The petrography and mineral composition of a mantle-derived garnet peridotite xenolith from the V.Grib kimberlite pipe（Arkhangelsk Diamond Province,Russia） was studied.Based on petrographic characteristics,the perid...The petrography and mineral composition of a mantle-derived garnet peridotite xenolith from the V.Grib kimberlite pipe（Arkhangelsk Diamond Province,Russia） was studied.Based on petrographic characteristics,the peridotite xenolith reflects a sheared peridotite.The sheared peridotite experienced a complex evolution with formation of three main mineral assemblages：（1） a relict harzburgite assemblage consist of olivine and orthopyroxene porphyroclasts and cores of garnet grains（Gar1） with sinusoidal rare earth elements（REE） chondrite C1 normalized patterns;（2） a neoblastic olivine and orthopyroxene assemblage;（3） the last assemblage associated with the formation of clinopyroxene and garnet marginal zones（Gar2）.Major and trace element compositions of olivine,orthopyroxene,clinopyroxene and garnet indicate that both the neoblast and clinopyroxene-Gar2 mineral assemblages were in equilibrium with a high Fe-Ti carbonate-silicate metasomatic agent.The nature of the metasomatic agent was estimated based on high field strength elements（HFSE） composition of olivine neoblasts,the garnet-clinopyroxene equilibrium condition and calculated by REE-composition of Gar2 and clinopyroxene.All these evidences indicate that the agent was a high temperature carbonate-silicate melt that is geochemically linked to the formation of the protokimberlite melt.展开更多
基金financially supported by the Program for Development MSUsupported by the Russian Foundation for Basic Research, project Nos.15-05-03778a and 16-05-00298a
文摘The petrography and mineral composition of a mantle-derived garnet peridotite xenolith from the V.Grib kimberlite pipe（Arkhangelsk Diamond Province,Russia） was studied.Based on petrographic characteristics,the peridotite xenolith reflects a sheared peridotite.The sheared peridotite experienced a complex evolution with formation of three main mineral assemblages：（1） a relict harzburgite assemblage consist of olivine and orthopyroxene porphyroclasts and cores of garnet grains（Gar1） with sinusoidal rare earth elements（REE） chondrite C1 normalized patterns;（2） a neoblastic olivine and orthopyroxene assemblage;（3） the last assemblage associated with the formation of clinopyroxene and garnet marginal zones（Gar2）.Major and trace element compositions of olivine,orthopyroxene,clinopyroxene and garnet indicate that both the neoblast and clinopyroxene-Gar2 mineral assemblages were in equilibrium with a high Fe-Ti carbonate-silicate metasomatic agent.The nature of the metasomatic agent was estimated based on high field strength elements（HFSE） composition of olivine neoblasts,the garnet-clinopyroxene equilibrium condition and calculated by REE-composition of Gar2 and clinopyroxene.All these evidences indicate that the agent was a high temperature carbonate-silicate melt that is geochemically linked to the formation of the protokimberlite melt.
