内蒙古毕力赫斑岩型金矿成矿岩体地球化学、锆石U-Pb年代学及Hf同位素研究  

Zircon U-Pb age,geochemistry and Hf isotopes of the causative porphyry from the Bilihe porphyry gold deposit,Inner Mongolia

作　　者：朱雪峰 陈衍景[1] 王玭 张成[1] 蔡云龙 邓轲[1] 许强伟 李凯月 ZHU Xuefeng;CHEN Yanjing;WANG Pin;ZHANG Cheng;CAI Yunlong;DENG Ke;XU Qiangwei;LI Kaiyue(MOE Key Laboratory of Orogenic Belts and Crustal Evolution,Peking University,Beijing 100871,China;School of Mining and Coal,Inner Mongolia University of Science and Technology,Buotou 014010,China;Key Laboratory of Ocean and Marginal Sea Geology,Chinese Academy of Sciences;South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,Chin;4.Sonid Jinxi Gold Mining Co.Ltd.,Sonid Youqi 011200,China)

机构地区：[1]北京大学造山带与地壳演化教育部重点实验室,北京100871 [2]内蒙古科技大学矿业与煤炭学院,内蒙古包头014010 [3]中国科学院边缘海与大洋地质重点实验室 [4]中国科学院南海海洋研究所,广东广州510301 [5]苏尼特金曦黄金矿业有限责任公司,内蒙古苏尼特右旗011200

出　　处：《地学前缘》2018年第5期119-134,共16页Earth Science Frontiers

基　　金：国家自然科学基金项目(41602065,41630313,U1139301)

摘　　要：毕力赫金矿位于中亚造山带东南段华北克拉通北缘白乃庙早古生代弧增生杂岩带内,该矿床为一个斑岩型矿床,成矿岩体为早中二叠世花岗闪长岩。文中对成矿岩体进行了主微量元素地球化学以及锆石U-Pb年代学和Lu-Hf同位素研究。毕力赫花岗闪长岩具有安第斯型陆缘弧岩浆岩的地球化学亲缘性:岩体SiO2含量(质量分数)介于61.3%~64.4%,K_2O/Na_2O值介于0.52~0.87,A/CNK值介于0.82~0.95,属准铝高钾钙碱性系列岩石;岩体相对富集Rb、Th、U等大离子亲石元素和轻稀土元素,亏损Nb、Ta、Ti等高场强元素和重稀土元素,显示负Eu异常(δEu=0.50～1.03)。岩体浅部(zk086-53)与深部(zkI005-105)两个样品的锆石206Pb/238 U加权平均年龄分别为(268.1±1.8)Ma(MSWD=1.17,1σ)和(267.7±4.1)Ma(MSWD=1.06,1σ);继承锆石除外,样品中锆石εHf(t)值分别为3.2～8.7和-0.6～8.3,二阶段模式年龄T_(DM2)分别为1 085～737Ma和1 330～762Ma。成矿岩体可能源于洋壳俯冲脱水导致的新生地壳部分熔融而产生的底侵中基性岩浆与由底侵导致的古老基底物质部分熔融形成的长英质岩浆的混合。The Bilihe gold deposit,located in the Bainaimiao arc along the northern margin of the North China Craton（NCC）,is considered a porphyry mineralization system.This study is focused on the LA-ICPMS U-Pb geochronology and Lu-Hf isotopic composition of zircons from the causative granodiorite.The results show that geochemical features,such as peraluminous high-K calc-alkaline characteristics,SiO_2 content（61.3%-64.4%）,ratios of K2O/Na2O（0.52-0.87）and A/CNK（0.82-0.95）,enrichment of LILEs（eg.Rb,U,Th）and LREEs,depletion of HFSEs（eg.Nb,Ta,Ti）and HREEs,and negative Eu anomalies（δEu=0.50-1.03）,indicate the Bilihe granodiorite is similar to typical arc-related granitoids.Also,two granodiorite samples（zk086-53 and zkI005-105）had similar zircon ages and Lu-Hf isotopic characteristics,with weighted mean 206 Pb/238 U ages of 268.1±1.8 Ma（MSWD=1.17,1σ）and 267.7±4.1 Ma（MSWD=1.06,1σ）,respectively,εHf（t）values of 3.2-8.7 and-0.6-8.3,respectively,and TDM2 ages of 1085-737 Ma and 1330-762 Ma,respectively,suggesting that the Bilihe causative granodiorite likely formed during the Early-Middle Permian,from the underplating magma of partially molten juvenile crust mixed with partially molten ancient basement rocks in a continental arc setting.

关 键 词：中亚造山带 索伦缝合带 毕力赫金矿 锆石U-Pb年龄 LU-HF同位素 

分 类 号：P618.51[天文地球—矿床学] P597[天文地球—地质学]