西藏邦铺斑岩矿床黑云二长花岗岩的形成时代及地球化学特征  

Geochronology and Geochemistry Characteristics of the Biotite Monzonite in the Bangpu Porphyry Deposit,Tibet

作　　者：赵晓燕[1] 杨竹森[1] 张雄 卢世银[3] ZHAO Xiao-yan;YANG Zhu-sen;ZHANG Xiong;LU Shi-yin(Institute of Mineral Resources, CAGS, Beijing 100037, China;Beijing Institute of Geology for Mineral Resources, Beijing 100012, China;Q inghai Geological Survey Institute, Qinghai 810012, China)

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]北京矿产地质研究院,北京100012 [3]青海省地质调查院,青海810012

出　　处：《矿物岩石地球化学通报》2017年第5期786-796,共11页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：国家重点研发计划课题(2016YFC0600307);中国地质科学院基本科研业务费项目(K1709)

摘　　要：邦铺是继驱龙、甲马之后在冈底斯斑岩铜矿带发现的又一大型斑岩型矿床。为探索邦铺矿区岩浆的起源、建立岩浆演化序列提供依据,本文对位于矿区西南侧的黑云二长花岗岩进行了主、微量元素,锆石U-Pb年代学,Sr-Nd-Pb-Hf同位素分析。结果显示,邦铺黑云二长花岗岩的SiO_2平均含量为73.52%,属钙碱性系列、弱过铝质花岗岩;其轻重稀土分异较明显,负Eu异常强烈,富集K、Rb、Th等大离子亲石元素,相对亏损P、Nb、Ta、Ti等高场强元素;锆石U-Pb年龄为(62.2±0.32)Ma,^(176)Hf/^(177)Hf值分布于0.282892~0.283014,εHf(t)均值为7.3。研究表明,邦铺黑云二长花岗岩起源于俯冲的特提斯洋壳板片脱水引起的地幔楔的部分熔融,地幔组分约占80%,岩浆在上升过程中,有较多地壳物质的加入,并经过了强烈的结晶分异作用。The Bangpu deposit is a large-scale porphyry deposit after Qulong and Jiama in the Gangdese porphyry copper metallogenic belt. Zircon U-Pb dating,whole rock elemental and Sr-Nd-Pb-Hf isotopic compositions of the biotite monzonite have been performed in this study in order to identify the origin of parental magma and constrain magma evolution history. The rocks have average SiO_2 of 73. 52% and are belonging to calc-alkalic and weak peraluminous granite. The rock is enriched in large-ion lithophile elements such as K,Rb,Th and depleted in high field strength elements including P,Nb,Ti. The zircon U-Pb age is（ 62. 24±0. 32） Ma,176 Hf/177 Hf is between 0. 282892 and 0. 283014 and the average εHf（ t）value is 7. 3. The biotite monzonite is originated from the partial melting of the mantle wedge triggered by the subducted Tethyan oceanic slab. The parental magma then experienced extensive fractional crystallization with addition of ~ 20% crustal materials.

关 键 词：亏损地幔 结晶分异 黑云二长花岗岩 邦铺 冈底斯斑岩铜矿带 

分 类 号：P588.121[天文地球—岩石学] P618.41[天文地球—地质学]