The Gruvaktiebolaget Viscaria holds a 100% interest in the Viscaria Project through its wholly owned subsidiary, Viscaria Kiruna AB, which serves as the operating entity responsible for implementing, licensing, and advancing the project.
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Summary:
The Viscaria Project is situated within the Kiruna Greenstone Group in the Kiruna mining district. This district comprises a Paleoproterozoic (2.5 Ga–1.8 Ga) supracrustal sequence spanning around 150 km by 20 km and hosts several Kiruna-type Iron Oxide Apatite (IOA) deposits and significant copper deposits that are located within close proximity to each other, the largest being Kiirunavaara-Viscaria and Malmberget-Aitik-Nautanen.
The Viscaria Formation, with its 3 major ore zones (A, B and D), hosted in the Kiruna Greenstone Group, is comprised of a thick succession of volcanoclastic and sedimentary rocks, bounded by basalts in both the footwall and hanging wall. Metamorphism reached upper greenschist to lower amphibolite facies and sedimentary and volcanic textures are generally well preserved. Regional scale structures cross the Viscaria project on the western side running N-S and on the eastern side trending NW-SE.
Only small offsets in the stratigraphy are identified, and at depth in the D Zone structural investigations are on-going in identifying a possible thrust fault that could lead to a thinning and thickening and potentially stacked ore bodies. The defined ore bodies, the A, B and D zones, are emplaced at different stratigraphic levels and generally stratabound with a NE-SW strike and 60-70° dip towards the south-east. Many areas adjacent to and between the known A, B and D zones host copper sulfide mineralisation, including the recently discovered ABBA zone, thus opening potential for additional future resources to be found at different stratigraphic levels.
Key hydrothermal alteration in Viscaria consists of an early district-scale sodic alteration (CaNa), followed by iron-potassic (Fe-K) and calcic-iron-magnesium (Ca-Fe-Mg) alteration. The Fe-K metasomatism is indicated by biotite formation and most intense in the direct hangingwall of copper mineralisation. Amphibole and magnetite formation as a result of Ca-Fe-Mg alteration has the closest relation to the copper magnetite ore bodies and is found in immediate vicinity and with replacement textures within the richest copper mineralisation’s.
The ore zones widths vary between 3-25 meters, whereas 8-12 meters is the most common width for A, B and D Zone. These zones with their typical NE-SW strike and steeply (60-70°) dipping orientation towards the SE make for efficient underground extraction through long-hole open stoping.
Mineralogy of the ore zones varies across A, B and D Zone with their respective host rocks as well as the alteration style. Copper is almost exclusively hosted in chalcopyrite, with some exceptions where bornite has been identified in the latest areas of exploration, particularly in the D Zone.
Deposit type
The Viscaria deposit was classified in the 1980s to be a syngenetic volcanogenic massive sulfide system with exhalative characteristics. Especially the A Zone with its blanket shape of mineralization of magnetite and sulfides and their association with black shales may favour a syngenetic model. Extensive drilling in 2019–2025 and additional scientific studies suggest that Viscaria formed within a long-lived epigenetic and fault related hydrothermal system. Most economic parts of the deposit have a stratabound characteristic, where copper sulfide deposition was triggered by changes from an oxidized to a reduced environment, this includes the A, B and D Zone ore bodies. The main copper mineralization is interpreted to have taken place before the major E-W compressional event that tilted the whole regional geological units into its current position.
The interpretation of Viscaria as a manto-style iron oxide-copper-gold (IOCG) deposit, analogous to the Candelaria deposit in Chile, supports the concept of making further discoveries at depth, along strike and at different stratigraphic positions. The blind discovery of the ABBA zone highlights the potential to find new copper-rich horizons, even where there is no clear surface expression. The system appears better developed at depth and the prospective host units for copper mineralisation are not limited to the classical A, B and D zones.