GEOLOGICAL SURVEY CIRCULAR 336
GEOLOGY OF THE SHINARUMP NO. 1 URANIUM MINE, SEVEN MILE CANYON AREA, GRAND COUNTY, UTAH
This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission. UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary
GEOLOGICAL SURVEY W. E. Wrather, Director
GEOLOGICAL SURVEY CIRCULAR 336
GEOLOGY OF THE SHINARUMP NO. 1 URANIUM MINE, SEVEN MILE CANYON AREA, GRAND COUNTY, UTAH
By W. L Pinch
This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission.
______Washington, D. C., 1954 Free on application to the Geological Survey, Washington 25, D. C. , B E A V E R *
'IRON .-'I GAR
WASHINGTON
L K«n«b'p U A.R I
EXPLANATION Uranium deposit or group of deposits in the Shinarump conglomerate
Uranium deposit or group of deposits in the Chfnle formation
25 0 I i i i i I
Figure 1. Map of part of the Colorado Plateau showing the location of the Shinarump No. 1 mine and the distribu tion of uranium deposits in the Shinarump and Chinle formations. GEOLOGY OF THE SHINARUMP NO. 1 URANIUM MINE, SEVEN MILE CANYON AREA, GRAND COUNTY, UTAH
By W. I. Finch
CONTENTS
Page Page Abstract...... 1 History and production...... 4 Introduction...... 2 Ore deposits...... 4 General geology...... 2 Mineralogy...... 5 Stratigraphy...... 2 Petrology...... 6 Stratigraphic section...... 2 Habits of ore bodies ...... 9 Cutler formation...... 3 Spectrographic study...... 10 Moenkopi formation...... 3 Age determinations of uraninite...... 12 Shinarump conglomerate Origin of deposit...... 12 and Chinle formation...... 3 Conclusions...... 13 Wingate sandstone...... 4 Literature cited...... 13 Jurassic rocks...... 4 Unpublished reports ...... 14 Structure...... 4 Group number classification...... 14
ILLUSTRATIONS
[Plates are in pocket] Page Plate 1. Geologic maps and sections of the Seven Mile Canyon and Shinarump No. 1 mine areas, Grand County, Utah. 2. Selected maps of mine walls from the Shinarump No. 1 mine. Figure 1. Map of part of the Colorado Plateau showing the location of the Shinarump No. 1 mine and the distribution of uranium deposits in the Shinarump and Chinle formations...... ii 2. Paragenesis of uraninite and sulfide minerals, Shinarump No. 1 mine...... 6 3. Photomicrographs of polished and thin sections from the Shinarump No. 1 mine ...... 7 4. Cumulative curves of grain size of samples from the Seven Mile Canyon area...... 9 5. Frequency curves of grain size of samples from the Seven Mile Canyon area ...... 9 6. Curves of grain size of ore-bearing and barren siltstone from Shinarump No. 1 mine...... 10 7. Geologic map and sections of the Shinarump No. 1 mine...... 11
TABLES Page Table 1. Samples from Seven Mile Canyon area...... 8 2. Geometric mean values (in percent) of elements contained in barren and uranium-bearing rock from the Shinarump No. 1 mine, copper-bearing rock from nearby copper deposits, and uranium-bearing rock from a nearby deposit in the Morrison formation...... 12
ABSTRACT are found in three zones in the lower 25 feet of the Chinle formation of Late Triassic age. The Shinarump No. 1 The geology of the Shinarump No. 1 uranium mine, mine, which is in the lowermost zone, is located on the located about 12 miles northwest of Moab, Utah, in the west flank of the Moab anticline near the Moab fault. Seven Mile Canyon area, Grand County, Utah, was studied to determine the habits, ore controls, and The Shinarump No. 1 uranium deposit consists of possible origin of the deposit. discontinuous lenticular layers of mineralized rock, ir regular in outline, that, in general, follow the bedding. Rocks of Permian, Triassic, and Jurassic age Ore minerals, mainly uraninite, impregnate the rock, crop out in the area mapped, and uranium deposits High-grade ore seams of uraninite and chalcocite occur along bedding planes. Uraninite formed later than, or area is given by McKnight (1940). Below is a brief simultaneous with, most sulfides, and the chalcocite discussion of the stratigraphy and structure of the may be of two ages, with some being later than uran- Shinarump No. 1 mine area. inite. Uraninite and chalcocite are concentrated in the more poorly sorted parts of siltstones. In the Seven Mile Canyon area guides to ore inferred from the study Stratigraphy of the Shinarump No. 1 deposit are the presence of bleached siltstone, carbonaceous matter, and copper Stratigraphic section sulfides. Results of spectrographic analysis indicate that the mineralizing solutions contained important In the Shinarump No. 1 mine area, the Cutler, amounts of barium, vanadium, uranium, and copper, Moenkopi, Shinarump, Chinle, and Wingate formations as well as lesser amounts of strontium, chromium, form an escarpment along the west side of the Moab boron, yttrium, lead, and zinc. fault. The Upper Jurassic Morrison formation on the east side of the fault has been faulted against the The origin of the Shinarump No. 1 deposit Permian Cutler formation. Thus, in the area mapped, is thought to be hydrothermal. Jurassic rocks between the Wingate (Triassic) and Morrison formations are not exposed. A measured INTRODUCTION section of the rocks near the mine follows. The Shinarump No. 1 uranium mine is located Shinarump no. 1 claim section, measured about about 12 miles northwest of Moab, Utah, in the Seven 1. 500 feet south of Corral Canyon. Grand County. Mile Canyon area, Grand County, Utah (fig. 1). A Utah. Line of section S. 65 W.. sec. 27. T. 24 S.. road about a quarter of a mile long connects the mine R. 20 E.. Salt Lake meridian area with U. S. Highway 160. The mineralized zones crop out along a northwest-trending escarpment paral [Measured December 1952] leling Highway 160. Vegetation in the area is sparse. The United States Geological Survey studied the Wingate sandstone (incomplete): geology of the Shinarump No. 1 mine on behalf of the Top of section, not top of exposure. Atomic Energy Commission in order to determine the Sandstone, yellowish-gray (5Y8/1) 1 ; habits, ore controls, and possible origin of the deposit. weathers pale red (1OR6/2); fine-grained Vance Thorriburg, owner of the claims, was most co to very fine grained; bedding not distinct; operative and helpful throughout the investigation. only basal 5 ft examined; estimated height of cliff face 220 ft. Chinle formation and Field study began in January 19 52 and was carried Wingate sandstone contact placed at sharp on intermittently until April 1953. The Shinarump No. 1 change from cliff-forming sandstone of mine workings were mapped in detail by tape and open- Wingate to slope-forming shale and sand sight alidade early in 1952. Later a planetable map was stone of Chinle. Mudcracks at base of made of the area surrounding the mine to relate the mine Wingate; light-green alteration of upper few geology to the stratigraphic and structural features. A inches of Chinle and of mudcrack fillings. total of 31 samples of ore-bearing and barren rock were (Unit not measured.) taken in the area and analyzed chemically and spectro- Unconformity (local?). graphically. Stratigraphic sections were measured near the mine and in Little Canyon south of Seven Mile Canyon. Chinle formation: Shale and interbedded sandstone and con Previous work in the area includes a study of the glomerate, pale-red (1OR6/2); sandstone, geology of the area between the Green and Colorado fine-grained; conglomerate contains mostly Rivers by McKnight (1940) and recent studies of the clastic limestone concretions. Sandstone Seven Mile Canyon area in connection with exploration and conglomerate beds mostly 1 ft or less by the Atomic Energy Commission by Droullard (1951) in thickness. For most part unit forms and Droullard and Jones (1952). steep rubble-covered slope...... 