因子分析在藏北商旭金矿床地球化学勘查中的应用
Factor analysis in geochemical survey of the Shangxu gold deposit, northern Tibet
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摘要: 提要: 西藏双湖县商旭金矿床位于班公湖—怒江成矿带中部, 矿体受NWW向断裂构造控制, 呈脉状、透镜状产出, 赋矿围岩为木噶岗日群炭质板岩及变质砂岩, 矿石矿物为自然金, 矿石类型主要为石英脉型与绢英岩型, 为一典型的造山型金矿床。在对矿床地质特征、成矿条件分析的基础上, 利用矿区岩屑地球化学数据, 运用因子分析等多元统计方法, 研究矿区地球化学元素组合, 共划分出Cu-Pb-Zn元素组合分区、Au-Ag元素组合分区、As-Sb元素组合分区以及W-Mo-Bi元素组合分区等4个地球化学分区, 绘制了因子得分等值线图, 并在此基础上探讨找矿方向。结合矿区地质特征认为, Au、Ag元素组合和As、Sb组合为商旭金矿床的最佳地球化学标志元素, 下一步地质工作重点应放在Ⅱ1号、Ⅲ1号矿体深部及周围, 同时可布置适当的工程在Ⅲ号矿段西部A预测区, 以追索Ⅲ1系列矿体向西的延伸。Abstract: Abstract: The Shangxu gold deposit, an orogenic gold deposit in the middle part of Bangong Co?Nujiang metallogenic polymetallic belt, is located in Shuanghu County of Tibet. Orebodies occur as veins and lens controlled by the NEE fractures, and the host rocks are carbonaceous slate and metasandstone belonging to the Mugagangri Group; quartz vein type ore and altered rock type ore coexist, with distinctive alteration. Based on an analysis of previous research results of geological features and metallogenic conditions, the authors analyzed the debris samples in the Shangxu gold ore district by using factor analysis method, and drew a geochemical subdivision map and a factor score map. Four geochemical subdivisions were recognized, i.e., Cu?Pb?Zn subdivision, Au?Ag subdivision, As?Sb subdivision, and W?Mo?Bi subdivision. Combined with field geological work, the authors hold that Au?Ag, and As?Sb are the optimum element combinations for prospecting prediction. In future work, orebody Ⅱ1 and orebody Ⅲ1, as well as their surroundings should be regarded as the preferred exploration areas. Meanwhile, predicting area A located in the north of No. Ⅲ ore section is also recommended with the purpose of finding Ⅲ1 type orebodies which extend westward.