772 Ore Deposits of the United States, 1933-1967 Part 6 Chap 31 port 6 Chap. 37 Geology and Exploitation of Uranium Depoiits in Utah n3

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FIG. 1. Geologic Map of Lisbon Valley Area, San Juan County, Utah. Part 6 Chap. 37 Geology and Exploitation of Uranium Deposits in Utah n5 n4 Ore Deposits of the United States, 1933-1967 Part 6 Chap. V

EXPLORATION AND MINING HISTORY up to 33 ' feet of Moss Back sandstone and i .. 2 to 8 feet of uranium ore. This discovery estab­ lished the occurrence of uranium ore in the Exploration History and Costs downthrown block northeast of the main Lis. The first discovery of uranium-vanadium ore bon Valley fault at the north end of the anti­ on the Lisbon Valley anticline was made in cline. 1913, at the south end of the anticline, on Present direct drilling costs in the district outcrops of basal Chinle sandstone. In 1948, are about $1.00 to $1.25 per foot for non-core low-grade uranium deposits were discovered rotary drilling and about $5.00 per foot for and developed in upper Cutler sandstone out­ core drilling to depths of about 500 feet. Usu­ crops along the center of the southwest flank ally coring is limited to an interval of about of the anticline. These were the deposits that 40 feet, which includes the gray zone of the attracted Charles Steen to the area. In July basal Moss Back sandstone and the upper few 1952, Steen drilled the famous 70-foot deep feet of the red Cutler sandstone. Radiometric discovery hole on the Mi Vida claim just off logging costs 12 to 15 cents per foot. Costs the Big Buck claims and down dip from the were considerably higher during the period of mines in the Cutler Formation. He en­ major exploration than now. Assuming an countered about 13 feet of uraninite ore in average cost of $3.50 per foot for drilling, · the Moss Back sandstones, about 100 feet including direct and indirect drilling costs, higher stratigraphically than anticipated (1, p. about $7,700,000 has been spent for drilling 5) (2, p. 1). Following this discovery, c1airn in the area. The average discovery and devel­ opment rate, based on production plus ore re- . staking and exploration drilling progressed rap­ v 7)" I idly to the northwest and southeast and con­ serves, has been about 25 pounds U~a per - i tinued with intensity through 1956. During this foot of drilling, at a cost of about 14 cents V ! ensuing period, the following deposits in the per pound U.O. developed. Chinle were discovered by drilling in the north half of the Big Indian ore belt: Standard (Big Mining History and Costs Buck), Little Beaver, Louise, Texwood-Stinko, Ike-Nixon, La Sal, Columbia, San Juan, Cord Vanadium ore production from the Chinle (Jen) , Radon (Hecla), Far West, and North Formation at the Divide and Serviceberry Alice (Figure 2). A peak in exploration was mines in south Lisbon Valley was reported j,. \i reached in 1955, when 647,000 feet of drilling in 1917, 1940, and 1941. These same mines :.§ was reported. By mid-1956, exploration drill­ were reopened in 1948 (1) for their uranium .~ content. Also in 1948, the Big Buck mines r: ing began to taper off. By the end of 1964, ~ over 4500 holes totalling about 2,200,000 feet in the Cutler Formation in Big Indian Valley .... had been drilled in the search for uranium were mined for uranium. Intermittent produc­ ~ on the anticline, and over 3000 holes, spaced tion from these small deposits continued until ~ 1952. In December 1952, Steen shipped the r::: 200 to 500 feet apart, had been drilled within Q first ore from the Mi Vida mine (2, p. 3). oQ the delineated ore belt (Figure 2) . This inten­ .!:;! sity of drilling argues against the existence of Production from the Moss Back sandstone o..l any undiscovered large ore deposits in the beds has ranged from two to six million ~ drilled areas, although a number of small are pounds of U10. per year and reached a peak -S deposits may remain undiscovered. production of over 6,377,000 pounds in Fiscal Q Year 1958, Table 1. Due to the exhaustion -Q. The discovery in 1962 and the mining of uranium ore in 1964 at the Costanza mine of a few of the major ore deposits, the are ~ (Figure 1) in sections 26 and 35, T30S, R25E production rate started dropping in 1960 and ~::s established the existence of uranium ore on has leveled off to about 4,000,000 pounds ~ . ti the northeast side of a hinge fault that has year. " ~ ""pi) ::s I V ~ tile I ../ more than 2000 feet of displacement. This In the central and southern deposi~ I ~ ; I vanadium content is high enough for that I -...... -- ~.gO I -; high angle fault is one of the main bifurcating I ,/ N faults at the south end of the Lisbon Valley metal to be extracted economically. During -... !---- :: - I ---1------; -~ the 1948-56 period, vanadium was extracted I fault. Between May 1964 and July 1965, Hu­ I £ I I from ore that was shipped from these mines I ------r--r----+--+--4---I---' meca Exploration Company drilled five deep I holes (2500 feet ±), in the center of section to some of the processing mills on the Col~,.I I : 21, and in the southwest corner of section rado Plateau. However, most of the ore has -- -1------:------22, T29S, R24E. Interpretation of Century been processed at the Atlas Corporation at- r Geophysical Company gamma ray logs of kaline leach mill at Moab, Utah, and to date these holes indicated that two holes penetrated this mill has recovered only a small amount 776 Ore Deposits of the United States, 1933-1967 Part 6 Chap. 37 Part 6 Chap. 37 Geology and Exploitation of Uranium Deposits in Utah 777 TABLE I. ;f.n_1 Chinlr-Cutler Ore 'roduction 1948 surface ground conditions, and by the kind ,hrough F. Y. 1965 of mining equipment the company had avail· rado Plateau. Good access roads follow the beds are well-sorted, are fine- to medium­ able. The mining equipment in use depends valley floors. Except for a few drill roads, most grained, have a saccharoidal texture, and are Tons Pound. on the thickness of the ore and varies from of the hog-back ridges are inaccessible by as much as 50 feet thick. The sandstone is U.Os jacklegs to jumbos for drilling; slushers and motor vehicle. composed of quartz, feldspar, and biotite, with front-end-diesel-motor and air-motor loaders clay as the predominant binder, but locally 1948 to for mucking; battery or trolley motors with calcite may be the main cement. July 1, 1953 15,288 143,093 361,862 cars on track, Young-Shuttle Buggies, or GENERAL GEOLOGY A few uranium ore pods in Cutler sandstone F. Y. Ending Koehring's Dumpters for haulage. crop out along the west escarpment of Big July I, 1954 71,391 742,452 1,749,724 Many of the major mines are accessible Igneous Rocks Indian Valley about 100 feet stratigraphically July 1, 1955 208,781 1,998/764 3/271,362 by shafts 400 to 800 feet deep, but the Mi below the Permian-Triassic nonconformity and July 1/ 1956 394/713 2,795/701 2,643/571 Vida, Big