金川铜镍硫化物矿床Hf同位素地球化学特征与岩浆源区  

Hf Isotope Geochemical Characteristics and Magma Sources in Jinchuan Cu-Ni Sulfide Deposit

作　　者：焦建刚[1,2] 刘欢[1] 段俊[1] 鲁浩[1] 罗德智[1] 祁东[1] 

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]长安大学西部矿产资源与地质工程教育部重点实验室,陕西西安710054

出　　处：《地球科学与环境学报》2014年第1期58-67,共10页Journal of Earth Sciences and Environment

基　　金：国土资源部公益性行业科研专项项目(200911007;201011058);国家自然科学基金项目(41072058);中央高校基本科研业务费专项资金项目(2013G2273009)

摘　　要：金川铜镍硫化物矿床是中国最大镍资源基地,形成于新元古界超镁铁质小岩体中,围岩是古元古界白家嘴子组一套角闪岩相变质岩,矿床的成矿关键因素一直受到广泛关注。详细的地质填图发现岩体与围岩为侵入接触,呈岩席状产出,西南部为岩体顶部,东北部为岩体底部。通过SHRIMP锆石U-Pb年代学及Hf同位素研究,获得矿床中锆石年龄平均为(840±10)Ma,与前人获得的年龄(831.8±0.6)Ma在误差范围内一致,代表成岩年龄的锆石εHf(t)值主要集中在-8.52^-4.85;Hf模式年龄大于锆石U-Pb年龄,表明其岩浆源区受到过地壳物质的混染或来自于富集地幔。Hf-Sr-Nd-Pb-Os同位素研究发现,形成金川铜镍硫化物矿床的岩浆源区属于Ⅰ型富集地幔(EMⅠ),成岩成矿地质背景与陆内裂谷有关,这种特殊的构造环境与地幔源区可能对形成金川超大型铜镍硫化物矿床发挥了重要贡献。Jinchuan Cu-Ni sulfide deposit,which is formed in small Neo-Proterozoic ultra-mafic intrusion,is the largest base of Ni in China.The wall rocks are metamorphic rocks featured by amphibolite facies in Paleoproterozoic Baijiazuizi Formation.The key factors of mineralization are still attracted broad attention.The intruding contact boundary can be found between intrusion and its wall rock by detail geological mapping,Jinchuan intrusion is sill-like,and the top of intrusion is in the southwest and the bottom of intrusion is in the northeast;according to SHRIMP zircon U-Pb geochronology and Hf isotope,the average age of zircon is （840±10）Ma, which is corresponding to the age of （831.8±0.6）Ma measured by formers considering error andεHf （t）values of zircons are concentrated in-8.52--4.85;Hf model age is more than zircon U-Pb age,so that the magma sources have been contaminated by crustal material or from enriched mantle.Hf-Sr-Nd-Pb-Os isotope analysis indicates that the magma sources forming Jinchuan Cu-Ni sulfide deposit belong to Ⅰ-type enriched mantle（EMⅠ）,the petrogenetic and metallogenic setting is connected with continental rift,so that the special tectonic setting and magma sources maybe significantly contribute to the mineralization of Jinchuan super-large scale Cu-Ni sulfide deposit.

关 键 词：铜镍硫化物矿床 岩浆源区 地壳混染 HF同位素 锆石U-PB年龄 原始产状 金川 

分 类 号：P618.41[天文地球—矿床学] P618.63[天文地球—地质学]