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Arizona G e ological S urve y D igital G e ologic M ap D G M -33G e ologic map of the Espe ranza M ill 7 1/2' Q uadrangle

SAUCITOMOUNTAIN

GREEN VALLEY

SAMANIEGOPEAK

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G e ologic M ap of the Espe ranza M ill 7½’ Q uadrangle , P ima County, ArizonaJon E. S pe nce r, Charle s A. F e rguson, S te phe n M .

R ichard, and Ann Yoube rg.Arizona G e ological S urve y

D igital G e ologic M ap 33 (D G M -33)S e pte m be r 2019

Research supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program, under USGS award number #02HQAG0016. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. Introduction The Espe ranza M ill 7 ½' Q uadrangle is locate d approximate ly 40 km south-southw e st of downtown Tucson and is on the southe ast flank of the S ie rrita M ountains. The quadrangle e ncompasse s the e aste rn e dge of the Espe ranza ore body, which is now mine d from within a single large ope n pit that e ncompasse s both the S ie rrita and Espe ranza ore bodie s. It also e ncompasse s be drock hills on the southe aste rn flank of the S ie rrita M ountains, e xte nsive pie dmont alluvial de posits, S anta Cruz R ive r de posits, and e xte nsive mine tailings from the S ie rrita-Espe ranza mine . Be drock in the are a was mappe d during D e ce mbe r 2002 to M ay 2003. Q uate rnary de posits, mappe d e arlie r by P e arthre e and Yoube rg (2000), we re the targe t of mapping in spe cific are as that w e re conside re d to be incomple te ly unde rstood. In addition, all of the Q uate rnary de posits w e re e valuate d and in part re inte rpre te d base d on ae rial photograph inte rpre tation. All of this mapping was done as part of a multiye ar mapping program dire cte d at producing comple te ge ologic map cove rage for the P hoe nix-Tucson m e tropolitan corridor. This map is one of four 1:24,000 scale ge ologic maps that cove r most of the S ie rrita M ountains and that w e re produce d for this study. This mapping was done unde r the joint S tate -F e de ral S TATEM AP program, as spe cifie d in the National G e ologic M apping Act of 1992. M apping was jointly funde d by the Arizona G e ological S urve y and the U.S . G e ological S urve y unde r S TATEM AP P rogram Contract #02HQ AG0016. The be drock ge ology of the map are a is dominate d by the Cre tace ous D e m e trie Volcanics and Oligo-M ioce ne ande site and dacite , both which w e re pre viously mappe d by Coope r (1973) at a scale of 1:48,000. The Cre tace ous D e m e trie Volcanics and stratigraphically unde rlying Cre tace ous conglom e rate and Jurassic rhyolite are intrude d by the e arlie st Te rtiary R uby S tar granodiorite in the northw e ste rn part of the map are a. At the northw e ste rn corne r of the map are a, the se M e sozoic rock units are burie d by the mine dump adjace nt to the S ie rrita-Espe ranza porphyry coppe r ore body (L ynch, 1968; Aike n, and W e st, 1978; W e st and Aike n, 1982; P re e ce and Be ane , 1982). The D e m e trie Volcanics and ove rlying Oligo-M ioce ne ande site and dacite are ove rlain by e xte nsive Q uate rnary pie dmont alluvial de posits that e xte nd e astward to the S anta Cruz R ive r. This map include s update d mapping and inte rpre tations base d on the e arlie r mapping of Q uate rnary de posits by P e arthre e and Yoube rg (2000). Acknowledgments W e e spe cially thank D an Aike n of P he lps-D odge S ie rrita Inc. for his e fforts in obtaining pe rmission for the authors to e nte r P he lps-D odge prope rty. He and Gre g Baugh are grate fully acknowle dge d for providing acce ss to mine maps,

othe r information re garding the ge ology of the S ie rrita mine are a, and many inte re sting and informative discussions. W e also thank M at Turne r of Cate rpillar Inc. for granting pe rmission to map on Cate rpillar prope rty. References Cited Aike n, D .M ., and W e st, R .J., 1978, S om e ge ologic aspe cts of the S ie rrita-Espe ranza coppe r-molybde num de posit,

P ima County, Arizona, in Je nne y, J.P ., and Hauck, H.R ., e ds., P roce e dings of the P orphyry Coppe r S ymposium, Tucson, Ariz., M arch 18-20, 1976: Arizona G e ological S ocie ty D ige st, v. 11, p. 117-128.

Be tancourt, J.L., 1990, Tucson’s S anta Cruz R ive r and the arroyo le gacy: Tucson, Unive rsity of Arizona, unpublishe d P h.D . disse rtation, 239 p.

Bilode au, W .L., and K e ith, S .B., 1986, L ow e r Jurassic Navajo-Azte c-e quivale nt sandstone s in southe rn Arizona and the ir pale oge ographic significance : Am e rican Association of P e trole um G e ologists Bulle tin, v. 70, p. 690-701.

Busby-S pe ra, C.J., 1988, S pe culative te ctonic mode l for the e arly M e sozoic arc of the southw e st Cordille ran Unite d S tate s: G e ology, v. 16, pl 1121-1125.