Buck (Standard). Louise, and North No igneous rocks are exposed on the anti­ 1000 to 1500 feet up dip and northeast of July 1/ 1957 592,304 4,707/193 3/409/168 Alice are entered by inclines or adits. Direct cline, and none has been encountered in the the eastern limit of the ore belt. Other ore July I, 1958 773,042 6/377/746 2/401/720 mining costs, plus haulage to mill of about numerous oil and gas test wells that have pene· pods are found in these massive sandstone July I, 1959 771/229 6/349/628 3,821,721 4.5 cents per ton mile, ranged from about trated over 11,000 feet of sediments on the units where they subcrop under the Moss $6.40 per ton for ore 15 to 45 feet anticline. The nearest igneous intrusives are Back ore deposits. Some ore pods are as much Subtotal (2,898,748) (23,114,582) (17,659,128) thick, using the room and pillar method. to in the La Sal Mountains (South Mountain), as 40 feet below the nonconformity, but most July I, 1960 760,585 5,649,143 Incomplete about $13.10 per ton for ore 3 to 8 feet thick, 7 air miles north of the North Alice mine are within 6 feet of it. The Cutler sandstone July I, 1961 640,536 4,179,223 vanadium using the long-wall retreat method. The mines (Figure 1). Dl!ring the Tertiary period, the beds, where exposed in the mine workings, July 1,1962 590,319 3,819,600 assay were dry, the ore bodies were fairly uniform diorite, monzonite, and syenite porphyrys of appear to be more extensively bleached than July 1, 1963 418,477 4,309,452 record •• in thickness, the dip of the bedded host rock the La Sal laccoliths, dikes, sills, and plugs they are on the rim outcrops. The thickness July I, 1964 507,398 4,650,565 was usually less than 10°, fracturing was not were intruded into and through at least 9000 of this bleached zone below the unconformity July I, 1965 330,748 2,806,691 excessive, and the average grade was high for feet of sediments (Pennsylvanian through Cre­ does not appear to be directly related to the this type of bedded sandstone ore. taceous in age) (15). No physiographic, struc­ size or position of the overlying ore bodies TOTAL 6,146,811 48,529,256 tural, or mineralogic evidence appears to relate but does appear to be related to the thicker the La Sal igneous intrusives to the Lisbon and more porous of the Cutler sandstone beds. PHYSIOGRAPHY • Note. The above production was compiled from U.S. Valley uranium deposits; however, some geolo­ Atomic Energy Commission are receipts and include. ore Lisbon Valley is one of the many north­ gists postulate a relationship based on geo­ MOENKOPI FORMATION The Moenkopi For­ shipments to numerous uranium processing mills on the west-trending, subsequent stream valleys graphic considerations, on the Tertiary age of mation, widespread throughout the Paradox Colorado Plateau. From November 1956, when the Moab formed along breached salt anticlines in the the major faulting, and on a few U"" /Pb'" Basin, does not crop out on the anticline (12) mill went on stream, to 1960, the mill a.sayed the are for Paradox Basin of the Colorado Plateau (20) isotope age determinations that indicate early (27), but it is penetrated in oil and gas test vanadium, but after 1960 they dl.contlnued the practice. (23) (28) . The Cane Creek, Moab, Lisbon Tertiary ages. wells drilled low on the flanks of the anticline POlt·1959 vanadium allays are available on are shipments Valley, and Dolores (Slick Rock) anticlines (22). At the nearest outcrops on the Colorado to other plateau mills, but these shipments were sporadic are on the west edge of the deeper part of Stratigraphy River, the Moenkopi consists of interbedded the basin; they all have Triassic and younger dark-red to chocolate-brown, laminated, mica· of vanadium on an experimental basis. Mo· formations exposed; they all have uranium A generalized stratigraphic section at the ceo us, ripple-marked shales and siltstones, con­ lybdenum assays ranging up to 0.25 per cent mineralization in basal Chinle sandstone beds. anticline is shown in Figure 3, which sym­ taining a few thin, well-sorted, fine-grained are common but very spotty in the Big Indian The Lisbon VaHey anticline is a compound bolizes the lithOlogy and gives approximate sandstone beds. It is unconformably overlain ores. Those deposits with anomalous molybde· s!ructure formed by folding during both the thicknesses of formations. Only the ore-bearing by the Chinle Formation. num, such as the North Alice, South Almar, Permian and Tertiary periods. The two anti­ formations and those important in explaining CHINLE FORMATION The Chinle Formation Mi Vida, Standard, and Velvet, normally assay clines have separate but nearly paraJIel axes; the characteristics and the genesis of the Big consists of fluviatile and lacustrine sediments only 0.03 to 0.07 per cent molybdenum. however, the younger Tertiary anticline forms Indian ore belt are described in the text. and averages about 400 feet thick along the Up to July 1, 1965, about 6,147,000 tons the present physiographic structure. Weir, et ore belt. The lower part is the Moss Back of ore at a grade of 0.39 per cent U.O. con· al. (31) named the smaller, ancestral Permian CUTLER. FORMA nON The Cutler Formation Member (type section in White Canyon), taining about 48,530,000 pounds of U.O" anticline, the axis of which is west of the fault, at the Lisbon Valley anticline exemplifies the which ranges from 10 to 80 feet in thickness which is over 8 per cent of the U.S. total, the Lisbon VaHey anticline, and the larger Ter­ red bed facies (10, 11, 26) and ranges from and was deposited on the Cutler erosion sur­ had been mined from deposits in the Big In· tiary anticline, the axis of which is east of 900 to 1800 feet in thickness. It thins gradually face by streams flowing westerly and north­ dian ore belt, including production from the the fault, the Lisbon Canyon anticline. The to the north and to the west and thickens westerly. The upper part of the Chinle. which Cutler Formation, Table I. Continuation of writer prefers to consider the smaller Permian to the east and northeast toward the Uncom­ ranges from about 275 to 400 feet in thickness operations to 1971 should result in a total anticline the ancestral Permian anticline and pahgre uplift. Throughout the salt anticline area, in this area, has not been precisely correlated, production of about 57 million pounds of ura· the larger Tertiary anticline the Lisbon Valley at the top of the Culter, there is a notable ero­ but it is probably equivalent to the Church nium oxide worth about $450,000,000. anticline (Figures 1 and 2). sional unconformity. Erosional thinning of the Rock Member in White Canyon (11) (32). In the Big Indian belt, all underground min­ The Lisbon Valley anticline covers an area Cutler over the anticlines indicates the Per­ The Moss Back Member, the uranium host ing methods allow full caving, and rarely is about 21 miles long and 9 miles wide. Alti· mian ancestry of most of the anticlines (24). rock in the Big Indian belt, is predominantly a stoped area accessible after the ore body tudes range from about 6000 to 7200 feet. Where exposed in Big Indian Valley (Figure a fluviatile, cross-bedded, calcareous, fine· to has been depleted. The mining method selected Many high sandstone-capped cuestas, cut by 1), the fluviatile upper part of the Cutler con· coarse-grained, arkosic, poorly-sorted sand­ was often determined by the adequacy of de­ canyons or gorges 200 to 500 feet deep, char· sists of alternating beds or lenses of light pink, stone with interbedded lenses of mudstone and velopment drilling, by the knowledge of sub- acterize this area, which is typical of the Colo- orange, and buff mudstone, calcareous silt· calcarenite conglomerates. Sparse to abundant stone, and arkosic sandstone. The sandstone coalified plant material, mostly as woody trash, n8 Ore Deposits of the United States, 1933-1967 Part 6 Chap. 37 ParI 6 Chap. 37 Gealogy and Exploitation of Uranium Deposits in Utah n9

