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File : Aa-0 .0 .27Aa-i6A.19.13

AMERICAN SMELTING AND REFINING COMPANYTucson Arizona

December 24, 1963

MEMORANDUM FOR J . H . COURTRIGHT :

o' ce

JAN 1 1 `;. .

STRATIGRAPHY - SUMMARYTroy (Precambrian)-Bolsa (Cambrian)Superior District , Arizona

Attached is a summary report on the Troy and Bolsa Quartzites of CentralArizona . Information for this summary was secured in the vicinity of Superior,

• Arizona and personal communications with D . W. Peterson, A. F. Shride, and M . E .Krieger, all of the U .S .G .S .

The Troy Quartzite and the underlying Apache Group has been intruded by thelarge diabase masses in Central Arizona . Age determinations assign a Precambrianage to the diabase . Subsequently all Precambrian units were beveled by the Cam-brian seas as sedimentation again became dominant in Central Arizona .

The break between Precambrian and Cambrian time, and the assignment of for-mational units, has long been a speculated problem in Central and SouthernArizona . Krieger in her paper was the first to separate the Troy (Precambri .an)and Bolsa (Cambrian) Quartzites with the new evidence now mapped and deciphered .Krieger and Shride, with additions by Cooper and Peterson, are scheduled to writea summary paper on the Precambrian-Cambrian problem . Last report indicated littlehad been written although the report was started more than two years ago .

Separation of the Precambrian and Cambrian quartzites and the assigning ofthe large intrusive diabase masses to the Precambrian helps clarify many structuralcomplexities . Among these is the confirmation of Precambrian as well as post-Paleozoic deformation along the same northeast trending fault zone located northof Superior, Arizona, which essentially is the northern limit of Nels Petersonsmineral belt of the Globe-Miami-Superior area .

JAMES D, SELL

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• Troy (Precambrian) - Bolsa (Cambrian) Problem

TABLE OF CONTENTS

1 . Early History of the Troy-Bolsa Quartzite Problem .

2 . Diabase Problem .

3 . Unraveling of the Quartzite Problem by the UIS .G .S .

4 . Field Work and Description of the Troy and Bolsa (?) Quartzites in the SuperiorArea .

5 . References .

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1 . Early History of the Troy-Bolsa Quartzite Problem

• Pioneering stratigraphic studies and geologic mapping by Ransome (5, 6, 7,8, 9) and Darton (1) established the nomenclature of the Precambrian and Paleozoicformations south of the Colorado Plateau in Arizona .

Ransome (5) in his early work in the Globe area placed all units below thefossiliferous Paleozoic limestone into the Apache Group and assigned a Cambrian(?)age to the group . The Apache Group units above the older Precambrian Pinal Schistwere (in ascending order) : Scanlan Conglomerate, Pioneer Shale, Barnes Conglom-erate, and Dripping Spring Quartzite .

In the Bisbee area the formational exposures are clearer and more easily re-solved than at Globe. At Bisbee Ransome (6) found and named the following Paleozoicunits above the Pinal Schist: Bolsa Quartzite, Cambrian (unfossiliferous) ; AbrigoLimestone, Cambrian (fossiliferous) ; Martin Limestone, Devonian ; Escabrosa Limestone,Mississippian ; and Naco Limestone, Pennsylvanian .

- Returning to the Ray-Globe region, Ransome (7, 8, 9) was able to redefine muchof his early work in the Globe area and extend part of the formational names fromthe Bisbee area. Several new units were noted in the Ray area (Ransome 7, 9) andthe redefined sequence above the Pinal Schist was recorded as : Apache Group, Cam-brian(?) ; Martin Limestone, Devonian ; and Tornado Limestone, Carboniferous . TheApache Group, in ascending order, included : Scanlan Conglomerate, Pioneer Shale,Barnes Conglomerate, Dripping Spring Quartzite, Mescal Limestone, vesicular basaltflows, and Troy Quartzite . The Troy Quartzite of Central Arizona and the BolsaQuartzite of the Bisbee area were somewhat similar but direct correlation could notbe established and separate formation names were assigned .

Darton (1) in his work questioned the Cambrian (?) age of the Apache Group whenhe recognized a long time- interval between some of the units within the Troy` uartz-ite . Southeast of Globe Darton noted an upper Cambrian fossiliferous sandstoneoverlying the lower, unfossiliferous , sandstone and quartzite . Further , this fos-siliferous unit of the Troy was found to be unconformably on the Mescal Limestoneand Dripping Spring Quartzite as the unit was traced southeastward from Globe .Darton suggested that the upper Troy units were equivalent to the Bolsa Quartziteof the Bisbee area .

Darton (2), and latefi-Stoyanow (14), removed the Troy from the Apache Groupand dropped the group status to Precambrian while retaining the Troy in the Cam-brian .

Students of Arizona geology have since speculated on the Troy and Bolsa Quartz-ites in regard to nomenclature and stratigraphic relationships .

2 . Diabase Problem

The great mass of diabase found extensively in Central Arizona has also been asubject of much discussion, primarily as to its age and mode of emplacement .

Darton (1) believed the large sills were Precambrian in age with small bodiesbeing post-Pennsylvanian . Ransome (9) favored a late Paleozoic or early Mesozoic

i .

age for all the diabase . Subsequent writers have confirmed one or the other of• the above observations . A brief review and summary were given by Sell (10) on

the age and mode of emplacement of the diabase in the Superior area .

In the study (10) of a few exposures of diabase and quartzite in the east endof the Magma Mine in Superior, the results indicated that the diabase was an intru-sive magma but had not assimilated any of the quartzite in which it was emplaced .Later, at Magma, additional exposures of diabase and quartzite were observed in theunderground workings . In one exposure an unconformity within the quartzite (des-ignated as Cambrian Troy) was noted and the diabase intruded the lower quartzite ofthis sequence . In another exposure a rubble layer of diabase was noted at the con-tact of the massive diabase and the quartzite . As the quartzite was thought to beTroy in each case, the observations help to confuse the issue on the mode of em-placement of the diabase . The knowledge allowed the possibility of (1) two ages ofquartzite (pre- and post-diabase) or (2) two ages of diabase intrusive activity .

• 3. Unraveling of the Quartzite Problem by the U .S .G .S .

During the past several years workers in the U .S .G .S . have been mapping quad-rangles in Central Arizona and interest in the stratigraphic correlations problemshas been renewed .

Shride, working in the asbestos region north of Globe, was primarily interestedin the diabase , Apache Group , and the lower Paleozoic formations . Shride (11) re-newed the question of the relationship between the nonfossiliferous Troy Quartziteof his area and the fossiliferous Cambrian sandstones , also referred to as Troy,which were found in the southern part of the region . He suggested a Precambrianage for the nonfossiliferous units with a separation of them from the fossiliferousCambrian units .

Krieger (3), mapping the Holy Joe Quadrangle south of Globe, found the twounits in contact and established the stratigraphic and age relationship of the Troyand Bolsa Quartzites . Continued work by Shride (12) established similar relation-ships for the quartzites and established the position of the diabase in relationshipto the quartzite . The diabase intrudes the unfossiliferous Troy and in turn isoverlain by the Bolsa . Age determinations by Silver (13), on differentiates of thediabase sills north of Globe, places a Precambrian age on the diabase, Apache Group,and the Troy Quartzite of the region .

In November 1960 twelve geologists of the U .S .G .S, met in Arizona for a fieldsymposium on the stratigraphic problems of the younger Precambrian and Cambrianunits . Most of these geologists were conducting geologic mapping in specific areasof southeastern Arizona . Also included in the group were authorities in paleontol-ogy, stratigraphy, and structural geology . Areas were visited in the little DragoonMountains, Santa Catalina Mountains, Galiuro Mountains, areas near Winkelman,,Superior, Globe, Christmas, and in the Sierra Ancha Mountains .

The group's major conclusions were :

(1) The Troy Quartzite is Precambrian, based on (a) the intrusion of the Troyby diabase, (b) the time interval represented by the erosional cycle forthe complete removal of large areas of the formation, and (c) the deepweathering of the exposed diabase prior to the deposition of the Bolsa,

(2) The Troy is separated from the Apache`y-Group by a distinct disconformityand is therefore not included in the Apache Group .