Coope r, J.R ., 1971, M e sozoic stratigraphy of the S ie rrita M ountains, P ima County, Arizona: U.S . G e ological S urve y P rofe ssional P ape r 658-D , 42 p.

Coope r, J.R ., 1973, G e ologic map of the Twin Butte s Q uadrangle , southw e st of Tucson, P ima County, Arizona: U.S . G e ological S urve y M isce llane ous G e ological Inve stigations M ap I-745, scale 1:48,000.

D ickinson, W .R ., F iorillo, A.R ., Hall, D .L., M onre al, R ., P otochnik, A.R ., and S wift, P .N., 1989, Cre tace ous strata of southe rn Arizona, in Je nny, J.P ., and R e ynolds, S .J., e ds., G e ologic e volution of Arizona: Arizona G e ological S ocie ty D ige st 17, p. 397-434.

He rrmann, M .A., 2001, Episodic magmatism and hydrothe rmal activity, P ima M ining D istrict, Arizona: Tucson, Unive rsity of Arizona, M .S . the sis, 44 p.

Je nse n, P .W ., 1998, A structural and ge oche mical study of the S ie rrita porphyry coppe r syste m, P ima County, Arizona: Tucson, Unive rsity of Arizona, M .S . the sis, 136 p.

L ynch, D .W ., 1967, G e ology of the Espe ranza mine and vicinity, P ima County, Arizona: Tucson, Unive rsity of Arizona, M .S . the sis, 70 p., with map, scale 1:6,000 (map date d 1963).

L ynch, D .W ., 1968, The ge ology of the Espe ranza mine , in Title y, S .R ., e d., S outhe rn Arizona G uide book III: Arizona G e ological S ocie ty, p. 125-136.

M ache tte , M .N., 1985, Calcic soils of the southw e ste rn Unite d S tate s, in W e ide , D .L., e d., S oils and Q uate rnary G e ology of the S outhw e ste rn Unite d S tate s: G e ological S ocie ty of Am e rica S pe cial P ape r 203, p. 1-21.

M e nge s, C.M ., and M cF adde n, L.D ., 1981, Evide nce for a late st M ioce ne to P lioce ne transition from Basin-R ange te ctonic to post-te ctonic landscape e volution in southe aste rn Arizona: Arizona G e ological S ocie ty D ige st 13, p. 151-160.

P e arthre e , P .A., and Calvo, S .S ., 1987, The S anta R ita fault zone : Evide nce for large magnitude e arthquake s with ve ry long re curre nce inte rvals, Basin and R ange province of southe aste rn Arizona: Bulle tin of the S e ismological S ocie ty of Am e rica, v. 77, p. 97-116.

P e arthre e , P .A., and Yoube rg, Ann, 2000, S urficial ge ologic map and ge ologic hazards of the G re e n Valle y – S ahuarita are a, P ima County, Arizona: Arizona G e ological S urve y Ope n-F ile R e port 00-13, 21 p., two maps, scale 1:24,000.

P re e ce , R .K ., III, and Be ane , R .E., 1982, Contrasting e volutions of hydrothe rmal alte ration in quartz monzonite and quartz diorite wallrocks at the S ie rrita porphyry coppe r de posit, Arizona: Economic G e ology, v. 77, no. 7, p. 1621-1641.

S tre cke ise n, A.L., 1973, P lutonic rocks: Classification and nom e nclature re comm e nde d by the IUG S S ubcommission on the S yste m atics of Igne ous R ocks: G e otim e s, v. 18, n. 10, p. 26-30.

Tosdal, R .M ., Haxe l, G.B., and W right, J.E., 1989, Jurassic ge ology of the S onoran D e se rt re gion, southe rn Arizona, southe aste rn California, and northe rnmost S onora: Construction of a contine ntal-margin magmatic arc, in Je nne y, J.P ., and R e ynolds, S .J., e ds., G e ologic e volution of Arizona: Arizona G e ological S ocie ty D ige st, v. 17., p. 397-434.

W e st, R .J., and Aike n, D .M ., 1982, G e ology of the S ie rrita-Espe ranza de posit, P ima mining district, P ima County, Arizona, in Title y, S .R ., e d., Advance s in ge ology of the porphyry coppe r de posits, southw e ste rn North Am e rica: Tucson, Unive rsity of Arizona P re ss, p. 433-465.

W ood, M .L., House , P .K ., and P e arthre e , P .A., 1999, Historical ge omorphology and hydrology of the S anta Cruz R ive r: Arizona G e ological S urve y Ope n-F ile R e port 99-13, 98 p., with map, scale 1:100,000.

Yoube rg, A., and He lmick, W .R ., compile rs, 2001, S urficial ge ology and ge ologic hazards of the Amado-Tubac are a, S anta Cruz and P ima Countie s, Arizona: Arizona G e ological S urve y D igital G e ologic M ap 13, scale 1:24,000.

Correlation Diagram

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Qy3

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Qi4

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middleTe rtiary

Jurassic

Cre tace ous

144 M a

65 M a

e arlyTe rtiary

Te rtiary L ate

Holocene

Pleistocene

L ate M ode rn

Early

M iddle

L ate

L ate st

Early

M id L ate

Quaternary

S CALE 1:24,0001 0 10.5 M ile s

1 0 10.5 K ilom e te rs

0 1100 2200330044005500F e e t

CONTO U R INTER VAL 40 F EET

Topographic base map de rive d from the Espe ranza M ill 7.5' U S G S topographic quadrangle map originallywith NAD 27 datum. R e proje cte d to UTM NAD 83 datum (zone 12) using iG age All Topo M aps V9. UTMNAD 83 grid and lat-lon marke rs produce d using ES R I ArcM ap v. 10.4.

