The Bigrlyi deposit is a tabular, sandstone-hosted, uranium–vanadium deposit of Carboniferous age located in the Ngalia Basin of central Australia. The deposit is similar to the continental, fluvial Saltwash-type of sandstone-hosted U-V deposits which are well known from the Colorado Plateau, USA. Most mineralization at Bigrlyi occurs as thin, multiple-stacked, stratiform lenses at the base of fluvial channels near the contact between a grey sandstone succession and a hematitic, purple–red sandstone succession. A larger halo of lower grade vanadium mineralization extends beyond the main U-V-mineralized zone. The host is an immature, feldspathic sandstone, grading into arkose and lithic-rich variants. Lithic ‘rip-up’ clasts of clay-rich sediments are common in the basal parts of fluvial channels, and are frequently the focus of, and have acted as sites for, U-V mineralization. Coffinite and uraninite are the main uranium minerals, with the former dominant. Vanadium is mainly hosted by Fe-V-bearing clays and chlorite, including roscoelite, grading into vanadian illite, the interlayer mineral corrensite, and altered detrital biotite. The V-Fe–oxyhydroxide minerals montroseite, haggite and doloresite, and altered detrital Fe-Ti oxides, are minor V-hosts. Mineralized zones correlate with enrichments in Se, Li, Ba, Be, Mo, Mg and Fe, and elevated Se/S ratios are characteristic of U-mineralized zones. Petrographic studies show that a heterogeneous mixture of variably mineralized lithic clasts is present; in the same rock, some clasts are Fe-rich and only weakly U-V-mineralized, while other clasts are strongly V- and/or U-mineralized. These observations point to mineralization processes that did not take place in-situ in the host sandstone at the site of deposition as required by conventional groundwater models. Lead isotope results provide evidence of the open-system mobility of radiogenic elements in parts of the deposit. In V-bearing zones, radiogenic Pb contents were found to be unsupported by current U levels, suggesting that over time U has been mobilized from these zones and redistributed, resulting in U-enrichment in other parts of the deposit. Mobility pathways were likely open over time from early in the history of the Bigrlyi deposit. A hybrid mineralization model, involving an interplay between solution-precipitation processes, detrital transport and post-depositional U remobilization, is proposed for Bigrlyi. Ferrous-ion-bearing clay minerals and pyrite are considered to be the most likely primary reductants/adsorbents, while the deposit is lacking carbonaceous matter.

中文翻译：

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澳大利亚中部Ngalia盆地Bigrlyi板状砂岩型铀钒矿床

Bigrlyi矿床是位于澳大利亚中部Ngalia盆地的一种由石炭纪组成的板状砂岩型铀钒钒矿床。该矿床类似于美国科罗拉多高原众所周知的大陆性，河流盐溶型的砂岩型紫外线矿床。Bigrlyi的大多数矿化作用是在灰色砂岩演替与紫红色，紫红色砂岩演替之间接触的河道底部薄，多叠层状晶状体发生的。较低品位钒矿化的较大晕圈延伸到主要的UV矿化区之外。主体是不成熟的长石砂岩，分为方糖和富含石质的变体。富含粘土的沉积物的岩屑“剥落”碎屑在河流通道的基部很常见，并且经常成为人们关注的焦点，并已成为UV矿化的场所。Coffinite和uraniteite是主要的铀矿物，前者占主导地位。钒主要由含Fe-V的粘土和绿泥石（包括硅锰铁矿）组成，可分为钒伊利石，夹层矿物堇青石和碎屑黑云母。V-Fe-羟基氢氧化物矿物是蒙脱石，钙铁矿和白云母，以及已改变的碎屑Fe-Ti氧化物，都是次要的V元素。矿化带与硒，锂，钡，铍，钼，镁和铁的富集相关，硒/硫比升高是U-矿化带的特征。岩石学研究表明存在不均匀矿化的碎屑岩屑的非均质混合物。在同一块岩石中，某些碎屑富含铁，仅弱紫外线矿化，而其他碎屑则具有强烈的V和/或U矿化。这些观察结果表明矿化过程不是常规地下水模型所要求的，而是在沉积地点的宿主砂岩中原位发生的。铅同位素结果提供了矿床部分放射源元素在开放系统中活动的证据。在含V区，发现放射性铀的铅含量不受当前铀水平的支持，这表明随着时间的流逝，铀已经从这些区中迁移出来并重新分布，导致铀在矿床的其他部分富集。从Bigrlyi矿床历史的早期开始，随着时间的流逝，流动路径就可能开放。针对Bigrlyi，提出了一种混合矿化模型，该模型涉及溶液沉淀过程，碎屑运移和沉积后U迁移之间的相互作用。