(3) Younger quartzite (Bolsa) and other sedimentary rocks (Abrigo ) are sep-• arated from the Troy and the diabase by a major unconformity . These

younger rocks in some places contain fossils diagnostic of Cambrian ageand other organic remains -- vertical scolithus tubes , fucoid markings(horizontal burrows), and phosphatic linguloid brachiopods .

When the group visited the Superior area, under the direction of Don Peterson,they suggested that both Precambrian Troy Quartzite and one of the Cambrian forma-tions were probably present . Subsequent mapping by Peterson confirmed this sugges-tion although the nomenclature for the Cambrian formation has yet to be clarified .Diabase was found to intrude the redefined Troy Quartzite, and several good expo-sures were found showing the Cambrian formation overlying weathered diabase . Insome places up to 700 feet of Troy lay below the Cambrian formation ; and in otherplaces deformation and erosion prior to Cambrian deposition has completely removedthe Troy. Further study by Peterson showed subtle but distinct and consistentlithologic differences between the quartzites of the Troy and those of the Cambrianformation .

i Peterson's report on the geology of the Superior quadrangle is being proc-essed by the U .S .G .S . The western half of the quadrangle has been released inpreliminary form as U .S,G .S . map MF-253 (Peterson, 4) . On this sheet the Cambrianrocks have the-symbol for Bolsa, but the explanation lists them as "Cambrian rocks"without a unit name . Although the unit is essentially a quartzite, Shride andKrieger (personal communication, 1962) favor correlating the Cambrian quartzite atSuperior with the Abrigo formation in the Bisbee-Tombstone area . Peterson (person-al communication, 1962) favors the Bolsa nomenclature . The uncertainty of correlat-ing the Cambrian quartzites of the Superior area with formations further southmakes it advisable to use the designation Bolsa(?) for the formation at this time .

A report on the regional problem as expressed by the U .S .G .S . field symposiumis being prepared by Shride and Krieger . A brief summary of the problem has beenpresented by Krieger (3) .

4 . Field Work and Description of the Troy and Bolsa(?) Quartzites in the SuaeriorArea

The field work in the Superior area during October 1961 was primarily directedtoward gaining an insight into differentiating the Troy and Bolsa(?) Quartzites .The work was undertaken with the guidance and helpfulness of Don Peterson of theU .S .G .S . Several sections typical of parts of the Troy and Bolsa(?) were studiedand specimens from the various units were collected .

The Troy has been divided by Peterson (personal communication, 1962) into anupper and lower member in the Superior area based on a very marked visual changein the formation . Shride (personal communication, 1962) has divided the Troy intothree members in the Sierra Ancha region and has established the following nomen-clature in descending order :

quartzite memberChediski memberarkose member

The arkose member is locally missing north of the Salt River and is missingeverywhere south of the Salt River, In the Superior area Shride would place his

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quartzite member equivalent to Peterson's upper member and the Chediski memberequivalent to the lower member . The term "arkose member" would be reserved forthe lowest member found north of the Salt River .

At Superior the lowest member generally has a basal conglomerate . The conglom-erate consists of granules, pebbles, and cobbles of quartzite, quartz, and frag-ments of Final Schist and the Apache Group in a coarse-grained, poorly sorted,arkosic sandstone matrix . Overlying the conglomerate is a highly variable sequenceof sandstone, arkose, quartzite, siltsone, and gritty and conglomeratic beds .Certain beds locally pinch and swell, and many are lenticular . The channeling andirregular bedding are characteristic of Shride's Chediski member of the Troy .Color varies through shades of brown, gray, yellow, purple, and maroon, with purple-black liesegang bands occurring in some beds . The lower member is generally veryfeldspathic (pink feldspar is found only in the lower member) with abundant inter-stitial feldspar and clay spotting on the weathered surface's . Hematite grains andvarious types of pebble bands are found throughout . The weathered surface isgenerally vitreous and the shapes of the blocks and faces are variable, with therock breaking across the quartz grains for the most part . The over-all color char-acteristic of the exposures is grayish .

At Superior, Peterson's upper member of the Troy shows a marked change . It isgenerally finer grained with only occasional pebble and grit beds and is medium- tothick-bedded with distinct bedding planes, and weathering with a blocky aspect . Theupper member is generally better sorted, cleaner, and is a quartz sand quartzitewith less feldspar and clay content than the lower member . Two features are verycharacteristic of the upper Troy at Superior : (1) A "plum" conglomerate layer ofpebbles which are found at the top of a bed rather than at the base of the bed, and(2) pebble zones composed of dead-white quartz pebbles . The dead-white quartzpebbles are not found elsewhere either in the lower Troy or the Bolsa(?) Quartzites .The weathering characteristic shows the over-all grayish coloration of the Troy, butthe angular blockly outline of the outcrop is different from the variable outlineexhibited in the lower member .

Although the Troy may be readily separated into upper and lower members by thevisual change in the formation at Superior, Shride (personal communication, 1962)believes that the actual contact should be placed somewhere in Peterson's upper mem-ber . Shride points out that the "plum" conglomerate (usually more than one andsometimes as many as twenty ) are characteristic of the upper one -third of theChediski member ( i .e., lower member at Superior ) from north of Globe to the MogollonRim . Also, the quartzite member of Shride (upper member at Superior ) has only rarepebble and grit beds and rare feldspar and clay content .

In the Troy the lithology of the formation is laterally consistent . Althoughthe lower member is quite variable in lithology and grain size, the variabilitypersists laterally from one place to another . Likewise, the lithology of the upperTroy is laterally consistent,

The Bolsa(?) Quartzite is not as consistent in its appearance and changes arefound throughout the Superior district . The base of the Bolsa(?) is variable inlithology and thickness and generally depends upon the underlying rock type . Whereit rests on diabase the basal unit is composed of weathered diabase debris inter-mixed with feldspar grains, quartz grains(?), and in a few places it is composedentirely of diabasic material with a distinctive crossbedded structure . Few dis-tinct diabase fragments, however, have been recognized .

A f

The basal unit of the Bolsa(?) Quartzite is generally dirty, poorly sorted,` contains angular fragments, coarse to fine particles, with silts and muds . The

remainder of the Bolsa(?) is essentially a sequence of regularly bedded sand-stones and quartzites . The rock is even-grained with coarse-grained sections con-taining scattered grit or pebble streaks . Over-all the sequence grades upwardinto finer-grained, thinner-bedded quartzites . Banding and crossbedding areabundant and complete, generally sharp, with distinctive color bands of yellow,orange, red, and white occurring widespread laterally and increasing in the upperunits, in the Superior area interstitial feldspar is less in the Bolsa(?) than inthe Troy, and feldspar (clay) spotting on the exposed surface of the rocks is lack-ing for the most part. Fracturing and blocky outlines are not as sharp nor as con-sistent in the Bolsa(?) . The coloration of weathered surfaces is a decided yellow-ish color and the rock tends to break on the sandstone side with free grains ex-posed rather than across the grains .

5 . References

- 1. Darton, N. H., 1925, A Resume of Arizona Geology : Arizona Bur . Mines Bull . 119,_ 298 pp.

2 . Darton, N. H., 1932 , Some Algonkian Strata in Arizona and Adjoining Regions(abst .) : Washington Acad . Sci . Jour ., V . 22, P . 319.

3. Krieger , M. E., 1961, Troy Quartzite (Younger Precambrian) and Bolsa and AbrigoFormations (Cambrian ), Northern Galiuro Mountains , Southeastern Arizona :U .S . Geol . Survey Prof . Paper 424-C, pp . C 160-164

. Arizona:

4. Peterson , D . W., 1962, Preliminary Geologic Map of the Western Part of theSuperior Quadrangle, Pinal County , Arizona : U .S . Geol . Survey MineralInvestigations Field Studies Map MF-253 .

5 . Ransome, F. L ., 1903, Geology of the Globe Copper District, Arizona : U .S . Geol .Survey Prof . Paper 12, 168 pp .

6. Ransome, F . L ., 1904, The Geology and Ore Deposits of the Bisbee Quadrangle,Arizona : U .S . Geol . Survey Prof . Paper 21, 168 pp .

7. Ransome, F . L ., 1915, The Paleozoic Section of the Ray Quadrangle, Arizona :Washington Acad . Sci . Jour . V . 5, pp . 380-388.

8 . Ransome, F . L ., 1916, Some Paleozoic Sections in Arizona and Their Correlation :U .S . Geol . Survey Prof . Paper 98-K, pp . 133-166.