Map Unit Descriptions

Quaternary and Latest Tertiary Map Units

River Deposits

River channel deposits - River channel deposits of the S anta Cruz R ive r, compose d primarily of sand and pe bble s. Along the S anta CruzR ive r, mode rn channe ls are typically e ntre nche d se ve ral m e te rs be low adjace nt young te rrace s. The curre nt e ntre nche d channe lconfiguration be gan to e volve with the de ve lopm e nt of arroyos in the late 1800's, and continue d to e volve through this ce ntury(Be tancourt, 1990; W ood and othe r, 1999). Channe ls are e xtre m e ly flood prone and are subje ct to de e p, high ve locity flows in mode rateto large flood e ve nts. Banks along som e portions of the S anta Cruz R ive r have be e n prote cte d with soil ce m e nt, but othe r re ache d areunprote cte d and are subje ct to se ve ral late ral e rosion during floods.

Qycr

Floodplain and terrace deposits - F loodplains and low te rrace s flanking the main channe l syste m along the S anta Cruz R ive r. M ost Q yrare as along the S anta Cruz R ive r are part of the active floodplain and may be inundate d in large floods. Te rrace surface s are flat andune rode d, e xce pt imm e diate ly adjace nt to channe ls. Q yr de posits consist of w e akly to unconsolidate d sand, silt, and clay with som ele nse s of coarse r mate rial. The se de posits are inte rbe dde d with pie dmont Q y and Q iy de posits. S oils are w e akly de ve lope d, with som ecarbonate filam e nts and fine masse s and w e ak soil structure in ne ar surface horizons. L ocally, Q yr surface s may e xpe rie nceshe e tflooding during large floods in are as whe re the main channe l is not de e ply e ntre nche d, and as a re sult of flooding on local tributarie sthat de bouch onto Q yr surface s. Unprote cte d channe l banks form e d in Q yr de posits are ve ry susce ptible to late ral e rosion.

Qyr

Piedmont Alluvium

Active channels - Active channels compose d of mode rate ly-sorte d sand and pe bble s with som e cobble s in the low e r pie dmont are as tove ry poorly-sorte d sand, pe bble s, and cobble s with som e boulde rs in the uppe r pie dmont are as. Channe ls are ge ne rally incise d le ssthan 1 m be low adjace nt Holoce ne te rrace s and alluvial fans, but locally incision may be as much as 2 m. Channe l morphologie sge ne rally consist of a single thre ad high-flow channe l or multi-thre ade d low-flow channe ls with grave l bars. Channe ls are e xtre m e ly floodprone and are subje ct to de e p, high ve locity flows in mode rate to large flow e ve nts, and se ve re late ral bank e rosion. F lood flows maysignificantly change channe l morhology and flow paths.

Qyc

Active channel and bar deposits - Active channel and bar deposits compose d of mode rate ly-sorte d sand and pe bble s with som e cobble sin the low e r pie dmont are as to ve ry poorly-sorte d sand, pe bble s, and cobble s with som e boulde rs in the uppe r pie dmont are as. Channe lsare ge ne rally incise d le ss than 1 m be low adjace nt Holoce ne te rrace s and alluvial fans, but locally incision may be as much as 2 m. Channe l morphologie s ge ne rally consist of a single thre ad high flow channe l or multi-thre ade d low flow channe ls w ith grave l bars. Channe ls are e xtre m e ly flood prone and are subje ct to de e p, high ve locity flows in mode rate to large flow e ve nts, and se ve re late ral banke rosion.

Qy3

Very Young alluvial fan, terrace and channel deposits - Ve ry young de posits in low te rrace s, alluvial fans, and small channe ls that are partof the mode rn drainage syste m. Include s Q yc whe re not mappe d se pe rate ly. In the uppe r pie dmont are as, channe l se dim e nt isge ne rally poorly to ve ry poorly sorte d sand and pe bble s, but may include cobble s and boulde r; te rrace and fan surface s are typicallymantle d with sand and fine r se dim e nt. On low e r pie dmont are as, young de posits consist pre dominantly of mode rate ly sorte d sand andsilt, with som e pe bble s and cobble s in channe ls. Channe ls ge ne rally are incise d le ss than 1 m be low adjace nt te rrace s and fans, butlocally incision may be as much as 2 m. Channe ls morphologie s ge ne rally consist of a single -thre ad high flow channe l or multi-thre ade dlow flow channe ls with grave l bars adjace nt to low flow channe ls. F lood flows may significantly change channe l morphology and flowpaths. D ownstre am-branching distributary channe l patte rns - small, discontinuous, w e ll-de fine d channe ls alte rnating with broade xpansion re ache s whe re channe ls are ve ry small and poorly de fine d - are associate d with the fe w young alluvial fans in the are a. L ocalre lie f varie s from fairly smooth channe l bottoms to undulating bar-and-swale topography that is characte ristic of coarse r de posits. Te rrace s have planar surface s, but small channe ls are common. S oil de ve lopm e nt associate d with Q y2 de posits is w e ak.

