西天山可克萨拉呼斯特岩体地球化学特征及地质意义

Geochemical Characteristics and Geological Significance of the Husite Pluton in Kekesala,West Tianshan

呼斯特岩体为可克萨拉铁铜矿成矿岩体,由石英闪长岩、花岗闪长岩、二长花岗岩及正长花岗岩组成,时代均为晚泥盆世。岩石SiO_2含量为63.30%~69.16%,具有较高的全碱含量,且总体富钾、贫钠,(K_2O+Na_2O平均值为7.28%;K_2O/Na_2O平均值为1.08),ACNK均值为1.06,属准铝质-弱过铝质高钾钙碱性系列。岩体高LREE/HREE值平均为8.32,弱-中等负Eu异常(δEu=0.45~0.79,平均为0.71),富集大离子亲石元素(LILEs:Rb、Th、K、Zr),相对亏损高场强元素(HFSEs:Nb、Ta、Ti),总体显示火山弧花岗岩特点。矿区未发现与295Ma(辉钼矿Re-Os年龄)配套的具有后造山或是陆内地球化学特征的岩体。因此,呼斯特岩体地球化学特征佐证该岩体年龄仍是目前间接提供可克萨拉铁铜矿成矿时代的唯一依据。区内早二叠世辉钼矿化与可克萨拉铁铜矿化应是2次成矿事件的产物。

The Husite pluton serves as the ore-forming rock body of Kekesala Fe-Cu deposit,which is composed of quartz diorite,granodiorite,monzogranite and orthoclase granite.All of their ages are Late Devonian.This pluton has SiO2 content of 63.30%-69.16%,with high alkali content,rich potassium and low sodium（average K2O＋Na2O content of 7.28%;average K2O/Na2O ratio of 1.08）,belonging to quasi-aluminum and weakly peraluminous,high-K calc-alkaline series.This pluton has high LREE/HREE ratio（averaging in 8.32）and has negative Eu anomalies（δEu=0.45-0.79,with an average value of 0.71）.It is rich in large ionic lithophile elements（LILEs：Rb,Th,K,Zr and Hf）,but is depleted in high strength elements（HFSEs：Nb,Ta,Ti）,showing the characteristics of volcanic arc granite.No post-orogenic or intracontinental granite with an age of 295 Ma（molybdenite Re-Os age）has been found in this area.Therefore,the geochemical characteristics of the Husite pluton can prove that the age of this pluton serves as the only basis for indirectly providing the ore-forming age of the Keshala iron-copper deposit.The Early Permian Mo mineralization and Keshala iron-copper mineralization in the area should be theproducts of two metallogenic events.