High Pressure Metamorphism of Garnet-Amphibole Rocks from Songshugou Area,Eastern Qinling Mountain and Its Tectonic Implication

(整期优先)网络出版时间:1993-01-11
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Eclogiticgarnet-amphibolerocksarescatteredaroundtheSongshugouultramaficbodiesinQinlingMountains.Threemetamorphicstagesarerecognizedintermsofpetrography,mineralchemistryandgeothermobarometry.Thefirstalbite-amphibolestagewasofgreenschistfaciesmetamorphismwithtypicalmineralassemblageofactinolite+epidote+chlorite+albite;thepressureandtemperatureconditionswereequaltoorlowerthan500MPaandabout400℃.Thesecondprogradeeclogiticgarnet-amphibolestagewasofamphibole-eclogitefaciesmetamorphismwithtypicalmineralassemblageofgarnet+hornblende±clinopyroxene+rutilewithoutphagioclase,thepressureconditionwasatleast1000-1200MPaandthetemper-atureabout600℃.Thethirdretrogradeepidote-amphibolestagewasofepidote-amphibolitefacieswithassemblageofplagoclase+hornblende+epidote+ilmenite/titanite,thetemperaturewas500-600℃andthepressurefrom800MPadownto500MPa.AllthreestagestookplaceinonesingletectonothermaleventcalledJimingianmovementa