西藏冈底斯成矿带南缘新特提斯洋俯冲期成矿作用：来自雄村矿集区Ⅰ号矿体的Re-Os同位素年龄证据  

Neo-Tethys Mineralization on the Southern Margin of the Gangdise Metallogenic Belt,Tibet,China:Evidence from Re-Os Ages of Xiongcun Orebody No.Ⅰ

作　　者：郎兴海[1,2] 唐菊兴[3] 陈毓川[3] 李志军[1] 黄勇[1,2] 王成辉[3] 陈渊 张丽[4] 周云[1] 

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]西藏天圆矿业资源开发有限公司,西藏日喀则857000 [3]中国地质科学院矿产资源研究所,北京100037 [4]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《地球科学（中国地质大学学报）》2012年第3期515-525,共11页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金(No.41172077);国家“973”项目(No.2011CB403103);天圆公司项目(No.2006G-07)

摘　　要：雄村矿集区是近年来西藏冈底斯成矿带内发现的一处超大型铜金矿集区,该矿集区位于冈底斯造山带中段南缘,其南侧紧邻日喀则弧前盆地.最新的勘探资料表明,雄村矿集区由I、II、III号斑岩型铜金矿体组成.本文以雄村I号矿体为研究对象,获得I号矿体中4件辉钼矿样品的Re-Os模式年龄范围非常一致,其变化范围为160.1±2.3～163.4±2.3Ma,等时线年龄为161±11Ma(MSWD=4.2),误差较大,而平均模式年龄161.5±2.7Ma(MSWD=2.0),误差较小.因此,雄村I号矿体的形成时代为160.1±2.3～163.4±2.3Ma,最有可能的形成年龄应为161.5±2.7Ma,该年龄代表了雄村I号矿体的成矿年龄,这与前人获得的含矿斑岩(含眼球状石英斑晶的角闪石英闪长玢岩)的锆石U-Pb年龄(164.3±1.9Ma)基本吻合,表明矿床形成于中侏罗世.同时,雄村I号矿体的含矿斑岩体和赋矿火山岩具有与岛弧火成岩类似的地球化学特征,如相对富集LREE、LILE,亏损HREE、HFS,缺少或微弱负Eu异常.综合来看,雄村I号矿体形成于新特提斯洋俯冲期(>65Ma),产出的构造背景为新特提斯洋向北俯冲形成的岛弧环境,属岛弧型斑岩铜金矿床.Xiongcun metallogenic district,one of the large-size metallogenic areas discovered along Gangdise metallogenic belt,is located in the middle of the southern margin of Gangdise orogenic belt.Its south margin is Shigatse forearc basin.The latest exploration data indicate that Xiongcun metallogenic district is composed of No.I,II and III porphyry copper-gold orebodies.In this paper,Xiongcun orebody No.I is taken as the research subject.The Re-Os model ages of molybdenit（4 samples） from Xiongcun orebody No.I are similar,ranging from 160.1±2.3 Ma to 163.4±2.3 Ma;its isochron age is 161±11 Ma（MSWD=4.2） and error is big;its weight average age is 161.5±2.7 Ma（MSWD=2.0） and error is small.So ore forming age of Xiongcun orebody No.I is（160.1±2.3）-（163.4±2.3） Ma and the most probability is 161.5±2.7 Ma.This age is similar to zircon U-Pb age（164.3±1.9 Ma） of mineralization porphyry（hornblende quartz diorite porphyry with big quartz eyes）,so the ore forming age of Xiongcun orebody No.I is Middle Jurassic.In addition,mineralized porphyry and tuff show geochemical characteristics similar to those of volcanic rocks in an arc or active continental margin,such as relative enrichment of LREE and LILE,depletion of HFEE,HFS and Eu anomalies.We conclude that northward subduction of Neo-Tethys resulted in mineralization of the Xiongcun orebody No.I in the Middle Jurassic;the tectonic setting is the island-arc environment.The deposit type of Xiongcun orebody No.I is island arc type porphyry copper-gold deposit.

关 键 词：Re-Os年代学 辉钼矿 斑岩 成矿作用 西藏 新特提斯洋 

分 类 号：P597[天文地球—地球化学]