Canodian Mineralogist Yol.26, pp. 355-376(1988)

COEXISTINGGALENA, PbSo AND SULFOSALTS:EVIDENCE FOR MULTIPLE EPISODESOF MINERALIZATIONIN THE ROUND MOUNTAIN AND MANHARAN GOLD DISTRICTS.NEVADA

EUGENE E. FOORD ANDDANIEL R. SHAWE M.S. 905, U.S. GeologicalSuney, Box 25046,Denver Federal Cmter, Lakewood, Colorado 80225, U.S.A. NANCY M. CONKLIN M.S. 928,U.S. GeologicalSumey, Box 25M6, DenverFederal Center, Lokewood, Colorado 80225, U.S.A.

ABSTRACT CuSIg) i compositionvariable, provenantdes disfiicts auri- fbres de Round Mountaitr et de Manhattan, au Nevada, Studies of galena and Pb-Bi Ag-Cu(I{g) sulfosalts of confirment la pr€sencede plusieurs 6pisodesdistincts de varied compositions in the Round Mountain and Manhat- mindralisation, dont temoiguent les diff€rents champs de tan gold districts of Nevada corroborate the occurrenceof composition et assemblagesde min€raux. Si les dpisodes severaldistinct mineralizedsystems characterized by differ- de mindralisation sont li6s d divers 6v6nements ent mineral compositions and assemblages.The different magmatiques-hydrothermaux,d'6ge cr6tac6i tertiaire, en mineralization related episodesof are to different Creta- revanche I'attribution de compositions et d'associations ceous and Tertiary magnatic-hydrotiermal events, sp6cifiquesd des6v6nements de min6ralisation d'6ge connu although the assignmentof specific mineral compositions demeureincomplEte. A la mine Fairview, la galOneassoci€e and associations with dated mineralized systems is still aux sulfosels Pb-Bi-Ag et aux sulfures simples se trouve incomplete. galena At the Fairview mine, associatedwith e! intercroissancesdont la composition globale d6finit des Pb-Bi-Ag inter- sulfosalts and simple sulfides @curs as ft€roupsments €Nrtermes de teneur en argent et en bismuth. growths of discretely different composition controlled by Nous avonstrouvd une composition intermddiairede galine galena-type phase silver and bismuth content. A @bSo) (PbSs, Gal60Mata6) enrichie dans Ie terme matildite with solid solution toward matildite, (composition fuBi$ AgBiq. Si l'argent et, i un degrdmoindre, le bismuth sont Gal6sMatao)was found. If silver and, to a lesser extent, absents, la galbne form6e par exsolution est par contre bismuth are absent, the galenaformed will be pure almost presque stoechiom6trique. L'antimoine, en faibles quan- PbS. Some minor antimony may substitute for bismuth. titds, peut remplacer le bismuth. Ces r&ultats confirment This study confirms a linear relationshipbetween a cell edge la relation lindaire entre le param€tre rdticulaire a et la and Ag-Bi(Sb) for galena less content containing than about proportion de Ag-Bi(Sb) dans la galbnepour des teneurs 15 wt. 9o Ag and B(Sb). Other Pb-Bi-Ag-Cu(Hg) sulfides (en poids) infdrieures i l5Vo Ag + Bi(Sb) environ. On a from and sulfosaltsidentified the districts are bismuthinile, pu identifio d'autres sulfures et sulfosels de Pb-Bi-Ag- galenobismutite,lillianite-gustavite, aikinite, friedrichit{?), CUGIg)r bismuthinite, galenobismutite,lillianire-gustavite, hammarite, ourayite, and berryite(?). PhasesX and Y, aikinite, friedrichite(?), hammarite, ourayite, et berryite(?). mercury-bearingPb-Bi-Ag-Cu sulfosalts (most likely new On siguale la pr€sencedes phasesXet I, sulfosels de Pb- species),and coloradoite were recognized from Out- the Bi-fu-Cu mercurifdres,qui sont probablementde nouvelles law prospect southeast of Round Montain. Multiple epi- espece$,ainsi que la coloradoite, dans I'indice min6ralisd mineralization (i) sodes of are supported by: coexisting de Outlaw, au sud-est de Round Mountain. Les facteurs galena, and complex sulfosalts of widely varied com- PbSo suivantsindiquent qu'il s'agit d'une multiplicit6 d'6pisodes positions and with textures that indicate successivereplace- de mindralisationl (i) une coexistencede galCne,de PbSo, ment; (ii) a characteristic but commonly incomplete para- et de sulfosels complexesd compositions trbs variables et genesis mineral (early hiibnerite, molybdenite, of species e textures qui indiquent une successiond'6pisodes de rem- galena, intermediate galena sphalerite, and chalcopyrite; plac€rnent;(ii) une paragen&ecaract6ri$tique mais typique- and Pb-Bi-Ag sulfosalts; late tetrahedrite-tennantite, ment incompldte de min€raux: hubnerite, molybd6nite, galena(?), chalcopyrite(?), covellite, and mercurian galdne, sphal6rite et chalcopyrite (prdcoces),galdne et sul- geologically geochem- minerals), some of which can be or foselsPb-Bi-Ag (intermdiaire), et tetraedrite-tennantite, (iii) ically correlated with dated deposits;and mineral com- galbne(?), chalcopyrite(?), covelline et min€raux de mer- positions (Sb:Bi as indicators of temperature of deposition cure (tardifs); danscerlains cas, dc corr6lationsg6ologiques <0.06, T 2m-3@'C; Sb:Bi >6.0-13, f 100-160'C). et g6ochimiquessont possible avecdes gftes min€raux dont l'6ge est connu; et (iii) les indicateurs de tempdrature de galena, Keywords: PbSo, Pb-Bi Ag-Cu(Hg) sulfosalts, formation i partir des compositions min6rales (Sb:Bi Round Mountain, Manhattan, Nevada. <0.06, T 200-3@oC;Sb:Bi > 6.0-13,T 100-160'C).

(fraduit par la Rddaction) SoMMAIRE Mots-clds: galEne, PbSo, sulfosels Pb-Bi-Ag-Cu(Hg), Nos €tudes de galbne et des sulfosels de Pb-Bi-Ag- Round Mountaia, Menhattan, Nevada. 355 356 THE CANADIAN MINERALOCIST

I 17000'

MOUNTJEMRSON CALDERA

f contact NEVAOA -z- ovu. Elv Round a Samole localltY \ a \ Manhdan and numDer a 8O-30 7+'142ab 7918

km

ROUNDMOUNIAIN

'ffiihFatvts mhe

Romd Mostaln gold nlne

ROUNDMOUNTAIN LOBE OFfiE GRANITEOF SHOSHONEMOUNTAIN

I -.----...\cAlvYoil_, \-.s..j_.. \ ..,-''-...- i \-._-. .._..._..\.q,ng:..i;.r/

38037',30"

Ftc. l. Simplified geologic map of the Round Mountain quadrangle, showing locations of areas studied. Qa, Quater- nary alluvium; Tv, Tertiaryvolcanicrccks (-24-27 Ma); Tg, Tertiarygranodioritestock (35 Ma); Tr, Tertiary rhyolite dykes (35 Ma); Kg, Cretaceousgranite (-80-95 Ma); Pzsm, Paleozoicsedimentary and metamorphicrocks. MINERALIZATION IN GOLD DISTRICTS' NEVADA 357

INTRoDUCTIoN GEoLocYoF THELocettttss STuPtBo

As a part of the detailed geological mapping and The southernToquima Range,in which the Round mineral resoruceappraisal of the southern Toquima Mountain and Manhattan gold districts occur, is an Range, Nye County, Nevada, the mineralogy and area of complex geology that evolved over a long paragenesesof the sulfides and coexisting Pb-Bi- period of time. Paleozoicmarine sedimentary rocks Ag-Cu sulfosalts from many of the mines and consistof Cambrian and Ordovician mostly transi- prospectsin the areawere investigated @igs. l, 2). tional facies argillite, quartzite, and carbonate that Physically and chemically different generations of were fault-thrust eastwardas the Roberts Mountains galena and sulfosalts have been recognized.In addi- allochthon during the late Devonian to Mississippian tion, field mapping, radiometric dating, and petro- Antler orogeny. Other thrust-fault events followed graphic and geochemicalstudies indicate a complex in later Paleozoicand Mesozoictimes, and they ter- sequenceof igneous activity and multiple episodes minated when granitic plutons were emplaced into of mineralization (Shawe1985, 1986,Shawe et al. the sedimentary rocks in the Cretaceous. Tertiary 1986).These studies collectively have clarified the igneousactivity involved emplacementof stocksand geological history of severalmineral deposits in the dykes, and formation of severalcalderas accompa- area, in particular the large gold-silver deposit at nied by eruption of voluminous silicic ash-flow tuffs. Round Mountain. Hydrothermal mineral deposits were formed or

lrrfnl'' 3SsJ,grr- 0 I MltS F----lJ 'I O KTOMETER

MANI.IATTAN CALI'E8A

Frc. 2. Simplified map of the Manhattan quadrangje, showing locations of areas studied. Legend as on Figure l. 358 THE CANADIAN MINERALOCIST

