西藏冈底斯东段叶巴组火山岩地球化学特征及其地质构造意义  

Geochemistry and Tectonic Setting of Lavas in the Yeba Formation in the Eastern Part of the Gangdise Belt

作　　者：曾忠诚[1] 刘德民[1] 泽仁扎西 尼玛次仁 

机构地区：[1]中国地质大学地球科学学院,武汉430074 [2]西藏地质矿产勘查开发局地质二队,拉萨851400

出　　处：《吉林大学学报（地球科学版）》2009年第3期435-445,共11页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(40572113);中国地质大学(武汉)优秀青年教师资助计划项目(CUGQL0612);国家“973”计划项目前期研究专项(2005CCA05600);中国地质调查局矿调项目([2006]1-8)

摘　　要：西藏冈底斯东段叶巴组火山岩的岩石地球化学特征研究表明:该火山岩为一套岩性连续分布的钙碱性火山岩,其中基性火山岩主要来源于岩石圈地幔的部分熔融,并受到流体的交代作用,中酸性火山岩则主要来源于地壳的部分熔融。叶巴组火山岩形成于岛弧或活动大陆边缘的构造环境,其动力来源应为新特提斯洋向北的俯冲消减。叶巴组发育的岛弧地区是形成具重要经济价值的VMS矿床的最佳地域。叶巴组火山岩的研究对早、中侏罗世的生物事件、气候变化以及海退或海侵事件也有重要的意义。The geochemical characteristics of the lavas in the Yeba Formation in the eastern Gangdise tectonic belt in Tibet show that they are calc-alkali volcanic rocks. The basic volcanic rocks are believed to be originated from partial melting of the mantle that might have undergone fluid metasomatism, and the intermediate-acidic volcanic rocks to be formed by partial melting of the crust. The lavas in the Yeba Formation were formed in an island arc or an active continental margin tectonic environment. It is concluded that northward subduction of the Neo-Tethys resulted in the magmatic eruption of the Yeba Formation in the Early-Middle Jurassic time. The island arc area where the Yeba Formation developed is suggested to be also the most favorable area for important VMS deposits. Meantime, it is proposed that the studies on the lavas in the Yeba Formation are also meaningful to understand the Early Jurassic biotic crisis, climate change, and regression or transgression events.

关 键 词：西藏冈底斯带 叶巴组火山岩 地球化学特征 大地构造环境 

分 类 号：P588.14[天文地球—岩石学]