Geochemistry and Isotopic Geochronology of Dacites from the Lower Permian Xiaotikanlike Formation in the Southern Margin of South Tianshan, and Its Tectonic Significances
详细信息
- 责任者：Luo Jinhai (State Key Laboratory of Continental Dynamics ; Department of Geology ; Northwest University ; Xi’an 710069) ; Che Zicheng
- 刊名：Acta Geologica Sinica
- 出版年：2012
- 卷期：87(1)
- 关键词：同位素地质年代学 ; isotopic geochronology ; 英安岩 ; dacites ; 岩石地球化学 ; lithogeochemistry ; 天山 ; Tianshan Mountains
- 页码：p.29-37
- 图表：illus., 4 tables, 19 refs.
- 分类号：0801
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Along the southern margin of South Tianshan occurs a 300-km-long EW-trending volcanic rock belt consisting of mafic,intermediate and acidic rocks of the lower Permian Xiaotikanlike Formation.Dacites outcropping near the Tiereke hot spring are characterized by calc-lkaline(δ=1.37~1.69) and metaluminous-peraluminous(A/CNK=0.89~1.36),enrichment in LREE(La/Yb=10.45~12.77) and elements such as Th,Hf,Zr,Tb,Gd,Rb,U,and depletion in elements such as P,Ti,Nb,Ta,Sr and Ba.They have a medium negative Eu anomaly(δEu=0.57~0.62),with εNd(288 Ma)=-6.77,εSr(288 Ma)=117.78,TDM=1.47 Ga.U-Pb LA-ICP-MS dating on zircon yields a weighted 206Pb/238U age of 288.4±3.0 Ma(MSWD=2.7).Combined with regional geological data,the dacites are likely the result of partial melting of mid-lower crust in the Tianshan orogenic belt,and formed in an post-collsional extension settings in early Permian.