矿床形成深度与深部成矿预测

Depth of ore deposit formation and prognosis of deep-seated ore deposits.

阐述了不同类型内生矿床的成矿深度和金属沉淀的垂直范围。热液成矿作用的深度下限可以下降到10000～12000m。不同类型矿床的成矿深度范围与成矿时的具体地质构造特征有关,且有很大的变化空间。金属矿床的形成深度受成矿母岩岩浆侵位深度的约束,而岩浆侵位的深度又与岩浆中挥发组分的数量、流体释放的时间、成矿元素的矿物/熔体和溶液/熔体分配系数等因素有关。据此可以解释斑岩铜-(钼)、斑岩钼-(铜)和斑岩钨矿床形成深度的差异。地温梯度和多孔岩石的渗透率也与成矿深度有关。CO2等挥发组分的溶解度对压力非常敏感,因此流体包裹体地质压力计对于成矿深度的确定有重要的应用价值。在开展深部成矿预测和找矿时,探寻隐伏岩体顶上带或岩钟是寻找深部与花岗岩有关的多金属矿床的捷径之一。

This paper deals with the depths of mineralization and vertical range of metal precipitation of different endogenic ore deposits. The lower limit of the depth of hydrothermal mineralization may reach 10-12 km below the surface. The depth ranges of different types of deposit are closely related to the characteristics of particular geological structure and magmatism at the time of mineralization, and the ore deposits show a very large variation space. The depth of metal deposit formation is constrained by the depth of emplacement of parent ore magmas, while the depth of magmatic emplacement is in turn related to such factors as the quantity of volatile components in parent magmas, fluid separation time and partitioning coefficients between minerals and melts and between hydrothermal fluids and melts. Thus, we may explain the differences in mineralization depths of porphyry Cu （-Mo） deposits, porphyry Mo （-Cu） deposits and porphyry W deposits. The depths of mineralization are also related to geothermal gradients and permeability of porous rocks. Because the solubility of volatiles such as CO2 is very sensitive to pressures, the use of the fluid inclusion geobarometer can be considered to determine the depth of mineralization. During prognosis and prospecting of deep-seated granite-related polymetallic ore deposits, it is important to look for the top belt or cupola of hidden intrusions.