西藏地堡那木岗矿区水系沉积物地球化学特征及找矿预测

GEOCHEMICAL CHARACTERISTICS OF STREAM SEDIMENT AND ORE PROSPECTING OF THE DIBAONAMUGANG OREFIELD IN TIBET

利用SPSS等软件对矿区1∶5万水系沉积物地球化学数据分析,选用平均值±3倍标准差(X±3S)作为上下限反复剔除原始数据的特值,使元素含量服从正态分布.最后以X+2S作为异常下限(T),以1T、2T、4T三级浓度分带,圈定Cu、Au、Ag、Mo单元素异常和Au-Ag-Mo综合元素异常,揭示矿区内水系沉积物地球化学异常特征.将异常区与矿区地质特征、矿床(点)套合分析,表明异常受地层、断裂、围岩蚀变控制,对寻找矿(化)体、断层、围岩蚀变带有指示作用.最终,优选2处远景区,分别为3号综合异常区中心北北西方向至北东向断裂附近,1号、2号综合异常区及其东侧组成一个走向为东西向的异常带.

With the software of SPSS, the geochemistry data from 1 ： 50 000 stream sediment survey in the orefield are analyzed. Adopting the average values plus or minus 3 times of standard deviation as bounds to eliminate the eigenvalues of original data, until the data obey normal distribution. Finally, taking the average values plus 2 times of standard deviation as anomaly thresholds （T）, with IT, 2T and 4T as concentration zonation, to draw element anomaly maps, involving single element anomaly of Cu, Au, Ag and Mo and assemblage anomaly of Au-Ag-Mo. The overlap analysis of ore deposits/occurrence with geological characteristics shows that the anomalies are controlled by strata, faults and wallrock alterations, which are indicators for the searching of orebodies. Eventually, two prospecting areas are selected.