remineralizedin associationwith emplacementof the quarfz,.Pyrite contains sparsetiny cubesof galena, various igneousbodies. Locations of each of the and galenalikewise contains rare tiny cubesof pyrite, prospects mines and examinedare shown on Figures suggestingpossible contemporaneousformation of I and 2. the minerals. Sulfosalt minerals are molded around Following emplacementof granite plutons, a var- broken grains of pyrite and molybdenite flakes. iety of small, mosfly uneconomicbase- and precious- Covellite occurs as a replacementof and a fracture metal veins and tungsten-bearing tactite and vein filling in galena.Muscovite fills shearsin quartz and depositsformed at 75-80 Ma in the granite and in lines vein margins, and sparsehiibnerite occurs as nearby Paleozoic carbonate and clastic rocks. The 1iny, l- to 2-mmJong crystals embeddedin massive tactite and vein deposits characteristically contain white vein quartz. Limonite is a cornmon alteration pyrite, sphalerite, galena, and chalcopyrite as initial mineral a1the Fairview mine. Anglesite and cerus- components. Other sulfide and sulfosalt minerals in site are weathering products of galena. the deposits appear to be the products of younger mineralizing events on the basis of textural critera. Lead-Silver For example, tetrahedrite-tennantite typically fills King prospect vugs in quartz, is molded around earty sumde The Lead-Silver King prospect Iies in a zone of minerals, or fills fractures in broken sulfide mineral base-and precious-metalmineral depositsalong the grains in someof the quartz veins. Tungsten-bearing southwesternmargin of the Mount Jeffersoncaldera. veins granite in were remineralizedwith copper, lead An intensely sheared,mineralized zone a few meters zinc, arsenic,and antimony in the vicinity of a 35 yrd9, a northwest-trendingfault that separares granodiorite 4gng Ma stock and associatedrhyolite dyke- Ordovician carbonaterocks from a large horse of swarm. Tourmaline mineralization of granite and Tertiary rhyolite tuff, is about l(D m outside the cal_ rhyolite dykes accompanied emplacement of the dera. Irregular, thin quartz veins in the shearedzone stock. The main gold-silver mineralization at Round contain galenaas irregular massesas much as several Mountain occurred at 25 Ma within a rhyolitic ash- cm long, either as fillings of shearedmilky quanz, flow tuff. An economically significant gold-silver or as crudelytabular massesin quartz-linedvugs. The mineralizing eventat Manhattan took ptaceat 16 Ma quartz in vugs comrnonly is broken and healed. within Paleozoicphyllitic argillite, quartzite, and car- Cleavagesurfaces of some galena massesare nora- bonate along the south margin of the Manhattan cal- bly curved. As seenin polished section, somegalena dera. A separatebut undated Tertiary mineralizing displays minute veinlets of marcasite, mosi com- event introduced mercury, antimony, and arsenic monly oriented along the cleavageplanes. Oxidation minerals into the easternpart of the Manhattan belt. products in the galena-bearingquartz veins include The mercury mineralization produced a few small limonite, beudantite,and cerussite. mineabledeposits; it waswidespread, and overlapped older zones of base- and precious-metal veins-.- Prospect southeost of Round Mountain Fainiew mine An unnamed prospect shaft in granite of the Round Mountain lobe of the granite of Shoshone The Fairview mine lies at the eastern edge of a Mountain (Shawel98la) about 2 km southeastof mineralized zone in rhyolitic tuff that contains the Round Mountain exposes 3 or 4 closely spaced Large2SMa gold-silver deposit at Round Mountain. northeast-trending nearly vertical quartz veins The Fairview mine produced gold mostly from thin l-20 cm wide. The quartz-vein material, in appear- stringersin shearedrock parallel to a west-northwesr- ance typical of the 80 Ma veins, contains pyr.ite, striking fault, not far above a depositional contacr sphalerite, stibnite, and aikinite. Veinlets of covel- of tuff on granite and Paleozoicrocks. Theseoxi- Iite occur in the sulfides and sulfosalts. Alteration dized bodies contained gold associated with iron products of aikinite are abundant medium-yellow (from oxides pyrite) in drusy quartz, as well as gold ocherous bismutite and minor anglesite. Locally, plates interspersed in mosaic-textured vein quartz tabular massesof limonite derived from pyrite are (Ferguson l92l). Judgedfrom materialson the waste as much as 3 cm thick and line vein margins. Serici- dumps at the Fairview mine, mining extendeddown- tized granite wallrock contains small disseminated ward from veins and stringers in rhyolitic luff into grains of pyrite and molybdenite, and sparse thin the underlying granite, where thin quartz veins were veinlets of pyrite. The prospect lies within 80 m of encountered.The vein material, texturally like nearby a northeast-trending rhyolite dyke of the 35 Ma 80-Mabase- and precious-metaland tungsten-bearing swann. granite veins in (Shawe et ol. 1984), contains hiib- Fission-track agesdetermined on accessoryzircon nerite, molybdenite,pyrite, multiple generationsof and apatite from pyrite-bearinggranite collectednear covellite, bismuthinite, and ourayite, all as fillings the quartz veins are about 43-44 Ma and 20 Ma, of vugs and fractures in mosaic-textured to druiv respectively (Shaweet ql. 1986).The agesare inter- MINERALIZATION IN GOLD DISTRICTS, NEVADA 359 preted to reflect partial annealing of zircon during gue minerals along with qrrartz. Anglesite is a emplacementof the 35 Ma dykes, and annealing of weathering product of galena. Addition of sulfides apitite probably during both the 35 Ma event and to the vein, and alteration of hiibnerite to scheelite, during the 25 Ma mineralization at nearby Round are thought to have occurred during a younger Mountain, followed by slow cooling to about Z) Ma (35 Ma?) event following the initial (80 Ma) episode at which time apatite had passedthroueh the anneal- of hiibnerite-bearing quartz vein mineralization ing threshold. Remineralization of the quartz veins (Shawe et al. 1984). may have occurred during either or both of these events. Prospect north of Mariposa Canyon A prospectpit about 1.5 km north of Mariposa The Shale Pit Canyon and 6.5 km south of Round Mountain The Shale Pit is a small gold mine in Ordovician eiposes a quartz vein, in granite, that strikes Nl5"E carbonaceous argillite and limestone about 3 km and dips steeply west. A similar parallel vein lies l0 south of the Round Mountain gold-silver mine. Gold m westof the pit. The veinspinch and swellto a max- mineralization occurred mostly in argillite just below imum thicknessof about 0.5 m. They consist of a thrust fault that placeslimestone above the argil- mostly massive white quartz, but in places much lite. Yery fine-grained gold is disseminatedin silici- vuggy quartz is evident. In one place a central frac- fied argillite where iron oxides (altered from pyrite) ture in the white massive quartz vein is lined with are abundant. Anomalous amounts of arsenic, late vuggy quaftz. Somevugs are lined or filled with antimony, mercury, and silver, along with otler chalcedony (Shawe et al. 1984, Fig. 25). metals, suggest a kinship with Carlin-type gold The veins contains sparsehtbnerite embeddedin deposits. massive quartz. Abundant sphalerite and lesser At the ShalePit a pod of milky-white quartz about amounts of pyrite, galena, tetrahedrite-tennantite, 2 m long occurs in strongly deformed silicified and and pyrrhotite(?) are concentratedin vugs in quafiz, iron-mineralized argillite about 3-5 m below the or are strung out in quartz closeto or in prominent thrust fault that forms the sole of overlying lime- shears in the veins. The sphalerite contains tiny stone. The pod contains abundant massesofgalena exsolved blebs of chalcopyrite (Shawe et at. 1984, several cm long, interconnected by numerous thin Fie, Zl). Chalcedonylocally veins broken sphalerite anastomosingveinlets of galena.The galenadisplays crystals, and a late stageof quartz-chalcedony filled somewhat curved cleavagesurfaces. Thin veinlets in some vugs lined with quartz and pyrite crystals galena that are filled with cerussite contain sparse (Shawe et ol. L984, Figs. 24,25). Tetrahedrite- tiny grains of arsenopyrite. The quartz mass is tennantite, paragenetically younger than the early strongly shearedand fractured, and locally it con- sulfides, shows late-stage alteration to chalcocite, tains vugs lined with drusy quartz. The milky-white acanthite, stromeyerite, covellite, and stibiconite(?) quartz of the pod appearstypical of that in the 80 (shawe et al. l9M, Fig. 28). Ma veins; the drusy quartz is typicat of the Tertiary A quartz vein, which is in granite and is similar gold-bearing deposits in tle southern Toquima to the two veins at the prospect north of Mariposa Range. Canyon and about 2.2 lm to the northwest, and another one about 0.9 km to the north, have been respectively.Another quartz Prospect near the head of Kelsey Canyon dated as 78 and 79 Ma, vein 0.5 km to the northwest, dated as 83 Ma, was A prospect shaft 5 km southeastof Round Moun- sheared, brecciated, and remineralized in Tertiary tain near the head of KelseyCanyon expos€sa quartz time with chalcedony, barite, and cinnabar (data vein, in granite, t,'lpical of the 80 Ma group of veins. from Shawe et al. D$A. The vein, of undetermined thickness, strikes north- Yein material con- east and dips steeply southeast. Prospects north of White CaPs mine sists of massivemilky-white quartz, but with locally abundant vugs into which less-milky quartz crystals Prospects 0.7 km north-northeast of the White extend. Caps mine eastof Manhattan exposea set of quartz Hiibnerite occursas isolated crystalsin quartz and veins in Ordovician limestone on the south flank of is partly altered to scheelite. Pyrite, galena, covel- Salisbury Peak. The veins are witlin about 3fi) m lite, and tetrahedrite are seenmainly as vug fillings of the south margin of the Manhattan caldera, and in quartz, and in inegular pocketsformed in sheared they lie about 3 km norttr of a Cretaceousgranite quartz. Covellite forms irrqular replacementpatches pluton, referred to as the gpanite of Pipe Spring and fills cleavagesalong crystallographic planes in (ShawelgSlb). Thin veins of white bull quartz a few galena (Shaweet ol. l98y', Fig. 2O, and tetrahedrite crn to perhapsI m wide, generallynortheast-trending is molded around pyrite and galena crystals. Mus- and steeplydipping, occur wherelimestone is jasper- covite, barite, and fluorite occur as additional gan- ized, calcsilicated, and iron-mineralized. Quartz is 360 THE CANADIAN MINERALOGIST mostly massiveand mosaic-textured,though locally irregular quartz veins in quartzite ofthe Ordovician it is wggy. The quartz veins commonty exiriUit ttrin Toquima Formation. The veins are about 2 km selvages of muscovite, and in placespotassium feld- southwest of the margin of the Manhattan caldera spar occurs with muscovite in vein selvagesand and about 4 km northwest of the main mass of the extendsinto the coresof veins,forming a rock simi_ graniteof Pipe Spring(Shawe l98lb) south of Man- lar -to .pegmatite. Locally a few light-brown_ hattan. weathering clots of calcite, no more than icm across, Silver- and bismuth-bearing galena occurs in and thin fracture fillings of calcite can be seen in quartz as well as in small (l cm) massesalong poorly white quartz. pb- Sparse,small tabular massesof defined inegular fractures in quartzite. Galenais the Bi-Agsulfosalts along with minor chalcopyriteand only sulfide mineral identified at this occurrence, galenobismutite occur in shearedquartz. tiiimitell;, although limonite in someof the vein material sug- bismutite(?), or daubreeite-bismoclite(?)are altera_ geststhe presenceof pyrite at deeperlevels where tion products of the sulfosalts. the rock hasnot beenweathered. Cerussite is an alter- The quartz veins at the prospects nofih of the ation product of galena. White Capsmine are typical of veins associatedwith The Greenfieldclaim liesabout I km south of the the granite plutons, though they show evidenceof east-trendingManhattan belt of gold mineralization, remineralization with complex sulfosalts. Similar and about 2 km west ofthe principal gold-producing quartz veinsnearby havebeen dated at about 75 Ma. zone on Gold Hill. Muscovite in quartz-mineralized AIso, quartz the veins at the prospectslie within a rock at Gold Hill hasbeen dated 75 noftheast-trending as Ma, whereas zone of Tertiary mercury miner_ adularia associatedwith gold at the samelocality has alization centeredon the White Caps mini. an age of 16 Ma (Shaweet al. 1986't.

Greenfield claim Outlaw prospect Shallow prospect pits at the Greenfieldclaim about The Outlaw prospect,long known (Shannon1924, 2 km west-southwestof Manhattan expose thin Nuffield 1953,1954, 195, Karup-M gller lTl2, 1977,

TABLE 1. SEUIq'AITITATXVE B'IXSSIOI{-SPECTSOCRAPHXCDATA FOi CALEIIA AI{D PbS.. SIT'PI,SS FRot{rBE RouItDr.toul{TAlr AND MAr{rurtAr coLD DrsrRrcrs, r{!E courfry, rwAoe. ""

Falf- Load-Sl.lyer Shale Prospeot, Prospeot Oson- vlew KlnS pposp. ptt Looalltv - head of north of fletd nlne Kelsey ItaPl,pos olaln _- Ceyon Csyon sarple DRS DRS- DRS- DiS- DSlt_ DRS_ DRS- Dns- DBI'_ 74- 79- ?8- '14' 'l\- nu-uer !l-: ,122 74- 74' 80- 224 42a 1g 221 219 252a 252b \g pbses pbsse pbs pbsss pbg pbs pbsss pbsss pbsss Fe .t50 2000 1500 3000 r50 30 50 <10 70 u8 <50 <10 <10 <10 <10 100 <10 <10 .10 Ca 100 30 5r >2t .03t 1,51 O.3' 0.3t 1.5, 2$ >2' cd t{10 150 150 150 m0 x10 300 't0 r50 qo N10 l{10 il10 Il0 rtto t{10 lt10 l{10 150

crl x10 L10 ltl 0 r{10 t{l 0 t{l 0 l{10 llt 0 cu 3ooo 10 20 50 11 1.5' 1.5t 1.5' 700 f,l r10 MO MO xt0 !110 [10 !t10 nlo 15 lto 3000 x5 l{5 il5 x5x577N5 Pb !l UM t{ MUilnil sb 7000 lrl0o 15oO 3000 ?00 200 7000 n100 1100 sn 70 [10 20 l{10 grl{530t5 l{10 l{10 [10 50 t50 15 10 5X550 vl{t{t r{N 30[30 st 3, <10 <10 tru 3000 5000 1.5' 1500 'r 3000 A1 lO <.10 <10 <20 150 3000 0 <10 <,10 t{a l{500 $00 r5OO $00 x500 x500 n500 200 [500 llotes: N not deisoted a! ltnit, of.dotsrnlnatlon. !f liaJor. HlBh Cu va1ue6 ln saEplos DRL-74-?2|, DnS-74-219, 7\-252a 8d, DRS-74-252bar€ due io adrl;ed oovelltte. nfeil Sr Elues ln ihese s&e four mplga plus DRS-gO-qgand DRS-?3-229ane due to qq"!l:,!. adnlxei u. Conklln, ealys!.. Htgh yaluos of Fo 1n mtteo DRS-?3-2?8, DRS_f4_1tl2a, and-Dis-79-18 ' aro due to pJrlie (or moastte, on !otn) mnt ot6ttoa; htih yalue of l{o tn-mplo DBS-73-aaBls due to dolyb

