Late Paleoproterozoic Columbia Supercontinent Aggregation Event In The Northeastern Margin Of The Tarim Craton: Constraints From Meta-pelites In The Kuruktag Area

Kuruktag(Quruqtagh)is located in the northeastern margin of the Tarim Craton.Precambrian basement rocks are widely exposed in this area,which is an important window to understand the Precambrian tectonic pattern and early crustal evolution of the Tarim Craton.In recent years,some scholars have carried out a lot of work in this area,and discussed in depth the widespread magmatic metamorphic events in the late Paleoproterozoic.However,previous studies mainly focused on isotope chronology and geochemistry.The research on the material composition,lithofacies characteristics,metamorphic evolution process and the combination with isotope chronology of metamorphic rocks is still very weak,and the P-T path of metamorphic evolution needs to be further improved.In this paper,the metamorphic argillite in the Xingditag Group of Kuruktag(Quruqtagh)is selected as the research object.On the basis of field geological observation,combined with detailed petrographic observation,the LA-ICP-MS zircon UPb dating,electron probe and other technical analysis methods are used to study the metamorphic age,metamorphic stage and temperature and pressure conditions,and the metamorphic P-T path is established.Combined with regional geological data and previous research results,the relationship between metamorphic-magmatic events and orogenic activities in the late Paleoproterozoic of Kuruktag(Quruqtagh)is discussed,which further provides new constraints for the performance of the northern margin of Tarim craton in the late Paleoproterozoic Columbia supercontinent convergence event.This paper mainly obtains the following five results and understandings:(1)Lithology of Xingditage Group in Kuruktag(Quruqtagh)consists of gneiss,marble,amphibole and granulite,U-Pb dating results show that the two garnet plagioclase cordierite metamorphic rocks record the ages of 1834�47 Ma and 1802�45 Ma respectively,and show obvious left-leaning trend in the standardized chondrite diagram of rare earth elements.The HREE overall relative loss((Gd/Yb)N)=0.03~1.93,mostly less than 1),with obvious negative Eu anomalies(Eu/Eu*=0.04~0.19).Combined with zircon CL images,it shows that it is metamorphic zircon,which represents the late Paleoproterozoic metamorphic recrystallization age.(2)Through detailed petrographic observation and mineral chemical analysis,the mineral assemblages of four metamorphic stages are identified,and the temperature and pressure conditions of each metamorphic stage are limited by a variety of temperature and pressure calculation methods: the mineral assemblage of progressive metamorphic stage(M1)is Grt+Bt +Pl+Q�Mus�St,and the temperature and pressure conditions are T>500�C,P=4~5 kbar;The mineral assemblage of peak metamorphic stage(M2)is Grt+Sill+Bt+Kfs+Pl+Q�Ilm,and the temperature and pressure conditions are T=754~800�C,P=6.1~7.4 kbar;The mineral assemblage in the post-peak near isothermal decompression stage(M3)is Grt+Sill+Crd+Q +Bt�Spl�Pl�Ilm,and the temperature and pressure conditions are T=732~784�C,P=3.8~4.7 kbar;The mineral assemblage in the cooling and demetamorphism stage(M4)is Grt+Pl+Bt+Q�And�Mus,and the temperature and pressure conditions are T=550~610�C,P=1.3~2.5 kbar.(3)Combined with the newly defined temperature and pressure conditions of each metamorphic stage,this paper obtains a clockwise P-T evolution path curve,which has the characteristics of near-isothermal decompression,indicating that there is a collision orogenic event in the late Paleoproterozoic of Kuruktag(Quruqtagh).In this event,the supracrustal rock was buried to the lower crust depth(18~22 Km)under the influence of compression and collision,and the high-angle amphibolite facies to granulite facies metamorphism occurred.Subsequently,due to the influence of gravity equilibrium,it began to return,and the process of near-isothermal decompression and cooling occurred.(4)Combined with regional geological data and previous research results,this paper argues that the orogenic event is synchronous with the orogenic movement of the major continental plates in the late Paleoproterozoic,which may be related to the Columbia supercontinent aggregation.