西藏谢通门县斯弄多铅锌矿区矿床地质特征和构造地球化学找矿研究

Study on Geology and Tectono-geochemistry of the Silongduo Lead-Zinc Deposit in Xietongmen County, Tibet

通过矿区现场调查、成矿构造分析,系统总结了矿区构造控矿规律。在此基础上开展构造地球化学找矿研究。区域性东西向挤压构造带是本区重要的控岩控矿构造,其与横向断裂、斜向断裂交汇部位是有利赋矿部位。矿区铅锌矿体产出受地层岩性控制明显,上石炭统昂杰组白云质灰岩及白云岩是有利的赋矿围岩。铅锌矿体与花岗斑岩小岩体关系密切,常位于花岗斑岩体和碳酸盐岩接触面附近。矿区不同岩石Pb、Zn、Mn、As、Sb、Mo、Cu、Bi、Sn含量高,变异系数大,可作为找矿指示元素。元素分布型式显示成矿元素Pb、Zn、Ag、Mn具特征的双峰式分布,表明这些元素卷入了成矿作用。由矿石结构特征和元素组合分析表明,本区铅锌成矿具多阶段性,多期矿化叠加造成矿化富集。原生晕剖面和元素分带研究表明,斯弄多铅锌矿区原生晕分带序列自上而下为(Cr-W-Co-V-Ni)→(Ti-Ba)→(Pb-Ag-Au-As-Sb-Cu-Bi)→(Sr-Zn-Mn-Mo-Sn)。作为前缘晕指示元素As、Sb位于中下部,与主成矿元素重叠,结合矿区控矿构造分析,推测矿区下部可能存在隐伏矿体。

Base on field survey and ore-forming structure analysis for the Silongduo lead-zinc deposit, the structural controls and tectonic geochemical prospecting of the orefield are discussed. The regional EW-trending compressed zones are the major rock- and ore-controlling structures, and their intersections with the transverse and oblique rup- tures are the favorable ore-bearing positions. The occurrence of the lead-zinc ore body was controlled obviously by lithology. The Upper Carboniferous dolomitic limestone and dolomite of the Anjie Group are the favorable host rocks. The lead-zinc ore body is usually located in the contacts between the small granite-porphyry bodies and car- bonate rocks. The concentrations of elements such as Pb, Zn, Mn, As, Sb, Mo, Cu, Bi, Sn in the rocks from the orefield are high with variable coefficients of variation, and thus can be regarded as indicator elements for ore pros- pecting. The distribution patterns of the ore metals, e. g. , Pb, Zn, Ag, Mn, show characteristics of bimodal distri- bution, indicatve of the involvement of mineralization. The texture and the element association of the ores show that the ore-forming processes are of multi-period and multi-stage. The study on the element zonation and primary halo show a downwards zonation of （ Cr-W-Co-V-Ni ）→ （Ti-Ba）→ （ Pb-Ag-Au-As-Sb-Cu-Bi ） → （ Sr-Zn-Mn-Mo-Sn ）. The zonation of elements such as As, Sb are overlying the main ore body. Combining with the analysis of ore-con- trol structure in the orefield, we speculate that there is a concealed ore body at the depth of the mining area.