新疆昭苏卡拉盖雷铜(金)矿床酸性火山岩锆石U-Pb年代学、地球化学及其地质意义

新疆昭苏卡拉盖雷铜(金)矿床位于中天山北缘构造带西段,矿区主要出露一套基性、中-酸性的亚碱性火山岩。本次研究对其中的流纹岩、安山岩、霏细岩等酸性火山岩的锆石U-Pb测年结果为451~437Ma(前人对研究区的地质调查显示火山岩归属下石炭统大哈拉军山组),为晚奥陶世。地球化学测试结果显示主要呈高钾(2.26%~9.27%)、高铝(11.77%~16.66%)及亚碱性的特征,稀土元素中Eu呈现不同程度的负异常且轻稀土相对富集,微量元素特征显示主要富集Ba、Tu、U等大离子亲石元素,亏损Ta、Nb、Sr等元素。综合分析认为岩石具有大陆岛弧性质,岩浆主要经历了结晶分异作用,可能形成于造山后期的伸展背景下。

Zircon U-Pb dating and geochemistry of the acid volcanic rocks from Kalagailei Cu-Au deposit in Zhaosu, Xinjiang Province, and its geological implications

The Kalagailei copper-gold deposit which is mainly controlled by basalt, andesite, dacite and rhyolite is located in west part of the north side of the Central Tianshan tectonic belt in Zhaosu, Xinjiang Province. The LA-ICP-MS zircon U-Pb ages of rhyolite, andesite and felsite is between 451Ma and 437Ma belonging to Late Ordovician (It is suggested that the volcanic rocks is Lower Carboniferous Dahalajunshan formation). Geochemical analysis shows that the volcanic rocks are high in K2O (2.26%~9.27%) and Al2O3 (11.77%~16.66%) and belongs to a sub-alkaline series. The rocks are in enriched in LREE with negative Eu anomalies. In the spider diagram, they show enrichment in Ba, Tu and U, and depletion in Ta, Nb and Sr. Combined the regional tectonic settings with results of geochemical data, it is suggested that the volcanic rocks have a nature of continental arc and were probably generated by fractional crystallization in an extensional environment related to post-orogenic period.