张宏睿, 杨立强. 2022: 胶状黄铁矿成因类型与鉴别特征. 地质通报, 41(6): 1039-1052. DOI: 10.12097/j.issn.1671-2552.2022.06.011
    引用本文: 张宏睿, 杨立强. 2022: 胶状黄铁矿成因类型与鉴别特征. 地质通报, 41(6): 1039-1052. DOI: 10.12097/j.issn.1671-2552.2022.06.011
    ZHANG Hongrui, YANG Liqiang. 2022: Genetic types and identification characteristics of colloform pyrite. Geological Bulletin of China, 41(6): 1039-1052. DOI: 10.12097/j.issn.1671-2552.2022.06.011
    Citation: ZHANG Hongrui, YANG Liqiang. 2022: Genetic types and identification characteristics of colloform pyrite. Geological Bulletin of China, 41(6): 1039-1052. DOI: 10.12097/j.issn.1671-2552.2022.06.011

    胶状黄铁矿成因类型与鉴别特征

    Genetic types and identification characteristics of colloform pyrite

    • 摘要: 胶状黄铁矿广泛分布在多种地质体中, 对其成分标型进行深入研究可以获得大量成因信息。通过分析胶状黄铁矿的矿物形态、晶体结构, 并利用Fe-S、Co-Ni、S-Se、Se-Te和δ34S图解, 对胶状黄铁矿的组成特征进行对比研究, 可以有效区分其成因类型。沉积成因的胶状黄铁矿多呈球形、椭球状和团块状的聚合形态, Co/Ni<l, S/Se>2.5×104, Se/Te<0.45, δ34S值变化范围较宽(-13‰~+13‰), 显微镜下常具有鲕粒替代的假象结构。热液成因的胶状黄铁矿多呈不规则的脉状, 微观结构常具有一定的定向性, 1<Co/Ni<5, S/Se<2.5×104, Se/Te>0.45, 其中岩浆热液成因的胶状黄铁矿Co/Ni、S/Se和Se/Te均高于变质热液成因, δ34S值范围较窄, 通常集中于0~5‰。沉积成因的胶状黄铁矿成核和晚期环带生长的过程主要发生在厌氧的早期成岩阶段, 在硫酸盐还原菌的作用下结晶出纳米粒级的微晶黄铁矿, H2S存在的厌氧环境中, Cu、Zn、Mo等金属元素以硫化物固溶体的形式进入结晶的纳米级黄铁矿颗粒而富集。而热液成因的胶状黄铁矿可作为一种载体矿物, Au、As等元素按层状-岛状生长模型赋存在胶状黄铁矿的生长环带中; 中低温条件下可相变为磁黄铁矿等矿物, 进一步促进Cu等元素沉淀。

       

      Abstract: Colloform pyrite is widely distributed in various geological bodies and the genetic information can be obtained by in-depth study of its classification type.By comparing and analyzing the morphology, the internal structure and geochemical features, the hydrothermal and sedimentary colloform pyrite can be effectively distinguished.In combination with the mapping method of Fe-S, Co-Ni, S-Se, Se-Te and sulfur isotope mapping proposed in this paper, the trace characteristics of colloform pyrite of various genetic types were compared.The colloform pyrite of sedimentary origin is mostly spherical, ellipsoidal and agglomerated, with Co/Ni < l, S/Se > 2.5×104, Se/Te < 0.45, and a wide-ranging δ34S ratio(-13‰~+13‰).Under the microscope, mineral isomorphism of clay are often observed.The colloform pyrite of hydrothermal origin mostly occurs as irregular veins and has a certain orientation, with 1 < Co/Ni < 5, lower S/Se ratio(< 2.5×104), and the Se/Te ratio more than 0.45, as well as a narrow range of 34S ratio(0~ 5‰).Among them, the colloform pyrite Co/Ni, S/Se and Se/Te of magmatic hydrothermal origin are all higher than the metamorphic hydrothermal origin.The nucleated and growing process of sedimentary colloform pyrite origin is under the anaerobic condition.In the bacterial sulfate reduction zone with the H2S, metal elements such as Cu, Zn and Mo are enriched in the crystalline nano-sized pyrite particles in the form of sulfide melt.The colloform pyrite of hydrothermal origin can be used as a mineral carrier.Au, As and other elements occur in the zone of colloform pyrite as a consequence of heteroepitaxial Stranski-Krastanov growth.The mineralogical phase can be changed into pyrrhotite under the lower temperature, which promotes the precipitation of copper.

       

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