Sandstones, uranium deposits

Adams, S.S. Smith, R.B. 1988. Geology and recognition criteria for sandstone uranium deposits in mixed fluvial-shallow marine sedimentary sequences, South Texas. Bendix Field Engineering Corporation, Grand Junction, Colorado NURE Report GJBX-4(81), 146 p. 

The Earth s crust contains an average selenium content of0.05-0.09 mgkg approximating that of cadmium and antimony and ranking above molybdenum, silver, mercury, and uranium. Higher concentrations of selenium are found in volcanic rock (up to 120 mgkg ), sandstone, uranium deposits and carbonaceous rocks (Elkin 1982, Fishbein 1983, Einbrodt and Michels 1984, Merian 1985, Jacobs etal. 1977). There are... 

Peterson F. and Turner-Peterson C. E. Lacustrine-humate model sedimentologic and geochemical model for tabular sandstone uranium deposits in the Morrison Formation, Utah, and application to uranium exploration. Open File Rep. U.S. geol. Surv. 80-319, 1980, 46 p. 

Brisset, F. (2000). Fluid Regime in the Kombolgie Sandstone Uranium Deposits, Northern Territory,... 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

Lithium isotopes do not fractionate as a result of redox reactions, but Li is preferentially partitioned into the fluid phase, whereas Li prefers sites in alteration minerals such as micas. The Li/ Li ratios of mica and chlorite in alteration zones around uranium deposits are higher and decrease to lower values with distance from the ore relative to background mica in the Athabasca Group sandstones. In barren areas, high ratios are rare and background ratios are dominant. When used together, the isotopic composition of uranium and lithium can be utilized to refine both the genesis of uranium deposits and as exploration tools. 

Unconformity-type uranium deposits, as well as sandstone-hosted deposits, should be zoned in their 238y 5y pg jgg gg g result of two processes. In the first process, the 238y 235y... 

Fig. 2. General alteration and geologic features of basement- and sandstone-hosted uranium deposits showing distributions in U and Li isotope ratios.

Geochemical detection of uranium deposits in sandstone-type deposits depends on the geochemical behavior of U and pathfinder elements (Rose Wright 1980). Uranium is dispersed under oxidizing conditions but is immobile under reducing conditions. Adsorption on freshly precipitated Fe-oxides and certain types of organic matter also limits dispersion unless high concentrations of or... 

Sandstone around the uranium deposits typically has radiogenic ° PbF° Pb isotope ratios (>30) (Fig. 5), with Pb isotopic compositions that are unsupported by the amount of U in the sandstone. This is consistent with the introduction of this Pb... 

Deep-penetrating geochemical exploration for hidden sandstone-type uranium deposits in the Turpan-Hami basin, northwestern China... 

Keywords deep-penetration, geochemistry, expioration, sandstone-type, uranium deposits... 

Traditional exploration for sandstone-type uranium deposits has centered on genetic models and radiometric methods (Morse 1969 Harshman 1970 Rubin 1970). However, these methods have become prohibitive for sandstone-type uranium deposits hidden at a depth of hundreds of metres (Riese et al. 1978). Radioactivity detectors are ineffective in regions where there is a relatively thin inactive overburden (Bowie etal. 1970). 

Conventional regional soil geochemical surveys based on coarse fractions of soils (>20 mesh) to avoid windblown sand dilution for elemental contents failed to delineate uranium geochemical anomalies for blind sandstone-type uranium deposits in desert basin terrains in China. 

Three geochemical provinces of U and Mo were delineated in the Turpan-Hami Basin (Fig. 3). The westernmost one contains the Shihongtan large sandstone-type uranium deposit. Sandstone-type uranium deposits are characteristic by coexisting U and Mo anomalies. The east one at Hami area is was selected for follow-up exploration and a big deposit was found by drilling program. 

Sandstone-type uranium deposits are characteristic by coexisting uranium and molybdenum anomalies. 

Fig.1. Bar graphs showing the concentrations of various elements in different size fractions of soil over the Shihongtan sandstone-type uranium deposit.

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