冈底斯中段岗讲斑岩铜钼矿床锆石U-Pb和辉钼矿Re-Os年代学及其地质意义  

Zircon U-Pb and Molybdenite Re-Os Dating of the Gangjiang Porphyry Cu-Mo Deposit in Central Gangdese and Its Geological Significance

作　　者：杨震[1] 姜华[2,3] 杨明国[1] 梅红波[1] 胡光道[1] 张黎黎[1,4] 张裴培 

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]昆明理工大学国土资源工程学院,云南昆明650093 [3]云南铜业(集团)有限公司,云南昆明650051 [4]安徽省地质矿产勘查局326地质队,安徽安庆246003 [5]拉萨天利矿业有限公司,西藏拉萨850015

出　　处：《地球科学（中国地质大学学报）》2017年第3期339-356,共18页Earth Science-Journal of China University of Geosciences

基　　金：云南铜业(集团)有限公司和中国地质大学(武汉)合作项目(No.2010026410)

摘　　要：岗讲铜钼矿床是西藏冈底斯成矿带中段典型的斑岩型矿床,岗讲矿床成岩成矿时代、岩浆演化过程及其与成岩成矿关系尚不明确,利用LA-ICP-MS锆石U-Pb定年方法对岗讲矿区主要岩体二长花岗斑岩、花岗闪长斑岩和英云闪长玢岩成岩时代进行研究,获得锆石U-Pb年龄加权平均值分别为16.6±0.3Ma(MSWD=0.94,n=10)、16.1±0.2Ma(MSWD=1.07,n=12)、14.4±0.4Ma(MSWD=1.12,n=7);同时采用辉钼矿Re-Os同位素测年方法首次对岗讲矿床石英硫化物脉中的辉钼矿进行定年,获得12件辉钼矿Re-Os同位素模式年龄集中于13.24±0.20Ma^13.55±0.22Ma,加权平均年龄为13.4±0.1Ma(MSWD=0.65),等时线年龄为13.6±1.6Ma(MSWD=1.2).结果表明:(1)岗讲矿区复式岩体侵入序列为含巨斑黑云二长花岗岩-二长花岗斑岩-花岗闪长斑岩-流纹斑岩(深部定名为英云闪长玢岩),成岩时限为16.6~14.4Ma,成矿时代为13.4Ma左右,成岩成矿是一个连续的岩浆演化过程;(2)辉钼矿中Re含量为155.4~171.1μg/g,均值为162.9μg/g,指示其成矿物质中有幔源成分的加入;(3)矿床产出于中新世印度-亚洲大陆碰撞后伸展构造环境.The Gangjiang Copper-Molybdenum deposit is a typical porphyry deposit, which locates in the Central Gangdese met- allogenic belt. In order to determine the ages of magmatism and mineralization, and disentangle the complicated magmatic evo- lution and the relationship between magmatic process and copper-molybdenum mineralization, the author carried out a study of LA-ICP-MS zircon U-Pb ages of the monzogranite porphyry, granodiorite porphyry, and tonalite porphyrite in Gangjiang min- ing area. It is shown that the zircon U-Pb weighted isochron ages are 16.6±0.3 Ma （MSWD=0.94, n=10）, 16.1±0.2 Ma （ MSWD= 1.07, n = 12）, 14.4± 0.4 Ma （MSWD= 1.12, n = 7 ）. Meanwhile, twelve molybdenite samples separated from quartz sulfides in Gangjiang copper orebodies were used for Re-Os dating, and the model ages obtained range from 13.24±0.20 Ma to 13.55±0.22 Ma, with weighted average 13.4±0.1 Ma （MSWD=0.65） and isochron age 13.6±1.6 Ma （MSWD=1.2）. On the basis of geological studies, and conbined with the results mentioned above and previous research data, it is proposed that the rock mass intrusion sequence is monzogranite porphyry→granodiorite porphyry→tonalite porphyrite→rhyolite porphyry. The porphyry occurred ranges from 16.6 Ma to 14.4 Ma, and the mineralization age of Gangjiang deposit is about 13.4 Ma, and petrogenetic and metallogenic is a continuous process of magmatic evolution. The Re content of the molybdenite is 155.4- 171.1μg/g, with an average of 162.9μg/g, suggesting that the metallogenic material originated from a source with mantle com- ponents. Gangjiang porphyry copper-molybdenum deposit was formed in post-collisional extension setting of India-Asia conti nental collision orogenic belt during the Miocene.

关 键 词：地球化学 锆石U-PB测年 辉钼矿Re-Os测年 斑岩铜钼矿床 冈底斯 

分 类 号：P597[天文地球—地球化学]