Geological and Geophysical Studies of Sulfide Copper Mineralization in the Dochileh Area: An Example of Manto‐Type Deposit in the Sabzevar Zone, Iran

IF 1.1 4区 地球科学 Q3 GEOLOGY
Resource Geology Pub Date : 2019-12-19 DOI:10.1111/rge.12222
Susan Ebrahimi, A. Arab-Amiri, A. Kamkar-Rouhani
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引用次数: 3

Abstract

The Dochileh stratiform copper deposit in the Sabzevar Zone of northeastern Iran is hosted in the basaltic sequence of the Upper Eocene age. The host rock displays two hydrothermal events: zeolite–carbonate alteration that is a stratigraphic–lithologic feature and chlorite and chlorite/ferruginous alterations in the local mineralized structures. Ore formation is related to both hydrothermal events and occurs in both stratiform and vein mineralization types. Mineralization consists of main chalcocite with variable amounts of bornite, chalcopyrite, native copper, malachite, and cuprite minerals, which occur as hydrothermal breccias, and disseminated, vein, and veinlet forms. Geophysical field studies using resistivity and induction polarization (IP) methods were conducted along nine survey lines in the area. As a result of modeling and interpretation of the acquired geophysical data, high values of IP and resistivity corresponding to mineralization were observed at two depth levels: 0–20 m and more than 40 m. Based on these geological and geophysical investigations, six locations for drilling exploration boreholes were proposed. Drilling data confirmed the mineralization containing high copper values in the two depth levels: the vein‐type mineralization in the surface and shallow depth level, and the stratiform mineralization at the deeper level. Fluid inclusion studies in calcite and quartz from stratiform‐ and vein‐type mineralization show the evidence of mixing, and a linear dilution trend during the ore formation occurred at a wide range of temperatures: 121–308°C and 80–284°C, respectively, and varying salinities of between 3.2–16.8 and 0.8–22 wt% NaCl equivalents. The stable isotope composition of δ34S that falls in a range of −2.4 to +25.0‰ could be considered biogenetic sulfur from bacterial sulfate reduction and leaching of sulfur from hosting basalt. The δ13C values of calcite vary between −0.6 and −7.6‰, suggesting a major contribution of marine carbonates associated with igneous carbonates, and the δ18OSMOW values of calcite are between +15.2 and +19.9‰, suggesting a contribution of δ18O‐rich sedimentary rocks and δ18O‐poor meteoric water. Copper and sulfide‐rich hydrothermal fluid have flowed upward through the local faults and permeable interbeds within the Eocene volcanic sequence and have formed the mineralized veins and horizons. The geophysical results have detected the local faults as the channel ways for mineralization.
Dochileh地区硫化物铜矿成矿地质与地球物理研究——以伊朗Sabzevar地区Manto型矿床为例
伊朗东北部Sabzevar地区Dochileh层状铜矿赋存于始新世上玄武岩层序中。寄主岩石表现出两个热液事件:一是具有地层岩性特征的沸石-碳酸盐蚀变;二是局部矿化构造中的绿泥石和绿泥石/铁蚀变。成矿与热液活动有关,并以层状矿化和脉状矿化两种类型存在。成矿以辉铜矿为主,含不同数量的斑铜矿、黄铜矿、天然铜矿、孔雀石和铜矿矿物,以热液角砾岩、浸染状、脉状和脉状等形式赋存。利用电阻率和感应极化(IP)方法在该地区沿9条测量线进行了地球物理野外研究。通过对获取的地球物理数据进行建模和解释,在0-20 m和40 m以上两个深度上观测到与矿化对应的高激电和电阻率值。在这些地质和地球物理调查的基础上,提出了6个钻探钻孔的位置。钻探资料证实了在表层和浅层为脉状矿化,深层为层状矿化两个深度层次上均存在高铜值矿化。层状矿化和脉状矿化的方解石和石英的流体包裹体研究显示了混合的证据,并且在成矿过程中,在很宽的温度范围内(分别为121-308°C和80-284°C),盐度在3.2-16.8和0.8-22 wt% NaCl当量之间变化,呈线性稀释趋势。δ34S稳定同位素组成在−2.4 ~ +25.0‰范围内,可认为是细菌硫酸盐还原和寄主玄武岩硫浸出的生物成因硫。方解石的δ13C值在−0.6 ~−7.6‰之间变化,表明其主要贡献为与火成岩碳酸盐岩相关的海相碳酸盐;方解石的δ18OSMOW值在+15.2 ~ +19.9‰之间变化,表明其主要贡献为富δ18O -沉积岩和低δ18O -大气水。富含铜和硫化物的热液沿始新世火山层序的局部断裂和渗透性互层向上流动,形成矿化脉和层位。地球物理结果表明,局部断裂是成矿的通道。
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来源期刊
Resource Geology
Resource Geology 地学-地质学
CiteScore
2.30
自引率
14.30%
发文量
18
审稿时长
12 months
期刊介绍: Resource Geology is an international journal focusing on economic geology, geochemistry and environmental geology. Its purpose is to contribute to the promotion of earth sciences related to metallic and non-metallic mineral deposits mainly in Asia, Oceania and the Circum-Pacific region, although other parts of the world are also considered. Launched in 1998 by the Society for Resource Geology, the journal is published quarterly in English, making it more accessible to the international geological community. The journal publishes high quality papers of interest to those engaged in research and exploration of mineral deposits.
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