Qy2

Young terrace deposits - Young terrace deposits found at scatte re d locations along incise d drainage s throughout the S ie rrita pie dmont. Q y1 surface s are highe r and le ss subje ct to inundation than adjace nt Q y2 surface s, and are ge ne rally planar. L ocal surface re lie f may beup to 1 m whe re grave l bars are pre se nt, but typically is much le ss. Q y1 surface s are 1 to 2 m above adjace nt active channe ls. S urface stypically are sandy but locally have unvarnishe d ope n fine grave l lags. Q y1 soils typically are w e akly de ve lope d, w ith som e soil structurebut little clay and stage I to II calcium carbonate accum ulation (se e M ache tte , 1985, for de scription of stage s of calcium carbonateaccum ulation in soils). Ye llow brown (10YR ) soil color is similar to original fluvial de posits.

Qy1

Young alluvium, undifferentiated - Unit Q y include s units Q yc, Q y2 and Q y1 and is use d whe re it was not possible , at a scale of 1:24000,to se parate ly map the de posits. Unit Q y consists of smalle r incise d drainage s on the pie dmonts and more e xte nsive young alluvial fans atthe base of the pie dmonts, adjace nt to the S anta Cruz floodplain. S oil de ve lopm e nt consists of cam bic horizons ove r w e ak to mode rate(stage I to II) calcic horizons. This map unit include s units Q 5 and Q 4 of He lmick (1986), and units 3B and 4 of P e arthre e and Calvo(1987).

Qy

Young and young intermediate alluvial fan deposits - Broadly rounde d alluvial fan surface s approximate ly 1 m above active channe lscompose d of mixe d alluvium of late P le istoce ne and Holoce ne age . D rainage ne tworks consist of a mix of distributary channe l ne tw orksassociate d w ith large r drainage s and tributary channe ls associate d w ith smalle r drainage s that he ad on Q iy surface s. Q iy are as areprimarily cove re d by a thin ve ne e r of Holoce ne fine -graine d alluvium (unit Q y), but re dde ne d P le istoce ne alluvium (unit Q i3 and rare ly,Q i2) is e xpose d in patche s on low ridge s and in roads and cut banks of washe s. The Holoce ne surface s usually are light brown in colorand soils have w e ak subangular blocky structure and minor carbonate accum ulation. Q iy fans support palo ve rde and me squite tre e salong w ashe s and low shrubs and grass in inte rfluve are as. This unit is ge ne rally corre lative with units 2d and 3a of P e arthre e and Calvo(1987).

Qiy

Very young intermediate alluvial fan and terrace deposits - Unit Q i4 consists of slightly disse cte d re lict alluvial fans and te rrace s found onthe uppe r, middle and low e r pie dmont. M ode rate ly de ve lope d, slightly incise d tributary drainage ne tworks are typical on Q i4 surface s.Active channe ls are incise d 1-2 m be low Q i4 surface s. Q i4 de posits consist of pe bble s, cobble s, and fine r-graine d se dim e nt. Q i4 surface shave ope n lags of pe bble s and cobble s; surface clasts e xhibit w e ak rock varnish. Q i4 soils are mode rate ly de ve lope d, with orange tore ddish brown clay loam cam bic to w e ak argillic horizons and stage II calcium carbonate accum ulation. D ominant forms of ve ge tationinclude grasse s, small shrubs, m e squite , and palo ve rde . Unit Q i4 is ge ne rally corre lative with unit 2d of P e arthre e and Calvo (1987).

Qi4

Young intermediate alluvial fan and terrace deposits - Unit Q i3 consists of slightly to mode rate ly disse cte d re lict alluvial fans and te rrace sfound on the uppe r, middle and low e r pie dmont. M ode rate ly to w e ll-de ve lope d, slightly to mode rate ly incise d tributary drainage ne tworksare typical on Q i3 surface s. Active channe ls are incise d up to about 2 m be low Q i2 surface s. Q i3 fans and te rrace s are commonly low e rin e le vation than adjace nt Q i2 and olde r surface s, but the low e r margins of Q i3 de posits lap out onto more disse cte d Q i2 surface s insom e place s. Q i3 de posits consist of pe bble s, cobble s, and fine r-graine d se dim e nt. Q i3 surface s commonly have loose , ope n lags ofpe bble s and cobble s; surface clasts e xhibit w e ak rock varnish, and appe ar light orange to dark orange on color ae rial photos, re fle ctingre dde ning of surface clasts and the surface soil horizon. Q i3 soils are mode rate ly de ve lope d, with orange to re ddish brown clay loam tolight clay argillic horizons and stage II calcium carbonate accum ulation. D ominant forms of ve ge tation include grasse s, small shrubs,cholla, prickly pe ar, barre l cacti, and me squite . O cotillo occurs whe re carbonate pare nt mate rial e xists.