9. Ransome, F . L ., 1919, The Copper Deposits of Ray and Miami, Arizona : U .S . Geol .Survey Prof . Paper 115, 192 pp .

10 . Sell, J . D ., 1960, Diabase at the Magma Mine, Superior, Arizona : Arizona Geol .Soc . Digest III, pp . 93-97.

1i, Shride , A. F., 1958 , Younger Precambrian Geology in Southeastern Arizona (abst .) :Geol . Soc. America Bull ., v. 69 , p . 1744.

12 . Shride, A. F., 1961, Some Aspects of Younger Precambrian Geology in SouthernArizona : Univ. Arizona unpublished doctoral thesis , 234 pp .

' 13 . Silver, L . T. 1960, Age Determinations on Precambrian Diabase Differentiatesin the Sierra Ancha, Gila County , Arizona (abst,) : Geol . Soc. America

i Bull., V . 71, pp . 1973-1974 .

14. Stoyanow, A. A., 1936, Correlation of Arizona Paleozoic Formations : Geol . Soc.America Bull ., V . 47, pp . 459-540 .

JDS/j k

Reprinted from Sout -n ArizonaGuidebook III, Ariz. Geol. S~ o 968 r'

J . H • Cou r t r i gh t

,~ e k, 69

CORRELATION OF SOME POST-LARAMIDE TERTIARYUNITS GLOBE (GILA COUNTY) TO GILA BEND

(MARICOPA COUNTY), ARIZONA

By

James D. SellAmerican Smelting and Refining Company, Tucson, Arizona

GENERAL STATEMENT

Integration of field mapping by various geologistshas resulted in the identification of some correlativeTertiary units along a zone 130 miles in length. Thezone extends from the Globe-Miami area across thealluvial basin at Casa Grande into the Gila Bend area .The rock units are correlated on the basis of rocktype, structural involvement, and sequence, but theyare not necessarily exact time equivalents . This paperdoes not propose that any rock unit completely cover-ed the region from Globe to Gila Bend, nor that similarappearing units in the various areas are necessarilyfrom the same source . The units are post-Laramide(post-early Tertiary) in age .

I wish to thank ASARCO geologists for their writtenand verbal comments and, along with M . E. Cooley,for field checks. American Smelting and RefiningCompany (ASARCO) kindly permitted permission forpublication of the paper .

DIVISIONS

The late Cretaceous-early Tertiary sequence of se-lected localities was reported in a paper by Richardand Courtright (1960). Summaries of the numerousproblems of Late Mesozoic-Tertiary events involvingsequence and correlations are given by Cooley andDavidson (1963), and Heindl (1962) .

The post-Laramide Tertiary units rest on a wide-spread erosion surface termed the San Xavier surface(Heindl, 1962, p. 13). In this paper the following sixdivisions are proposed for this portion of the Tertiarysequence .

VI Younger basalts ) Late (?) Miocene-early Pliocene

V Tuffs and ignimbrites ) Late Eocene (?) toMiddle Miocene (?)

IV Younger conglomerates)III Older volcanics )II Andesitic volcanics )I Older conglomerates )

All divisions are not represented in each area discus-sed; however, the stratigraphic-structural break repre-senting these divisions has been noted and commentedon by various workers in Cenozoic geology . Field rela-tionships of the rock units and their structural com-plexities indicate that a sequence of depositional-readjustment and volcanic activity was continuous forthe entire time span as covered in this paper. Therelation of structure to deposition, volcanism, anderosion is widely covered in the papers by Cooley andDavidson (1963), and Heindl (1962) . Because of thesecomplexities any of the Tertiary units may be in dep-ositional contact with any Laramide or pre-Laramidesequence .

Unit names in this paper (generally in quotes) arethose given in the various reports and thus are of localusage only. Widespread correlation with named unitselsewhere in Arizona is speculative at this time, andwork is continuing in correlating the Tertiary sequenceof the Basin and Range Province in Arizona .

Division DescriptionI. Older conglomerates . The older conglomerates

are generally tuffaceous and contain large quantitiesof locally derived debris but do not contain fragmentsof extrusive volcanic rocks. The gravels range frompebble to boulder size, angular to rounded, unsortedto poorly sorted. In the eastern area (Superior-Globe-Miami), the conglomerates appear to occupy restrictedbasins whereas westward in the Table Top-Sand Tankarea they were deposited in more widespread sheets .A major unconformity separates the older conglom-erates from the overlying units .

II . Andesitic volcanics. The lower flows of theandesitic volcanics may interfinger with the underlyingconglomerates but the change - occurs rapidly fromdominantly sedimentary rock to dominantly volcanicrock. At the base of the andesitic volcanics are beds,often exhibiting waterlain characteristics, of brown tored-brown cinder and ash beds, and locally in the west-ern area a white pumice bed. Overlying the cindersare non-vesicular light to medium grey andesite flowscharacterized by abundant red specks which are prob-ably iddingsite derived from olivine .

70

The characteristic cinder and ash beds have beenmapped from the Superior area to the Gila Bend areaand constitute a very good marker bed even thoughthey are thin and not present in all outcrops of andes-itic volcanics.

III . Older volcanics. A dark gray, to black ves-icular basalt lies disconformably on the underlyingvolcanic rocks, predominantly andesitic, in the westernpart of the report area . Associated with the basalt is acomplex sequence of andesitic, rhyolitic, and latiticflows and vents. In the Superior-Globe-Miami area, theDivision III unit is a complex of trachyte, rhyolite,glassy lavas, and other flows, which, in Arnett Creekis known to overlie the "red speckled" andesite andthe red-brown cinder-ash beds of Division II . A majorunconformity occurs at the top of the complex Divi-sion III.

IV . Younger conglomerates. The younger con-glomerates appear to occupy very restricted basins andare primarily composed of material from the erodingand reworking of the nearby older volcanic-conglom-erate sequence . Especially characteristic is the abun-dant debris derived from the older volcanics of diversetypes. With the conglomerates are abundant tuff-aceous sandstones, and some mudstones .V. Tuffs and ignimbrites. A vast amount of ash

material, ranging in composition from rhyolitic to dac-itic, and of pastel colors, make up the units of thisdivision. The material is characteristically a weldedtuff or ignimbrite which often has a dense black vitro-phyre layer near the base . The structural complexitiesof the ignimbrites are minor compared to the under-lying units (especially the older volcanic rocks) al-though the ignimbrites are cut by faulting . A minorunconformity separates the units from the overlyingyounger basalts .

VI. Younger basalts. Dense, black basalts overliethe ignimbrite forming material . The basalts are foundas isolated "caps" throughout the region, but are alsofound as widespread, though dissected, sheets .

DESCRIPTION OF AREAS

Five areas , from Globe to Gila Bend, and their se-quence of post-Laramide rock units are discussed inthis section . Figure 1 shows the geographical relation-ship of the areas. Figure 2 is the proposed correlationbetween the six divisions previously described .

Globe-Miami

In the Globe-Miami area the older conglomerateunit of Division I is represented by the Whitetail Con-glomerate which may rest on any of the older rocks .The conglomerate is composed of coarse, bouldery

_0Arizona Geological Society - Guidebook III

diabase detritus with subordinate amounts of PinalSchist, Apache Group, and Paleozoic limestones . N .P .Peterson (.1962, p. 37) writes: " . . . . the lower part iswholly unsorted and unstratified. Higher in the sec-tion crude stratification can be recognized, and lensesof poorly sorted gravel occur that undoubtedly repre-sent temporary stream channels . Approximately theupper 50 feet of the formation is well stratified and iscomposed of layers of dark sand and gravel interbed-ded with layers of white tuffaceous sand ."

The andesitic volcanics, Division II, are not repre-sented in the Globe, Miami area and the older volcanicsof the complex Division III rest directly on the White-tail. The correlation of N . P . Peterson's "Earlier Vol-canics" with Division III is based on Blucher's (1958)and D . WW' . Peterson's (1962) work in the Superior area .

The Division III unit is a complex assemblage ofbedded tuffs (some of which are waterlain), felsiticand glassy lavas, and perlitic glass . These volcanics areseparated from the overlying volcanics by an "intervalduring which some erosion of the rocks of the firsteruption occurred" (N. P. Peterson, 1962, p . 37) .

This interval of erosion undoubtedly is the intervalrepresented by Division IV, younger conglomerates,but no remnants of any conglomerate have been re-ported .

