CC)L(l!~AUC. GJBX-16{ GEOl c.)C;ICAL SURV~Y . ,<..,, . /W'-' ~ '"\ ""' 0' ~ J. cc ~1'14 GJBX-16(77)
GEOLOGY, URANIUM DEPOSITS, AND URANIUM Ff\VORABILITY OF THE HARTFORD HILL RHYOLITE AND TRUCKEE FORMATION, SOUTHWESTERN WASHOE COUNTY, NEVADA, AND EASTERN LASSEN COUNTY, CALIFORNIA
G. M. Cupp, S. H. Leedom, T. P. Mitchell and D. R. Allen
BENDIX FIELD ENGINEERING CORPORATION Grand Junction Operations Grand Junction, Colorado 81501
April 1977
PREPARED FOR THE U.S. ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION GRAND JUNCTION OFFICE UNUER CONTRACT NO. E(OS-1)-1664 CONTENTS
Page
Summary . • . . .. . 1
Introduction 2 Objectives and scope . . 2
Previous work 2
Acknowledgments 4
Procedures 4
Field procedures 4
Sampling procedures 4
Analytical procedures 5
Statistical correlation of rock units 5
Geology . , • . , . . • . • 5
General stratigraphy 5
Mesozoic rocks . . 5
Tertiary rocks 8
Quaternary rocks 9
·stratigraphy of the Hartford Hill Rhyolite 9
Cooling Unit 1 , . , . 10
Cooling Unit la 10
Cooling Unit lb 13
Cooling Unit 2 ' . . ' 14 Cooling Unit 3 . • ' . 14 Rainbow Canyon Member 16 Maue-McCray Men1ber . ' 16 Cascade Member . . . . 17
iii CONTENTS (continued)
Geology (continued)
Dikes . • 17
Conclusions 18
Stratigraphy of the Truckee Formation 18
Long Valley . 18
Hungry Valley and Warm Springs Valley 19
Structure 20
Uranium deposits 22
Hartford Hill Rhyolite 22
Deposits related to fracture systems 23
Deposits related to organic debris 24
Deposits related to basalt dikes 25
Truckee Formation 26
Uranium favorability 29
Uranium favorability criteria for the Hartford Hill Rhyolite . • . . . . • . 29
Uranium favorability criteria for the Truckee Formation • • . • 29
References cited 32
Appendix A. Prospect names, locations, production, and development work ...... 33
Appendix B. Pr~spect maps and analytical results • 39
lv ILLUSTRATIONS
Figure l. Index map of the Hallelujah Junction Pyramid Lake project area ...... 3
2. Simplified geologic base map of the Hallelujah Junction-Pyramid Lake proje~t area · · · · · • 6
3. Simplified stratigraphic section fo·r the project area . • ...... · · · · · 7
4. Correlation chart for the stratigraphic sections of Brooks, McJannet, Wallace, and the present study ...... 11
5. Correlation chart for McJannet's Basal Member of the Tule Peak Formation and basal portion of the Hartford Hill Rhyolite . . . . . 12
6. Favorable areas for uranium exploration 30
Plate 1. Geologic map of a portion of the In Virginia Mountains ...... pocket
2. Geologic map of a portion of In Petersen Mountain ...... pocket
APPENDIX ILLUSTRATIONS
81. Buckhorn mine geologic map 40
B2. Bastian prospect geologic map 43
B3. DeLongchamps mine geologic map 45
B4. Geologic plan of DeLongchamps mine adit 46
BS. Radiometric and sample plan of DeLongchamps mine adit 47
B6. Red Bluff prospect geologic map . 49
B7. Geologic, radiometric, and sample plan of Red Bluff prospect adits 50
B8. Garrett prospect geologic map 53
119. Armstrong mine geologic map . 55
v HARTFORD HILL RHYOLITE AND TRUCKEE FORl~TION, NEVADA AND CALIFORNIA
SUMMARY
The Hartford Hill Rhyolite and the overlying Truckee Formation are host for several uranium deposits found in an area extending from Long Valley (Lassen Co., California) eastward to the Virginia Mountains (Washoe Co., Nevada) and from Severi Lakes Mountain on the north to Hungry Valley on the south.
The Hartford Hill Rhyolite i~ a series of ash-flow sheets that range in age from late Oligocene to early Miocene. This series at tains a maximum stratigraphic thickness of approximately 4,000 ft. The formation is divided into seven ash-flow tuff cooling units and avalanche deposits, which range in composition from rhyolite to an desite.
The Truckee Formation is a sequence of alternating lacustrine, fluviatile, and volcanic rocks of Pliocene age, which attains a thickness in excess of 3,000 ft. Basaltic and rhyolitic lava flows are found at or near the base of the formation. Above these flows are sandstones and conglomerates that grade upward to clayey lake beds and tuffs. In Long Valley the upper one-third of the formation is a quartzitic sandstone. Mudflow sheets with large granitic boulders are scattered throughout the sequence.
All known uranium deposits in the Hartford Hill Rhyolite, with one exception, are confined to two cooling units (units lb and 3). The deposits are localized by organic material, fractures, and dikes. They are small deposits that range in grade from less than 100 ppm to 800 ppm u3o8 . Uranium deposits in the Truckee Formation are near the base of the formation, adjacent to contacts with the underlying Hartford Hill Rhyolite. Deposits have been localized by organic material, by thin clay beds, or along contacts with the Hartford Hill Rhyolite. These deposits are small in size and range in grade from less than 100 ppm to 410 ppm u3oR. No genetic relationship was observed between Tertiary intrusive rocRs and uranium occurrences.
Favorability for important uranium deposits in the Hartford Hill Rhyolite is judged to be low. The known occurrences are of limited extent, and the overall uranium content of the formation is low (4 to 10 ppm u3o8). However, because of the thickness and extent of the formation and the uranium occurrences contained in it, it may have been a source for uranium in the younger, topographically lower Truckee Formation.
Uranium favorability of the Truckee Formation is judged to be high. It has moderat('ly abundant amounts of organic material, con ta:l.ns extensive favorable rocks types and is in a favorable topographi< and stratigraphic position to receive uranium-bearing solutions de rived from the weathering and eroslon of the Hartford Hill Rhyolite. APPENDIX ILLUSTRATIONS (continued)
Figure BlO. Geologic, radiometric, and sample plan of Armstrong mine adits • • • • . • 56
Bll. Jeannie "K" prospect geologic map 58
Bl2. Cornelia "C" prospect geologic map • 60
Table Bl. Buckhorn mine 41
B2. Bastain prospect . 44
B3. DeLongchamps mine 48
B4. Red Bluff prospect 51
B5. Garrett prospect 54 B6. Armstrong mine . . 57 B 7. Jeannie "K" prospect . . . . . 59 B8. Cornelia "C" prospect . . . . 61
vi INTRODUCTION
The Hartf{~);;"g,J-IiJ.,l, Rhyo.l:i,te (Miocene..)-anti> 1 the overly OBJECTIVES AND SCOPE This study was conducted by Bendix Field Engineering Corporation (BFEC) under the auspices of the U.S. Energy Research and Development Administration (ERDA). The objectives of this study were: (1) to define a;ad,,"gef,JJ.,l~%.~e f<'JXO.:X: (2) to determine the relationsp;i.p .pJ d.acit.~ jii.lug.s., (intrusive bodies of Kate Peak Formation in the vicinity of Mullen P·a;~y ''to'"'ncearby ura~ium deposits. The sc;~~. of this project included a seareft.c.. Q~ t.b.a,l.it.erature, general geolRg:U; l;',e,e~n.a,~a,p.t;,e,.,.,detailed ma,p,ping of the larger prospects, sur{p~.~· ~~~UI.g, surface r:al;\tPiti~J,ric survexing, detailed examination of the stratigraphy of the Hartford Hill Rhyolite and the Truckee Formation, chemi,cat PREVIOUS WORK Brooks (1956) mapped and described the Lowary (Maue-McCray prospect) and the DeLongchamps mine in the Virginia Mountains. McJannet (1957) mapped and described the geology of the Pyramid Lake-Red Rock Canyon area. Gimlett (1967) conducted a gravity survey of Warm Springs Valley and described the geology. Bonham (1969) mapped and described the geology and mineral deposits of Washoe County, Nevada, including several uranium deposits in the project area. Garside (1973) listed and briefly described uranium deposits in Nevada, including those in the project area. Wallace (1975) mapped and described the geology and mineral deposits of the Pyramid m~n~ng district, including a brief description of uranium deposits in the Ha~tford Hill Rhyolite. 2 HARTFORD HILL RHYOLITE AND TRUCKEE FORMATION, NEVADA AND CALIFORNIA ACKNO\.JLEDGMENTS Larry J. Garside and Harold F. Bonham, Nevada Bureau of Mines and Geology, and Andy B. Wallace, graduate student at the University of Nevada, gave generously of their time discussing the geology and mineral deposits of the area. PROCEDURES The objectives of this program were met by using information collected in the field and obtained from published literature. Rock samples were analyzed by the Grand Junction Laboratory of the Energy Research and Development Administration, operated by the Bendix Field Engineering Corporation. FIELD PROCEDURES Two stratigraphic sections of the Hartford Hill ~k.~~ were studied in detail; one on the east side and one on the west side of the project area.. The stratigraphic section on the east side is in Mine Canyon, sec. 36, T. 24 N., R. 20 E., Mt·. Diablo Base Line and Meridian, and in Rainbow Canyon, sec .. 6, T. 23 N., R. 21 E. The stratigraphic section on the west side is in Red Rock Canyon near the north end. of Petersen Mountain, sec. 32, T. 24 N., R. 18 E. Two areas were mapped in detail (Fig .. 1; Pls. 1 and 2). They are significant to understanding the relationship between the Hartford Hill Rhyolite, the Truckee Formation, and related uranium deposits. Ten u:raJ!t~md~.p~,i,ts, thought to be the most significant, were mapped by plane table. Reconnaissance studies were made of seven teen other deposits. Underground mapping and sampling were done where possible. SAMPLING PROCEDURES Samples of the stratigraphic sections were collected for chemical and petrographic analys:i:s. The uranium deposits were sampled to determine their size and shape, the uranium minerals present, the rock units involved, and the general nature of the individual deposits. Individual samples were collected over areas of similar radiometric reading, generally in 200 cps increments. Select samples were collected :Ln areas of special interest. Radiometric scans were made over the sample intervals and stratigraphic sections with a Mt. Sopris Scintillometer Hodel SC-131A and a Measurements, Inc. Model 3 Geiger Counter. Readings were recorded in counts per second (cps). 4 IIARTFORD HILL RHYOLITE AND TRUCKEE FOK._tf_~_:_IOJ'iL_B}~V_A[!A__ Al'll~S.1.!!:!..:J~RNlA_ -··---·-----·---·------·------·----·-----·-' - ANALYTICAL PROCEDURES A totracl·o~~~:X:I:tl:i': =mPl. STATISTICAL CORRELATION OF ROCK UNITS ,. The silver, copper, lead, zinc, and zirconium content in samples of the Hartford Hill Rhyolite, the Kate Peak Formation, and the gran odiorite of Petersen Mountain was determined and the results plotted on a series of bar graphs. Comparisons were made to d~.t~rmine if the trace elemea,t;:,,C:..QQ,t~t 11 . 1 Qi ~~, 1 ~t un:i.q~J:¥ 11 .0.~-~in&uis~ed., it from other rock units. Reliable d}~~~,ip~ti..~IJr~J--~~~},.9 1 n?t, always be made. Data for ~~.i,.~OI);~1 ~m was plot ted on prq~JJ~y paper, ppm zir conium versus cum~t1ve frequency. The plot for the Hartford Hill Rhyolite illustrated that as much as_ ~.8, ..P~J;-1;:.