occurs in sandy lenses and pockets in and streams and caused shifting of stream courses. ERA SYS~M FORMATION above the basal part of the ore sandstone or This resulted in many facies changes and the and are depo~lts I~ous/" Dokolo gpo 4C>-IOO~n- Copper - mlnerollzotlon in highly coalified mudstone beds above the deposition of intraformational conglomerates -- --:. ore sandstone. The upper facies of the Moss and thick sandstone lenses favorable for ura­ 8:oUs~~Y ~~~ Back Member contains proportionably more nium emplacement. en 3: mem - - calcarenite conglomerate and micaceous mud­ Conspicuous bleaching, manifested by color stone beds. The Moss Back is gray-green to changes of the rock from darker to lighter % Uronium - vonadlum 1I0lt unit ~ ~1 dark brown to greenish-gray and light gray colors, has taken place in the upper Cutler g g Solt Wasil .:--_--=~ mem in contrast to the variegated red color of the . . and lower Chinle beds, predominantly along overlying upper Chinle beds. The Moss Back, the nonconformity. The bleaching is noticeable Jurassic in the northern and central part of the anti­ throughout the Big Indian ore belt, occurring v cline, averages 45 feet thick, and in the south­ in, above, and below ore and extending later­ ...o ern part only 13 feet thick. The Moss Back ally away from the ore deposits, although it o grades lithologically upward into the variegated is less conspicuous in areas remote from .,In reddish-brown, purple, and lavender thin­ known ore. The greater intensity of bleaching ~ bedded siltstones and claystones of the upper indicates that strong reducing conditions, Chinle. Many of the claystones are lacustrine, caused either by migrating humic acids derived and some of the clay beds are bentonitic, hav­ from diagenetic processes, by sulfur-bearing Jurassic? Koyenlo fm. ing been derived from volcanic ash (14) (38). waters rising from salt anticlines or oil fields, 200- 250 ft Isopach maps of the Chin!e Formation indi­ or by uranium mineralizing solutions, existed 1-:-::":-~ ' ~ ' 7 .- cate that this formation is over 100 feet thicker in and nea:- the ore. to the southwest and down dip from the cen­ In the vicinity of ore deposits, the contact Wi nQol8 Sl. tral group of ore bodies than it is over these between the Cutler and Chinle beds is often 260-360 II ore bodies, and, in contrast, it is about 100 difficult to identify, particularly where the Triossi c feet thinner to the west or down dip from basal Chinle sandstone contains an abundance Chinle f m. the northern group of ore bodies than it is of reworked Cutler arkosic sands or where 340·480 ft over them. This notable thickening and thin­ the beds on both sides of the contact are ning, 480 to 340 feet, is characteristic of fluvia­ bleached to light gray, are calcareous, are ura­ MO~~~~~ ~ ~:. :- ~~:»..:.- "~~~ Major uranium host unit Angulor Unconformlly _ . 7"-'-':"~"'-':'-:-':""\ tile sediments in this region. niferous, and are otherwise lithologically simi­ ...... Pes Spotty uranium mi"t'rohlotion lar. The following mineralogic, lithologic, and CUTLER-CHINLE NONCONFORMITY The angle color variances may be used to locate the con­ -.;. .-~~~~~~;"'~";'~~/ of discordance between the beds of the Cutler tact. The Moss Back has an abundance of and Chinle Formations at the northwest end carbon specks or woody fragments, an abun­ 0 Cutler fm =~=-~-:.~ =~=~ =:.:,1 of the ore belt is less than 2 ; at the Standard­ dance of red or gray subangular chert pebbles 900-1800 ft ...... -----"'-.:..; .. . . -.:... Big Buck mine near the central part of the and concretions, and some muscovite and chlo­ 0 ore belt, it is about 6 ; and at the southeast rite. It is poorly sorted and is more cross­ end of the belt it is 3 0 to 4 0 (Figure 4). The bedded and more coarse-grained than the Cut­ Permian paleotopography of the nonconformity varies ler. The Moss Back in the vicinity of ore is from a fairly smooth, undulating surface with light to dark-gray, greenish-gray, or buff with less than 5 feet of relief to a deeply scoured some limonite specks. The Cutler sandstone, surface with over 30 feet of relief. The pa­ on the other hand; has an abundance of fresh ...o o leotopographic relief is greater in the area un­ and altered fe!dspar and of biotite altered to ... derlying the ore bodies in the central part of chlorite and has a few thin gray and red chert "0 a. the ore trend where the greatest Permo-Triassic beds or lenses. It is normally friable and fairly uplift and erosion occurred. Elongated scours well sorted. Where overlain by ore, it is mot­ - ~ : .; ~ .. ' • • •• • . • • 0 .. • .- __ • - . - : •• . .' .\ or troughs are common, but no pattern or tled-gray, tan, brown, and pink. The mottled -=.l common orientation is evident. Distribution coloration grades downward into a normal of the are bodies is erratic with respect to the rusty-red or brown (12) (18). paleo lows and highs (Figure 5). Some large scours parallel the strike of the Cutler subcrops, Structure of the Anticline and Fault Zone and other scours trend down the dip of the H,rmosa fm. Cutler beds, but there are no persistent or well­ The Lisbon Valley anticline is a faulted Pennsyl­ 1100- 2000ft vanian defined channels, such as the Shinarump (basal asymmetric anticline, formed by flowage of Chinle sandstone) channels of the White Can­ salt and gypsum in the Paradox Member of yon district (R. C. Malan, this volume). From the Hermosa Formation (Figures I, 2, 3, 4). . ~.• : . ~ ' :-~ . . general observation in the mines, it appears Over 6000 feet of salt and anhydrite beds have that the variable topography of the surface of been penetrated in a few of the oil and gas FIG. 3. Generalized Stratigraphic Section in the Lisbon Valley Area. nonconformity produced turbulent Moss Back test wells. According to Budd (22, p. 121), ..... "'( c:o o o L _seON VAlle Y CD o It "0 rooc ~~ ' .'~ • . •_.. .~.W.'h ~. - ~ ,~." --~-- n~~= - ~~ : ·~~:~:(~':":t~.· :~~:=;~:~~ ~:~~~~~:: " '- ~~-::-:~..!:h=~ _--- --\- -" L ':,- ;... :::, --- - - :::.~ ='---- -= . == = ~~ -""".:-t 'oo ' ~ 2. :f~~::-~~=::~::~~--J>-~~~:- ~~ ··~ · '· · \-v·'!;::': · ~ ~~},~~~~:~~~::~1~? ' -' ;:. ... - CD ------Section olonll A - A' across central Lisbon Valley anticline. C it=. CL (I) s.. flgu,. L fo, ..plano lion and localion III 0 Q I I of .. etlons A-A' and B- B' WILES ~

