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首页> 外文期刊>Economic geology and the bulletin of the Society of Economic Geologists >Mineralogical and Geochemical Evolution of the Unconformity-Related McArthur River Zone 4 Orebody in the Athabasca Basin, Canada: Implications of a Silicified Zone
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Mineralogical and Geochemical Evolution of the Unconformity-Related McArthur River Zone 4 Orebody in the Athabasca Basin, Canada: Implications of a Silicified Zone

机译：加拿大阿萨巴斯卡盆地与不整合面相关的麦克阿瑟河带4矿体的矿物学和地球化学演化：硅化带的意义

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摘要

The McArthur River unconformity-related uranium deposit, located near the southeastern margin of the Proterozoic Athabasca basin in northern Saskatchewan, Canada, contains both basement-hosted and sandstone-hosted orebodies, one of which is the sandstone-hosted Zone 4 orebody and its alteration system. Early pre-ore quartz cementation forming immediately above Zone 4 produced a 200-m-thick silicified zone within the lower Manitou Falls Formation. Late pre-ore oxidizing basinal fluids (δ~(18)O = 1.1-8.9‰, δ~2H = -70 to -34‰) formed zones of dickite, magnesiofoitite, and sudoite-rich alteration in the Manitou Falls Formation above the deposit. These zones were overprinted by an outer halo of illite and illite-chlorite mixed-layer clay that coincided with illite and clinochlore alteration of the Wollaston Group basement rocks. Circulation of basinal fluids into the fault zone, promoted by fault reactivation, created a reducing fluid (δ~(18)O = 3.9-7.8‰, δ~2H= -62 to -25‰) through basement interaction, which formed a narrow sudoite alteration halo near the faulted unconformity. Mixing of these two contrasting fluids initiated uranium mineralization at ca. 1600 Ma. Post-ore alteration caused isotopic resetting of primary uraninite, broadly coincident with the intrusion of the Mackenzie dikes into the basin, followed by alteration of uraninite to coffinite, poorly crystalline uraninite, and gummite during the Neoproterozoic. Cool (ca. 10℃), oxidizing, meteoric waters (δ~(18)O = -15.7 to -13.2‰, δ~2H = -120 to -93‰) later infiltrated fractures, produced post-ore kaolinite, and caused partial oxidation of uraninite to uranophane. The silicified zone at Zone 4 functioned as a physical barrier to fluid flow, creating favorable conditions for uranium mineralization by focusing basinal fluids into the fault zone, localizing reducing basement-modified basinal fluids, and enhancing ore preservation. However, the silicified zone limited the spatial extent of late pre-ore sudoite alteration and obstructed the post-ore mobilization of components such as radiogenic Pb and other pathfinder elements into the overlying strata.
机译：麦克阿瑟河不整合相关的铀矿床位于加拿大萨斯喀彻温省北部元古代阿萨巴斯卡盆地东南缘附近，既有基底托管的砂岩矿体，也有砂岩托管的4区矿体及其蚀变。系统。在4区正上方的早期矿石前石英胶结作用形成了曼尼通瀑布下层下部200米厚的硅化带。矿床上方的Manitou Falls地层中晚期的矿石前氧化性盆地流体（δ〜（18）O = 1.1-8.9‰，δ〜2H = -70至-34‰）形成了地闪石，镁橄榄岩和富辉长岩的蚀变带。存款。这些区域被伊利石和伊利石-绿泥石混合层粘土的外部晕圈覆盖，这与沃拉斯顿集团基底岩石的伊利石和斜绿石蚀变相吻合。断层再活化促进了盆地流体向断层带的循环，通过基底相互作用形成了还原流体（δ〜（18）O = 3.9-7.8‰，δ〜2H = -62至-25‰），形成了狭窄的断裂不整合面附近的苏多石蚀变晕。这两种对比流体的混合使铀矿化开始于大约。 1600毫安矿石后的变化导致原生铀尿石的同位素复位，这与Mackenzie堤防侵入盆地大体一致，随后在新元古代将铀矿改变为有限的结晶性尿素石和软沸石。稍后冷却（约10℃），氧化，流域水（δ〜（18）O = -15.7至-13.2‰，δ〜2H = -120至-93‰），渗透后形成裂缝，形成矿石后的高岭石，并引起尿素部分氧化为尿烷。 4区的硅化带起到了流体流动的物理屏障的作用，通过将盆地流体集中到断层带中，定位还原了地下的改性盆地流体并增强了矿石保存，为铀矿化创造了有利条件。但是，硅化带限制了晚矿石前苏多石蚀变的空间范围，并阻碍了矿石如成矿铅和其他探路元素进入后层的动员。

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