Qi3

Intermediate alluvial fan and terrace deposits - Unit Q i2 consists of mode rate ly to highly disse cte d re lict alluvial fans and te rrace s withstrong soil de ve lopm e nt found throughout the map are a. Q i2 surface s are draine d by w e ll-de ve lope d, mode rate ly to de e ply incise dtributary channe l ne tworks. Channe ls are typically se ve ral m e te rs be low adjace nt Q i2 surface s with channe l disse ction incre asingtow ards the mountains and the southe rn e nd of the map are a. W e ll-pre se rve d, planar Q i2 surface s are smooth with scatte re d pe bble andcobble lags; surface color is re ddish brown; rock varnish on surface clasts is typically orange or dark brown. M ore e rode d, rounde d Q i2surface s are characte rize d by scatte re d cobble lags with mode rate to strong varnish and broad ridge -like topography. W e ll-pre se rve d Q i2surface s have a distinctive dark re d color on color ae rial photos, re fle cting re dde ning of the surface soil and surface clasts. S oils typicallycontain re dde ne d, clay argillic horizons, w ith obvious clay skins and subangular to angular blocky structure . Unde rlying soil carbonatede ve lopm e nt is typically stage II-III, with abundant carbonate through at le ast 1 m of the soil profile ; indurate d pe trocalcic horizons arerare . Carbonate de ve lopm e nt is stronge r towards the north e nd of the map are a, and in are as whe re carbonate pare nt mate rial e xists.Q i2 surface s ge ne rally support grasse s, cholla, prickly pe ar, barre l cacti, m e squite and ocotillo. This unit is ge ne rally corre lative to unit Q 2of He lmick (1986) and unit Q 2b of P e arthre e and Calvo (1987).

Qi2

Older intermediate alluvial fan and terrace deposits - D e posits associate d with de e ply disse cte d re lict alluvial fans. Q i1 surface s formbroadly rounde d ridge s that are highe r than adjace nt Q i2 surface s but not as high or e rode d as adjace nt Q o surface s or the highe st Q Tade posits. Tributary drainage ne tworks are incise d 3 to 6 m, incre asing towards the mountains. Erode d Q Ta de posits are occasionallye xpose d along som e ridge slope s. W he re w e ll pre se rve d, Q i1 soils are strongly de ve lope d with a distinct dark re d (5-2.5 YR ), he avy clayargillic horizon and subangular blocky to prismatic structure . Carbonate accum ulations are 1-2 m thick and range from stage III - V.

Qi1

Old alluvial fan deposits - D e posits associate d with ve ry old, high, de e ply disse cte d alluvial fan re mnants with mode rate ly w e ll-pre se rve dfan surface s and strong soil de ve lopm e nt. Q o de posits and fan surface re mnants are scatte re d across the southe rn S ie rrita pie dmont,but are be st pre se rve d surface s are ne ar the mountain front. Q o surface s range from fairly smooth and planar to rounde d ridge s. Q ode posits vary from cobble s and boulde rs to sand, silt and pe bble s. S tage III to IV calcic horizons are typical, but not always pre se nt. W he re surface s are planar and w e ll-pre se rve d, re d (5 - 2.5 YR ), he avy clay argillic horizons are typical, but may include pocke ts ofmode rate ly de ve lope d, re ddish brown (7.5YR ), sandy loam with scatte re d grave l lag. Q o surface s re cord the highe st le ve ls ofaggradation in the S anta Cruz Valle y, and are probably corre lative with othe r high, re mnant surface found at various locations throughoutsouthe rn Arizona (M e nge s and M cF adde n, 1981; Yoube rg and He lmick, 2001).

Qo

Very old alluvial fan deposits - Unit Q Ta is a basin fill de posit consisting of ve ry old, de e ply disse cte d and highly e rode d alluvial fande posits de rive d from ne arby mountains. Q Ta surface s are alte rnating e rode d ridge s and de e p valle ys, w ith ridge cre sts typically 10 to 30me te rs above adjace nt active channe ls. Q Ta ridge s are more de e ply incise d towards the mountains and the southe rn e nd of the mapare a. Q Ta surface s are draine d by de e ply incise d tributary channe l ne tworks. G e ne rally Q Ta ridge s are rounde d e xce pt whe re toppe d byplanar re mnants of Q o alluvium ne ar the mountain fronts. P ocke ts of re d, w e ll de ve lope d soil mantle som e of the hillslope s. Q Ta de positsare dominate d by subangular to subrounde d boulde rs, cobble s, and grave ls with laye rs and le nse s of sand, silt and clay. D e posits aremode rate ly indurate d and are quite re sistant to e rosion be cause of the large clast size and carbonate accum ulation, which can varylocally from stage III-V (ce m e nte d pe trocalcic horizons with laminar cap). Ve ge tation on Q Ta surface s typically are grasse s with scatte re dcacti, m e squite , acacia, and ocotillo.

QTa

Other Units

Saprolite derived from Tertiary bedrock - Q isis a saprolite that forms in situ ove r Te rtiary be drock units Tdh and Ta. The saprolite varie sfrom disaggre gate d, angular be drock clasts to w e ll-de ve lope d, re dde ne d, clay-rich re sidual soil, which grade s into be drock and re tainsbe drock te xture in the C horizon.

