Zircon U-Pb Ages and Hf Isotopic Composition of the Pu Sam Cap High-Potassic Alkaline Rocks in
详细信息
- 责任者：Tran Mydung (State Key Laboratory of Geological Processes and Mineral Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Liu Junlai
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(6)
- 关键词：碱性岩 ; alkali rocks ; 越南 ; Vietnam
- 页码：p.1902-1914
- 图表：8 illus., 4 tables, 53 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Pu Sam Cap high-potassic alkaline rocks are located in western part of the southern segment of Ailao Shan-Red River shear zone. There into, the trachyte lays unconformably upon the Upper Cretaceous sedimentary rocks. The syenite and alkaline granite intruded the Triassic terrigenous sedimentary rocks, Jurassic rhyolite and amphibole-bearing granitic intrusion of 40～35 Ma. The Pu Sam Cap potassic alkaline rocks are ultrapotassic or shoshonitic enriched in LILE, LREE and compatible elements, and have marked Nb, Ta and Ti depletion, which is similar to a subduction related component and has the characteristics of post-collisional arc type potassic igneous rocks. Zircon LA-ICPMS U-Pb dating gives the emplacement age of 32.70±0.24 Ma for high-potassic syenite and 35.1±0.06 Ma for alkaline granite. It is suggested that the Pu Sam Cap high-potassic alkaline rocks were resulted from mixing between mantle and crust-derived magmas and may be derived from an EM2 mantle. The remnant of the subduction of Yangtze Plate beneath the Indochina plate during the closure of the Mojiang Paleotethyan oceanic basin, and the Cenozoic continental collision between Indian and Eurasian plates provide a broad tectonic background for the Pu Sam Cap potassic alkaline magmatism.
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