安徽青阳峙门口层状硫铁矿矿床地质特征及成因研究

青阳峙门口层状硫铁矿矿床赋存于石炭纪地层中,矿体主要呈似层状、透镜状;尽管经历了热变质与接触变质作用,但矿体中仍残留胶黄铁矿和菱铁矿,矿石中不仅可以见到交代残余结构,还可见到草莓结构和微层理构造.黄铁矿中砷的质量分数和S/Se,Co/Ni比值显示火山热水沉积特征.同位素分析显示,矿石中硫化物的硫同位素组成表现出火山热水沉积和热液改造特征;矿石中铅同位素组成则显示,黄铁矿中铅以上地壳铅为主,混有少量地幔铅.上述研究表明峙门口层状硫铁矿矿床是由石炭纪喷流沉积形成的层状矿床或矿胚层,经燕山期岩浆热液和构造作用改造所形成.

STUDY ON GEOLOGICAI CHARACTERISTICS AND GENESIS OF STRATIFIED PYRITIC DEPOSIT IN SHIMENKOU,ANHUI PROVINCE

Bedded pyritic deposit was found in Carboniferous strata at Shimenkou in Qinyang. The ore body was mostly bedded or in lens. Although heat and contact metamorphism were the main geological process in the diggings, there is the residual pyritogelite and sparry iron in this deposit. Not only replacement remnant texture but also strawberry texture and micro-bedding structure are found in the ores. The abundance of As, S/Co and Co/Ni ratio in pyrite indicate the characteristic of volcanic hydrothermal deposit. Isotopic analysis results also indicate that the isotopic composition of sulfide in the ores is consistent with volcanic hydrothermal deposit and hydrothermal alteration and the fractionation of lead isotope in pyrite show that the lead was mainly from upper crust, combined with tiny amount of mantle-derived lead. In our research, the bedded pyritic deposit at Shimenkou was primarily formed as eruptive deposit or protore in Carboniferous period, and later due to the alteration of magmatic water and tectonic process during Yanshan period, the deposit was gradually formed.