%0 Journal Article
%T Upward mantle wedge convection recorded by Zhimafang orogenic garnet-lherzolite, Sulu UHP terrane, eastern China<br>洋壳俯冲过程中的地幔楔上升对流：来自芝麻坊石榴子石二辉橄榄岩早期变质的证据
%A SONG YanRu
%A YE Kai
%A XU HaiJin
%A <br>宋衍茹
%A 叶凯
%A 续海金
%J 岩石学报
%D 2009
%I 
%X Many orogenic garnet peridotite bodies are enclosed in ultrahigh-pressure (UHP) gneisses and/or migmatites in Sulu UHP terrane. On the basis of their field occurrence and bulk rock geochemistry, a group of garnet peridotites have been derived from depleted mantle and were subsequently metasomatized by melts and/or fluids derived from the subducted continental crust. However, their early stage depletion processes are still unclear. New evidence on early stage metamorphism of the garnet lherzolite from Zhimafang, Donghai County, Sulu UHP terrane are reported. Based on detailed analysis of reaction textures and mineral compositions, the Zhimafang garnet lherzolite have experienced at least two stages of metamorphism before they were evolved in high P-T subduction zone metamorphism. The protolith of the Zhimafang garnet lherzolite was a high-pressure and high-temperature fertile garnet lherzolite, which is defined by the high Ca-Cr core of garnet porphyroclast and inclusions of high-Mg clinopyroxene, high-Al-Cr orthopyroxene and high-Mg olivine. The rocks were then transformed to a high-temperature and low-pressure refractory spinel-hurzbergite or spinel-dunite, as indicated by the presence of abundant relict high-Al chromite and high-Mg, low-Ni olivine, as well as high-Mg orthopyroxene included in the low-Cr mantle of the porphyroclastic garnet and core of fine-grained neoblastic garnet, clinopyroxene is absent in this stage. The early stage metamorphic evolutions of the Zhimafang garnet lherzolite suggest that it experienced upward mantle wedge convection during the subduction of previous oceanic slab before they were evolved in the high P-T subduction zone metamorphism due to subsequent continental subduction. We propose that the Zhimafang garnet lherzolite were originated from deep, hot and fertile mantle wedge above the previously subducted oceanic slab, thermal buoyancy in the mantle wedge above the subducted oceanic slab resulted in their convection to shallower back arc and sub-arc mantle wedge, and decompressional melting transformed the enriched garnet-lherzolite to depleted spinel-hurzbergite or spinel-dunite.
%K Garnet-lherzolite
%K Oceanic subduction
%K Mantle wedge convection
%K Zhimafang
%K Sulu UHP terrane<br>石榴子石二辉橄榄岩
%K 洋壳俯冲
%K 地幔楔对流
%K 芝麻坊
%K 苏鲁超高压变质地体
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=621CF755B1A341E5&jid=2013B5467E3054B1614CEC199353FCED&aid=2416A1C88B836A927B851853C76CCC99&yid=DE12191FBD62783C&vid=C5154311167311FE&iid=CA4FD0336C81A37A&sid=2922B27A3177030F&eid=4C100B7696CE9E24&journal_id=1000-0569&journal_name=岩石学报&referenced_num=0&reference_num=65