西藏改则地区拉果错蛇绿岩地球化学特征及成因  

Geochemistry and genesis of Lhaguo Tso ophiolite in south of Gerze area, Center Tibet

作　　者：王保弟[1] 许继峰[1] 曾庆高 康志强[1] 陈建林[1] 董彦辉[1] 

机构地区：[1]中国科学院广州地球化学研究所同位素年代学和地球化学重点实验室,广州510640 [2]西藏地勘局区域地质调查大队,拉萨851400

出　　处：《岩石学报》2007年第6期1521-1530,共10页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2002CB412602);中国科学院知识创新工程重要方向性项目(KZCX3-SW-143);国家杰出青年基金项目(40425003);中国地质调查局国土资源大调查项目(200313000017)资助.

摘　　要：拉果错蛇绿岩位于西藏改则县南侧,是班公湖-怒江缝合带南侧蛇绿岩带中发育最完整的蛇绿岩之一,可能形成晚侏罗世—早白垩世,主要由地幔橄榄岩、堆晶岩、枕状熔岩、岩墙、斜长花岗岩及放射虫硅质岩等构造单元组成。微量元分析结果表明该蛇绿岩中的中基性岩富集 Sr、Rb 等大离子亲石元素,亏损 Nb、Ta 等高场强元素,具有岛弧型火山岩的特点其在稀土元素球粒陨石标准化配分图解中主要显示平坦型曲线,它们可能是由消减板片流体交代的地幔楔源区的部分熔,形成。拉果错蛇绿岩可能形成于弧间盆地环境,代表了班公湖-怒江缝合带南侧弧-弧碰撞的产物。Lhaguo Tso ophiolite, which is geographically located in south of Gerze county, Tibet, is one of the most completed ophiolites preserved on the south side of the Bangong-Nujiang suture zone. It was probably generated during Jurassic to Cretaceous and mainly consists of mantle peridotites,cumulates,pillow lavas,dykes,plagiogranites and radiolarian siliceous rocks units. Trace elements analyses indicates that mafic-intermediate rocks in the ophiolite are enriched in LILE,such as Sr,Rb, depleted in HFSE, such as Nb, Ta,clearly displaying compositional characteristicsof island-arc volcanic rocks, and their rare earth elements also mainly show a flat pattern. We suggest that these rocks be produced by partial melting of a mantle wedge metasomatized by the fluid released in the slab dehydration. Lhaguo Tso ophiolite likely occurred and developed in an inter-arc basin, representing the product of arc-arc collision on the south side of the Bangong-Nujiang suture zone.

关 键 词：蛇绿岩 地球化学 弧间盆地 拉果错 西藏 

分 类 号：P588.125[天文地球—岩石学] P594.1[天文地球—地质学]