The Origin of Uraninite, Bitumen Nodules, and Carbon Seams in Witwatersrand Gold-Uranium-Pyrite Ore Deposits, Based on a Permo-Triassic Analogue

摘要: Permo-Triassic Dongara sandstones from the Perth basin of Western Australia contain solitary bitumen nodules that are analogous to uraniferous (or fly-speck carbon) in Late Archean Witwatersrand gold-uranium-pyrite ore deposits. Nodules both cores radioactive minerals and occupy depositional sites where heavy were concentrated. Solitary Sandstone formed during burial by radiation-induced polymerization liquid hydrocarbons migrating through primary porosity around detrital monazite grains. Similar deposits likewise interpreted have burial, although radiation-emitting grains uraninite. Carbon seams stratiform bodies coalesced nodules. By analogy with nodules, individual carbon as migrated past uraninite grains, but they differ many been stretched perpendicular bedding form an ellipsoidal or columnar structure. Although a structure is consistent deformation vertical extension, clearly postdated nodule formation. In some seams, elongated associated spatially framework-hosted bedding-parallel microfractures, which commonly filled fibrous secondary minerals. Again, microfracturing Columnar-textured fractures be postdiagenetic structural fabrics, whereas appear microfocus compressive deformation. Neither columnar-textured nor present Sandstone, not every seam either, supporting contention focused fabrics postdate formation. Recognition hosted origin supports historical mineralogical observations contained placers. Indeed, most likely former mineral strands. Given chemical instability under oxidizing conditions, strata long-held atmosphere significantly less oxygen than modern atmosphere.