青海省那陵郭勒河中游晚三叠世侵入岩地球化学特征及地质意义

那陵郭勒河中游位于东昆仑西段祁漫塔格地区,分布着大量的花岗岩。对该地区晚三叠世侵入岩的研究有助于认识东昆仑造山带印支期构造-岩浆演化历史。对研究区内花岗岩进行了岩石学、年代学及岩石地球化学分析。分析结果表明,研究区花岗闪长岩和二长花岗斑岩锆石LA-ICP-MS U-Pb年龄分别为(225.7±1)Ma、(213.74±1)Ma,为晚三叠世岩浆活动产物。岩石地球化学分析结果显示,该地区晚三叠世侵入岩属高钾钙碱性系列,饱和铝指数显示为偏铝质到过铝质,富集Rb、Th、K等大离子亲石元素和轻稀土元素,明显亏损Nb、P、Ti等高场强元素。花岗岩具有I型花岗岩特征,具有板块俯冲阶段的特征。通过分析认为岩浆岩形成于板块碰撞前的火山弧环境中。

Geochemical Characteristics and Geological Significance of Late Triassic Intrusive Rocks in the Middle Reaches of Naling Guole River,Qinghai Province

The middle reaches of Naling Guole River is located in the western part of Qimantage area in East Kunlun Mountains,where a large number of granites are distributed.The study of the Late Triassic intrusive rocks in this area is of help to understand the Indosinian tectono-magmatic evolution history of the East Kunlun orogenic belt.Petrological,chronological and geochemical analyses of granites in the study area were carried out.The results show that the zircon LA-ICP-MS U-Pb ages of granodiorite and monzogranite porphyry in the study area are(225.7+1)Ma and(213.74+1)Ma respectively,which are the products of late Triassic magmatism.The results of petrogeochemical analysis show that the Late Triassic intrusive rocks in this area belong to the high-K calc-alkaline series.The saturated aluminium index shows that they are meta-aluminous to peraluminous,enriched with large ion lithophile elements such as Rb,Th,K and light rare earth elements,and obviously depleted with high field strength elements such as Nb,P and Ti.Granite is characterized by highly differentiated I-type granite and plate subduction stage.The analysis shows that the magmatite formed in the volcanic arc environment before plate collision.