Sulfide Mineralization of Carbonate–Silicate Veins in Early Proterozoic Metabasites of North Karelia: Mineral Assemblages, Mineral Forms of Silver, and Fluid Inclusions

IF 0.8 4区地球科学 Q3 GEOLOGY

Geology of Ore Deposits Pub Date : 2023-12-01 DOI:10.1134/s1075701523060107

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Abstract

The work presents the first data on sulfide mineralization in carbonate–silicate veins, which are widespread on the islands and coast of the White Sea (North Karelia), associating with Early Proterozoic metamorphosed gabbroid bodies. The veins with Fe–Cu sulfide mineralization up to ore occurrences are localized within metabasite bodies and along their contacts with host gneisses. During the study of the mineral composition of the veins, the main assemblages of sulfide minerals were identified: chalcopyrite –bornite ± chlorite ± selenides and Pb–Ag tellurides (B1); digenite–bornite ± selenides and Pb, Ag, and Pd tellurides (B2); pyrite–bornite ± chalcopyrite (B3); marcasite–pyrite–bornite–chalcopyrite (B4); and siegenite–chalcopyrite ± acanthite ± chlorargyrite. The development of sulfide associations, as well as quartz–chlorite aggregates, was related to the late stage of vein formation. Inductively coupled plasma and laser ablation mass spectrometry analyses showed that bornite from association B1 has the highest silver content (up to 675 ppm) and, in terms of Ag, Se, and Bi contents, is closest to bornite from low-temperature epithermal, skarn, and high-temperature vein deposits. In general, bornite is the main Ag carrier in the studied associations, while digenite containing up to 1000 ppm Ag, as well as discrete silver minerals (selenides, tellurides, acanthite, and chlorargyrite), occur in subordinate quantities. Fluid inclusions in quartz from sulfide associations, as well as from a sulfide-free carbonate–silicate vein, were studied by cryo- and thermometric methods. It is established that mineralization at the late stages of vein formation was related to heterogeneous CO₂–H₂O–NaCl metamorphic fluid. Carbon dioxide fluid inclusions were captured by vein quartz at temperature of 253–314°C and pressure of 2 ± 1 kbar. Water–salt inclusions were captured in a wider temperature range of 100–500°С. The highest temperature fluid inclusions with temperatures of homogenization >300°С are characteristic of quartz veinlets of the siegenite–chalcopyrite association with Ag sulfide and chlorargyrite.

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北卡累利阿早新生代元基岩中碳酸盐-硅酸盐矿脉的硫化物成矿作用：矿物组合、银的矿物形态和流体包裹体

摘要该研究首次提出了有关碳酸盐-硅酸盐矿脉硫化物矿化的数据，这些矿脉广泛分布于白海（北卡累利阿）的岛屿和海岸，与早新生代变质辉长岩体有关。硫化铁-铜矿化的矿脉直至矿点都位于偏闪长岩体内部，并沿着其与主片麻岩的接触面分布。在对矿脉矿物成分的研究中，确定了硫化物矿物的主要组合：黄铜矿-黄铁矿±绿泥石±硒化物和铅银碲化物（B1）；地开石-黄铁矿±硒化物和铅、银、钯碲化物（B2）；黄铁矿-黄铁矿±黄铜矿（B3）；黄铁矿-黄铁矿-黄铜矿（B4）；以及锡安黄铜矿±黄铁矿±绿泥石。硫化物联合体以及石英-绿泥石集合体的形成与矿脉形成的后期阶段有关。电感耦合等离子体和激光烧蚀质谱分析表明，伴生体 B1 中的波长石含银量最高（高达 675 ppm），就银、硒和铋含量而言，与低温热液矿床、矽卡岩矿床和高温矿脉矿床中的波长石最为接近。一般来说，在所研究的关联中，波长石是主要的银载体，而含银量高达 1000 ppm 的黝帘石以及离散银矿物（硒化物、碲化物、黄铁矿和绿帘石）则处于次要地位。通过低温和测温方法研究了硫化物伴生的石英中的流体包裹体，以及无硫化物碳酸盐-硅酸盐矿脉中的流体包裹体。结果表明，矿脉形成后期的矿化与异质二氧化碳-H2O-NaCl 变质流体有关。在温度为 253-314°C 和压力为 2 ± 1 千巴的条件下，矿脉石英捕获了二氧化碳流体包裹体。水盐包裹体的捕获温度范围较宽，为 100-500°С。温度最高的流体包裹体的均匀化温度为 300°С，是锡铁矿-黄铜矿与硫化银和绿泥石结合的石英脉的特征。

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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.