The Division V, tuffs and ignimbrites, ("Later Vol-canics" of N . P. Peterson, 1962 ) have a base of whiteto gray crystal-tuff which grades upward into a blackvitrophyre, which in turn is overlain by the massivewelded tuffs or dacite which have a slightly variablelight brownish-gray-orange color .

Superior

The Whitetail Conglomerate (Division I, older con-glomerates) crops out in the Superior quadrangle inseveral places and in Queen Creek within the Thomp-son .Arboretum area of the Picketpost quadrangle . TheWhitetail Conglomerate, as described by D . W. Peter-son (1962) is " . . . . fluvial deposits composed ofangular to subangular fragments derived from all olderrocks, mainly from underlying or nearby rocks . Mostfragments are pebble size, some larger . Matrix iscoarse-grained, poorly sorted arkosic to lithic sand-stone, moderately well cemented ; bedding planes poor-ly defined or absent."

Overlying the Whitetail Conglomerate north of Pick-etpost Mountain is the distinctive brown to red-brownash bed which in turn is overlain by a massive blue-black andesite ("Blue Basalt" of Blucher, 1958) withaltered red crystals - probably iddingsite after olivine .These volcanic units represent Division II, andesiticvolcanics, of this paper . In Arnett Creek the ash bedsrest directly on either Final Schist or Laramide granite,

IN

0 071

SCALE10 0 1 30 40 50 miles

Figure 1 - Location map of south-central Arizona

72

while in the road cuts west of the Arboretum they reston Pinal Schist and poorly preserved conglomerates .

Blucher and Kinnison in 1960 (Personal Communi-cation) recognized a disconformity separating the Divi-sion II red ash and "Blue Basalt" units from the over-lying complex (Division III) of tuff, spheroidal agglom-erate with perlite, and rhyolite of the Arboretum area .Eastward the units are apparently part of the sequencewhich D. W. Peterson (1962) describes as : "Rhyolite :Lava flows composed of rhyolite and perlitic obsidian .Light to medium-gray rhyolite . . . . generally prominentflow laminations, locally contorted . Perlitic obsidiangenerally forms top or bottom of rhyolite flows . . . .Includes minor deposits of tuff, tuff breccia, and flowsof andesite and trachyte ."D. W. Peterson (1966) suggests that the tuffs and

rhyolites on Picketpost Mountain are younger than thedacite; however previously (1962), he maps and des-cribes the thick rhyolite which underlies the dacitenortheast of Picketpost .

A break suggesting an "unrecognized erosion cycle"(Blucher, Personal Communication) separates the com-plex sequence of Division III from the overlying daciteand welded dacite tuff of Division V . As in the Globedistrict, this interval is represented by Division IN' .

The dacite of Division V is described by D . W. Pet-erson (1962) as " . . .ash-flow sheets ; non-welded tuffat the base grades upward to densely welded blackvitrophyre that is overlain by densely welded tuff withcryptocrystalline groundmass . Progressively upwardfrom the vitrophyre the welding gradually decreases,the amount of crystallization in the groundmass in-creases and the color changes from light brown tomoderate red to very light grey ."

Blackwater-San Tan

ASARCO geologists Blucher and Kinnison conduc-ted the bulk of the mapping in this area and the fol-lowing descriptions are from their reports .

The lowest post-Laramide unit found was termedthe "Yellow Peak conglomerate" for its excellent ex-posure on Yellow Peak northeast of Olberg. This Divi-sion 1, older conglomerate, is equivalent in position tothe Whitetail Conglomerate of the Globe-Superior re-gion. The "Yellow Peak" (as reported by Blucher)". . . .is a poorly sorted, poorly indurated, fluvial de-posit . . . . made up principally of pebbles, cobbles, andboulders of Coolidge granite in a silty matrix ." TheCoolidge granite is the report term for the Laramidegranite of the area .

The basal unit of Division II, not everywhere pres-ent, is red-brown cinders and ash beds ("Olberg Beds"of Blucher and Kinnison) which rest directly upon the

0Arizona Geological Society - Guidebook III

"Yellow Peak conglomerate" as well as the Laramidegranite. Overlying the red-brown cinders and ash bedsis Blucher's "Blue Basalt" which is seldom amydaloi-dal or vesicular . The basalt weathers to a soft bluish-gray surface. This sequence of cinders and basalt isdirectly correlated with the Division II sequence at theArboretum, Superior, Arizona .

Units composing the complex group of Division III,older volcanics are not exposed in the areas mappedby Blucher and Kinnison, but they may be present inthe volcanic complex of the Malpais Hills to the northand west .

Overlying the "Blue Basalt" is the "Rock Peak con-glomerate" which is assigned to the younger conglom-erates of Division IV . This unit is composed of " . . . .tuffaceous sandstone, siltstone, and conglomeratewhich weathers to a light tan pock-marked surface"(Blucher, private company report) .

The tuffs and ignimbrites of Division V cap RockPeak and Yellow Peak and are exposed in most of thecliffs west of the peaks . This thick sequence of daciticvolcanic rocks is correlated with the dacites to the eastand consists of tan dacite tuff, welded tuff, or tuffagglomerate with a brown to black vitrophyre nearthe base of the series .

The younger basalts (Division VI) cap many of theisolated buttes in the region . They were named the"Walter Butte basalt" by Blucher for exposures onthe butte .

Table Top-Sand Tank

Throughout this region are numerous exposures ofthe older conglomerate - here termed the "AntelopePeak conglomerate" for its excellent exposure on thatpeak in the Antelope Peak quadrangle west of CasaGrande . The Division I conglomerate rests on Pre-cambrian granite at Antelope Peak, on Apache Grouprocks on Table Top Mountain, on Pinal Schist through-out the area, and on Paleozoic limestones and Lara-mide granite south of Freeman Underpass on the CasaGrande-Gila Bend Freeway . Mapping in this area wasconducted by the author. The "Antelope Peak con-glomerate" has a sandy-silty-tuffaceous matrix, oftenwith waterlaid biotite tuff lenses and contains pebblesand boulders of Laramide and older rocks . Some vol-canic porphyry-type pebbles are present in minoramounts but none resemble the overlying volcanics .Boulders of conglomerate similar to the Glance Con-glomerate (Cretaceous) of the Vekol Mountains arealso present .

Division II, andesitic volcanics unit, is composed oftwo distinct units . The lower member, the "Freemanbeds" (exposed in the roadcuts at Freeman Underpass)

GILA BEND SAND TANK TABLE TOPBLACK WATERSAN TAN ARNETT CREEK SUPERIOR SUPERIOR GLOBE-MIAMI

(L.A . NNndl) ( J.D . Sell ) (J . D. Sell) ( A.G . Bluchera J .E . Kinnsan )

(A.G. Bluchera J.E . Kinnison)

( A . G. Blucher ) (D.W. Peterson) (N . P . Peterson)

HISmilest X22 miles- ~135milss- "'3O maes- ",5 n les- Same Area '1t3 miles-

V Tsv, Volcanic MemberTri, Rhyolite Rnimbrile

t hV

RhyoliteV

Twb, Walker

tuff rop yrcalnstutf ignimbrite VI Basalt

\ \i\ D

Dacite \

IV CongbmeraleTic, Indian

IV Butte(Os), Caliche

IV cementedoc le

\ V black docitic vitrophyre V Massive beds andConglomerate sediments Ion docile lull stratified tuffs

M\ \

III BasalYounger Volcanic$

III Tb , basaltTu ,undifferentiated

III Tb, Basalt

~\ Rock 9I\ IV Peak III

Conglomerate W

Brawn rhyolite \III Sphergdol agglomerate V

S perlite\

Docileand/orweldedDociletuff

To, Dacitevery light grey docile

V moderok red docilelight brown docileblack vitrophyre

> Dociley g black NNropbyre

white b grey cryslal-tuffTon water- lain tuffs

~

non-*,Idld talf

Dacitb welded tuft Tdv , Double BoRes Volcnnicsdocile tuft

Tow, Older Volcanicsdocile tuff "Blue

~ -"Blue \ r° Rhyolite Tr, Rhyolife Compbs of bedded

block vitrophyreII scoria-agqlomerote starta•ogqbmeMe Basalt• Basalt, I11

I .. flows of r liceIII

h ntuffs, le se and

11 red speckled mdesile II red spesMed andesite 11 11

\

Vilrophyre .including tuH~ tuH III _ glassy lovos, and

erlite leBrownish red ash itb,Freeman Beds Olberg beds"red ind and ash Brown to Tuff breccic and flows of

ondesite and trachyteg nw° p

eolian sandstone s c ers red brown µ'ash red bran ash

Tam, Sedimentary Member Toe Antelope "Tw, Whitetail Tw, Whitetail T., Whitetail Tw , Whitetail

I grey boubK conglomerate ,I Peak I Ta, Pebble I Yellow Peak

") Conglomerate . I Conglomerate Conglomerate I Conglomerate

nduroted tanglomerate ; Conglomerate Conglomerate Conglomerate (Arboretum Area-brick red arkosk smdstane Sell)

LARAMIDE AND PRE-LARAMIDE ROCKS

Figure 2 - Proposed correlation of post-Laramide units in central Arizona

0

w

I74

is composed of brown-red cinders and ash with whitepumice. The upper member, "Double Buttes volcan-ics" (named for the exposures in the Table Top quad-rangle), is composed of purple gray andesite contain-ing the characteristic altered red crystals, lava scoria,cinders, agglomerate, and sometimes local units ofdacitic tuff.