73 Sandstone, light-red (5R6/6), fine-grained; quartzitic; thin horizontal bedding with some GENERAL GEOLOGY low-angle crossbedding; forms ledge; channels into lower unit...... 7 Rocks of Permian, Triassic, and Jurassic Sandstone and mudstone, moderate-red age crop out in the area mapped. Uranium-bearing (5R5/4), fine-grained; irregular bedding; rock occurs in lower beds of the Upper Triassic forms ledge ...... 12 rocks. Copper-bearing rock occurs in a large Sandstone and conglomerate, pale-red (5R6/2) talus block that may be Dakota sandstone of and light greenish-gray (5GY8/1), fine-grained. Cretaceous age and in the Moab fault gouge zone. Conglomerate consists mainly of clastic lime Outside the Shinarump No. 1 mine area, uranium- stone concretions. Abundant hematitic con bearing rock also occurs in the Morrison forma cretions scattered mainly in sandstone beds, tion of Late Jurassic age (pi. 1). Copper-bearing some silicified wood, some white calcite fill rock occurs along the Moab fault northwest of ing cavities and fractures. Irregular bedding the area mapped. and penecontemporaneous slumping. This and upper two beds form a single ledge which di The nearest igneous rocks crop out in the La Sal vides the Chinle into two units; base of unit Mountain laccolith about 20 miles to the southeast. The channels in lower beds and is base of upper major structural features are the Moab anticline and unit of Chinle formation- .... 1° Moab fault. The general geology of the surrounding 1 See footnote p. 3- Chinle formation Continued Feet Moenkopi formation Continued Feet Sandstone, pale-red (5R6/2) fine-grained, Sandstone, very pale-orange (10YR8/2) to thin-bedded; with interbeds of yellowish moderate reddish-brown (10R4/6); fine gray (5X7/2); beds weather with hackly grained, grading to coarse-grained near surface; forms a steep covered slope ...... 64 top; angular quartz grains, abundant Conglomerate, yellowish-gray (5Y7/2); muscovite and biotite; thick-bedded; forms clastic limestone concretions and rounded slope; some bleaching along and some white quartz; pebbles range across bedding ...... 11 from i to 2 inches across; calcareous Total Moenkopi formation...... 20 cement; irregular bedding; forms ledge ..... 6 Unconformity ?). Sandstone and siltstone, moderate red-orange (10R6/6); sandstone, fine Cutler formation: grained, in beds mainly 1ft thick Sandstone and shale, moderate red-brown which form discontinuous channel- (10R4/6); some biotite along bedding; fillings; small scale crossbedding; irregular bedding; forms bench...... 31 some miniature slumping; unit forms slope. .. 48 Sandstone, moderate reddish-brown (10R4/6); Sandstone, grayish-green (5GY6/1), medium- to coarse-grained; some mica; very fine-grained; composed of quartz grains, thickly crossbedded; irregular bleaching along white mica, some carbon flecks; cal some beds; weathers rounded; forms ledge..... 24 careous cement; thin-bedded; weathers Shale, pale-red (10R6/2); contains mud-crack into small irregular crescent-shaped fillings; bleached in places ...... 1 partings; forms slope; lenticular, Sandstone, grayish red-purple (5RP4/2) to channels into lower unit ...... 4 moderate-red (5R4/6), coarse-grained to Siltstone, dark red-brown (10R.3/4); conglomeratic; some white mica and feldspar, some white mica and coarse quartz abundant biotite; thin-bedded to low-angle sand grains; thin-bedded; forms slope; cross lamination; bleached spheres from uranium bearing in places ...... 22 i inch to 1.5 ft in diameter-cutting bedding; Claystone and siltstone, light-green friable; forms ledge. (Base of outcrop, (5G7/4) and light -brown (5YR6/4); some not base of formation)...... 10 fine quartz grains, white and green Total Cutler formation exposed ...... 66 mica, wood fragments; thin -bedded; forms slope; grades into overlying 1 Rock-color chart prepared by "The Rock-Color Chart Committee," beds. Uranium bearing in places; E. N. Goddard and others, National Research Council, Washington, D. C., some wood replaced by uraninite 1948. and becquerelite ...... 22 Cutler formation Conglomerate, greenish-gray (5GY6/1); clastic lime pebbles as much as 2 in. Only the upper 66 feet of the total 1,000 feet or across, some quartz grains, some more of the Cutler formation of Permian age is ex limonitic stains; calcareous cement; posed in the area mapped. The exposed Cutler con uneven bedding; forms ledge. Uranium sists of medium- to coarse-grained sandstone and bearing in upper part, uraninite forms muddy sandstone and pale-red shale. Bleaching along rims about some limestone pebbles...... 13 fractures and bedding planes is common. Cross-laminated Muds tone, pale -red (10R6/2); some lime sandstone forms a prominent rounded ledge near the stone pellets...... 2 top of the Cutler. Locally along the Moab anticline an Conglomerate, pale -green (5G7/2); angular and erosional unconformity exists between the clastic limestone pebbles; calcareous overlying Triassic Moenkopi and the Cutler. However, cement; irregular bedding ...... 1 the contact between Permian and Triassic rocks in the Siltstone and conglomerate, moderate Shinarump No. 1 mine area is difficult to determine. reddish-orange (10R6/6); conglomerate contains clastic limestone pebbles and reworked siltstone pebbles from Moenkopi formation the Moenkopi; abundant limonite staining; some white quartz grains; The Moenkopi formation of Early and Middle( ?) irregular bedding; forms steep slope Triassic age is 20 feet thick in the measured section beneath conglomerate ledge. Uranium near the Shinarump No. 1 mine and pinches out about bearing at Shinarump No. 1 mine...... _7 450 feet to the north, and a few miles south, the Moenkopi Total Chinle formation ...... 