厄立特里亚阿斯马拉VMS矿床S、Pb同位素对成矿物质来源的约束

发布时间：2018-05-23 08:07

本文选题：硫同位素 + 铅同位素　；参考：《中国有色金属学报》2017年04期

【摘要】：阿斯马拉(Asmara)地区位于非洲东北部的厄立特里亚,是重要的VMS型矿床成矿带。对其矿石结构特征和成矿物质来源的分析研究有利于区域成矿规律的总结。在分析矿床成矿地质条件的基础上,研究Emba Derho和Debarwa VMS型矿床的矿石结构特征、矿石硫、铅同位素组成及闪锌矿中的流体包裹体特征。结果表明:Debarwa和Emba Derho矿床成矿作用在经过VMS过程之后,其后期的变形变质过程对成矿的改造和叠加作用有限。闪锌矿中的流体包裹体研究显示其成矿流体具有低盐度、中-高温的特征。Debarwa和Emba Derho矿床中黄铁矿、闪锌矿和黄铜矿等原生硫化物矿物的δ~(34)SCDT值变化范围较窄,数据集中在0.01%~0.48%之间,重晶石S同位素为高正值(δ~(34)S=1.66%~1.73%),具有地幔硫和海水硫的混合来源特征。Debarwa和Emba Derho矿床矿石铅同位素组成稳定,显示正常铅的特征。对矿石铅同位素进行特征参数示踪、铅构造模式示踪和Δβ-Δγ图解示踪的结果表明:Debarwa和Emba Derho矿床中矿石铅主要为地壳与地幔混合的俯冲铅。
[Abstract]:The Asmara area, located in Eritrea in northeast Africa, is an important VMS metallogenic belt. The analysis of ore structure characteristics and ore-forming source is beneficial to the summary of regional metallogenic law. Based on the analysis of ore-forming geological conditions, the ore structure, sulfur and lead isotopic compositions and fluid inclusions in sphalerite of Emba Derho and Debarwa VMS type deposits are studied. The results show that the ore-forming process of the W Debarwa and Emba Derho deposits is limited by the late deformation and metamorphism process after the VMS process. The fluid inclusions in sphalerite show that the ore-forming fluids have low salinity and medium-high temperature. In the Debarwa and Emba Derho deposits, there is a narrow range of changes in the SCDT values of the primary sulphide minerals such as pyrite, sphalerite and chalcopyrite, and the data are concentrated in the range of 0.01 ~ 0.48%. The S isotope of barite is high positive (未 ~ (34) S ~ (1.66) and 1.73 ~ (th). It has the characteristics of mixed source of mantle sulfur and seawater sulfur. Debarwa and Emba Derho deposits have stable lead isotopic composition of ore, indicating the characteristics of normal lead. The results of lead isotopic tracer, lead tectonic model tracing and 螖尾-螖纬 diagram show that ore lead in the W Debarwa and Emba Derho deposits is mainly subducted lead from crust and mantle.
【作者单位】：北京科技大学土木与资源工程学院;北京科技大学金属矿山高效开采与安全教育部重点实验室;中国地质调查局武汉地质调查中心;中国地质大学(北京);
【基金】：中国地质调查局工作项目(1212011220911) 国家自然科学基金资助项目(41372096,41672070)~~
【分类号】：P597;P612

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