U-Pb zircon age and geochemical characteristics of Early Paleozoic granites in the Baoqing area, Heilongjiang Province

Detailed geochemical analysis and U-Pb zircon dating were carried out for Qiyilinchang syenogranite and Ganhegoukou monzonitic granite in Baoqing area, Heilongjiang Province. The results show that the ages of the syenogranite and monzonitic granite are 523.3±2.4Ma and 523.3±2.3Ma respectively, implying early Cambrian. Petrogeochemical studies show that they have the features of quasi aluminous peraluminous calc alkaline and high differentiation Ⅰ-type granite with high silicon, high aluminum and rich alkali. They belong to the type of LREE enrichment and HREE depletion. δEu=0.38~1.73, averaging 1.05. According to positive and negative Eu anomalies, the granites in Baoqing area are divided into positive Eu anomaly granite and negative anomaly granite. They are enriched in large ion rock elements (LILE) Rb and K, and depleted in high field strength elements (HFSE) Nb, Ta, P and Ti. Combined with regional tectonic background and chronology, the authors hold that, before early Proterozoic, Jiamusi-Xingkai massif might have belonged to the same continent of Gondwana and then, after the peak period of the Pan African movement, due to the collision of continental blocks, large quantities of Early Paleozoic granitic rocks were formed.