西藏邦铺斑岩钼(铜)矿床钾硅酸盐化热液黑云母电子探针分析及早期成矿流体特征  

EPMA Analysis of Hydrothermal Biotite from the Bangpu Porphyry Mo-Cu Deposit of Tibet,China and the Characteristics of Early Oreforming Fluids

作　　者：王勇[1] 唐菊兴[2] 王立强[2] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院 [2]国土资源部成矿作用和资源评价重点实验室中国地质科学院矿产资源研究所

出　　处：《岩矿测试》2016年第4期440-447,共8页Rock and Mineral Analysis

基　　金：国家自然科学基金资助项目(41403040);中国地质调查局地质调查项目(12120115028301);中央级公益性科研院所基本科研业务费专项(K1416)

摘　　要：热液黑云母的化学组成对于揭示早期成矿流体的物理化学性质和流体演化过程具有重要意义。邦铺矿床是冈底斯成矿带东段一个大型的斑岩型钼(铜)矿床,其钾硅酸盐化蚀变带内热液黑云母广泛发育,本文对采自该矿床闪长玢岩钾硅酸盐化蚀变带内的热液黑云母进行了电子探针分析。结果表明,热液黑云母的SiO_2、TiO_2、Al_2O_3、FeO^T、MgO和K_2O等主要氧化物的平均含量为38.95%、1.42%、13.55%、14.22%、16.23%和9.77%,具有明显的高镁低铁、高钾低钠钙等特征,且异常高的K/Na值(82.5)可能是指示斑岩型钼矿化的重要指标。依据化学组成估算热液黑云母结晶时流体的氧逸度和温度,显示钾硅酸盐化蚀变带内早期成矿流体具有高温、高氧逸度特征,且深部流体平均温度(458℃)明显高于浅部流体(366℃),成矿流体从深部向浅部运移的过程中,温度和压力逐渐降低,导致钼、铜硫化物从流体中析出从而成矿。该成果为进一步研究矿床成矿流体的演化和成矿机制提供了重要线索。The chemical composition of hydrothermal biotite is important in revealing the physiochemical conditions and evolution of early ore-forming fluids. The Bangpu deposit is a large porphyry Mo（ Cu） deposit in the eastern part of the Gangdese metallogenic belt,and hydrothermal biotite is extensive in the potassic alteration zone. Hydrothermal biotite in the potassic alteration zone of dioritic porphyry was analyzed by Electron Microprobe Analyzer（ EPMA） and is reported in this paper. Results show that the biotite is characterized by the high content of K and low contents of Na and Ca. The average contents of SiO2,TiO2,Al2O3,FeOT,MgO,K2O are 38. 95%,1. 42%,13. 55%,14. 22%,16. 23%,9. 77%,respectively. The anomalously high K / Na values（ 82. 5） may be an important indicator for the porphyry Mo mineralization. Based on chemical components,the temperature and oxygen fugacity of the ore-forming fluids were calculated. Results show that the early ore-forming fluids of the potassic alteration have a high temperature and oxygen fugacity,and the average temperature（ 458℃） of the deep ore-forming fluids is much higher than that of the shallow ore-forming fluids（ 366℃）. The decreasing temperature and pressure during the migration of the early ore-forming fluids from deep to shallow resulted in the precipitation of the Mo and Cu sulfides. This research provides an important clue for studying the evolution of ore-forming fluids and the ore-forming mechanism.

关 键 词：热液黑云母 电子探针 物理化学条件 斑岩型矿床 邦铺 

分 类 号：P578.959[天文地球—矿物学] P575.1[天文地球—地质学]