Major activities and provisional results of gold deposit forecasting in the eastern (Russian) part of Fennoscandian shield

The paper discusses the main gold metallogeny features within foreign Precambrian shields (excluding sedimentary-metamorphogene deposits of Au-rich conglomerates and magmatogene Au-rich Cu-Ni and PGE deposits) and regional features of the eastern Fennoscandian shield. Data on geological setting of Finnish gold deposits are summarized and analyzed. The paper briefly reviews gold prospecting knowledge within Karelian-Kola region and work results. The author compiled a digital model of gold-specific forecast-metallogenic map for the eastern Fennoscandian shield; based on this model, further prioritized exploration activities in Karelian-Kola region are proposed, potential for discovering medium-sized and major deposits of various formational and geological/economic types is forecasted.

Geology, petrography and mineralogy of explosive breccias of Sallanlatva, Kola Region

The Sallanlatva massif belongs to the group of Paleozoic alkaline-ultrabasic complexes wide spread in the Kola Region (the northwestern part of the Fennoscandian Shield). In the central part of this massif, the host ijolite and urtites contain calcite, ankerite, ankerite-dolomite and siderite carbonatites. The explosive processes that led to the formation of carbonatite breccias in the calcite and ankerite-dolomite carbonatites occurred in Sallanlatva massife in the last stages of the carbonatite magmatism. There are two types of explosive carbonatite breccias in the Sallanlatva massif: (1) glimmerite-calciocarbonatite breccias, and (2) siderite-dolomite breccias. Analysis of the mineral composition of fragments and matrix and the shape of fragments in breccias has shown that the first material to intrude into the host calcite and ankerite-dolomite carbonatites was calcite melt. After that, dolomite melt penetrated through the fracture zones, which resulted in the formation of siderite-dolomite breccias. The differences in the mineral composition of the breccia matrix suggest that the residual carbonatite melts originate from separate magma chambers. The chamber with calcite melt was located at great depth, and some captured glimmerite fragments were abraded during the melt upwelling. Silicate-dolomite melts lifted from a shallower depth; the captured fragments of siderite carbonatites retained their angular shape. Late hydrothermal processes yielded veins and caverns with Ba-Sr-P-S-Ti-REE mineralization in the breccias and host rocks.

Coulsonite FeV2O4—A Rare Vanadium Spinel Group Mineral in Metamorphosed Massive Sulfide Ores of the Kola Region, Russia

This work presents new data on a rare vanadium spinel group mineral, i.e., coulsonite FeV2O4 established in massive sulfide ores of the Bragino occurrence in the Kola region, Russia. Coulsonite in massive sulfide ores of the Bragino occurrence is one of the most common vanadium minerals. Three varieties of coulsonite were established based on its chemical composition, some physical properties, and mineral association: coulsonite-I, coulsonite-II, and coulsonite-III. Coulsonite-I forms octahedral crystal clusters of up to 500 µm, and has a uniformly high content of Cr2O3 (20–30 wt.%), ZnO (up to 4.5 wt.%), and MnO (2.8 wt.%), high microhardness (743 kg/mm2) and coefficient of reflection. Coulsonite-II was found in relics of quartz–albite veins in association with other vanadium minerals. Its features are a thin tabular shape and enrichment in TiO2 of up to 18 wt.%. Coulsonite-III is the most common variety in massive sulfide ores of the Bragino occurrence. Coulsonite-III forms octahedral crystals of up to 150 µm, crystal clusters, and intergrowths with V-bearing ilmenite, W-V-bearing rutile, Sc-V-bearing senaite, etc. Chemical composition of coulsonite-III is characterized by wide variation of the major compounds—Fe, V, Cr. In some crystals of coulsonite-III, relics of chromite are observed. The microhardness of coulsonite-III is 577 kg/mm2, the reflection coefficient changes in relation to iron, vanadium, and chromium content.

Obtaining refractory materials from chromite raw materials of Karelia and physical and chemical processes in their service

The mineral and chemical compositions of the chromite raw materials of the Karelian-Kola region are studied, the physical and chemical processes for the production of refractory materials from chromite concentrate are established, the phase and structure formation during drying, firing and during service are determined. The dependence of some properties of refractories on their material, grain and phase compositions has been established.