湖南花垣矿田长登坡铅锌矿床闪锌矿微量元素组成与指示意义

Trace Element Composition and Indication Significance of Sphaleritein Changdengpo Lead-zinc Deposit in Huayuan Ore Field,Hunan Province

花垣矿田长登坡铅锌矿床位于湘西—鄂西铅锌多金属成矿带,是近年来新发现的代表性铅锌矿床之一。本次研究对长登坡铅锌矿床闪锌矿微量元素进行了高精度的LA-ICP-MS测定,结果表明闪锌矿具有低Fe、Mn,高Cd、Ge、Ga和低In的特征;闪锌矿Fe、Mn含量和In/Ga、In/Ge、Zn/Cd比值均指示矿床成矿温度不高,通过闪锌矿微量元素组成估算成矿温度为80~200℃,均值为136℃,指示该矿床成矿可能与中低温盆地流体有关;闪锌矿在(Ga+Ge)-(In+Se+Te)-Ag三角图解中的投点范围明显不同于SEDEX型矿床、VMS型矿床与矽卡岩型矿床,而与MVT型矿床有很大范围的重叠。综合分析认为,长登坡铅锌矿床属于MVT型铅锌矿床。

The Changdengpo lead-zinc deposit in the Huayuan ore field is located in the Western Hunan-Western Hubei lead-zinc polymetallic metallogenic belt.It is one of the representative lead-zinc deposits newly discovered in this area.In this study,the high-precision LA-ICP-MS is adopted to determine the trace elements in sphalerite from Changdengpo lead-zinc deposit.The results show that the sphalerite in this deposit has low content of Fe,Mn and In,but high Cd,Ge,Ga.The Fe,Mn content and ratio and of In/Ga,In/Ge and Zn/Cd in sphalerite all indicate that the temperature of the ore-forming fluid in the deposit is not high.However,the ore-forming temperature is estimated to be 80~200℃,with an average value of 136℃,based on the trace element composition of sphalerite,which indicates the sphalerite could be precipitated from the basinal fluids with mid-low temperature.In the trace element triangle diagram of sphalerite(Ga+Ge)-(In+Se+Te)-Ag,the range of sphalerite samples from the Changdengpo deposit is obviously different from the ranges of the SEDEX-type deposits,VMS and skarn-type deposits,but overlaps with the area of MVT deposits.Based on the trace element characteristics of the Changdengpo lead-zinc deposit,combined with the ore geology of this deposit,the authors propose that the Changdengpo lead-zinc deposit should be classified to the Mississippi Valley-type lead-zinc deposit(MVT lead-zinc deposit).