Geochronology, Geochemistry and Tectonic Significances of the Yamansubei Pluton in Eastern Tianshan, Northwest China
详细信息
- 责任者：Lei Ruxiong (Key Laboratory of Western China’s Mineral Resources and Geological Engineering ; Ministry of Education ; College of Earth Sciences and Resources ; Chang’an University ; Xi’an 710054 ; China) ; Wu Changzhi
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(8)
- 关键词：花岗岩 ; granite ; 铀—铅计时 ; U-Pb dating ; 天山 ; Tianshan Mountains
- 页码：p.2653-2664
- 图表：5 illus., 3 tables, 81 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Yamansubei granite pluton (YB) is situated in the Late paleozioic Qoltag orogenic belt,eastern Tianshan,Northwest China. Petrographically,the pluton is a K-feldspar granite,which is composed of quartz (25% ～ 40%),perthite (40% ～ 70%), plagioclase (10% ～ 25%,An = 18 ～ 30) and biotite (2% ～ 5%). Zircon LA-ICP-MS U-Pb dating shows that the YB pluton intruded at 227. 9 ± 0. 47Ma of Middle Triassic. Geochemically,the pluton is characterized by high silicon (SiO2 = 74. 27% ～ 75. 99%), alkali (ALK = 7. 64% ～ 8. 29%),potassium (K2O = 4. 37% ～ 4. 79%) and metaluminous,whereas low titanium,calcium,iron and magnesium,which attributes to high K calc-alkaline granite. The pluton is also rich in LILE (K,Rb,Cs etc.),HFSE (Th,U,Zr, Hf etc.) and depleted in Ba,Sr,Nb,Ta and Y. Chondrite-normalised REE distribution pattern for the YB pluton displays right skewed shapes with slightly negative Eu anomalies (δEu = 0. 48 ～ 0. 86) ,indicating fractionation of LREE,and fractionation between LREE and HREE. Zircon in-situ Hf isotopic composition analysis yields the εHf(t) and t DM2 values of the YB pluton varying +8. 60 ～ +11. 31 and 538 ～ 711Ma,respectively. Integrated studies in petrography,geochemistry and Hf isotope and regional tectonic evolution indicate that the YB pluton resulted from mantle magma underpalting induced partial melting of the Neoproterozoic new-born lower crust. After comprehensive study on previous contributions,this paper suggests that the geodynamic source for Indosinian magmatism in eastern Tianshan could attribute to the influence of the Paleo-Tethys ocean tectonic regime.