西藏多不杂斑岩铜矿床辉钼矿Re-Os和锆石U-Pb SHRIMP测年及地质意义  

Molybdenite Re-Os and SHRIMP zircon U-Pb dating of Duobuza porphyry copper deposit in Tibet and its geological implications

作　　者：佘宏全[1] 李进文[1] 马东方[2] 李光明[2] 张德全[1] 丰成友[1] 屈文俊[3] 潘桂棠[2] 

机构地区：[1]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 [2]中国地质调查局成都地质矿产研究所,四川成都610082 [3]国家地质实验测试中心,北京100037

出　　处：《矿床地质》2009年第6期737-746,共10页Mineral Deposits

基　　金："十一五"国家科技支撑计划项目(2006BAB01A10);973基础研究项目(2002CB412609)的资助

摘　　要：多不杂矿床是班公湖-怒江缝合带上发现的第一处大型斑岩铜矿床。该矿床位于班公湖-怒江缝合带的北侧,羌塘地块的南缘。含矿斑岩体属花岗闪长斑岩,其SiO2含量为61.37%～67.73%,平均为65.16%;稀土元素总量为(41.4～94)×10-6,LREE>HREE,属轻稀土元素富集型;微量元素特征表现为富集大离子不相容元素Rb、K、Th、Ba、La、Ce、Sr,亏损高场强元素Nb、Ta、P、Ti。含矿斑岩的稀土元素和微量元素特点反映出岛弧带的岩浆作用特征。含矿斑岩中锆石的U-PbSHRIMP测年获得(120.9±2.4)Ma(MSWD=4.3)谐和年龄,代表了含矿斑岩的形成时代。6个辉钼矿样品的Re-Os模式年龄范围非常一致,其变化范围为(117.6±1.3)～(118.5±1.4)Ma,等时线年龄为(118.0±1.5)Ma(MSWD=0.30),代表了该矿床的成矿年龄。该矿床的形成时代对应于班公湖-怒江早白垩世期间的多岛弧-盆系演化时期,其形成环境类似于东南亚的多岛弧-盆系统。The Duobuza porphyry copper deposit, the first large-size porphyry copper deposit discovered along the Bangong-Nujiang suture zone, is situated in the Duobuza tectonic-magmatic zone on the southern margin of the Qiangtang-Sanjiang massif. The main mineralized porphyry in the ore deposit is a granodiorite porphyry, whose SiO2 content varies from 61.37% to 67.73%, 65.16% on the average. Its REE content is （41.4-94）×10-6, and the LREE content is higher than the HREE content, suggesting the enrichment of LREE. As for trace elements, the porphyry shows enrichment of Rb, K, Th, Ba, La, Ce, Sr and depletion of Nb, Ta, P, Ti. The major, rare earth and trace elements of the mineralized porphyry have characteristics of volcanic rocks formed in the island arc. The zircon SHRIMP dating （14 samples ） of Duobuza granodiorite porphyry gave 206Pb/238U concordant ages from （116.5± 4.6） Ma to （125.3±4.7） Ma, with a weighted mean age of （120.9±2.4） Ma, which indicates the age of the copper-mineralized porphyry rock. Meanwhile, the 187Re and 187Os content of molybdenite from the ore deposit was de termined by Inductive ly Coupled Plasma Mass Sperctrometry （ICP-MS）, and the results show that the Re-Os model ages of the deposit are from （117.6±1.3） to （118.5±1.4） Ma, and its isochron age （118.0±1.5） Ma, which have accurately determined the ti ming of mineralization.The age of the ore deposit is consistent with the evolution of the Bange-Nujiang archipelagic arc-basin system in Early Cretaceous, implying that the Duobuza c opper deposit was formed in an archipelagic are basin system similar to the syst em of southeast Asia.

关 键 词：地质学 岩石地球化学 同位素年代学 成矿时代 斑岩铜矿床 多不杂 西藏 

分 类 号：P618.41[天文地球—矿床学]