~1)1.~ q,t" the Vfilues belong to a single, alm~s~; ~9rJ)ll~lJ,.~, d~;,r.j..bt,LJ;,!ifd,.,~9,Pu..1.,ation. The 12 percent apparently not iri this population were examined but no unique character istics were identified. It is possible that wall-rock material, car ried up by the eruptive ·process, was incorporated in the unit and inadvertently sampled. A similar plot of zirconium analyses for the Kate Peak Formation, gr~~~I?Fite from Petersen Mountain, and Hartford Hill RJ1yoltt~~,.).dentified zirconium populations unique to the individ ual rock types. I GEOLOGY e GENERAL STRATIGRAPHY I I Rocks of Mesozoic to Tertiary age are exposed in the mountain ranges and valleys of the project area (Fig. 2). Quaternary sediments fill most of the valleys. Figure 3 shows the major rock units present. Mesozoic Rocks The oldest rocks are Mefj!~~s>-~f ID!f.~1 fl-p,~diments and metavolcanics that are believed to be part of the Peavine and Nightingale sequences of probable Triassic or Jurassic age (Wallace, 1975, p. 11). These 5 N. .H~ j ~~ QGate rna r y de po s i t s • lJ.!,LC."B Fo rmat i on· ~!v~ Tertiary volcanics ~ Kate Peak Formation F:!0l 0'>. ~ Hartford Hi II R~.!e RTI Mesozoic basement and ~ older /', Contact: dashed where ' approximately located ,. Fault: U, upthr·ownside J:L,' 0, downthrownside: 0 dashed wher~ approxi mately located ~ S t r i ke and d i p Prospect and/or mine Figure 2. Simplified geologic base map of the Hallelujah Junction- Pyramid Lake 8 location project area. e e Quaternary sediments: Stream deposits, ~lopewash, talus Pleistocene alluvial fan deposits, to Recent eolian deposits, lake deposits, {8 and land slide deposits. Tertiary Truckee Fornation: Lake beds, fluviatile sands, boulder zones, tuff beds, Pliocene { and basalt flm.,rs. I Tertiary volcanics: Andesitic I Tv and basaltic volcanics and G I (Tab) associated rocks, upper part Miocene Tab is equivalent to Lousetown Tv Basalt. Lower part Tsv is (Tsv) equivalent to Pyramid Sequence. iI ---1 I Tertiary dacitic flows (Tk) Tertiary Hartford Hill I and intrusives (Tki) previously I Rhyolite: A sequence of mapped as Kate Peak Formation. rhyolitic ash-flow tuffs EEJ Oligocene with minor basaltic mud flows, airfalls, andesite {G and basalt dikes, and reworked tuffs. Mesozoic basement: Granitic rocks with minor pegmatite and Hesozoic and aplite dikes and gabbro older pods; metavolcanics {8 and medisediments. ------Figure 3. Simplified stratigraphic section for project area (modified after Bonham, 1969). rocks are found as ~f,..,,peu\lapts or as large continuous outcrops associated w~.th ply.):;.Q,p_.i,<;:~ rocks. They range in metamorphic grade from greenscl1ist facies to pyroxene hornfels (Wallace, 1975, p. 12) . The metamorphic rocks were' iat.l;.l,ld,eQ. .. ,.h¥-,,t:i~!?QZOi~ P.lutonic rocks inferred to be part of a northern extelljO~~f,~·~ll_..>'·~vada batholith (Wallace, 1975, p. 12). These plutonic rocks were mapped, on the basjs of age dat,~~·. ~~··. J~~:t"a~~.!.c,,t~ .S,ret~~~.e<:us in age (Hallace, 1975, p. 12). The roc'ks range in composition from quartz diorite to quartz monzonite. Some rocks of gabbroic compos ition are prbsont, as well as pegmatite and aplite dikes and pods. These rocks have been grouped togetl1er on Figure 2 as Mesozoic base ment (mb). ~rertiary Rocks The oldest Tertiary rocks in the study area are silicic to intermediate ash-flow, tuffs, of t:he,.!Jartford Hill RhyoJ,ji.te. Radio metric dates of 27.9 + 0.8 m.y. to 21.6 + 0.6 m.y. place the sequence in the late, Oligocene""' ~0-~SJ:rly Miocene,, (Wq,llace, 197 5, p. 37) . The for mation ranges in thickness from 0 to 4,000 ft, reaching maximum thickness in the Mullen Pass and Dogskin Mountain areas (Bonham, 1969, p. 23). Dacite int~usives and flows (Tki and Tk, respectively; Fig. 2) have been correlated with the Kate Peak Formation by Bonham (1969); l10wever, recent age dates of 19.3 ± 0.8 m.y. and 20.7 ± 0.6 m.y. show these rocks to be older than the Kate Peak Formation (Wallace, 1975, p. 52). This, together with petrographically similar brecciated flow rocks found in an upper member of the Hartford Hill Rhyolite, suggest that they are correlative in part with the Hartford Rt.ll Ra¥dJ.ite. They would therefore be early tii.a~ ,,j,n ~· According to Wallace (1975, p. 50-51), these rocks range in composition from rhyodacite to andesite. Tl1ey are porphyritic in texture with phenocrysts composing 20 percent to 30 percent of the rock. Of the phenocrysts, 65 percent are plagioclase, 10 percent quartz, 10 percent biotite, and 10 percent horn blende. The phenocrysts range in size from 4 mm to 6 mm. The matrix is composed of SO percent plagioclase, 45 percent quartz, and 2 to 5 percent magnetite, apatite, and rutile. Matrix crystal size is 0.02 to 0.05 mm. The color is light bluish gray to medium light gray. Rocks of this unit are prominently exposed in Mullen Pass as small intrusive plugs. Other small intrusive bodies. are found in Warm Springs Valley and in 'spanish Springs Valley. A small dacite flow is exposed at the northern end of II!Jllgry Valley. Wallace (1975, p. 136) interpreted these intrusives and flows to be post-Pyramid mineralization in age. Field data indicates that they are not related to uranium mineralization, however, as uranium deposits in the area appear to have no spatial relation to the Pyramid mining district. · 8 11/\RTFORD lllLL RIIYOI.I TE /\ND TRUCKEI·: FORMATlON.J_N_EV/\D_/\ /\ND C/\LIFOf~~_!-~ ------ Younger Tertiary volcanic rocks of rhyolitic to basaltic com- positi6n have been grouped into one unit on Yigure 2 (Tv). Older rocks of th:is unit are of the Pyramid sequence with ages of 16 to 21 m~y., placing them in the middle Miocene (Wallace, 1975, p. 48). Younger rocks of this unit are in part correlative with the Truckee Formation and the Lousetown Basalt of middle Pliocene age. These rocks unconformably overlie the Hartford Hill Rhyolite but are not intruded by the dacite plugs of the so-called Kate Peak intrusives . . The Pyramid sequence is more than 4,200 ft thick (Bonham, 1969, p. 28 and 29). Younger basalts in the project area are in excess of 1,000 ft thick (Bonham, 1969, p. 39). Rocks of the Terti~U, ';l:,t\,l<;.l.<,~!if.)'.2).:!)1~t~on .~-.~C?sed in Lo~~ley, in Warm Springs Valley, and in Hungry Vaffey (Tst, Fig. 2) are midcl,Je PJ,i,,!]$;epe in.~ge (Gimlett; 1967, p. 12). The formation is a sequence of f4.vJ.:i,~;L& ..w9illd~p,iq;:erbedded with l<4H Mdav~' t1tffs, and bo~£ .a~ .. , In Long Valley the formation ranges from 0 to more than .),,~~~,J;,~, 4~ql!!~~·ti8;Jicaphic thickness. Quaternary Rocks The Quat;.~~~.r.Q£ok&.,shown on Figure 2 (Qal) are sediments rang '>~ing in age from Plais~aae, tQ.,~:.a~u ,,(Bonham, 1969). They consist ~1of stream, ~lop,e, Wal;? q,,., .. J;iii:l.4.1?..,.,.,aJ,.ll.lvJ.aJ. .f.an, eol~n, .lacustrine, and ;~landslide d~p.~stF,~,S~ STRATIGRAPHY OF THE HARTFORD HILL RHYOLITE V. P. G~a named the Hartford Hill ~.Ql.ite in 1936 from exposures at Hartford Hill south of Virginia City, Storey County, Nevada (Bonham, 1969, p. 23). Rocks of this formation in the project area do not appear to be lithologically related to the type section but do appear to have corresponding ages (Bonham, 1975, oral commun.) and are mapped as being part of the Hartford Hill Rhyolite. Ro~ks of the Hartford.Hill Rhyolite were mapped by Brooks (1956), McJannet (1957)~ artd Wallace (1975). Brooks (1956) subdivided the formation into lithologic units that he lettered A through K and U. McJannet (1957) named the sequence the Tule Peak Formation and subdivided it into seven members, naming the members from bottom to top 11s follows: Basal Member, Mine Canyon Member, Pumice M0mh0r, Crystal Tttff Membe~, Rainbow Canyon Member, Maue-McCray Member, and Cascade Member. Wallace (1975) determined that the formation, in the area he mapped, was a serie•...C"·~l.ow.~,t,..,.~t;~ ;;tnd, on the basis of radiometric dates, assigned the units to the Hartford Hill R,~~ite. Both Brooks and McJannet gave accurate descriptions of the formation, but their work was done before the current understanding of ash-flow tuff deposits had been attained. 9 Figure 4 is a correlation chart of the stratigraphic divisions of the Hartford Hill Rhyolite (after Wallace, 1975, p. 15). The chart shows the correlation of unit names used by Brooks, McJannet, Wallace, and the authors of this report. C ,i ;';; The Hartford Hill ~,QJJJ;.e.,.J..a,.a.~®ce of rhy~,i.fi..J.,&,.-6 ar.ulc.:.i1t lc ash-flo}'J tpf,f~ w,,.:h,l;.b ,m.;i.JJ.Q:t; .,.aJ,.:~:-.f.~. t~Jf~.,~ter-laid tuffs, basaltic. mud flows, rhyolitic and dacitic lava flows, and bflsalt dikes. ~,: flow tuff~"C Two areas, one in the Virginia Mountains (Pl. 1) and the other , on the west flank of Petersen Mountain (Pl. 2), were mapped to provide a better understanding of the stratigraphy of the format~on and to correlate the uranium deposits with the stratigraphy. ~e locations of thses areas are shown on Figure 1. Cooling Unit 1 On the basis of field relations observed in this study, Cooling Unit 1 has been subdivided into two cooling units, designated la and lb. McJannet (1957), on the basis of lithology, subdivided his Basal Member into nine units, which he labeled A through I, noting that various units were absent in Mine Canyon, Red Rock Canyon, and at the· Bu'ckhorn mine. Wallace (1975) placed all of McJannet's units into Cooling Unit 1, but Bonham and Wallace believe it to be more complex, probably containing at least two cooling units (Bonham, 1975, oral commun.; Wallace, 1975, oral commun.). Figure 5 illustrates the correlation betwee~ Cooling Unit la, Cooling Unit lb, and McJannet's Basal Member. McJannet (1957) found unit C (part of Cooling Unit lb in this report) in Mine Canyon, Rep Rock Canyon, and at the Buckhorn mine. During this project, unit C was traced from Petersen Mountain to the east end of Seven Lakes Mountain. It was also found on the east side of Hungry Valley and north of Mine Canyon. Unit C appears to be the only unit of Cooling Unit 1 that is uniform throughout the study area. It was on this basis that the correlation between McJannet's units and Cooling Unit la and Cooling Unit lb was made. Cooling Unit la. Cooling Unit la is a vitric to vitric-crystal tuff of rhyodacitic to andesitic composition with small portions of rhyolitic composition. Phenocrysts, composing 4 percent to 18 percent of the rock are quartz (0 to 6 percent), K-feldspar (26 to 79 percent), plagioclase (15 Ll> 67 percent), and hiotlte (4 to 16 percent). 