南祁连化石沟铜矿区上石炭统克鲁克组大理岩C、O同位素特征

摘要

化石沟铜矿区位于南祁连西南缘之阿尔金与南祁连构造带的交会部位，是研究祁连-柴北缘构造-岩浆系统演化的关键地区。研究区内出露地层主要为古元古界达肯大坂群、泥盆-石炭系阿木尼克组和石炭系克鲁克组，晚古生代中酸性侵入岩发育。石炭纪克鲁克组中的大理岩，受侵入岩破坏，大部分呈残留体存在，与晚古生代石英闪长岩等共同构成沿化石沟的环形构造，前人认为其属于岩浆成因的碳酸岩。本次研究分析了克鲁克组大理岩的C、O同位素组成，δ13CPDB和δ18OSMOW值分别为-9.3‰～0‰和14.44‰～31.76‰，明显区别于碳酸岩，类似于沉积的碳酸盐岩的特征。结合区域大地构造背景，认为石炭纪克鲁克组大理岩应该形成于祁连-柴北缘造山作用停止之后，古特提斯洋发育的海相环境，而部分较低的δ13CPDB和δ18OSMOW值可能与侵入的石英闪长岩岩浆热液有关。%Huashigou copper mine is located about 120 km east of Akesai County,tectonically in the South Qilian area.The strata in the area are mainly distributed by Paleoproterozoic Dakendaban Group,Devonian-Carboniferous Amunike Formation and Carboniferous Keluke Formation.The marble,the main lithology of Carboniferous Keluke Formation,is considered to be carbonatite by former geologist as its closer relationship with quartz diorite of Huashigou copper mine.According to the determination and analysis of C,O isotopes,the result ofδ13CPDB andδ18OSMOW values (-9.3‰~0‰ and 14.44‰~31.76‰ respectivly) shows that the marble belongs to carbonate rocks originate from sedimentation,and lower δ13CPDB and δ18OSMOW values is probably related to the magmatic hydrothermal of intruding of quartz diorite.