阿尔泰可可托海地区泥盆纪花岗岩特征及其地质意义

阿尔泰南缘可可托海地区发育大量的400Ma左右的泥盆纪花岗岩。岩石SiO2含量在62.36%～77.41%, 里特曼指数σ介于0.43～1.88, A/CNK 值在0.97～1.12, 属中钾、钙碱性、准铝质-弱过铝质岩石。具有富集Rb、Th、U等大离子亲石元素和轻稀土元素, 相对亏损重稀土和Nb、Ta、Ti等高场强元素, 弱-中的负Eu异常的岛弧岩浆岩特征。结合区域地质资料, 可可托海地区泥盆纪花岗岩形成于活动大陆边缘的陆缘弧构造环境, 是古亚洲洋向北俯冲的产物。

Characteristics and Geological Significance of the Devonian Granitoids in Koktokay Area of Altay

The Koktokay area is located in the southern part of Altay, where Devonian granitoids were well developed and the ages of the granitiods are about 400 Ma. The SiO2 content ranges from 62.36% to 77.41%, and σ from 0.43 to 1.88, A/CNK from 0.97 to 1.12, implying the granitoid belongs to mid-K, calc-alkaline, quasi-aluminous and weak peraluminous rocks. In addition, they are enriched in LILE(Rb, Th, U) and LREE, obvious depleted of HREE and HFSE(Nb, Ta, Ti), besides, they have island-arc magmatite features characterized by weak-medium negative Eu anomaly. Combined with the regional geological data, the Devonian granitoids is a product of Paleo-Asian Ocean subduction toward north, and generated in an island-arc setting of active continental margin.