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Aleksey V. Berezin
Aleksey V. Berezin
Senior Research Scientist, Ph.D.
Institute of Precambrian Geology and Geochronology Russian Academy of Sciences
Saint Petersbur Russia
Senior Research Scientist, Ph.D.
Institute of Precambrian Geology and Geochronology Russian Academy of Sciences
Saint Petersbur
Russia
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  • Date submitted
    2020-05-14
  • Date accepted
    2020-10-05
  • Date published
    2020-12-02

Fahlbands of the Keret archipelago, White Sea: the composition of rocks and minerals, ore mineralization

This paper presents a complex mineralogical and geochemical characteristic (based on SEM-EDS, ICP-MS analysis) of the fahlband rocks of the Kiv-Guba-Kartesh occurrence within the White Sea mobile belt (WSMB ). The term “fahlband” first appeared in the silver mines of Kongsberg in the 17th century. Now fahlbands are interlayers or lenses with sulfide impregnation, located in the host, usually metamorphic rock. The level of sulfide content in the rock exceed the typical accessory values, but at the same time be insufficient for massive ores . Fahlbands are weathered in a different way than the host rocks, so they are easily distinguished in outcrops due to their rusty-brown color. The studied rocks are amphibolites, differing from each other in garnet content and silicification degree. Ore mineralization is represented mainly by pyrrhotite and pyrite, and pyrrhotite grains are often replaced along the periphery by iron oxides and hydroxides, followed by pyrite overgrowth. At the same time, the rock contains practically unaltered pyrrhotite grains of irregular shape with fine exsolution structures composed of pentlandite, and individual pyrite grains with an increased Ni content (up to 5.4 wt.%). A relatively common mineral is chalcopyrite, which forms small grains, often trapped by pyrrhotite. We have also found single submicron sobolevskite and hedleyite grains. The REE composition of the fahlband rocks suggests that they are related to Archean metabasalts of the Seryakskaya and Loukhsko-Pisemskaya structures of the WSMB, rather than with metagabbroids and metaultrabasites common in the study area.

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Laysan I. Salimgaraeva, Sergey G. Skublov, Aleksey V. Berezin, Olga L. Galankina (2020) Fahlbands of the Keret archipelago, White Sea: the composition of rocks and minerals, ore mineralization. Journal of Mining Institute. Vol 245. p. 513-521. DOI: 10.31897/PMI.2020.5.2