Oceanic lithosphere heterogeneity in the eastern Paleo-Tethys revealed by PGE and Re-Os isotopes of mantle peridotites in the Jinshajiang ophiolite  

作　　者：Yan-JunWang Wen-Jun Hu Hong Zhong Wei-Guang Zhu Zhong-Jie Bai 

机构地区：[1]State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,China [2]State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,China [3]Department of Earth Sciences,The University of Hong Kong,Hong Kong,China [4]College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Geoscience Frontiers》2021年第3期416-427,共12页地学前缘（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(Grant No.41425011)。

摘　　要：Platinum group elements(PGE)and Re-Os isotopes of mantle peridotites in the Jinshajiang ophiolite(SW China)were investigated in this study,in order to constrain the evolution of the lithospheric mantle beneath the Jinshajiang-Ailaoshan Ocean,which was a branch of the eastern Paleo-Tethys.The Jinshajiang peridotites have whole-rock compositions(e.g.,MgO=32.7-38.1 wt.%;Al_(2)O_(3)=0.67-1.30 wt.%)and spinels with moderate Cr#values(0.4-0.6)similar to those of abyssal peridotites,which indicate moderate degrees of partial melting(15%-20%).These peridotites exhibit U-shaped chondrite-normalized REE patterns that could be caused by hydrothermal alteration or melt-rock interaction after mantle melting.In addition,Pd concentrations and(Pd/Ir)_(N)ratios of the Jinshajiang peridotites increases with decreasing Al_(2)O_(3) concentrations.These negative correlations cannot be explained by simple partial melting but record a melt-rock reaction event after mantle melting.This study therefore demonstrates the efficiency of PGE in detecting the melt-rock reaction process relative to whole-rock major and trace elements.The suprachondritic^(187)Os/^(188)Os ratios(0.1272-0.1374)further indicate that the later percolating melt derived from a mantle domain with distinct^(187)Os-enriched isotopic compositions.In comparison with peridotites in the Ailaoshan ophiolite belt,which were not significantly affected by melt percolation,this study further highlights that the lithospheric mantle compositions beneath different segments of the same ocean basin are highly variable and might be controlled by distinct mantle processes in response to different rifting mechanisms.

关 键 词：Jinshajiang ophiolite PALEO-TETHYS Mantle peridotites Melt-rock reaction 

分 类 号：P588.125[天文地球—岩石学]