新疆东天山突出山铜铁矿区岩浆岩年代学、地球化学特征及地质意义

突出山铜铁矿床赋存于上石炭统底坎尔组火山岩中, 地质特征表明矿床成因为火山热液交代型。矿区玄武岩具有高Al、Na, 贫K、P、Ti的特点, 属于钙碱性系列火山岩。岩石具有轻稀土元素、大离子亲石元素相对富集和高场强元素相对亏损的特点。微量元素特征表明岩石与俯冲带流体作用有关, 经历了橄榄石(±辉石)和铬铁矿的结晶分异作用, 形成于石炭纪弧后盆地环境, 指示铁矿床的成矿环境为弧后盆地环境。矿区闪长岩和钾长花岗岩的锆石LA-ICP-MS U-Pb谐和年龄分别为326.2±1.6 Ma与318.2±2.5 Ma, 均为石炭纪岩浆活动的产物。根据闪长岩、钾长花岗岩、矿体与底坎尔组火山岩的穿插关系, 限定矿床的铁成矿作用时间为底坎尔组火山岩的形成时代, 早于闪长岩的形成时代(326 Ma), 而铜成矿作用时间与闪长岩的形成时代相近或稍晚。

Geochronology,geochemistry of magmatite from Tuchushan cooper-iron deposit in the eastern Tianshan of Xinjiang and its geological significance

Tuchushan copper-iron deposit is hosted in volcanic rocks of the Upper Carboniferous Dikan'er Formation. The genesis of mineral deposit is belong to volcanic hydrothermal metasomatic type. Basalts in ore district are rich in aluminum and sodium, but loss potassium, phosphorus and titanium, indicating that the rocks are calc-alkaline volcanic rock series. The rocks are characterized by enrichment of light rare earth elements, large ion lithophile elements and loss of high filed strength elements. The characteristics of trace elements show that genesis of rocks are related to fluid of subduction, primary magmas have experienced crystallization differentiation of olivine or clinopyroxene and chromite, also suggest basalts and iron orebodies were formed in back-arc basin environment. LA-ICP-MS U-Pb zircon dating on diorite and moyite from ore district yielded concordant ages of 326.2±1.6 Ma and 318.2±2.5 Ma, indicating that they were formed in Carboniferous. Based on the contacting relation of diorite, moyite, iron orebody and volcanic rocks, we hereby confine the age of iron mineralization is similar to the forming time of volcanic rocks of the Dikan'er Formation, which is before the age of diorite(326 Ma), but the age of copper mineralization is appreciably later than 326 Ma.