华南地区泥盆系MVT铅锌矿床S、Pb同位素特征

发布时间：2018-06-23 12:11

本文选题：密西西比河谷型 + 铅锌矿　；参考：《地质学报》2017年01期

【摘要】：华南泥盆系密西西比河谷型(MVT)铅锌矿床,受控于泥盆系海进序列的台地碳酸盐岩,大体可分为以凡口为代表的中低温热液型和以泗顶、北山为代表的低温热液型。在矿床学研究基础上,对研究区内不同类型的铅锌矿、硫铁矿开展系统的硫、铅同位素分析,收集和测定493件S和64件Pb同位素数据,总结硫、铅的来源和硫同位素分馏机制,并初步探讨了成矿机制。硫同位素研究显示,矿石硫有多种来源,主要来自于还原性卤水,部分来自氧化性卤水中ΣSO_4~(2-)的还原,少量硫来自于矿区含矿地层。不同矿床在成矿作用过程中硫同位素的分馏机制不同。在以凡口为代表的中低温热液矿床中,矿石δ~(34)S值高且相对集中,以热力学分馏为主,生物分馏作用较微弱;在以泗顶、北山为代表的低温热液矿床中,矿石δ~(34)S值低且分散,以生物分馏作用为主,仅部分中粗粒铅锌矿石以热力学分馏为主。成矿作用过程中硫同位素分馏远未达到平衡状态。不同矿床的矿石铅同位素组成呈线性分布,反映出不同来源铅的混合。古老铅来自遭剥蚀的古陆,年轻铅代表泥盆系沉积物的普通铅。二者的比例与岩石中陆源物质(Pb)的含量相对应。成矿时的铅直接来自于氧化性卤水,间接来自于卤水对流经的泥盆系含矿层(尤其是底部碎屑岩)的淋滤,更间接地来自古陆剥蚀区以及海相沉积物。金属物质的迅速沉淀成矿作用与两类流体的混合有关,氧化性卤水来自蒸发盐红层盆地,沿泥盆系底部紫色砂岩经区域性迁移,其中富含大量金属成矿元素,并含有少量呈ΣSO_4~(2-)的硫;而还原性流体中富含ΣH2S的硫。流体的混合作用局限于矿区范围内,并不存在区域性的简单大规模流体混合过程。
[Abstract]:The Devonian Mississippi River Valley type (MVT) lead-zinc deposit in South China, controlled by the platform carbonate rocks of the Devonian transgressive sequence, can be divided into moderate and low temperature hydrothermal type represented by Fankou and low temperature hydrothermal type represented by Siding and Beishan. On the basis of ore deposit study, the sulfur and lead isotopic data of 493 S and 64 Pb isotopes were collected and determined for different types of lead-zinc ore and pyrite in the study area. The sources of sulfur and lead and the mechanism of sulfur isotope fractionation were summarized. The metallogenic mechanism was also preliminarily discussed. Sulfur isotope studies show that there are many sources of sulfur in ore, mainly from reductive brine, partly from the reduction of 危 so _ 4- ~ (2-) in oxidized brine, and a little from ore-bearing strata. The fractionation mechanism of sulfur isotopes in different ore deposits is different. The 未 ~ (34) S value of ore is high and relatively concentrated, the thermodynamic fractionation is dominant, the biological fractionation is weak, and the 未 ~ (34) S value of ore is low and dispersed in the low-temperature hydrothermal deposit represented by Siding and Beishan. Biological fractionation is the main activity, and thermodynamics fractionation is the main component of the coarse lead zinc ore. Sulfur isotope fractionation is far from equilibrium during mineralization. The isotopic composition of ore lead in different ore deposits is linearly distributed, reflecting the mixing of lead from different sources. Ancient lead comes from the eroded ancient land, and young lead represents the common lead of Devonian sediments. The ratio of them corresponds to the content of terrestrial matter (Pb) in rocks. The lead during mineralization comes directly from oxidizing brines, indirectly from the leaching of the Devonian ore-bearing beds (especially from the bottom clastic rocks) flowing through the brines, and more indirectly from the paleocontinental denudation areas and marine sediments. The rapid precipitation and mineralization of metal matter is related to the mixing of two kinds of fluids. The oxidized brine comes from the evaporative salt red bed basin, and the purple sandstone moves along the bottom of the Devonian system through regional migration, which is rich in a large number of metal metallogenic elements. It also contains a small amount of 危 SO4-, while the reductive fluid is rich in 危 H2S. Fluid mixing is confined to the mining area, and there is no regional simple large-scale fluid mixing process.
【作者单位】：北京矿产地质研究院;中国地质调查局发展研究中心;广东凡口铅锌矿;有色金属矿产地质调查中心;
【基金】：中国地质调查局Ⅱ级项目“内蒙古赤峰有色金属基地综合质调查”(DD20160072) 国家科技支撑课题“湖南锡田地区深部成矿岩体空间结构与成矿预测”(2011BAB04B08) 全国危机矿山接替资源找矿项目“湘南-粤北地区锡钨多金属矿床成矿规律总结研究”(20089927)联合资助
【分类号】：P618.4;P597

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