Zircon U-Pb ages and geochemical characteristics of the granites in Duobaoshan area, Northeast Da Hinggan Mountains

Abstract：The Duobaoshan area in Da Hinggan Mountains is tectonically located in a fold belt between the Songneng Block and the Xing’an Block in the east of the Xingmeng oregenic belt. Large quantities of Neopaleozolc granitic rocks are distributed in this area. This lithology is mainly composed of monzonitic granite and syenogranite. SHRIMP zircon U-Pb dating yielded ages of 309.0± 3.0Ma and 299.3± 2.8 Ma. Major element analyses show high SiO2 and alkali content, slightly high Al2O3 content and low MgO and CaO content. Trace element studies demonstrate the enrichment of Th, Zr, Rb, Nd, K and depletion of Ba, Sr, P, Ti. The samples are enriched in LREE (light rare earth elements) and depleted in HREE (heavy rare earth elements), suggesting a high degree of fractionation. The granites generally belong to the high-K calc-alkaline series and might have been produced by the magma that had experienced a high degree of crystallization differentiation. Petrological geochemistry shows that the granites are quite similar to S-type granite, with the material source derived from the crust.