Uranium deposits, types shales

Furongite was described by the Hunan 230 Laboratory as a yellow, minutely crystalline deposit on carbonaceous shale in the oxidized zone of an illuvial-type uranium deposit. Walenta and Wimmenauer described hallimondite from Lahr, Baden. It is very similar to parsonsite. Pseudo-autunite was characterized by Sergeev from fenitized rocks of the exocontact zone of a massif of ultrabasic-alkaline rocks of northern Karelia, U.S.S.R. Walpurgite-(P), an unnamed phosphate analogue of walpurgite, was described in Soboleva and Pudovkina. ... 

Uranium deposits in this unit are of numerous geological types, but three are typical of the Hercynian orogen (1) intra-granitic deposits related to leucogranites, (2) deposits bound to the contact-metamorphic haloes of granite intrusives in Lower Palaeozoic shales (the so-called Iberian type ) and (3) deposits bound to Permian cover rocks or Permian acid volcanics. Other types are veins in less differentiated granites, veins in metamorphic environments, sandstone-type deposits in Mesozoic or Caenozoic cover rocks in basin structures of the Hercynian space included in or adjacent to the Moldanubian zone (or its Iberian equivalent). 

Phosphorites that are richest and thickest and contain the most uranium are the miogeosynclinal type deposited on the outer parts of continental shelves where upwelling of deep marine waters has occurred. These waters were saturated with respect to phosphate and were probably the source of the phosphate in the phosphorites. These phosphorites are commonly present in thick miogeosynclinal sequences, where they are associated with carbonates, black shale, chert, carbonaceous mudstone and minor amounts of mudstone. " The Phosphoria Formation of the western U.S.A. is an example. 

The Precambrian European province proper contains limited resources in vein-type deposits in northern Sweden and, again, a huge low-grade uranium natural stock in Cambrian black shales. Grades, under present market conditions, are not economic. 

This model for uranium mineralization associated with granites requires (1) a metalliferous Sn-U mildly alkaline type or transitional granite to rise to a level in the crust where it will create a thermal anomaly (2) adequate water of suitable chemistry for hydration and reduction of primary silicates (thus rocks of low metamorphic grade and more pelitic composition, particularly graphitic shales, will favour mineralization) and (3) a well-developed fracture system, particularly for low-temperature mineral deposition. 

---