西藏冈底斯多金属成矿带铅锌矿定位预测与资源潜力评价

Regional metallogenic predication and mineral reserves evaluation of lead and zinc deposits in the Gangdise polymetallic ore-forming belt,Tibet

矽卡岩型和热液脉型铅锌多金属矿是冈底斯地区铅锌资源量的主要来源。本文在全面收集冈底斯成矿带及其周边(主要包括冈底斯及其以南的喜马拉雅带)地质、矿产、物探、化探、遥感等基础地质资料的基础上,建立了GIS平台基础上的资源预测评价系统。运用特征分析模型和数理统计方法,分别确定了预测区内矽卡岩型和热液脉型铅锌多金属矿定位预测的找矿模型和定量化标志,其中对铅锌矿预测比较重要的地质变量(变量权重>0.2)有中酸性花岗质侵入岩体,其他类型矿床(点),Cu、Pb、Zn、Ag、Cd、Au、Bi单元素化探异常,Cu-Pb-Zn-Ag、Pb-Zn、Pb-Zn-Ag-Cd组合化探异常,磁异常正负场变化,中低负重力异常场等。在此基础上,利用MRAS资源评价系统,圈定了铅锌矿成矿远景区共57处,总体上预测成果与实际地质情况及已知矿床(点)分布吻合较好。采用面金属量法估算了各远景区的铅锌矿资源量。统计结果表明,预测区内1000m以浅潜在铅锌资源总量可达2.9亿吨,指示了冈底斯成矿带及其周边仍具有良好的铅锌矿找矿远景和资源潜力。

Skarn and hydrothermal vein deposits constitute the main resources of lead and zinc in the Gangdise metallogenic belt. In recent years, especially since the beginning of the Geological Survey Project in 1999, great progress in geological survey and resource exploration has been made, several large-size lead and zinc ore deposits have been discovered, and many important regional geological data have been accumulated in Gangdise region. Based on detailed collection of geological, ore deposits, minerals, geophysical and geochemical data and remotesensing information in this region, the authors established a mineral resources evaluation system based on GIStechnology. The basic data of the mineral resources evaluation system cover a wide range of information, which includes geology （stratigraphy, tectonics, magmatic rocks and metamorphic rocks）, minerals （ore deposits and mineralized spots）, geophysical data （magnetic and gravitational method）, geochemical data （individual and composite Cu, Pb, Zn, Ag, Cd and Au geochemical anomalies） and geography. Using characteristic analysis model and mathematical statistics, the authors determined the metallogenic model and quantitative geological variables for prognosis of skarn and hydrothermal veinlike lead and zinc deposits respectively, which constitute the dominant lead and zinc ore types in the Gangdise metallogenic belt. The result has shown that the most im- portant geological factors for the prognosis of lead and zinc deposits include intermediate-acid granitic intrusive bodies, known ore deposits and mineralized spots, individual Cu, Pb, Zn, Ag, Cd, Au, Bi geochemical anomalies, composite Cu-Pb-Zn-Ag, Pb-Zn, Pb-Zn-Ag-Cd geochemical anomalies, positive-negative change of magnetic anomalies, and middle-low negative gravity anomalies. According to the calculation of the MRAS system （de- veloped by Institute of Mineral Resources, CAGS）, 57 target areas for skarn and hydrothermal vein lead and zinc deposits were delineated in the Gangdise metallogenic belt. The results obtained by statistics are in well accord with the geological deduction. The lead and zinc reserves were estimated by the areal productivity method, which shows that there still exists great potential for lead and zinc deposits in Gangdise region, and that the predicated lead and zinc reserves within the depth of 1 000 m are over 290 million tons. The most potential lead and zinc target areas mainly include Yaguirang-Sharang-Dongzhongsongduo, Bangpu-Songduoxiong-Xiamari- Nongruri, Zexue lead and zinc deposits, Bengbunong gold deposit, Mengyaa-Longmala etc., in which the potential lead and zinc reserves are over 20 million tons.