10 e e Hartford Hill Rhyolite Rainbow Canyon-~line Canyons, and Red Rock Canyon Hartford Hill Rhyolite Present Study Rainbow-:t-line Canyons, Members of unnamed Members of HcJ~mnet' s llace (1975) at ion nrooKs \.L::UO} \~...I...IIJ ~ ----- ~ ...... -- ...... Cascade Cascade ~ Member Hember Cooling Unit K 6 ------J Maue- Maue- Cooling McCray .. -~ ... - I McCray Unit 5 ------t------Rainbow MPmhPr H G Canyon Rainbow Hernber I-' Cooling ----- F I-' Canyon Member Unit 4 E ______----:: -C-r~a:1 -r-";Tf''n ..•. . D . Pumice Cooling Nernber Cooling c I Unit 3 Unit 3 B Mine - Canyon Cooling Unit 2 A - Unit 2 ~ Basal Cooling ---- Cooling Nernber Unit lb Unit l .~ I~ Cooling ------Unit la Figure 4. _ ons ."-- '"" --- of Brooks (1956), HcJannet (1957), Hallace (1975), f"~=nt l and the present study, as modified from ~-.'al1ace (1975). Buckhorn Red Rock Basal Portion Tule Peak Hine Canyon of Hartford Hill Rhyolite Section Section Section .Present McJannet McJannet HcJannet Study (1957) (1957) (1957) Hine Canyon / ~1embe r Hine / / ,.... N funit F 1 =TUnit E Unit C F + . Unit B Base Not Exposed Bas Figure 5. Correlation chart for McJannet's (1957) basal member of Tule Peak Formation·and basal part of the Hartford Hill Rhyolite (this report). -·------.HARTFORD II [LL RIIYOL---- I TE J\ND TRUCKJ::E I'ORMJ\TTON, NEVADA AND CALI.FORNT/\ Minor amounts of volcanic and plutonic rock fragments, as well as ~~~~, ;Jre rresent in the groundmass. The units, 0,2IlW-~J~.eQ. ,at the base to moder :tll'ly welded The base of the unit is exposed as a white to light-gray, poorly indurated slope former, up to 20 ft thick. The upper portion stands out as a well~indurated cliff former, medium pinkish red in color in Mine Canyon and light gray to reddish tan in exposures on Petersen Mountain. Along the west flank of Petersen Mountain, the unit is at the base of the section and lies unconformably on quartz diorite basement. It is exposed here only at the Buckhorn mine and in Red Rock Canyon. In the Virginia Mountains, the unit is exposed in a 75-ft-deep gorge ~t the bottom of Mine Canyon. Cooling Unit la correlates with McJannet's units A and Band ap pears to be a simple cooling unit. The radiometric background of this unit is 160 to 280 cps. Cooling Unit lb. Cooling Unit lb is a vit:ti~ •. tQ..,Jl-i.tr.iJ;;.:-Crystal tuff of rhyolitic to andesitic composition. Phenocrysts, composing 4 percent to 35 percent of the rock, are quartz (0 to 12 percent), K-feldspar (4 to 89 percent), plagioclase (8 to 84 percent), and biotite (0 to 22 percent). Abundant fragments of volcanic rocks are present in the groundmass, with white pumice fragments especially abundant in the lower part. Shards are present throughout the unit. The lower part is gen erally nonwelded, whereas some parts near the center of the flow are moderately to densely welded. The upper part of the flow is generally moderately welded, but some zones show no welding. Approximately 425 ft of the unit is exposed in Mine Canyon, and approximately 250 ft is exposed on the west flank of Petersen Mountain. Tn outcrop the lower portion of the unit is a light- to medium-gray, poorly indurated slope former up to 125 ft thick. It may be a multiple flow unit on the basis of what appear to be ground surge features be- low densely welded parts. It commonly overlaps Cooling Unit la and lies unconformably upon basement rock. Where Cooling Unit la is present, Cooling Unit lb generally appears to be in conformable contact with it; however, in Red Rock Canyon (SE~SE~ sec. 30, T. 24 N., R. 18 E.) the contact between Cooling Unit la and Cooling Unit lb is an angular un conformity, and an arkosic sandstone is overlain by a basaltic mud flow at the base of Cooling Unit lb. The upper portion of Cooling Unit lb crops out as a yellow-tan to dark reddish-brown cliff former, commonly well indurated. It appears to be composed of several flows, ranging in total thickness from 0 to 375 ft, with individual flows of a limited extent. The lower portion of Cooling Unit lb correlates with McJannet's (1957) units C and D and was identified throughout the project area. The upper portion correlates with McJannet's (1957) units E, F, and G and Brooks' (1956) units A and U. Cooling Unit lb appears to bea compound cooling unit. 13 li/\HTFOH.D Hl!.L tmYOLITE AND TRUCKEE FORMi\Tl.ONz NEVADA AND CALlFORN~ All uranium deposits found in the Hartford Hill Rhyplite on Peter sen Mountain, Seven Lakes Mountain, and Hungry Valley are in Cooling Unit lb or at its contacts with overlying or underlying units. The radiometric background of this ynit is 130 to 275 cps. An age date for unit lb.in Mine Canyon was 27.9 ± 0.8 m.y. (Wallace, 1975, p. 19). Cooling Unit 2 Cooling Unit 2 is a vitric tuff of rhyolitic composition. Pheno crysts, composing 2 percent to 11 percent of the rock, are quartz (0 to 5 percent), K-feldspar (76 to 93 percent), plagioclase (2 to 14 percent), and biotite (0 to 1~ percent). Rocks in the middle of the unit generally have a groundmass consisting of abundant, black, flat tened pumice fragments and glass shards. The unit, which is moderately to densely welded, ranges in thickness from 120 ft in Mine Canyon to approximately 500 ft in Red Rock Canyon. In outcrop the unit is a light- to dark-gray cliff former with some medium reddish-brown portions. Black-streaked pumice fragments are distinctive for this unit and, although generally found near the middle of the unit, are also found at its base at Petersen Mountain. Cooling Unit 2 is exposed on the west flank of Petersen Mountain, in Red Rock Canyon, in the north end of Spanish Springs Valley, and in Mine Canyon and Rainbow Canyon, and was tentatively identified on Dogskin Mountain. It is easily recognizable because of the black pumice fragments mentioned above. The contact between Cooling Unit 2 and Cooling Unit 1 is noticeably unconformable in the Virginia Mountains. A basaltic mud flow.is present at the base where the unit crops out below the Red Bluff prospect. In sec. 31, T. 24 N., R. 21 E., unit 2 flowed around a hill of Cooling Unit lb and into a paleostream channel eroded into Cooling Unit lb. This unit ranges in thickness from 0 ft at the paleohill to 200 ft at the paleostream channel. Cooling Unit 2 correlates with McJannet's (1957) units Hand I of the Basal Member, with Mine Canyon Member, and with Brooks' (1956) unit B. It appears to be a simple cooling unit with a radiometric back ground of 225 to 325 cps. Cooling Unit 3 Cooling Unit 3 is a vitric to crystal tuff ranging in composition from predominantly rhyolitic to rhyodacitic. Phenocrysts compose 6 percent to 72 percent and consist of quartz (0 to 80 percent), K-feldspar (20 to 100 percent), plagioclase (0 to 67 percent), and biotite (0 to 15 percent). The groundmass commonly has minor fragments of volcanic and plutonic rocks with some pumice fragments. Glass shards are present, but 14 much of the rock has been altered nnd the shards devitrifled. The unit Is lightly to moderately welded with some densely welded areas. lt .is 0 to 150 ft thick on Petersen Mount.1in and In Red Rock Canyon, and 1.50 to JSO ft thick in the Virginia Mountains. In outcrop tlte lower portion o[ unit 3 is a lightly welded slope former of light-gray to light-tan color. It ranges in thickness from 50 ft at the Maue-McCray prospect to approximately 200 ft at the Arm strong mjne. At the base are zones of abundant partially silicified wood fragments and evidence of ground surge. The unit is devitrifled as the result of secondary alteration, probably caused by circulating ground water. The upper portion of unit 3 is a moderately to densely welded cliff former with honeycomb structure. It is medium to dark reddish.:... brown in color with minor zones of light to medium gray. This upper portion is rich in bipyramidal quartz crystals, has abundant K-feldspar with blue chatoyancy, and shows evidence of primary devitrification. The high crystal content and chatoyancy, in combination with the reddish-brown color and honeycomb structure, is distinctive for the upper portion of Cooling Unit 3. It is approx imately 200 ft thick in the Virginia Mountains and is only partially exposed on Petersen Mountain. Bonham (1975, oral cornmun.) separated Cooling Unit 3 into upper and lower portions on the basis of primary and secondary devitrifi cation. The contact between the two portions was established where primary devitrification of the upper portion stopped its downward migration during the cooling period. Secondary alteration is pre dominant in the lower portion, whereas the upper portion exhibits both primary and secondary alteration. Cooling Unit 3 is exposed in the Pah Rah Range, Virginia Mountains, Dogskin Mountains, Seven Lakes Mountain, and Petersen Mountain. The unit is generally easily recognized except at the north end of the Pah Rah Range and the north end of Dogskin Mountain, where it is crystal poor. In the Pyramid mining district, on the north end of the Pah Rah Range, the unit has been intensely altered by mineralizing solutions. Cooling Unit 3 correlates with Brooks' (1956) units C and D, Mc Jannet' s (195 7) Pumice Member and Crystal Tuff Member, and Wallace's (1975) Cooling Unit 3. The unit appears to li~ conformably on Cooling Unit 2. At the Hed ID11ff nnd Maul'-McCray prospects in Mine Canyon, however, the contact I:; m;1rked hy a haHaltlc mud []ow that. may lndJcatc an l'roslonal h!ntus. Cooll11)\ UnLL :3 appl'ars to he a simple cooling unlt. All uranium de posits found in the Hartford Hill Rhyolite on Dogskin Mountain and in the Virginia Mountains are in Cooling Unit 3. The radiometric back ground of this unit is 200 to 425 cps. 15 HARTFORD HILL RJIYOL lTE AND TRUCKEE FORMATION, NEVADA AND _CALli~~~ Rainbow Canyon Member The Rainbow Canyon Member is a vitric to vitric-crystal, ash flow tuff cooling unit of rhyolitic to andesitic composition. Pheno crysts compose 15 percent to 30 percent of the rock and consist of quartz (16 to 67 percent), 'K-feldspar (8 to 66 percent), plagioclase (11 to 29 percent), and bfotite (8 to 12 percent). The groundmass contains minor litl1ic and pumice fragments. Glass shards are also present but many of them are devitrified. The member, nonwelded to lightly welded, is 320 ft thick at Rainbow Canyon. In outcrop, the Rainbow Canyon Member forms a series of ledges and slopes that are lightly to moderately indurated. It ranges in color from grayish orange pink at the base to reddish brown at the top. A distinctive 8-ft-thick ledge in the middle of the member is nearly continuous throughout the area. The Rainbow Canyon Member is present in the Pah Rah Range, Virginia Mountains, and at the north end of Dogskin Mountain. This member is also intensely altered in the Pyramid mining district. The Rainbow Canyon Member is the same as Brooks' (1956) units E, F, G, and H; HcJannet's (1957) Rainbow Canyon Member; and Wallace's (1975) Cooling Unit 4. This member, a compound cooling