陕西省铝土矿地质特征及成矿规律

GEOLOGY AND METALLOGENESIS OF BAUXITE IN SHAANXI PROVINCE

陕西省已知铝土矿产地主要分布于陕北的府谷县、渭北的铜川—韩城一带和陕南的西乡、镇巴、南郑地区;已知铝土矿都位于沉积间断面上,受地层层位控制,属滨海—浅海相沉积矿床。陕北和渭北铝土矿主要产于石炭系下统下部本溪组,陕南铝土矿主要产于二叠系上统吴家坪组底部王坡页岩段。成矿的地质构造条件是隆起区边缘。成矿物质来源既有基底碳酸盐岩的溶蚀分解物,也有陆源铝硅酸盐岩的风化分解物。气候条件是有利于使岩石中铝质析出的温暖潮湿条件。时间上有一个较长时间的沉积间断。对成矿有利的地形条件是古地形总体比较平缓,有利于铝硅酸盐风化物在缓慢的搬运过程中充分分解析出Al2O3。

Bauxite resources in Shaanxi province are mainly distributed in Fugu County, northern Shaanxi Province, the districts of Tongchuan-Hancheng in the northern Weihe River, the area of Xixiang, Zhenba and Nanzheng counties in southern Shaanxi province. Bauxite mineralization occurs on the surface of sedimentary intervals, controlled by stratigraphic horizons and belonging to sedimentary deposit of littoral-neritic facies. Bauxite minerals in northern Shaanxi and the north of the Weihe River occur mainly in the Lower Carboniferous Benxi Formation and in southern Shannxi, bauxite mineralization exists mainly in Wangpo shale portion at the bottom Wujiaping Formation of the upper Permian system. The metallo- genic structures are in the margin of uplift and material source of minerals is of dissolution decomposition products from basement carbonate rocks and also from weathered and decomposed materials of terrigenous aluminum-silicate rocks. Warm and humid climate, long-term sedimentary intervals and some gentle paleotopographic landform in this area were favorable for mineralization.