Early Jurassic intra‐oceanic arc system of the Neotethys Ocean: Constraints from andesites in the Gangdese magmatic belt,south Tibet |
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| Authors: | Xuxuan Ma Zhiqin Xu Joseph Meert M. Santosh |
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| Affiliation: | 1. Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Department of Geological Sciences, University of Florida, 241 Williamson Hall, Gainesville, Florida 32611, USA;3. Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia 50005, Australia;4. School of Earth Sciences and Resources, China University of Geosciences Beijing, No. 29, Xueyuan Road, Haidian District, Beijing 100083, China |
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| Abstract: | The Gangdese magmatic belt is located in the southern margin of the Lhasa terrane, south Tibet. Here zircon U–Pb ages and Hf isotopic data, as well as whole‐rock geochemistry and Sr–Nd isotopes on andesites from the Bima Formation with a view to evaluating the history of the Gangdese magmatism and the evolution of the Neotethys Ocean. Zircon U–Pb dating yields an age of ca 170 Ma from six samples, representing the eruptive time of these volcanic rocks. Zircon Hf isotopes show highly positive εHf(t) values of +13 to +16 with a mean of +15.2. Whole‐rock geochemical and Sr–Nd isotopic results suggest that the magma source of these andesites was controlled by partial melting of a depleted mantle source with addition of continental‐derived sediments, similar to those in the southern arcs of the Lesser Antilles arc belt. In combination with published data, the volcanic rocks of the Bima Formation are proposed to have been generated in an intra‐oceanic arc system, closely associated with northward subduction of the Neotethyan oceanic lithosphere. |
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| Keywords: | andesite Gangdese magma evolution Neotethys Tibet zircon geochronology |
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