西藏班戈地区青龙花岗闪长岩SHRIMP锆石U-Pb年龄及其地球化学特征

青龙岩体位于冈底斯带北麓，是班戈-嘉黎岩浆岩带的重要组成部分。该岩体主要岩性为花岗闪长岩，形成于白垩纪早期，SHRIMP锆石U-Pb 206Pb/238U年龄加权平均值为123.1Ma±3.4Ma，该年龄反映了青龙花岗闪长岩体的侵位或结晶年龄。花岗闪长岩地球化学数据表明，该岩体具有正常的SiO2含量，较低的K2O/Na2O比值，为弱过铝质岩石。该岩体轻稀土元素较重稀土元素富集，负Eu异常较弱。在微量元素蛛网图上，该岩体表现出强烈的Nb、Ta、Ti、Y负异常，具有岛弧花岗岩的地球化学特征。通过初步研究，认为青龙花岗闪长岩形成于俯冲背景，为与板片俯冲作用有关的同熔型花岗岩。

SHRIMP zircon U-Pb age and geochemical characteristics of Qinglung granodiorite in Baingoin area,Tibet

Located in the middle of Baingoin-Nujiang suture zone，the Qinglung rock mass is an important component part of the Baingoin-Lhari magmatic zone. The rock mass is composed mainly of granodiorite formed in Early Cretaceous. Zircon SHRIMP U-Pb age is 123.1±3.4 Ma，which reflects the age of pluton emplacement or crystallization. Geochemical data indicate that the rock mass has high SiO2 content and relatively low K2O/Na2O ratios, belonging to weakly peraluminous rocks. Qinglung rock mass is enriched in HREE and depleted in LREE，with relatively weak negative Eu anomaly. In the trace element spider diagram, granodiorite shows strong negative Nb, Ta, Ti and Y anomalies， similar to the island arc granite in geochemical characteristics. The tectonic setting of Qinglung rock mass was a subduction environment, mainly formed by the melting of the subduction slab.