Rodinia Supercontinent Convergence Event In The Northern Margin Of Tarim

Large volume of Neoproterozoic igneous rocks are exposed in Tarim plate.The diagenetic age of these rocks and their tectonic significance in this area are important ways to understand the Neoproterozoic structural pattern of Rodinia supercontinent.However,because there are only a few data reports of Tarim plate between 900 and 830Ma,the unknown tectonic environment and the lack of igneous rock and magma reports in the same period,some scholars think it is the reflection of Rodinia supercontinent breakup,on the contrary,some scholars think it is the response of Rodinia supercontinent convergence.In this paper,the granodiorite of the oykuluke massif in the northern margin of Tarim is taken as the research object,and systematic petrology,geochronology,geochemistry and zircon HF isotopes are studied.Through the analysis of data and the summary of existing data,the genetic characteristics,crustal evolution and tectonic background are discussed,and the time limit of Tarim massif merging into Rodinia supercontinent is limited.This paper has achieved the following research results and understanding:(1)The LA-ICP-MS zircon U-Pb dating of the granodiorite from the oykuluke massif in the northern margin of Tarim shows that the crystallization age of the oykuluke massif is 855±29ma,which is the product of early Neoproterozoic magmatism.(2)The Si O2 content of granodiorite varies from 61.6%to 64.2%,Al2O3 content from 17.24%to 18.7%,total alkali(K2O+Na2O)content from 5.84%to 6.21%,K2O/Na2O content from 0.27 to 0.61(average value of 0.41),and ritmann index?from 1.6to 1.9.It is a quasi aluminous weakly peraluminous and calc alkaline series I-type granite.The total amount of rare earth elements(?REE)is between 129.41×10^-6and192.18×10^-6,and there is no obvious Eu anomaly.Enrichment of Rb,Ba,K,Sr and other large ion lithophile elements,loss of P,Ti,Nb,Ta and other high field strength elements,obvious positive anomalies of Sr and negative anomalies of Ti,Nb,Ta,belong to high Sr content granite.The negative anomalies of Nb and Ta indicate that the source area may be affected by the ancient subduction components.(3)The results of Hf isotopic analysis of zircon from the granodiorite of the oykuluke pluton(?HF(T)value is-15.12?-11.52,and tdm2 value is 2.46?2.66GA),indicate that the oykuluke pluton in the northern margin of Tarim is formed by melting of the lower crust from the late Neoproterozoic to the early Paleoproterozoic.(4)In this paper,zircon U-Pb dating and zircon Hf isotopic analysis of the aoyikuluke massif in the northern margin of Tarim are carried out.The results show that there is early Neoproterozoic magmatic activity related to plate subduction in the northern margin of Tarim,which indicates that there is a material record of Rodinia supercontinent convergence in the early Neoproterozoic in the northern margin of Tarim.