Hanis & Chen 1975, 1976, Karup-Mdller & Limonite is a common alteration product, and angle- Makovicky 1979,Makovicky &'Mummi t929, pun- site and bismoclite-daubreeite(?)are presentas alter- ning et a/. 1988) as a localiiy for rare and complex ation products of aikinite. Minor amounts of bis- pb-ni-a,g-Cu sulfosalts, is in a quartz vein at a ion- mutite, sulfur, and cerussitealso were identified as 1988). tact betieen eranite and schist about 8.5 km alterationproductsof aikinite(Dunning etal. southeastof Round Mountain. The schist,reprsent- ing metamorphosedsedimentary rocks of brdovi- Muscovite from the quartz vein at the-Outlaw cian(t) age, forms a narrow east-trending screen prospect hry uq age of 8l Ma (Shawe et al. 1986)' Uetweenlwo granite plutons (Shawe l98ia). The indicating that it was formed as part of the miner- principal(?) uein is t-Zh *iOe, itrikes northeast,and alization related to the Late Cretaceousgranite plu- iipr tt".piy nonhwest, following an irregular con- tons. However, the prospect lies in an east-trending tact t"tr"'Cn granite and schist. fein quartz is milky belt of Tertiary mercury depositsthat extendsfrom white, generailymosaic-textured, andiocally wggy. south of RoundMountain for more than l0 km east- The vein has Leen much sheared, and commoniy ward (Shawe1986). The leachedpyrite in the deposit shows thin lensesof granite or schist shearedinto and veining of sulfides by sulfosalts suggestthat at the vein margins. Muicovite forms thin selvageson some time following formation -of t!t" base-metal the vein walli, as well as irregular lensesandbleh deposit, additional hydrothermal activity-occured. within quartz. SmAt tourmaline crystals line shears The presenceof tourmaline suggeststhat the miner- in quart locally near tourmaline schist wallrock. alization is related to the 35 Ma igneous episode. Fluorite, pyrite, and rare rutile are intergrown with irregular massesof muscovite within quartz, or they _ l occur as isolatedcrystals in quartz. The pyrite localy MINERALoGIcALDATA is granular to porous (or spongy), giving the appear- anie of having tein ioriiraea ana teiCtred. Resultsofourstudiesareorganizedinthefollow- Sphalerite,galeni, molybdenite, and severalPb-Bi- ing pageson the basisof mineral speciesagd groups. Ag-Cu suliosalts occur as euhedral crystals and Material from severallocalities in the Round Moun- in:egular massesin shearedvein quartz, and as fill- tain and Manhattan golddistricts provided data on ings in vugs in quartz. The pyrite, iphalerite, galena, galena, galeaasolid-solution (PbSJ' and other sul- anO motylaeniie commoniy are fractured, and the fides specifically associatedwith the galena, on bis- fracturei filed with sulfosalts. According to Shan- muthinite, galenobismutite, and berryile(?), on non (l9Z) chalcopyrite fills thin veidJts in ben- lillianite-gustavite and on tetrahedrite-tennantite. jaminite. A late gineration of Hg-bearing Pb-Bi- The Outlaw prospect near Round Moudtain is dis- Ag-Cu sulfosaltJ and coloradoite is also present. cussedseparately in considerable detail becauseof

FRoU TABLE 2. ELECTBOI]|ICBOPnOBE DAIA FOB CoExrglxrc cALEllAs, Pbsss' Al{D ouBAYrrE rflo RormDMolrNTAr[ - MAMtlrra[ AREA, [rE CO.' TSVADA.

L9ad Prospeot Prosp€ct a,@n-, StIYor shate hqd of north of fleld Lsallty FalrYl€l Blne Klng Pti Kelsoy i{ariPom olatn --999p99!- _ csvon -!4!.9- DRS sampls DBS-?3-228 DnS- DRS- DBS- DBS- D8S- DRS- n*ijn phaas prtaee ptraoo ?4- T9- 78- 7\: 74- 7\' 80- t 2 3 1rl2b 18 122 219 221 252b 49

[o. of eal.6225 potnte

nlo. oraylbe Pbsas Pbgs€ Pbs Pbs PNus PbS Pbs Pbsss Pbsss nano

0.0 0.0 0.0 o.o O,O O.O 0.0 0.0 0.0 0:0 sb 0,9 0.1 0.2 0.1 0.3 0.3 o.o 0.1 0.0 o'l hr 0.0 0.0 0.0 o.o 0.0 0.0 0.0 0.0 0.0 0.1 16.0 1rt.3 1,1.9 13.r1 rg.rr !3.q r3.5 13.3 13.5 13.8 s 81.2 Pb 39.5 ?0.8 56.7 e6.s a6.z 8?.0 87.5 85.5 83.3 1.6 BI 33.3 9.1 18.5 o.2 0.0 0.0 3.1 9.6 4.E 9.4 0.0 0.1 0.5 0.1 o.2 0.9 1.7 0.0 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 AA 0.0 0.0 0.o 0.0 0.0 0i0 0.0 0.0

100'0 ToiaI 99.5 99.1 gg.g 10o.ll 1oo.o 101.4 101.1 99.1 99.3

!lo!o, Mo ed ltg sought ln smple DRS-80-il9 sd foud to be b91ot the deteotlon iirii. s"rpr" ins-25'rza al$ oontalns o.lf se and 0.03, Ie bassd on enlaslon cpeotrographto amlysle. -- trot delenmlnod. r 362 Tlm cANADTANMrNERALocrsr

TASla 3' CorlBrts 0F cttALcoPFrLE8lIt.l8!lrs FoR SELECISDSAT.IPLES TABLE4. COrrEltrS trOi SXLVER, OT OALE}IA. Brst{Ultl, A{D Am!Ol|! Irl CA!,E!II8.

Sa[ple no. Ele@nt oongsnt Bl./Aa nailo (xt.) Itoopeoi (fr@ qu&t. I€ad-Sllver Kl.ng {d localttJ B1 tooallti Shale PIC head of speo. data) proap9ct pfoop€ct KElset Csyon DRS-?9-18 1400 1?o Lqd-S11yef Sarple ,li33i' Dns-?rl Dns-?9 Dns-?8 Dns-?rt Klng P.osp. fi300) (rcne) (2600) !@bor -l 42a -rq -t22 -22'l DnS-?q-142a 6too laooo lroo'. Aa & t020?o tdad-SllYef (300)- Klng Fosp. (--_, (---, lu <10 <0.2 <0.2 <0.4 t--_, BI lllr.z)' eoo(rto)' >o.et(0.:o). rsoo(a3oo). DRS-?q-1!2b (200) (<200) (800) cd roo(150)r 1oo(l5o)+ r5o(r5o), l€ad-St1Y9r 15@ 700 4(f,)i Ktng Prosp. sb 3oo (r)r rrl0o(1500)r >0.2f(0.3)r {oo(?oo). Dns-?8-122 TE 20 15 300 1oo 52OO 5600 3OOO*-- Shale Plt ( >2000) u\ <20([) r 6(n)r roo(r)t qo(11)r (5roo) (3300) (2600)

5.940

5.930

5.920 \{€------o 5.910 -\

3 4 5 6 7 wt.% EAg+Bi+Sb Ftc. 3. Relation of a versassummation of sb+Ag+Bi for galenafrom the Round - Mountain Manhanan area (1, DRS-74-142b;2, T9-lg; 3, 7L219; 4,7g_l?2; 5, 7L221; 6, 74-142a;7 , 74-252b;8, 14-252a;9, 8G49). Solid circle, ty etectron_ 'nicroprobe; open circle, by quantitative emission spectrography. An'additional data p-oint--(fromKarup Mdller &"Makovicky lggl), is sh-own * op.n lri*_ gle. AII cell dimensionsr0.0o2 A. Micropiobe data arc r0.4"r $.g;. MINERALIZATION IN GOLD DISTRICTS, NEVADA 363 minor-element contents. Discrete coexisting galena antimony contents in galena samples(Fig. 3). Data and PbSo with different compositions have been from the literature are included for comparison. identified from two localities (Lead-Silver King Fieure 4 showns the compositions determined by prospect and Fairview mine dump) and probably electronmicroprobe and plotted along the galena- exist elsewhereas well @oord et al. 1985).Tellurium matildite join. It can been seen on this figure that and seleniumsubstitution for sulfur in galena(altaite some of the points show a slight excessin bismuth. and clausthalitecomponents, respectively) was deter- This phenomenonsuggested to Karup-Mdller (1977) mined to be nearly nil. Resultsof spectrographicand that the Bi-excessin galena may be due to domain- electron-microprobe analysesare given in Tables I type structuressimilar to those in the lillianite homo- and 2, respectively. Concentrations of chalcophile logues. elementsare shown in Table 3; those.of silver, bis- Becauseof the extremelysmall amount of PbSo muth, and antimony in selectedgalena samplesare and associatedsulfides and sulfosalts collected from given in Table 4. the Fairview mine dump, all data (X-ray, emission Back-scattered electron @SE) imaging of the spectrographic and microprobe) could not be galena from the Greenfield Claim (DRS-8049) obtained on exactly the same grain or grains of showedhomogeneous-appearing galena, an unusual material. A 114-mmdiameter Gandolfi X-ray pat- property for galena with such high content of bis- tern made from a somewhatbrittle silvery-white sul- muth and silver. fide or sulfosalt associatedwith visible molybdenite An almost linear correlation may be seenbetween and quartz in veins within hydrothermally altered the a cell edgeand the sum of silver, bismuth, and eranite (sampleDRS-73-228, Fairview mine) shows

Bi(sb)

(1981

Ag(Gu,Hg) Pb Frc. 4. Triangular plot in terms of Pb, Bi(Sb), and AeGu,Hd, showing the com- positions (atomic) of galena and associatedsulfosalts from the Round Mountarn - Manhattan area. Selecteddata from the literature are also shown. Symbols:open circle, known minerals and ideal compositions; solid circle, samplesfrom Round Mountain and Manhattan; open square,Karup Mdller (1977);open triangle, Fina- slir et al. (1981),Herbert & Mumme (1981); +, phaseX; solid square' phase Y; b, bismuthinite; u, ustarasite;ip, ideal pavonite; ib, ideal benjaminite; ub' unsub- stituted benjaminite; k, kitaibelite; gb, galenobismutite;gu, gustavite; abh, Ag-Bi heyrovskyite; mu, mummeite; cp, cupropavonite; o1qo,ourayiteljgi op, P

lines that could be indexed on two discrete galena- of two minerals, it was realized that one of the type cells. However, after the discovery of an galenas was ourayite. Additional X-ray powder- ggrante composition (Ours) as well as that of diffraction studies of material from the prepared PbS"" by microprobe analysis of additional polished section also indicated the presence of material, and BSE imaging indicated an intergrowth ourayite. The X-ray-diffraction pattern of ourayite