unit, confor . mably overlies Cooling Unit 3. The radiometric background is 17 5 to 275 cps. Maue-McCray Member The Maue-McCray Member appears to be an avalanche deposit. It is polylithic, composed of rocks from older members of the Hartford Hill Rhyolite, brecciated lava flows petrologically similar to the so-called Kate Peak intrusives in Mullen Pass, and basaltic mud flows. In the Virginia Mountains, the member averages 225 ft in thickness, with some expo~ures at least 325 ft thick. In the Virginia Mountains, the member is light gray to dark purple in color and forms an irregular series of slopes and ledges. Abundant blocks of reddish-brown Cooling Unit 3 are scattered throughout the member. Exposures of the Maue-McCray Member in the Pah Rah Range are dif ficult to recognlz1' because of alteration associated with the Pyramid mineralization epoch. The member is well exposed in.the Virginia Mountains and is probably present on the north end of Dogskin Mountain. The Maue-McCray Member correlates with Brooks' (1956) units I and J, McJannet's (1957) Maue-McCray Member, and Wallace's (1957) Cooling Unit 5. Wallace incorrectly identified this member as a cooling unit, 16 \ HARTFORD HILL RHYOLITE AND TRUCKEE FORMATION, NEVADA AND CALIFORNIA probably because of the abundant included ash-flow material and the relatively poor exposures. TI1e Maue-McCray Member unconformably over lies the Rainbow Canyon Member. The radiometric background of this member is 150 to 250 cps. ¢ Cascade Member .The Cascade Member is a crystal-vitric tuff of dacitic composition. The phenocrysts, composing 36 to 37 percent of the rock are quartz (11 to 12 percent), K-feldspar (0 percent), plagioclase (72 to 81 percent), biotite (3 to 12 percent), and hornblende (4 to 5 percent). TI1e groundmas~ contains a moderate amount of lithic fragments of vol canic and plutonic origin, abundant pumice fragments, and a few fine glass shards. The degree of welding is slight at the base, increasing toward the top where the member is densely welded, and contains flat tened pum'ice fragments. The member is approximately 400 ft thick. Outcrops of the Cascade Member form slopes in the lower two-thirds with the upper one-third generally forming a cliff. The color ranges from light gray at the base to medium g~ay at the top. The member is well exposed on the west flank of the Virginia Mountains near Rainbow Canyon. It may be present on Dogskin Mountain and in the Pah Rah Range, but exposures were not evident. The Cascade Member correlates with Brooks' (1956) unit K, McJannet's (1957) Cascade Member, and with Wallace's (1975) Cooling Unit 6. The base of this member appears to be conformable with the Maue-McCray Member despite the fact that the Maue-McCray Nember is an avalanche de posit and some degree of unconformity should be expected. The member has the characteristics of a simple cooling unit. The radiometric background of this member is 125 to 200 cps. Two radiometric dates from exposures in Mullen Pass gave ages of 21.6 + 0.6 and 22.6 + 0.7 m.y. (Wallace, 1975, p. 19). Dikes In the Virginia Mountains, the Hartford Hill Rhyolite has been intruded by basalt dikes. These dikes acted as structural controls for the uranium deposits in Mine Canyon and at the Armstrong prospect where they intruded Cooling Units 2 and 3 and the Rainbow Canyon Member; they must also intrude Cooling Units la and lb. No dikes were found in any member above the Rainbow Canyon Member. The dikes were probably feeders for the overlying Pyramid sequence, but no direct evidence was found to demonHtr:Jte this. 'l11e rad:tometric background on non mlnera l.tzed portlonl:l of the dikes is 100 to 250 cps. 17 HARTFORD HILL IUIYOLITE AND TRUCKEE FORMATION, NEV¥JA .AND CALIFORNIA c,~n~~W~ Cooling Unit 1 may belong to a different eruptive sequence than t younger units because it is more mafic in composition ~han the over lying cooling units, and an unconformity exists at the base of Cooling Unit 2. Rock units from Cooling Unit 2 through the Rainbo~ Canyon Member have a normal ch~l.&al,.g.radation f~.~fl,Qw,.,~,U: . ..-.aquence silicic at the base to intermediate at the top - indicating that these younger rocks came from a continuous series of eruptions. !he Maue-McCray Member apparently formed during a period of minor volcanism. Bonham (1975, oral commun.) believes it probably formed on the ri.m,.Q,f,.,,tfilo."~.a.l.Qf.t,3;. !he Cascade Member of the Hartford Hill Rhyolite represents the last volcanic eruptive sequence of the series in this area. All significant U~;iQjla.,~i.~.,in ,tl}~.. l?t::,<;>Je.ct ar;,~ are within Cooling Units .1.1;> Q~ .J.: Both of these units have relati~~J,y ;~Qae~ble b9SeJ;i, rest on basement or moderately to densely welded ash-flow tuff, have been altere~ .... ~,w.a.t..er, and are capped by moderately to densely welded.."~"~ .~. a.ib..{lQW .,w.,f£. Three select samples of lower Cooling Unit 3 contain anomalous uranium: 19 ppm, 17 ppm, and 32 ppm u3o8 • STRATIGRAPHY OF THE :!liitU!iii,,,.li'~TION The Truckee Formation in the project area ranges in lithology from fluviati.J..i .s~~";:i.W,..4 .~;t~Q&~r~t~. Long Valley In Long Valley the Truckee Formation consists of a series of alternating fluvi~~~,,~, lat;;~s;~~ne 1 ,se4;i~ts. bou,~~e:( b,eds,. tuffs~. The lower 100 ft of the stratigraphic section in Long Valley cons sts of lithic and arkosic sandstones and wackes primarily derived from the 18 11/\H.TFORD HILL RHYOI. J'l'g AND TRUCKEE FORMATION, NEVADA AND CALIFORNl.A L he eros ion of volcanic rocks. The sands tones grade upward into .· tuffnceous sands and silty sands interbedded with tuffs. The. upper ;>nc-third of the section is composed of quartzitlc snnd~tonc dcriyed from plutonic rocks. Most of the sandstones have faint to moderate cross-bedding and a cut-and-fill structure characteristic of stre•m channels. Bo~~~.~S b~ .. ,,~,,~Q.~ ,,tt,Ji~~,£,1< are common throughout the sect~on. Granitic bouiders, up to 20 ft ~n diameter, are embedded in a sand and clay matrix. Some boulder beds grade laterally into sandstone, as at the Red Rock Canyon prospect. The boulder beds are mudflow der posits and appear to have been derived from the west. Clay beds (1 in. to 5 ft thick) in the basal sands. contain organi~'' n;:~te'f'i~l~"''"~~e'r'al prospects are located in areas where yhe. organic material has been enriched in uranium. In sees. 19 and 30, T. 23 N., R. 18 E., a ba~.~{t,2,lrl..,§eparaites the Hartford Hill Rhyolite from beds of the Truckee Formation. It is conformable with the Truckee Formation. On the east and west sides of Long Valley, the Truckee Formation lies unconformably on basement rock. On the east side of the va~ley the Truckee lies unconformably on Hartford Hill Rhyolite. The r~dio metric background of the formation in Long Valley is 80 to 150 q~s. Hungry Valley and Warm Springs Valley The Truckee Formation in Hungry Valley and Warm Springs Val]jey is predominantly a l~"lllepesit:••"W'!:~ .. ~!!-a'l.·"Bandstone and ,con glomerate unit. One rhyo!"ft'! A basal .l;9~QJBiaillirfMi·i.&'~.~c material, approximat,ly 20 ft thick, grades upward into a sandstone composed of volcanic and plutonic material ·approximately 100 ft thick. This sandstone grades upward into silts and clays. There is no apparent cross-' bedding, but paleostream channels filled with coarse arkosic ' sandstone were found in the lake-bed sequence. One channel cont~ined a radioactive bone fragment. · · Hartford Hill Rhyolite underlies the Truckee Formation uncom formably on the east side of the valleys. On the west side of the . ·va I.lcys the formation unconformably overlies basement rocks. The rndiometric background ~f the Truckee Formation in these two valleys ranges from 50 to 125 cps. HARTFORD HILL RHYOLITE AND TRUCKEE FORMATION, NEVADA AND CALIFPRNIA s q;y.ctw? e Benham (1969, p. 43) believes the pro.ject area is in a ~r~n~- i ti~nal zon"~,.~et;::.,;~~he ...?+~t;J:,f:l ij~v,~~ P+·~~~tQ,.th~ 1111 :fess,. anbp t11e Bas 1n and .. ~e. P+~'{Jr.PS~ t.o,, t,he.. e.a&,t. It l.S also loca~ . .(l.t t e northwest end of,,,W~:t. WP,~.,,..,P,l?,f,~~.~EJEf~!ill:" zone that paralj~els the southern Nevada-California boundary. { There is evidence thjat large magnitude noQWJ,.. ~~~H~~ .. q:::.e,9~ng nprth and northeast, ~rder most of the mountain ranges in the '?rea. In the Virginia Mouqjtains, faults of la-s~~ .~i~Ce,lll.~Q.t, ..• w:i..t.h J;ela.tU.··~ 1'91\~s, long lin~nr ' ridges, and s~nll;os1t~. \i~.... t~ .. Jill~fJ,..Qne~ by Bridwell (1975) as in~icative I of strike-sl!p movement. Wallace (1975, p. 57) described an area on the east side:of the project area as dominated by northwest- to west-trending faul~s that mainly affect the Hartford Hill Rhyolite or older rocks. Faults of this system appear to have had the greatest effect on the top~graphy , of the Virginia Mountains, Dogskin Mountain, Pah Rah Range, al)d Warm Springs Valley. Faults of this system are found elsewhere in·· the project area but their effect on the topography is minor. Northeast-trending faults are evident throughout the project ar and have had movement of large magnitude. They have had greatest ef ct on the t~Q.x ,,in the central and western part of the area~ The I topograpb,~l:.;,,~iiaiWi..,_.,.-;,.EeJ:ersen Mountain, Long Valley, H~gry Mountain, Hungry Valley, and Spanish Springs Valley afl@••i!'4!'hn.,a co faults.9~~·~.l;!,~. ~~~Ill· BasaJ.t:.d}~,f1S, have followed this trend in the Virginia Mountains. Mullen Pass also probably lies on this fault system. Although no faults are apparent on the surface in Lou.g,V.blley and Hungry Valley, it seems likely that north- to northwest-trending faults are present (such as at the mouth of Hungry Valley) anp have repeated sections of the Truckee Formation. Beds of the TrucJi.!i~J;;g.~ti..9~r:td ..1;1H.f..~~ of the Hartford ~ill Rhyolite are not fol,g~~~.tt.• UHa,.m;i.~ .. ~J.Q.s_related to faUI(lting. The formation was deposit~ .. ,,~&,,.~.~~.~JQ.IJJ. l.i.&ht to moderate relief. Hills or loJ!f J)lH!:!Blflii1 ranges of basement rock appea·d to hav been present in the area. S,J;!~~~;., tQ,Qllr.Sl£~V>.,~~r~... deposit;ed over ! and around these, with younger units OV.jiiil.i.m?;hU,&,.th~,_':?.lder oQ1es. 1 Shortly before .tl;l.,-.,IfJJ...~~~ .. f.9...W.2.1;:i2n was deposited, the cent~r of th area began to dome.,.J,W~.; ,.,J;,l;M~., •.1W.lJ..tt. .coati aued through.,,lJ;,JJ..C,*-e .. time As a result of the c:J.s?