Jurassic Hornblende Gabbros in Dongga,Eastern Gangdese,Tibet:Partial Melting of Mantle Wedge and Implications for Crustal Growth

查看全文 作　　者：XU [1,2]Bo;HOU [2]Zengqian;ZHENG [1]Yuanchuan;ZHOU [2]Ye;ZHOU [3]Limin;YANG [4]Yu;HAN [5]Yanwei;ZHEN [6]Guo;WU [1]Changda

机构地区：[1]School of Earth Science and Mineral Resources,China University of Geosciences,Beijing 10083,China;[2]Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;[3]National Research Center for Geoanalysis,Chinese Academy of Geological Sciences,Beijing 100037,China;[4]State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earth quake Administration,Beijing 100029,China;[5]Kunming Foundation Engineering Company of China Nonferrous Metals Industry,Kunming 654000,China;[6]Department of Ocean Science and Engineering,South University of Science and Technology of China,Shenzhen,518055 China

出　　处：《Acta Geologica Sinica(English Edition)》索引2017年第91卷第2期,共20页

基　　金：jointly supported by The National Key Research and Development Project of China(2016YFC0600310);National Science Foundation of China(41320104004;41672197 and 41302054) 摘　　要：The Gangdese batholith, more than 2500 km in length, is composed mainly of JurassicMiocene igneous rocks. This batholith is one of the most important constituents of the Tibetan orogenesis and provides an ideal place for study of Neo-Tethyan ocean geodynamic evolution and plateau uplift. Recent studies on the Gangdese Jurassic felsic magmatism highlight its juvenile source. However, important aspects concerning the genesis of the juvenile magmatism and related deep geodynamic evolution are still unclear. Here, we report detailed petrological, geochronological, geochemical, whole-rock Sr-Nd isotopic, and in situ Sr-Hf isotopic data for a recently identified hornblende gabbro in the Dongga area, southern Lhasa sub-block. This hornblende gabbro is dominated by hornblende and plagioclase, dated at Early Jurassic(ca. 180–190 Ma), and characterized by a narrow compositional range in SiO_2(49.38wt%–52.27wt%), MgO(4.08wt%–7.00wt%), FeO(10.43wt%–11.77wt%), Na_2O(2.58wt%–3.51wt%), and K_2O(0.48wt%–1.53wt%). It has depleted isotopic signatures, with whole-rock(^(87)Sr/^(86)Sr)i ratios of 0.7033–0.7043, ε_(Nd)(t) values of +4.90 to +6.99, in situ plagioclase(^(87)Sr/^(86)Sr)i ratios of 0.7034–0.7042, and zircon ε_(Hf)(t) of +12.2 to +16.8. Our results integrated with published data suggest a model of Gangdese juvenile crustal growth by a subduction-related water-enriched mantle wedge. The hydrous partial melting of the lithosphere mantle was triggered by the dehydration of a Neo-Tethyan oceanic slab. This mafic magmatism emplaced in the middle-lower crust of intraoceanic arcs or active continental margins, leading to Jurassic juvenile crustal growth in southern Tibet. 关键词：地壳生长西藏南部部分熔融冈底斯地幔楔 Sr-Nd同位素地球动力学演化新特提斯洋

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Jurassic Hornblende Gabbros in Dongga,Eastern Gangdese,Tibet:Partial Melting of Mantle Wedge and Implications for Crustal Growth

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