小兴安岭东段晚古生代花岗岩体的厘定及其地质意义

Determination of the Late Paleozoic granite and its geological significance in the eastern of the Lesser Xing’an Range

摘要: 通过LA-ICP-MS锆石U-Pb定年和岩石地球化学分析，研究了小白金河岩体的形成年代和地球化学特征。结果表明，小白金河岩体形成于261.7±3.8Ma，为中二叠世末期的侵入体。岩体具有高SiO2、K2O和ALK，低CaO、Al2O3和TiO2的特征；具有强烈的负Eu异常；强烈亏损Sr、Ti、V、P等高场强元素，富集K、Rb、Th等大离子亲石元素。研究表明，小白金河岩体属于A型花岗岩，形成于晚古生代弧后裂陷环境。

Abstract: In this paper, the age and geochemical characteristics of Xiaobaijinhe pluton were studied by LA-ICP-MS zircon U-Pb dating and geochemical analysis. The results show that the pluton formed at about 261.7±3.8Ma, being an intrusion of the Permian period. It is characterized by higher SiO2, K2O, and ALK，lower CaO, Al2O3 and TiO2 as well as stronger negative Eu anomalies. It is depleted in such HFSE as Nb, Ta, Zr, Hf, P and Th and enriched in LILE like K, Rb, Sr, Ba, Cs and Pb. It belongs to A-type granites and formed in the geological environment of back-arc basin in the late Paleozoic period.