紫金山铜金矿黄铁矿碎裂结构特征及其地质意义

Characteristics of fragmentation pyrite and its geological implication in Zijinshan Cu-Au Deposit

紫金山铜金矿黄铁矿的碎裂结构具有三种赋存状态,主要运用电子探针(EPMA)对其进行微区分析,进而探讨碎裂结构黄铁矿的特征及其地质意义。通过研究得出以下主要结论:1)本矿碎裂结构黄铁矿的三种赋存状态:破碎程度一般,颗粒较大;破碎程度大,颗粒细小;碎裂结构与粒状结构黄铁矿共生。黄铁矿的破碎程度越大,颗粒越细小,含金性越大,且黄铁矿中金的赋存状态为纳米级颗粒金;2)碎裂结构黄铁矿是亏铁富硫型的,从浅部到深部,亏铁程度与富硫程度逐渐减弱,黄铁矿的Co-Ni图解,说明其是火山—热液成因,其形成与早期隐爆作用有关;3)碎裂结构黄铁矿的主要微量元素有Cu、Co、Ni、Pb、Zn、Au、Ag、As、Sb、Se、W、Sn等,从浅部到深部,碎裂结构黄铁矿的微量元素Sn含量明显增加;元素W、Au、Zn、Ag、Pb都有逐渐降低的趋势;Ni含量也逐渐降低,但是靠近铜矿体,其含量有所增加;越接近铜矿体,Cu与S的含量增加,而Fe的含量降低,体现了紫金山铜金矿床的成矿流体是火山热液(形成于燕山晚期,富含Cu、Au、Pb、Zn等成矿元素)与紫金山复式花岗岩岩体(形成于燕山早期,具有W、Sn、Mo、Bi等矿化特征)的叠加。

Fragmentation structure of pyrites has three kinds of states in Zijinshan Cu-Au deposit,this paper investigated its characteristics and geological implication by the micro area analysis on EPMA.Though the study,we make the following conclusion：1）The three occurrence fragmentation structure pyrites in this deposit：General fragmentation,larger particles;large degree of fragmentation,tiny particles;fragmention pyrite co-occurrence with granular structure pyrite.The larger degree of fragmentation pyrite,the smaller particles,the greater contents of the gold,the occurrence of gold in pyrite is nanoscale particles gold.2）The fractured pyrite is iron-deficiency,sulfur-rich type.The degree of iron-deficiency sulfur-rich gradually weakened from shallow to deep part;The Co-Ni diagram of pyrite show that it is the volcano-hydrothermal origin and relevant to early cryptoexplosion.3）The main trace elements of fragmentation pyrite included Cu、Co、Ni、Pb、Zn、Au、Ag、As、Sb、Se、W、Sn and so on.From shallow to deep part,the content of Sn was increased;the content of W、Au、Zn、Ag and Pb gradually decreased.The content of Ni also decreased,but increased near the copper body.Approaching to copper body,the contents of Cu and S increased,while the content of Fe decreased.It presented that the ore-forming fluid is rich in ore elements such as Cu,Au,Pb,Zn,etc.The volcanic hydrothermal fluid with ore-forming elements superimposed on the early Yanshan Zijinshan composite granite pluton which is mineralized with W,Sn,Mo,Bi,etc.