西藏当雄地区拉屋矿床二长花岗岩地球化学特征及构造背景  

Geochemical signatures and tectonic setting of monzogranites in the Lawu ore deposit,Damxung,Xizang

作　　者：兰双双[1] 李光明[2] 马东方[2] 董磊[2] LAN Shuang-shuang LI Guang-ming MA Dong-fang DONG Lei(Sichuan Institute of Metallurgical Geology and Exploration, Chengdu 610051, Sichuan , China Chengdu Center, China Geological Survey, Chengdu 610081, Sichuan, China)

机构地区：[1]四川省冶金地质勘查院,四川成都610051 [2]中国地质调查局成都地质调查中心,四川成都610081

出　　处：《沉积与特提斯地质》2016年第3期1-7,共7页Sedimentary Geology and Tethyan Geology

基　　金：国家重点基础发展计划课题(2011CB403106);中国地质调查局青藏专项(1212010918033)联合资助

摘　　要：西藏拉屋矿床位于冈底斯铜铅锌多金属成矿带东段。通过对拉屋矿区出露的二长花岗岩地球化学研究表明,岩石中SiO_2、Al_2O_3和CaO等的含量均高、贫Fe和低Na_2O;w(SiO_2)含量为65.40%~74.43%,A/CNK值在1.41~2.20之间,为强过铝质花岗岩。岩石稀土总量ΣREE(不含Y)较低,为(5.08~80.38)×10^(-6),LaN/YbN值为2.43~5.65,ΣLREE/ΣHREE为1.63~3.64,稀土元素配分型式为右倾型,具负铕异常。Nb、Ti、Zr、Ce等高场强元素和Ba明显的亏损,K、Rb、Sr等大离子亲石元素明显的富集。综合研究认为,本区花岗岩的物质来源于上部陆壳,岩浆源区岩石成分为泥质岩;该岩体为形成于同碰撞构造环境、地壳加厚阶段的过铝质花岗岩。The Lawu ore deposit is located in the eastern part of the Gangdise Cu-Pb-Zn polymetallic metallogenic belt in Damxung,Xizang. The geochemical signatures have revealed that the monzogranites outcropped in the Lawu ore deposit are rich in SiO2（65. 40% - 74. 43% ）,Al2 O3 and CaO,and poor in Fe and Na2 O. The A/ CNK ratios range between 1. 41 and 2. 20,suggesting the highly peraluminous granites. The ΣREE values vary between 5. 08x10-6 and 80. 38 ＆#237; 10-6 . The LaN / YbN ratios range between 2. 43 and 5. 65. The ΣLREE / ΣHREE ratios range from 1. 63 to 3. 64. The REE distribution patterns display the right-leaning curves,and negative Eu anomalies. The high field strength elements such as Nb,Ti,Zr and Ce as well as Ba are markedly depleted while the large ion lithophile elements such as K,Rb and Sr are markedly enriched. It follows that the monzogranites in the Lawu ore deposit were derived from the upper crust,and the source rocks are represented by mudstones. The peraluminous granites cited above are interpreted to be formed in the syn-collisional tectonic settings during crustal thickening.

关 键 词：过铝质花岗岩 地球化学 构造环境 拉屋 西藏 

分 类 号：P588.12[天文地球—岩石学]