青海卡而却卡铜多金属矿床流体包裹体地球化学及成因意义

Fluid Inclusion Geochemistry in the Kaerqueka Copper Polymetallic Deposit,Qinghai Province and Its Genetic Significances

卡而却卡位于青海省东昆仑西段祁曼塔格地区,通过最近几年找矿成果显示其找矿潜力巨大.此次研究主要从包裹体测温入手,探讨流体包裹体的成因意义.并且通过对包裹体进行拉曼探针分析和氢氧同位素组成研究,说明了流体的化学成分以及流体来源,并在此基础上探讨了卡而却卡斑岩矿化带和矽卡岩矿化带流体之间的关系.对卡而却卡矿区流体包裹体测温结果研究表明,斑岩矿化带和矽卡岩矿化带成矿流体均分为高温、高盐度流体和中高温、低盐度流体两个端元,其中斑岩矿化带绢英岩化阶段是成矿主要阶段,均一温度集中区间为260～400℃,而矽卡岩矿化带矽卡岩期湿矽卡岩阶段均一温度也集中于260～400℃,该时期是成矿物质沉淀的主要阶段.可以看出,二者成矿阶段均一温度吻合.并且各自温度区间均有很好对应.通过对包裹体氢氧同位素组成研究,卡而却卡矿区成矿流体均来源于岩浆水,但斑岩型矿床流体局部存在着与大气降水的混合,显示出明显的“δ18O飘移”现象.激光拉曼探针分析结果显示,卡而却卡成矿流体为一套以H2O-NaCl为主,含有微弱CH4、CO2、H2S和N2的复杂组分体系.综上所述,卡而却卡斑岩型矿化带和矽卡岩型矿化带二者属于同一成矿系列,即碰撞后伸展导致酸性岩浆活动而形成的斑岩-矽卡岩铜钼铅铁多金属成矿系列.

Kaerqueka is located in the Qimantage area of the western part of East Kunlun Mountains,Qinghai Province.Recent prospecting results have showed its huge potential for mineralization.This study starts with the measurement of fluid inclusions of this deposit and further discusses its genetic implication.O and H isotopic compositions of fluid inclusions were tested using Raman method,indicating the compositions and origin of the ore-forming fluid.Based on this,the relation of porphyry mineralized belt and skarn mineralized belt of the Kaerqueka porphyry is also discussed.Thermometry results of fluid inclusion show that ore-forming fluids of both porphyry mineralized belt and skarn mineralized belt contain two members： high-T hypersaline fluid and medium-high temperature,low salinity fluid.Among them,the porphyry mineralized belt with sericite alteration was the major ore-forming stage with homogeneous temperatures ranging from 260to 400℃.While the homogeneous temperature of skarn mineralized belt at the wet skarn stage was concentrated around 260~400℃ and this stage was the main deposition period of mineralized material.Our study shows that two ore-forming stages have the same homogeneous temperatures.Study of H and O isotopic compositions of fluid inclusions suggests that the metallogenic fluid of Kaerqueka deposit mainly derived from magma water and the fluid of porphyry-type deposit was the mixing of magatic water and meteoric water,characterized by the distinctδ18 O shift.The Raman microprobe analysis results show that the metallogenic fluid of Kaerqueka deposit is characterized by a complicated system of H2OCO2-NaCl-CH4,in combination with tiny H2S and N2.In words,the Kaerqueka porphyry mineralized zone and skarn mineralized zone belong to the same metallogenic series,i.e.porphyry-skarns Cu-Mo-Pd polymetallic metallogenic series caused by felsic magmatic activity due to collision and post extension.