青海省曲麻莱县活塔加查岩浆岩年代学、地球化学特征及地质意义

Geochronology,Geochemistry and Tectonic Significance of the Huotajiacha Magmatic Rocks in Qumalai County,Qinghai Province

岩浆岩记录了地球深部的动力学演化过程,开展活塔加查岩浆岩年代学、地球化学特征研究,探讨其地质意义,对巴颜喀拉盆地深部的构造研究具有重要意义。系统研究了活塔加查岩体英云闪长岩和石英花岗岩的U-Pb锆石年代学和主、微量元素地球化学特征。研究结果表明:活塔加查英云闪长岩成岩年龄为(212.1±1.3)Ma,石英闪长岩成岩年龄为(197.8±0.5)Ma,属晚三叠世-早侏罗世;活塔加查地区岩浆岩为准铝质-过铝质钙碱性I型花岗岩,具有高硅碱、Na_(2)O相对较高,低TiO_(2),大离子亲石元素Rb、Ba等相对富集,高场强元素Nb、Ta、Ti相对亏损,δEu弱负异常的特征;活塔加查花岗岩具弧型岩浆岩地球化学特征,形成于与古特提斯洋壳俯冲有关的火山弧挤压构造环境。

Magmatic rocks record the dynamic evolution process in the deep part of the earth.It is of great significance to study the chronology and geochemical characteristics of magmatic rocks in Huotagacha and discuss their geological significance.The research is of great significance for the study of deep structures in the Bayan Har basin.The U-Pb zircon chronology and geochemical characteristics of the tonalite and quartz diorite of the Huotagacha pluton are determined in this paper.The results indicate that the diagenetic age of tonalite is(212.1±1.3)Ma,and the diagenetic age of quartz diorite is(197.8±0.5)Ma,belonging to the Late Triassic-Early Jurassic.Geochemically,the magmatic rocks are metaluminous to peraluminous calc-alkaline I-type granites with high siliceous alkali and relatively high Na_(2)O,low TiO_(2).They are relatively enriched large ion lithophile elements Rb,Ba,etc,and depleted in elements Nb,Ta and Ti with negative Eu anomalies.The huotagacha granite rocks have the geochemical characteristics of arc magmatic rocks and were formed in the volcanic arc compression tectonic environment related to the subduction of the Paleo-Tethys oceanic crust.