Cretaceous Meteorite Impact-Induced Initial Subduction:Records of highly Siderophile Element Abundances and Re-Os Isotopes in Ophiolites  

作　　者：Benxun Su 

机构地区：[1]Key Laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China [2]University of Chinese Academy of Sciences,Beijing,100049,China

出　　处：《Journal of Earth Science》2022年第6期1526-1534,共9页地球科学学刊（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(No.91755205);the Open Fund Project of the State Key Laboratory of Lithospheric Evolution(No.SKL-K202202);the Youth Innovation Promotion Association,Chinese Academy of Sciences。

摘　　要：Compiled global ophiolite data reveal that Cretaceous ophiolites exhibit broaden variations in 187Re/188Os and ^(187)Os/^(188)Os values,increases in Re concentrations and thus Re/Os ratios in all peridotites and chromitites,and additional increased PPGE/IPGE(Pd-subgroup platinum-group element(PGE)/Ir-subgroup PGE)ratios in chromitites and dunites relative to pre-Cretaceous ophiolites.These compositional changes in Cretaceous ophiolites,which mostly formed in subduction initiation settings,cannot be attributed solely to involvement of subducting or previously subducted crustal materials.Here,the author proposes a Cretaceous meteorite impact model that led to impact-induced disruption of oceanic lithosphere,asthenosphere upwelling,subduction initiation at edges of laterally spreading anomalies.High-pressure and high-temperature conditions during the impacts caused melting of the meteorites and the ambient crustal and mantle rocks,producing hybrid melts containing partially un-melted fragments.Crustal materials contributed to the elevated ^(187)Os/^(188)Os values,Re and Re/Os ratios,whereas the undifferentiated meteorite accounted for the increases in the PPGE/IPGE and decreased ^(187)Os/^(188)Os ratios.Shock pressure and super-reduced phases were likely generated by this process and were subsequently transported into the newly formed mantle peridotites and chromitites of future ophiolites.The remaining meteoritic and lithospheric fragments most likely sank deeper and were distributed widely in the convecting mantle to produce the observed global compositional heterogeneities.

关 键 词：Re-Os isotopes OPHIOLITES PGE METEORITES subduction initiation oceanic lithosphere 

分 类 号：P534.53[天文地球—古生物学与地层学] P597[天文地球—地质学]