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| 西藏南部岗巴—定日地区花岗岩地球化学特征及其构造环境 | |
| 引用本文： | 毛琼,邹光富,顾雪梅,陈岚.西藏南部岗巴—定日地区花岗岩地球化学特征及其构造环境[J].矿物岩石,2012,32(1):67-73. |
| 作者姓名： | 毛琼 邹光富 顾雪梅 陈岚 |
| 作者单位： | 1. 中国矿业大学(北京),北京100081;成都地质矿产研究所,四川成都610082 2. 华北油田第一采油厂,河北任丘,062552 3. 华北油田华达综合服务处,河北任丘,062552 |
| 基金项目： | 国家自然科学基金，1:25×104聂拉木县幅区域地质调查项目 |
| 摘 要： | 通过对出露于西藏南部岗巴—定日地区花岗岩体的地球化学研究表明,岩石中SiO2,Al2O3,Na2O和FeO,MgO等的含量均高,贫CaO和Fe2O3;w(SiO2)介于71.40%～73.06%,A/CNK在1.17～1.34之间,为铝和硅过饱和类型的强过铝质花岗岩。岩石的稀土元素总量(ΣREE)为56.80×10-6～89.12×10-6,(La/Yb)N=6.30～18.26,(La/Sm)N=2.62～3.40,ΣLREE/ΣHREE=2.41～4.66;稀土元素配分曲线呈右倾型,具有弱的负铕异常。Nb,Ti等高场强元素具有明显的亏损,而Rb,U,La,Nd,Hf,Eu,Y等大离子亲石元素具有明显的正异常。岩石的87Sr/86Sr初始比值较高,87Sr/86Sr为(0.738 71～0.751 12)。综合研究认为,本区花岗岩的成因为陆壳部分熔融作用形成的,属陆壳改造型强过铝质花岗岩。本区花岗岩岩浆源区岩石成分主要为砂屑岩,其次为泥质岩,是上地壳部分熔融作用的结果。岩石的微量元素标准化曲线图、岩石地R1-R2图解、Rb-(Yb+Ta)和Rb-(Nb+Yb)图解均显示本区岩体形成于同碰撞构造环境的花岗岩,具有同碰撞岩浆活动的特征,是喜马拉雅早期印度板块与冈底斯板块的俯冲碰撞导致的地壳增厚,上地壳部分熔融的产物;为形成于同碰撞构造环境的花岗岩。 |
| 关 键 词： | 强过铝质花岗岩 地球化学 地壳重熔 构造环境 同碰撞 西藏南部 |
GEOCHEMICAL FEATURES AND TECTONIC SETTING OF GRANITES IN GANGBA-DINGRI AREA OF SOUTHERN TIBET |
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| MAO Qiong , ZOU Guang-fu , GU Xue-mei , CHEN Lan.GEOCHEMICAL FEATURES AND TECTONIC SETTING OF GRANITES IN GANGBA-DINGRI AREA OF SOUTHERN TIBET[J].Journal of Mineralogy and Petrology,2012,32(1):67-73. | |
| Authors: | MAO Qiong ZOU Guang-fu GU Xue-mei CHEN Lan |
| Institution: | 1.China University of Mining and Technology(Beijing),Beijing 100081,China; 2.Chengdu Iinstitute of Geology and Mineral Resources,Chengdu 610082,China; 3.The First Exploit Factory of HuaBei Oilfield Company,Renqiu 062552,China; 4.Huada Comprehensive Services of Huabei Oilfield Company,Renqiu 065002,China) |
| Abstract: | The geochemistry of granite in Gangba-Dingri region of the southern Tibet was analyzed and discussed in the paper.It was showed that the granites were rich in SiO2,（71.40%～73.06%）,Al2O3,Na2O,FeO and MgO and poor in CaO and Fe2O3.A/CN K ratios range from 1.17 to1.34 and saturate with Al and Si,belonging to typical strongly peraluminous granite.The ΣREE=70.80×10-6～134.02×10-6,（La/Yb）N=6.30～18.26,（La/Sm）N=2.62～3.40,ΣLREE/ΣHREE=2.41～4.66.REE diagram shows rightward incline and obvious negative Eu abnormity.High field strength elements such as Nb and Ti show distinct negative anomaly while lithophile elements such as Rb,U,La,Nd,Hf,Eu and Y exhibit obvious positive anomaly.The strongly peraluminous granite has relative high（87Sr/86Sr）ratio of 0.738 71～0.751 12.So,the granite was resulted from partial melt of continental crust in the area.The magma of the granite was mainly originated from clast rocks with minor mudstone.Preliminary mantle-normalized trace element spider diagram,R1-R2 diagram,Rb-（Yb+Ta） and Rb-（Nb+Yb） diagrams indicated that the granite was formed in syn-collision setting.With the features of the syn-collisional magmatic activity,the granite is the product of partially melting crust in such a geologic condition of crustal thickening resulted from the subduction and collision between the Laha massif and India massif during the early Himalayan. |
| Keywords: | strongly peraluminous granites geochemistry crust remelting tectonic setting syn-collision southern Tibet |
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