H., K-Ar and Rb-Sr Ages of Some Alkalic In t rus ive Rocks from Central and Eastern United States ," Amer. Jour. Science, Vol. 265, Dec. 1967, pp. 848-870.

15. Kidwell, Albert L., "Post-Devonian Igneous Activi ty i n Southeastern Missouri," Missouri Geological Survey and Water Re- sources, R. I. No. 4, 1947, pp. 1-83.

16. Brown, J. S., Emery, J. A * , and Meyer, P. A * , J r . 9 "Explosion Pipes i n Test Well on Hicks Dome, Hardin County, I l l i n o i s , " Economic Geolom, Vole 49, Dec. 1954, pp. 891-902.

17. Wagner, Richard E., and Kisvarsanyi, Eva B., " I a p i l l i Tuffs and Associated Pyroclast ic Sediments," Missouri Geological Survey and Water Resources, R. I. No. 43, 1969, pp. 1-80.

18. Heyl, Allen V., "Minor Epigenetic, Diagenetic, and Syngenetic Sulfide, F luor i te , and Bar i te Occurrences i n t he Central United States ," Economic Geology, Vol. 63, Sept.-Oct., 1968, pp. 585-594.

19. Heyl, Allen V., "The 38th Pa ra l l e l Lineament and Its Relation- sh ip t o Ore Deposits," Economic Geolof~ll, Vo1. 63, Jan.-Feb. 1968, pa 88.

20. Hall, George M e , and Amick, H. C., "Igneous Rock Areas in t h e Norris Region, Tennessee," Jour. of Geology, Vol. 52, Nov. 1944, pp. 424-430.

21. Neumann, G. L., "Guymard Lead-Zinc Deposit, Orange County, N. Y.," U. S. Bur. Mines, R e I. 4909, Aug. 1952, pp. 1-10.

22. Brown, John S., "Ore Deposits of t h e ort the astern United States,' ' Ore ~ e p o s i t s i n the-united States ," Ridge, J. D., ed., AIME, New York, 1968, pp. 1-19.

23. lkkeuchi, H., Uyeda, S., and Kanamori, He, "Debate About The Earth," Freeman, Cooper, San Francisco, 1967, pp. 1-253.

24. Dickinson, William R., "The New C l o h l Tectonics, " Ceotimes, Vol. 15, April 1 9 0 , pp. 18-22.

25. Vacquier, Victor, Raff, Arthur D., and Warren, Robert E., "Horisontal Displacements in the Floor of the Northeastern Paci f ic Ocean," Bull. Ceol. Soc. Amer., Val. 72, Aug. 1961, pp. 1251-1258.

26. Zeitz , Isadore, King, Elizabeth R., Geddes, Wilburt, and Lidiak. Edward G.. "Crustal Studs of a Continental S t r i ~ from the ~ t l a n t i c Ocean t o r t h e Rocky ~ o u n k i n s , " B u l l . Ceol. SOC; Amer., Vol. 77, Dec. 1966, pp. 1427-1448.

27. U. S Geological Survey, "Transcontinental Geophysical Survey b (35O - 39 N)", Washington, D. C., 1968.

28. Kay, Marshall, "Continental Dr i f t i n North Atlantic Ocean," Worth Atlantic -- Geology and Continental Drift, A.A.P.C., Tulsa, 1969, PP* 965-9738

29. Degans, Egon T., and Ross, h v i d A., eds., "Hot Brines and Recent Heavy Metal Deposits i n the Red Sea," Springer-Verlag, New York, 1969, pp. 1-600.

Documents

GEOLOGY AND EXPLORATION - library.aimehq.orglibrary.aimehq.org/library/books/Volume 1 - Mining and...structure, and probable time of mineralization. The theories developed to explain