桂西马雄金矿微量、稀土元素地球化学特征及其成矿指示意义

Geochemical characteristics of trace and rare earth elements in Maxiong gold deposit,West Guangxi and the metallogenic implication

马雄金矿床是桂西右江成矿带典型的微细粒浸染型金矿床。为了探讨其成矿物质和成矿流体来源,在野外调查基础上,对矿床的地质特征及微量元素、稀土元素地球化学特征进行研究。结果显示:马雄金矿矿石微量元素特征相似,相对富集Rb、Zr、Nb、Cs、Ba、W、Th、U等元素,Sr元素明显亏损,Sn、Hf、Y及Ta未见明显富集和亏损;矿石稀土特征曲线呈平缓右倾型,与辉绿岩稀土特征基本一致,均具轻稀土相对富集,重稀土略微亏损、分馏程度高、Eu中—轻度亏损、Ce无异常或轻微富集的特征。马雄金矿成矿流体性质相对稳定,与辉绿岩同源,均具壳幔混合特征,成矿流体体系主体以富Cl为特征的还原环境,主要成矿物质来源可能来自富矿围岩或深部流体,辉绿岩不是成矿物质的主要来源。

Maxiong gold deposit is a typical fine-grained disseminated type gold deposit in Youjiang metallogenic belt in West Guangxi.In order to explore the source of its metallogenic materials and ore-forming fluids,the geological characteristics and geochemical characteristics of trace elements and rare earth elements of the deposit are studied on the basis of field survey.The result shows that the characteristics of trace elements in the ore are similar.The ore is relatively enriched in Rb,Zr,Nb,Cs,Ba,W,Th,U and other elements.Sr is obviously depleted,and Sn,Hf,Y and Ta are not obviously enriched or depleted.The REE characteristic curve of the ore shows a gentle right dip type,which is basically consistent with the REE characteristics of diabase.The REE characteristics of the ore are relatively enriched in light REE,slightly depleted in heavy REE,high degree of fractionation,moderate to slight depletion in Eu,and no anomaly or slight enrichment in Ce.The ore-forming fluids of Maxiong gold deposit are relatively stable in nature,homologous with diabase and characterized by crust-mantle mixture.The main ore-forming fluid system is a reduction environment characterized by rich Cl,and the main ore-forming materials might come from rich-ore-bearing wallrocks or deep fluids,while diabase is not the main source of ore-forming materials.