In the Sand Tank region, the volcanics of DivisionII are mapped as the Sauceda volcanics of Cretaceousage by Wilson et al (1957). As the volcanics overliethe older conglomerates which contain fragments ofLaramide-type rocks, the volcanics must be youngerthan Cretaceous .

The interfingering of the lower conglomerate typeunit with the first phases of extrusive volcanic actionof the Division lI units is well demonstrated in expo-sures in the region . However, it is not known whetherthe interfingered conglomerates are merely the resultof erosion and reworking of the main conglomerateunits or whether it reflects the continued inflow fromthe conglomerate source areas. The exposures show,however, that the change from dominantly sedimen-tary processes to dominantly volcanic processes issharp and complete .

Overlying the andesitic volcanics are units of Divi-sion III . In the Table Top area, Division Ill is a basaltsequence of dark glassy basalt and dark andesitic ba-salt; whereas, to the west in the Sand Tank area thebasalt is associated with a complex of andesitic, latitic,and basaltic volcanics interbedded with minor tuff-aceous units .

The younger conglomerates of Division IV are poor-ly exposed throughout the region but scattered out-crops of conglomerate containing fragments of all pre-vious volcanic types in the area can be found . Oneexposure is at Indian Butte (Table Top quadrangle)where a tuffaceous, often caliche-cemented, conglom-erate contains numerous fragments of the older vol-canics and basalts. Northwest of the Table Top Moun-tains an outcrop of conglomerate containing all typesof volcanics is found underlying a rhyolite ignimbrite .

Capping many isolated buttes, especially north ofthe Freeman Underpass, is a distinctive pinkish rhyo-lite ignimbrite which generally has a basal tan tuff andblack vitrophyre. The tuff, vitrophyre, and rhyoliteignimbrite are assigned to Division V. An unconform-ity separates Division V units from the underlyingunits, and the upper units have been subjected to onlyminor faulting and tilting.

No dense black basalt of the Division VI type wasfound in the area mapped .

0Arizona Geological Society - Guidebook III

Southeastern Gila Bend Mountains

The work of Heindl and Armstrong (1963 ), follow-ing the previous work of Babcock and others (1948),was a rapid reconnaissance of a small part of the southend of the Gila Bend Mountains . Heindl defined anddescribed the "Sil Murk Formation" in this report and,although additional work is needed to definitelyestablish the correlation, the sequence of units theydescribe in this formation resembles the sequence ofunits in the Tertiary section farther east .

The Division I conglomerates are mapped over muchof the Gila Bend area and were named the "Sedimen-tary Member" of the Sil Murk Formation .

The "Volcanic Member" overlies an angular uncon-formity cut on the conglomerate and is sequence inwhich Heindl lists the following, ascending, types :Eolian tuffaceous sandstone, brownish-red ash, blackvitrophyre, and dacitic welded tuff (all Division II) ; afine-grained black basalt (Division III) ; a conglomeratecontaining both gneissic and volcanic rocks (DivisionIV) ; and a lavender tuff, possibly dacitic (Division V) .

Also found on the northwest side of the area (butnot mentioned by Heindl) is the distinctive pinkrhyolite ignimbrite of Division V, which is underlainby conglomerates having volcanic material and belong-ing to Division IV .

REFERENCES

Babcock, H . M., Kendall, K . K., and Hem, J . D., 1948, Geology andgroundwater resources of the Gila Bend basin, Maricopa County,Arizona : U . S . Geol. Survey, Open-file Report, 27 p .

Blucher, A . G., Jr., 1958, Porphyry copper reconnaissance, Globe-Superior region, Pinal-Gila Counties, Arizona : private ASARCOreport, 12 p .

Cooley, M . E., and Davidson, E . S ., 1963, The Mogollon Highlands -their influence on Mesozoic and Cenozoic erosion and sedimentation :Ariz . Geol. Soc . Digest, v . VI, p . 7-35 .

Heindl, L . A., 1962, Cenozoic geology of Arizona - A 1960 resume :Ariz . Geol. Soc . Digest, v . V, p . 9-24 .

Heindl, L . A., and Armstrong, C . A ., 1963, Geology and ground-waterconditions in the Gila Bend Indian Reservation, Maricopa County,Arizona : U . S . Geol. Survey Water-Supply Paper 1647-A, 48 p .

Peterson, D . W., 1962, Preliminary geologic map of the western part ofthe Superior Quadrangle, Pinal County, Arizona : U . S . Geol . SurveyMineral Investigation Field Study Map, MF-253, 1 sheet .

Peterson, D . W., 1966, The geology of Picketpost Mountain, NortheastPinal County, Arizona : Ariz . Geol . Soc . Digest, v . VIll, p . 159-176 .

Peterson, N . P., 1962, Geology and ore deposits of the Globe-Miamidistrict, Arizona : U . S . Geol . Survey Prof. Paper 342, 151 p.

Richard, K ., and Courtright, J . H., 1960, Some Cretaceous-Tertiaryrelationships in southeastern Arizona and New Mexico : Ariz . Geol .Soc . Digest, v . III, p . 1-7 .

Wilson, E . D., Moore, R . T ., and Peirce, H . W., 1957, Geologic map ofRlaricopa County, Arizona : Arizona Bur . of Mines, 1 sheet .

GEOLOGY OF THE BISBEE AREA

Abstract

The geologic formations outcropping in the Mule Mountains in the Bisbee

area consist of the Precambrian Pinal schist basement overlain by 1,200 feet of

Cambrian Bolsa quartzite and Abrigo limestone, 300 feet to 375 feet of Devonian

Martin limestone, 600 feet to 800 feet of Mississippian Escabrosa limestone, and

3,000 feet of Pennsylvanian-Permian Naco group . During late Triassic or early

Jurassic time, the Juniper Flat granite with associated dikes and the Sacramento

Stock were intruded into these formations, accompanied by complex faulting and

b recciation . Peneplanation north of the Dividend fault was followed by the

deposition of 5,000 feet of the lower Cretaceous Bisbee group . Post-Cretaceous

tilting, faulting and erosion gave rise to the present surface .

4

STRUCTURAL CONTROL OF THE SULFIDE REPLACEMENT DEPOSITS AT BISBEE

Abstract

Orebodies around and adjacent to the Sacramento stock south of the Divi-

dend fault were probably of a pyrometasomatic origin . Their configuration was

influenced largely by the bedding of the limestone host and to some extent by

fracturing . Orebodies lying away from the stock tend to occur in groups or

clusters . The placement of these clusters was influenced largely by steeply-

dipping north-south trending fracture zones which occur between branches of north-

east-southwest trending faults . A prerequisite of the host rock was its ability

to fracture under stress . This prerequisite is met in the thinly-bedded Abrigo

formation, the Parting quartzite overlying the Abrigo, the impure and brittle

Martin limestone, and the chert zones in the lower portion of the Escabrosa lime-

stone . Post-Cretaceous movements along many of these northeast-southwest faults

have displaced the ore-bearing fracture zones along with the Cretaceous sediments,

and further displaced the Paleozoic formations .

e

k

UNDERGROUND GRAVITY SURVEYS AT BISBEE, ARIZONABY ROBERT N . SCHNEFFE

Abstract

Twelve thousand gravity stations have been occupied in 160 miles of

crosscut underground at Bisbee . All of these values are referenced to a base

network, permitting direct comparison of the data . Latitude, free air, Bouguer,

terrain, and regional corrections are made to the raw data . The resulting residual

gravity data presented in the form of contour maps .

