湘西合仁坪钠长石石英脉型金矿床围岩蚀变及质量平衡

摘要

Albite-quartz vein-type gold deposit in Liulincha area of the western Hunan is widespread and poorly constrained.Herenping gold deposit is most typical in the area.In order to reveal the source of ore-forming material,ore-forming process and fluid of the gold deposit,the altered wall-rocks of Herenping gold deposit were studied;mass transfer between the host rock and the ore-forming fluid in the process of wall-rock alteration was calculated by the normalized Isocon diagram method.The results show that wall-rock alteration of Herenping gold deposit mainly includes sericitization (decolorization),pyritization and chloritization,and decolorization is widespread and important for the gold deposit;Al2 O3 in the wall-rock is inert component in the forming process of Herenping gold deposit,and the components including Na2 O,Sr,V,Cr,W, Nb,Th and part volatiles (S,CO2 and H2 O),etc.,are transferred into wall-rock,but the components including SiO2 ,Fe2 O3 ,K2 O,CaO,MgO,Cu,As,Pb,Zn,Ni,Co,Sb,Li,Rb, Ba,etc.,are transfered out;the emigration of light rare earth element is far more than that of high rare earth element,and the differentiation between light and high rare earth elements is strong during wall-rock alteration;Na of albite in ore vein is not derived from ore-host wall-rock, and is mainly transferred into wall-rock by ore-forming fluid;Si of quartz in ore vein is partly derived from ore-host wall-rock.%湘西柳林汊一带钠长石石英脉型金矿十分发育。为了揭示该区金矿的成矿物质来源、成矿过程及成矿流体信息，对该区最典型的合仁坪钠长石石英脉型金矿床围岩蚀变特征进行研究，并利用标准化Isocon图解法，对围岩蚀变过程中物质带入、带出进行质量平衡计算。结果表明：合仁坪金矿床的围岩蚀变主要包括绢云母化(褪色化)、黄铁矿化和绿泥石化，其中褪色化分布最为广泛，是该区金矿床最重要的蚀变类型；在合仁坪金矿床形成过程中，围岩中的 Al2 O3为惰性组分， Na2 O、Sr、V、Cr、W、Nb、Th及部分挥发分(S、CO2和 H2 O)等组分被带入围岩中，而 SiO2、Fe2 O3、K2 O、CaO、MgO、Cu、As、Pb、Zn、Ni、Co、Sb、Li、Rb、Ba等组分从围岩中迁出；轻稀土元素的迁出程度远远大于重稀土元素，围岩蚀变过程中轻、重稀土元素发生强烈的分异；矿脉中钠长石的钠质并非来自赋矿围岩，而是由成矿流体从外界带入的；矿脉石英中硅质则部分来自赋矿围岩。