小秦岭地区大湖-秦南钼矿床矿化类型、Re-Os定年及找矿方向  

Mineralization Types,Re-Os Dating of Dahu-Qinnan Molybdenum Deposit and Exploration in Xiaoqinling Mt,Central China

作　　者：张元厚[1] 刘金伟 文斌 杜尚泽 屈文俊[2] Zhang Yuanhou;Liu Jinwei;Wen Bin;Du Shangze;Qu Wenjun(College of Earth Sciences,Jilin University,Changchun 130061,China;National Research Center for Geoanalysis,Beijing100037,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]国家地质实验测试中心,北京100037

出　　处：《吉林大学学报（地球科学版）》2020年第3期815-824,共10页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(41972093)。

摘　　要：小秦岭地区大湖-秦南钼矿床位于华北地台南缘,属于小秦岭-外方山成矿亚带。矿化类型可分为含钼次生石英岩型和细脉浸染型。含钼次生石英岩型矿石构造有角砾状构造、团块状构造、蜂窝状构造、细脉网脉状构造和块状构造;蚀变以细脉浸染状钾化、硅化、碳酸盐化、高岭土化、硬石膏化为特征。细脉浸染型矿化通常与花岗质岩石关系密切,偶尔也见于含钼次生石英脉边部的片麻岩中;蚀变通常为钾化、硅化、绢云母化和少量的黄铁矿化、高岭土化、碳酸盐化等。含钼次生石英岩型含有含钼花岗质岩石角砾。野外证据表明,含钼花岗质岩石向含钼次生石英岩内部表现为,含钼花岗质岩石角砾逐渐变小,并逐渐被含钼次生石英岩包裹,含钼石英脉增厚,高岭土化、硬石膏化增强。这一特征反映了二者之间的成因联系。两种矿化类型中获得的12件辉钼矿Re-Os模式年龄分别为(223.6±4.1)^(196.1±3.0)Ma以及(197.8±3.2)和(196.1±3.3)Ma,Re-Os同位素等时线年龄为(199+14/-25)Ma。这些年龄数据表明,该区的成矿作用发生于印支期或早燕山期。钼矿化时空上与花岗斑岩脉和正长斑岩一致,含钼花岗质岩石的矿化和蚀变样式与斑岩型矿床类似。辉钼矿中w(Re)为0.894×10^-6~2.964×10^-6,反映钼成矿物质来源于地壳。这一时期,区域上以碱性岩岩脉产出为特征,因此本区成矿作用形成于陆内伸展环境下,应注意找寻与印支期花岗质岩石有关的斑岩型钼矿床。Dahu-Qinnan molybdenum deposit in Xiaoqinling is within the Xiong’ershan–Waifangshan metallogenic subzone,which is located at the margin of North China platform.Its mineralization types are divided into Mo-bearing secondary quartzite and vein disseminated associated with granitoid mineralization types.The textures are characterized by breccia,lump,porous,stockwork,and massive.The alterations are dominated by disseminated and stockwork of potassic+sillific+carbonated+argillic+anhydrited.The vein and stockwork with disseminated mineralization is closely associated with the granitoid,occasionally occurs within gneiss nearby the Mo-bearing secondary quartzite.The alterations in vein and stockwork ores are mainly characterized by feldspar+quartz+sericite,with minor pyrite+kaolin+carbonate.The Mo-bearing secondary quartzite ores usually contain granitoid breccia associated with veins.The field evidences show that the Mo-bearing granitoid is disintegrated near its contacted zone to small breccias,and finally disappeared inside of the Mo-bearing secondary quartzite;on the contrary,the Mo-bearing secondary quartzite thickens with the increase of intensive argillic and anhydrite alteration.The results suggest that the Mo-bearing secondary quartzite is derived from the Mo-bearing granitoids.12 samples of molybdenite were taken from the Mo-bearing secondary quartzite and the Mo-bearing granitoids in Dahu-Qinnan molybdenum deposit.The age of Re-Os molybdenite of Dahu-Qinnan molybdenum deposit is(223.6±4.1)Ma to(196.1±3.0)Ma and(197.8±3.2)Ma to(196.1±3.3)Ma.The Re-Os isochron age is(199+14/-25)Ma.This result suggests that the molybdenum mineralization of Dahu-Qinnan deposit took place in Indosinian,or early Yanshanian.The excellent correlation between the Re-Os ages from molybdenite and the ages of granitoids in the area indicate a direct genetic relation between the granitic porphyry and syenite porphyry.The similarity of the Mo-bearing granitoids in Dahu-Qinnan deposit and the classic porphyry deposit in mineralizati

关 键 词：RE-OS定年 印支期斑岩 含钼次生石英岩 大湖-秦南钼矿床 小秦岭 

分 类 号：P618.65[天文地球—矿床学]