青藏高原玉树混杂带糜棱岩化石英闪长岩年代学和地球化学研究  

Chronology and geochemistry of mylonitic quartz diorites in the Yushu mélange,central Tibet

作　　者：张洪瑞[1] 杨天南[1] 侯增谦[1] 宋玉财[1] 程先锋[1,2] 丁妍[1,3] 陈文[1] 侯可军[4] 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]云南国土资源职业学院,昆明650217 [3]山东黄金地质矿产勘查有限公司,莱州261400 [4]中国地质科学院矿产资源研究所,北京100037

出　　处：《岩石学报》2013年第11期3871-3882,共12页Acta Petrologica Sinica

基　　金：国家973项目(2009CB421001;2011CB403100);国家自然科学基金项目(41102040);中国地质调查局项目(1212011220908);国际地学对比计划(IGCP/SIDA-600)联合资助

摘　　要：玉树混杂带内含有大量金沙江西段古特提斯演化信息,对其物质组成进行详细解剖,有望厘清青藏高原东北缘的特提斯演化过程。本文以该带内糜棱岩化岩体为研究对象,研究其岩石学、构造变形特征,报道其锆石U-Pb年龄、黑云母ArAr年龄、主量、微量和Sr-Nd同位素数据,结合区域岩浆事件和构造变形资料讨论大地构造意义。研究表明该岩体主要为石英闪长岩,变形强烈,发育北西西向糜棱面理,面理走向与区域构造线一致。岩石为准铝质中-高钾钙碱性系列,富集K,Rb,Ba,Th等大离子亲石元素,亏损高场强元素,具有高Sr负Nd的同位素组成,为基性下地壳部分熔融的产物。石英闪长岩锆石U-Pb年龄为208Ma,黑云母40Ar/39Ar年龄为201Ma,讨论认为前者代表岩浆结晶年龄,形成于洋盆俯冲背景;后者代表变形年龄,与区域碰撞挤压有关。The tectonic evolution model of the west segment of the Jinshajiang Paleo-tethyan are hotly debated. Located in the northern margin of the eastern Qiangtang block （ EQ ）, the Yushu m61ange is very important for understanding the Paleo-tethyan evolution. Zircon U-Pb and biotite 40Ar/39Ar dating document a Late Triassic generation and deformation time for the Yushu quartz diorite from the northern margin of EQ. The pluton has elongated shape, deformed fabric, with some granodiorite vein intrusive. The quartz diorites exhibit strong enrichment of large ion lithophile element and light rare earth element, depletion in high field strength element, and have enriched isotopic compositions with （87 Sr/S6 Sr）i ranging from 0. 70783 to 0. 71064 and ZNd （t） from -3. 6 to -5.9. These features suggest that they were derived from marie lower ernst; the Yushu_mylonitie pluton likely represents magmatic expression of subducting Paleo-Tethyan slab and deformed during the collision of EQ with Eurasia continent in Triassic.

关 键 词：锆石U-PB年龄 黑云母Ar-Ar年龄 地球化学 糜棱岩化石英闪长岩 玉树混杂带 古特提斯 

分 类 号：P588.122[天文地球—岩石学] P597.3[天文地球—地质学]