Accretion Processes of Oceanic Crust in Slow-spreading Ridges: Plagiogranite Perspective of the Xigaze Ophiolite, South Tibet
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Accretion Processes of Oceanic Crust in Slow-spreading Ridges: Plagiogranite Perspective of the Xigaze Ophiolite, South Tibet
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This work was supported by grants from the National Natural Science Foundation of China (Grant Nos. 41720104009 and 41772231) and the China Geological Survey Project (Grant No. DD20190060). We thank Prof. Ba Dengzhu for discussions that improved this paper.

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    Structural and petrological data suggest that the Xigaze ophiolite from the Yarlung Zangbo Suture Zone (YZSZ) in south Tibet was a typical slow-spreading ridge. A new field, geochemical, mineral, and U-Pb zircon dataset of plagiogranite intrusions were used to constrain the dynamic processes of oceanic accretion in this slow-spreading ridge. Plagiogranites mainly occur as dykes or intrusions intruded into the whole sequence of the ophiolite and have a similar orientation to the dolerite dykes developed in the late stage of detachment faulting. U-Pb zircon ages of 122–123 Ma were obtained for two types of plagiogranites and associated dolerite dykes. Detailed geochemical and mineralogical examinations suggest that the plagiogranites are the product of low-pressure (2–3 kbar) fractional crystallization of mid-ocean ridge basalt-like magma and unlikely to have been derived from the partial melting of hydrous gabbroic rocks. The complex cross-cut relationship between the plagiogranites and ophiolite sequence reflects that they are controlled by small discontinued melt lenses rather than a big magma chamber under the ridge axis and reveals multiple injections during the oceanic crust accretion. The formation of plagiogranites possibly reflects the complex characteristic of oceanic accretion at slow-spreading ridges, time-dependent on structural (external) and magmatic (internal) processes.

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LI Yuan, LI Ruibao, YANG Shengbiao, ZHANG Jian, YANG Jingsui.2022. Accretion Processes of Oceanic Crust in Slow-spreading Ridges: Plagiogranite Perspective of the Xigaze Ophiolite, South Tibet[J]. ACTA GEOLOGICA SINICA(English edition),96(6):1945~1959

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  • 收稿日期:2022-01-23
  • 最后修改日期:2022-06-21
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  • 在线发布日期: 2022-12-28
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