扬子板块北缘马元铅锌矿床闪锌矿LA-ICP-MS微量元素特征与指示意义

Trace and Minor Elements in Sphalerite from the Mayuan Lead-Zinc Deposit,Northern Margin of the Yangtze Plate:Implications from LA-ICP-MS Analysis

马元铅锌矿床是我国近年来在扬子板块北缘探获的大型铅锌矿床,对马元铅锌矿床闪锌矿微量元素进行了高精度的LA-ICP-MS测试研究,结果表明矿床闪锌矿微量元素含量具有低Fe、Mn,高分散元素Cd、Ge、Ga,低分散元素In的特征;闪锌矿Fe、Mn含量和Ga/Ge比值特征指示了矿床成矿流体温度不高,可能为与中低温盆地流体有关的铅锌矿床;闪锌矿中分散元素In、Ge特征能有效的区分铅锌矿床的成因类型:与岩浆或火山活动有关的铅锌矿床闪锌矿具有高In或低In,低Ge的特征,而与盆地卤水有关的中低温矿床中闪锌矿则普遍富Ge贫In。依据马元铅锌矿床微量元素特征,结合矿床地质与地球化学特征,认为马元铅锌矿应属于密西西比河谷型铅锌矿床(MVT铅锌矿床)。

In recent years,the large-scale Mayuan lead-zinc deposit in the northern margin of the Yangtze plate, China has been explored. This paper focuses on trace elements found in sphalerite from the Mayuan lead-zinc deposit, using LA-ICP-MS method of analysis. The following conclusions were arrived at: sphalerite from the Mayuan deposit have a with low Fe and Mn content, as well as In. However, a high content of dispersed elements Cd, Ge and Ga was detected. The characteristic of Fe and Mn content and the Ga/Ge ratio in the sphalerite indicates that low temperature ore-forming fluids could be possibleand generated from basinal fluids. The genetic type of lead-zinc deposit could be effectively distinguished by In and Ge occuring in the sphalerite. The sphalerite with a high or low content of In, but with high levels of Ge, could be formed in the lead-zinc deposits related to the magma and(or) volcanic activity. Conversely, a characteristic high content of Ge but low content of In in sphalerite indicates that the Pb-Zn deposits, such as MVT and SST, may be related to low temperature basinal fluids. Based on the trace elements in the ore, combined with the geological and geochemical characteristics of the Mayuan lead-zinc deposit, we suggest this large-scale deposit could be classified as a MVT lead-zinc deposit.