Silurian A-type granitoids in the southern margin of the Tongbai-Dabieshan: Evidence from SHRIMP zircon geochronology an
SHRIMP U-Pb dating on magmatic zircons extracted from a riebeckite quartz syenite in the Huangyangshan pluton in Suizhou, the southern margin of Tongbai-Dabieshan yielded an age of 439±6Ma. According to the morphology and high Th/U ratios of the zircons, the age is interpreted as crystallization timing of the pluton. The Huangyangshan pluton is composed of peralkaline quartz syenite, alkaline granite and syenite. All of the rocks are characterized by high agpaitic index (A.I.=(Na+K)/Al, molar ratio) and Fe-number [FeOT/(FeOT+MgO)], low CaO and MgO contents, enrichment of high field strength elements (i.e. Nb, Zr, Ga, Y, Hf) and light REEs, evidently negative Eu anomalies and high Ga/Al ratios, which are consistent with anorogenic A-type granitoids. Being part of the South Qinling-South Dabieshan Paleozoic alkaline rock belt, the Huangyangshan A-type granitoid pluton results from the Paleozoic extension-initial rifting in the northern margin of the Yangtze Craton related to the opening of the eastern Paleo-Tethyan Ocean.
作 者： MA Changqian SHE Zhenbing XU Pin WANG Lingyan 作者单位： State Key Laboratory of Geological Processes and Mineral Resources, and Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074, China 刊 名： 中国科学D辑（英文版） SCI 英文刊名： SCIENCE IN CHINA SERIES D(EARTH SCIENCES) 年，卷(期)： 2005 48(8) 分类号： P5 关键词： Dabieshan Orogenic belt A-type granite Silurian extension Paleo-Tethys