Ftc. 5. Back-Scattered Electron (BSE) photograph of Gal66-Mat4q(medium grey) and host pyrite (white) from the Fairview mine, Round Mountain, Nevada. Samprc Off,S-ZlZi6. Ftc. 6. BSE, and elementdot.maps for an aggregateof minerals in sample DRS-73-228(Fairview mine). (a) BSE image: pyrite' black cube; ourayite(?), dark grey; PbS* light grey. (b) PbMa dot map, sameare{l ag on 6a. (c) BiMcv dot map' same area as 6a and 6b. (d) BSE image: pyrite, black; ourayite(?), medium grey; PbSo, light grey. (e) AgZcu dot map, same area as 6d. MINERALIZATION IN GOLD DISTRICTS, NEVADA 365

(Karup-Mdller 1977, Makovicky & Karup-Mdller Bismuthinite, galenobismutite, gustavite, 1984) is simil4l to that of galena, owing to the and berryite(?) presence galena-type of dominantly layers with rela- A lead-bearingbismuthinite was identified in one tively few bismuthinite-type layers. Single-crystal sample(DRS-81-201c), collected from the Fairview will necessaryto confirm.whether the studies be mine dump south of Round Mountain @ig. l). The (Makovicky ourayite is 3-centered or P-centered & grey, metallic bismuthinite is associatedwith quartz Karup-Mdller 1984) or if it is another mineral spe- and pyrite. A six-step semiquantitative emission- cies having a value of N equal to ll. A lillianite spectrographic analysis (by NMC) showed: Fe homologue can be characterizedby the number of 0.1590,Mg <10 ppm, Ca (20 ppm, Ag 70 ppm' (N) octahedra in the octahedralchains in eachof two Bi major, Cu 0.790,Nb 15ppm, Pb 2t/0,Sb 0.390' typesof layersMakovicky & Karup-Mdller lW7 a,b). Zr 20 ppm, Si 0.390, and Al < l0 ppm. Other ele- On the basis of electron-microprobe analyses and ments were not detectedat their respectivelimits of galena-typephases (phases SEM studies, two 2 and determination. Chalcophileelements were also deter- phase 3) were found along with a dominant third mined (by C. Heropoulos, USGS) for the sample (phasel) compositionallymost closelylsgsrnuing with the following results (in ppm): As 1()0' Au ourayite. X-ray-diffraction studies of this material <0.3, Bi > 1000,Cd 4, Sb 200, Te 200' Zn 26, P phases galena, identified I and 2 as ourayite and <1, Tl <1, Hg <1, Se 1300. phase respectively. An insufficient amount of 3 An average of six electron-microprobe analyses present (highest Ag- and Bi-containing galena) was gave:Bi 79.22wt.r/0,Pb2.23,S 18.47,total99.92. for detection by X-ray diffraction. However, care- A structural formula calculated on the basis of two phase (CafuMatao) ful examination of 3 at high cations is (Bi,.nrPbo.or)S2.e5,or if calculatedon the magnification using SEM BSE imaging techniques basisof 3 sulfur atoms is (Bi1.e7Pb0.06)Sr.This bis- showedno tracesof any other intergrown or exsolved mineral phase(Fig. 5). Annealing studies of two samples of the hand- picked fragments selectedfor spectrographicanaly- sis, and which were initially determined to have two galena-typephases present (subsequentlyidentified as an intergrowth of galena and ourayite), when heated at 5ffioC in vacuo for 1 week produced material that gave a sharper single galena-typepat- tern along with a faint pattern for ourayite. We con- clude that the untreated sample contained, in addi- tion to ourayite(?), two discrete compositions of galena, both of which contain abundant matildite in solid-solution (PbSJ. Upon heating, the two different compositionsof galenawere homogenized, and the ourayite-like mineral was converted to the artificial equivalent of ourayite sensu stricto. Figures 6a to G show BSE and selected-element dot maps for phasesI (Our53)and 2 (Gal*Mat2') in DRS-73-228from the Fairview dump (Fig. l). Simul- taneoussrystallization of ourayite, PbSo, and pyrite !E]E :r*S seemsindicated; compositional boundaries between :rfrii:ii Si.i:l *:$ @-; 'b, different minerals are sharp and no exsolution-type S. rb:1 textures are visible. Phase 3 (GaleoMat*) is totally enclosed within a grain of pyrite @ig. 5). An emission-spectrographic analysis of hand- picked fragments yielded the composition for DRS- 73-228 eiverr in Table 1. Three thousand ppm molybdenum are present, indicating somewhat less than 190 molybdenite contamination. X-ray- -'*i;il .& diffraction studies confirm the presenceof minor Frc. 7a. BSE photograph of intergrowth of gustavite, laths amounts of 3R molybdenite and quaxtz. Three dis- of bismuthinite and sparse patches of alteration tinct sulfide and sulfosalt phasesin addition to pyrite products, prospectnorth of the White Capsmine @RS- (Iable 2, Fig. 4) were determinedto be presentbased 8G56). white, bismuthinite; light gey, gustavite; dark on optical and electrou-microprobe studies. grey, galena. 7b. BSE closeup-photograph of 7a. 366 THE CANADIAN MINERALOCIST

muthinite is similar in compositionto othersreported An averageof three microprobe analysesof the in the literature @ig. 4). BSEphotographs show the galenobismutitegave: Cu 0.2, Sb 0.1, S l?.1, pb bismuthinite to be monomineralic. 27.5, Bi 56.2, total 101.I wt. 90. Zinc, arsenic,ilon, One polishedsection (DRS-80-56) of vein quarrz and silver were sought but were found to be below from one of the prospectsnorth of the White Caps the limits of detection. This material is normal pb-Bi-Ag-Cu_Sb mine contains an intergrowth of galenobismutite; its composition is plotted on sulfosalts; X-ray, spectrographic, and ilectron- Figure 4. microprobe analysesshow theseto consist chieflv of An averageof six electron-microprobeanalyses of bismuthinite, galenobismutite,and gustavite with the bismuthinitegave: Bi 80.63,Pb 1.45,S 18.42, lesseramounts of berryite(?).Cerussite, bismutire, total 100.50wt.9o. A calculatedstructural formula bismite, and other alteration products are also basedon 3 S atoms is: (Bir.efb6.srS3. present. BSE-imaging and EDS analysisof the finer The gustavite matrix enclosing laths of bis- grained part of the intergrowth show the presence muthinite is uniform in appearance images)and of gustavite @SE major enclosingrandomly oriented laths is homogeneousin composition.An averageof six of bismuthinite and scattered, extremely small microprobe analysesis given in Table 6. anhedral blebs, patches and veinlets of alieration A fourth mineral, which may be berryite, is products within the gustavite @ig. 7a). The bis_ associated with the gustavite, bismuthinite, and muthinite laths are 5-10 pm long and 2-3 p m wide. galenobismutitein DRS-8G56.The chemicalformula AJteration patches of cerussiteand/or angiesite,and of berryite still is uncertain, and the extent of solid- Bibearing minerals are typically 2 pm aCross@gs. solution betweencopper and silver end-membersis 7a,b). Another part of the samepolished section con_ variable. An electron-microprobe analysis of one tains a coarser grained (50-100 pm across) inter- grain of the berryite(?)gave: Cu 5.11, Sb 0.86, grofih S of euhedral crystals of bismuthinite and 16.55, Pb 24.61, Bi 42.32, Ag 10.09, total galenobismutite without guslavite. A six_step 99.54 wt.t/o. Zinc, arsenic,and iron were sought but emission-spectrographic analysis(NMC) of the mix_ not detected.If the data are recaston the basisof ture_qlve: Fe 700 ppm, Mg l0 ppm, Ca 200 ppm, 16 S atoms, the formula is: Pbr.r(Agr.oCuz.o) Ag2Vo,Ba200 ppm, Be2 ppm, Di >l0go, CIIOO (Bi6.4Sb0JSr6;on the basisof ll S atoms, the for- ppm, pb !pT: 90 ? Cu 1.590,Ni 7 ppm, >l0go, mula is: Pbr.6(Ag2.oCu1.8XBi4.4Sb0.rS,,.If the Sb ppm, 5000 Si 1.590,and Al < l0ppm. Other ele- mineral is berryite then someminor substitutionof msnts were not detectedat their respectivelimits of antimony for bismuth is likely. No X-ray-diffraction determination(Table 5). The Si is fiom quartz con- studieson pure material were done becauseof the tamination. Chalcophile elementsdetermined spec_ small grain-size. A Gandolfi film for a sample of trographicallyby C. Heropoulos, USGS, are: As-560 bulk material showed major bismuthinite, lesser g!g, Au <1.6 ppm, Bi )lgo, Cd 4m ppm, Sb galenobismutite and gustavite, plus additional faint 1600ppm,-Te p 240 ppm, Zn 80 ppm, < l-ppm, Tl linesthat are closeto thoseof berryite. The compo- 16 ppm, ppm, Hg 15 Se Z@ ppm. sition of the probe-analyzedberryite(?) material is shown on Figure 4. Ideal benyite is also plotted on the Figure. IABLE 5. .APPTOXIMAIE LOXER LII,lIlS OF DET8ft{1I,IATIOI{ FOE EL&,I8I{TS Other analyzed samples (Nuffield & DETERI,III{EDB1 6.SISP SPSCTBOOMPMCUEIIIOD (IIi PETCEI{TAtrD PPM) Harris 1966,Karup-Mdller 1966, 1917,Borodayev sl 0.002t 5 pp! qr c nnh &Mozgova 1971,Harris & Owens1973) are shown AI ,001 cd 50 so 100 on Figure 8. Berryite is phase .001 G€ 10 ta 200 the only that is close Ms ,002 Hf 100 Tb 200 in composition to our analyzed material. .002 go 20 !e 2000

Ne ,05, 1n 10 ppq th 200 ppn ,7 IN 50 TABT.E6. ELECTRONMICROPROBE OATA FOB LILLIAIITTE IITD T1 .0002 3O to 20 cuslAyrlE FRox UAInATTAI, lrBgApA .2 50 u 500 Un .0001 LU 30 t7 Dffr-8o-55A Dns-80-56 Ll11lutta Custaylis A8 !{o 3 ppo r 100 pp! A8 1000 l{b 10 Arera8s of AYoragg of Au 20 l{d T 2o lll, Zr\ 200 BA 09 50 Zr 100 0.0 sb .3 B9 1 ppD Pb 10 ppo 16.3 16.45 Bi Pd Pb \2.3 31.9 ?0 PT 'I00 150 Pt 30 Bi 39,2 47.8 Co Re 30 18 AS 0.1 -?:o 'I ppn Cr Rh 2 ppm TO o,2 .1 Cu l Ru 10 Dt 50 sb Toial 100.4 I 02.05 Br 50 Sc 8u r00 Sn 10 lotor Zn ed Fe s@ght but noi degeoted. --- not dgiernlned. MINERALIZATION IN COLD DISTRICTS, NEVADA 367

