Research on HP Granulite-Facies Metamorphism and Anatexis: A Case Study of Dulan Area in the North Qaidam Mountains
详细信息
- 责任者：Yu Shengyao (State Key Laboratory of Continental Tectonics and Dynamics ; Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 10037 ; China) ; Zhang Jianin
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(6)
- 关键词：高压变质作用 ; high pressure metamorphism ; 麻粒岩相 ; granulite facies ; 柴达木盆地 ; Qaidam Basin
- 页码：p.2061-2072
- 图表：illus., 1 table, 66 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
In some typical subductional /collisional orogens,high-pressure granulite facies metamorphism often accompanies extensive anatexis. This article focuses on mafic HP granulite and leucosome in the Dulan area,the North Qaidam Mountains.0n the basis ofdetailed field observation,in combination with petrographic and geochronologicaldata,we will discuss the relationship between HP granulite-facies metamorphism and anatexis. In the field,the leucosome lithologies appear as veins,layers small leucocratic patches injected into the HP mafic granulite,and locally contain lenses,blocks or layers of mafic granulite,which show a migmatization and are considered as the principal evidence for partial melting. The mafic HP granulite primarily consists of garnet, clinopyroxene,plagioclase and quartz,withdistinct amounts of kyanite,amphibole,rutile,zoisite/clinozoisite,biotite,scapolite and chlorite. The leucosome is mainly composed of K-feldspar,plagioclase and quartz,with minor kyanite and garnet in some samples,which is analogous to typical felsic HP granulite. Cathoduluminescence ( CL) image of zircons in leucosome exhibits both anatectic and metamorphic origin,which yielded similar weighted mean236 Pb /238 U ages of434 ±2Ma ( MSWD = 1. 1) ,analogous to the existing geochronological data. Therefore,the combination of field relationship,petrography,geochemistry and geochronology defined identicaldynamic process for HP granulite-facies metamorphism and anatexis,suggesting that the high Sr/Y meltwas probably derived from partial melting of hydrous minerals ( e. g. amphibole,zoisite or mica) in the ( meta-) mafic rocks,leaving the mafic HP granulite as residuum.