Qis

Hillslope talus and colluvium - Unit Q tc consist of locally-de rive d de posits on mode rate ly ste e p hillslope s. Colluvium is ve ry e xte nsive inthe mountains, but mappe d only whe re suffice ntly thick and e xte nsive as to obscure unde rlying be drock. D e posits are ve ry poorly sorte d,ranging from clay to cobble s and boulde rs. Clasts typically are subangular to angular be casue the y have not be e n transporte d ve ry far. Be dding is w e ak and dips are quite ste e p, re fle cting the ste e p de positional e nvironm e nt. D e posits are a fe w m e te rs thick or le ss; thicke stde posits are found at the base s of hillslope s. S om e stable hillslope s are cove re d primarily with P lie stoce ne de posits, which are typicallyre dde ne d and e nriche d in clay. O the r more active hillslope s are cove re d with Holoce ne de posits, which have minim al soil de ve lopm e nt.

Qtc

Ground disturbance from mining activities - Are as disturbe d by mining or othe r activitie s that comple te ly obscure or re move thepre e xisting natural surface . Include s mining-re late d tailings, dumps, le ach pads and e xcavate d rock whe re not mappe d se parate ly, andothe r disturbance s such as stock tanks.

d

Bedrock Units

D e m e trie Volcanics, ande site (L ate Cre tace ous) - M assive ande site volcanic rocks and possible hypabyssal e quivale nts. G e ne rallyconsists of m e dium to dark gray rock with 5-40% 1-4 mm gray to chalky white plagioclase (?) and 2-15%, <2 mm biotite (?). F latte ne dinclusions, re pre se nte d by 1-10 cm long, 0.5-5 cm thick pits form e d afte r lithic fragm e nts(?), de fine fabric that could be re late d tohorizontal flow and ve rtical flatte ning. F aint flow(?) banding, de fine d by diffe re nce s in re sistance to w e athe ring, could be flow banding. Crude laye ring in autoclastic bre ccia also de fine s planar fabric e le m e nt that could be re late d to lava flow ove r the Earth's surface . S outhof Espe ranza W e ll this unit appe ars locally as fine -graine d quartz(?)-fe ldspar-biotite porphyry with quartz-e pidote alte ration. In thinse ction this rock contains 0-12%, 0.2-2.0 mm, brown biotite (?) that is typically rimm e d with opaque mine rals (probably iron oxide s). Opaque s, 0.1-0.5 mm, make up as much of 15% of rock. Birdse ye maple e xtinction is stronge st indicator that this mine ral is biotite . Anothe r cle ar mine ral could be biotite that has lost its iron due to alte ration. One crystal containe d a brown core , cle ar zone around thebrown ce nte r, and opaque rim. P ossibly, the cle ar zone re pre se nts biotite that has be e n de ple te d in iron, and this iron is now in theopaque rim. Extinction is paralle l to long axis of biotite (?) crystals and paralle l cle avage . It is e stim ate d that, unalte re d, this rock unitwould contain about 10% brown biotite and 5% opaque s. Alte re d, 0.3-3.0 mm fe ldspar, make s up 35-60% of the rock. Albite tw inning iscommon in som e sample s, rare in othe r. This unit re sts on tuff (map unit K dlr), which in turn re sts on conglom e rate (map unit K cg) that isintrude d by the 64.3 ± 0.4 M a R uby S tar granodiorite . The R uby S tar granodiorite was intrude d at sufficie nt de pth (probablyse ve ral kilom e te rs) that it did not de ve lop hypabyssal te xture s. W e the re fore infe r that the D e m e trie Volcanics are olde r than the R ubyS tar granodiorite , and so are probably olde r than te rtiary (the Cre tace ous-Te rtiary boundary is date d at 65.5 M a). The conglom e rate andsandstone that unde rlie the D e m e trie Volcanics are conside re d to be Cre tace ous in age and broadly corre lative with the Bisbe e G roupand or F ort Critte nde n F ormation (D icke nson e t al., 1989). W e the rfore conside r the D e m e trie Volcanics to be late Cre tace ous in age .

Kd

Demetrie Volcanics, andesite, altered (Late Cretaceous) - Ande sitic lava flows and volcanoge nic bre ccias that w e re subje cte d to oxidizingalte ration that conve rte d biotite and othe r mafics to iron oxide s and produce d pre vasive orangish-brown iron-oxide staining that is visiblein outcrop and conce ntrate d on fracture surface s.

Kda

Demetrie Volcanics, lower rhyolite tuff (Late Cretaceous) - L ithic tuff e xpose d be tw e e n the S ie rrita-Espe ranza mine dump and D e m e trieW ash (Coope r, 1971, 1973). Tuff is light gray to tan with flatte ne d aphyric volcanic-lithic fragm e nts, 3-100 mm, forming up to 70% of rock.Conte nt of volcanic lithic fragm e nts varie s ove r te ns of m e te r in som e are as. Also include s <1%, <1 mm fe ldspar and up to 4%,<4mm quartz phe nocrysts. In roadcuts along Cate rpillar R oad the tuff locally contains sparse 2-10 mm dark pink to re d K -fe ldxe nocrysts, spare iron-oxide staine d fracture s with discoloration ove r 1-2 cm from fracture , and sparse clots of iron oxide that look a littelike oxidize d sulfide s, but no boxwork se e n. Examination of two thin se ctions from ne ar the ce nte r of the tuff re ve als that this rockcontains 1-3%, 0.1-1.0 mm, subangular to subrounde d quartz, 2-4% 0.5-2.0 mm alte re d fe ldspar, and 1-2% alte re d mafic mine rals thatare too alte re d to ide ntify. Examination of two thin se ctions from ne ar the base of this unit re ve al 5-15% fe ldspar fragm e nts, subrounde dto subangular, with abundant volcanic lithic fragm e nts. S pe nce r e t al. (2015) re port a 75.9 +/- 1.0 M a L A-ICP -M S zircon U-P b date on asample of this unit at UTM 491266E, 3525010N.