~ ... units of the Hartford Hill Rhyolite were tilted 40° to 60° W. on the west flank of Petersen Mountain, 10° to 15 ° N. on Seven Lakes Mountain and Dogs kin Mountain, and 40° to 50° 1 W. on the east side of Hungry Valley. On the south end of Hungry · Valley the dip is 5° to 10° S. ln the Virginia Mountains thci dip is! 5° to 10° SE.; it is 0° to 10° N. in the Pah Rah Range and iq the unnamed mountains bordering Spanish Springs Valley. However~ on the 1 west side of the northern end of the Pah Rah Range, the unitd dip 30° to 50° W. into Warm Springs Valley. Where the formations are in normal contact with each other, beds of the Truckee Forma,ion 20 HARTFORD HILL lUIYOLlTE AND TRUCKEE FORMATION, NEVADA AND CALIFORN~.,· dip the same direction as the Hartford Hill Rhyolite, but dips in the Truckee Formation are generally 10° to 20° les·s than in the undcrljing units of the Hartford Hill Rhyolite~ ~ l 111e ccn•.. ~.:f,.2,£.,;o,.~ !~.~,~~a"·~-,~~,a..~"""~' ~~• .,<;! ... l>.p~~trtb.i..<;\, ~£!}]£_,,~ 1t ).rf ani JL i c hasc~cq.t ~ock·.·' .w· itll .rc.. cen.t .•.. a.ll.···I··· u···.. v. iun~. t1.l11.ng tne valleys. Exposurcli·1• of the Truck,e~... i~.~,n,~t.ti_~r.tf Hany of the urant~..Q~~§.j.t§.,,.Q..t,~,t~,,area are controlled by, .,et' u,~ture as well as b¥,,.l,iL~PJ.~... North to northeast £'fiii!G.Ii.-...-•-.··"• .. s localized Y;uluil.l.m.wm~.Qii:~ .~be. .. ~i.ftia Mountains, Dogskin Moun1 ains, Hungry Valley, and Petersen Mountain. Northwest-trending faults t,~rminat ma.ny of the deposits. The Seven Lakes Mountain, Tick Canyon, and ~ost Pardners prospects are on northwest- to west-trending faults. . ' - ~-. ~~:;:;, '~i?i·~~ I Sky Lah.~~~~~~"'~~l~,,J~~~- that enqjpm- passes most of the project area. Wallace (1975, discounts j~eteor impact as the origin of the feature and suggests it was formed ei9her by volcanic-tectonic events or by intersection of structur~l trenct.ss, such as the Walker Lane intersection with the Mullen Pass zone. 1he general size and configuration lead to the speculation that this ' feature may be the surfJi,lil,~.~~~.~... ~£~aldera. If l[lthe feature is ~" x~.§.1!I~~,n.t~l1ta:a., .... a...wnnher of geologic events can b~ ex plained by using Smith and Bailey's (196~}.,_§g.wJ,~~~l? of cauldrqn format ion descrj,~.Q,,Qc,•••.. m The chemi~p,,rgh_lem in th~-H:;r'dord ~ill Rhyolite (more andesitic ash-flow tuffs of Cooling Unit 1 being o-.terlain ~ by silicic cooling unit, a reversal of what would be expected in 1 continuous erupt1.'on···· o. f. ash-flow.. u.. n. its) can be explained as.,...tJ,m~.¥1··... 'J~ples in the tappin&... Q.L,tl;l .. ~ •. ,;w.~~~~~Q.e,r._, with enough time passing bet. een the eruption of Cooling Units lb and 2 for the magma to further d :f fcrentlate. ~~ I The following is a Stage-by-stage description.of events~M~e suppo~.~·~·~<,c;~~~~~~ .. ,.~J.rim· ... Stage 1: Regional tumescence and propagation of ring fractures .. At this time the more basic ash-flow tuffs of Cooling Units la tnd lb were erupted. 1': Stage II: Major ash-flow eruptions. Following a period of erosi~n on the surface of Cooling Unit lb and differentiation in the! magma chamber, Cooli~g Units 2 and 3 and the Rainbow Canyon 1: Menilier were erupted. . !i! Stage Ill: Caldera collapse. This event formed the general shapf of the circular feature on the Sky Lab photograph, the boundary I~ of which is shown on Figure 1. •' 21 !.!_A_I_~:YOR"Q...... ll[LL RHYOLITE AND '_l:_J~UCKEii_l~ORMATION, NI~:VADA AND CALIFORNlA Stage IV: Minor pyroclastic eruptions and eruption of the lava on the caldera floor. During t~is stage the avalanche deposits of the Mauc-McCray MembL~r and lava flows associated with the intrusions of the Kate Peak intrusives at Mullen Pass formed at the ring fracture zone and on the caldera walls. Stage V: Resurgence doming. This stage formed the structural dome evident in the area while Truckee Formation sediments and volcanics began to fill the "moat" forming around the dome. Parts of Warm Springs Valley, Hungry Valley, Lemmon Valley, and Long Valley are the depressions that made up the moat. Stage VI: Reopening of ring fractures. At this time, the Cascade Member was erupted while the Truckee Formation was being deposited. Stage VII: Hydrothermal activity or fumarolic and hot spring activity. This activity occurred during all the other stages and continued long after other processes of caldera formation had stopped. This stage may account for some of the precious metal deposits in the area, as well as for the mobilization of the uranium from the tuffs and basement rocks into the ground-water systems of the area. Following these J;.~~J!E.!'L Jll()VCJ:l1~nt.s, 9:!~n$ Walker Lane structures may have displaced the.•in@-£E.a&t!!.l.74i ,a,~t:~m, Extensive field work will be required to prove or disprove this hypothesis. It is interesting to note that all uranium deposits in the area are either in or close to the proposed ring fracture zone, or inside it around the structural dome of basement rock. U~~ .. JJ~QSITS HARTFORD HILL RHYOLITE Urani..l1IJ1 .. d~¥,e.. ~!!Hl:! in the Hartford Hill Rhyolite are primarily strat-. igraphicalJ.¥., ~Q,g,f,~Ql,AA,Q...,,.Ji;k:J;;,l;l~~cou4a,ry control exerc,:j.~e4.~.Y .,f~ ture sy•~' carbog.;i..~.,~QQ4,, Q.~Q.. t'.~, ~d ba-.al.,tkc;. (.!:ij(es. All of the known deposits, with one exception, are confined to Cooling Units lb and 3, and are locali~~d-l:"{~,t.J'lj~ •. ,~l'l~.... l:J,ap~q.. J:lOpweJR~.d p}lm.B:S!79.us. poJ;,1;:ign near contacts w,it-,1:>. ove,t.l¥.4J,g .. a.ud ....JJA!ierlyin,g., mo ;t;.~ weJ,ded port ions. W.W,ded members that ;ax;.a~Mect~¥'M •.,.., .• :L89'··'11l'ifl.ertMriaed independently near these contacts. Uranium prospects in the Hartford Hill Rhyolite are listed in Figure 1 and in Appendix A. Geologic maps of specific prospects are in Appendix B. 22 l . 11/\R'I'I'OitD I!LLL HI!YOLI.'I'E AND TRUCKEE FORMATlON, NEVADA AND CALIFORNIA ·--·-- --'< ~.-·W--E4\!.i: · _, ff.J11"Jdti«$$?i'Wi¥·\l!·ftfffftt 1&~&$'-·M _.~ ---· Several major dcpqsits and numerous minor ones are related to frnclu:t;~ .. syst~ITI~ .W:lthin ~e,l,ded and nonwelded portions of Cooling Units lb and 3. A majp,t,md,lii!PO!iit. the Buckhorn mine, is located on th(' west flank of Petersen Mountain on the Californi:1-Nevadn border (1 1ig.l). The dq~o~i,t is }n one of the most complete Rections of Cooling Units la and 't'o found outside of the Red Rock Canyon area (Fig. IH). A local erop..;b~~.,J;.~~J;.~nt in the Petersen Mountain gr:modi.or i.te core !Jl Lq~.~R9~,1,t}(?I1 of increasesJ,,,th icknesses of . Cooling Units la and lb. Two adits were driven on either side of a southeast-trending ridge to intercept downdip extensions of surface radiometric anomalies. An anomaly was found in the west adit, but not in the east adit. Numerous roads and trenches were cut to deter mine the lateral extent of these anomalies. Disseminated guPIA!it:e, uranophane, and aut~t;.~ .. in narrow, iron-stained, silicifiedtveiulets were reported by Hetland (1955). The total thickness of Cooling Units Ia and lh increases to about 400 ft at the mine area and thins. to 150 ft J/2 mile north, where Cooling Unit la is not exposed. Erosion resistnnt devitrified welded portions of Cooling Units la and lb form prominent north-trending flatirons that dip 40° to 50° W. Tl1e Truckee Formation unconformably overlies the upper welded portion of Cooling Unit lb just west of the mine area. Radiomet.r.;ic,~iiiJJ.d..."!;;.b~;bs.aJ uranium values delineate two linear anomalies .. A similar anomaly on the east side of the ridge extends for 400 ft along fractured exposures of the welded upper portion of Cooling Unit la and below the contact with Cooling Unit lb. The highest uranium cqpce.J.t"'~p1,1s (20Q,,,PJUl~•• l~~o,Q,,.~.lJj.O~),,.are in a 50-sq-ft area south of the east adit portal. Elon&4~-~R):}.. ,9JJ"lt.h~r anomalies reflects distributiou of sample points along the,,B!;,t).. ~,e"~'~'~Wilures. The width could not be detcrmin~d because of the cover, but probably does not exceed 50 ft. llown Uraniu~.m~Q,~Ii/J~ are also found in northeast-tren~;i.l.~. ,t*,;.;,ctures at LIH· Haue-McCray prospect in the Mine Canyon area (Fig. 1). A trench about 23 1101 I &bd 5 U1 I 22 OJ£ as 30 ft wide and 200 ft long, near the contact of the lower pumice member of Cooling Unit 3 and underlying intensely welded Cooling llntt 2, exposes rracturcs that trend N. 34° E. nnd N. 60° W. with moderate light-greenish alteration. The wallrock is silicified along the fractures and is locally altered to clay with minor iron staining. A select sample from a fracture contained 0.13 percent U308. Nu~n>.~P.)!rLnor deposits related .. t,g ...f,t The fra~tw;:,~.,.~s;~~.!!s,,~ with strikes of north to northeast to east, are probably t'T:e result.Q,i.t:e.U$.ional.,~e.aUA& .tl.~r.allel to directions of majo.I.,l,i:J.Ult..;i,}l,g.Jn th~ Pyrami4Lake area (Wallace, 1975). In a majority of these fracture systems, deposits of uranium lll,lnerals are also found at in,J,;J~rf;l.,e.&;,t;i.o,p,s'""w.it:.b,.and al,Q.ng, conjugate sets~.f joints. Deposits not related to major faulting may have been localized by part ing surfaces which were caused by contraction during cooling, or by laminar flow. Appar~ntly~.""t;~.J.11,S!,l.QI'!d portions of the cooling unit were so impervio~.~..... tuat_.,g;t;,w.w,d ,,,x{g,t;.e.;r;;a,.,UlQ.~· -~~ugh nonwelded portions ·concentrated Ut:ijJ~yl,.,io!J.§.,,.Q,.ul.Y.,"xW~~ ft.;;tctures opened the rock and increased the surface exposure in the welded portion. Cl4Ys in the fracture gouge may have f~... ~w.e uranium. At the Tick Canyon prospect on Dogskin Mountain (Fig. 1), uranium minerals are. confin&i.-~o.,a. fault gou~~.another indication of the affiu.ity.. .Qf. .. cl.ays for uranium ions. This prospect may have produced a small unknown amount of ore from a 5-ft-wide, northwest-trending fault contact between the lower and upper portions of Cooling Unit 3. R~;j,J;)..Q.~J;,i)l,j,Jy ~at the Flagg Section prospect in the Pah Rah Range was reportedly associated with joipt~ and fractures in a fault brec~cia zone (Bonham, 1969, p. 86). Exami~~tfon' orthis prospect indicated an anomalous :ru~,~.J,c, ?;gn$ij ...R,J;:,..i;l.X~he deposit, between welded and non welded portions of the Maue-McCray Member. This deposit-is the only known ur~nium occurrence in the Hartford Hill Rhyolif~""n~t· in or ad- jacent to ~:i.ng~~'trf''d'f""'~: '·'' .._.,,,..' Deposits not found during this project, but reported to be associated with fault zones or fracture systems, include the Hopeless prospect and Bing group in the Pyramid mining district and the Golden Eagle claims on Dogskin Mountain (Garside, 1973, p. 99-101). Deposits Related to OrJ;,f.Uli~ .. J?~ji!F;is In some areas, Cooling Units lb and 3 co~ .,e;;tx;l;>.o.naceous stringers -.-. 24 11/\lrl'l•'OlW lllLL RHYOLITE i\ND TRUCKEE FOl\MATION, NEVi\Di\ AND Ci\LlFORNii\ i\ deposit of considerable extent is the Divide prospect on Dogskin Mountain (Fig. 1). CharcpaJ, 1111 ,;\Gn~s ~n4 stringers at the base of Cooling Unit '3, ln contact with grnnodiorite, are reported to contain ~.,~0 p.~rcent u3oH (Gnrslde, 1973, .·p·.·.··· .10·2.