Anthraxolite-Uranium Mineral: Composition, Structural Features and Genesis

Abstract

The most common uranium minerals are uraninite, coffinite and ningyoite. From a mineralogical point of view, anthraxolite is particularly interesting because it is a mixture of bitumen, uraninite and a small amount of coffinite while its composition has been significantly influenced by radiation metamorphism. As a mineral, it is light, hard, crumble, black in color with a brownish cut, matte sheen and a conchoidal fracture. Anthraxolite is always bound to the accumulation of uraninite, often metasomatically replacing uraninite. In the case of uranium deposit in Příbram, Czech Republic, the anthraxolite formation is the result of the transformation of organic matter into bitumens in the sediments of the Upper Proterozoic and Lower Cambrian, mobilization and transport of these bitumens by hydrothermal fluids into uranium deposit, and -after incorporation of uraninite particles / fragments -the radiation effect of uranium radionuclides causing the polycondensation of aromatic hydrocarbons in the bituminous mass and a change in its properties.

Origin of Zn-Pb Mineralization of the Vein Bt23C, Bytíz Deposit, Příbram Uranium and Base-Metal Ore District, Czech Republic: Constraints from Occurrence of Immiscible Aqueous–Carbonic Fluids

“…This may be valid especially for CO 2 , because a significant portion of carbon bound in carbonates has a "deep" isotopic signature [2,4] and this work and CO 2 is usually a dominating compound among volatiles derived from lower parts of the Earth's crust [31]. Secondly, some gases (including CO 2 , CH 4 , and N 2 ) could have been produced during the hydrothermal alteration of organic matter contained in sedimentary wall rocks and by radiolysis of hydrocarbons that were migrated together with aqueous fluids and gave rise to anthraxolite-bearing uranium mineralization, whose source is supposed in organic-matter rich horizons of the host Proterozoic sequences [80,81]. Thirdly, considering the participation of fluids from overlying Permian piedmont basins, we can assume that the source of volatiles (including CO 2 , CH 4 , and N 2 ) was due to the maturation of organic matter from coal seams, which occur at the base of sedimentary sequences of the neighbouring Blanice Graben [16,57]; sedimentary basins are in general the fertile sources of fluids with various gaseous compounds [53,82,83].…”