The Ak-Sug Porphyry Copper–Gold–Molybdenum Deposit, East Sayan: Noble Metal Mineralization, PT-Parameters, and Composition of Ore-Bearing Fluid

IF 0.8 4区地球科学 Q3 GEOLOGY Geology of Ore Deposits Pub Date : 2024-03-06 DOI:10.1134/s1075701523070188

R. V. Kuzhuget, N. N. Ankusheva, A. K. Khertek, A. O. Mongush, Yu. V. Butanaeva

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Abstract

Ore mineralization of the Ak-Sug Porphyry Copper–Gold–Molybdenum deposit formed during three stages: 1) porphyry-copper mineralization with simple sulfides in quartz–sericite and quartz–sericite–chlorite metasomatites, 2) subepithermal Au–Bi–Te–Pd-quartz mineralization in quartz–sericite metasomatites, and 3) intermediate-sulfidation Au–Ag mineral assemblages with selenides, tellurides, and Sb and As sulfosalts in argillisites. Fluid inclusion studies (microthermometry, Raman spectroscopy) of quartz and mineral thermometry (an assemblage of Au and Ag tellurides) showed that porphyry copper and subepithermal mineralization precipitated from hydrocarbon–aqueous–chloride (Na–K ± Fe) fluid with salinity of 20.1–32.8 wt % NaCl eq. at 435–375°C and hydrocarbon–aqueous–chloride (Na–K ± Fe ± Ca ± Mg) fluid with salinity of 7.5–15.0 wt % NaCl eq. at 415–325°C, respectively. The epithermal mineral assemblages precipitated at ∼0.55 kbar from hydrocarbon–aqueous–chloride (Na–K ± Fe ± Ca ± Mg) fluid with salinity of 1.4–12.6 wt % NaCl eq. at 370–200°C. The latest low-temperature (240–190°С) and diluted (3.5–4.9 wt %) fluids are characterized by variations in Na and K chlorides; Fe²⁺, Fe³⁺, Ca, and Mg carbonates; and Na, K, and Mg sulfates. The S isotopic composition of the fluid of different mineral assemblages varies from –2.7 to +0.3‰ and suggest that they are derivatives of a single porphyry system. The δ¹⁸О values of the fluid of porphyry copper (7.4‰) and subepithermal (7.0‰) stages indicate its magmatic genesis, whereas those of the epithermal stage (from +1.2 to +7.2‰) are evident of mixing of magmatic fluid and meteoric waters (from +0.4 to +5.7‰). Our isotopic data, combined with mineralogical–geochemical peculiarities and formation conditions of ores, provide tracing the principles of the evolution of mineral assemblages, temperatures, composition, and fluid salinity at the Ak-Sug deposit upon the transition from porphyry copper to epithermal stage.

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东萨扬 Ak-Sug 斑岩铜金钼矿藏：贵金属矿化、PT 参数和含矿液成分

摘要 Ak-Sug 斑岩铜金钼矿床的矿石成矿过程分为三个阶段：1）斑岩型铜矿化，在石英-绿泥石和石英-绿泥石-绿帘石变质岩中形成简单的硫化物；2）亚热液型金-铋-碲-钯-石英矿化，在石英-绿泥石变质岩中形成；3）中硫化型金-银矿物组合，在绿帘石中形成硒化物、碲化物以及锑和砷硫化物。对石英和矿物热度（金银碲化物集合体）进行的流体包裹体研究（微测温、拉曼光谱）表明，斑岩铜矿和次热液矿化是从含盐量为 20.1-32.8 wt % 的氯化钠当量（435-375°C）和含盐量为 7.5-15.0 wt % 的氯化钠当量（415-325°C）的烃水氯化物（Na-K ± Fe ± Ca ± Mg）流体中析出。热液矿物集合体是在∼0.55千巴时，从盐度为1.4-12.6 wt % NaCl当量、温度为370-200°C的碳氢-水-氯化物（Na-K ± Fe ± Ca ± Mg）流体中沉淀出来的。最新的低温（240-190°С）和稀释（3.5-4.9 wt %）流体的特征是Na和K氯化物；Fe2+、Fe3+、Ca和Mg碳酸盐；以及Na、K和Mg硫酸盐的变化。不同矿物组合流体的 S 同位素组成在 -2.7 至 +0.3‰ 之间变化，表明它们是单一斑岩系统的衍生物。斑岩铜矿阶段（7.4‰）和次表热阶段（7.0‰）流体的δ18О值表明其岩浆成因，而表热阶段（从+1.2到+7.2‰）流体的δ18О值则表明岩浆流体和流星水（从+0.4到+5.7‰）的混合。我们的同位素数据与矿石的矿物学地球化学特征和形成条件相结合，为阿克苏格矿床的矿物组合、温度、成分和流体盐度从斑岩铜矿过渡到表生铜矿阶段的演变原理提供了依据。

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来源期刊

Geology of Ore Deposits 地学-地质学

CiteScore

1.10

自引率

14.30%

发文量

审稿时长

6-12 weeks

期刊介绍： Geology of Ore Deposits is a periodical covering the topic of metallic and nonmetallic mineral deposits, their formation conditions, and spatial and temporal distribution. The journal publishes original scientific articles and reviews on a wide range of problems in theoretical and applied geology. The journal focuses on the following problems: deep geological structure and geodynamic environment of ore formation; distribution pattern of metallogenic zones and mineral deposits; geology and formation environment of large and unique metallic and nonmetallic deposits; mineralogy of metallic and nonmetallic deposits; physicochemical and isotopic characteristics and geochemical environment of ore deposition; evolution of ore-forming systems; radiogeology and radioecology, economic problems in exploring, developing, and mining of ore commodities.