Abstract The sediment-hosted uranium deposit at Four Mile West is buried by 130–150 m of sediments yet has a landscape as well as a surficial geochemical and biogeochemical expression of the mineral system. The landscape expression includes exposure of stratigraphy with now-oxidised redox overprinting (including ‘roll-fronts’) equivalent to those in the buried mineralisation. The landscape also includes morpho-tectonic expressions of faults that have been responsible for the development and preservation of mineralisation. Most importantly, this faulting has produced an embayment in the range front corresponding to a down-faulted area on the plains that has hosted throughflow of surface and groundwater and preservation of underlying, chemically reduced, ore-hosting Mesozoic and Cenozoic sediments. Landscape geochemical and biogeochemical expressions of buried mineralisation are best represented in U2/Th and selected trace elements, rather than simply elevated U contents in isolation. These associations are especially important for distinguishing between the U-rich expressions of buried, sediment-hosted mineralisation and laterally transported U-rich detritus from the adjacent ranges. The surficial geochemical and biogeochemical expression of the underlying mineralised substrate, with higher U2/Th, is best expressed in regolith carbonates, river red gums and potentially ants and macropod droppings. The mechanism proposed for this vertical geochemical transfer is in part tree-root depth penetration (or burrowing in the case of ants) but most importantly upward groundwater flux. Important groundwater fluctuations are connected to low-frequency–high-intensity rainfall periods that drive groundwater recharge and significantly raises the water-table towards the land surface, especially along faults and fractures near the range front and the immediately adjacent plains. During seasons with high rainfall, this groundwater rise may even express itself as water discharge at springs along the range front. Other media, such as stream sediments, soils and inland tea tree are more closely associated with expressing lateral physical dispersion and re-accumulation of U within the landscape. This study shows that surficial mapping, geochemistry and biogeochemistry within a landscape processes/landscape system context can be invaluable for the detection of, and exploration for, buried sediment-hosted uranium mineral systems, and most especially understanding more about the behaviour of chemical elements in the Australian landscape.

中文翻译：

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动物、蔬菜和矿物中的铀：南澳大利亚四英里西部沉积铀矿床的景观地球化学和生物地球化学表达

摘要 位于西四英里的沉积型铀矿床被 130-150 m 的沉积物掩埋，但具有地貌以及矿物系统的地表地球化学和生物地球化学表现。景观表现包括地层暴露与现在氧化的氧化还原叠印（包括“滚动前沿”）等同于埋藏矿化中的那些。景观还包括断层的形态构造表现，这些断层负责矿化的发展和保存。最重要的是，这种断层作用在对应于平原上的下断层区域的山脉前沿产生了一个海湾，该区域承载了地表和地下水的通流，并保存了下伏的、化学还原的、含矿的中生代和新生代沉积物。埋藏矿化的景观地球化学和生物地球化学表达最好用 U2/Th 和选定的微量元素来表示，而不是简单地孤立地提高 U 含量。这些关联对于区分埋藏的沉积物成矿矿化的富 U 表现和来自相邻山脉的横向输送的富 U 碎屑特别重要。具有较高 U2/Th 的下伏矿化基质的表面地球化学和生物地球化学表现在风化岩碳酸盐、河红树胶以及潜在的蚂蚁和巨足动物粪便中表现最佳。这种垂直地球化学转移的机制部分是树根深度渗透（或在蚂蚁的情况下挖洞），但最重要的是向上的地下水通量。重要的地下水波动与低频-高强度降雨期有关，这些降雨期驱动地下水补给并显着提高了地表的地下水位，特别是沿着山脉前沿和紧邻平原附近的断层和裂缝。在降雨量大的季节，这种地下水上升甚至可能表现为山脉前沿泉水的排放。其他介质，如河流沉积物、土壤和内陆茶树，与景观中 U 的横向物理分散和重新积累的表达更密切相关。这项研究表明，景观过程/景观系统背景下的地表测绘、地球化学和生物地球化学对于探测和勘探埋藏沉积物的铀矿物系统非常宝贵，