·.)...... T.he area of rad-ioactivity measures about 700 by 300 ft. A chil);tp~~ 9.~\!U~le from a carbonaceous zone contained 120 ppm uranium, whereas the carbonaceous debris contained 2500 ppm (Holmes, 1972~ p. 30). Excavations at the Hastain prospect, on the west flanks of Petersen Mountn! n, exposed U"(pnj,,U,Ill-CJ.l.li~hed c.a,r~nj.,z'*' woo4 f~ents "Within a 40-ft-thick zone oLth~ bas~,..pumice lapilli member of Cooling Unit lb and above the contact with granodiorite (Fig. B2). The un:i,J ~s highly fractured.~ prQaabJ,.y du4i\ to laminar flow, but autunite is primarily dis seminated within or partly encloses the carbonized wood fragments and does not coat the fracture surfaces. Several composite trench samples across the zone contained lOO.,..pp~ .. I;.P.. ~,5,DQ,.,.,~. u3o8 . Concentrations up to 100 ppm u3o8 were found associated with a yellow to reddish-brown woody layer at the contact with granodiorite. This layer probably is ~~ pal,.ea~pl horizon similar to that which is mineralized at the Barbara "L" and Jeannie "K" prospects within the same geologic environment. De~;>,mposed granodiorite sample!=;near the contact contain uranium values five times greater ·than the pluton, indicating uranium may have been leached from the paleosol and fi~ed ,PY kaq,linized fe.ldspars in the'"'granodiorH'e. The Petrified Tre~ prospect in Spanish Springs Valley contains plant debris, including sificlfied 'and carbonized logs, within the lower portion of Cooling Unit lb in contact with granodiorite and a gneissic pendant (Fig. 1). Carbonhed, wood. fr;:;l~m,~n,.J;.s <;;q~;i,n greater amounts of uranium (190 ppm) than the silicified fragment~ (24 ppm) (Holmes, 1972, p. 30). The Indepen dence Group was not found but reportedly belongs to this type of deposit. Extensive <::?:X:QOQA,~~.QJ.Iq, ~~~.W~- t".Q.!.1tld at the Tick Canyon prospect on Dogskin Mountain and at the Red Bluff prospect in the Virginia Mountains; however, it is not mineralized and these deposits are confined to dominant structural features. i]_epos~:.t~___ Rela ted to Basalt Dikes There are several uraniuii•w.d~~t.a,ia Mine Canyon, on the western flanks of the Virginia Mountains, that are related to a basaltic Hike that intrudes Cooling Units 1, 2, and 3 and the Rainbow Canyon Member of the llartford Hill Rhyolite (Pl. l), These deposits, from south to north, are the 11eLongchamps mine, Red Bluff prospect, Garrett prospect, Penney cl:1ims, and Armstrong mine. Approximately 1,000 lbs of u3o8 were shipped from tl1is area during 1955-1956. The dike trends generally northeast nnd cLips from 60° NW. to near vertical. Although east-trending faults hav(• c1 i sp1 :1ced it both horizontally and vertically, the dik~ is exposed 25 IIAH.TFOIW HILL RIIYOLl'fl': AND FORMATION, NEVADA . ------______.,. ______TRUCKEl~ ., __ _ ANJ!.__(_j\Lli~'O~ti_i_j\ l"t~t· 2,1-+00 ft bo.JJ.~.~.t;.,J:.l:.t~te.S,, Emplacement of the d~ .. ,fx,,.;~,e,tt.U;~d.apd .QJ,:t,ghtly altered the adjacent wall rock. A zone of white ka.Ql;l.uiZ£d. walLrock, 1 to 7 ft wldc, con tains fractures filled with greenish-gray opal, or dark reddish-brown hematite, and thin clay seams, The uranium.is concentrated along the footwall witll.in the~e fractures and seams. '·'samples contain from 800 ppm U30.s t,<;>, +~00 PP!l .. YJ~~at tl!e Garrett prospect (Fig. B8). The dike is commonly altered to a greenish-gray color and is strongly fractured. Fresh exposures are dark gray in color. ,A.l,Jered portions of the dike contain from 34, tQ J.a3 ..p.pjU u3o8 ,.. but concentrations abruptly decrease to near background values away from the dike. Adits were driven along the dike at the DeLongchamps mine, Red Bluff prospect, and Armstrong mine to determine the subsurface extent of the mineralization. At the DeLongchamps mine, several high-grade Ol;~ p.9ds and.stringers \vere mined from a 200 ft adit driven in the upper portion of Cooling Unit 3 (Brooks, 1956, p. 38). Uranium minerals, including a},ltun.ite 111 S.ilb.u.ga 1 i tc, phosph\lo+· At the Armstrong mine, a 40 ft shaft and a short adit encountered n h·actured and altered, 6-ft~wid,~.~lt. ~.that intruded the upper portion of Cooling Unit 3 (Fig. B9). It is only slightly anomalous, in that surface samples taken near the shaft contained 86 ppm u3o8 . Samples from the adit walls (Fig. BlO) contained only 2 to 7 ppm u3o8 . The high-grade ore, reportedly containing over 2.7 percent u3o8 (Bonham, 1969, p. 85), had been entirely removed. Uranium deposits in basal ):>,,illJd~ .. of the,.~uckee ForlV,fltion aie asstH' i <1 tl•d with thin clays contai11in~c[lrb?~aceous debris near the contact wi.th underlying gr;rnotiiorlt'~, and the' ff'artford Hill Rhyolltc. A humic-rich 411/:·!"-'<·~-d' 26 111\RTFORD lULL RHYOLiTE AND TRUCKEE FORHATlON, NIWADA AND CALIFORNIA pal <~osolof post--Tr~c~ceFormation age developed across the same contact; .it contains' fi'i~'i'rff.'{~~i~>E"!iiuranium concentrations. The Bar.bara "L," Jennnie "K," Cornelia "C," Yellow Jacket Croup, and Red Rock Canyon prospects in the Petersen Mountain area; the w.-, mtw~,~,.~~"~l,?r~s Valley; and the Greenstone prospect in Hungry Valley are in the Trw:.~.iii:Jiliiltion and are described below. Several contiguous prospects on the west flanks of Petersen Mountain are at the contac.t,,~ft4,t.~•dss ,Qf ~-~.-lt~~·~e.e Formation in Long Valley and the gronodiorite (Pl. 2). The Tr~Q~ Formation in Long Valley d:J-~1;1 t".,J;,9.~~.J!.~0 "W. and strikes generally N. 10° E. ft unconformably overlies erosional remnants of cooling units of the Hartford Hill Rhyolite. The Barbara ''L" prospect consists of several small pits and trenches that expose a radioa.~~"·~aie:..HM ~~~~flg basa1·-Ga.nds of the Truckee Formation and Cooling Unit 3 of the Hartford Hill Rhyolite. A 4-ft--tb,ick 4Ye.J:-Qf. lm~;;r,;i.l;l;l.. e.p.l.aJ;J.t ..Qebtl.§., iq~.rmixed with clay, silt, and scattered detrital phenocrysts, is anomalous over a 1,000-square- ft area. Samples from a 50-'ft-long trench, which exposed the l~4i· ... ~ich laye1:.,. con tained,,!J.,rs.u;i,J.!JJ,l,_Values.. ~ing_. from O.J•. Z .perceut ... t.o .. D •. ~J.... ~ercent U.3n8 • Chemi_ca;L.,.J,U;A.Q.j,MJll-Y:P.lues for ore-grade material are nearly,.lQ.O .times gre At the Jeannie "K" prospect, anomalous ~iljjjjtw.ii' .. •t+l~ in clays and carbonaceous ,:tlle:ln;:is in the l;J:"\4£.~ ,Ji:o~mation and i~. i9-·~~q~ed p<¥leG80l (Fig. Bll). A mi~imum of ~- f.~ pf .t~~,Q.;-;-~ra.y,.I.r;ucls.e.~ F9rmation sand, dipping 45~ ,,W. unconformably overlies the basal nonwelded unit of Cooling Unit lb. Ura~.~~.li;;-t.o be associated with a 2-;-in. -thick bed of carhonaccou.s u;_..Q. ani!,•-~J.~f.t~~ic.k .slay bed. The clay bed was reported to conta:in disseminated subugalite for at least 100 ft along the strike (C:;Jr:-dde, 1973, p. 101;). A sample from poorly exposed remnants of an ovi·rlying pal.Q~'w't'~ contained 600-'··~·li:D . S;mds of the Truckl'c Pormation exposed downdip within the prospect Jr~ only slightly anomalous, ~V('r 27 a primary source for uranium in Hartford Hill Formation and Truckee formation deposits. Farther to the north, at the Cornelia "C" prospect, stt;;;£.\1.~ uLpplng Tru~~~ Format ion sands inteldiiliddeQ..~~UuJ.I.t,tJ.J..f..ts,,.,4J.re exposed (Fig: "J3ii).''"n~~'""teldspathic sands exhibit fe~&)~~.,.g,,f_iron oxides, in- dicating downt.lip J.ll..!-.JHi1Lti9.~Lflt>J.ktti<,tn§,,.,Jl.!J.t there is Q.P, .. £,V!:.;i<:'l1.rl' of rol_~:SX!l-~.2-~! tet;31.U.9.P• The quartz grains do.;, not appear to be etched, the feldspar and biotite grains are not significatnly altered, and relict pyrite is not evident. TI1e sands .are clearly oxidized, but no evidence was observed to indicate that th~ 8''ectiments''were ever reduced. The reductant responsible for fixing anomalous concentrations of uranium .• -'1::>:-"""~~~as .,__ , ___ -,., at the prospect is tho~h.. ~ .. ~;.t,q,.be 9 •.~~elated to the limit.c~t.),?.~g and marsh .,~X.~:t;.oument previously mentioned. Ur:QPium values averaged 50 pplih:U,* i,p,,..~,t1.}~fs and 2} p_pm in the sands at this locality. At the extreme north end of Petersen Mountain, on the Yellow Jacket claims (Fig. 1), anomalous humi~~~-~,,f.aund within claystones interbedded with tuffaceous sandstones and other clastics of the Truckee Formation. The rich~.,~ from a small series of discontinuous mineralized zones contain~~,-pp,m 0308 . Other minor uranium occurrences are found in the b~l.o.Poftion of the Truckee. Formation at or near the contact with -the und.gx.l,.yi.u.g.,H.a..,tford Hill lijl,}:~t~:·P ''The' Red Rock Canyon prospect on the west flanks of the Seven Lakes Mountain (Fig. 1) contains a thin anomalous clay zone interbedded with arko~,li\iiHidS ,,a~,..bQ14J.~.. ,coQ.glo~Wi:.U·t..es that dip 45 o W. The anomalous clay.>,*Qne... c.gntains disseminated carbon8G4Wii~Wii·~br,.is and can be traced for at least 300 ft along the strike. The zone is within 100 ft of the contact with the Hartford Hill Rhyolite. Equivalent uranium ranged from 42 to 137 ppm. The Greenstone prospect, on the northeast side of Hungry Valley (Fig. 1), consists of several pits and an adit at the contact between the lower portion of Cooling Unit lb and the Truckee Formation. 1he highest .~e,.;U;tt;iJ.lQ.meter counts were in a 20-ft-thick. ha.sa.l"·¥&1QiHt'.i~,~noglo merate associated with dark reddi~ln:;gWQ..i~~c:..t.aip,i,ng, and in a thin greenish band 1rt""Cooling Unit lb, 5 ft below the contact with the Truckee Formation. At the north end of Warm Springs Valley, in the Winnemucca Hills (Fig. 1), a prospect· pit exposed faulte4 •.lr.u.c.kee, :Form The Herbal claims, not found during this project, are reported to contain uranium minerals in discontinuous lenses in micaceous sands and clay beds of the Truckee Formation (Garside, 1973, p. 104). 28 'I'll (. II; I r l r () r l¥1.;J')·~i~l:,'-·~" l·.! ,,,~~--- <~f.·'ii. .i_,._ ,;.•,'-·"- - ~ "'' :-·· ~ rock. llr The 1:~~~ J,Q~,t~oo .. h;l.s,~.. hi&~l·~·U:t"~n~~ fa'IM.)i:ab.i].,\J.y. ~1?. a_, host rock because ( 1) the formation conta.~•· -~.~sume,,,;uld ,,.~Q~],OJ,ll~.rp.te sections that have observable ~~PJJ~.~us. ~~l. aQitJ2t, ~h.~. for.ma~,;i.on is commonly found topogr~~.,,~J;. .. t~~ ..ll llRi\NTUM FA~1Llr:~I~l.A FOR TilEI:~~I,F£.~D IUW...MXO~ITE Most uranium deposits in the Hartford Hill ~yoJ,;i.ty are in Cooling UnLts lb and 3. The deposits are generally controlled by north- to northeast-t;J:;e~~ng,.~liiW·~W~,~--· atRfr';'' but~1.S few are on ~rthwest- to west-trending fractures. The major;S.,ty; .A'-,~a.,~.. -tt~;anium concentrations in Cooling Unit 'l are found along .P,~aJ.,t... Q~!;,.&~ct,9-RQ:Y~ th~.,.,contact with Cooling Unit 2 or at the contact between the upper and lower portions of Cooling Unit J. Othe~~~· are along north- to northeast-trending ir.aet~,~.