Lil lianit e- gustav it e series ing the nomenclatureof Makovicky & Karup-Mdller (1977a,b).The calculatedN..* is equal to 3.99. Studies of members of the lillianite-gustavite The gustavite from DRS-80-56has an averagecom- (Pb3Bi2S6- PbAgBi3S) series(e.9., Nedachi e/ d/. position of L3eGus61and appearsto be composi- 1973,Makovicky & Karup-Mdller 1977b,Finashin tionally homogeneous(Table 6). et al. I98l) have indicated a solid-solution series As stated by Makovicky & Karup-Mdller (1977b), between the two minerals vrith a miscibility gap in natural phasesbelonging to the lillimils-gu51ayi1g the seriesbetween about Gusr6and Gus65. series, PbrBirS6 - PbAgBi3S6,&re- homogeneous Blades of lillianite enclosed in quartz comprise between Gus,* and Gusr, (the 8-A phases)and sampleDRS-80-55a from oneof the prospectsnorth again between Gusrs and Guse (the 4-A phases; of the White Caps mine. An average of seven e.9., Ontoyev et al. 1982).High-temperature phases microprobe analysesis shown in Table 6. Five with compositions situated in the compositional gap 114mm Gandolfi X-ray-diffraction films of the lil- show exsolution phenomena. The lillianite in DRS- lianite in DRS-80-55ashowed the material to be 8G55ais homogeneousand representslower temper- mostly rilli4aile, with a trace of galena.The galena aturesof crystallizationthar the crestof the solvus. was not found during the microprobe analysesof the Becausethe gustavitein sampleDRS-80-56 appears lillianite. The lillianite in DRS-80-55aranges in com- homogeneous(BSE imaging) even at high magnifi- position from LTaGuq6to L76Gus2(Fig. 4), follow- cation (2000x ), it may have cooled rapidly enough

p e un e

glo

I e oko r.rd h9' 8t AA: nuo r{ on" , 6@a

Frc. 8. Triangular plot in terms of Cu(Ag), Pb, arid BilSDl showing the composi- tions (atomic) of aikinite-bismuthinite series minerals and others. Solid circle' compositions of minerals from Round Mountain - Manhattan; plus sign' average of cornposidonsof sevensamples from the Outlaw prosp€ct;open circle with cross' aikinite-bismuthinite series; open circle, ot[er natural minerals; open triangle, unknown structure; open square, Karup Mdller (1977);b, bismuthinite; p, pek- oite; u, ustarasite;un, unnamed;gl, gladite; r, rezbanyite;n, nordstromite; j' junoite; k, krupkaite; gb, galenobismutite;pa, paderaite;ho, hodrushite; cb' cuprobismutite; e, ernplectite; l, lindstrdmite; ip, ideal paderaite; h, hammarite; ber, berryite; ko, kobellite; pr, proudite; c, cannizarite;co, cosalite;bur(?)' bur- saite; lil, lillianite; xil, xilingoiie; bon(?), bonchevite; hey, heyrovskyite; asc, aschamalmite;g, galena;w, wittichenite; la, larosite; cc, chalcocite;f, friedrichite; s, soucekite;a, aikinite; nu, nuffieldite; ne, neyite; solid squares,giessenite. Bonche- vite and bursaite are inadequately'described minerals. 368 THE CANADIAN MINERALOGIST

TABLE 7. CIIALCOPIIILEELEMEIIT CONCEITRITIONS IN TIIREE microprobe. SAI,IPLESOF TE'IRAHSDRIIEF'ROU TNE BOUND!,IOIJI{TAIN AREA The maximum amount of silver deter- mined by electron-microprobeanalysis to be present Dns-?8-l Dns-78-2 DnS-?q-243 in any of the six examined tetrahedrite-tennantite SffpLs nos. (Fon rboauronsrc shaweeu afllSSIT- samples from the Round Mountain - Manhattan Elonant area is about 390. AS >2000 >2000 700 Au 0.5 <0.2 Bt 200 >l 000 >1000 >1000 Sulfusolts and suffides from the Outlaw prospect, sb >2000 >2000 >2000 northeast of Manhotton 100 t00 100 Table 8 is a summary of minerals identified from Za >200 >200 >200 <1 <1 this prospect.Despite the complexityand degreeof T1 <1

Qustz 1,2, 5, 11 OM 11 krupkaite-type, and aikinite-type structural ribbons Fluoflt€ 1, 2, 11 Bl-PtsFg-A8-tu (Kostov & Minleva-Stefanova 1982).Various mem- Ieortb 1,2, lt stfd8 I bersof the series,e.g., pekoiteand hammarite,may lor@l lne t 1 (Pb@ x) tutlle 11 U@ 11 be seleniferous (e.g., Mumme & Watts 1976, Prrle 1, 11, 12 Br-Pbng:&-Cu Kovalenkerel al. 1984,Chekalova & Slyusarev1974). Chal@yftb 1, 2, 3, 5,6, 9, 11, 12 olfodl 2 Aikinite. In this study, aikinite and possibly tul@tb 1, 12 (tu i) &rolltb 6, 12 &lof&1te 11. 12 friedrichite(?) were identified from sevendifferent bltxontle 1, 1t c4@1b to, lt,12 samples from the Outlaw prospect. Electron- SPhalerllo 10 Anglestt€ 10, 11, 12 microprobe data on the aikinite and friedrichite(?) Glem 11 Bl@lrr 10, 11, t2 Arthtb 1.2, \, 5! 11, 12 tuube1t6 in all of thesesamples are given in Table 9. The com- hJelnlte 1, 2, 3, 4, 6, 7, 8, 9 al@tlh 12 positions given in Table 9 and the average(of 7 sam- htl& 2, 6, 7, 8 tul@hlb 12 ples) are plotted on Figure 8. Whereas some of the kt1ldt& 2, 7 hk1!e 72 analytical points cluster around ideal LldEtrod& 2,9 E€rrhtydi6 12 friedrichite @b Bl@lhtnlb 4 0o€h1& 12 30.5,Bi 43.1,Cu9.4, S 17.0wt.9o), and other points Mrlb 6, l, 11 Jf@lb 12 are closer to ideal friedrichite than to ideal aikinite trqpbller. 7,8, 9, 12 xoslblb 12 (Pb 36.0, Bi 36.3, Cu 11.0,S 16.7wt.9o), single- tubrlb 7, 8, 9, 12 $lfa 12 rr crystal precession-camerastudies (of DRS-79-84a) @p6lLlo s EtEn t6 MD ol ll!'@lb rah€f tu hDdb. (19?I), (2) xfflerd(1953), (3) bnFutr+ (112), Fl"I"l9:"--(4) (1975),!1)-q"',1"1 (5) confirmed that some material is nonstoichiometric Xufflerd ht6 a tun (r9?5), (5) brls & cilen t1976).'' t7)' hrFbtlr (r9?7), (8) Hovloky & @ (l97g), (9) kutsrrrbr & aikinitewirh 4 ll.3l(l), , ll.6t(l), c 4.02Q)A. !,t:!9v,loky(19?9), 00) S. A..rllrt@, p6. @., r98r, (it) mrs sUay, (12) MIG gq *, (ln pros+ Figure 9 is a photograph of a kinked (twinned) sin- MINERALIZATION IN GOLD DISTRICTS, NEVADA 369 gle crystal of aikinite (DRS-79-8zla)elongared on c and striated parallel to [c]. Reddish brown internal reflections are presentin oblique incident light. Our investigation showed only aikinite, friedrichite(?), and hammarite to be presentas representativeof the aikinite-bisrnuthinite series.Other investigatorshave reported lindstrOmite, krupkaite, and bismuthinite as well (Table 8). The composition of krupkaite (averageof sevenpoints) reported by Karup-Mdller (1977)and Karup-Mdller& Makovicky (1979)is just about identical to that reported by Harris & Chen (1976)as hammarite.Compositionally, the average of the sevenpoints plots close to ideal hammarite and is quite removed from ideal krupkaite. One specimen of material labelled Frc. 9. Photographof kinked,elongate, striated crystal of @C-Benj) "ben- quartz the Outlawprospect (DRS-79- jaminite, Outlaw Mine, Mariposa Canyon, Nye Co., aikinite in from 84a),Mariposa Canyon, Toquima Range, Nevada. Scale Nev." was obtained from F. Cureton. This sample divisionsare I mm. was collectedin the 1920sfrom the Outlaw prospect. As viewed megascopically,the specimenconsists of milky quartz containing muscovite, molybdenite, Tl (emission-spectrographicdetermination of chal- pyrite, and a bronze-tarnishing sulfosalt. Examina- cophile elementsby C. Heropoulos, USGS). Six-step tion of the sulfosalt by electron microprobe showed semiquantitative emission-spectrographic analysis the presence of a member of the aikinite- (NMC) of another split of this sampleshowed: Fe bismuthinite serieshaving a composition nearly iden- 0.1590,Ag 3000ppm, Ba 15 ppm, Bi major, Cu tical to that of ideal friedrichite (Table 9, Fig. 8). major, Pb major, Cr 7 ppm, Ni 10 ppm, Mo 500 The mineral, however, may be nonstoichiometric ppm, Sb 7@ ppm, and 1.590Si. No other elements aikinite, as was found in some of the other samples were detected. examined in this study (Table 9, Fig. 8). One com- What is most likely aikinite, with a slight excess position (Table 9, Fig. 8) lies midway between of bismuth, is presentin DRS-8G38a(prospect 2 km friedrichite and hammarite, which is probably a non- southeast of Round Mountain; Table 9) associated stoichiometric hammarite. One area examined by with sphalerite, pyrite, and quartz. An emission- microprobe contains a 20-pm-wide veinlet of a spectrographicanalysis (NMC) of the aikinite(?) that mercury-bearing Bi-Pb-Ag-Cu sulfosalt (phaseX), contains minor sphalerite and pyrite shows300 ppm which is most likely a new species.Material of simi- Ag and 3000 ppm Sb. Among the chalcophile ele- lar composition was found in two additional sam- ments (analyst: C. Heropoulos), the samplecontains ples @RS-7343b and DRS-73-43d); additional 50 ppm As, < I ppm Hg, 2 ppm Tl, 70 ppm Te, 700 details are given later. ppm Se, 500 ppm Sb, and < 0.2 PPm Au. The One sample (DRS-7343a) of aikinite from the associatedsphalerite (containing about 490 aikinite) Outlaw prospectcontains 100 ppm As, 150ppm Sb, contarns0.590 Fe, 0.390Mn, 1.590Cd' 50 ppm Iq 200 ppm Se, 50 ppm Hg, 100 ppm Te, and 7 ppm and 7 ppm As.

TASI,E9. SLBCTIOIUICROPROBE DA1A FOR AIKII{ITE, FiXBDBICFITE(?)' AnD BA}|UARITEFRolil lHE oufLArPRosPEcT, MARXPOSACIJ{YOII, AllD flt0 PRoSPE0Tsourlt oF RoultD!{ouNtAll{' mquIMA RAXOE' NET!"DA

Avdags of DRS-73 DRS'-73 DRII-79 Fc- DBS-8O o$rl3 DRS-73 DRS-?3 oullac -3ga err.*t, -43o -43d -tr3e -43f -8qa BBIIJ mpre9

l{o. ol (4) (2) polnta 9.q 9.C 8.5 9.f 8.9 9.1 9.5 8,7 9.2 10.2 sb 0.1 0.1 0.1 0.0 0.1 0.1 0.r 0.1 0.ll s 16.',t 17.8 16.8 't't .1 12.4 17.4 16.9 17.0 1',|.1 1'1.3 31.8 31,7 29.',1 32.2 3r.5 29.8 28.8 30.6 33.5 B1 42.3 39.2 44.2 38,7 42.5 40.8 S4.o 47.1 42.S 38.C5 A8 0.0 0.0 z\ -9:t -::' -::' -t.0. -;;. -::t -9:t -9:' 0.1 te I.D. rf.D. l{.D. lf.D. .0 .1 0.0 [.D.

