Evolution of the Mesozoic granites in the Xiong'ershan-Waifangshan region, western Henan Province, China, and its tectonic implications.

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• 责任者：Han Yigui ; Zhang Shihong ; Pirajno ; Franco ; Zhang Yuanhou
• 年：2007
• 作者单位：China University of Geosciences, State Key Laboratory of Geological Processes and Mineral Resources, Beijing, China.
• 刊：Acta Geologica Sinica English Edition.
• 期：81,2

摘要

Based on the new isotope age data and geochemical analyses, three types of Mesozoic granites have been identified in the Xiong'ershan-Waifangshan region in western Henan Province: high-Ba-Sr I-type granite emplaced in the early stage (160 Ma), I-type granite emplaced in the middle stage (130 Ma) and anorogenic A-type granite emplaced in the late stage (115 Ma). Geochemical characteristics of the high-Ba-Sr I-type granite suggest that it may have been generated from the thickened lower crust by partial melting with primary residues of amphibole and garnet. The gradual increase in the negative Eu anomaly and Sr content variations reflect progressive shallowing of the source regions of these granites from the early to the late stage. New (super 40) Ar/ (super 39) Ar plateau ages of the early-stage Wuzhangshan granite (156.0+ or -1.1 Ma, amphibole) and middle-stage Heyu granite (131.8+ or -0.7 Ma, biotite) are indistinguishable from their previous published SHRIMP U-Pb ages, indicating rapid uplift and erosion in this region. The representative anorogenic A-type granite, the Taishanmiao Pluton, was emplaced at 115 Ma. The evolution of the granites in this region reveals a tectonic regime change from post-collisional to anorogenic between 160 Ma and 115 Ma. The genesis of the early- and middle-stage I-type granites could be linked to delamination of subducted lithosphere in the Qiniing orogenic belt, while the late-stage A-type granites represent the onset of extension and the end of orogenic processes. In fact, along the Qinling-Dabie-Sulu Belt, the Mesozoic granitoids in the western Henan, Dabieshan and Jiaodong regions are comparable on the basis of these temporal evolutionary stages and their initial (super 87) Sr/ (super 86) Sr ratios, which may suggest a similar geodynamic process related to the collision between the North China and Yangtze Cratons.