西藏松多榴辉岩变质作用研究  

A study of metamorphism of Sumdo eclogite in Tibet,China.

作　　者：张丁丁[1,2] 张立飞[2] 赵志丹[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]北京大学地球与空间科学学院,北京100871

出　　处：《地学前缘》2011年第2期116-126,共11页Earth Science Frontiers

基　　金：国家重点基础研究发展计划"973"项目(2009CB825007);国家自然科学基金项目(40821002)

摘　　要：西藏拉萨地块松多附近新发现一条榴辉岩带,长约100 km,宽约2-3 km。松多榴辉岩主要经历了进变质的绿帘石榴辉岩相—峰期的榴辉岩相—退变质的角闪岩相3个阶段。岩石学研究表明,峰期的特征矿物组合是石榴子石-绿辉石-多硅白云母-金红石,峰期温压条件是760-800℃,3.3-3.9 GPa。这表明松多地区可能曾经历超高压变质作用,之后快速返回,p-T轨迹呈＂发卡＂状,后期退变质经历了角闪石榴辉岩相阶段。研究松多榴辉岩表明,拉萨地块内部有一条新的缝合带,这对于了解拉萨地块和古特提斯洋的演化有重要意义。A new eclogite belt,more than 100 km long and 2—3 km wide,was discovered in Sumdo in Lhasa terrain of Tibet.The studies show that the metamorphism of Sumdo eclogites has undergone three stages,i.e.,the prograde episode-eclogite facies,peak eclogite facies and retrograde amphibo-lite facies.According to geothermobarometry of garnet-omphacite-phengite-rutile,the p-T estimations of peak metamorphic stage are 760—800 ℃,3.3—3.9 GPa,which implies that the Sumdo eclogites may have undergone UHP metamorphism.The p-T paths are characterized by the clockwise hairpin-like shape,which indicates that the Sumdo eclogites have undergone fast subduction and exhumation.The discovery of Sumdo eclogites suggests that there may be a new suture zone in the Lhasa terrain,which would be very important for understanding the tectonic evolution of the Lhasa terrain and the Paleo-Tethys.

关 键 词：超高压榴辉岩 变质作用 松多 西藏 

分 类 号：P588.32[天文地球—岩石学]