鄂东南地区鸡笼山矽卡岩金矿床的辉钼矿Re-Os同位素年龄及其构造意义

摘要

鄂东南地区是我国长江中下游Cu-Au-Fe-Mo成矿带中最重要的组成部分之一，其中鸡笼山金矿是是区内典型的大型矽卡岩金矿床。本文利用Re-Os同位素定年方法对鸡笼山金矿床进行了成矿时代测定，获得了辉钼矿的Re-Os同位素模式年龄范围为147．7±2．4～151．6±4．0Ma，等时线年龄为148．6±1．5Ma，与矿区内花岗闪长斑岩SHRIMP锆石U-Pb年龄151．6±0．7Ma相吻合，也与鄂东南地区其他矿田的成矿时代基本一致。鸡笼山矽卡岩金矿床可能形成于岩石圈伸展构造背景。硫同位素值为-2．5‰～5．5‰，均值为2．84‰，具有明显的塔式效应，反映了成矿物质具有岩浆来源的特征；辉钼矿中 Re 含量为174．3×10-6～871．4×10-6，平均为476．2×10-6，表明成矿物质来源属于壳幔混源型。%Southeast Hubei Province is one of the most important part of the Cu-Au-Fe-Mo metallogenic belt in the middle-lower Yangtze River in China,the Jilongshan Au deposit is a large skarn gold deposit in this area.This paper use Re-Os isotope dating method for the determination of timing of the Jilongshan gold deposit.The molybdenite Re-Os isotopic model age range from 147. 7 ±2. 4 to 151. 6 ±4. 02Ma with an isochron age of 148. 6±1. 5Ma,which is alomost similar to zircon SHRIMP U-Pb age of 151. 6±0. 7Ma of granodiorite porphyry in the Jilongshan Au skarn deposit.These data are alos consistent with skarn Cu-Fe mineralization age in Southeast Hubei.The Jilongshan skarn Au deposits may be formed in lithosphere extension tectonic setting.Sulfur isotope values are -2. 5‰~5. 5‰ with an mean value of 2. 84‰, eflecting that the characteristics ore-forming material originated from magmatic origin.The content of Re in molybdenite is 174. 3 ×10-6~8714 ×10-6 ,with an average value of 476. 2 ×10-6 ,indicating that the sources of ore-forming are deried from a mixture of crust and mantle material.