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板伏砂岩型铀矿床构成了美国最大的铀矿资源类型。地下水流的性质和方向一直是有关该类矿床最主要的争论点。本文给出了圣胡安盆地上侏罗统莫里森组Westwater谷段和Jackpile砂岩段铀成矿期区域地下水流的定量模拟。从1 600个钻孔、100个实测剖面和古地形再造的资料中得到了每一岩层的厚度和砂、泥比,从而给出了4层岩层有限差分模式的输入项。地形斜坡、湖滨线的位置及湖水和孔隙流体的密度差控制了地下水流的方向和补给排泄区。对于铀矿床形成来说,最重要的结论就是区域地下水流通过盆地排泄。排泄区主要沿湖滨线或干盐湖的边缘分布,绝大多数水流受重力驱功。
Plateau volcanic sandstone-type uranium deposits constitute the largest type of uranium resources in the United States. The nature and direction of the groundwater flow has always been the main argument for this type of deposit. This paper presents a quantitative simulation of the groundwater flow in the West Jurassic Formation and the Jackpile sandstone section of the Upper Jurassic Morrison Formation during uranium mineralization. The thickness, sand and mud ratio of each rock formation are obtained from the data of 1,600 boreholes, 100 measured sections and palaeo-terrain reconstruction, thus giving the input of the finite difference model of 4 layers. The slope of the terrain, the location of the lakeside line, and the density difference between the lake and pore fluids control the direction of the groundwater flow and the recharge and discharge area. For the formation of uranium deposits, the most important conclusion is that regional groundwater flow through the basin excretion. The drainage area is mainly distributed along the edge of the lake coastline or dry salt lake, and most of the water current is driven by gravity.