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Tea Piute Range in the west-central part of Lincoln County, ffevada, approximately 85 mile* vest of Caliente, 100 Biles east of Tonopah, and 160 Biles north of Las Yogas. The district is reached by 40 Biles of desert road froB B. S. Highway 93 at Crystal, near Hiko. The deposits

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Introduction __ ______________ __ __________ _ 238 Purpose of the investigation.___ _ _ __ 239 Field work and acknowledgments _ __. ____ _ 239 Previous work._ __._ _____________ _____________ ___ 239 Location and physiography __________ ____________ ______ 240 Accessibility_____________________.___._________ 240 General geology 241 Sedimentary rocks-_ ____________________ __ ___ 241 Igneous rocks______ _________________ _________ ___ 242 Structure______________ _ _ _ _ _. 242 Geologic history 243 Radioactivity.- .-__ __________________________ ____ 244 Uranium deposits 245 Uraniferous lignite. _________________________________ _ 246 Distribution______________________________ 246 Geology_________________________________ 248 Radioactivity.-________________________ _ ______ 250 Origin______.__ ..________.____________-_ 253 Lost Creek schroeckingerite deposit______________________ 254 Location and history _ ______________ ____ 254 Geologic setting. _______ ________ _________ ______ 256 Mineralogy _______ ___ _________ _.__-. 260 Schroeckingerite_______________________________ Other uranium minerals._________________________ Ore bodies___________._____________._____.-Grade_________.._____________________... Auger-testing program of 1950__ __ Sampling and logging procedures__________________-_____ Geologic results.._______________________ Distribution of uranium____________________________ Origin___________________________________ Aids to prospecting______________________________________ Future outlook__________________________________ Literature cited.._______________________________ Stratigraphic sections... _________ ___ _ _ Analyses....______________________________________________ Auger-hole data.____________________________________________ Index________________________________________ 307 m Page TABLE 1. Comparison of radioactivity measurements, Red Desert,Wyo_ 245 2. Summary of paleontologic data, Red Desert, Wyo______ 249 3. Analyses of material other than lignite, carbonaceous shale, schroeckingerite, or water, Red Desert, Wyo_____________ 4. Analyses of water samples (ppm), Red Desert, Wyo__-___._ 5. Spectrographic analyses (in percent), of uraniferous lignite, Red Desert, Wyo____________________________ 284 6. Analyses of radioactive lignite, carbonaceous shale, clinker, and ash, Red Desert, Wyo_______________-7. Analyses of rock samples, Lost Creek schroeckingerite deposit.

Igneous processes tend to concentrate uranium in late phase differentiates of magmas, notably in pegmatites, small alkalic plutons, and veins and other epigenetic deposits. The concentrations in igneous rocks are syngenetic. They may be large but are low-grade. Vein and other epigenetic deposits associated with igneous rocks are generally relatively small, but some are high-grade. Weathering and sedimentary processes may either disperse or concentrate uranium, depending primatily on climate. Some primary , uranium-bearing minerals accumulate in placers. Others are dissolved and the uranium is transported by ground and surface waters from which it may be precipitated in favorable receptors to form epigenetic deposits. Most deposits thus formed are relatively low-grade but some are large. Some uranium in solution reaches the sea and may be extracted to form large low-grade accumulations in phosphorites or black fhales, Metamorphic processes may affect concentrations of uranium either by converting pre-existing rocks to magma, which subsequently may form uranium-rich differentiates, or by "sweating" uranium out of weakly uraniferous rocks and concentrating it in favorable geologic settings.Most of the world's important uranium deposits are clustered in a few areas or provinces that perhaps represent uranium-rich portions of an originally inhomogeneous crust. These uranium-rich provinces apparently persist through long periods of geologic time. Within them, some types of uranium-rich rocks and uranium deposits may be relatively short lived, depending on the geologic history and climate; but, as they are destroyed by erosion or metamorphism, others in equilibrium with the prevailing environment may form.

The Treasure Hill area consists of eight mining-lode claims in secs. 10 and 15, T. 9 N., R. 70 W., Larimer County, Colo. All of the workings were examined and samples were taken from most of them. The results of the examination indicate that there is little or no detectable radioactivity in the schist and granite of the area.

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