闪锌矿与方铅矿的LA-ICPMS微量元素地球化学对江西冷水坑银铅锌矿田的成因制约

发布时间：2018-07-29 18:34

【摘要】：冷水坑银铅锌矿田位于江西省贵溪市,是我国重要的银铅锌矿集区。矿田中产有两类特征迥异的矿体,一类为赋存于花岗斑岩体内的细脉浸染状-大脉状矿体,另一类为产于火山碎屑岩夹层中的块状硫化物矿体。然而,目前关于两类矿体的成因及联系还存在争议。本文采用激光剥蚀电感耦合等离子体质谱仪对两类矿体中的闪锌矿和方铅矿进行了微区原位成分的测试,试图根据它们的微量元素特征约束矿床的成因问题。分析结果表明,产于细脉浸染状-大脉状矿体中的闪锌矿具有相对较高的Fe、Mn、Pb、Ag、Cu、Sb、Sn和Tl含量,而产于层控块状硫化物矿体中的闪锌矿具有相对略高的Cd含量。两类矿体中方铅矿的微量元素也存在一定差别,前者具有相对较高的Ag、Sb、Sn和Au含量,而后者具有相对较高的Cd、Bi、Se和Tl。通过与国内外不同成因类型铅锌矿床的综合对比,我们发现冷水坑矿田的闪锌矿具有较低的Zn/Cd比(66~131)、Cd/Fe比(0.06~0.31)和Co含量(多数10×10~(-6)),以及相对较高的Sn含量(多数1×10~(-6)),这些特征与火山成因块状硫化物矿床中闪锌矿的特征十分类似,表明它们可能具有类似成因。此外,我们的研究结果表明冷水坑矿田闪锌矿中Fe、Cd、Ag、Sb和Tl等元素主要以类质同象的形式存在,而Cu、Pb和Sn等元素主要以显微包裹体的形式存在。方铅矿中的Ag、Sb、Cd、Sn和Tl等元素以类质同象的形式存在,而Mn、Bi和Se等元素可能以显微包裹体的形式存在。此外,基于闪锌矿-方铅矿共生矿物对的Cd分配系数温度计,获得层控块状硫化物矿体的形成温度为238~246℃,而细脉浸染状-大脉状矿体的形成温度略低,为209~224℃,前者闪锌矿中相对较低的Fe和Mn含量,可能由氧逸度的影响造成。综上所述,我们认为冷水坑矿田两类矿体具有相同的成因机制,成矿流体和成矿物质都主要来自深部岩浆热液,温度、围岩性质及氧逸度是控制两类矿床金属硫化物微量元素差别的重要因素。
[Abstract]:The Lengshuikeng silver lead zinc ore field is located in Guixi city Jiangxi Province and is an important silver lead zinc ore concentration area in China. There are two different types of orebodies in the ore field, one is the vein-disseminated and large-vein orebody in the granitic porphyry, the other is the massive sulfide orebody occurring in the intercalation of pyroclastic rocks. However, there are still disputes about the origin and connection of the two types of orebodies. In this paper, the in-situ composition of sphalerite and galena in two kinds of orebodies has been measured by laser denudation inductively coupled plasma mass spectrometer in order to limit the genesis of the deposits according to their trace element characteristics. The results show that the sphalerite occurring in the vein-disseminated and large-vein ore bodies has relatively high contents of Fe ~ (2 +) mn ~ (2 +) P _ (B) _ (B) _ (B) _ (Cu) Cu _ (+) SB _ (1) Sn and TL, while the sphalerite occurring in the stratabound massive sulphide orebodies has relatively high CD content. There are also some differences in trace elements of galena between the two types of orebodies. The former has relatively high content of Ag SbSbSn and au, while the latter has relatively high content of CdSbSe and Tl. Through comprehensive comparison with different genetic types of lead-zinc deposits at home and abroad, It is found that the sphalerite in the Lengyangkeng Orefield has a relatively low Zn/Cd ratio (66 / 131) / CD / Fe / Fe ratio (0.06 ~ 0.31) and Co content (most 10 脳 10 ~ (-6), and relatively high Sn content (most 1 脳 10 ~ (-6), which are very similar to the characteristics of zinc sphalerite in the volcanic massive sulphide deposits. This suggests that they may be of similar origin. In addition, our results show that the elements such as FebCdSb and TL in sphalerite in the cold water pit ore field mainly exist in the form of similar material, while the elements such as Cu, Pb and Sn are mainly in the form of microinclusions. In galena, the elements such as Ag SbSbCdcdnSn and TL exist in the form of metamorphic homology, while mn, Bi and se may exist in the form of microinclusions. In addition, based on the CD partition coefficient thermometer of sphalerite-galena symbiotic mineral pairs, the formation temperature of stratified massive sulphide orebodies is 238246C, while the formation temperature of vein-disseminated and large-veined orebodies is slightly lower, 2090.224 鈩，

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