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7000'] . Jo ~~ ( --. ::::~ _ _ ~u b..:: _001 '" __ ... ~~ .".. ... ---- '"" ::-.::---:=:::~--: =--=-.::-:----~--==- =-""-=-;-;-;-;-.==.:=~.:-;-..:::-- .--

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SOlie dolo loll.n hom Min tfal Inw'1119Qtioftl .... Section olonll B- B' across Lisbon Valley anticline at Ike - Nixon shall, f itld Slucliu Mop I MF - 145 and Mf -1$1 ~ ()o 9 FIG. 4. Geologic Sections across the Lisbon Valley Anticline. ":'" I ~

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_0-- C) It --- -0-'" EXPLANATION 0 TI"'\" 1tc "ionic C"inlt I,.. 0' - I" cO I--D.'lil "cliCMII D·O' "' ••• hIO ... ---i Longitudinal S.ction CoCo Pc: P.U'UOft CIoIU •• 'M S. Son4latOllf -< -1" Q OH Ot- ill tlo" pfOl ec1e4 10 :l T Ii". 0' U,IIOf! CL e ll Con'lo .... ' ... m )< ~ Wi i".lIou"'•• "0 s •• lillU'. I 10' 10COlioft 01 ... lIoft C- C' §: [ c)" o :l ..441 2. ca .uo' c::I · 3 0 CD O.toil of or. londslone in loIi Vida Min. olona Section C-C' "0 ~. 5· c FIG. S. Geologic Section across the Ore Body at the Utex (Mi Vida) and Standard (Big Buck) Mines. Q :r ...... c:o 782 Ore Deposits of the United Stotes, 1933-1967 Part 6 Chap. 37' Part 6 Chap. 37 Geology and Exploitation of Uranium Deposits in Utah 783 the anticline has 3000 feet of vertical closure flank of the Tertiary anticline, is shown on at the surface. Figures 1, 2, 4. the Laramide orogeny. Salt and gypsum flowed ness, with an average thickness of 6 feet. The The anticline is faulted along its longitudinal into the footwall of the fault, thrusting the ore has an average grade of 0.39 per cent axis by the Lisbon Valley normal fault. The Geologic History of the Anticline footwall block upward and southwestward. U.O., contains about 15 per cent CaCO., and fault plane has dips ranging from 50· to Tilting of the southwest flank accentuated the has a dry bulk density factor of about 13 cubic 85°NE. The surface trace of the fault is about In Pennsylvanian time, a deep basin devel­ arcuate bend of the ore belt. In the hanging feet per ton. The northern 6 miles of the big 21 miles long but probably has a greater length oped southwest of the northwest-trending Un­ wall, away from the fault zone, the beds were Indian ore belt contains about 2600 acres, of at depth. The fault zone contains gouge, shear compahgre Highland. A thick sequence of elevated only slightly. Rejuvenated flowage of which about 300 acres is underlain by ore. bands, and closely spaced step faults with a marine shale. limestone, and evaporites accu­ evaporites and accompanying movement along All the deposits are irregular, amoeba-shaped variety of dips, some reversed. Adjacent beds mulated in this basin; the Lisbon Valley area the fault probably continued into Oligocene masses that lie concordantly to the bedding. are often broken by drag and gash fracturing. is on the southwestern edge of the deeper part or Miocene time and still may be active. The Within each deposit, there is a notable variabil­ At the crest of the anticline, the displacement of this basin. Plastic flow of the evaporites unoxidized and unaltered condition of the ity in thickness and grade, but in general, the is about 4000 feet, and Hermosa beds butt into northwest-trending zones of weakness, brecciated fault zones along some of the small grade of uranium ore drops sharply at the against Dakota beds; 8 miles northwest at the folds or grabens, caused by fracturing and subsidiary faults, which displace uranium ore edges of the ore bodies. This sharp cutoff pre­ North Alice mine, the displacement is about faulting, initiated the formation of the salt bodies at the north end of the belt, indicates cludes the probable existence of any large re­ 2000 feet, and Chinle beds butt against Morri­ anticlines of the region (24,35). that some of this faulting may be fairly recent. serves of low-grade uranium ore. son beds. Displacement decreases toward the Uplift of the ancestral anticline started in Extensive erosion of the Lisbon Valley anti­ Late Permian time and probably continued northwestern and southeastern ends of the anti­ cline started in Late Eocene time (35), re­ Mineralogy and Geochemistry into Late Triassic time. During this period, moved approximately 5000 feet of sediments, cline, where the fault splits into a number. of of the Big Indian Ore smaller hinge-type branches. These branchmg a local topographically high area developed and exposed Pennsylvanian sediments on the faults have different dips and strikes, which that was exposed to extensive erosion. Hun­ crest of the anticline. Uraninite, UO.· UO" is the principal uranium complicate interpretation of the structural geol­ dreds of feet of Cutler and Moenkopi sedi­ ore mineral. Intimately associated are small ogy. Horst and graben blocks are common ments were denuded from the crest of the an­ amounts of coffinite, U(SiO.),-.(OH).-I, and along the fault but are most prevalent at each cestral arch, prior to deposition of fluviatile ECONOMIC GEOLOGY the vanadium minerals montroseite, VO(OH), end of the anticline. sediments over the structure by westward and doloresite, V.O.· nH.O, and vanadium clay or Almost aU branch faults and major fractures northwestward flowing Moss Back streams. Size, Shape, Grade, and Distribution vanadium hydromica. Secondary uranium and are parallel or subparaIlel to the Lisbon Valley Mild uplift probably continued during deposi­ of the Uranium Deposits vanadium minerals, such as metatyuyamunite, fault and the long axis of the anticline. At tion of the Moss Back sediments, as is evi­ Ca(UO.).(VO.k5-7H.O, pascoite, Ca.V,.O .. · the Cord, Far West, and North Alice mines, denced by the occurrence of intraformational The I5-mile-long by half-mile wide Big In­ I6H.0, and corvusite, V.0.·6V.0.