The density of the country rock is remarkably uniform and averages

2 .70 g/cc . A density contrast of 1 .00 g/cc between the massive sulfide minerali-

zation and the country rock is generally assumed in making theoretical calcula-

tions .

Limited station distribution precludes the use of mathematical inter-

pretational aids . Non-sulfide disturbing influences are solution caverns, mine

workings, epidote skarn, dolomitic limestone, gossan, and some copper oxide

m ineralization .

Five examples of gravity anomalies in various portions of the mine are

shown . These illustrate a number of the problems encountered in the interpreta-

tion of the results, as well as the size and magnitude of the anomalies to be

expected . One example of a vertical section showing the relation of the apparent

density to the gravity contours is given .

Eighty percent of the recommended holes that have been drilled have cut

sufficient sulfide mineralization to account for the anomaly they were investi-

gating . The gravity data is also used in planning exploration crosscuts .

~el

P' ..~

Q X , .oa e, Nevada .

No # 1 Shaft at och- tlet4 Shaft over summit - about I mile apart .

` °e body s~ . . ~ lime bad in o shale near base * Prospect Mt. rums b-

low. 0.M, bed 30 ' thick - mineralized portions 3t-51 c -- 2 to 3 h ar on O '

Ore Average grade, Au. , ~ Ago 6 O Z& 6 Lead, I ., 17-19 F - ph de

Or o* e a ton follows B, 11j, 'i u s - N .L faults - drop ' ' boo a as much

as 21-f-300.1* Numerous Porghm-, dikeso

BRISTOL SILVER Bristol age of P ocPaul e tl , geologist, - 3. N. eh e Mgr.

GEOLOGY

Eleven at ocher r 1200 • Min habe wore t .? W on 5 e . . l ne

Shaft . Ore ocourv in fissure fillings and replacements along B-11 8 dlppi4 normal

+ Taper formations are t ,gbIn , peak limestone and dolomite - llwe B rowan

dolomite, Muav & hish shale? r i nearly a.11 secondary r - Iron a. 3 & tee

and sulphates a oxides - : 0 , $04 - Z 0 - T pioal assay - 2 , 4g# 15 Fbo 5

Zat Au . *03 oz. Large v ' containing soft ore occur - platy oho .ti' `beds act as

dams rich ore above . Leads are iron oxide stringers l oVayrio dikes lower

levels - Water table a 1720 - r a doe s supply - r U lay rd

plunger pump . Mine prices 6 tons per day. o contain high grade di&,Ite and

W.Powebaterp Chief Geologist

LO IBYFo .tons Ore , orp - altered mon rite - intruded into aIeo t , s i-

in sass and fractures- also hlo o .te mica and molt' de ,, a . Later ' t par-

°y, - less altered seldom carries ore values - Tertiary h of - ;q bade

r ie fragments o high grade copper -indicating possibility of ore below .

Erosion just- to - v, ' .pii ore small amounts o eon have been

mined (c or e)

Rough rain, district - op erp , o dp silver$ lead,, zinc, X449 'O a in r-

a ination in R-- break : - data es. Foot Wail reverse fault ontr*: n factor

in ore deposition * ore only * mcv n pie-»poe by to past-t yoli e .

s~ Both Por. are sills.

f :.

n,

2

RUTH MINE - NEVADA CONSOLIDATED, Paul Hat, Sup' t .

C"

Gradual gradation from o pre- arpb ry - do o recognize different ,-

. ivea * bottom of high grade ( aleoo t ore ohuts onta.; ° cuoi e - d round-

ed nodules - aoa - called Iteannon balls"' .

r : MNDSINE- 0i . ofTaah -»X.Co erkinap S'

r nodiorit intruding shale and quartzite* Lower pit - c rb aceoi* a .e and

quartzite and granite are a r1. s - latter s ooft altered . Average value $6.00

Au - some rad to . Gold s , :r e fine - does o pan* Anderson - a +a h . *

made i- section of .7 ore » showed no free gold at 10,000 fit Extraction n 80-85% .

3 0T

Early silver p * steep-dipping ,4 t emu ;yes Wna d shale - veins

p °a el to b+ + 1 most case -worked to 5001 - majority of o values .1a

COPPER 0,0103 : E - of Battle an.

L

Bri pipe in quartzite conglomerate out numerous fissures •- latter were

p early days for gold sad copper - soft oxidized ore. Mine developed to 5001 -

primary aleopyrite td pyrite i s - 500#000 tan blocked out - Cup .1 Au .,

gold associated with cha . o . ouzo .t plug ridge a1bove, mine* Diorite

and porphyry dikes in ore body . Solo pyrrh ti #

INDEPENDENCE 'MINE - Wilson coal - west of Copper Ga y ,near re ac ,

Steep-dippin fraot Zee -» average width 5' - irregular odies o -oft oxidized

gold silver ore - aouutry rook - shale ., uar i e and ilild d shale . SJAart down

200* - have shipped of o - average x .01 . Silver-sold ration about, to 1-

Values erratic - ore does o pan "r gold - ao to s much s 1 $ ..- some

Bismuth - small pockets of primary r eno ^r .yes occur. Apparently post mineral

fracturing and faulting has allowed free circulation of surface waters creating open

spaces + r eawes - partly filled with extremely soft residual ore ached removal

o valueless material .

TURQUOISE MINE -» located in Copper as 7 . from Battle Mountain

f

arro seams a . frame zone - vertical altitude vertical - w rook leached --

'light grey - altered quartzite or partially metamorphosed sandstone subsequently alter-

ed b solutions - Ore s hand sorted and ecbbe - shipped gem cutters ire X00

fees - owners - Mineralized zone 151-201 wi e# grades into hard quartzite,-au each

side - Material o ' good quality - bard, dark blue - worth about 600 per b - last

year mine produced three quarters f the U'1 . supply - deposit appears to worked out .

/' . Now With S . Vanadium in Uolorado*

G

Flat lying Weds 3' , is n alluvium at base of m, tai n east of o conch

Ore is composed of .i a so material - mainly tra v erb1ae, clay and iron Oxide - In

places beds of manganese oxide, acme . . , yr lu . occur. Apparently a hot

springs deposition shallow lake W03 in solid of tiou Beds 3t to Of thid.k will be

mined room and pillar - overburden is but few feet wick but batting stands, ell . 30'

bed will be stripped and mined power shovel . Ore soft. i . present development

drifts blasting holes driven with :per and bull prick, Prospecting l chumn rill

y NOTES ; E10 G,4S.A. T `"Tungsten bearing enese Deposits at of ,, evad& R, by Paul `, lamb

Blanket-like deposit of au ifero s and Ohio ; .a lies on ca tilted

Triassic sediments . Overlain ea oec um a: - Beneath are veins of imi zi

era i ation - may b source of ores - R

Ore .iffier .. are colloidal . origin - to at c acid adsorbed

into siom l and limonite while both were gels . Ore -minerals and tafa 4f hot spring

o i l eralizatio started with ert ica ion - .cif ca o - followed by

precipitation of wo , Mai a and u .

1 all of of a

7

Fracture one 1Or-60' ride quartzite . average 15 .00 u d Is - ' flue are

irregular - assay a $ part .

4

EST OAT MINE N of n - sco Smite U.C .

Fissure vein : eta nor bos e si - r i s and hy) i t * Triassic

tu age? Diorite stock near deposit - dikes occur ~» reminerr: - pies voin cuts dior-

ite ttie difference erali ation noted. 3 I- IS 65 degrees . *o stages

of er isation - earlier wife quartz - contains As and `e -ala .d s -» little tu

or 14, Later dark € uartz fills br aeiat d spaces - coma &rs o yr ..te (redoa s--

rite, galena and sine blonde as latest mineral . o e specimens show a la -

b solution o earlier quartz, numerous strike slips displace r tow feet -

.311.s are discontinuous - apparently caused b settling of morn= fault blocks .

MOUNT B Q ; / MINEMike Gould,* PresidentWilliam 'e I t .