297 attains a thickness of about 450 feet. Thin-bedded shale and mudstone, and massive sandstone make up the Shinarump conglomerate absent in line of section. Moenkopi strata. A distinct moderate reddish-brown, Unconformity (erosional). abundant mica, and ripple-marking characterize the Moenkopi. The overlying Upper Triassic beds were de Moenkopi formation: posited on an erosional surface formed on the Moenkopi Shale and mudstone, pale -green (5G7/2) and and, in places, on the Cutler. mode rate -red (5R5/4); mica along bedding; bedding poorly developed ...... Shale, grayish-brown (5YR3/2); some white Shinarump conglomerate and Chinle formation mica; bedding poorly developed ...... Sandstone, mode rate -red (5R5/4) grading The Shinarump conglomerate of Late Triassic age upward into grayish-green (10GY5/2); is absent in most of the area mapped. McKnight showed coarse-grained, massive...... that the Shinarump conglomerate pinches out along an irregular east-west line about 15 miles north of the inter light-green mudstone. Boulders of the Burro Canyon section of the Green and Colorado Rivers, and only iso - or Dakota formations of Cretaceous age cover some of lated outcrops of Shinarump conglomerate were mapped the slope of Brushy Basin exposures. north of this line. One such isolated outcrop was mapped inthe vicinity of Little Canyon (pi. 1). The Shinarump con glomerate in Little Canyon ranges from 5 to 10 feet in Structure thickness and consists of a friable white coarse-grained to conglomeratic quartz sandstone. The Shinarump be The Shinarump No. 1 mine is located on the west comes discontinuous and lenticular near the northern flank of the Moab anticline about 700 feet west of the edge of this outcrop. Siltstone and fine-grained sand Moab fault. The beds strike N. 15° E. and dip 8° NW. stone of the Chinle truncate many of the Shinarump at the mine. The joints occur in two sets; one major lenses. In an opencut adjacent to the Shinarump No. 1 set strikes N. 5°-75° W. and dips 50° NE. to vertical, mine, a white coarse-grained to conglomeratic quartz and a minor set strikes N. 35°-70° E. and dips 70° SE. sand lens corresponding to the Shinarump conglomerate to vertical. is truncated by the fine-grained sediments containing the ore deposit. Thus, the Shinarump north of the main The Moab anticline, a result of salt intrusion, ex area of deposition was deposited as small thin lenses or tends about 15 miles northwest of the Colorado River. channel fills and was, at least in part, removed before The Moab fault, a normal fault, lies a short distance or during the deposition of the overlying Chinle. southwest of the crest of the Moab anticline. The fault extends about 30 miles northwest from the Colorado The Chinle formation of Late Triassic age is River and has a general trend of about N. 45° W. nearly 297 feet thick in the section measured at the mine. In parallel to the axis of the Moab anticline. In the Shina the Seven Mile Canyon area, the Chinle formation may rump No. 1 mine area, the fault has a maximum dis be divided into a lower and an upper unit. The base of placement of about 1, 800 feet and dips about 65° NE. and a prominent ledge of fine-grained sandstone and lime makes a gentle turn to the west near the Shinarump Nos. 1 stone pebble conglomerate that is characterized by and 3 mines. slump-bedding marks the division of the two units. The lower unit is composed of thin- and irregular-bedded The Moab anticline was in existence at the end of light-green to pale-red siltstone, sandstone, and lime Permian time as shown by the angular and erosional un stone pebble conglomerate. Much of this unit is covered conformity between the Cutler and Moenkopi formations. by talus. A limestone-pebble conglomerate bed about McKnight reports that the deformation was renewed in 10 feet above the base of the Chinle serves as a "marker middle Triassic time, prior to the deposition of the ore- bed" in the Shinarump No. I mine area (see section A- bearing Chinle strata, and was resumed once again dur B-C, pi. 1). The upper unit is composed mostly of pale- ing the Laramide orogeny at the end of the Cretaceous red shale and sandstone which forms for the most part period. However, in similar structures on the Colorado a covered slope. Near the Moab anticline the contact Plateau, Stokes and Phoenix (1948) and Shoemaker (1951) between the Chinle and the Wingate sandstone is a local find that the intrusion of salt was continuous from Permian unconformity. to Late Jurassic time; and the author believes the Moab anticline had a similar history. McKnight correlates the Many of the uranium deposits in the area between faulting along the Moab Valley anticline with the normal the Green and Colorado Rivers lie near the northern edge faulting of the Wasatch Plateau that is later than pre- or north of the pinchout of the Shinarump conglomerate Eocene folding and possibly late Tertiary. The Moab (fig. 1). In the Seven Mile Canyon area, the uranium de fault may be related to the Laramide orogeny or the posits lie north of the Shinarump outcrop in Little Canyon. collapse of the salt structures later in the Tertiary or Thus, the uranium deposits are related to the edge of Quaternary periods. Field relations are so obscure that Shinarump deposition on a regional and local scale. the dating of the Moab fault is uncertain. Evidence genet ically relating the uranium deposits in the Seven Mile ' Uranium-bearing rock in the Seven Mile Canyon Canyon area to the Moab fault is lacking. area is found in many zones in the lower unit of the Chinle, but the ore deposits are found mainly in three zones in the lower 25 feet of the Chinle (section A-B-C, pi. 1). HISTORY AND PRODUCTION The Shinarump No. 1 mine is in the lowermost ore zone. In February 1948 Gordon Babbel and Nicholas Murphy, of Moab, Utah, discovered the Shinarump No. 1 Wingate sandstone mine. During the following year, claims were staked throughout the Seven Mile Canyon area, and a few tons The Wingate sandstone of Late Triassic age con of ore was shipped in 1949. The mines were idle during sists of massive yellowish-gray fine-grained sandstone 1950, but in 1951 mining from several prospects was re that weathers pale red and is characterized by surface sumed and since then has been continued intermittently. coatings of black desert varnish. In the Seven Mile Can Over a thousand tons of ore was shipped from the Shina yon area the Wingate, which forms a massive cliff, is rump No. 1 mine between 1948 and January 1953. The over 200 feet thick. Thornburg Mining Company, Grand Junction, Colo. owns the Shinarump mines Nos. 1, 3, and 4. Jurassic rocks ORE DEPOSITS In the vicinity of the Shinarump No. 1 mine, the Brushy Basin shale member of the Morrison formation Copper-bearing rocks occur separate from uranium- of Late