·nH.0 are subsidiary normal faults dip to the northeast conglomerates that contain mudstone, cal­ dian ore belt consists of numerous intermittent found in areas of oxidation, but they are of no and southwest and displace the ore bodies carenite, and chert pebbles or fragments de­ bodies ranging in size from 500 to 1,500,000 quantitative importance (8). Beautiful high­ ( 18) . Small strike slip displacements are measur­ rived from erosion of Permian and Triassic tons of ore. A five-mile stretch of the south­ grade uraninite ore specimens, usually replace­ able where the faults are exposed underground sediments. central part of the ore belt has been removed ments of coalified wood, have been collected (Figure 2). The intensity of fracturing or the Emplacement of uranium minerals to form by erosion, leaving about 6 miles of coalesced from many of the mines; some samples assay strike of the fractures does not appear to con­ the Big Indian ore belt started soon after de­ or separate ore deposits in the northern part about 80 per cent U,O.. Ore minerals domi­ trol the location or shape of any observed ore position of Chinle sediments and probably con­ of the belt and about 4 miles of scattered nantly fill the interstices between grains of body. However, the longitudinal fractures, tinued until movement of connate waters, smaller deposits in the southern quarter. Possi­ sand, but they also replace calcite, carbon­ which are usually open, have caused mining caused by compaction of sediments or by re­ ble evidence that ore bodies have been eroded, aceous plant remains, and, to a lesser extent, problems and unexpected caving. gional folding, became negligible. During the between the Standard and Serviceberry mines, detrital quartz and feldspar grains and other On the southwest flank, the Chinle beds dip ensuing Triassic, Jurassic, and Cretaceous pe­ is indicated by the anomalous radioactivity in accessory minerals. 10· to 15°SW, and the Cutler beds dip as riods, the Paradox Basin continued to subside the alluvium of Big Indian Valley in the vicin­ The principal detrital constituents of the much as 20·. On the northeast flank, the Juras­ and thousands of feet of eolian sandstone, flu­ ity of Big Indian Rock (7), and by the exis­ quartzose sandstone host rock are quartz, limy sic and Cretaceous beds dip 5· or less to the viatile sandstone and mudstone, marginal ma­ tence of uranium mineralization on a point rock fragments (calcarenites), feldspar, mica, northeast. All bedding dips decrease toward rine, marine, lake sediments, and volcanic ash of Moss Back cropping out in section 30, chert, clay, and coalified plant remains. Min­ the ends of the anticline (Figures I, 4). beds were deposited over the region. This de­ T30S, R25E. erals commonly associated in anomalous quan­ The difference in the shape of the Permian positional sequence was interrupted by brief The ore belt contains two large groups of tities with the ore deposits are barite, celestite, anticline from the shape of the Tertiary anti­ hiatuses, which probably coincided with some nearly coalesced' deposits from which 74 per galena, pyrite, chalcopyrite, chalcocite, molyb­ cline is indicated by: (1) the approximate 15° regional uplifting. Proof of continuous or in­ cent of the districts ore has come as of July denite, chalcedony, greenockite, and sericite angle between the strike of the Cutler beds termittent salt flowage during this period is 1, 1965. Approximately 20,000,000 pounds of (8) (31). and the strike of the Chinle beds in the north­ not available, but it is inferred, from the varia­ U.O. has been mined ' from the north group Paragenetic studies (8) indicate that detrital ern part of the ore belt; (2) by the flattening tions in formation thicknesses and from the of deposits and 16,000,000 pounds from the minerals were deposited and cemented by cal­ of the dip in the Cutler beds on the crest hiatuses in the overlying sediments, that mild central group. Three intermediate-size ore de­ cite; silica and barium sulfate solutions precipi­ of the ancestral Permian anticline; and (3 ) salt flowage could have occurred intermittently posits lie between the two larger groups and tated authigenic silcia and barite; local de­ by the difference in the discordant angle of (19,24,27). production from them ranges from 2,800,000 formation of the mudstones and some of the dip between the Chinle and Cutler beds Major uplift of the present Lisbon Valley to 3,500,000 pounds of U.O•. Eight smaller less competent sandstone beds resulted in frac­ throughout the anticline. The present location anticline, which was superinduced on the an­ ore bodies, ranging in size from 500 to 90,000 turing of quartz, feldspar, and calcite; and ore of the ancestral Permian anticline, now a cestral Permian anticline, and the major offset tons or ore, are scattered throughout the ore solutions penetrated the sandstone, replaced minor anticline or flexure on the southwest along the Lisbon Valley fault occurred during belt (Figure 2). In general, the ore deposits some minerals and plant remains, and precipi­ range from a few inches to 45 feet in thick- tated in the voids. In places, there was also 785 784 Ore Deposits of the United States, 1933-1967 Part 6 Chap_ 37 Part 6 Chap. 37 Geology and Exploitation of Uranium Deposits in Utah fracturing of the detrital grains after uraninite (Figure 1) by the author were submitted to sandstone units. Although thinner and litho­ was influential in positioning the ore belt. They was formed, but before introduction of some John Rosholt (U.S.G.S.) for isotope analysis. logically less favorable Moss Back sandston.e theorized that it acted as an impervious cap to rising uraniferous solutions, until the pinch­ of the galena and greenockite. Calcite was The results of isotope fractionation studies on is spread over the southern part of the ~n~l­ probably deposited, dissolved, and redeposited U ... , U ... , and U''', as given in J. N. Rosholt's cline, even this less favorable host rock, wlthlO out was reached or that the uraniferous solu­ many times; consequently, calcite is replaced letter on May 13, 1964, for these samples, are the ore belt, contains numerous small but tions, migrating laterally in the fairly per­ by uraninite and other minerals and in turn summarized in this quotation: "The Lisbon minable ore deposits. Persistent paleostream meable Moss Back beds, were confined be­ replaces them (13, p. 548). Valley samples studied show extremely good channels which were scoured into the Cutler tween the quite impermeable Moenkopi and Geochemical and mineralogic studies (17, examples of radioactive equilibrium between paleotop~graphy and later filled with thick upper Chinle beds. The val~dity of this hy­ 20 pothesis depends on the locatIon of the Moen­ 31) show that: (1) lead correlates with ura­ U • and U.. • . No other area in sandstone-type lenses of favorable Moss Back sandstone, do kopi pinch-out, which has not been deter­ nium, (2) molybdenum occurs as a halo above ore deposits. yet analyzed, has indicated such ~ot occur under the Big Indian ore belt. Elon­ some of the central and southern ore bodies, an environment of consistently stable uranium gated sandstone-filled scours, containing ura­ mined. (3) vanadium ranges from one-third to three mineralization. The deviation from the equili­ nium ore do occur at some of the larger ore times the per cent of uranium in the Mi Vida brium U'''/ U'JJ ratio is within ± 1 per cent for deposits, but their control of any ore distribu­ Structural Position of the Ore Bodies mine and in other deposits to the south, and all six samples, thus