Kdlr

Volcanic-lithic conglomerate (Cretaceous) - Volcanic-lithic pe bble -cobble conglom e rate w ith sparse quartz grains. Clasts in conglom e rateinclude gray porphyry with 30-40%, 2-4 mm blocky white fe ldspar phe nocrysts. Epidote le nse s and stringe rs are notably le ss commonthan in adjace nt fe ldspathic lithic sandstone . Contact with more quartz-rich sandstone is abrupt. O utcrop is poor, mostly boulde r-cobblecolluvium on surface .

Kvcg

Conglomerate (Cretaceous) - M assive to poorly sorte d sandy conglom e rate , conglom e ratic sandstone , and sandstone . S and containsroughly 40% quartz, 3-5% mafics, most of which is probably magne tite that locally forms lamination. Clasts are locally up to 50 cmdiam e te r, are subrounde d to subangular, and include m e dium graine d granite with 5% mafics, fine graine d le oucogranite w ith <2%mafics, fine graine d quartzite , bande d aphyric rhyolite , and coarse graine d granite with appoximate ly 10% mafics (primarily biotite ). Alle xposure s are locate d ne ar low e r D e m e trie W ash.

Kcg

Sandstone (Cretaceous) - F ine - to coarse -graine d, mode rate ly to poorly sorte d sandstone that varie s from containing sube qual amountsof quartz, fe ldspar, and lithic fragm e nt to quartz-rich sandstone with up to pe rhaps 80% quartz.Kss

Mafic to intermediate metavolcanic rocks (Cretaceous to Jurassic) - This unit consists of mafic of mafic volcanic/hypabyssal rock andautobre ccia, dark gray to blackish gray, massive , with 20% 1-2 mm plagioclase and 3-4% 1 mm dark (magne tite and clinopyroxe ne (?)). M afic volcanic/hypabyssal rocks are e ithe r intrude d into associate d autoclastic bre ccia or are gradational with it. M ost like ly both are partof intrusive /e xtrusive comple x.

KJmv

Rhyolite (Jurassic) - R hylite of infe rre d Jurassic age is e xpose d in the S ie rrita-Espe ranza mine are a whe re this unit consists of ge ne rallypale gray, massive rhyolite with faint and vague ly de fine d aphyric silicic lithic fragm e nts visible on w e athe re d surface s. In thin se ction thisrock appe are d as comple te ly re crystallize d, with 0.1-1.0 mm quartz and fe ldspar(?) crystals with 1-2%, 0.5-2.0 mm re lict plagioclase and2-3%, 1-3 mm re lict K -fe ldspar. Abundant opaque mine rals <<1mm w e re se e n in som e hand sample s but w e re not se e n in thinse ction. In som e are as unit has granular te xture and contains fre sh pink K -fe ldspar up to 5 mm diam e te r, making up ~5% of rock, thatcould be product of potassic alte ration. S om e quartz grains approximate ly 1 mm diam e te r are e nclose d by se condary K -fe ldspar. AJurassic age in infe rre d be cause of the association of the rhyolite w ith quartz are nite that is thought to be re gionally corre lative withJurassic e olian quartz are nite (e .g., Bilode au and K ie th, 1986; Busby-S pe ra, 1988; Tosdal e t al., 1989). S pe nce r e t al. (2015) re port aLA-ICP -M s U-P b zircon date of 171.9 +/- 2.7 M a from this unit.

Jr

Quartzite (Jurassic) - F ine -graine d quartzite .Jq

Mine dump and leach pads (Holocene) - Are as whe re mining ope rations have burie d ge ological fe ature s with ge ne rally coarse rockde bris.dl

Mine tailings (Holocene) - Are as whe re mining ope rations have burie d ge ologic fe ature s with fine -graine d rock de bris that was de ple te dof sulfide mine rals in the S ie rrita and Espe ranza mills.t

Tertiary Map Units

Hornblende dacite of Tinaja Peak (Tertiary) - M assive and flow bande d, ge ne rally de vitrifie d hornble nde dacite lava flows and//or shallowintrusions. Variations in re sistance to w e athe ring de fine 2-20 cm thick laye rs that are infe rre d to re fle ct igne ous flow foliation andvariations in de gre e of de vitrification. This banding is irre gular on scale of se ve ral to se ve ral te ns of m e te rs. R O ck containsapproximate ly 2-5%, 0.5-3 mm hornble nde that is locally up to 8 mm, and ~1%, <1 mm biotite .

Tdh

Lower dacite of Tinaja Peak (Tertiary) - D acite lava containing approximate ly 20%, 1-3.5 mm subhe dral to e uhe dral, rounde d, stronglyzone d plagioclase , 3-5%, 0.5-3.0 mm hornble nde , and trace s of 2 mm subhe dral to e uhe dral clinopyroxe ne , <1 mm biotite , and <0.3mm opaque phe nocrysts. M atrix is typically gray to orange -brown and crystalline . A w e ll-de ve lope d vitric autobre ccia occurs at the base ,but the carapace autobre ccia is mostly abse nt. Expose d only on the e ast side of Tinaja P e ak.