Jurassic age is faulted against the Permian and bearing rocks in the Shinarump No. 1 mine area. Copper- Triassic rocks. The Brushy Basin consists mainly of bearing rock is found along the Moab fault and in a talus block that is thought to be Dakota sandstone of Creta Uraninite (pitchblende), ideally UO2 (commonly ceous age. Copper carbonates are found along frac contains UOa), is the principal uranium mineral. It tures and bedding planes as well as disseminated in occurs as microscopic grains mixed with chalcocite sandstone in a prospect in the talus block. Fractured and other sulfides replacing carbonaceous material rock along the fault in an abandoned shaft at the base of and disseminated in siltstone. Rich concentrations the talus block contains copper carbonates. The copper of uraninite occur in seams as much as a half prospects are not commercial in size or grade. Ura an inch thick along bedding planes. nium is not known to be associated with the copper. Some uraninite is slightly altered to a burnt- The uranium-bearing material in the Shinarump orange material resembling gummite, and halos of No. 1 mine area occurs mainly in three zones in the this material are present about unaltered uraninite. lower 25 feet of the Chinle formation. The zones in Schroeckingerite NaCa3 (UO2)(CO3) 3 (SO4)F. 10H2O, ,apale clude, in ascending order, a basal siltstone unit, the yellowish-green mineral, and becquerelite 2UOs.3H 2O, top of the overlying limestone-pebble conglomerate a yellowish-orange mineral, occur along fractures "marker bed," and an irregular dominantLy siltstone and bedding planes near the edges of the deposit zone 5 to 10 feet above the conglomerate. nearest the surface. No secondary vanadium-uranium minerals were found. The highest zone consists of small calcareous nodules of rich concentrations of uranium minerals as sociated mainly with wood and carbonaceous rubble in The sulfides present in the ore are chalcocite, greenish siltstone and minor limestone-pebble conglom pyrite, bornite, chalcopyrite, and blue chalcocite erate beds. Some wood is almost completely replaced (digenite?, solid solution of covellite and chalcocite). by uraninite, which has been altered to becquerelite in All the sulfides, except the blue chalcocite, occur as places. If the frequency of occurrence of nodules is scattered grains in both barren and uranium-bearing great enough, the deposit can be economically mined. rock. Chalcocite and pyrite are more abundant in the At the Shinarump No. 3 mine this zone, although dis uranium-bearing rock. Uraninite is associated with all continuous, is as much as 3 feet thick. the sulfides but most commonly with pyrite and chalco cite. Some malachite is found coating chalcocite. The middle zone is in the upper part of the con glomerate "marker bed" where limestone pebbles are. Gangue materials include barite, calcite, gypsum, rimmed and replaced in part by uraninite. This con and carbonaceous matter. Carbonaceous matter in the glomerate is mineralized north of the Shinarump No. 1 form of leaves, twigs, and small pieces of wood is mine (pi. 1). Most of the uranium-bearing material in most abundant right above the uranium-bearing beds. these two zones is associated with calcite nodules or There is no megascopic difference in the physical limestone pebbles, carbonaceous material, and gray or properties of barren and radioactive carbonaceous green rock. matter. Limonite is rare, whereas hematite is abun dant in places. The Shinarump No. 1 mine is in the lowermost ore zone, which is made up mostly of siltstone with some In both barren and uranium-bearing rock, the interbeds of mudstone, sandstone, and conglomerate quartz has been etched and crushed. Bornite, chalco and ranges from 5 to 10 feet in thickness. Where this cite, pyrite, uraninite, calcite, and barite are later zone is mineralized, the beds are bleached from red to than etching. Fractures in crushed quartz are either gray and green. The saucer-shaped area of bleached void or contain calcite. Uraninite, pyrite, and chalco ore-bearing beds extends from 1 to 15 feet laterally cite are associated with poorly sorted parts of a rock beyond the limits of the deposit. The limestone-pebble and, in general, follow bedding planes. Stringers of conglomerate "marker bed" is fairly uniform and massive these minerals wrap around and are deflected by the throughout the area except above the Shinarump No. 1 de large quartz grains. Many blebs of uraninite and pyrite posit and above the deposit in the lower uranium-bearing are zoned with the uraninite forming rims about fine zone at the Shinarump No. 4 prospect, the thinning and grained pyrite. Pyrite was observed in very fine frac less massive character of this "marker bed" above the tures in siltstone. Chalcocite occurs in vertical vein- deposits in the lower zone may be significant in pros lets as much as half a millimeter wide that strike east- pecting for ore in the Seven Mile Canyon area. west. Nuclear-track plates on thin sections of these veinlets indicated the absence of radioactive minerals. On the basis of the major metal content, uranium However, copper and uranium minerals extend outward deposits of the Colorado Plateau may be divided into along bedding planes away from these fractures. Cal vanadium-uranium, copper-uranium, and uranium. The cite and more rarely barite have filled voids in the rock. Shinarump No. 1 deposit contains only minor amounts of copper and vanadium and thus, is a uranium deposit. Paragenesis of uraninite and sulfides from the Oxidation of the uranium deposits such as the Shinarump Shinarump No. 1 mine is given in figure 2. The con No. 1 is generally slight, and deposits of this type are ventional line diagram is shown with the circular dia less obvious to the prospector because secondary ura gram (Robertson and Vandeveer, 1952) to compare the nium minerals are scarce at the outcrop. two methods of showing paragenesis. The circular diagram shows the minerals observed in contact; pyrite, for example, was observed in contact only MINERALOGY with uraninite and chalcocite. The line diagram shows that some pyrite is later than chalcopyrite even though Other writers have studied the mineralogy of the the two were never observed in contact. It is difficult Seven Mile Canyon area (Weeks, 1952, andRosenzweig, to show two groups of simultaneous minerals in the in report by Droullard and Jones, 1952). Only the min circular diagram. The two diagrams, thus, comple eralogy of the Shinarump No. 1 mine is discussed here. ment each other. by the exsolution of chalcopyrite in bornite. Photo micrograph F of a thin section of sample no. 5 BORNITE CHALCOPYRITE shows the zoning of uraninite and chalcocite about <»$ a pyrite core.
