Geology, mineralogy, and sulfur isotope geochemistry of the Sargaz Cu–Zn volcanogenic massive sulfide deposit, Sanandaj–Sirjan Zone, Iran
Geology, mineralogy, and sulfur isotope geochemistry of the Sargaz Cu–Zn volcanogenic massive sulfide deposit, Sanandaj–Sirjan Zone, Iran
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DOI：
10.1007/s00126-011-0357-4
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发表时间：
2011-05
影响因子：
4.8
通讯作者：
Z. Badrzadeh;T. Barrett;J. Peter;D. Gimeno;M. Sabzehei;M. Aghazadeh
中科院分区：
文献类型：
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作者：
Z. Badrzadeh;T. Barrett;J. Peter;D. Gimeno;M. Sabzehei;M. Aghazadeh
Sargaz铜锌块状硫化物矿床位于伊朗萨南达季-锡尔詹地区南部克尔曼省东南部。 Sargaz 矿床的地层下盘为上三叠统至下侏罗统 (?) 枕状玄武岩，而地层上盘为安山岩。镁铁质火山岩被安山岩火山碎屑和火山角砾岩覆盖，局部被异质泥石流覆盖。流纹英安岩流和火山碎屑岩覆盖在玄武岩和安山岩层序之上。根据火山活动的双峰性质、区域地质环境和火山岩的岩石化学，我们认为萨尔加兹的大量硫化物矿化形成于新生的青岩弧后盆地。 Sargaz 矿床目前的储量（经过古代开采）为 3 公吨，铜品位为 1.34%、锌品位为 0.38%、铅品位为 0.08%、金品位为 0.24 克/吨、银品位为 7 克/吨。块状硫化物透镜体在结构上被肢解，从富含黄铁矿的基底到富含黄铁矿的±±黄铜矿的中心部分和富含闪锌矿-黄铜矿的上部，以及上部侧面的富含闪锌矿的区域。主要硫化物矿物为黄铁矿，还有少量黄铜矿、闪锌矿。供给区由石英-硫化物-绢云母假角砾岩和最深处的绿泥石-石英-黄铁矿假角砾岩组成的脉网组成。下盘热液蚀变延伸到块状硫化物透镜体下方至少 70-80 m，并且从块状硫化物透镜体沿走向延伸超过一百米。硫化物矿床侧面的 Jasper 和 Fe-Mn 含燧石层代表了演化热液系统的低温热液沉淀物。根据矿物结构和共生关系，Sargaz矿床的生长历史是复杂的，包括：（1）海底硫化物（protore）的早期沉淀，作为细粒反面黄铁矿、闪锌矿、石英和重晶石的沉淀； （2）硬石膏在硫化物丘内的开放空间和矿物间隙中沉淀，随后溶解，形成角砾岩结构和丘碎屑，并沉淀出粗粒黄铁矿、闪锌矿、四面体-铁锰矿、方铅矿和重晶石； (3) 用在较高温度下沉淀的黄铜矿替代预先存在的硫化物（区域精炼）； (4) 继续“精炼”导致第三阶段黄铜矿溶解，并在块状硫化物透镜体的最下部形成贫贱金属黄铁矿体； (5) 碳酸盐岩脉被安置在硫化物透镜体中，取代了 2 级重晶石。硫化物的δ34S组成范围为+2.8‰至+8.5‰（平均为+5.6‰），随着块状硫化物透镜体和下伏网状带内深度的增加，δ34S比率普遍增加。较重的值表明一些硫源自海水硫酸盐，最终在深层热液反应区中热化学还原。
The Sargaz Cu–Zn massive sulfide deposit is situated in the southeastern part of Kerman Province, in the southern Sanandaj–Sirjan Zone of Iran. The stratigraphic footwall of the Sargaz deposit is Upper Triassic to Lower Jurassic (?) pillowed basalt, whereas the stratigraphic hanging wall is andesite. Mafic volcanic rocks are overlain by andesitic volcaniclastics and volcanic breccias and locally by heterogeneous debris flows. Rhyodacitic flows and volcaniclastics overlie the sequence of basaltic and andesitic rocks. Based on the bimodal nature of volcanism, the regional geologic setting and petrochemistry of the volcanic rocks, we suggest massive sulfide mineralization in the Sargaz formed in a nascent ensialic back-arc basin. The current reserves (after ancient mining) of the Sargaz deposit are 3 Mt at 1.34% Cu, 0.38% Zn, 0.08%Pb, 0.24 g/t Au, and 7 g/t Ag. The structurally dismembered massive sulfide lens is zoned from a pyrite-rich base, to a pyrite ± chalcopyrite-rich central part, and a sphalerite–chalcopyrite-rich upper part, with a sphalerite-rich zone lateral to the upper part. The main sulfide mineral is pyrite, with lesser chalcopyrite and sphalerite. The feeder zone, comprised of a vein stockwork consists of quartz–sulfide–sericite pesudobreccia and, in the deepest part, chlorite–quartz–pyrite pesudobreccia. Footwall hydrothermal alteration extends at least 70–80 m below the massive sulfide lens and more than a hundred meters along strike from the massive sulfide lens. Jasper and Fe–Mn bearing chert horizons lateral to the sulfide deposit represent low-temperature hydrothermal precipitates of the evolving hydrothermal system. Based on mineral textures and paragenetic relationships, the growth history of the Sargaz deposit is complex and includes: (1) early precipitation of sulfides (protore) on the seafloor as precipitation of fine-grained anhedral pyrite, sphalerite, quartz, and barite; (2) anhydrite precipitation in open spaces and mineral interstices within the sulfide mound followed by its subsequent dissolution, formation of breccia textures, and mound clasts and precipitation of coarse-grained pyrite, sphalerite, tetrahedrite–tennantite, galena and barite; (3) replacement of pre-existing sulfides by chalcopyrite precipitated at higher temperatures (zone refining); (4) continued “refining” led to the dissolution of stage 3 chalcopyrite and formation of a base-metal-depleted pyrite body in the lowermost part of the massive sulfide lens; (5) carbonate veins were emplaced into the sulfide lens, replacing stage 2 barite. The δ34S composition of the sulfides ranges from +2.8‰ to +8.5‰ (average, +5.6‰) with a general increase of δ34S ratios with depth within the massive sulfide lens and underlying stockwork zone. The heavier values indicate that some of the sulfur was derived from seawater sulfate that was ultimately thermochemically reduced in deep hydrothermal reaction zones.