+es in the same stratigraphic location or at the contact with granitic base ment rocks. The known uranium deposits in Cooling Unit lb are found along north- to northeast-trending ~X:oUii~a.Qii .. where less welded portions of tlte unit are in contact with the more indurated or welded portions or other units. - lJRJ\Nl Uf'-1 Fi\ VORWJ;.I'!'Y._CRTTERIA -~~~~{_):!!!~ TRl~!f!~F I JZQWW.Q~. Basa.(.,.~.A~,.;V)~ .~~.lU.&JJk~1:,£!,.~,sti .. , 29 -~- .... -- ~------~----· ii e e N. Hartford Hill Rhyo! ite-Truckee Fm . . con t ac t : 8 8 ~ f ~X.9.~ a b.!.~ i f ~ s uil abl e host e rttJ.Laaments.-;,.'.'~::~"'--:'·,,·. as descr1bed 1n the text. are present. 0 Areas of younger • sedimentary rock and alluvium '-' 0 ~ und~ r 1,1a,.i.A. P.Y the T ru~'Ke e Fm. : favorable if suitable host environment-s_ JS describeo in the text. are pres~~t. ~ Prospect and or 01 0 mine location _,. -'·"'-..lit· . (; ·~· ~ F1gure- 6. FJvorable areas for uranium exploratiOn. based on favorabi I 1ty cr1teria J•scussed 1n report (Compare With Figure 2: for ~eology). 11/\RTFORD HILL RHYOLITE AND TRUCKEE FORHATION, NEVADA AND CALIFORNIA An unf~htJ&~-~.t,,:Qf.~ the Truckee,.f9...,ion is the ~~eer dips .found in the area. Where measured, the basal units dip 2:0° to r: !):· ·••:"'· ,,:··: . .. ::·:;:-I''Y:•> r; 4J , but dips r lesser magnitude may be found nearer the centers of the valleys. . bscured faults in the val~cys may have brought the, basal units closer to the surface, makin) them accessible for mining. All of the deposits in the Truckee -~'"&~rlit-•· .. ~~aaphically below exposures of Hartford Hill Rhyolite that are more radioactive than normal. ~'· fl··''' ~·i·~t··,:~~if~f ~--~';···"'-·--·--#;o_~:c-~ .-, :.... ljl:fMm"··., ". The presence of paleos.!:;I¥-A~ .• ~.l:J-9-t:Pl;~s. anq 111 ~,::?,tantial amounts of tuffs, also adds to the favorability of this formation. It is es pecially noteworthy that large volumes of the formation are present in the several valleys in the project area. 31 ...... ; ... ~~---- HARTFORD liT LL HIIYOLITE AND TRUCKEE FORMATION, NEV~DA_A_N_D____ --+f_l_<'O__ R_N ___ I_.A_,_ REFERENCES CITED Bonham, H. F., L969, G<>ology and mineral deposits of Washoe Storey Counties, NevaJa: Nevada J.W-. • .w.n.E;i.§,B.JJlJ-,,]0~ p. Br.itlwcll, R. J., 1975, Sinuosity of strike-sUp L!Ult trace Geology, v. 3, no. 11, p. 630-632. Brooks, Howard, 1956, Geolo~ qf .a urapia-"deposit in the VirgiJ.l~fl- t:12~ntJ!l:Lf1s, W.~slJ.p~. County, Nevada [M.S. thesis Reno, Univ. ~vada, 50 p. · Burnett, J. L., and Jennings, C. W., 1965, G~ie-.fUPG£ liforniu, Olaf P. Jenkins edition, Chico Sheet;;,: California Div. nes and Geol. 2° Geol. Quad. Sheet. Butler, J. M., 1958, Physical beneficiation of low-grade urn ores: U.S. Atomic Energy Comm. RM0-2683, Tech. Inf Service, Oak Ridge, Tenn., 134 p. Garside, L. J., 1973, Radioru;;.,t;;.~ye J;Q,i!1~.ra~~~'pccurrences in a: ( Nevada Bur. Mines and Geology Bull. 81, 121 p. Gimlett, J. I., 1967, Gravity study of Warm Springs Valley, Washoe County, Nevada: Nevada Bur. Mines Rept. 15, 31 Hetland, D. L., 1955, Preliminary report on the Buckhorn claims, Washoe County, Nevada, and Lassen County, Calif rnia: U.S. Atomic Energy Comm. RME-2039, Tech. Information Se ice, Oak Ridge, Tenn., 13 p. Holmes, P. J., 1972, Infiltration uranium rleposits in ash tuffs [M.S. thesis]: Reno, trniv. N~~d<1, 65 p. '1!1 McJanne t, G. S . , 19 57, Geolo~,- oLJlle PYl;j~ili Lake-Red Rock '1. Canyon area, Washoe County, Nevada [M.S. thesis]: Los Angeles, Univ. California, 125 p. Smith, R. L., and Bailey, R. A., 1968, Resur~&;.,,,~!,!...+liJrons, n Coats, R. R., Hay, R. L., and Anderson, C. A., eds., St in volcanology: Geol. Soc. America Mem. 116, p. 613-662. Wallace, A. B., 1975~ Geology and mineral 4eposits of t)J.e py id Distric,_~ •. t~outhern Washoe County, Nevada [Ph.D. thesis] Reno, Univ. Nevada, 162 p. 32 APPENDIX A. PROSPECT NAMES, LOCATIONS, PRODUCTION, AND DEVELOPMENT WORK 33 APPENDIX A. PROSPECT NA.1'1ES, LOCATION, PRODUCTION, AND DEv'ELOPHENT WORK ~ames Legal location Production Stratigraphic Development work (Ht. Diablo Base (Tons; per unit (2) and Meridian) cent & lbs. u3o8 ) (l) l. B CCKHOR.t'l ~rr;;E SE~'IE~ sec. 31, 317 Tons Thl Two adits (caved); two shafts An tel ope Range T. 2 3 N., R. 18 E. 0.24 % extensive dozer cuts and (Peterson :'-1ountain) 1490 lbs. trenches; drill holes. area; Hallelujah Junction area 2. BASTIAN PROSPECT NE~SE~ sec. 30' None Th 1 Drill holes; dozer cuts and T. 23 N., R. 18 E. trenches. w .t>- 3. LUCKY DAY PROSPECT SE~E~ sec. 19, None Th 1 15 ft adit; minor dozer cuts; Valley View prospect T. 23 N., R. 18 E. prospect pits. 4. BARBARA "L" PROSPECT NW0lli~ sec. 18, None Tst Shallow pit; trenches; drill Barbara "L" claim; T. 2 3 N. , R. 18 E, holes. Barbarel 5. JE.<\.'INIE "K" PROSPECT NW~SE''4 sec. 7, None Tst Dozer cuts and. trenches. Cornelia C; Jeannie T. 23 N., R. 18 E. "K" claim 6. COR.t'l'ELIA II C" SE~E~ sec. 6, 724 Tons Tst Drill holes; dozer cuts and PROSPECT T. 23 N., R. 18 E. 0.32 % trenches. ··- 7. YELLOI-l JAC:ZET GROL"P ~-~~ sec. 5, None Tst ~linor cuts &~d trenches. P~OSPECT .~. .. 1;',,~~3 ;-!'~~ R~ _18 _E.~ ~· .. - -rerlow-Jacket claims-~·· ·--- • • APPLWIX A. (continued) Names. Legal location Production Stratigraphic Development work (Ht. Diablo Base (Tons; per · unit (2) and l1eridian) cent & lbs. u3o8 ) (l) 8. RED ROCK CA.\10N SE~~;SW\ sec. 30' None Tst Drill holes; dozer cuts. PROSPECT T. 24 u.' R. 18 E. 9. SEVEN LAKES MOUNTAIN sw~~ sec. 27, None Th 1 Dozer cuts and trenches. PROSPECT - T. 24 N., R. 18 E. Crescent claims; Seven Lakes prospect; w Red Rock prospect Vl 10. SUNNYSIDE PROSPECT SH~S'i.J~ sec. 20, None Th 3 Dozer cuts; caved shaft. Sunnyside claims T. 24 N. , R. 19 E. (Nos. 1 and 2) 11. LARA P~OSPECT SH~H~ sec. 29' None Th 3 Dozer cuts, prospect pit. Lara No. 9 claim T. 24 N., R. 19 E 12. LAURA PROSPECT NE~S'.J~ sec . 29, None Th 3 Dozer cuts. . ' Laura (?) claim T. 24 N. , R. 19 E. c· 13. PUP PROSPECT NE~SE~ sec. 29, None Th 3 Prospect pit; dozer cut. Go-Getter' claim; T. 24 N. , R. 19 E. Pup claim 14. TICK CALTIO:;~ PROSPECT SH!.-,..'lE~ sec. 32, 15 Tons Th 3 Shallow inclined shaft; dozer Tick Canyon group T. 24 N., R. 19 E. 0.21 % cuts; pro~p~c:t_ p_it._ (Nos. :G16):_uc; -. Tock claims .----~· .... '' APPENDIX A. (continued) Names Legal location Production Stratigraphic Development work (~t. Diablo Base (Tons; per unit (2) and Heridian) cent & lbs. U308) (1) 15. DIVIDE PROSPECT sw~ sec. 26, None Th 3 Prospect pits and dozer cuts. Divide claims T. 24 N., R. 19 E. (Nos. 0-9) 16. WINNUlUCCA HILLS NE~NE~ sec. 10, None Tst Dozer cuts. PROSPECT T. 23 N., R. 20 E. Double Jack placer w 0' claim 17. DeLONGCHAHPS MIYE NE~'\ll-1!:: sec. 1, 200 Tons Th3 300 ft of underground workings; Red Bluff (nos. 1-7, T 23 N., R. 20 E. 0. 23 % dozer cuts; drill holes. 10,11); Rainbow No. 911 lbs. 8 Fraction; Red Bluff mine 18. RED BLUFF PROSPECT m-1~~ sec. 1, None Th 3 Two adits totaling 100 ft, T. 23 N., R. 20 E. dozer cuts; drill holes. 19. GAJL~ETT PROSPECT S\-l~E~ sec. 36, tione Th 3 Dozer cuts. T. 24 N., R. 20 E. 20. MAUE-acCRAY t Lowary claims; ~laue pits and licCray mine; Lowary group; Lowary mine e e APPE~DIX A.. (continued) Names Legal location Production Stratigraphic Development work (Ht. Diablo Base (Tons; per- unit (2) and Heridian) cent & lbs. U303) (1) 21. PE:mEY CU.I:!S mv~SH~ sec. 31, None Th 3 Prospect pit; dozer cuts. PROSPECT T. 24 N., R. 21 E. 22. ARMSTRONG :-II~E ...... SE~SW!,; sec. 32' 21 Tons Th 3 40 ft shaft; 275 ft of adits; Armstrong claims; T. 24 N., R. 21 E. 0.33% dozer cuts. Penney No. 6 and 138 lbs. w No. 10 clains '-1 2 3. LOST PARD~ERS SH!,;SH~ sec. 24, None Th 3 (?) Prospect pits; dozer cuts. . PROSPECT T. 23 N. , R. 21 E. Lost Partner group; Lost Pardner mine; Lost Partners . 24. FLAGG SECTION NW~SH!,; sec. 35' 16 Tons Thm Adit (caved); prospect pits. PROSPECT T. 2 3 N. , R. 21 E. 0.34% Thunder Bird group 109 lbs. (Nos. 1-15); Thunderbird claims; Flagg Section; Flagg Station 25. GREENSTOXE PROSPECT NH!,;S E~ s e c . 2 7 , None Tst & 45 ft adit; prospect pit and DaisyTfae· cLnms r.=!2 n.. R. a@ s:. Th 1 trenches. --~~c ~--···-·· = ~·-··_. = APPENDIX A. (continued) Names Legal location Production Stratigraphic Development work (Ht. Diablo Base (Tons; per unit (2) and Heridian) cent & lbs. u3o8 ) (1) 26. PETl\EFIED TREE NE~SI.J~ sec. 12, None Th 3 (?) Prospect pits; _dozer cuts. PROSPECT T. 21 N., R. 20 E. Spanish Springs Valley prospect; Petrefied Tree group (Nos. 1-17) w CXl 27. GOOD LUCK PROSPECT NE!---,.NW!-,; sec. 16, None Thl Prospect pit; dozer cuts. Good Luck claims T. 21 N., R. 20 E. (Nos. 1-8) Prospects not found: Herbal claims; Independence group; Golden Eagle, Red Eagle claims; Snap property; Bing group; Hopeless prospect; Unnamed prospect sec. 29, T. 24 N., R. 21 E.; all listed by Garside (1967). (1) Production from records of the U.S. Energy Research and Development Administration. (2) Th 1 - Cooling Unit 1, Hartford Hill Rhyolite. Tst - Truckee Formation. Thm - Maue-~1cCray Member, Hart ford Hill Rhyolite. APPimiHX n. PROSPECT MAPS AND ANALYTICAL RESULTS 39 0 50 100 150 200 --SCALE-- IN FEET rx.~rJ Truckee Formation -5600"' 200-Ft t ograph contour Hartford Hill Rhyolite ~ Cooling Unit lt1 ~ Cut Hartford Hi II ehyol ite .&...l..l.L.J.. F iII Cooling Unit la TTTTTT" [;;iii Shaft . Granodiorite ~ Ad it Contact >- _/ Dump / Contact dashed wherL ~ / / located approximately Road "' Fault ODH Dr i II hoI ~D --- Sample no. and location 4- Strike an dip Figure 81. Buckhorn mine geologic map. 40 !APPENDIX B (continued) Table Bl BUCKHORN HINE Surface R I fl~JL7 7 4.37 7.3 21.. 5 190 LO I f1 I (>92 I h9 'HJ 5 6.60 7.8 21.4 160 10 I(/) 'l L l2 1..90 12.1 2 3. 6 140 10 LblJ'J2 JO 4.81 9.4 24.3 220 10 I (> I (>94 '.i 'J4 5. 2 3 4 7. 2 28.4 1500 10 I fl9/~(> 19 4.29 21.4 23.1 800 10 I (>lJ!~ 7 1.7 4.98 29.0 24.0 500 35 I h 1)t, H 13 5.28 21.. 3 25.7 600 45 I (,rJ49 2J 5.87 28.5 27.7 800 30 I (,C) 'JO 339 6.83 ' 90.9 30.8 1000 10 I fJ tJ ')I 108 7.56 52.8 32.0 900 15 I (> 1) ') 2 55 l. 29 28.7 27.7 600 15 I (JlJ'J J 30 5.11 60.5 26.5 900 30 I (>9 51, 83 5. 70 101..8 30.3 1250 35 I - I f • 'J '> '> 'll.2 6.86 204.1 34.8 1750 35 Jb956 1~80 7. 03 252.1 37.4 3000 30 /(>9)7 407 6. 30 212.6 34.9 1200 20 . ------·------·------~------·------t--- 41 II II APPENDIX B (continued) ... T<~h I 0 Bl (continued) BUCKHORN MINE I Gamma Spectrosco Sur r: cc Equivalent Equivalent Radio :tries S;1mp I• S:unple U308 lPotassium Uranium Tiwrium Val iv !11 t(•rv: Number (ppm) fpercent) (ppm) (ppm) . (q ) (fcvt) 16958 '•1 5. 77 47.3 28.9 10 1(>959 8 6. 79 7.4 21.9 32 10 16960 29 6.80 20.1 23.6 50 •. 25 1(>961 57 7. 39 25.6 26.8 62 /10 16962 49 6.58 26.2 25.2 100 i 1.0 16963 75 7.16 175.3 27.6 500 ' 10 16964 353 6.73 156.7 28.9 100 :: 65 16965 208 6. 