湘西北-湘中地区金-锑矿床中—低温流体成矿作用的地球化学成因指示

Geochemical Signals for Ore-forming Process by Mid-Low Temperature Fluid in Au-Sb Deposits in NW-Central Hunan,China

通过对湘西北 -湘中主要金 -锑矿床和有关区域地层的系统地球化学研究 ,揭示了该区元古界基底和古生界盆地中～低温热液系统特征及流体成矿作用的关系 ;介绍了应用微量元素和稳定同位素隐性地球化学标志进行区域古流体示踪的方法和实际应用效果 ;提出了该地区区域性古流体的运动在水平方向上可达盆地规模 ,在垂直范围内可达几公里的认识 .同时 ,从流体成矿作用的角度对区内锡矿山超大型锑矿床的成因进行了探讨 ,提出湘中盆地至少在城步-新化大断裂以东的广大地区 ,可能同属一个受盆地周边燕山期花岗岩体制约 ,并以深循环大气降水来源为主的大型盆地热液系统 .燕山期主要的热流异常中心是成矿的有利部位 .深大断裂及其次级断裂 ,以及不同渗透率的地层通过其不同的隔水、导水和聚水作用 ,对区域流体的运移和汇聚起主导因素 .盆地基底在提供成矿物质和热流来源方面对成矿起了重要作用 。

Systematized geochemical studies on the major Au_Sb deposits and related strata in NW_central Hunan have revealed characteristics of the mid-low temperature hydrothermal systems in the Paleozoic basin and the Proterozoic basement and the related ore_forming process by the geofluid in region. The regional geofluid movement by which the deposits was formed could reach basin_scale horizontally and several kilometer vertically. Cryptic geochemical signals of trace elements and isotopes can well be applied in regional fossil geofluid tracing. On the basis of the above studies, this paper discusses genesis of the Xikuangshan mine, the largest Sb deposit in the world, focuses on the fluid ore_forming process,and has confirmed the opinion that the Central Hunan Basin,or at least its part to the east of the Chengbu_Xinhua Deep Fault,should be a large basin_scale hydrothermal system controlled by the Yansanian granites around basin margin and characterized by gravitational drive of deep_circulated meteoric water. The major centers of the Yansanian geothermic anomaly were favorable for ore deposits. Various interdicting,transmitting or gathering-water faults and strata were key factors to control movement and confluence of the regional geofluid,and the basement played an important role in supplying ore_forming materials and heat flow as well, though it could be possible that a conjectural deep_buried intrusive under local doming contributed a part of heat flow or a fraction of fluid were from deep sources at the early mineralization.