Tdx

Conglomerate and volcanic breccia (Tertiary) - Coarse -graine d clast to matrix-supporte d, ge ne rally massive conglom e rate with alight-colore d pumice ous, sandy volcaniclastic matrix. Typically contains 5-40% clasts of the low e r dacite of Escondido W ash (mao unitTdf), 30-90% clasts of the low e r dacite of Tinaja P e ak (map unit Tdx), and 10-30% clasts of M e sozoic volcanic rocks. Expose d only onthe e ast side of Tinaja P e ak. The unit mostly unde rlie s the low e r dacite of Tinaja P e ak, but appe ars to ove rlap the lava along its e aste rnmargin.

Tcx

Dacite of Escondido Wash (Tertiary) - D acitic lava containing 20-30%, 0.3-2.0 mm, e uhe dral, zone d plagioclase , and 5-7%, 0.2-2 mmsubhe dral to e uhe dral clinopyroxe ne . Expose d only in one small are a south of Tinaja P e ak. M atrix is tyoically vitric and ve ry dark, andthe lava is massive , displaying only rare zone s of autobre ccia.

Tdf

Andesite of Escondido Wash (Tertiary) - Ande site lava containing 20-30%, 0.3-2.0 mm, e uhe dral, zone d plagioclase , and 5-7%, 0.2-2 mmsubhe dral to e uhe dral clinopyroxe ne , plus sparse ye t conspicuous large phe nocrysts (xe nocrysts?) of plagioclase (<6 mm) and olivine(2-5 mm). M atrix is typically microcrystalline and crum bly. One che m ical analysis of this unit indicate s that it is an ande site .

Tdfl

Andesite of Tinaja Hills (Tertiary) - Crystal-poor mafic lava flows of probable ande site to basaltic traychyande site composition pre se rve d inam algam ate d flows w ith massive flows inte riors and abundant flow-bre ccia. R e ddish w e athe ring scoriace ous zone s locally mark flowcontacts. R are ly contains volcanic-lithic sandstone be ds up to 3 m thick be tw e e n flow bre ccias. G e ne rally contains 0.5-2%, <1 mmplagioclase phe nocryst. L ocally contains up to 5% small plagioclase phe nocryst. M icrocrystalline matrix is common strongly de vitrifie d,with a blotchy, micro-amygdaloidal te xture .

Ta

Volcanic-lithic sandstone and conglomerate (Tertiary) - Clastic se dim e ntary rocks be ne ath mafic lava flows of map unit Ta. L ocallyconsists of lapilli(?) sandstone and pe bbly volcanic lithic sandstone . Thickne ss 1-10 m.Tvs

Sierrita breccia (Tertiary) - This igne ous bre ccia unit is e xpsoe d in the S ie rrita ope n-pit coppe r mine . Examinations by Je nse n (1998)indicate s that this unit consists of 5% to 60% mafic xe noliths in a porphyritic matrix. This unit is younge r that the R uby S tar granodiorite .Tsb

Ruby Star granodiorite (Tertiary) - M e dium graine d, ge ne raly e quigranular, biotite granodiorite with 3-8% biotite typically 1-4 mm diam e te rbut locally up to 6 mm. Biotite has fre sh, re fle ctive face s in som e are as, unlike ne arby P rote rozoic granite in the Twin Butte s 7.5'quadrangle . M odalmine ral analysis by Je nse n (19980 de te rm ine d that this rock unit is in the granodiorite fie ld of the IUG S classificationsche m e (S tre cke ise n, 1973), but is ve ry close to the granite fie ld.

Tgd

<bol>R uby S tar granodiorite , porphyritic phase (Te rtiary)</bol> - M e dium graine d, porphyritic biotite granodiorite e xpose d in the S ie rrita ope n-pitcoppe r mine . K nown locally as the Espe ranza quartz monzonite porphyry. A sample of this rock unit yie ld a U-P b zircon date of 64.3&plusmn; 0.4 M a (He rrmann, 2001).

Tgx

Felsite intrusion (Tertiary) - W hite fe lsite , crystal poor, with sparse 0.5-1 mm quartz crystals, and abundant se ricite afte r fe ldspar(?); a fe wle nse s of m e dium-graine d granitoid are pre se nt.TKf

Mafic dike (Tertiary or Cretaceous) - Ve ry dark gray to black, fine ly crystalline to aphanitic mafic dike rock w ith chille d margins.TKmd

Cretaceous and Jurassic Map Units

Andesite intrusion (Late Cretaceous) - M assive intusive ande site , contains ~40% crystals, including 1 mm e uhe dral plagioclase (~25%),15-20% mafic crystals (hornble nde ?) alte re d to chlorite , in me dium to dark gray aphanitic graoundm ass. Host tuff appe ars slightly atirre gular, inte rdigitate d contact.

Ka

Arizona Geological Survey1955 East S ixth S tre e t, P O Box 210184

Tucson, AZ 85721(520) 621-2470

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