36 100.5 27.1 150 t1o 16966 26 6.49 18.7 24.7 75 /15 16967 30 6.60 18.4 25.6 95 16968 64 6.48 42.1 26.2 110 .10 16969 280 5.97 131.0 26.7 80 1: .10 16970 22 1.81 11.9 28.7 ]() 16971 10 5.82 8.2 24.2 10 16972 8 1.72 6.5 26.2 lO 16977 42 5.16 46.4 21.2 lO J6978 27 4.98 54.6 2.7.5 10 16979 8 4.43 7.6 22.8 1 () 42 I! I ' I ~------4----..-~P-~ APPENDIX B SCALE IN FEET Hartford Hi II l1yo I i t e Dump ~ Cnol ing Unit 1 Road . Granodiorite ~ Cut Contact ...... / I ~ Fi II ,5800~ 200-Ft topographic contour e----'- Sample no. and location Figure 82. Bastain prospect geologic map 43 APPENDIX E (continued) Table B2 .. BASTAIN PROSPECT Surf e Gamma Spectroscopy R ------~~-----+------~----~+---- 44 ------·- ---~======:::--ii--+-~~=== APPENtiiX B (continued) 0 50 100 150 200 ----SCALE IN FEET I Basalt dike .-" 1 ~ / Conta~t dash d w11 ere __./ approximately iit ocated Hartford l-lill Rhyolite I ~ cascade Member Yo Fau It . Hartford Hi II R!1yo I it~ ------Road kTEfn~ Maue - McCray Member Cut Hartford Hill Rhyolite ~ ~ Rainbow Canyon Member 2 00- rt topog phic /54001 I conto~r Hartford Hi II Rhyolite ITM Cooling Unit 3 ¥ Dump Hartford Hi II fH1yo I i te Ad it ~ Cooling Unit 2 >- Samp l·e no., ocation Hartford Hill Rhyolite and i1nterval ~ Cooling Unit lb - . Tem pD!r a r y .:angu I at 1on stat i1,on I ' I Figure 83. Oelongchamps mine geologic'map. I 45 I APPENDIX B (continued) Th3 ~----Raise ~~------Timber Th3 [41'• \ Ore pod (mined out) Basaltclike Hartford Hill Rhyolite Cooling Unit 3 D I &0 IOOI'&?O Dri I I hole SCAI.E IN iFffT Figure 84. Geologic plan of Delongc11amps mine allit (mol.lit1e11 from Brooks, 1956). I APPENDIX B (continued) ·I?UO 17577- -17576 2000 17574 540- 2 600 U-•goo 700 600 17573 . I ! . 120V:· Rml1ometr1c reculing in CPS. i 0 50 100 150 200! . r I SCALE IN FEET ~ Samnle intervnl haserl on 1"15"/2 l'i Fq>.nre 85. Rmliometric anrl sample plan of IJelongclwmps mine mlit (mollifle!l from Brooks, 1956). ., APPENDIX B (continued) Table B3 .. DeLONGCILAHPS MINE r c~; ~ · ;nup I '• Samp ll.~ U308 Potassium tl·rv;I( J'Jumbcr (ppm) (percent) r el' t) 16835 8 5.18 9.3 ~-21:.2 400 . 50 16836 9 3.90 15.6 25.3 400 50 16837 10 2. 72 14.3 24.8 ' 300 20 16838 7 1. 73 7.2 9.3 250 20 16839 5 2.09 12.0 21.3 250 10 16858 21 2.12 18.7 8.7 350 10 16859 8 4.34 5.9 17.5 300 20 16860 5 2. 74 5.1 20.4 250 20 16861 8 4.29 9.0 19.3 350 47 16862 10 4. 6 7 10.2 20.7 500 3 16863 34 1.24 26.1 4.5 800 1] 16864 65 1.16 47.3 5.6 llOO 7 16865 850 3.96 570.3 38.6 5000 10 16866 19 4.45 11.7 21.1 500 20 17572 11 3. 78: 8.8 24.6 650 90 17573 90 1.12 80.7 7.6 1900 20 175 74 39 3.95: 38.9 "26. 3 .3200 30 17575 99 0.98 86.5 7.7 3000 40 17576 24 3.87 20.1 23.5 1400 20 17-577 68 1.18 59.0 6.3 1350 ------ 48 ~PPENiliX B (r.ontinuell) --SCALE-- IN FEET Basalt dike Hartford Hi IIi Rhyo I i te Rainbow Canyo~ Member· ' Hartford Hi 11: Rhyolite 1 I I I I I I I I Cooling Unit r : I' I I I I I I I p Hartford Hi IIi Rhyolite Cooling Unit~ · .. Hartford Hill' Rhyolite .. Cooling Unit !liJ em po r a t r i an · Ia t i on tat ion / 5600/ 200-Ft topog~aph i c contour 1 Figu~e · 86. Red Bluff prospect geologic ap~ 49 ~PPINIIIX ll {I:Uillilllll~tll 0 10 20 30 ~(, b_2~~1 Bas a It ell ke ~~11 SCALE IN FEET H --~- 1400 R Figure B7. Geologic, radiometric, and sample plan of Reel Bluff prospect a1J i t s. 50 APPENDIX 8 (continued) Table B4 RI~D BLUFF PROSPECT Gamma Spectroscopy Surface Equivalent Equivalent Radiometries Sample Sample U308 Potassium Uranium Thorium Value Interval Numhl' r (ppm) (percent) (ppm) (ppm) (cps) (feet) 16712 5 3. 73 3.7 16.2 175 10 167JJ 6 2.48 5.5 27.7 225 10 167Jl4 7 4. 36 7.6 21.0 250-325 10 1.6 76!. 10 4.33 6.8 20.0 400 50 16765 80 1.17 67.8 4.6 500 40 1676fi 16 4.54 13.1 20.4 400 50 1681,() 17 3. 02 14.8 37.8 500 40 16841 39 2.94 41.1 33.9 800 43 I h 8L, 3 106 3.14 117.5 39.6 1400 12 16844 49 0.76 43.4 4.1 800 13 I r>H4') 140 1.63 171.3 13.8 1300 15 I(> 81,(> 175 1. 87 202.1 45.0 1800 10 I (>81• 7 21. 2.57 21.3 39.6 900 20 161-)t,l-) 31 2.67 26.1 35.1 450 50 I fi8L1Y lJ 4.32 9.9 20.1 350 20 16850 12 0.84 7.5 3.1 400 12 I (>85 J 11 3. 92 12.2 19.4 350 20 li>H'J~~ 8 2.85 9.7 34.7 400 40 I: lb8'JJ 183 2. 77 181.7 39.8 1200 7 16 8')1. 62 1.. 30 50.0 5.3 500 10 I 51 APPENlHX B (conl lnued) Table B4 (continued) •o RED BLUFF PROSPECT !i rl Gumma Spectroscopy Surface Equivalent Equivalent Radiometries Sample Sample U308 Potassium Uranium Thorium Value lnterval Nttmbcr (ppm) (percent) (ppm) (ppm) (cps) (fcl'l) 16855 109 2. 72 125.8 38.1 1200 10 16856 13 2.84 16.7 34.9 400 50 16857 32 2.42 34.0 21.7 600 75 17578 301 2.06 254.4 48.6 10,000 14 17579 183 1.06 182.7 8.6 5,000 1 J I I 52 SCALE IN FEET ~ Basalt dike _/ Contact Hartford Hi II Rhyolite __/ Fault Rainoow Canyon Memoer ~ 200-Ft topographic /54001 Hartford Hi II· Rhyo I i te contour [Kill Cooling Unit.3 --- Road Hartford Hi II Rhyolite ~ Cooling Unit 2 ''I'tIt I "''""'T"l I Cut Hartford· Hill Rl1yolite ~ Dump Coo I i ng Unit 1o ~ Samp I e nlo., location Hartford Hi II Rhyolite :t=: and i nt elf va I i' Cooling Unit 1a \ '1 Temporary Triangulation 8 station Figure BB. Garrett map. APPENDIX B (continued) T.:1b1e B5 GARRETT PROSPECT Gamma Spectroscopy Surface EquivaTent Equivalent Radiometries Sample Sample U308 Potassium Uranium Thorium Value Interval Number (ppm) (percent) (ppm) (ppm) (cps) (feet) -·· ..---- - 16767 .8 8$;')1 7.8 20.9 250 80 ~ 16768 11 • 3.29 10.3 31.7 300 95 16769 136 2.90 116.7 44.9 1400 10 16 770 64 1.64 46.3 15.6 600 8 lh771 101 2.37 84.4 37.1 600 8 16772 32 1.40 23.4 8.2 500 13 16773 13 1. 67 12.7 11.6 550 13 16774 * 1130 l. 43 887.0 67.2 6500 1 16775 139 1. 81 82.6 40.6 1400 10 ]6 776 35 2.75 12.6 34.8 500 15 16778 6 6.42 6.4 18.1 275 10 I 16779 7 3.25 7.4 30.1 300 35 16780 18 3. 07 17.2 34.8 400 32 16781 26 2.02 31.1 37.8 1100 5 1.6782 46 . 2.01 44.5 13.2 750 15 16783 106 1. 90 88.3 35.2 800 8 16 78!1 6 2.86 6.7 35.1 350 65 16 785 12 3. 7G 12.0 33.9 300 . 30 --·--·-----·. - -- * Located between 16773 and 16775 54 AI'PINUIX IJ (COillillliCll) 0 50 100 150 200 --SCALE-- IN FEET Basalt dike __IV, Fault ~ u le Dump Hartford Hill Rhyolite ~ l rnu Cooling Unit 3 >- Ad it I ,5400/ 200-Ft topographic Sample no. and I ocation contour --- ~ Sllaft I --- Road I l j Figure • 89. Armstrong mine geologic map. ,! l ' 55 ' APPENIIIX H (Cllllllllllllll l Zone Fault 350 Timber Th3 Fault Breccia Fault i l ! ~ Basalt dike Tuff Breccia Hartforll Hill Rhyolite Cooling Unit 3 --·--- 1 50 Rarl i om~tr i c readings in CPS ...... "------1 6934 Sample location Figure 810. Geologic, radiometric, and sample plan of Armstrong mine adit. 56 APPENDIX B (continued) ~ . ..·[ 'l';lh I I' I~(J ARMSTRONG HlNE Surjface Radio1me t rics Sample Sample U308 Potassium V<4luc Interval Numbc r (ppm) (percent) ( ps) (feet) 16909 5 4.46 7.7 15.2 '2qo 10 16910 7 4. 77 6.1 20.6 zh 10 I I 16911 6 4.69 6.9 20.3 2ts · 10 16912 27 4.97 20.7 20.7 8~0 10 16913 86 1.81 63.1 8.8 13~0 10 I L6914 184 4.90 153.3 26,3 zsbo 10 16915 35 5.05 37.5 25.7 5po 10 I 16916 6 4.78 6.0 21.8 2pO 10 I 1691 7 10 1. 50 8.9 8.7 2bo 10 I 16918 19 4.16 13.7 19.3 3~0 10 16919 28 1. 75 27.0 8.6 300 10 .16920 8 3.84 3.2 18.1 joo 10 e I 16934 7 4.65 6.6 20.7 ~so 10 I ]()9 35 5 .65 3.5 21.0 ~50 10 l ()(J)(l 2 1.86 1.1 6.4 ]so 10 I 169 37 4 1.61 1.9 5.6 po 10 ------______.______.~______-+- ___..., _____ 57 ~PPENO\l B (contin~ed) --SCAI.E-- IN FEET ~I I I I I I r e thi\d Truckee F rmation _, I I I I.....J. I I Cu Granodior te Dr II hole. / Contact Du p 200-Ft to agraphic (52001 Sa le no. contour an locati n ---- Road Figure 811 Jeannie "K" prospect geologic ma . 58 ~-~-~ ~ .·" ' ' i • ! APPENDIX B (continued) e I Table B7 JEANNIE; "K" PROSPECT amma Spectroscopy Sur ace Equivalent Equivalent Radio etrics Samp e Sample U308 Potassiu~ Uranium Thorium Va ue Inter'li al Number (ppm) (percent) (ppm) (ppm) (c s) (fee~) 17586 9 1.91 8.6 13.9 3( 0 10 ~ ' 17587 38 2.26 74.3 9.3 7. 0 10 17588 610 1.0 804.2 36.6 24( 0 10! I 17589 87 1. 70 8.8 14.8 5( 0 10 i I 17590 4 1.45 3.2 7.5 5( 0 10' ' ' ' ; I . ' •-a·--"-••-·--·-- ·-·-••---·- - -·· I i 59 l I APPENDIX B (continued) --SCALE-- IN FEET Truckee For Ill I I II LL Fi II e ~:Er;;nJ . tf I I I I I i r Granodiorit ~ Dump .,~ Contact da hetl where Sample no. and locati n ~ approximate y I oc ated 200-Ft top raphic Temp or rszool contour A statio ------Road 0 oH Dr iII II I I I I I I Jlle II...L.J... Cut ~ Strike nd dip of bed Figure Corne I i a ''C'' prospect geologic ap. 60 Sample U308 number potassium (ppm) (percent) (ppm) 16 4.01 4.6 16709 4 4.91 4.9 16710 4 2.93 3.9 1671 I 3 4.22 4.5 16712 5 3.73 3.7 16713 6 2.48 5.5 7.7 16714 7 4.36 7.6 I .0 16715 18 3.50 13.0 6.9 16716 8 4.16 7.5 5.4 16717 9 3.78 6.2 0.2 16718 6 4.62 5.3 8.5 16719 5 3.20 6.1 8.6 16720 6 2.81 3 ..5 I .6 16721 5 3.39 5.7 I .3 16722 6 2.35 3.4 0.3 1672 3 4 2.70 3.9 I .5 Plate 1. of a po E X P L A N AT I 0 .N Geolooic contact,------dashed where inferred JE· ~~ :~~~1 ~I Alluvium Strike and dip u , ...-o---~ Foul!, dashed where inferred u upthrown side D downlhrown side rO..J ~ X: 1 ~ Volcanic rocks Prospect I w z [8] w u Sholl 0 :::!: ~ I e Stratigraphic section sample location I I I I ~ cascade Member I Formation ~Mine Canyon Member . Mud flow - slraliQrophic w II relationship 1000' 0 1000' 2000' 3000' 4000' ~t~---~~~~~~~· ~~·~~~~ ; ~ Rainbow Canyon Member SCALE IN FEET >- I wa: z_~ ~::::! Cool_inQ Unit 3 OI [ffilJ \.!) 0 oa: 0 s~ Cooling Unit 2 I • CooliniJ Unit 1b Cooling Unit 1a ~ Mesozoic baseml!nt ~ Basalt dike JJI of tile Virginia Mountains. I APPENDIX B (continued) .. Table B8 CORNELIA "C" PROSPECT < amma Spectroscopy Surf 1ee Equivalent Equivalent Radiorr ~tries Samp]j Snmple U308 Potnssium . Uranium Thorium Val ie Inter~ 1 Number (ppm) (percent) (ppm) (ppm) (ep ;) (fee~ 17580 33 2.80 32.8 8.10 30C 10 17581 44 0.96 26.5 16.9 25( 10 1~ 17582 56 1.43 44.4 16.4 35( 10 !'W 17583 12 2.54 13.0 9.5 25( 10 ' ! , r • 'I I i I ! -~~' ,; 61 . .. EXPLANATION ~.. Truckee Fm basalt flow I ~I T. z• N. Coolinq IJirii 2 T. 23 N. Cooling Uni I Ia ~·· ~esozoic~ .. basement 1000 1000 . 2000 3000 .0000 SCAlE 1ft FEET ____ .... Geologic contact, dashed where inferred Fault, dashed w.nferred +--' U upthrown side ~nthrown side • ~· Str1Ke and dip "X Prospect -- Stratigraphic section sample locality A B B' c c· Th.lb I 7000' Thlb l-1000· 6000' 6000' 6000' !1000' 0000 !1000' 4000' SAMPLES OF STRATIGRAPHIC SECTION Gommo spectroscopv Chemical Semple Equivalent Equivalent Equivalent Oa number u3 potassium uranium thorium (ppm) (percent) {ppm) {ppm) 16724 6 2.85 3. I 9.8 16725 8 3.15 7.9 .2-L L. ' 16726 8 3.66 5.8 17.1 16727 4 3.80 5.6 17.6 16728 II 3.98 10.0 27.3 16729 2 2.10 ' 2 4 27.4 16730 8 3.72 5.8 18.9 I 16.731 4 4.16 6.8 20.0 16732 10 3.84 9.9 28.7 I 16733 I 6 3.36 7.8 24.3 R 17 E lUI£ Plate 2. Geologic map of a portion of Petersen Mountain •