| The Taerlang area belongs to the late Paleozoic back-arc rift basin in the central and southern Altai orogenic belt.Two sets of metamorphic rock groups and late Paleozoic intrusive bodies are mainly developed in this area.At present,there are still some controversies about the metamorphic rock characteristics,metamorphic stages and tectonic evolution model in this region,In this paper,the metamorphic rocks of the Kemuqi Group and Kanas Group in the Taerlang area are studied by means of petrogeochemistry,chronology analysis,protolith recovery of metamorphic rocks and tectonic environment discrimination,and the main metamorphic stages and related tectonic movements in the region are speculated.Precambrian age information of continental basement in this area.The results are as follows :The main types of rocks in the study area are plagioclase amphibolite,granulite,gneiss and marble,and the main types of metamorphism are regional low-temperature dynamic and hydrothermal metamorphism.Among them,the Kemuqi group formed earlier,and the chronology data obtained in this paper show that most of them are concentrated in 2200 Ma,which may contain precambrian continental basement information and are strongly cut by multi-stage magmatism.Geochemical characteristics show that the normal metamorphic rocks are alkaline-calc alkaline basalt and rhyolite.The total content of rare earth is low,the fractionation degree of light and heavy rare earth is low,and the distribution curve is slightly right-leaning.Trace elements Rb,Hf and Sc are relatively enriched,while Ba,Sr,Nb and Th are slightly depleted,indicating that their material source is the crust;Parametamorphic rocks are thick mudstone and sandstone,and the oxide content is close to the average content of lithic sandstone.REE fractionation is strong,Sr is low,Cr,Sc and Hf are slightly higher,and the distribution curve is strongly right-leaning.The source area is determined as the source area of continental island arc intermediate-acid volcanic rocks.The metamorphic rocks of the Kanas Group were formed far later than those of the Kemuqi Group,The geochemical characteristics of normal metamorphic rocks are calc-alkaline basalt and dacite.The REE distribution curve is relatively flat and the differentiation is not obvious.Geochemical characteristics of parametamorphic rocks show that rare earth elements are strongly right-leaning,light rare earth strongly fractionation,heavy rare earth fractionation is relatively weak,the content of large ion radius elements is low,and the content of small ion radius elements is high.Tectonic environment and provenance are identified as felsic or felsic-basic rock mixed areas in active continental margin-island arc environment.In this paper,the study of marble in the two rock groups is relatively less,only from the carbonate modulus and structure,source discrimination diagram speculated that it should be marine sedimentary environment.Metamorphic rocks in this area mainly experienced four metamorphic stages,Before the Jinning period,the Kemuqi Group was subjected to the dynamic heat flow metamorphism in the middle-low pressure region,and the metamorphic degree could reach the high amphibolite facies.The early Caledonian Kanas group was subjected to regional low-temperature and low-pressure metamorphism,with a metamorphic degree of low greenschist-low amphibolite,and the Kemuqi group was cut by the intrusion of this period.In the middle Caledonian,the Kemuqi Group and Kanas Group underwent retrograde metamorphism under regional low-temperature dynamic metamorphism;Two sets of metamorphic rock groups from late Caledonian to early Variscan were subjected to tectonic deformation,forming oriented feldspar,biotite and broken phenocryst.The intrusive bodies in the study area were subjected to partial low-grade metamorphism. |
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