LA-ICP-MS Zircon U-Pb Age, Geochemistry and Tectonic Setting of the Volcanic Rocks in the Heishantou Formation from the Area of Barleik, West Junggar
详细信息
- 责任者：Tian Zhixian (Institute of Oceanology ; Chinese Academy of Sciences ; Qingdao 266071 ; China) ; Yan Jun
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(3)
- 关键词：安山岩 ; andesite ; 玄武安山岩 ; basaltic andesite ; 铀—铅计时 ; U-Pb dating ; 准噶尔盆地 ; Junggar Basin
- 页码：p.343-352
- 图表：illus., 2 tables, 70 refs.
- 分类号：0801
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
The volcanic rocks of the Heishantou Formation in the area of Barleik, West Junggar, consist of gray purple (vesicular) almond andesite and almond shaped basaltic andesite, belonging to sub-alkaline series. High-precision LA-ICP-MS zircon U-Pb dating shows that the rocks formed at the age of 349 8Ma, with MSWD=0.14 (95% conf.), suggesting an age of Early Carboniferous. These rocks are characterized by moderate Mg# (23.82~50.4), relatively high alkali (Na2O+K2O=3.74%~8.02%), and relative enrichment in Na, enrichment in LREE \[(La/Yb)N=2.87~13.41\] and well fractionated \[(La/Sm)N=1.46~3.41\], and weak HREE fractionation \[(Gd/Yb)N=1.46~3.48\]. Only part of the samples shows weak negative Eu anomalies (δEu=0.82~1.47). Large ion lithophile elements (LILEs, eg., Ba, Th, K and Sr) are relatively enriched, especially Ba and K, and high field-strength elements (HFSEs, eg., Nb, Ta, and Ti) are depleted, but Zr and Hf slightly enriched. Geochemical features indicate that the volcanic rocks are the products of metasomatism between subduction-zone fluids and lithospheric mantle. Comprehensive analysis indicates that the volcanic rocks derived from active continental margin. The determination of the age and tectonic environment information of volcanic rocks from the Heishantou Formation provides new evidence for further understanding of the tectonic evolution in the area of Barleik in West Junggar