Genesis of pyroxenite veins in supra-subduction zone peridotites:Evidence from petrography and mineral composition of Egiingol massif(Northern Mongolia)  

作　　者：Anas A.Karimov Marina A.Gornova Vasiliy A.Belyaev Aleksander Ya.Medvedev Nikolay V.Bryanskiy 

机构地区：[1]A.P.Vinogradov Institute of Geochemistry Siberian Branch of Russian Academy of Sciences,Irkutsk,Favorskogo str.,1A 664033,Russia

出　　处：《China Geology》2020年第2期299-313,共15页中国地质（英文）

基　　金：The reported study was funded by RFBR according to the research project(18-35-00535);IGC State Assignment Project(0350-2019-0008).

摘　　要：Swarms of orthopyroxenite and websterite veins are found within Egiingol residual SSZ peridotite massif of Dzhida terrain(Central Asian Orogenic Belt,Northern Mongolia).The process of Egiingol pyroxenite veins formation is investigated using new major and trace element analyses of pyroxenite minerals,calculations of closure temperatures and composition of equilibrium melt.The pyroxenites show abundant petrographic and geochemical evidence for replacement of the residual peridotite minerals by ortho-and clinopyroxene due to melt-rock interaction.Relics of peridotite olivines are found in pyroxenites,Cr#of spinel increases from peridotites to pyroxenites,and compositions of ortho-and clinopyroxene change from peridotite to pyroxenite.The authors show that calculated equilibrium melts for investigated pyroxenites are very similar to compositions of boninite lavas from the Dzhida terrain.Therefore,formation of pyroxenite veins most likely resulted from percolation of boninite melts through the Egiingol peridotites.Orthopyroxenite veins formed at first,followed by websterite veins.Thus,the authors assume that pyroxenite veins represent the channels for boninitic melts migration in supra-subduction environment.

关 键 词：Pyroxenite vein BONINITE Partial melting Melt-rock interaction Supra-subduction zone peridotite Egiingol massif Dzhida terrain Central Asian Orogenic Belt Northern Mongolia 

分 类 号：P542[天文地球—构造地质学] P588.125[天文地球—地质学]