西藏拉抗俄斑岩铜钼矿床辉钼矿Re-Os同位素测年及其地质意义  

Re-Os dating of molybdenite from the Lakange porphyry Cu-Mo deposit in Tibet and its Geological Significance

作　　者：冷秋锋[1] 唐菊兴[2] 郑文宝[2,3] 张金树 唐攀[1] 严刚 董宇 

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037 [3]中国地质大学(北京),北京100083 [4]西藏地质调查院,西藏拉萨850000 [5]西藏第六地质大队,西藏堆龙德庆851400

出　　处：《中国地质》2015年第2期570-584,共15页Geology in China

基　　金：中国地质调查局地质大调查项目(12120114050501,12120113093700);国家自然科学基金项目(41302060);国家973项目(2011CB403103)共同资助

摘　　要：西藏冈底斯成矿带拉抗俄斑岩铜钼矿床位于西藏特提斯构造域拉萨地块东段中南部,是近年来青藏高原地质大调查项目评价的重点矿床之一。本文在钻孔地质编录的基础上,采用辉钼矿Re-Os同位素测年技术,对拉抗俄铜钼矿床中8件产于花岗闪长斑岩中的辉钼矿进行定年,获得了拉抗俄矿床辉钼矿成矿年龄,辉钼矿Re-Os模式年龄为(13.20±0.20)Ma^(13.64±0.21)Ma,加权平均值为(13.38±0.15)Ma,等时线年龄为(13.12±0.44)Ma,代表了拉抗俄斑岩铜钼矿床的成矿时代,成矿作用发生于中新世。辉钼矿中Re的含量为343.6×10-6~835.7×10-6,平均557.8×10-6,指示其成矿物质中有幔源物质加入。拉抗俄斑岩铜钼矿床形成于印度—亚洲大陆碰撞造山带碰撞过程的伸展背景,其成矿年龄与冈底斯斑岩铜矿带东段中亚带众多斑岩-矽卡岩成矿系统年龄基本一致(17~12 Ma),相对于同一矿集区的驱龙、甲玛、邦铺斑岩-矽卡岩型铜多金属矿的成矿年龄小2~3 Ma,但其形成受控于相同的成矿地球动力学背景。The Lakange porphyry Cu-Mo deposit in the Gangdise metallogenic belt of central and southern East Lhasa block within the Tethys tectonic domain is one of the key deposits in the Tibet Plateau geological survey project evaluation in recent years. ReOs isotopic dating technique was applied for determination of mineralization events, and eight molybdenite samples were analyzed for Re-Os isotopic compositions, with the model ages obtained ranging from（13.20±0.20） Ma to（13.64±0.21） Ma, and the isochron age being（13.12 ± 0.44）Ma which represents the metallogenic age of the Lakange porphyry Cu- Mo deposit, indicating Miocene.The Re content of the molybdenite is 343.6 × 10^-6-835.7×10^-6, with an average of 557.8 × 10^-6, suggesting that the metallogenic material originated from a source with mantle components. The Lakange porphyry Cu- Mo deposit was formed in a stretching background of India-Asia continental collision orogenic collision, the age（17-12 Ma） is identical with ages of numerous porphyryskarn mineralization systems in the eastern of Gangdise metallogenic belt, and is 2-3 Ma younger than ages of the porphyry-skarn copper polymetallic deposits in the same ore concentration area, such as Jiama, Qulong and Bangpu, with the formation controlled by the same metallogenic geodynamics setting.

关 键 词：地球化学 RE-OS同位素测年 成矿时代 拉抗俄 冈底斯 西藏 

分 类 号：P597.3[天文地球—地球化学] P618.41[天文地球—地质学] P618.65