On July 9, 2024, Millennial Potash Corp. ("MLP", "Millennial" or the "Company") earned a total 70% interest in the shares of Equatorial Potash Pty. Ltd. which, through its Gabon subsidiary Mayumba Potasse SARL, holds 100% of the Banio Potash Project.
Millennial Potash Corp. (Millennial or the Company) entered into an option agreement with Equatorial Potash Pty Limited (Equatorial Potash) to acquire up to a 100% interest in the company.
Millennial Potash is acquiring up to 100% of the Banio Potash Project in Gabon through staged payments and exploration work.
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Summary:
The Banio Project is predominantly located within the Congo Basin. The Congo Basin is part of the equatorial West African Aptian salt basin that extends from Cameroon to Namibia and includes the Douala, Kribi-Campo, Rio Muni, Gabon, Congo, Kwanza, Benguela, and Namibe Basins.
Deposit Type
The deposits of the Banio Project are classified as evaporites within the Congo Basin, part of the larger Aptian salt basin that stretches across equatorial West Africa. They can be considered as primary sedimentary rocks.
The Congo Basin evaporite cycles as well as individual potash seams within the cycles can be correlated over large areas of the basin. The continuity of the potash seams is comparable with the potash seams in the Elk Point basin in Saskatchewan, Canada. Mineable potash seams in the Congo Basin sequence sum up to a potential economic thickness of >100 m. This is larger than the Saskatchewan deposits mined using solution mining (combined thickness of 30 m to 50 m) and the conventionally mined potash in the Upper Kama basin in Russia.
Carnallite was the main potash mineral at the start of potash fertiliser production in Germany in 1865 and is still used for the production of KCl fertiliser at two locations. It is mined using solution mining techniques where the deposit has a thickness of between 15 m and 35 m.
The Congo Basin is part of the passive continental margin of West Africa that formed during the Late Jurassic to Early Cretaceous breakup of Gondwana. A thick sequence of Lower Cretaceous to Miocene continental and marine clastic and evaporite sediments fills the Congo Basin (Pedley et al., 2016), and to the east, it is bordered by Pre-Cambrian Mayombe igneous and metamorphic basement rocks (de Ruiter, 1979).
Evaporitic salt deposition occurred during the late Aptian (113 Ma to 125 Ma ± 1 Ma) throughout the basin in a large steadily and relatively evenly subsiding sub-sea-level basin. The basin was fed by seepage inflow from the proto-Atlantic (Pedley et al., 2016). The Walvis Ridge, formed by the migrating Tristan da Cunha hot spot, restricted circulation from the open marine ocean to the south, and the Cameroon Fracture Zone limited the northern extent of the Aptian salt basin (Brownfield and Charpentier, 2006).
Within the Rock Salt Formation of the Congo Basin, ten sedimentary evaporite cycles (I to X) have been identified whose mineralogy are consistent with typical brine evolution models (Pedley et al., 2016). The original subdivision of the evaporite cycles was made by the MDPA geologists (e.g. Schlund & Vandenbroucke, 1960). These cycles are consistent with rapid periods of sea water inflow and protracted evaporation resulting in the precipitation of salts. A cycle, from bottom to top, generally consists of a basal shale or clay layer, a layer of rock salt (halite), a mixture of halite and carnallitite, and sometimes an end member of bischofite or tachyhydrite (de Ruiter, 1979). The potash seams are predominantly carnallitite except in certain areas where it has been replaced by sylvinite (Pedley et al., 2016).
The replacement of carnallitite by sylvinite principally occurs along the flanks of gentle antiformal features and within the upper 50 m to 100 m of the evaporite sequence (Pedley et al., 2016). Low tensional strain associated with the antiforms may have caused fracturing in the Anhydrite Formation cap allowing the gradual seepage of brines into the evaporite sequence from overlying aquifers. The interaction of brines resulted in the dissolution of carnallite leading to the formation of secondary halite, sylvite, and a chloride rich brine. The grade of the sylvinite is directly proportional to the grade of the precursor carnallitite.
The potash seams vary in thickness from cm-scale up to 20 m thick and are separated by rock salt with clay layers that vary in thickness from cm-scale to over 100 m thick (Rauche & van der Klauw, 2015). Rocks with interlayered potash and rock salt where the rock salt dominated layers are <1 m are grouped together as a single potash seam. The boundaries of these inhomogeneous seams are not clearly fixed. Potash seams are named by the cycle within which the seam is found followed by the seam number within that cycle, sequenced from the base upwards.
Mineralisation
The down hole geophysical logs allowed the identification of overburden, clay, and anhydrite dominated rocks. Within the evaporite sequence it was used to distinguish between rock salt layers, carnallitite seams, interlayered rock salt and carnallitite, tachyhydrite layers, and interlayered carnallitite and tachyhydrite.
The potash was originally deposited as carnallite seams and are present within three fault blocks separated by two NE-SW trending near vertical strike slip or transform faults. Within each block the carnallite seams were originally deposited as near horizontal layers which now shallowly dip towards the SW.
The horizontal seams after deposition have been offset by NW-SE trending normal faults (locally reversed) with a dip in the range of 65° to 70°. The orientation and offset of the faults were interpreted from the seismic exploration data. The carnallite seams can be offset along these faults, but all seams present in the relative upthrown block are also present in the downthrown block. If a drill hole on a downthrown block shows the presence of stratigraphically higher seams, these are only extended over a relative upthrown block, when there is independent information about the magnitude of the vertical movement along the fault structure.
The transformation of the carnallite deposit to a sylvite deposit, requires fluid infiltration and only takes place in uplifted blocks (Pedley et al., 2016). Therefore, seams with sylvite mineralisation are not extended over faults in downthrown blocks. These seams are probably present as carnallite seams, but are only modelled if they have been shown to be present in a drill hole in a downthrown block.