河南栾川火神庙钼矿床辉钼矿Re-Os同位素年龄及其地质意义

摘要

The Huoshenmiao skarn Mo deposit in the Luanchuan ore district is a medium-sized Mo deposit discovered in recent years. The Mo orebodies are mainly hosted in Huoshenmiao intrusion and Sanchuan marble. In order to determine the age of miner-alization, the source of molybdenum and the relationship with the Nannihu-Sandaozhuang and the Shangfanggou Mo deposits, the authors selected six molybdenum-bearing samples of different ore-forming types for precise dating through ICP-MS molybdenite Re-Os isotopic measurement, and the results yielded model ages ranging from 146.1Ma±2.0Ma to 148.1Ma±2.1Ma, a weighted av-erage age of 147.01Ma±0.95Ma, and an isochron age of 145.7Ma±3.9Ma, implying that the Huoshenmiao Mo deposit was formed in late Jurassic, whereas the Re values of molybdenum vary in the range of 39×10-6~65.4×10-6, indicating that they were derived from mixed crust and mantle sources. The Huoshenmiao and Nannihu-Sandaozhuang as well as Shangfanggou Mo deposits were pro-duced by the second magmatic activity of the late Jurassic in the Luanchuan ore district. The discovery of the Huoshenmiao Mo de-posit provides the basis in the search for mineral resources in the west of the Luanchuan ore district.%火神庙矽卡岩型钼矿床是东秦岭钼矿带栾川矿集区近些年查明的一个中型钼矿床，钼矿体主要赋存于火神庙复式岩体与新元古界蓟县系三川组大理岩接触带的矽卡岩中。为厘定火神庙钼矿床的成矿时代、成矿物质来源及与南泥湖-三道庄、上房沟钼矿床的关系，采用ICP-MS辉钼矿Re-Os同位素定年法对6件辉钼矿样品进行成矿年龄测定，获得的模式年龄为146.1Ma±2.0Ma~148.1Ma±2.1Ma，年龄加权平均值为147.01Ma±0.95Ma，等时线年龄为145.7Ma±3.9Ma，表明火神庙钼矿床形成于晚侏罗世。辉钼矿样品的Re含量为39×10-6~65.4×10-6，显示成矿物质来源于壳幔混源。火神庙钼矿床与南泥湖-三道庄、上房沟钼矿床均为栾川矿集区晚侏罗世第二次岩浆活动的产物，它的发现为在栾川矿集区西部寻找矿产资源提供了依据。