大兴安岭东北部哈拉巴奇花岗岩体锆石U-Pb年龄及其成因

U-Pb chronology in zircon from Harabaqi granitic pluton in northeastern Daxing'anling area and its origin

哈拉巴奇岩体主要由二长花岗岩钾长花岗岩和花岗闪长岩组成。样品的LAICPMS锆石UPb年龄测定和主量及微量元素的分析结果表明,哈拉巴奇岩体为两次侵位的早古生代花岗岩体,其中二长花岗岩钾长花岗岩的侵位时间较早(500Ma),花岗闪长岩的侵位时间相对较晚(461Ma);岩体具有后造山花岗岩类的岩石组合特征和地球化学特征,为额尔古纳地块与兴安地块碰撞拼贴作用结束后的后造山阶段的产物;二长花岗岩钾长花岗岩和花岗闪长岩起源于相同的岩浆源区,其源区物质可能是中元古代期间地幔中新增生的地壳物质,二者地球化学特征的差别是源岩部份熔融程度不同所致。

Harabaqi granitic pluton is mainly composed of adamellite-moyite and granodiorite. The authors used LA-ICP-MS as zircon U-Pb dating and analyzed the major and trace element compositions in the granitic pluton. The results show that the pluton formed in Early Paleozoic, with intrusions for two times. The intrusion of adamellite-moyite （aged in 500 Ma） is earlier than of the granodiorite （461 Ma）. The pluton is marked by rock assemblage and geochemistry of postorogenic granite, and is the postorogenic pluton after collision between Erguna plot and Xing＇ an plot. The adamellite-moyite and granodiorite came from the ,same magma source, and the provenance may be the crustal substance from new accretion of mantle, The difference in geochemistry between the two kinds of rocks resulted from their distinct degree of partial melting of the provenance.