UOMILY

Located 50 mi . south ,nn a - Cinnabar occurs m in a "print" t seams

in i u rtzit e - apparently ?ffaceous clay acted as barriers

solution' - deposit may have originated nearby hot springs - lava show Intense

leaohi g due 'to hy oth rme. alteration - characteristic of area contain mercury deppa-

its the district Z o v ..oc ,

NEVADA KASSACHU-SVIT5, W* Ott F. 3 er, Manager .

LmogLocated mi. W of , it ill en age . Con to t met" orp a type deposit

thin beds limestone (3' to 1 :S a sic halo have been replaced by tom , garnet,.

epi ; t , pyrite eaUte Beds str. roa I'1y N-5 and 41) aao o to in-

trades e eu a ° , m ° mor loo .ng shale o tsi . : ' . glue beds terminate

to N a, a t

AKG OPRETY - Located a srt okel a y# 2 mi.S of *ol u - Pat Divines offer.

0, Q,9

Ore occurs in lens 30W 'hick yeti , hundred feet in diameter - near top o spur

u west side of valley. Deposit contains - lover grade material on er.30%,Mn margins- era . i aeou rook associated * jasper and c ° s - tow, veins,

quartz. Ore mineral is sil clan - small amounts of man i . and r l ± . e noted .

Deposit lie on schistose igneous rook p ssibly ru t - May have exig1jute . s

replacement of sedimentary beds . 200,000 ton ; ore blocked out,, 20,000 tons ship-

pod to date . Mining open cut - hand mucked - a erred to minus 3m - jaw sh x -

trucking to olco da $1 .25 - freight Provos, Utah, $3 .25 a 0 per unit - ,umbia

Steel PAYS $9,00 per ton . At present 5 care being loaded for U. S . Government at

Boulder. c content-50..55%.

5

T PLANT - Fred Wise, General , aga

3 .. . r , K V11 8ta eut

eral zat on occurs n said to b .n: re fault zone - tr. -$ dip

40 «- extend several :Mlles . o c, sediments shale .d limestone tntrw3eId by .

Utter e ore where vein cuts dikes or tongues . Or soot v ray from 500 to 2000 ft .

in g - average id ft.,- prospected by incline shaft and drift to $00 level -

HWi black clay gouge - a y a wall - foot wall or i is ou - bre iate

,shale d mes 4e . Oxidized *one down 400' on dip In main pit - '' ,pin: hard

Sam, . a0 broods s over oxide ore - a assays « or .04 - ore I comparatively soft

b+ Bath . Gold s extremely fine M - does not pan - o, c . rations of pyrites 4 not show

higher values -» Average assay $7 .00 . Later r a and orpiment have been introduced -

fault shows movement b equ to all n : ere lira ion flut characterized b series o

ging cted as dam for ore . tons . Contact e . ,lo -asprings . clay gouge h&4g

a t n.te ,r tr lite occur on foot al - no values,, Vein apparontly splits to

north - eroded down to sulphide tone . Small amounts cinnabar i dog sooth mar

sulp d zone - crosscut' on main baulage, drift .

Sulphide ore is roasted drive off sulphur and rend oat . g ) from, gold

particles - 90 extra ti n on oxide less en sulphide ore .

,z n D MINE . . Ross ra ar, S'*GEOLOGY

Open out 100' deep -» all nearly vertical - ins r ,i at occurs in fractured

limestone - assay wall i l: estq e on East - shale contact o West . Ore shows some

iron oxide - n erous calcite stringers * bottomed b flat-dip fault - -04 cut of

Cross-section of deposit

Grade is higher just above fault - some local faulting in ore body . later t 1

otr* rat-loll-'. :?ION SITE 00. .a.

:,mo t emi e deposit e t p *e * albiti c or a .bitised trashy e . A flow

rook in of to limestone, r .kale. Rook Is light colored + htoto * Formation

strikes N--$ dips steeply - ortisrite occurs lenses 21 .*. 1 tbilk platy

schist - Intercalated sediments or zone of shearing - cost of produatAou $20#00 per

ton - ore is sorted and a€ .c b e . An l i and coed are found + yon East .

t

Y' - Pacific Portend cement o

bedded past * "art&s io sediments - 0 pure .

bot - n 5302 form 1,000080 16 cu, ft* in place per a:

SIXT T ONE MINt - e hs r, O ifa .)ilk B e t per Wn tk $ ? nnBill 010r, 0001agiat

Anhydrite at

degree reverse S ult in e Y izL and. r t r formation - chlorite tale id

€ o e i - later tit . out vein . t stage - pjrits d rseaop TitS

on . with and slightly earlier both vall and vein -- replacementt aad stringers

a bona- - repi o t o tU rook rite, a c i e$ , °i c t and

0100e* Last state - Calcite, m ca tt ,Writ oatin and ta . Earlier

quarts milk .e ho- ° e tats. - later quart; War op e earlier,

,;ways sso d ted with rs a Sri - never less than $10O per A.

. acr aof - quartz, pyrite, araenbpy i,t ly Intensity r °a 2 lenal

gold lower Intensity o pha o and to adr te . Ore shoo on 155 - ° Ions

1 dip - , 1 width -» produced 500,000 one p1 ft . drift - 30U,000 200

gold, $140000,000 total pro u - Ira e mill ore $4,50 - 135% redovo # brought out

by specimen boas

BROWNS VALLEY " EMPIRE MPAKYn r ire t Manager

Flat dipping aura in m ete B ab e, a ro, K r - vein r .bsa right

angle turn r ine foraaUo : bond - due no doubt to relatively 1a ate € e of

e tin- Vein is , he - no quartz or , ,ea In e pent . May have acted .s a

dam to solutions a Values are higher where vein goes into serpentine. oa ral f ,

Ing in plane ot vein - causes 00gular thickness of quartz - Later Zornal 901009

e di , a t o 10 o iSf . Earlier faulting r ' « i inera .. - galena

usually associate with gold values - also pyrite - and a & l e ; t - some ru , s

P via shaft on N-8 east dipping brad - eb o 6h aft - 1 degree average

41pf on sw vain .

a~

1

LAVA, OAP MINE

Ot S i±' t ar„ a e

are reverse fault fissure In Metamorphosed ca ona o s srjale l : a ii to

Sate. Average dip 51 ree * width of v& : average , - feet, ' o, .

eff ted by 9r, :Atruajo has not bo ffi .i ' ,y- : r e to 'or ox j' at s

+ afro tact . ., ,: . rc &l& is grey to buck* dose b o °re - defy

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large striations or ourvas In veJA - rake to north - where vein splits ourlobaeat

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1,10 to I.

AMERICAN SMELTING AMD REFINING COMPANYTucson Arizona

February 18, 1963

FILE MEMORANDUM

PORPHYRY COPPER DEPOSITS - AR,ZCNA & NEW MEXICO

A general review of porphyry copper exploration in the Southwest wascontained in my memorandum of October 4, 1950 . Since that time considerableexploratory work has been carried out by various companies, and several newmines have been put into production . The purpose here is to bring the pictureup to date and to re-examine the gambling odds involved in porphyry copper.exploration .

. In the following tabulation porphyry copper occurrences are divided into5 different categories : (1) Productive Deposits, (2) Marginal Deposits(undeveloped), (3) Deposits Currently Under Exploration, (1) Prospects whichhave been Tested and Proven Sub-Marginal, and (5) Untested Prospects .

Productive DeGosits

Over 100 Million Tons*MorenciSanta RitaSan ManuelMiami-inspirationRayAj oCananea (Sonora, Mex.)BisbeeMission-Pima

* Production plus potential

Under 100 Million Tons*BagdadCopper CitiesSilver BellEsp'eranzaChristmasMineral Park(under development)Castle Dome(mined cut)

2) Marginal Deposits (Undeveloped)

Tyrone . . . . . . . . . . . . . Reportedly plus 400 million tons C@ .70% Cu,chiefly chalcocite . Owned by Phelps Dodge .

Lone Star . . . . . . . . .., Reportedly 800 million tons P .55% Cu, mixedsulphides and oxides . Kennecott . -

San Juan . . . . . ., . . ., "Large ore body too deep for open pit mining ."Owned by Phelps Dodge .

Helvetia . . . . . . . . . . 14 million tons .80% Cu . Mixed sulphides andoxides . Controlled by Banner .