within our experimental tion is local. A structure map, (Figure 2), showing con­ ( 4) is negligible in the Ike-Nixon mine and error. There is no evidence to indicate that Prevalently the lowest sandstone or co~­ tours drawn on the nonconformity at the base in other deposits to the north. Most of the the uranium mineralization in the fault zone glomerate unit of the Moss Back Memb~r .. S of the Chinle Formation, shows that the the uranium host rock, and it rests on or wlthm ore from the Mi Vida mine on the south may (at the mines mentioned above) occurred at 6-mile-Iong northern half of the ore belt lies a few feet of the Cutler-Chinle nonconformity. be classified as uranium-vanadium or vana­ a more recent time than that some distance between the 6000- and 6700-foot contours and Within a host unit, the lithology and the sedi­ diferous uranium ore because the ore will usu­ from the fault zone." the southern one-quarter of the ore belt is ally assay over 0.40 per cent V,O•. Other ex­ Uranium-lead isotope age determinations mentary structural features, which direc~ed ~e between the 5800- and 6800-foot contoun. course of the ore fluids, control the locahzatlon trinsic elements, anomalous in or around the range from 85 to 295 m.y. and disagreements Furthermore, over 90 per cent of the ore oc­ ore bodies, are arsenic, barium, cadmium, cop­ on interpretation and value of the age deter­ of the ore. The ore bodies may cut across curs between the 6200- and 6700-foot contours per, iron, strontium, and zirconium and some­ minations are acknowledged by many (16, bedding planes within the host and may o~ur in the northern half of the ore belt. Explora­ times selenium, cobalt, zinc, yttrium, and 34,36) . Most of the U W /Pb2IIT apparent age above and below a mudstone seam, but they do tion drilling to date has failed to discover lar~ columbium. determinations range between 150 and 210 not cross through intercalated mudstone beds. ore bodies on the southwest flank of the anti­ Lekas and Dahl (12) in 1956 and Puffett Mill heads average about 15 per cent CaCO., m.y. and imply that the ore deposits are cline outside of this delineated belt. This verti­ and Weir (21) in 1959 recognized the spatial but the CaCO. content differs considerably Jurassic to Triassic in age. cal limitation was first referred to in 1955 as relation of the Moss Back ore deposits to the from deposit to deposit within the ore belt the "magic contour interval" (6). . and also from place to place in the individual Favorable lithology of the Host Rock subcrop, at the nonconformity, "of a Cutle~ The horizontal width of the ore bodies or ore bodies. The calcium carbonate concentra­ sandstone unit, called locally the sugar san? ore body aggregates along the trend ~f the tion is highest where it occurs as a cement Where this unit crops out at the Standard mme Lithologically the most favorable host rock ore belt ranges from 800 to 3000 feet 10 the and as detrital grains. Rarely does high-grade is a gray, poorly-sorted, fine- to coarse-grained, portal, it is a 30-foot-thick, friable, porous, northern section. At the northwest and south­ saccharoidal, fine-grained, light-gray sandstone. ore assay over 20 per cent CaCO•. Commonly calcareous, arkosic quartzose sandstone con­ east ends, where the ore belt is inte~ected the CaCO. has been recrystallized to form visi­ taining some interbedded mudstone and lime­ Underground it can be traced from the by the Lisbon Valley fault, the ore bodIes are ble sand crystals showing a poikilitic texture stone pebble conglomerates and some mud­ portal, in a northwesterly direction, to the spread over a wider area, 3000 feet to over (8). Although these deposits are hundreds of stone and siltstone lenses, all poorly sorted north end of the Mi Vida mine. This "sugar 3600 feet across the trend, giving the appear­ feet above the present water table, the low and of variable permeability. The highest-grade sand" has not been definitely traced north of ance that the ore is spread out along the Lis­ permeability, due to cementation by calcite, ore is in semi-permeable, fine-grained, sandy the Mi Vida mine. It is believed that the north­ bon Valley fault. This spread of the ore belt has protected them from oxidation and leach­ lenses that contain less than 30 per cent cal­ ern ore bodies are underlain by different, strati­ may be explained by a flattening of the angle ing by vadose waters. cium carbonate as cement or as clastic lime­ graphically lower, but physically similar Cutler of nonconformity between the Cutler and Coalified wood fragments are common, but stone grains. Jasper, smoky quartz, pyrite, and sandstone units. The common occurrence of Chinle beds from 6° at the crest to . 3° at the this sandstone unit or its physical equivalent show little spatial relation or quantitative cor­ a reddish-brown or pink calcite, colored by ends, and by a gentle flattening . o~ the dip relation to the ore deposits. Coaly material hematitic inclusions, are common in the under the ore belt has been a useful guide of these beds at each end of the antlcllOe. is usually in the clayey beds immediately above higher-grade deposits. There is an abundance in exploration. Lekas al'd Dahl suggest that The limitation of the ore belt within the the ore-bearing sandstone. where it is concen­ of mudstone pebbles and coalified wood-trash the subcrop of this porous Cutler ~andstone "magic contour interval" may imply a water trated along bedding planes and is disseminated either in or directly overlying the host rock. unit acted as a conduit for ore solutIOns, thus table or a water-oil-gas interface as a cont~ol in mudstone conglomerates. Because the coaly localizing the ore deposits within the delineated for positioning the Big Indian uranium depOSIts belt lU1d Noble (37) suggests that'a pressure layer is usually barren and is embedded in Stratigraphic Position of the Ore Bodies (30). Another interpretation is that the struc­ mudstone, it is not ' broken into during mining, cha~ge occurred at the intersection of the two tural position of the ore belt may repre~nt which may account for the low carbon content The Chinle Formation thickens and thins (Cutler and Chinle) acquifers. It is suggested an ancestral water table where the descendmg of the mill heads. Within the ore bed, some notably, 480 to 340 feet in short distances. by the writer that the Cutler porous sandstone vadose water encountered connate water. coalified logs are partially replaced by urani­ There is no apparent relation of the thickness units may have acted as a conduit for rising nite, but others are not. of the Chinle Formation or of the Moss Back gases or solutions that precipitated the ura­ Member to the position of the ore belt. nium minerals or changed the pH or Eb suffi- Summary of Geologic Characteristics of the Big Indian Ore Belt Isotope Analyses and Geochronology Usually, within the ore belt, the larger ore