URANINITE CHALCOPYRITE Blue chalcocite observed in one polished section may be digenite, which is a solid solu tion of covellite and chalcocite; however, the common digenite texture is absent. Wandke (1953) points out that if the specimen is heated above 68° C, during the preparation of the sample, CHALCOCITE BLUE CHALCOCITE digenite may be formed from covellite and chal cocite. However, covellite was not observed so that either all covellite was adjacent to chalcocite and transformed or digenite was present before preparation of the sample. The author prepared Simultaneous deposition the specimens in sealing wax which may not have Simultaneous >- Simultaneous with replacing tendency shown by arrows heated the specimen above the critical tempera -> Replacement, example: chalcopyrite replacing bornite ture. The problem of blue chalcocite (digenite?) is important from the standpoint of temperature Lines connect only those minerals observed in contact. of ore formation (Buerger, 1941). Minerals arranged clockwise in approximate order of deposition. Modified after Robertson and Vandeveer (1952) PETROLOGY Bornite Chalcopyrite Samples of barren and uranium-bearing rock Blue chalcocite from the Shinarump No. 1 mine (table 1) were Pyrite studied in thin section, slides of light and heavy grains, and by size analysis. Generally, the Chalcocite ore-bearing rocks are siltstone and fine-grained Uraninite sandstone that are more poorly sorted than the barren siltstone and fine-grained sandstone. Barren Figure 2. Paragenesis of uraninite and sulfide miner rocks include siltstone, fine- to coarse-grained als, Shinarump No. 1 mine, Grand County, Utah. sandstone, limestone-pebble conglomerate, and mudstone. Reworked siltstone and sandstone pebbles In general, in the Shinarump No. 1 deposit and grains from the Moenkopi are common in uraninite is later than or simultaneous with most many beds. Visually, packing is good in both sulfides. Chalcocite may be of two ages with barren and ore-bearing rocks. Calcite and clayey some being later than uraninite. Rosenzweig material cement barren and ore-bearing rock. The (in Droullard and Jones, 1952), writing about the grains are usually subangular to well rounded.. An Seven Mile Canyon area, states: "It appears that gular and broken feldspar is abundant in one ura the time of formation of the copper sulfides fol nium-bearing .siltstone sample. lowed closely or possibly overlapped that of uran inite. " Thus, the paragenetic relationship of uran The composition of light constituents, specific inite and sulfides in the Shinarump No. 1 deposit gravity less than 2.9, of the uranium-bearing and found by this study is not in complete agreement barren Chinle samples is mostly quartz and chert, with the Seven Mile Canyon area taken as a unit. and minor amounts of microcline, muscovite, orthoclase, and oligoclase are present. Some chert grains contain Photomicrographs in figure 3 show some of pyrite cubes. Heavy nonopaque detrital minerals, spe the paragenetic relationships. Chalcocite cross- cific gravity greater than 2.9, include mostly zircon, cutting uraninite that has completely replaced tourmaline, and biotite, with minor amounts of rutile, wood is shown in photomicrograph A. Photomi chlorite, spinel, garnet, and staurolite. Opaque detrital crographs C and D show the relationship of minerals include ilmenite, leucoxene, and hematite. etched quartz grains, uraninite, and chalcocite. Authigenic barite is abundant in both barren and uranium- Note the uraninite-free areas surrounding the bearing rock and has been precipitated in open spaces. etched quartz grains. A peripheral line of uran Counts of the heavy detrital minerals from barren and inite is concentric with the shape of the etched uranium-bearing samples show no correlation of any quartz grain. Stringers of uraninite radiate from mineral or group of minerals with uranium-bearing rock. these peripheral lines. It appears that cracks may have formed in the chalcocite and were X-ray spectrometric determinations of material later filled with uraninite. Other, but less likely, smaller than 4 microns, from barren and ore-bearing explanations are that these crack fillings repre samples made by the trace elements laboratory of the sent the replacement of crushed or distorted Geochemistry and Petrology Branch of the Geological cellular structure of wood or that chalcocite re Survey, indicate the presence of quartz (fine crypto- placed quartz grains in places and the uraninite crystalline?), hydro mica, and kaolin in every sample. replaced the interstitial clay material. Photomi Some samples contain small amounts of feldspar, crograph E shows a texture interpreted as caused calcite, dolomite, chlorite, and montmorillonite. Figure 3. Photomicrographs of polished and thin sections from the Shinarump No. 1 mine, Grand County, Utah. A, Polished section of sample 22 showing replacement of wood by uraninite (U, light gray) and chalcocite (Cc, white). B, Polished section of sample 23 showing relation of chalcocite (Cc, white) and Uraninite (U). C and D, Polished section of sample 23 showing etched quartz (Q, dark gray) grains surrounded by chalcocite (Cc, white), which is free of uraninite (U, light gray), and uraninite filling minute cracks in chalcocite that are oriented radially about the quartz. E, Polished section of sample 26 showing texture interpreted as caused by exsolution of chalcopyrite (Cp, white) in bornite (B, light gray), replacement of bornite by chalcocite (Cc, dark gray), and uraninite (U, medium gray) cutting all other minerals. F, Thin section of sample 5 with reflected and transmitted light showing bleb of minerals, pyrite (Py, light gray) surrounded by border of chalcocite and uraninite (Cc-U, black) in sandstone. Note encroachment of quartz (Q, white) by ore minerals. Table 1. Samples from Seven Mile Canyon area
Sample Description no. Specific location1 1 Wall MN Uranium-bearing unbleached siltstone stringers. 2 Uranium-bearing sandstone; very fine to coarse grained. 3 do , Limy siltstone. 4 Wall GH Highly radioactive carbonaceous material. U«1 1 MINI ------Uranium -bear ing muddy siltstone. 6 _ __7To - _ _ _ - _ - _ Uranium-bearing silty sandstone. 7 Uranium-bearing siltstone . 8 -Wall CD Uranium-bearing silty sandstone. 9 do Uranium-bearing siltstone . 10 Wall EF Muddy siltstone; forms back of mine. 11 do Limestone pebble conglomerate above ore. 12 Uranium-bearing siltstone . 13 Wall EF Limy sandstone below ore. 14 do Barren siltstone. 15 Wall CD Uranium-bearing siltstone north of fracture. 16 do Barren siltstone north of fracture. 17 do Altered siltstone south. of fracture. 18 do Unaltered siltstone south of fracture. 19 Wall IJ Nonradioactive carbonaceous material. 20 Secondary copper minerals in Moab fault zone. 21 Copper-bearing material from Moab fault zone. 22 20 feet N. 3° W. of station R3 Fractures filled with chalcocite. 23 28 feet N. 11° W. of station. R3 Uraninite and chalcocite layer. 24 Wall CD Conglomerate below ore. 25 Kellog No. 1 claim2 Uranium-bearing sandstone from the Morrison formation. 26 Uraninite, bornite, chalcocite in seam. 27 North portal3 Barren siltstone from the Chinle formation. 28 Barren sandstone from the Shinarump conglomerate. 29 Wall IJ Uranium-bearing siltstone, chalcocite veins. 30 Wall KL Uranium-bearing siltstone and sandstone. 31 Little Canyon 2 Conglomeratic sandstone from the Shinarump conglomerate
'Plate 2 unless otherwise noted. 2Plate 3 Figure 7.
