西藏冈底斯带花岗岩的时空分布特征及地壳生长演化信息

西藏冈底斯带花岗岩的时空分布特征及地壳生长演化信息

莫宣学1 2, 董国臣2, 赵志丹1 2, 周肃1 2, 王亮亮2, 邱瑞照3, 张风琴2

1. 地质过程与矿产资源国家重点实验室(中国地质大学),北京, 100083; 2. 中国地质大学(北京)地球科学与资源学院,北京, 100083; 3. 中国地质调查局,发展研究中心,北京, 100037

收稿日期:2005-09-20 修回日期:2005-09-20 出版日期:2005-09-20 发布日期:2005-09-20

Spatial and Temporal Distribution and Characteristics of Granitoids in the Gangdese, Tibet and Implication for Crustal Growth and Evolution

MO Xuan-xue1 2, DONG Guo-chen2, ZHAO Zhi-dan1 2, ZHOU Su1 2, WANG Liang-liang2, QIU Rui-zhao3, ZHANG Feng-qin2

1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China; 2. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China; 3. Developing and Research Center, Chinese Geological Survey, Beijing 100037, China

Received:2005-09-20 Revised:2005-09-20 Online:2005-09-20 Published:2005-09-20

摘要/Abstract

摘要： 花岗岩是大陆特有的重要组成部分,同时与矿产资源有密切的关系。西藏花岗岩约占西藏自治区面积的12％,其中,80％分布在冈底斯岩浆岩带。在空间上,冈底斯花岗岩带大致可以分为3个亚带：北带、中带和南带；在时间上,以印度一亚洲大陆碰撞事件为标尺,可将青藏高原构造一岩浆事件划分为碰撞前（〉65Ma）、碰撞期（65～45Ma）、后碰撞（〈45Ma）3大阶段。在这3个阶段中,冈底斯带都产生了具有各自特点的花岗岩构造一岩浆类型。冈底斯花岗岩类的形成演化与新特提斯班公湖一怒江洋及雅鲁藏布洋的形成演化,有密切的关系。因此,其岩石的Nd,Sr同位素资料,对地壳生长与演化有重要的指示意义。冈底斯南带的大部分地区的花岗岩,均具有εNd（t）（＋）值（＋1．64～＋5．21）,模式年龄tDM也很年青（〈500Ma）,具有初生（juvenile）地壳的特征。在花岗岩成因中地幔物质有重要的贡献。而冈底斯中带、北带及南带西段的花岗岩类以εNd（t）（-）值为特征（-5．3～-17．3）,模式年龄tDM有两组值1．2Ga及2．0～2．5Ga,暗示这些地区的地壳具有古元古代一中元古代基底在花岗岩成因中,地壳组分具有主要贡献。

Abstract: Granites are important components in the continents, and also closely related to mineral resources. Granites take c. 12% of the total area of Tibetan territory and about 80% （in area） of them are distributed in the Gangdese magmatic belt. Spatially, the Gangdese granitoid belt consists of three zones, i. e. , north, middle and south zones, as a result of the evolution of Neo-Tethyan Bangong Co-Nujiang ocean and Yarlung Zangbo Ocean. Temporally, the tectono-magmatie events in the Tibetan Plateau and the Gangdese can be divided into three stages： Pre-collisional （〉65 Ma）, syn-collisional （65 -45 Ma） and post-collisional （〈 45Ma）. Nd and Sr isotopes of granitoids in the Gangdese provide a hint for understanding the crust growth and evolution. Most of granites in southern Gangdese have positive values of εNd （t）（＋ 1. 64 - ＋ 5.21 ） and young Nd model ages tDM （〈500 Ma）, showing characteristics of the juvenile crust. It implies that the mantle material played a significant role in granite petrogenesis. Granites in middle and northern Gangdese, however, are characterized by negative εNd（t）（ -5.3 - - 17.3） and relatively older tDM, 1. 2 Ga and 2.0 - 2.5 Ga, implying a Neo- and Paleo-Proterozoic basement. Crustal material played a major role in granite petrogenesis for the latter case.

莫宣学 , 董国臣, 赵志丹 , 周肃 , 王亮亮, 邱瑞照, 张风琴. 西藏冈底斯带花岗岩的时空分布特征及地壳生长演化信息[J]. J4.

MO Xuan-xue1 2, DONG Guo-chen2, ZHAO Zhi-dan1 2, ZHOU Su1 2, WANG Liang-liang2, QIU Rui-zhao3, ZHANG Feng-qin2. Spatial and Temporal Distribution and Characteristics of Granitoids in the Gangdese, Tibet and Implication for Crustal Growth and Evolution[J]. J4.