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Sulfide ore facies, fluid inclusion and sulfur isotope characteristics of the Tappehsorkh Zn-Pb (± Ag-Ba) deposit, South Esfahan, Iran
Geochemistry ( IF 2.6 ) Pub Date : 2020-01-27 , DOI: 10.1016/j.chemer.2020.125600
Mina Boveiri Konari , Ebrahim Rastad , Jan M. Peter , Flavien Choulet , Leyla Kalender , Ali Nakini

The stratiform, stratabound Tappehsorkh Zn-Pb (±Ag-Ba) deposit, located in the southeastern part of the Malayer-Esfahan Metallogenic Belt of Iran, formed during Lower Cretaceous back-arc extension. Sulfide mineralization occurs within dolostone, black siltstone, and crystal lithic tuff and andesite associated with the Gushfil-Baghabrisham synsedimentary normal fault. Three sulfide ore facies (massive, bedded, and stockwork) occur in the deposit. Sulfide minerals are sphalerite, galena, tetrahedrite and pyrite with minor chalcopyrite and bornite, and gangue minerals are barite, dolomite and quartz. Sulfide mineralization textures are massive, replacement, vein-veinlet, laminated, disseminated, and breccia

Three mineralization stages are distinguished: early, main and post-ore. An early fine-grained sulfide ore (early ore, stage I) occurs in the bedded facies which has synsedimentary textures such as laminated, disseminated and framboidal pyrite, galena and sphalerite. Coarse-grained sulfides in the brecciated, massive replacement, and vein-veinlet textures comprise main ore stage of mineralization (main ore, stage II) and formed during diagenesis via sub-seafloor replacement of protore by mixing of hydrothermal brines with cold seawater. Late, coarse-grained sulfides (post-ore, stage III) were formed during deformation and orogenic events and occur as strain fringes, foliation-like, and spindle textures. Pervasive hydrothermal alteration styles are predominantly dolomitization and silicification and minor sericitization occurs in all host rocks in the hanging-wall of the GBF.

Fluid inclusions within massive sphalerite of the main ore stage have trapping temperatures ranging from 118–199 °C, and salinities ranging from 6.2 to >23.32 wt. % NaCl equivalent. The δ34S values of the sulfide minerals from main ore stage ranges from -2.4 to -34.1‰, whereas barite ranges from +10.3 to +16.9‰. The negative values of the δ34S as well as the narrow range of δ34S in galena and sphalerite suggest that sulfur was derived by bacterial reduction of seawater sulfate.

The back-arc extensional tectonic setting, presence of a normal fault controlling sulfide mineralization and hydrothermal alteration, the siliciclastic-carbonate-volcanic lithology of the host rocks, magmatism in the region (pyroclastic and volcanic rocks, that also host the sulfide mineralization), the distribution of the three ore facies, and the negative sulfur isotope values all support a sub-seafloor diagenetic replacement SEDEX-type classification for the Tappehsorkh deposit, which was then affected by Laramide (?) orogenic events which imparted the post-ore stage mineral textures.



中文翻译:

伊朗南埃斯法罕的Tappehsorkh Zn-Pb(±Ag-Ba)矿床的硫化物矿物相,流体包裹体和硫同位素特征

层状,层状约束的塔佩赫索克锌-铅(±Ag-Ba)矿床,位于伊朗马勒-埃斯法罕成矿带的东南部,形成于下白垩统后弧伸展期间。硫化物矿化发生在白云岩,黑色粉砂岩和与Gushfil-Baghabrisham同沉积正常断层有关的晶体岩性凝灰岩和安山岩中。矿床中出现了三种硫化矿相(块状,层状和储层)。硫化物矿物为闪锌矿,方铅矿,四面体和黄铁矿,以及少量的黄铜矿和褐铁矿,脉石矿物为重晶石,白云石和石英。硫化物的矿化质地为块状,置换,静脉-静脉,层状,散布和角砾岩

分为三个矿化阶段:早期,主矿和后矿。早期细粒硫化矿(早期矿石,I期)出现在层状相中,该相具有沉积的质地,如层状,散布和黄铁矿黄铁矿,方铅矿和闪锌矿。角砾状,块状置换和脉孔状纹理中的粗粒硫化物包括矿化的主要矿石阶段(主要矿石,第二阶段),并在成岩作用期间通过将海底热液与冷海水混合而通过海底置换原型形成。在变形和造山过程中形成了较晚的粗粒状硫化物(矿石后,阶段III),并以应变条纹,类叶状和纺锤体质地出现。

主矿块块闪锌矿中的流体包裹体的圈闭温度范围为118–199°C,盐度范围为6.2至> 23.32 wt。NaCl当量百分比。的δ 34从主矿石阶段范围为-2.4至-34.1‰的硫化物矿物的价值观,而重晶石范围从10.3到16.9 +‰。的δ的负值34 S作为以及δ的窄范围34在方铅矿S和闪锌矿表明,硫是由细菌减少硫酸盐海水的衍生。

后弧伸展构造背景,正常的断层控制着硫化物的矿化和热液蚀变,主岩的硅质碎屑碳酸盐岩-火山岩性,该地区的岩浆作用(热碎屑岩和火山岩,也具有硫化物的矿化作用),三个矿石相的分布以及负硫同位素值均支持Tappehsorkh矿床的亚海底成岩替代SEDEX类型分类,然后受到拉拉米德(?)造山事件的影响,这赋予了矿石后阶段的矿物纹理。

更新日期:2020-04-21
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