西藏冈底斯东段斑岩铜钼铅锌成矿系统的发育时限:帮浦铜多金属矿床辉钼矿Re-Os年龄证据  

Development of Porphyry Copper-Molybdenum-Lead-Zinc Ore-forming System in East Gangdese Belt, Tibet: Evidence from Re-Os Age of Molybdenite in Bangpu Copper Polymetallic Deposit

作　　者：孟祥金[1] 侯增谦[1] 高永丰[2] 黄卫 曲晓明[1] 屈文俊[4] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]石家庄经济学院,河北石家庄510031 [3]西藏地矿局第六地质大队,西藏拉萨851400 [4]中国地质科学院国家地质实验测试中心,北京100037

出　　处：《矿床地质》2003年第3期246-252,共7页Mineral Deposits

基　　金："国家重点基础研究发展规划"项目 (编号 :2 0 0 2CB412 60 0 )资助

摘　　要：通过对西藏冈底斯成矿带东段的帮浦矿床中的辉钼矿进行Re_Os精确测年 ,首次获得北矿带的铜多金属矿化时间。其Re_Os模式年龄为 (14 .30± 0 .2 5 )Ma～ (14 .75± 0 .2 8)Ma ,5件样品得到的187Re_187Os等时线年龄为 (15 .32± 0 .79)Ma。年龄数据与冈底斯成矿带东段南侧斑岩铜矿化带的矿化时间 (14Ma左右 )具有一致性 ,表明北矿带的成矿作用与斑岩有关。斑岩成矿是冈底斯成矿带内的一次主导成矿事件 ,冈底斯南矿带以斑岩型铜钼矿床为主 ,其北矿带以斑岩型铜铅锌多金属矿床为主。冈底斯南、北矿带的成矿作用具有统一的成矿动力学背景 ,发生在碰撞造山带侧向伸展时期 。There are two parallel metallogenic belts lying along the eastern part of the Gangdese Mountains in Tibet, i.e., the porphyry copper mineralization belt in the south and the copper polymetallic mineralization belt in the north. In this paper, the highly precise Re-Os age is given for the first time for molybdenite from the Bangpu copper polymetallic deposit in the north belt. The Re-Os mode ages of 5 molybdenite samples vary from (14.30±0.25) Ma to (14.75±0.28) Ma (error ±2σ). The deposit has yielded a 187Re- 187Os isochron age of (15.32±0.79) Ma, which is identical to the age (14 Ma±) of porphyry copper mineralization in the east Gangdese belt. These data suggest that the copper polymetallic deposits in the north belt are related to the porphyry and that the porphyry metallization must have played a dominant role in metallogenic events in the Gangdese belt. There exist different types of porphyry-related mineral deposits in the Gangdese belt, attributable to the different surroundings into which the metallogenic porphyries intruded. The porphyry copper-molybdenum deposits so far discovered almost unexceptionally occur in the south of the Gangdese metallogenic belt, whereas the porphyry-type copper-lead-zinc deposits are mostly seen in the north of the Gangdese metallogenic belt. The ore-forming processes of the deposits both in the south and in the north of the Gangdese belt took place in the period of east-west extension and shared similar settings of metallogenic dynamics. The copper polymetallic porphyry-related deposits in the Gangdese belt are products of syntectonic-magmatic activity in the Himalayan-Tibetan continent-continent collision orogenic zone.

关 键 词：地球化学 斑岩型矿床 铜多金属矿床 帮浦 冈底斯 西藏 Re—Os年龄 

分 类 号：P597.3[天文地球—地球化学] P618.4[天文地球—地质学]