贵州晴隆锑矿田微量元素地球化学特征及其对成矿流体的指示意义

Geochemical Characteristics and Its Implications of Trace Elements in Qinglong Antimony Deposit,Guizhou Province,China

硅化凝灰岩是贵州晴隆锑矿田普遍发育的成矿作用产物。对比分析未蚀变凝灰岩、硅化凝灰岩、峨眉山玄武岩、萤石和辉锑矿稀土元素配分特征,以及某些高场强元素特征参数,探讨成矿流体物理化学特征。大厂层下段(P2d1)强硅化凝灰岩、中段(P2d2)近矿硅化凝灰岩及上段(P2d3)未蚀变凝灰岩Sb元素丰度显示,与峨眉山玄武岩喷发有关的凝灰岩可能是潜在的晴隆锑矿矿源层,后期热液带来部分矿质来源,热液改造作用是成矿物质富集的关键。凝灰岩蚀变前后稀土元素演化特征研究表明,成矿流体稀土元素含量很低、以富F-为特征且具有还原性。Y/Ho、Zr/Hf和Nb/Ta比值表明晴隆锑矿成矿流体具多源特征。辉锑矿稀土元素配分特征与国内其他辉锑矿有显著区别,其具有近似的W型四分组效应是继承海水或地层水稀土元素特征的表现。

Silicified tuff spreading over the whole Qinglong antimony deposit is a common product of mineralization in Guizhou Province. Indicated physical and chemical characteristics of ore-forming fluid were studied by comparatively analysing BEE and HFS elements＇ parameters of unaltered tuff, silieified tuff, Emeishan basalt, stibnite and fluo- rite. Antimony abundance of strong silieified tuff of lower member from Dachang strata （P2dt ）, medium silicified tuff from middle member （P2d2） and unaltered tuff from upper member （P2d3） showed that the tuff related to Emeishan basalt might be the potential source bed. The later hydrothermal deposit bringing some exterior minerals was the key to metallization. Ore-forming fluid is characterized by lower REE, higher F and reducibility. The ratios of Y/Ho, Zr/Hf and Nb/Ta indicated the polyphyleticism of ore-forming fluids. The REE patterns were significantly different from other antimony deposits＇. Its W-type tetrad effect was the preference of the fixation of seawater or groundwater REE onto sedimentary rocks.