青海西南三江北段早古新世成岩、成矿事件:陆日格斑岩钼矿LA-ICP-MS锆石U-Pb和辉钼矿Re-Os定年  

Early Paleocene Diagenetic and Metallogenic Events of the Lurige Porphyry Molybdenum-Copper Deposit in Southern Qinghai, China: Evidence from Zircon LA-ICP-MS U-Pb and Molybdenite Re-Os Dating

作　　者：郝金华[1,2] 陈建平[1,2] 董庆吉[2] 王涛[3] 罗志忠[3] 张永涛[3] 

机构地区：[1]地质过程与矿产资源国家重点实验室中国地质大学(北京)科学研究院 [2]中国地质大学北京市国土资源信息开发研究重点实验室 [3]青海省地质调查院

出　　处：《地质学报》2013年第2期227-239,共13页Acta Geologica Sinica

基　　金：地质过程与矿产资源国家重点实验室开放课题基金项目(编号GPMR2011);中央高校基本科研预研项目(编号2-9-2012-21);中国地质调查局地质调查资助项目(编号1212010630804;1212011121215)资助的成果

摘　　要：对青海南部西南三江多金属成矿带北段陆日格斑岩钼矿床开展了锆石LA-ICP-MSU-Pb和辉钼矿Re-Os同位素定年研究。研究表明,陆日格黑云母花岗斑岩、细粒花岗斑岩的锆石LA-ICP-MS206Pb/238U加权平均年龄分别为62.1±0.4Ma、61.7±0.3Ma,所测锆石均显示岩浆成因特点,锆石U-Pb年龄可代表斑岩的结晶年龄;5件辉钼矿的Re-Os加权平均模式年龄为60.7±1.5Ma,锆石U-Pb同位素年龄与辉钼矿的Re-Os年龄非常吻合,所获年龄准确厘定了陆日格矿床的岩浆活动与矿化时限为早古新世。陆日格与三江带中北段主要斑岩型矿床成岩成矿年龄相差近20Ma,表明三江北段自古新世起,区域内至少有两期较大规模的斑岩成矿作用,作为目前已知新生代三江成矿带最早的一次岩浆成矿事件,陆日格斑岩钼矿具有非常重要的理论与找矿工作意义。Zircon LA-ICPMS U-Pb and Molybdenite Re-Os Dating was conducted for the Lurige porphyry Mo-Cu deposit, which is located in the northern portion of Sanjiang polymetallic Ore belt, sourthern Qinghai. The results give two average weighted LA-ICP-MS 206 Pb/238 U ages of 62. 1 ±0. 4Ma and 61. 7 ± 0. 3Ma for biotite granitic porphyry and fine-grained granitic porphyry. All the zircons tested show the characteristics co magmatic origin. The zircon U-Pb isotopic age may represent the crystallization age of porphyry. The 187Re and 187 Os contents of five molybdenite samples from the Lurige deposit determined by ICP-MS show that the Re-Os model age ranges between 59.2～62.8Ma, with an average mean age of 60.7±1.5 Ma. The zircon LA-ICP-MS U-Pb age is in consistent with and molybdenite Re-Os dating, and both may constraint the magmatic activity and mineralization with early Paleocene. Mineralization of the Lurige deposit is about 20 Ma earlier than porphyry deposits in the northern Sanjiang, which indicates that at least two large-scale porphyry mineralization occurred in northern Sanjiang ore belt from Paleocene to oligocene. As the earliest Cenozoic magmatic mineralization in the Sanjiang metallogenic belt, the Lurige porphyry molybdenite-copper deposit is worth further studying .

关 键 词：锆石LA—ICP—MS U—Pb定年 辉钼矿Re—Os定年 斑岩钼矿 陆日格 三江成矿带北段 

分 类 号：P597.3[天文地球—地球化学]