fotal 100,3 98.2 99.q 97.9 98.0 99.0 100.4 101.9 99.4 99.95

Xoto! Zn, trg' ed Aa $ughi but no! dsteoled aboYo lln1t of deterBlmtlon ln Outlat pPoopeot'miles. f.D. ' no! deierolned. uo ed tl8 eougtlt bu! oo! foud ln Dls-73-43a' ina ons-rl-4id. Dns-?3-[3a-C3f, DiL-?9-84a' !!-BEl{.t - Out].ar proepoctt DRs-80-38a p!"ospecl south ol Roud Moutatn. 370 THE CANADIAN MINERALOGIST

beendetected at low levels(20 to 50 ppm) by spec- trographic determinationof the chalcophileelements, in samplesof tetrahedrite-tennantite(DRS-78-1, DRS-78-2, DRS 74-243), and in one sample of sphalerite(DRS-74-252a) from sulfide- and sulfosalt- -lnglalized hiibnerite-quartz veins described by shawe et al. (1984).This study also has indicated the presenceof mercury in a sample of sphalerite from the prospect 2 km southeastof Round Mountain (20 ppm, DRS-8G.38a)and in the compositesulfosalt from one of the prospectsnorth of the White Caps mine (15 ppm, DRS-80-5O. Electron-microprobedata for the mercury-bearing sulfosaltin DRS-7343b and DRS-73-43dfor ll ele- ments are given in Table 10. If thesecompositions FIc. 10.BSE photograph of veinlet of unidentifiedHg- (and the average)are plotted on bearingsulfosalt within aikinite. DRS-7343d, a triangular diagram Outlaw Ag(+Cu)-Bi-Pb (Fig. prospect,Mariposa Canyon, Toquima Range, Nevada. 4) adding Hg to rhe Ag r-. Dark greyaikinite host,light greyHg-bearing pb-Bi- Cu corner, they fall very near the Nequals 7 line Ag-Cu sulfosalt. (iy'"h". = 7.16) and lie betweeneskimoite and hey- rovskyite, but are closer to eskimoite. The metal-to- sulfur ratio for phasesalong this line is 0.889.Table Results of electron-microprobe analyses of the I I summarizesdata on phaseslying along this line. aikinite(?) giyen are in Table 9. The averageof the A complete structural formula of phaseX based three data-sets,plotted on Figure 8, lies betweenthe- on 27 sulfur atoms is: (Hg2.rrAg1.aeCur.o:Pbo.:z) oretical aikinite and friedrichite, about l/3 of the (Pb)8.'(Bi,0.7rMoo.*Pbe.qrSbe.0rS27.Single-crystal way from aikinite to friedrichite. No single-crystal studiesof the material will be necessaryto determine X-ray studieswere done on this material; the spe- if it is a mercury-substitutedheyrovskyite, a mercury- cies designationis basedon chemistryonly. substitutedeskimoite, a newmember of the lillianite Hammarite. An electron-microprobe analysis of homologousseries, or a new species. one area in sampleDRS-73-43d (Outlaw prospect) Phose Y (probobly a new Bi-Pb-Hg-Ag-Cu sul- gave a composition very closeto that of hammarite: fosalt). Either a compositional variant of phase X Cu 7.05, Sb 0.22, S 16.74,Pb 26.22,Bi 49.97,Fe (ly' : 7) or, more likely, a new speciesof similar com- 0.10,Mo 0.09,Hg 0.23,totil 100.43@ig. 8). Zinc, position but with Nequal to ll was found in DRS- silver, and arsenicwere sought but not detected.The 7343b. Two microprobe analysesof the mineral results are in agreementwith the findings of Harris gave:Sb 0.02, 0.03; Te 0.04, 0.07; Cu 1.60, l.6l; (1976) & Chen and Karup-Mdller (1972)on ham- Hg 10.13,9.14; S 15.40,15.42;Pb 35.M, 34.71;Bi marite from the Outlaw prospect. 36.79, 36.95; Ag 2.59, 2.43; total 10l.6l, (probably PhaseX a new Bi-Pb-Hg-Cu sut/osott). 100.37wt.9o. Iron, zinc,and arsenicwere looked for Three of the eight polished sectionsexamined from but not detected.These compositions are plotted on the Outlaw prospect(DI{S-73-43b, DRS-7343d, and Figure 4. This mineral forms the bulk of one area FC-Benj) contain a mercury-bearing sulfosalt (about 200 x 200 pm) in the section, and contains mineral, here called phase X. Phase X has been lath-like intergrowthsof phaseX (Table l0), exsolved observedonly as veinletsthat cut nonstoichiometric blebs and irregular masses of galena, and aikinire (in two samples,FC-benj and DRS-73-43d). coloradoite. PhaseY has beenfound in only one sec- The reflectivity and color differencesbetween phase tion thus far, and may possiblybe a mercury- and X and aikinite are very small, but the carbon applied copper-substituted ourayite; single-crystal X-ray- for microprobe analysisenhanced these differences. diffraction studies will be necessaryto completely BSE photographs show the intergrowth of the characterize the mineral. mercury-bearing sulfosalt and aikinite very clearly It seemsclear that a mercury-rich and, to a lesser @ig. l0). The mercury-bearing sulfosalt has veined extent, a silver-bearingmineral assemblagepostdates and replaced the aikinite. The presence of mercury an earlierBi-Pb-Cu-Mo-Fe mineral ?ssemblageat in the sulfosalt was confirmed by wavelength spec- the Outlaw prospect.Phase X occursas veinletsin trometer scans and subsequently by emission- earlier formed minerals but as intergrown laths in spectrographicanalysis (NMC). The presenceof mer- the later generation of mercury-, silver-rich, and cury was noted in the bulk sample of aikinite from copper-poorminerals. the Outlaw prospect (DRS-7343), but not in the aikinite(?) from the prospect 2 km southeastof Coloradoite. Basedon microprobe analyses,very Round Mountain (DRS-8O.38a).Mercury also has minor amounts of coloradoite, HgTe, were identi- MINERALIZATION IN GOLD DISTRICTS, NEVADA 37t fied in sampleDRS-7343b. The rnineral occursas lABla 10. EI.ICTROI UICROPEOBE ANALXSES OF UEBCURY-BE.A8II{G SULTOSALT TROM TIIE OUTUT PROSPECT, IiIARIPOSA CAI|YOI{, TOQUIUA irregular and randomly oriented blebs (grains) as MITOE, I{EVADA y'61hin much as 15 x 20 pm in sizeincluded phase pns-73-43b tj-:-:1 ElsBsnr AYSrago Y. Recently, this mineral also has been identified of 1-3 from the Outlaw prospectby Dunnineet al. (1988). 't.2 Insufficient amounts were available for X-ray- r.3 1.3 '|.5 0.9 1.3 sb 0.3 0.0 0.1 0.1 0.1 0.t diffraction studies. s l5.9 16.0 16.0 15.6 r5.8 r5.8 Pb 29.8 29.3 30.6 32.3 31.8 31.6 Benjaminite. Benjaminite, frst described(Karup- B1 40.3 40,6 \2.',t 39.7 40.5 t10.8 Mdller & Makovicky 1979,Makovicky & Mumme AB 3.4 3.6 2.7 3.1 2.5 2,8 1979)from the Outlaw prospect,was not found dur- l.to 0.0 0.2 0.1 0.1 ing this investigation (Table 8). The existenceof a tls 8.3 8.4 9.0 7.7 7.7 8.1 t9 0.3 0.4 n.d. n.d. n.d. copper- and lead-unsubstituted benjaminite from Australia was described by Herbert & Mumme TotaLs 99,3 99.3 102.0 99.6 99.9 (1981). l{ote, F9, 46, ed Zn saght bul oot dsgected aboye llolis of Golena. Galena, not previously reported from the deterulmllon. n.d., nob deiornlned Outlaw prospect,was found in one sample(DRS- lsE 11. trIJauLs uvnc r - 7 IN Ea 8$m Pb - Bt(sb) - 38(c!)((C) 7343b). Someof this galena,however, rather than &tdrrsdfot having the coupled Ag + Bi = 2Pb substitution, 32136 - O,AA9 appearsto illustrate a Hg(Ag) * Bi = 2Pb coupled Ag7?btOBtt 5336 substitution. Two analyses of an elongate inter- pbe X (sg'Ag'fr'Pb)5PbS(81'rb'8b'b)u827 24127' 0.489 Pb6,Bt2s9 8/9 or 16118- 0,889 erowth of galena in phase Y within DRS-7343b !o Pb19ASB15316 gave:Cu 0.1, 0.1; S 13.3,13.6; Pb 83.9,83.3; Bi, Pb6,81289 8/9 - 0.889 0.9,0.8; Ag 0.45,0.,10; St 0.I, 0.0;Hg 0.l, 0.0;total A€3Pb5,Bt781g(1@ s, htgb A8; l@ ed) 16/18'0.889 98.85, 98.2 wt.9o. No antimony, tellurium, or zinc was detected.The grain shows the normal Ag + Bi molybdenum have not been established. = 2Pb coupled substitution. Two other microprobe A white to creamy microcrystalline crust (altera- analysesof galenafrom the samesample gave: Cu tion coating) on aikinite in DRS-79-84b from the 0.17,0.14;S 13.2,13.9; Pb 76.3,78.9;Bi 4.3,4.9; Outlaw prospect also was examined. A six-step Ag 0.7,0.6;He 5.0, 1.3;totals99.67,99.74wt.0/0. emission-spectrographicanalysis (NMC) of a 3.3 mg A structural formula based on one sulfur atom, bulk samplegave: Fe 0.0590,Mg0.02t/0, Ca0.l0/0, using the average of the two analyses is: Mn 5 ppm, Ag 200 ppm, Ba 500ppm, Bi > 1090, @b6.6sBie.qrHgs.ooAgo.or)S. Cu 500 ppm, La 200 ppm, Mo 30 ppm, Pb 290, Sr Alteration products of sulfides and sulfosalts. 50 ppm, Al < 150ppm. All other elementswere not Identified productsof alteration of galenafrom the detected (Table 5). Transmitted-light and X-ray- Fairview mine material are covellite, anglesite, and diffraction studiesof this material indicate anglesite cerussite.These same minerals are also presentat the and probable bismoclite-daubreeite. Additional other galena-bearing localities examined. alteration products of sulfides and sulfosalts are A mineral(s) that shows low reflectivity, is lisred in Table 8. medium-dark grey in reflected light and light to medium yellow in plane light, occurs as an altera- DISCUSSIoN AND CONCLUSIONS tion product that coats,fills fractures, and is included within galenobismutiteand gustavitein DRS-80-56. In many natural depositsand in synthetic systems Two microprobe analysesshowed: Bi 86.0 and involving lead-bismuth sulfides and sulfosalts, a 86.590and S 0.0 and 0.190,respectively; totals 86.0 generalizedparagenetic sequence has been observed and 86.6 fi.90. No other elementsabove atomic in which lead-rich minerals form prior to bismuth number 9 (F) were detected. This mineral is most rich ones(e.9., Chang& Bever 1973,Czamanske & likely bismite, bismutite, or daubreeite-bismoclite. Hall 1975).Structurally, most bismuth sulfosaltsare An emission-spectrographicanalysis (NMC) of a composed of axial-type structures (Kostov & bismutite-anglesitemixture associatedwith aikinite, Mindeva-Stefanova1982). Furthermore, a trend sphalerite,pyrite, and quartz (DRS-80-38a)gave: existsfrom bismuth to antimony to arsenicsulfosalts FeA.2o/0,Mg 0.0190,Ca 1.590,Mn 5 ppm, Ag with generally decreasingtemperature. Antimonian 700 ppm, Ba200 ppm, Bi )1090, Cd 70 ppm, Cr sulfosaltsare principally of pseudo-isometrictypes, 30 ppm, Cu 1000ppm, Mo 7000ppm, Ni 15 ppm, and arsenian sulfosalts are principally planar types. Pb > 1090,Sb 3000ppm, Sr 100ppm, U 1000pprn, This trend, axial - pseudo-isometris- planar, has V 500ppm, Y 30 ppm, Zn 700ppm, Si 390,A10.390, a definite bearing on the conditions of crystalliza- and Yb 3 ppm.All other elementswere not detected tion of the respectivesulfosalt minerals.The sulfosalt at respectivelimits of determination (Table 5). The minerals tend to separateand crystallizeafter the sul- host(s) of the calcium, uranium, vanadium, and fide mineralsKostov & Mindeva-Stefanova1982). 372 THE CANADIAN MINERALOGIST

