摘要
摘要:尧勒萨依花岗岩出露于阿尔金北缘西段尧勒萨依河下游至河口一带，岩性为黑云二长花岗岩。为确定尧勒萨依花岗岩形成时代、成因和构造环境，本文从岩石学、锆石U-Pb年代学和地球化学方面进行研究。通过LA-ICP-MS锆石U-Pb定年，显示年龄为240±2 Ma，形成时代为中生代早期晚三叠世。其高硅（SiO₂=69.68%～70.64%）、富碱（Na₂O+K₂O）=9.61%～9.87%，里特曼指数σ=3.34～3.63，呈碱性；铝饱和指数（A/CNK）=0.73～0.80，属准铝质；大离子亲石元素U、Th、K、Rb等相对富集，高场强元素Ti、P、Ta、Nb等相对亏损；稀土含量较高，相对富集轻稀土且分馏明显，（La/Yb） _N=79.80～88.40，Eu弱亏损（δEu=0.79～0.85）。根据岩体成因类型及区域构造演化特征，认为尧勒萨依花岗岩为壳幔混合的Ⅰ型花岗岩，形成于阿尔金断裂走滑局部应力释放的伸展环境。
关键词: 岩石地球化学/
LA-ICP-MS锆石U-Pb年代学/
Ⅰ型花岗岩/
阿尔金北缘/
晚三叠世

Abstract:The granite distributed in midstream of the Yaolesayi River, the western part of North Altyn-Tagh, is mainly composed of biotite monzonitic granite. In order to find out the origin, formation age and tectonic setting of intrusive rocks in this area, studies of petrology, zircon U-Pb chronology and geochemistry were carried out. LA-ICP-MS U-Pb dating obtains the age of 240±2 Ma, corresponding to Late Triassic period of Early Mesozoic. We have learnt that the granite in research area is rich in silicon(SiO₂=69.68%~70.64%) and alkali(Na₂O+K₂O)=9.61%~9.87%. The Rittman index of the granite is 3.34~3.63, which shows a characteristic of alkaline series. The aluminum oversaturated index (A/CNK) is 0.73~0.80, which is a metaluminous series. The granite is rich in LILEs such as U, Th, K and Rb and depleted in HFSEs such as Ti, P, Ta and Nb. The granite is also characterized by high SREE, LREE enrichment, notable light and heavy REE fractionation(La/Yb) _N=79.80~88.40 and negative Eu anomaly(δEu=0.79~0.85). These characteristics suggest that the granite in research area is Ⅰ-type granite with a crust-mantle mixing origin. According to the regional geological data, it is considered that the Yaolesayi granite was formed in the extensional environment of local stress release of the Altyn fault.
Key words:Petrogeochemistry/
LA-ICP-MS zircon U-Pb chronology/
Ⅰ-type granites/
North Altyn Tagh/
Late Triassic



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