-2-File l Memo February 18, 1963

3) Deposits Currently under Exploration

Sacatcn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AsarcoMcGee (NW of Esperanza) . . . . . . . . . . . . . . . Bear CreekSaginaw Hill (So . Tucson Mtns .) . . . . . . . AnacondaRed Mt . (Patagonia) . . . . . . . . . . . . . . . . . . . Kerr-McGeeTwin Buttes . . . . . . . . . . . . . . . . . . . . . . . . . . BannerFour Metals . . . . . . . . . . . . . . . . . . . . . . . . . . Noranda'Johnson Camp . . . . . . . . . . . . . . . . . . . . . . . . . . CyprusChilito . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bear Creek

Sub-Marginal DepositsProven either too small or too 1

Kelvin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Copper Creek . . . . . . . . . . . . . . . . . . . . . . . . .Sunnyside . . . . . . . . . . . . . . . . . . . . . . . . . . . .Turquoise . . . . . . . . . . . . . . . . . . . . . . . . .Red-Hills (Texas) . . . . . . . . . . . . . . . . . . . . .Postcn Butte . . . . . . . . . . . . . . . . . . . . . . . . .Lake Shore . . . . . . . . . . . . . . . . . . . . . . . . . . . .Pioneer Group . . . . . . . . . . . . . . . . . . . . . . . .Blackwater . . . . . . . . . . . . . . . . . . . . . . . . . . .Cerrillos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Hiltscher . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .Steeple Rock . . . . . . . . . . . . . . . . . . . . . . . . .Madera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Cactus . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .Three R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Copper Basin . . . . . . . . . . . . . . . . . . . . . . . . .

cw grade

Drilled ByCon CopperminesBear Creek & othersASARCOASARCO, Bear CreekASARCO., Bear Creek(?)ASARCOUSBM, Shattuck-Denn & Trans ArizonaDuval Sulphur & othersMagma CopperBear CreekBear CreekBear CreekMiami CopperMiami CopperCon Coppermines (property recently

acquired by Anaconda)Phelps Dodge

5} Porphyry Copper Prospects - Untest ed

Rock House (No . of Superior) Outcrops indicate minor chalcocite enrich-ment below, but zone too small in size .

Border Pipe (So . of Patagonia) Mineralized breccia pipe + 500' in diameter .` Outcrops indicate original disseminated

pyrite with minor enrichment. Deposit toosmall to warrant drilling .

Tyndall District (So . Santa Rita Zone of strong quartz-sericite-pyriteMts .) alteration several square miles in extent .

General character of leached outcrops, plusoccasional exposure of sulphides in oldadits, indicate little more than traces ofeither primary or secondary copper .

r

File Memo

5) Con' t

Tombstone

l

Organ District (Organ Mts .,NM)

-3-February 18, 1903

Zone of alteration one mile or more indiameter lies southwest of this old silvermining district . Outcrops do not appeartoo prcmising, but tctal extent of zonehas not been determined . Further recon-naissa,nce planned .

Zone of alteration '-z mile wide extendsabout one mile northwesterly where itpasses beneath valley alluvium . Mineral-ization in-exposed portion of zone notsufficiently attractive to warrant explora-tion . Possibilities under cover highlyspeculative . A possible application ofgeophysics was considered at one time ;however, the area is now partly within theWhite Sands Testing Range .

The Productive Deposits listed above (see attached map for location) range insize from 18 million tons (Castle Dome) to a plus one billion tons (Mcrenci), iffuture potential is added to past production . With the exception of Castle Dome,which is mined out, nearly all of the mines listed here have a future,life of atleast 10 years, and at least 50% of them a future life of over 20 years .

Tyrone is included in the group of marginal deposits ; however, under differentownership this deposit would likely be in production . Phelps Dcdge spent severalyears in drilling and evaluating and then placed it on the shelf --- presumablybecause they possess ample resources of lower cost copper elsewhere . Tyrone, with'a relatively large tonnage and a grade of .70% copper, would be at least equallyprofitable, if not more so, than either of Duval Sulphur's two deposits, Esperanzaand'Mineral Park .

Among the Deposits Currently under Exploration, Saginaw Hill and the FourMetals are noteworthy simply because both are relatively small deposits which haveundergone repeated unsuccessful exploration attempts by various companies in thepast . Anaconda is now drilling a 3000' hole cn Saginaw hill and Norenda is pre-paring to drill the Four Metals .

Reportedly Bear Creek ("McGee" Prospect) has been finding .4 to .5% primarycopper in diorite and andesite in ground adjacent to the Experanza .

Red Pit ., Patagonia, lies within a large alteration zone which includes theSunnyside breccia pipe (drilled by Asarco in 1950) . Kerr-McGee recently completeddriving an incline on the east side, encountering low grade (+ .05% Cu) primarymineralization . Reportedly, they plan drilling higher on the mountain .

Chilito produced 91,000 tons of 1 .4% Cu . This ore,'which consisted of dis-seminated copper in quartzite, was shipped to Hayden as siliceous flux . Kennecottacquired the property last year .,

Banner recently drilled several holes in a gravel covered area southeast of

File Memo-4-

February 18, 1963

Twin Buttes . This is the area generally considered to be the probable locationof the "roots" of the Mission-Pima zone of mineralizatiion . According to a localcontractor, Banner recently cancelled plans for an additional 90,000 feet ofdiamond drilling at Twin Buttes . The area may still hold exploration possibilities .

Most of the copper ore mined at Johnson Camp came from more or less massivesulphide lenses in the Cambrian Abrigo formation . Disseminated copper occurs,however, in the Cambrian quartzite and in the lowermost part of the overlyinglimy shale of the Ab'rigo . During the past few years, 150,000 tons or more ofoxidized copper-bearing rock has been mined open pit and shipped to the Douglas,El Paso and Hayden smelters for siliceous flux ; and recently, Cyprus completed aseries of drill holes in this disseminated copper horizon, reportedly indicatinga zone 150' thick and 2000' long of .75% Cu . `No intrusive rocks of the porphyry

~_ copper type have been found in -the-area ; however, the deposit resembles a porphyrytype occurrence in other respects, and an intrusive center of relatively strongalteration-mineralization. could exist under the alluvial covered valley east of'the mine .

Brief comments on the Untested Porphyry Copper Prespects'are included in theforegoing list.

Referring to the attached map, it is to be noted that with the exception ofChristmas, mines developed within the past 12 years '---- Mineral Park, Mission,Pima, and Esperanza --- all fall within a northwest-trending belt which includesBagdad, Sacaton, Silver Bell and Cananea . In his report on the discovery of theSacaton Prospect ( Feb . 13, 1961), Mr . Kinnison referred tc the aforementionedbelt as the Silver Bell zone, and pointed cut that the Saceton area was situatedat the intersection of this zone and two cross-trending zones which he labeled"Miami" and "Pcston Butte" . Since that time, drilling at Sacaton has demonstratedthe existence of a major-sized porphyry copper deposit', the full extent of whichhas yet to be determined . This, and other new discoveries, tend to emphasizecertain trends along which the exploration chances may be better ; but we must stilldepend on finding a lead ; such as an altered outcrop with evidence•of leached sul-phide mineralization, or altered boulders derived from a now-buried outcrop, whereverit be located --- on trend, or off .

In 1950 (above mentioned memo of Oct . 4, 1950) there were 12 "commercial"deposits (excluding Tyrone and Pilares) and 10 deposits regarded as either "non-commercial" or as "prospects" with unknown potential . The ratio has changed somein the past 12 years, but the odds still appear very favorable . Today there are17, (commercial" deposits (including Tyrone), 3 marginal, 16 sub-marginal, 8 currentlyunder exploration and 5 untested . Four of those currently under exp .lcration, SaginawHill, Chilito, Red Mt., and Four Metals, should be regarded as sub-marginal on thebasis of prior exploration results . Thus, we have a 20-25, or 4-,to-5 ratio if the3 marginal deposits are included with the 17 "commercial" deposits, and all 5 un-tested deposits are-included with the sub-marginal deposits . This ratio has nobearing on the chances of finding a new porphyry copper prospect --- due to thegreat concentration of exploration personnel in the Scuth'Nest for many years, thischance must be regarded as very slim --- but it does suggest that if a new prospect

S

k ._ -5-File Memo February 18, 1963

is found, and the zone of alteration-mineralization demonstrated to be of adequatesize (say, a half mile or more in diameter), the odds should be roughly even thatthe zone will contain a''lcommercial" ore body .

J . H . COURTRIGH`f

JHC/kwi Attachment - Map