Geochemical Feature and Its Tectonic Significance of Gemucuo Oligocene Potassic Volcanic Rocks in the Qiangtang Area, oft-com:office:smarttags" />Tibet , China
详细信息
- 责任者：Zhao Zhi (College of Earth Sciences ; Jilin University ; Changchun 130061 ; China) ; Chi Xiaoguo
- 刊名：Geological Bulletin of China
- 出版年：2009
- 卷期：28(4)
- 关键词：火山岩 ; volcanic rocks ; 西藏 ; Tibet
- 页码：p.463-473
- 图表：8 illus., 2 tables, 36 refs.
- 分类号：0801
- issnNo：ISSN1671-2552
- isbnNo：CN11-4648/P
摘要
///There is a suite of potassic volcanic rocks (30 Ma) occurred in Gemucuo, Qiangtang area mainly composed of olivine tephrite, olivine trachy-basalt, aegirite augite trachyte and leucite phonolite. SiO2 content of this suit ranges from 46% to 60%, Al2O3 from 3% to 21%, Mg# from 0. 14 to 0.63, K2O/Na2O ratio is above 1. The volcanic rocks are enriched in LREE and depleted in compatible element (Cr、Ni)and HFSE (Nb、Ta、Ti). The εHf (t) of whole rock mass ranges from -1.28 to -6.20. It is indicated that the primary magma source originated from minor melting of an ancient subduction mantle wedge which was metasomatised of astheno-sphere fluid, and consanguineous igneous magma went through AFC (Assimilation Fractional Crystallization).