【摘要】 班—怒结合带中部班戈江错地区存在大面积侵入岩,该岩体主要岩性为花岗闪长岩及二长花岗岩、斑状二长花岗岩。样品LA-ICP-MS锆石U-Pb年龄为114. 94±0. 93 Ma和115. 5±1. 1 Ma,形成时代为早白垩世。花岗闪长岩大离子亲石元素Rb、Th、K富集,呈现正异常,明显亏损高场强元素Nb、Ti、Ta,形成环境为俯冲环境下的岛弧—陆缘弧环境;斑状二长花岗岩大离子亲石元素Rb、Th、K富集,呈现正异常,Sr、Ti强烈亏损,形成环境为同碰撞构造环境,表明该地区洋—陆转换作用过程于早白垩世完成,中特提斯洋闭合,进入陆—陆碰撞阶段。更多还原

【Abstract】 There are large-scale intrusive rocks in Baingoin area in the middle of Baingoin-Nujiang junction zone. The main lithologies of the intrusive rocks are granodiorite,monzonitic granite and porphyry monzonitic granite. The LA-ICPMS zircon U-Pb ages of the samples are 114. 94 ± 0. 93 and 115. 5 ± 1. 1 Ma,forming in the Early Cretaceous. Large ion lithophile elements Rb,Th and K in granodiorite are enriched showing positive anomalies,and high field strength elements Nb,Ti and Ta are obviously depleted,forming an island arc-continental margin arc environment in subduction environment. Large ion lithophile elements Rb,Th and K in porphyritic monzonitic granite are enriched,showing positive anomalies,while Sr and Ti are strongly depleted. The formation environment is a syn-collisional tectonic environment,indicating that the process of ocean-land conversion was completed in the Early Cretaceous,and the Middle Tethyan Ocean closed and entered the stage of land-land collision.更多还原