Geochemistry of Neoproterozoic granite in Liuyuan area of southern Beishan orogenic belt and its geological significance

In order to constrain the early Precambrian geological evolution of the southern Central Asian Orogenic Belt(CAOB),the authors studied geochemistry,zircon U-Pb ages,trace elements and Hf isotope of the Neoproterozic granitic gneisses in Liuyuan area of the southern Beishan orogenic belt,which is considered to be the southernmost region of the CAOB.These granitic gneisses belong to high-K calc-alkaline series with K2O content of 5.31%-7.02% and are characterized by enrichment of light rare earth elements(LREE) and large ion lithophile elements(LILE),depletion of Nb,Ta,Ti and Sr,and existence of positive Pb anomalies,similar to characteristics of post-collision granites.In-situ zircon U-Pb dating and trace element analysis using LA-ICP-MS reveal that 902Ma±5Ma(2σ) represents the formation age of the Liuyuan Neoproterozoic granite.The presence of -1.6Ga inherited zircon core indicates the adding of ancient crustal materials.On the other hand,these granites have relatively high eHf(t) values(-2.0-1.0),indicating that the parental magma contained juvenile mantle-derived materials.Therefore,Liuyuan Neoproterozoic granites might have been derived from the partial melting of ancient crust and juvenile mantle materials.In combination with previous studies,the authors hold that Liuyuan Neoproterozoic granite could be considered to be a result of the assembly of Rodinia supercontinent.