南秦岭桂林沟斑岩型钼矿Re-Os同位素年代学及其构造意义研究  

Molybdenite Re-Os dating and its tectonic significance of the Guilingou porphyry molybdenum deposit,southern Qinling

作　　者：张红[1] 陈丹玲[1] 翟明国[2] 张复新[1] 宫相宽[1] 孙卫东[3,4] 

机构地区：[1]大陆动力学国家重点实验室、西北大学地质系,西安710069 [2]中国科学院矿产资源研究重点实验室、中国科学院地质与地球物理研究所,北京100029 [3]中国科学院矿物学与成矿学重点实验室、中国科学院广州地球化学研究所,广州510640 [4]中国科学院青藏高原地球科学卓越创新中心,北京100101

出　　处：《岩石学报》2015年第7期2023-2037,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41090374;41402064);大陆动力学国家重点实验室自主研发课题;中国博士后基金(BSH13048)联合资助

摘　　要：陕西省镇安县桂林沟斑岩型钼矿床位于南秦岭多金属成矿带内,其成矿围岩主要为细粒花岗岩、钾长花岗岩和蚀变的粗粒花岗岩。本文通过对桂林沟斑岩型钼矿床中辉钼矿Re-Os同位素定年以及围岩中锆石U-Pb年代学研究,旨在探讨成矿成岩的关系及其构造意义。结果表明,6件辉钼矿的Re-Os同位素年龄在195.9~198.5Ma之间,加权平均年龄为197.2±1.3Ma,表明桂林沟钼矿形成于早侏罗世。围岩细粒花岗岩、钾长花岗岩和粗粒花岗岩的锆石U-Pb年龄分别为199±1.4Ma、201±3.1Ma和198±11Ma,这说明其成岩和成矿年龄基本一致。值得注意的的是,桂林沟钼矿床的形成年龄不同于前人已报导的秦岭钼矿的三个主要成矿期,即238~213Ma、145~126Ma和116~110Ma,其稍晚于第一成矿期。200~190Ma可能代表了秦岭成矿带一期尚未认识的重要成矿事件,对于南秦岭找矿具有重要意义。该期钼矿形成于秦岭印支期碰撞之后,是在造山带垮塌引起的岩浆-热液事件过程中形成的。The Guilingou porphyry molybdenum deposit in Zhen＇ an City, Shaanxi Province is located in the southern Qinling polymetallic belts. The wall rocks of the deposit mainly consist of fine-grained granite, K-feldspar granite and altered coarse-grained granite. Molybdenite Re-Os isotopic dating of the ore deposit and zircon U-Pb dating of wall rock were conducted to constrain the relationship between magmatic evolution and mineralization as well as their tectonic significances. The results showed that six molybdenite Re-Os model ages range from 195.9Ma to 198.5Ma, with a weighted average age of 197.2 ＋ 1.3Ma, indicating that the Guilingou porphyry Mo deposit was formed in the Early Jurassic. Meanwhile, zircon U-Pb dating of fine-grained granite, K-feldspar granite and altered coarse-granite yielded ages of 199 ＋ 1.4Ma, 201 ＋ 3.1Ma and 198 ＋ 11Ma, respectively. This suggests that granitic magmatism was almost simultaneous with the mineralization of the Guilingou porphyry molybdenum deposit. Remarkably, the metallogenic age of 200 ~ 190Ma for the Guilingou Mo deposit is different from the reported three main mineralization stages of Qinling molybdenum deposits in literatures, namely 238 ~ 213Ma, 145 - 126Ma and 116 - 110Ma, with being slightly later than the first mineralization stage, displaying an unknown important metallogenic event in the Qinling polymetallic belts. This finding will be of importance in guiding the ore exploration in the southern Qinling. Our results also suggest the Guilingou porphyry molybdenum deposit was probably formed during the magmatic-hydrothermal process induced by orogenic collapse following the Indosinian collision between the South China Block and the North China Block.

关 键 词：桂林沟钼矿 辉钼矿RE-OS定年 锆石U-Pb定年 成矿期 南秦岭 

分 类 号：P597.3[天文地球—地球化学] P618.65[天文地球—地质学]