西藏多不杂铜矿床黄铁矿成分标型特征及地质意义

Typomorphic characteristics of the pyrite composition in the Duobuza copper deposit,Tibet and the geological significance

多不杂铜矿床是近年来在西藏多龙矿集区发现的超大型斑岩铜矿,铜矿石中金的含量较高,黄铁矿是重要的载金矿物之一。研究黄铁矿形态特征、热电性特征、化学成分标型特征等与金矿化具有显著相关性,对于矿石成因类型、成矿物质和流体来源、矿床成因的认识具有重要意义。通过对多不杂铜矿床中黄铁矿的化学成分标型特征研究表明,随着成矿的进行,N(S)/N(Fe)、δFe、δS值逐步变小;w(Co)/w(Ni)值逐步增加,w(Co)值和w(Ni)值逐步减小;w(Se)值逐步增加,w(S)/w(Se)值逐步减小;w(As)值、w(Ag)值以及w(Au)值逐步减小;Cu、Au、Ag呈正相关关系;黄铁矿具有轻稀土相对富集,重稀土相对亏损的特征,这是岩浆热液成因的标志;从岩浆期到热液期,黄铁矿稀土元素表现为正铕异常向负铕异常演化的特征,这是由岩浆向热液演化的依据。

Duobuza Cu deposit is a super-large porphyric Cu deposit discovered in Duolong ore-deposit-clustered area in recent years.Gold content is relatively high in the ore.Pyrite is one of the important gold carriers and its characteristics of morphology,thermoelectricity and composition typomorph are studied.The reesults show that gold mineralization is clearly correlated with the characteristics and they are significant to understand genetic types of the ore,ore material and ore fluid sources and genesis of the Cu deposit.During mineralization value of N(S)/N(Fe)、δFe、δS decrease and value of w(Co)/w(Ni)increase,value of w(Co)and w(Ni)decrease,value of w(Se)increase,value of w(S)/w(Se)decrease,value of w(As),w(Ag)and w(Au)gradually and Cu、Au、Ag are positively correalted and the pyrite is characterized by relatively enrichment of LREE and relatively depletiion of HREE which are the indications of magmatic hydrothermal fluid genesis of the deposit.Evolution of REE composition of the pyrite from positive Eu anomly to negative Eu anomly is the evidence for magma-hydrotherma fluid evolution of the deposit.