ciently to permit precipitation. . It has been suggested by some geologISts of the Big Indian Ore deposits are where the Moss Back Member ( 1) Most of the ore in the 15-~ile-.loI?g is thicker, such as across the north-central part ( 6, 12) that the position of th~ erosional by half-mile wide Big Indian ore belt 15 wIthin Uraninite ore samples collected from the of the anticline, but the higher-grade depOsits pinch-out of the Moenkopi Formation, a~o,!nd a 500-foot elevation interval. North Alice and South Almar (Cord) mines in the northern ore bodies are in thin basal the southwest flank of Lisbon Valley antlchne, Port 6 Chop. 37 Geology and Exploitation of Uranium Deposits in Utah 787 786 Ore Deposits of the United States, 1933-1967 Port 6 Chop. 37 probably comingled with vadose ground Ore Guides and Potential of the Area (2) The large ore bodies are hundreds of (13) No anomalous radioactivity has been waters. Under hydrostatic forces or water of feet above the present water table, but more found along the trace of the Lisbon Valley compaction forces (30,37), the solutions Future exploration along the Big Indian ore than 95 per cent of the ore is unoxidized fault or along the fault zone at depth, except moved laterally through the permeable Moss belt may be guided by the stratigraphic and uraninite. where the Moss Back, containing uranium Back sandstone toward points of expulsion or structural ideas and favorable host rock char­ (3) The spread of the ore bodies across mineralization, butts against the fault, and ore precipitation. At times, movement may have acteristics described herein and by giving due the belt is appreciably wider at the northwest bodies do not appear to have been localized been rejuvenated by ground water flushing the consideration to the probable shape and size and southeast ends of the anticline, where the or shaped by fractures. aquifer. of the target. Favorable Moss Back beds are beds have a more gentle dip and the Cutler­ It is reasonable to assume that the ura­ spread over the northern part of the Permian Chinle angle of nonconformity is less than it Ore Genesis and Mode of Deposition niferous solutions contained some natural anticline, with the thickest sandstone beds on is along the central part of the southwest flank. gases, such as methane and dense carbon di­ the crest of the anticline. Less favorable sand­ (4) The bedded ore deposits are displaced, Except for slight variations in their theory, oxide; that they were mixed with ground stone beds cover the southern part of the by Tertiary normal faulting, at the North Alice, Steen (2), Isachsen (6), Loring (18), Weir waters; that the uranium was transported as anticline. Far West, Cord, and Continental (Section 36) and Putfett (29), and Jacobs and Kerr (39), a nearly neutral, highly stable, uranyl dicar­ The more irregular the relief of the Cutler mines. postulate a hydrothermal origin, advocating bonate or tricarbonate complex; and that pre­ paleotopography, the better are the chances (5) The main ore deposits are usually con­ access of rising uranium, vanadium, and cop­ cipitation resulted from reduction of hexa­ of finding lithologically favorable Moss Back fined to the lowest sandstone bed in the Moss per solutions by way of the Lisbon Valley fault valent uranium to form uraninite (33). As sandstones. The scours trending parallel to the Back Member of the Chinle Formation. or by way of some unnamed conduit. Lekas explained by Garrels (5), the part played by strike of Cutler beds are deeper and commonly (6) Uranium deposits appear to be more and Dahl (12) discuss a variety of hypotheses liquid or gaseous CO. in the dissolution and contain uranium deposits on the up dip side persistent or to occur more often where po­ of origin and localizing features. Kennedy transportation of uranium is not fully under­ of the scour. rous, friable, fine-grained Cutler sandstone (25,31), and Noble (37), each postulate, stood, but, because large quantities of CO. are The favorable characteristics of the Moss units, bleached to light gray, sub crop at the but in a slightly different manner, that connate associated with the Mississippian oil reservoir Back on the northeast side of the Lisbon Val­ nonconformity under lithologically favorable waters, which were expelled from fluviatile under the northwest flank of the Lisbon Valley ley fault have not been thoroughly evaluated. Moss Back sandstone. sediments during compaction, may have been anticline, this probable relationship should be A Moss Back thickness of about 33 feet has (7) Small deposits of uraninite ore are in the ore-forming and ore-transporting fluid. considered and studied. Upon reaching a fa­ been interpreted from a gamma log of a deep the Cutler sandstone adjacent to the Moss Waters and Granger (3) and Schultz (14, vorable depositional site, precipitation may hole drilled northeast of the fault. GeologiC Back ore deposits. Carnotite deposits also 38), discuss how the extrinsic elements may have been caused by change in the pH and Eh, logs of other deep test wells drilled n?~east occur about 500 feet laterally up-dip and have been derived from Chinle volcanic ash or by reduction in pressure, or by encount~r­ of the fault, and still on the structure, lOdlcate at approximately the same elevation, but lower or tuff beds. ing hydrogen sulfide produce~ by bactenal a variable thickness of Moss Back sandstone stratigraphically, in the Cutler section than the The possibility that uranium and other ex­ action on carbonaceous matenal (34). The and probably the occurrence of Moenkopi ore occurrence subjacent to the Moss Back ore. trinsic elements in the deposits could have been presence of an abundance of coalified plant sandstone under the Moss Back. Unless more (8) Persistent bleaching, resulting from precipitated by reduction from telethermal, material within the host rock and the probable rapid changes exist in the character o~ the the leaching of ferric oxide, is unmistakable connate, or meteoric waters leaves the genesis leakage into the Cutler-Chinle nonconformity Chinle streams than has been observed, It ap­ in the Chinle and Cutler Formations in and open to many hypotheses. The hypothesis that of natural gas or sulfur-solutions from the pears logical to assume that favorable ~oss around uranium ore and particularly along the the ore solutions rose through the thick series Mississippian oil and gas reservoirs beneath Back sandstone beds do exist across the Lisbon nonconformity. of Pennsylvanian gypsum, halite, shale and the ore belt, aSsures the existence of sufficient Valley fault. . . (9) Abundant coalified plant material oc­ limestone beds, and then used the Cutler po­ reducing agents (16). In summary, it is believed that the ongI~al curs as lenses or as aggregations in and above rous sandstone beds as conduits to known The mechanism suggested, if effective, im­ ore belt encircled the crest of the Penman the