Figures 4, 5, and 6 show the results of size The results of the size analysis of 4 samples analysis. Sample 31 (figs. 4, 5) came from the are given in figure 6. Study of frequency curves Shinarump conglomerate in Little Canyon (pi. 1), and thin sections shows the siltstone to be more and sample 28 (figs. 4, 5) was taken from near poorly sorted to the north, on the mineralized the mine from a lens of a. similar sandstone side of the fracture, than to the south. Study of which has been eroded and cut out by the over the light and heavy detrital minerals shows no lying ore-bearing siltstone of the Chinle. The correlation of any mineral or group of minerals two samples have the same mineral suite, which with the uranium-bearing part of the siltstone. differs from the suite in the Chinle samples. The However, spectrographic analysis of these samples frequency and cumulative curve-j of the two samples indicates a marked increase of some elements in are similar. It is concluded that the lens near uranium-bearing rock over barren rock but no the mine is an erosional remnant of Shinarump difference between bleached and unbleached rock. near the margin of Shinarump deposition. The The increase of some elements in uranium-bearing coarse grains in several samples cause bimodal rock is not reflected as a halo about the uranium- frequency curves (fig. 5A, samples 7, 8; fig. 5C, bearing rock. The position of the fracture with sample 24), which suggest a source for the coarse relation to uranium-bearing and bleached rock is grains similar to the Shinarump or that the coarse probably a coincidence as the spatial relationship grains came from the Shinarump that was partly of this fracture along strike shows no similar re eroded before the deposition of the Chinle. Ura lationship to uranium-bearing or barren rock. nium-bearing samples are more poorly sorted than barren samples. The results of the petrographic study show the uranium-bearing rock to be more poorly sorted A special study was made of a single silt- than barren rock. Detrital grains in the uranium- stone bed along wall C-D (pi. 2) to find what bearing and barren rock are essentially the same changes might be evident in a mineralized and in mineralogy and quantity. The mineralogy of bleached bed. A fracture between the uranium- the coarse fractions of the ore-bearing beds in bearing rock and the unaltered rock is parallel dicate original source rocks to be schists and to the truncated ore as well as the line between acid to intermediate igneous rocks. The ore- bleached and unbleached rock. The possible effect bearing beds are thought to be mostly second- of this fracture on mineralization was also studied. cycle and partly third-cycle sediments. 1.00 percent U 3O 6. Near the edges of the deposit, the ore layer tends to rise in the beds so that the deposit in cross section is saucer shaped '~ . (maps of mine walls AB, CD. pi. 2). The north edge
I-*" ' ' "" ^ 80 of the deposit has an east-west trend. The ore- X^ bearing beds lie essentially flat and fill irregular i *° ''/ ities of an erosional surface. Structural contours w *° f- V on the top of the Moenkopi indicate that no channel 0, scour is present in the vicinity of the mine. 20 \ ^ Most of the deposit is composed of siltstone 0 T ! ^im '' C) 1 2 56 7 8 9 10 11 i; and fine-grained sandstone impregnated with micro 0SCALE scopic grains of uraninite, chalcocite, and pyrite. A. Ore-bearing Chinle samples High-grade layers as much as half an inch in thickness of chalcocite and uraninite are found along some bedding planes. In one place, the high-grade ore is concentrated along the base of - <' ^_ ^~- ^.^ a bed that overlies a less permeable appearing 80 ^' I3y. bed (pi. 2, map of mine wall IJ). Vertical veinlets IO 5 of chalcocite lead upward to this concentration. 60 y / The original color of sediments that contain 'S the deposit is thought to have been red that was 20 >fc . ~- 0 _ ^ -I 1 234567 10 11 12 *SCALE B. Barren Chinle samples
*N j*^ ^S 5S-« ^ ' "A31 y" I% 60 >' « ,0 31 3 £ It / -101 23456 ^» * SCALE .- /+ ft $ _^ A. Ore-bearing Chinle samples -10123456 8 10 11 12 0 SCALE C. Barren Chinle (Nos. 14 and 24) and Shinarump (Nos. 28 and 31) samples
Figure 4. Cumulative curves of grain size of samples from the Seven Mile Canyon area, Grand County, Utah. Scale is the phi scale of Krumbein (1934).
HABITS OF ORE BODIES -1 123456 The Shinarump No. 1 mine was mapped in plan
-- - "^ bearing rock from nearby copper prospects in the Moab ****** -_-^rr.-^: .-r^- fault, and uranium-bearing rock from the Kellog No. 1 80 ** mine (pi. 2) in the Morrison formation are shown in '£s table 2. The samples were tested for 26 other elements but I 60 /. U none were detected. In all groups of samples, common rock W 40 forming elements show no systematic variation. Com ft / / parison of barren and uranium-bearing rock from the 20 y Shinarump No. 1 mine shows a substantial increase in *** 0 ,__ / the uranium-bearing rock of the elements boron, beryl 1012345.67 9 10 11 12
4580' Uranium-bearing rock
4570'
EXPLANATION
Backfill in mine
Boundary of uranium-bearing ground, dashed where inferred
Chalcocite vemlets
Contact, dashed where inferred
Strike and dip of joint
Barren drift
Extent of workings, February 1952
Sample number 0 A Survey stetion
Boundary of opencut
RADIOACTIVITY MEASURED ALONG WORKINGS WITH A BETA-GAMMA GEIGER COUNTER
More than 2000 counts per minute and 1 foot or more thick
More than 2000 counts per minute and less than 1 foot thick
Between 20 and 2000 counts per minute any thickness
80 Feet
Figure 7. Geologic map and sections of the Shinarump No. 1 mine, Grand County, Utah. Table 2. Geometric mean values (in percent) of elements contained In barren and uranium-bearing rock from the Shlnarump No. 1 mine, copper-bearing rock from nearby copper deposits, and uranium- bearing rock from a nearby deposit In the Morrlson formation.
[Geometric mean in percent calculated from spectrographic analysis. Looked for but not found: As, Au, Bi, Ce, Ge, In, IT, Hf, Hg, Li, Nb, Os, P, Pd, Pt, Re, Rh, Ru, Sb, Sin, Ta, Te, Th, Ti. Yb, and W] Chlnle Copper- Morrlson Chlnle Copper- Morrlson Chlnle uranium- uranium- Chlnle uranium- uranium- Element barren bearing bearing bearing Element barren bearing bearing bearing rock1 rock2 rock3 rocku rock1 rock2 rock3 rocku zn CM 30 30 30 Be 0.0001 0.001 0 0 M ______2 4 2 .3 .01 .05 .005 r\f\£. 1 2 .4 .3 Y .002 .01 .001 .003 TJo ______.1 .3 .07 r\f. Ce ( 5 ) 0 0 0 TiVa______1 2 .5 2 Nd ( 5 ) 0 0 0 Mn .03 .02 .03 .03 V .02 .2 .03 .2 Ca 5 2 2 2 Nl .0009 .008 .002 .003 Mg .6 1 .2 .3 Co .0003 .008 .002 .02 Ba .07 .2 .1 .02 Oi i .05 .2 5 2 Q in .02 .03 .007 .02 Pb .002 .03 .003 HTH ______.2 .2 .06 .2 Zn 0 .03 0 .2 <7f> ______.02 .04 .02 .02 Cd 0 ( 5 ) 0 .003 Cr .006 .01 .002 .02 Mo ( 5 ) .003 .001 .02 Ga .0004 .002 0 .0002 Sn 0 ( 5 ) 0 0 Q « .002 .002 0 0 Ag ( 5) .0007 .002 .02 La (0 0 0 0 u 0 1 0 .06
1 Result of analyses of 10 samples from Shinarurap No. 1 mine. 4 Values of 1 sample. 2 Result of analyses of 7 samples from Shinarurap No. 1 mine. Detected in too few samples to take geometric mean. 3 Result of analyses of 2 samples.
