U/Th-rich bitumen in Archean granites and Palaeoproterozoic metasediments, Rum Jungle Mineral Field, Australia: implications for mineralizing fluids

摘要: Uranium/thorium (U/Th)-rich bitumen has been discovered within both Palaeoproterozoic black pelites and the Archean granitic basement of Rum Jungle Mineral Field, Northern Territory, Australia. Granite-hosted occurs as small (up to 400-µm diameter) discrete individual nodules, which exhibit many morphological similarities those observed in Phanerozoic siliciclastic rocks. Thorium, dominant radioelement, primarily a hydrated Th–Y–Si–P phase. Uranium-rich inclusions are rare, correspond U–Th–Y–Si–P phase, identified coffinite–thorogummite. Metasediment-hosted is more variable morphology, occurring massive (<2 cm width) veins that cross-cut all foliations, nodules or elongate seams 500 µm length), interpreted represent series coalesced nodules. In examples, uranium, radioelement metasediment-hosted bitumen, present Th-poor uraninite, with Y2O3 contents 3.21 wt.%). Raman investigation types indicates it poorly organized carbonaceous matter, not subjected metamorphism. Consequently, post-metamorphic timing for hydrocarbon emplacement can be inferred magmatic origin precluded. Potential source rocks shales Whites Formation 8 wt.% total organic carbon (TOC)) Koolpin (approximately 13 TOC). Post-metamorphic sericitization accompanied by near-complete removal matter. Alteration was possibly catalyst generation. The phase granite-hosted result alteration antecedent monazite. During this alteration, U, LREE P were fractionated removed, while Th, Y Si remained immobile, recombined form Th–Y–Si This pervasive U/Th-rich granites proposed genetic model formation uranium deposits Field unconformity associated on global scale.