Belorechenskoe

Geological Context

The Belorechenskoye deposit is situated in the Maykopsky District of Adygea, a republic in southern Russia. Specifically, it is located in the upper reaches of the small river Syuk, a right tributary of the Belaya river, 60 km south of the city of Maikop. The deposit is classified as a "five-metal" formation hydrothermal uranium(-nickel) deposit with baryte.

The geological setting consists of hydrothermal veins in serpentinites. This indicates a complex geological history involving ultramafic rock alteration and subsequent hydrothermal activity. The serpentinites provide a suitable host rock for the diverse mineral assemblage found at the site.

Mineral Paragenesis and Sequencing

The Belorechenskoye deposit exhibits a complex paragenetic sequence, reflecting multiple stages of mineralisation:

1. Primary mineralisation: This phase involved the deposition of sulphides and arsenides, including pyrite, chalcopyrite, arsenopyrite, nickeline, and millerite.
2. Uranium mineralisation: The presence of uraninite (pitchblende variety) and coffinite indicates a significant uranium deposition phase.
3. Oxidation and alteration: Extensive oxidation and alteration processes led to the formation of numerous secondary minerals, including:
   • Copper secondaries: azurite, malachite, brochantite, antlerite
   • Lead secondaries: cerussite, anglesite
   • Arsenic secondaries: scorodite, symplesite, parasymplesite
   • Uranium secondaries: autunite, metazeunerite, nováčekite
4. Late-stage mineralisation: The presence of carbonates (calcite, aragonite) and sulphates (gypsum, baryte) indicates late-stage deposition from circulating groundwater.

Type Locality Minerals

The Belorechenskoye deposit is the type locality for two mineral species:

1. Dymkovite (TL): A nickel-uranium-arsenic mineral with the formula Ni(UO₂)₂(As³⁺O₃)₂·7H₂O. It is described as a seelite-related arsenite.
2. Rauchite (TL): Another nickel-uranium-arsenic mineral, belonging to the autunite group, with the formula Ni(UO₂)₂(AsO₄)₂·10H₂O.

These type locality minerals underscore the unique geochemical environment of the Belorechenskoye deposit, particularly its enrichment in nickel, uranium, and arsenic.

Associated Minerals

The deposit hosts an impressive array of 87 distinct mineral species, including:

• Sulphides: Pyrite, chalcopyrite, galena, sphalerite
• Arsenides: Arsenopyrite, nickeline, rammelsbergite
• Uranium minerals: Uraninite (pitchblende), autunite, metazeunerite
• Nickel minerals: Millerite, annabergite, gersdorffite
• Copper secondaries: Azurite, malachite, brochantite
• Arsenic minerals: Arsenic, arsenolite, scorodite
• Carbonates: Calcite, aragonite, dolomite
• Sulphates: Gypsum, baryte, jarosite

This diverse assemblage reflects the complex paragenesis involving primary sulphide-arsenide mineralisation, uranium deposition, and extensive supergene alteration.

Conclusion

The Belorechenskoye deposit in Adygea, Russia, represents a mineralogically significant locality with a complex paragenetic history. Its importance is underscored by the presence of two type locality minerals, dymkovite and rauchite, both of which are nickel-uranium-arsenic species. The diverse mineral assemblage, comprising 87 distinct species, reflects a multistage mineralisation process involving primary sulphide-arsenide deposition, uranium mineralisation, and extensive supergene alteration. The deposit's classification as a "five-metal" formation hydrothermal uranium(-nickel) deposit with baryte, hosted in serpentinites, provides crucial context for understanding the formation of this unique mineral assemblage.