Geochemistry and Geodynamics of Intermediate-acid Igneous Rocks in Northern Tekesi, Western Tianshan Mountains
详细信息
- 责任者：Zhu ZhiMin(Key Laboratory of Mineralogy and Metallogeny ; Guangzhou Institute of Geochemistry ; Chinese Academy of Sciences ; Guangzhou 510640 ; China) ; Zhao ZhenHua
- 刊名：Acta Petrologica Sinica
- 出版年：2012
- 卷期：28(7)
- 关键词：酸性岩 ; acidic rocks ; 天山 ; Tianshan Mountains
- 页码：p.2145-2157
- 图表：illus.,3 tables,71 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
A large number of intermediate-acidic igneous rocks are exposed along Yi-Te Road and in Kulesayi area,the north of Tekesi County,Western Tianshan Mountains,Xinjiang,China.These rocks are quartz-albite porphyry along Yi-Te Road and quartz diorite and granodiorite in Kulesayi area.They were produced during subducting of the Paleo-Asian oceanic crust.According to their geochemical features and isotopic compositions,the quartz-albite porphyries are typical island/continental arc rocks,and quartz diorite and granodiorite have the compositions of adakite characteristics and may have been produced by slab melting.The earlier cold subducted slab dehydrated before it could begin to melt,and the released fluid ascented into the mantle wedge,which caused melting of mantle wedge and succedent crust-mantle interaction,giving rise to the typical arc magmatism in Yi-Te Road area.As the subduction of oceanic crust continued,the newly formed plate close to the ridge would be hot enough to melt in a shallower depth leaving garnet and rutile as residual phases.This process gave rise to adakitic magmatism in Kulesayi area.Secondary ion microprobe(SIMS)zircon U-Pb dating indicates the Kulesayi porphyry crystallized at the age of 342.5±2.3Ma,which means the Paleo-Asian Ocean(South Tianshan Ocean)had not been completely closed in the Early Carboniferous.These results show that the massive magmatism along southern margin of Yili-Central Tianshan plate was triggered by continuing subduction of South Tianshan Oceanic crust.As thus in Carboniferous,crust growth in Western Tianshan Mountains was possibly mainly horizontal accretion,and the accretion materials may contain oceanic slab(adakite)and mantle wedge components.