AGE DETERMINATIONS OF UEANINITE ORIGIN OF DEPOSIT
The following is a resume of the lead-uranium For many years the uranium deposits on the age determinations of some uraninite specimens Colorado Plateau, which included mostly oxidized from Triassic and Jurassic sedimentary rocks of vanadium-uranium deposits (carnotite-type) of the the Colorado Plateau by Stieff and Stern (1953). Morrison and Shinarump formations, were considered As part of their study on the origin of uranium to have been formed shortly after the deposition deposits in the Triassic and Jurassic sedimentary (penesyngenetically) of the enclosing sediments rocks of the Colorado Plateau, 21 samples of (Fischer, 1942). However, owing to concentrated in uraninite from 13 deposits were collected for vestigations during the past several years and to the dis Pb 206U236 age determinations. These uraninites covery of relatively unoxidized uranium deposits of the' are believed to be the most reliable of more than vanadium-uraniurn, copper-uranium, and uranium types 100 samples from the plateau on which age deter in many different formations of the Colorado Plateau minations have been made. The average age of and adjoining regions, several hypotheses that had been the uraninites from the Morrison is lower by a previously discarded are being reconsidered. These in factor of two than the best estimate of the age clude hydrothermal origin, downward leaching of ura for the Morrison formation. The average age of nium from volcanic strata, and petroliferous origin. A the uraninite samples including the Chinle forma brief statement of the fundamentals of each of the hypo tion in the one from Shinarump No. 1 mine (fig. 7), theses follows. from the Shinarump conglomerate is lower by a factor of three than the best estimate of the age The penesyngenetic hypothesis may be best ex of the Shinarump conglomerate. The average age of pressed by quoting Fischer. samples from the Upper Jurassic Morrison forma tion does not differ significantly from the average The primary ore minerals are thought to have been age of samples from the Upper Triassic Shinarump introduced into their present position not long after the sands were deposited. If this is true, the metals were conglomerate. The average age of samples from the probably transported and deposited by ground waters, and two formations agree very closely with the best the ores were probably localized by delicate chemical and available estimates for the age of the end of the physical conditions that now cannot be definitely recog Cretaceous or the beginning of the Tertiary periods. nized. This hypothesis probably requires at least three separate periods of ore deposition, to account for the Stieff and 'Stern conclude that ore in the Shinarump, Entrada, and Morrison formations.
Most of the lead-uranium data that we have ob Since his studies, deposits have been found in the Hermit, tained strongly suggests that the deposits are not Cutler, Moenkopi, Chinle, Todilto, Dakota, Mesaverde, syngenetic but were emplaced in the sediments dur Wasatch, Uinta, and other formations on the Colorado Pla ing the Tertiary, long after the enclosing sedljnents teau. were laid down. If, however, the deposits are syn genetic in origin, an event must have occurred at the The concept of a hydrothermal origin of the uranium end of the Cretaceous or during the Tertiary which deposits received impetus from the results of age determi completely redistributed the uranium and localized the nations of uraninite specimens from uranium deposits of the ore in its present sites. Colorado Plateau (Stieff and Stern, 1953). The hydrothermal 12 hypothesis suggests that uranium-bearing solutions were CONCLUSIONS related to Tertiary igneous activity and that solutions moved vertically along fractures and then laterally until The Shinarump No. 1 deposit, which is located on the reaching favorable loci where the uranium was deposited. west flank of the Moab anticline, is inthelowermostsiltstone beds of the Chinle formation that truncate erosional remnants Downward leaching of uranium from volcanic of Shinarump conglomerate. Uranium deposits in the Seven strata has been suggested because of the thick Mile Canyon area and elsewhere to the south and west are series of strata containing abundant volcanic de near the margins of Shinarump deposition. There is no evi bris that overlie both the Salt Wash sandstone dence to show a definite genetic relationship of the Moab member of the Morrison formation and the Shin- fault to the uranium deposits in the Seven Mile Canyon area. arump conglomerate. Waters and Granger (1953) suggest that the devitrification of this volcanic The ore is relatively unoxidized. Uraninite material provides the silica for silicification of (pitchblende), a primary mineral, is the most abundant ore wood as well as for the addition of silica in the mineral. It occurs as small grains disseminated in sand ore-bearing sandstones. Others (Proctor, 1949, stone and replacing wood structure. Uraninite, which is as and Love, 1952) have suggested these and other sociated mainly with chalcocite and pyrite, is later formed strata containing volcanic material as source rocks than most sulfides except chalcocite, whichis, in part, later. for the uranium. Chalcocite occurs in vertical fractures that trend east. The ore minerals occur in more poorly sorted parts of siltstone Uranium-bear ing material and petroleum have and in stringers of coarse sand in siltstone. the same suite of trace metals, and thus a com The ore deposit is not in a channel fill but mon origin has been suggested (R. Erickson, oral in flat-bedded sedimentary rocks that were deposited communication). on an irregular surface. Guides to ore in the Seven Mile Canyon area inferred from the study of the Any hypothesis must account for all of the Shinarump No. 1 deposit are the presence of bleached following relations or facts before it can be ac siltstone, carbonaceous material, and copper sulfides. cepted as a satisfactory explanation of the origin The deposit lies below thin parts of the limestone- of the deposits: pebble conglomerate "marker bed. "
(1) Sedimentary structures, such as channels The origin of the Shinarump No. 1 deposit is prob and lenses, and sedimentary features ably hydrothermal. Mineralizing solutions hydrothermal such as bedding planes, graded bedding, and, in part, ground water are thought to have been and impervious "barriers controlled the reducing in character and to have contained important location of most of the ore deposits. amounts of barium, vanadium, uranium, copper, and sulfur as well as lesser amounts of strontium, chromi (2) Bleaching of red mudstones to gray or green accompanies most deposits. um, boron, yttrium, lead, and zinc.
