滇西北雪鸡坪铜矿区岩浆岩大地构造环境及成矿意义

雪鸡坪矿区岩浆岩包括火成岩及侵入岩两类,该区矿体主要产出于侵入岩(斑岩)体的中—东部,该岩体由石英闪长玢岩、石英二长斑岩和二长花岗斑岩等组成。矿区岩浆岩SiO2质量分数为56.61%~66.18%,A/NCK值小于1.1;里特曼指数大多小于4,在化学成分上为高钾钙碱性系列,在岩石成因分类上为I型花岗岩。矿区斑岩体主要富集Rb、Ba、La、Hf、Ta和亲铜元素Cu、Pb等元素,亏损Th、U、P、Ti,在双变量协变图解上投点均落入火山弧花岗岩(VAG);微量元素、S-Pb同位素、Sr同位素初始比值均表明雪鸡坪矿区斑岩体为壳幔混合来源。结合区域地质背景认为甘孜—理塘洋壳俯冲的造山作用机制是雪鸡坪矿区岩浆岩体演化的构造背景。

Tectonic environment and metallogenic significance of magmatite in Xuejiping copper mine,northwest Yunnan

The magmatic rock in Xuejiping mine has included igneous rocks and instructive rocks.The ore-body is mainly occurred in the middle-eastern part of rock mass,which is composed of quartz diorite porphy-rite,quartz-monzonite porphyry and monzonitic granite porphyry.The SiO 2 mass fraction of magmatite is 56.61%—66.18% ,A/NCK value is less than 1.1.Besides,the Rittman index is mainly less than 4.The magmatite is belonged to high-K calc-alkali series in chemical constituents and belonged to I ype granite in petrogenesis.The porphyry body is mainly abundant in Rb,Ba,La,Hf,Ta and chalcophile elements of Cu and Pb,with a loss of Th,U,P and Ti.These diagram points are located at volcanic arc granite (VAG)in bivari-ate petrogenetic chart.The trace elements,S-Pb isotopic feature and initial ratio of Sr isotope indicate that the porphyry body is originated from crust-mantle mixed source.With combination to the research of re-gional geological background,this paper has pointed out that the orogeny mechanism of the Ganzi-Litang o-ceanic crust subduction was the tectonic background of magmatite evolution in Xuejiping mine.