However, within the Pb-Bi-Ag-(Cu)-S system, of crystallization from 3@ to 50& m were examined someminerals, such as the crystallizationsequence by Malakhov (1968).He concludedthar the Sb:Bi bismuthinite, galenobismutite,lillianite-gustavite, ratio principally reflects the temperature of crystal- berryite(?), and galena*, which have been inves- lization of the galena.Very low Sb:Bi values(<0.06) tigated in this study, commonly exhibit progressive are characteristic of high-temperature galena (200- lead-enrichment or silver-enrichment (or both) with 300oC and greater), whereashigher Sb:Bi values decreasing temperatur€ (Karup-Mdller 1977). (>6.0 to 13) are typical of low-temperaturegalena Ontoyev et al. (1982) found similar results in their (100-160.c). study of mernbsrsqf ths lillianite-gustavite seriesand Valuesof the Sb:Bi ratio in galenafrom the Round related sulfosalts. Silver- and bismuth-rich sulfosalts Mountain and Manhattan gold districts range from formed earliest, then sulfosalts with a moderare 0.00x to 5 (6-step semiquantitative emission- amount of these elements, and finally at the end, spectrographicanalyses), <0.0m1 to 8 (quantitative galenawith an insignificant content of silver and bis- emission-spectrographic analyses), 0.03 to 7 muth. As stated by Malakhov (1968)and Karup- (chalcophile-elementemission-spectrographic anal- Mdller (1977), bismuth-bearing sulfides are gener- ysis), and from 0.01 to 25 (electron-microprobeanal- ally considered to have crystallized in the high- ysis). These values are in agreementwith the range temperature hydrothermal range, antimony-bearing of temperaturesand depths of formation estimated sulfides in the medium hydrothermal range, whereas for these districts from geological and laboratory arsenic-bearingsulfides generally belong to the low- (fluid-inclusion data) studies:depth about 3 km, tem- temperature hydrothermal (epithermal) ranges. perature 300-200oC,to depth lessthan I km and Abundant data including phaseequilibria (e,g., Crug temperature less than 200'C (Nash 1972, Shaweet 1967),fluid inclusions(e.g., Nedachiet a/. 1973),sra- al. 1984). Significantly, the values for galena from . ble isotopes,and other data indicate that most of the Round Mountain and Manhattan districts show the mineral paragenesesbelonging to the pb-Bi-Ag- wide variation and, moreover, two populations, one (Cu)-S system have crystallized at temperatures with values greater than 2 and the other with values between2@ and 400oC. Galena + Pb-Bi-Ag(Cu) less than 1. Samplesof galena from one locality sulfosalt assemblagesat lvigtut, Greenlandare inter- (Lead-Silver King prospect) have two distinct chem- preted to have crystallized between 300 and 550.C ical compositions, based on major-, minor-, and (Karup-Mdller 1973,1977,Karup-Mdller & pauly trace-elementcontents, as well as two distinct habirs 1979).Galena and associatedsulfosalts in the Dar- (fillings in sheared quartz, and as irregular tabular win district, California wereinterpreted to have crys- crystals in quartz vugs). The two samples(DRS-79- tallized at more than 350oC (Czamanske& Hall 18 and DRS-74-142b)have low silver and bismuth r97s). contents and elevated antimony contents relative to The annealing of sampleswith high bismuth con- those of DRS-7+142.a,which has high silver and bis- tents (21 to 27 wt.tlo Bi) and that do not lie on the muth and low antimony. Thus, two generations of galena-matildite join (i. e., being composedof matil- galenaappear to be present,a high-temperatureform dite, clausthalite,and galena)at 500oCfor 5 hours and a low-temperature form. produces a galena-typepattern (Czamanske& Hall Khetchikov (1958) found two generations of 1975).This is due to reincorporation of the other ele- galena in a polymetallic skarn deposit in the Soviet ments into the high-temperature galena structure. Far East: the first is high in bismuth and is early, Galenobismutite has been determined to be sta- whereasthe second has no bismuth and is late. ble aboveabout 390oC(Hoda & Chang 1975,Chang However, within the first generationof galena,great & Hoda 197?).Below this temperature,decomposi- heterogeneity(as much as 2wt.t/o Bi difference) was tion to bismuthinite and lillianite occurs: 3pbBirsa found from closely spacedsamples within the same - 2Bi2S3+ Pb3Bi2S6.Galenobismutite was found type of ore. This heterogeneity was attributed to at only one locality (DRS-80-5O examined in rhe inclusions of galenobismutite. The two generations Round Mountain - Manhattan area. Only bis- of galena from the Kti-Tberda deposit, northern muthinite is directly associated(intergrown) with the Caucasus,U.S.S.R. (Ontoyat et al. 1982),deposited galenobismutite.As mentioned in earlier pages, in Paleozoic and Mesozoic time, respectively, are another part of the samepolished sectioncontains another exampleof two distinctly separateepisodes gustavite and bismuthinite. Deposition of the of mineralization. galenobismutite and bismuthinlle as interlocking Galena is definitely not always t}le simple mineral euhedral crystals indicates that the bismuth that it commonly is assumed to be. Galena may ( + silver?)mineralization took place above 390oC, under appropriate conditions contain substantial if the stability dara of Chang & Hoda (1977)are used amounts of silver and bismuth (with lesserantimony) as a geothennometer. in solid-solution (as much as 25 mol.9o AgBiS), Bismuth and antimony contents of 204 samples without decomposition to matildite plus silver- and ofgalena from 84 depositsrepresenting a depth range bismuth-free galena. The substitutional scheme MINERALIZATION IN COLD DISTRICTS, NEVADA 373

2Pb2+ = Bi3+ + Ag+ has beenaccepted by many The mdn gold-silver mineralizationat Round Moun- investigatorsto accountfor the presenceof silver and tain occurred x 25 Ma within a rhyolitic ash-flow bismuth in galena. However, as noted by Karup- tuff. This mineralizing event, by modification of an Mdller On7), any surplus of silver over bismuth (in older (Cretaceous?)vein, may have beenresponsible single-phasegalena) would require, in order to main- for production of the two coexistingcompositions tain charge balance, the insertion of 2Ag* for each of PbSo at the Fairview mine. The two distinctly Pbz* removed.One of the two silver atoms would different compositions of galena found at the Lead- therefore have to be placed in interstitial positions Silver King prospect are probably products of Ter- in the galena structure. However, as also noted by tiary eventsyounger than the 27 Matuff of Mount Karup-Mdller (1977), such positions are apparently Jeffersonthat forms one wall of the Lead-SilverKing not available, accounting for the apparent impossi- vein system.An economically significant gold-silver bility of finding more than a few tenths of a mol.9o mineralizing went at Manhattan took place at 16 Ma silver in excessof bismuth. An excessof bismuth is within Paleozoic sedimentaryrocks along the south readily accounted for, because for every 3Pb2* margin of the Manhattan caldera. A separate but removed, 2Bi3" enter into the galena structure, undated (probably early) Tertiary mineralizing event leaving one lead position empty. If a substantial introduced mercury, antimony, and arsenicminerals excessof bismuth is present, and no other bismuth- into the eastern part of the Manhattan belt (a bearing minerals are present, then a domain struc- northeast-trendingzone centeredon the White Caps ture may exist. Such domain structures may be simi- mine: Shawe 1986). Other centers of mercury, lar to those of the lillianite homologues (Karup- antimony, and arsenic mineralization peripheral to Mdller 197). Multiple generationsof galenaare res- the Manhattan caldera may have formed conclu- tricted to base- and precious-metal deposits where rently. Formation of the mercury-bearing Bi-Pb- sufficient ?mounts of silver and bismuth both are Ag-Cu sulfosalts(phases X and Y), coloradoite, and present in lead-rich environments. We believe thar the mercurian galena in a Cretaceousquartz vein at thesegalenas originate by either incomplete exsolu- the Outlaw prospectis thought to have occurreddur- tion resulting from rapid sqsling, or by multiple ing this episodeof mineralization. heating (mineralizing) eventsin varied geochemical Thus, we infer a general sequenceof deposition environments. of sulfides and sulfosalts in the Round Mountain - The presenceof coexistinggalenas with or without Manhattan area,although timing of the sequenceis associatedPb-Bi-Ag(Cu) sulfosalt assemblagessup- imperfectly known, and similar stagesin different ports the geological and geochronological evidence localities may not be strictly correlated in time. Iso- for multiple and chemicallycomplex stagesof miner- topic ageshave not been determined on any of the alization in the Round Mountain and Manhattan dis- lead minerals. Interpretations of lead-isotope ana- tricts. They also may be usedas crudely approximate lytical data would of coursedepend on assumptions geothermometers. that may or may not be valid for the complsx mingl- The Round Mountain and Manhattan districts are alized environments in the two gold districts. An areasin which severaldistinct and separateepisodes early high-temperature event related to the Creta- of base- and precious-metal mineralization took ceousgranite plutons involved deposition of simple place over approximately 65 Ma (80 to 15 Ma). Fol- sulfides in tactites and quartz veins. At a later time, lowing emplacementof granite plutons, a variety of a high-temperature bismuth-, silver-rich hydrother- small, mostly uneconomic base-and precious-metal mal activity locally modified these deposits. Proba- veins and tungrl"n-6garing tactite and vein deposits bly at about 35 Ma a lower temperature copper- formed at 80-75 Ma in the granite and in nearby lead-zinc-arsenic-antimony mineralization (charac- Paleozoic carbonate and clastic rocks (Shaweel a/. terized by covellite replacement of galena and 1984, 1986,Shawe 1985, 1986). These deposits are tetrahedrite-tennantite deposition) related to the characterizedby small amounts of simple sulfides: granodiorite stock and associated rhyotte dyke- pyrite, sphalerite, chalcopyrite, and galena. The swarm modified some of the Cretaceousveins. Still quartz-hiibnerite veins in granite were subsequently later, at about 25 Ma and at 16 Ma, low-temperature remineralized with copper, lead, zinc, arsenic, and gold mineralization occurred at Round Mountain antimony in the vicinity of a 35 Ma granodiorite and at Manhattan, furtler modifying older deposits stock and associatedrhyolite dyke-swarm.Deposi- in those areas.A Tertiary mercury-arsenic-antimony tion of Pb-Bi-Ag(Cu) snlfidesand sulfosalts, as well low-temperature event also modified older d€posits as tetrahedrite-tennantite, and the replacement of in the vicinity of the White Caps mine, the Outlaw galena by covellite, are thought to have been prospect, and at other centersperipheral to the Man- associated with this event. Possibly two separate hattan caldera. events, an early bismuth-rich event (a late phase of Additional new mineral species in the Pb-Bi- the hiibnerite epi$ode, at 80 Ma?), and a late Ag(Cu) t Hg systemcontinue to be reported. Many tetrahedrite-tennantite event (at 35 Ma), took place. additional studies remain to be done on this sy$tem 374 THE CANADIAN MINERALOGIST to further elucidate T, P, and lS, conditions of FencusoN,H. G. (1921):The Round Mountain dis- mineral deposition in complex natural systems. trict, Nevada.U. S. Geol.Sum. 8u11.12U1, 383 406.