(5) Most deposits are in continental- type sediments. LITERATURE CITED (h) Most deposits are associated with car Buerger, N. W., 1941, The chalcocite problem: Econ. bonaceous material.. Geology, v. 36, no. 10, p. 19-44. (5) The common age indicated by age de Fischer, R. P., 1942, Vanadium deposits of Colorado terminations . and Utah: U. S. Geol. Survey Bull. 936-P. Kruinbein, W. C., 1934, Size frequency distribution (6) The persistent association of uranium with of sediments: Jour. Sed. Petrology, v. 4, p. 65-77. vanadium in the Morrison formation and Love, J. D., 1952, Preliminary report on uranium de the variety of element associations in posits in the Pumpkin Buttes area, Powder River cluding vanadium and copper in the Basin, Wyoming: U. S. Geol. Survey Circ. 176. Triassic formations. McKnight, E. T., 1940, Geology of the area between Green and Colorado Rivers, Grand and San Juan The origin of the Shinarump No. 1 deposit, which Counties, Utah: U. S. Geol. Survey Bull. 908. is clearly later than enclosing sedimentary rocks, is Robertson, F., andVandeveer, P. L., 1952, A new dia thought to be hydrothermal. Age determinations by grammatic scheme forparagenetic relations of the ore Stieff and Stern (1953) indicate that the uraninite in this minerals: Econ. Geology, v. 47, no. 1, p. 101-105. deposit formed at the end of the Cretaceous or the be Shoemaker, E. M., 1951, Internal structure of the Siribad ginning of the Tertiary periods. The mineral assem Valley-Fisher Valley salt anticline, Colorado and Utah blage, particularly the presence of uraninite, blue (abs.): Geol. Soc. AmericaBull., v. 62, no. 12, part 2. chalcocite (digenite ?), and bornite-chalcopyrite solid Stokes, W. L., and Phoenix, D. A., 1948, Geology of solution, strongly suggests a temperature of formation the Egnar-Gypsum Valley area, San Miguel and Mont- warmer than the temperature of normal ground water. rose Counties, Colorado: U. S. Geol. Survey Oil The localization of the ore is related to the pinchout and Gas Inv., Prelim. Map 93. of the Shinarump conglomerate on a regional and local Wandke, A. D., 1953, Polishing phenomena in the scale and to sedimentary features such as bedding copper sulfides: Econ. Geology, v. 48, no. 3, p. 225-232. planes, graded bedding, and sorting, within ore- Waters, A. C., and Granger, H. C., 1953, Volcanic bearing beds. Carbonaceous and clayey material may debris in uraniferous sandstone and its possible have acted as a chemical and physical attraction for bearing on the origin and precipitation of uranium: the localization of the ore. Ground water probably U. S. Geol. Survey Circ. 224. played an important role in the precipitation of the Waugh, A. E., 1943, Elements of statistical method: uranium and sulfides. McGraw-Hill Book Co., Inc., p. 99. 13 UNPUBLISHED REPORTS
Droullard, R. F., 1951, Prospective bulldozer oper Stieff, L. R., and Stern, T. W., 1953, The lead- ations in the Seven Mile area: U. S. Atomic Energy uranium ages of some uraninite specimens from Commission RMO 689. Triassic and Jurassic sedimentary rocks of the Droullard, R. F., and Jones, E. E., 1952, Geology of Colorado Plateaus: U. S. Geol. Survey Trace The Seven Mile Canyon uranium deposits, Grand County, Elements Inv. Rept. 322. Utah: U. S. Atomic Energy Commission RMO 815. Weeks, A. D., 1952, Summary report on mineral - Proctor, P. D., 1949, Geology of the Harrisburg ogic studies of the Colorado Plateau through (Silver Reef) mining district, Washington County, April 30, 1952: U. S. Geol. Survey Trace Ele Utah: Unpublished doctoral dissertation, Ind. Univ. ments Memo. Rept. 431.
GROUP-NUMBER CLASSIFICATION
Assay Group Assay Group (report in no. 1 Class range Class mark (report in no. 1 Class range Class mark percent) percent) XX. + 1+ 46.4 -100.0 68.1 O.OX+ 4+ 0.046 - 0.09 0.068 XX. 1 21.5 - 46.3 31.6 .OX 4 .022 - .045 .032 XX.- 1- 10.0 - 21.4 14.7 .ox- 4- .010 - .021 .015 X.+ 2+ 4.6 - 9.9 6.8 .OOX+ 5+ .0046 - .009 .0068 X. 2 2.2 - 4.5 3-2 .oox 5 .0022 - .0045 .0032 X.- 2- 1.0 - 2.1 1.5 .oox- 5- .001 - .0021 -.0015 ,x+ 3+ .46 - .9 .68 .OOOX+ 6+ .00046 - .0009 .00068 .X J> .22 - .45 32 .ooox 6 .00022 - .00046 .00032 .X- > .10 - .21 .15 .ooox- 6- .0001 - .00021 .00015
^Subgroups overlap somewhat, but about 80 percent of cases will be io correct subgroup.
14 XHT.-DUP. sec., WASH., D.C.«T«II GEOLOGICAL SURVEY CIRCULAR 336 PLATE 1 R. 20 E. S. L M.
Summerville formation
Eotrada sandstone, Moab tongue
Shinarump conglomerate
Cutler and Rico formations
Strike and dip of beds
After McKnlght, 1940
3 Miles Copper prospect
25
Sample number
EXPLANATION
Contact, dashed where inferred
Fault, showing dip; U, upthrown side; O, downthrown side
located quarter corner Strike and dip of beds
_7O Strike and dip of joints
Strike of vertical joint!
Ground underlain by uranium-bearing rock
Shinarump conglomerate.
Contour Interval 40 feet D»tum la metn ft* level
SHINARUMP SHINARUMP NO 1 MINE NO 3 MINE Uranium-bearing rock
Conglomerate "marked bed'
Topography modified after advanced Geology by W. I. Finch topographic quadrangle Moeb 4 NW. Surveying by M. L. Mitigate, Grend County, Utah GEOLOGIC MAPS AND GENERALIZED SECTIONS OF THE SEVEN MILE CANYON AND SHINARUMP No. 1 MINE AREAS, GRAND COUNTY, UTAH W. I. Finch, and others GEOLOGICAL SURVEY CIRCULAR 336 PLATE 2 SKETCH SHOWING LOCATION OF MAPS OF MINE WALLS
SHINARUMP NO I MINE
4575-
4675'-
Muddy siltstona. bentonitic
OX* Carbonacaous matartai
Boundary of uranium-bearing rock
Trace of Joint or fracture surface Hi plane of watt
Sample number
i i i Boundary of red (unbleached) sediments, hachure Indicate* red side
-4575'
4570' :': ' JJ^^7^7^^^
Datum is mean sea level Geology by W. I. Finch SELECTED MAPS OF MINE WALLS FROM THE SHINARUMP No. 1 MINE, GRAND COUNTY, UTAH