The Baniaka iron ore Project is 100% owned by Ressources Minières d’Afrique Centrale Gabon SA (Reminac), a wholly owned subsidiary of Genmin Limited.
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Summary:
Deposit Type
Baniaka is located within the Chaillu Massif, where the Archaean basement comprises granitoids and gneisses with greenstone belts consisting of metasediments and metavolcanics including amphibolites, quartzites, micaceous schists and banded iron formation (BIF).
Iron mineralisation at Baniaka is associated with an eluvial and/or colluvial accumulation of iron-rich fragments derived from erosion of the underlying iron-enriched BIF units (DID), oxide BIF (SO and Intact Oxide), and primary BIF (Primary)). The DID and Oxide BIF are enriched in iron compared to the Primary, with in-situ grades of 40–50% Fe and 40–45% Fe, respectively, and 33% Fe for the Primary.
The BIF units are hosted in, and concordant with, felsic schists and para-gneisses with lesser amphibolite occurrences. Primary iron mineralisation is present as magnetite. The BIF units, wall rocks and early granitoids have been metamorphosed and have undergone multiple phases of deformation. Two (2) early phases of deformation show plunging, tight to isoclinal folds, boudinage structures and shearing. Two (2) later phases of deformation comprising open to gentle folding are also recognised. The metamorphic grade is Lower Amphibolite Facies.
The fault network of the PFS Prospects is well defined and pervasive, however faults have minor offsets of less than 15m. Younger brittle faulting, possibly related to the formation of the Francevillian basin to the north, and late undeformed dolerite dykes cross-cut the BIF units and wall rocks.
The Project area has been subject to intense tropical weathering, resulting in the progressive leaching of silica from fresh rock, which in turn leads to volumetric reduction and enrichment or accumulation of minerals that are stable and resistant to weathering processes. Ferro-silicate minerals (amphiboles and phyllosilicates) have been progressively oxidised to residual clay mineral assemblages. Primary magnetite associated with the BIF units has been progressively oxidised to maghemite, martite and hematite with subordinate goethite as proximity to ground surface, and intensity of weathering increases.
The combined effects of volumetric reduction of the in-situ BIF coupled with progressive oxidation of magnetite to hematite has led to the formation of a series of weathering zones each with distinct characteristics, that are enriched in iron and depleted in gangue minerals and impurities to various extents. These weathering zones are closely related to the styles of iron mineralisation encountered at the Project.
Mineralization
Four (4) styles of iron mineralisation are noted at Baniaka, each typically found in layers that are sub-parallel to dominant topographic features and constrained by the up-dip projection of the Primary BIF.
Detrital Iron Deposits (DID)
The DID comprises a blanket of iron-rich, BIF-derived gravels and their cemented duricrust equivalents. The DID results from the oxidation and disaggregation of the underlying BIF with limited transportation and typically directly overlie or immediately flank the BIF and are interpreted as a residuum. The DID is predominantly comprised of particles of enriched BIF that range in size from coarse sand (0.5–1mm) to pebbles (4–65mm) with minor coarser and finer fractions. DID is characterised by a high Lump fraction (40–50% >6.3mm) and low magnetic susceptibility. DID thickness ranges from 1 to 16m, with the thickest accumulations occurring at Bandjougoy. DID is typically flanked by iron-poor, non-BIF derived gravels termed lateritic colluvium. The mixing zone between DID and lateritic colluvium is known as Hybrid (HYB). The DID mineralisation does spread laterally beyond the surface projection of the underlying BIF due to lateral dispersion associated with weathering.
Soft Oxide Mineralisation
Oxide material directly underlies the DID and corresponds to the in-situ weathered portion of the BIF. Oxide mineralisation is therefore effectively constrained by the hanging wall and footwall contacts of the BIF. The Oxide extends from the base of the DID to depths of up to 70m below the natural surface. The upper portion of the Oxide is a soft, sandy to friable hematite-dominant weathered rock that has been enriched in iron by both accumulation and supergene enrichment, and has low magnetic susceptibility. The SO occurs with thicknesses from 15 to 45m, averaging approximately 30m.
Intact Oxide Mineralisation
The lower portion of the Oxide is referred to as Intact Oxide, which is a texturally preserved, banded to massive, weathered rock that features some preserved silica and ferro-silicates, with iron mineralisation present as hematite-martite-maghemite. The Intact Oxide is typically thinner than the SO, ranging from 5 to 25m thick, averaging 15m thick, and has moderate magnetic susceptibility.
Primary Mineralisation
Underlying the Oxide mineralisation, the Primary BIF is comprised of fresh BIF with a thin transitional zone at the base of the Intact Oxide, where magnetic susceptibility is slightly less than the Primary BIF. The Primary BIF is characterised by strong to very strong magnetic susceptibility, with magnetite being the dominant iron oxide. Gangue minerals are silica present as quartz, and ferro-silicate minerals. The true thickness of the BIF ranges from 50m up to 250m at Bandjougoy, with an average thickness of approximately 150m.