basal ore sandstone or as carbon trash points of deposition, seems improbable. Also, plies that these deposits were emplaced during anticline as a band. The southwest flank of disseminated in carbonaceous mudstone beds the absence of supporting evidence of hydro­ the fairly static period following deposition the anticline has been thoroughly explored for above the ore sandstone. thermal activity and the absence of any ore of the fluviatile Chinle Formation; that em­ large deposits. An extension of the Big Indian (10) Zoning of vanadium within the ore deposits localized along fractures or faults that placement continued during burial under thou­ ore belt, similar in size and grade to the known belt is manifested by the notable increase of could have acted as conduits for ascending sands of feet of Triassic and Jurassic sedi­ ore belt, probably occurs in the downthrown the V : U ratio in the Mi Vida and other thermal solutions makes it improbable that ments; but that emplacement ended prior to block northeast of the Lisbon Valley fault at ore bodies to the south and by some differ­ these deposits are of hydrothermal-hypogene the start of the Laramide orogeny. The depths of 2400 to 2700 feet beneath the ences, although erratic, in the up dip and down origin. ore deposits were positioned within the ore Dakota-capped surface. As of the fall of 1965, dip vanadium to uranium ratio within the ore In general, the geologic features of these belt by either a water-gas interface (30) or only nine holes had been drilled into the Moss bodies. deposits appear to be congruous with the the­ by a connate-vadose water interface near the Back sandstone northeast of the fault, which ( 11) Anomalous copper is spotty in Moss ories postulated by Kennedy, Noble, and the crest of the ancestral Permian anticline, or leaves this area as the most favorable unex­ Back uranium deposits and in nearby barren writer, and with some of the theories suggested by subcrops of either the porous upper Cutler plored area remaining on the Lisbon Valley Moss Back sandstone. In contrast, copper ore by Lekas and Dahl. ' sandstones or the Moenkopi Formation at anticline. containing only traces of uranium, is common The writer believes that the uranium was the nonconformity around the flanks of the in the Dakota Group sandstones at many indigenous to the Chinle Formation; was ancestral anticline. The multiple oxidation­ REFERENCES CITED places along the Lisbon Valley fault. mobilized or released from the siliceous glass solution-migration-accretion theory of Gruner (12) Molybdenum occurs as an anomalous by diagenetic processes, which started soon (9), does not explain some of t~e geolo~ic 1. Dix, G. P., Jr., 1953, The uranium deposits halo around some of the southern ore bodies after deposition of sediments; was moved later­ conditions described above, but It explalOs of Big Indian Wash, San Juan County, and is anomalous in samples collected from ally or outward from the least permeable sedi­ enough of these conditions to make this theory Utah: U.S. Atomic Energy Comm. RME- ore deposits adjacent to the subsidiary faults ments into more permeable sandstones, as con­ worthy of consideration. 4022, 15 p. in the northern part of the ore belt. solidation and compaction continued; and was 788 Ore Deposits of the United States, 1933-1967 Part 6 Chap. 37 Part 6 Chap. 37 Geology and Exploitation of Uranium Deposits in Utah 789 . 2. Steen, C. A., et al., 1953, Uranium mining tions of radioactive deposits: U.S. Geo!. operations of the Utex Exploration Co. in Surv. TEI·690, p. 497-504. U.S. Geol. Surv., Mineral Investigations, with special reference to sandstone· type ura­ the Big Indian district, San Juan County, IS. Hunt, C. B. and Waters, A. C., 1958, Struc­ Field Studies Map MF-143, 1: nium deposits: Econ. Geo!., v. 57, p. Utah: U.S. Bur. Mines 1. C. 7669, 13 p. tural and igneous geology of the La Sal 29. Weir, G. W. and Puffett, W. P., 1960, Simi­ 137-167. 3. Waters, A. C. and Granger, H. C., 1953, Vol­ Mountains, Utah: U.S. Geo!. Surv. 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B. and Garrels, R. M., 1962, thermal alteration along the Lisbon Valley Engrs., 13 p. gional geophysical investigations of the Lis­ The transportation and precipitation of ura­ fault zone, San Juan County, Utah: Geo!. 7. Research, Inc.-Dallas, Texas (Tripp, R. M.), bon Valley area, Utah and Colorado: U.S. nium and vanadium at low temperatures, Soc. Amer. Bull., v. 76, p. 423-440. May 1955, Research and development of Geo!. Surv. Prof. Paper 316·C, p. 39-50. geophysical and geochemical techniques for 21. Puffett, W. P. and Weir, G. W., 1959, uranium exploration on the Colorado Pla­ Geologic mapping, Lisbon Valley, Utah­ teau: U.S. Atomic Energy Comm., Final Colorado: U.S. Geo!. Surv. TEI-752, p. Contract Rept. RME·3111, 94 p. 13-18. 8. Gross, E. B., 1956, Mineralogy and paragene· 22. Budd, H., 1960, Notes on the PUre Oil Com­ sis of the uranium ore, Mi Vida mine, San pany discovery at northwest Lisbon: in Juan County, Utah: Econ. Geo!., v. 51, Guidebook-Geology of the Paradox Basin p. 632-648. fold and fault belt, Four Corners Geo!. 9. Gruner, J. W., 1956, Concentration of ura­ Soc. 3rd Field Conf., p. 121-124. nium in sediments by multiple migration­ 23. Buss, W. R., 1960, Physiography and geo­ accretion: Econ. Geo!., V. 51 , p. 495-520. morphic history of part of southeastern 10. Herman, G. and Sharps, S. L. 1956. Pennsyl­ Utah and adjacent Colorado: in Guide­ vanian and Permian stratigraphy of the book-Geology of the Paradox Basin fold Paradox salt embayment: in Geology and and fault belt, Four Corners Geol. Soc. economic deposits of east central Utah, 3rd Field Conf., p. 31-32. Intermountain Assoc. Petro!. Geols. 7th 24. Elston, D. P. and Landis, E. R., 1960, Cutler Ann. Field Conf. Guidebook, p. 77-84. unconformities and the early growth of the Paradox Valley and Gypsum Valley salt 11. Johnson, H. R., Jr. and Thordarson. W., 1956, anticlines: U.S. Geo. Surv. Prof. Paper Regional synthesis studies, Utah and Ari­ 400, p. 8261. zona: in Geologic investigations of radio­ 25. Kennedy, V. C., 1960, Origin of uranium­ U.S. Geo!. Surv. TEI-640, active deposits: vanadium deposits in the Lisbon Valley p. 188-191. area. San Juan County, Utah (abs): GeoL 12. Lekas, M. A. and Dahl, H. M., 1956, The Soc. Amer. Bull., v. 71, p. 1904. geology and uranium deposits of the Lisbon 26. Kunkel, R. P., 1960, Permian stratigraphy Valley anticline, San Juan County, Utah: in the salt anticline region of western Colo· in Geology and economic deposits of east rado and eastern Utah: in Guidebook­ central Utah, Intermountain Assoc. Petrol. Geology of tire Paradox Basin fold and Geols. 7th Ann. Field Conf. Guidebook, p. fault belt, Four Corners Geo!. Soc., 3rd 161-168. ,Field Conf. p. 91-97. 13. Holland, H. D., et 01. , 1957, The use of leach­ 27. Stewart, J. H. and Wilson, R. 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