ZIRCON U-Pb AGE AND GEOLOGICAL BACKGROUND OF CARBONIFEROUS GRANODIORITES IN WUNUER AREA, DAXINGANLING MOUNTAINS

The LA-ICP-MS zircon U-Pb dating and petrogeochemical results show that the granodiorite in Wuluer area was formed in the Early Carboniferous, with weighted mean zircon U-Pb age of 332.6±6.9 Ma(MSWD=3.1), belonging to the quasi-aluminous low potassium(tholeiite) series. The granodiorite is generally characterized by enrichment of LILEs and depletion of HFSEs, as well as obviously positive Th and U anomalies, notably negative Nb, Ta, Zr and Ti anomalies, enriched La, Hf and Lu, and negative Eu anomaly, which is similar to I-type granite and has the characteristics of volcanic arc granite, indicating that the formation of the intrusive rock is related to subduction. Combined with the regional geological characteristics, it is concluded that the granodiorite is the product of subduction of Paleo-Asian Ocean in Early Carboniferous, which may provide new constraint and evidence for the study of tectonic evolution of Paleo-Asian Ocean and Northeast China block.