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

doi:10.13278/j.cnki.jjuese.20180297

摘要/Abstract

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。

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

Abstract: 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 mineralization and alteration pattern implies that this area has the porphyry molybdenum deposit potential for the exploration of porphyry molybdenum deposits. The Re content in molybdenite is 0.894×10^-6-2.964×10^-6,indicating that the molybdenum materials come from the crust. Alkaline rocks are dominated during Indosinian,suggesting that the molybdenum mineralization occurred in continental extension tectonics. It is suggested that exploration of molybdenum porphyry should be carried out in Indosinian granitoids.

Key words: Re-Os dating, Indosinian porphyries, Mo-bearing secondary quartzite, Dahu-Qinnan molybdenum deposit, Xiaoqinling

中图分类号:

P618.65

张元厚, 刘金伟, 文斌, 杜尚泽, 屈文俊. 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[J]. 吉林大学学报(地球科学版), 2020, 50(3): 815-824.

Zhang Yuanhou, Liu Jinwei, Wen Bin, Du Shangze, Qu Wenjun. Mineralization Types,Re-Os Dating of Dahu-Qinnan Molybdenum Deposit and Exploration in Xiaoqinling Mt, Central China[J]. Journal of Jilin University(Earth Science Edition), 2020, 50(3): 815-824.

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