Chalcophile mineralization in hematite veins of the Cape Korabl’ amethyst deposit (Kola peninsula): sequences for the formation of Fe (Cu,Ag)-S-O parageneses

Abstract

Introduction: the article presents data on the unusual Fe-Cu-Ag-Sb-S-O paragenesis of hematite veins of the Cape Korabl’ amethyst deposit. These bodies can be attributed to a series of fluorite-barite-quartz-carbonate veins, widespread in the northern side of the Kandalaksha graben. The study of parageneses of Fe-S-O and Fe-Cu-S-O systems is of great importance, since their behavior determines many patterns of metal distribution in deposits.

Methodology: to study the composition of minerals, a scanning electron microscope Zeiss EVO-25 with an energy-dispersive analyzer Aztec UltimMax-100 (Center for Common Use of the KSC RAS, Apatity) was used.

Results and discussions: chalcophile mineralization is represented by sulfides (galena, cinnabar, chalcocite group), silver sulfosalts (argentopolybasite, pyrargyrite) and sulfoarsenides (arsenopyrite). The minerals are closely associated with hydrothermal lamellar hematite. Mineral parageneses indicate low-temperature (<200°C) conditions of their formation. The authors proposed a mechanism for the crystallization of this mineralization during changes in the redox potential in the Fe-S-O system.

Conclusion: the source of silver in hydrothermal veins could be authigenic pore hematite from the host arkosic sandstones of the Tersky suite, which, under the influence of hydrothermal solutions, was dissolved and redeposited in the form of almost stoichiometrically pure hematite with the release of silver into the hydrothermal solution.