伊什基里克山切特木斯铜矿区火山岩地球化学特征与成矿背景探讨

摘要

Carboniferous volcanic rocks from Qietemusi copper deposit in western Tianshan Mountains are composed of high potassium calc-alkalic andesite.These rocks characterized by high SiO2,Al2O3,Sr and low MgO,Y,Yb contents are similar to O-type adakite. And its geochemical characteristics show that they are enriched in LREE relative to HREE, as well as fractionated rare earth elements (REE). and also enriched large-ion-lithophile elements (LILE) such as Rb,Ba,Th,K, strongly depleted high-field-strength elements (HFSE) such as Nb.Ta and Ti.This indicates that they have an obviously blood relationship with volcanic-arc rocks and may be related to the subduction of the South Tianshan Ocean towards north beneath the Yili-Central Tianshan plate. Compared to Tuwu-Yandong porphyry copper deposit in eastem Tianshan Mountains. the Qietemusi volcanic rocks have the similar geochemical character and tectonic setting. Furthermore,crypto-explosion breccias, alteration patterns of porphyry copper deposits and low erosion level indicate that the exploration potentiality of porphyry copper deposit is remarkable.%新疆伊什基里克山切特木斯铜矿赋矿围岩主要由高钾钙碱性安山岩组成,该套火山岩具高SiO2,Al2O3,低MgO,富Sr,贫Y和Yb特征,具埃达克岩特征.地球化学特征表明,该矿区火山岩具轻稀土富集,重稀土相对亏损,铕轻微负异常,且富集大离子亲石元素(Rb,Ba,Th,K),相对亏损高场强元素(Nb,Ta,Ti),具大陆边缘岛弧火山岩亲缘性,可能形成于南天山洋向伊犁-中天山地块之下俯冲的火山岛弧环境.通过该矿区火山岩与土屋-延东地区火山岩对比,认为两地区火山岩地球化学特征相似,具岛弧火山岩特征,形成于相似构造环境.此外,含矿化的隐爆角砾岩筒、类似于斑岩型铜矿蚀变特征及较低剥蚀程度表明,切特木斯铜矿具寻找斑岩型铜矿潜力.