AcKNOWLEDGEMENTS Fnvasnm,V. K., Lrravnnqa,R. F., RoN,raNsNKo,I. M. & Cuueenov,V. M. (1981):On lillianite-gustavite andthe lillianite-gustavitemineral series in tin ores The authors thank C. Heropoulos (U.S. Geolo- gical of the Kavalerovsk region. Zap. I/ses. Mineral. Survey, Menlo Park, Calif.) for emission- Obshch.Ll0, 304-310.(In Russ.). spectrographicanalyses for the chalcophile elements on selectedminerals and mineral mixtures. We are Foono,E. E., Snawn,D. R. & Corrm, N. M. (1985): grateful to JamesCraig (V.P.I., Blacksburg,Va.) Multiple coexistingphases of galenaand associated for sealing some galena and sulfosalt samples in sulfosalts from the southern Toquima Range, quartz tubes under vacuum and annealing them for Nevadaand the Idaradomine, Ouray, Colorado. us. One sampleof 'benjaminite' from the Outlaw Geol. Soc.Amer. ProgramAbstr. 17,219. prospectwas provided by Forrest Cureton. The staff of the U.S. GeologicalSurvey library was most help- Harnrs, D. C. & CHrN, T. T. (1975):Benjaminite, ful in obtaining many of the Russianlanguage pub- reinstated as a valid species.Can. Mineral. 13, lications used in this work. We gratefully 402401. acknowledge the careful and perceptive reviews of (1976): R. C. Erd, P. J. Modreski, and B. F. Leonard, all & - Crystal chemistryand re- examination of nomenclatureof in of the U.S. GeologicalSurvey. We sulfosalts the alsoacknowledge aikinite-bismuthinite series. Can. Mineral. 14. the constructive reviewsof two anonymous referees t94-205. and the editor of the Canadian Mineralogist, R. F. Martin. & OwnNs,D. R. (1973):Berryite, a Canadian occurrence.Can. Mineral. 11, 1016-1018. RSFERENcSS Hnnrrnr, H. K. & Muulre, W. G. (1981):Unsub- Bonooevrv,Yu. S. & Mozcovn,N.N. (1971):New stituted benjaminite from the AW Mine, NSW: a group of the sulfobismuthidesof Ag, Pb and Cu. discussionof metalsubstitutions and stability.Neaar Soc. Mining Geol, lapan, Spec. Issue. (Proc. of Jahrb. Mineral. Monatsh., 69-80. IMA-IAGOD meetings'?0, joint symp.)2, 344.1. Hona, S. N. & CnaNc,L. L. Y. (1975):Phase rela- Cuarc, L. L. Y. & Bevnn,J. E. (1973)Lead sulphosalt tions in the systemsPbS lg2S-Sb2S3and PbS- minerals:crystal structures,stability relations, and Ag2S-Bi2S3.Amer. Mineral. 60, 621-633, paragenesis.Minerals Sci. Eng.5, l8l-191. HouucHr,H. & WuBNscs, B. J . (1977):Lindstrdmite, group & Hooa, S. N. (1977):Phase relations in the Cu3Pb3Bi7S15:its space and ordering scheme system:m PbS-Cu,S-BirSrPbS-Cu2S-Bi2S3 and the stability of for metal atoms in the crystal structure. Car. galenobismutite.Amer. Minerql. 62, 346-350. Mineral. 15, 527-535.

Cnrranove,K. A. & Sr,wsanrv,A. P. (1974):Find of Kanw-Mor.mn, S. (1966):Berryite from Greenland. seleniferoushammarite in the Orlovskoyedeposit, Can. Mineral. 8, 414423. Rudnyy Ntai. Dokl. Acad. Sci. USSR,Eorth Sci. Sect.216,14+146. (1972):New data on pavonite,gustavite, and some related sulfosalt minerals. Neues Jahrb. CnrN, T. T., Krncmwn,E. & Paan, W. (1978): Mineral. Abh. 117, 19-38. Friedrichite,Cu5Pb5Bi7Sls, a new memberof the aikinite-bismuthinite series. Can. Mineral. 16, (1973): A gustavite-cosalite-galena-bearing t27-t30. mineral suite from the cryolite deposit at Ivigtut, South Greenland.Medd. Grdnland 195(51. Cnerc, J. R. (1967): Phaserelations and mineral assemblagesin the Ag-Bi-Pb-S system,Mineralium -(1977): Mineralogyof someAg-(Cu)-Pb-Bi sul- Deposita1,278-306. phide associations.Bull. Geol. Soc.Denmark 26, 4l-68. Czauarsrn,G. K. & Har.l, W. E. (1975):The Ag-Bi- Pb-Sb-S-Se-Temineralogy of the Darwin lead- & Marovrcrv, E. (1979): On pavonite, silver-zincdeposit, southern Californta. Econ. Geol. cupropavonite,benjaminite and "oversubstituted" 70, r09Lltt0. gustavite.Bull. Mineral. 102, 351-367.

DunrNrNc,G. 8., CoornnJ. F., Jn. & Moss,G. E. & - (1981):Ae- and Bi-rich heyrovsklte (1988): Rediscoveryof the Outlaw mine, Nye from the Bi-W-Mo mineralization at Castlegar, County, Nevada.Miner. Rec. (in press). British Columbia. Can. Mineral. 19, 349-353. MINERALIZATION IN GOLD DISTRICTS, NEVADA 375

& Pnulv, H. (1979):Galena and associatedore NxH, J. T. (1972):Fluid-inclusion studres of some mineralsfrom the cryolite depositat lvigtut, South gold deposits in Nevada. In Geological Survey Greenland.Medd. Grdnland,Geosci.,25 pp, Research,1972. U.S. Geol.Sum. Prof. PaperS0nC, cl5-c19. KHercuxov, L. N. (1958):On the questionabout the content of bismuth in galena. SoobshcheniyaNsoacHl, M., TareucHr, T,, Yeuaora, K. & Dal'nevostoch.Filiala im. V. L. Komarova.u4N TaNrcucHr,M. (1973):Bi .le-Pb-S mineralsfrom CCCP, No. 9, 133-136.Vladivostok. (In Russ.). Agenosawamine, Akita Prefecture, northeastern Japan.Tohoku Univ., Sci.Rep., Third Series,12, Kosrov, I. & MrNlsve-Smrarove,J. (1982):Sulphide no. l, 69-80. Minerals- Crystal Chemistry,Parageneses and Sys- tematics.E. Schweizerbart'scheVerlagsbuchhand- Nurrrcro, E.W, (1953):Benjaminite. Amer. Mineral. lung, Stuttgart,W. Germany. 38, 550-552.

Kovelpuren,V. A., Marov, V. S., Ynvsrtcr.meva,T. - (1954):Studies of mineralsulpho-salts. XVII. L. & Vvel'sov, L. N. (1984):Junoite and pekoite Pavonite, a new mineral. Amer. Mineral. 39, - first find in the USSR. Zap, Vses.Mineral. 4094t5. Obshch.ll3, 3543. (1975):Benjaminite - a re-examinationof the Maroucrv, E. & Kenup-Morlsn, S. (19?7a):Chemis- type material.Can. Mineral. 13,3944A1. try and crystallographyof the lillianite homologous & Hannts,D. C. (1966):Studies of mineral series.I. Generalpropefiies and definitions.Neues sulpho-salts.XX. Berryite, a new species.Care. Jarhb. Mineral. Abh. L30,2U-287. Mineral. 8, 407413. & -(1977b): Chemistryand crystallogra- phy of the lillianite homologousseries. II. Defini- ONrovev,D. O., DnuzrnxtN,A. V., TsentN,A. I., tion of new minerals:eskimoite, vikingite, ourayite Vval'sov, L. N. & Basove,G. V. (1982):Minerals and treasurite.Redefinition of schirmeriteand new of the gustavite-lillianiteseries from the Kti-Teberda data on the lillianite-gustavite solid solution series. deposii(northern Caucasus). Int. Geol. Rev.24, NeuesJahrb. Mineral. Abh. l3l, 56-82. 659-670. & - (1984):Ourayite from lvigtut, Green- Pnacrn{, I. (1979):Aikinit z Krupky, CSSR.z4cta land, Can. Mineral. ?2, 565-575. Univ. Carolinae-Geol.No.34, 183-186.(In Czech.).

& Marovrcrv, M. (1978):Representation of SsasNoN,E. Y. (1924:):Benjaminite, a newsulphosalt compositionsin the bismuthinite-aikiniteseries. mineralof the klaprothitegroup. Proc, U.S. Nat. Can. Mineral. 16, 4A5-409. Museam65, art.24. - & Muut"tp,W. G. (1979):The crystalstructure Suewr, D. R. (l98la): Geologicmap of the Round of benjaminite Cus.joPbe.a0Ag2.3sBi6.seS12.Caz. Mountain quadrangle,Nye County,Nevada. U.S. Mineral. 17, 607-618. Geol.Sum. Open-FileRep. 8l-515, scalel:24,000.

Mar-arHov,A. A. (1968):Bismuth and antimonyin - (l98lb): Geologicmap of the Manhattanquad- galenasas indicators of someconditions of ore for- rangle, Nye County, Nevada. U.S. Geol, Sum. mation. Geochem.Int. 7, 1055-1068. OWn-File Rep. 8l-516, scale I :24,@0. Mozoove, N. N. (1979): Nonstoichiometric and (1985):Multiple episodesof mineralizationin homologousseries of sulfosalts.Mineral. Zh. l, the southernToquima Range,Nye County,Nevada. 93-98.(In Russ.). ,lz USGSResearch on Mineral Resources-l985,Pro- eram and Abstracts(K. Krafft, ed,), U.S. Geol. Muuun, W. G. (1975):The crystalstructure of krup- Sum. Circ.949, 4849. kaite, CuPbBi3S6,from the Juno mine at Tennant Creek, Northern Territory, Australia. Amer. (1986): Complex history of preciousmetal Mineral.60, 300-308. deposits,southern Toquima Range, Nevada. U,S, Geol. Sum. Open-FileRep.86-0459. & Warrs, J. A. (1976):Pekoite, CuPbBi11S16, a neww memberof the bismuthinite-aikinite mineral Foonp,E. E. & CouruN,N. M. (1984):Hueb- series:its crystal $tructure and relationship with nerite veins near Round Mountain, Nye County, naturally- and synthetically-formedmembers. Can. Nevada.U.S. Geol. Sum, Prof. Pap. l?37. Mineral. 14,322-333. -, MenvIN, R. F., Atontessst{,P. A. M., Wrlm, E. & Wu'rNscs,B. J. (1976):Crystal Msm.rEnr,H. H. & Mennrrt,V. M. (1980:Ages of chemistryand proposednomencliature for sulfosalts igneou3 and hydrothermal events in the Round intermediate in the system bismuthinite-aikinite Mountain and Manhattan gold districts, Nye (Bi2S3-CuPbBi\).Amer. Minerol. 61, 15-20. County, Nevada.Econ. Geol.81, 388407. 376 THE CANADIAN MINERALOGIST

SvNetrr, V. & Hrnrnn, J.0974)l. The crystalstruc- - & Pnacuafi.,I. (1981):Estimation of chemical tures of krupkaite, CuPbBi3S6,and of gladite, compositionsof the bismuthinite derivativesfrom CuPbBisSe,and the classificationof superstructures the lattice parameters. Neues Jahrb. Mineral. in the bismuthinite-aikinite group. Neues Jahrb. Monatsh., 495-544. Mineral. Monatsh., 541-560. -, Srrrdrr, V. & Hvrlrn, J. (1974):Krupkaite, ZAK,L. (1980):Isomorphism and polymorphismin the CuPbBi3S6,a new mineral of the bismuthinite- bismuthinite-aikinitegroup. NeuesJahrb. Mineral. aikinite group. Neues Jahrb. Mineral. Monatsh-, Monatsh., 440448. 533-541. & Hrnren, J. (1981):Krupkaite (x = 1.3)from Dobsina, CSSR.Nerres ./a& rb. Mineral. Monotsh., Received December 15, 1986; revised manuscript 20G2r4. acceptedJune 29, 1987.