| The metamorphic series which is riched in marble in Atantayi,exposed on an area that is 200 meters distance about the Eastern Kepurte river in Xinjiang uygur autonomous prefecture,is in an east-west direction.The main rock type is felsic chist,Marble,a small quantity of eclogite and blueschist and a very small quantity of quartzite.The degree of this metamorphic series is quilt high-ranking that it could attached blueschist facies-eclogite facies.Synthesize the observation at Wilderness,hand specimens,the identity about the slide of sample,the analysis result about major element and trace element and various of geochemical discrimination diagram,finally infer that the protolith of this metamorphic series is turbidite/flysch formation with arenaceous pelitic,calcareous and calcareous and arenaceous pelitic rhythm interbed,in which have a small amount of island arc basalt and middle-ocean ridge basalt,these melange accumulation rocks constitute the proliferative wedge complex in subduction zones.The peak temperature and pressure conditions of felsic schist were obtained by means of electron probe analysis and mineral temperature and pressure gauge: 567?~632?(?T=±37?)and 2.2GPa~2.4GPa(?P=±0.2GPa),then calculate the maximum subduction depth of the subduction plate :86~89km.On this basis,made a basin-mountain coupling analysis of the southwest tianshan mountain and its peripheral basins by quantitatively calculated the material conversion relationship between the two within a certain error range,we deduce that the high-and ultrahigh-pressure metamorphic belt of the southwestern Tianshan folds back through buoyancy together with the overlying lithospheric. |
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