Summary:
Kokoseb lies within the Northern Central Zone of the Pan-African Damaran Orogenic Belt around 15km south of the Otjihorongo Thrust, which separates the Northern Zone from the Northern Central Zone, and about 30km west of the NNE trending Welwitschia Lineament. The project area is underlain by metasediments of the Arandis, Karibib and Kuiseb Formations of the Swakop Group.
The Arandis Formation consists of alternating schists, calc-silicates (commonly scapolitic) and marble units which core two prominent domal features in the central portions of the Okombahe licence with the easternmost of these domes named the Otjongeama Dome. The Arandis Formation is overlain by the Karibib Formation which is dominated by impure marbles and lesser calc-silicates and is capped by the calcitic, graphite bearing marbles of the Arises River Member. The metasediments of the overlying Kuiseb Formation consist mainly of quartz/plagioclase/K-feldspar/biotite schist and biotite schist with minor quartzites and calc-silicates. The schists appear to have undergone local weak partial melting.
Along the southern edge of the Kokoseb Gold Prospect, the domal features cored by Arandis and Karibib Formation rocks are thrusted over the Kuiseb Formation, to the north, along the regional southern thrust, resulting in a prominent marble ridge that marks the southern boundary of known mineralisation.
Within the Kokoseb area, the Kuiseb schist forms a domal feature cored by a post tectonic leucogranite, the “Central Granite Pluton”, which consists predominantly of medium grained quartz, K-feldspar and plagioclase, with accessory biotite, muscovite, magnetite, garnet and tourmaline. Granite dykes, granitic veinlets and pegmatites cross cutting the Kuiseb schist represent the same granite phase or later granitic phases. Gold mineralisation wraps around this pluton in a roughly arcuate form but seems best developed along the western and northern margins of the Central Pluton. A coarse grained, pre-syn tectonic, porphyritic-feldspar granite encloses the mineralised schists in the west, east and northeast. The schist units consist of poorly foliated, dark grey, quartz/plagioclase/Kfeldspar rich, biotite bearing, schist and black, better foliated biotite schists.
Mineralisation
Gold mineralisation is found in the Kuiseb Formation metasediments which are extensively intruded by both late syn-tectonic and post tectonic granites, and minor N-S to NNE-SSW trending mafic dykes. There is generally moderate to good rock exposure throughout the licence area though the Kuiseb formation tends to only sub-outcrop and is commonly covered by thin soil, colluvium or pisolitic calcrete up to 2m thick.
Gold mineralisation, present as native gold grains and lesser silver bearing gold grains, is spatially associated with sulphides dominated by pyrrhotite, löllingite and arsenopyrite in order of abundance. Sulphides manifest as foliation-controlled blebs, stringers and disseminations and löllingite is always spatially associated with arsenopyrite and pyrrhotite where a retrograde reaction rim of arsenopyrite is always developed at the contact between pyrrhotite and löllingite. This contact zone between löllingite and arsenopyrite is typically where gold grains are developed, though they can also occur as partial inclusions within löllingite and rarely within pyrrhotite. Gold is commonly associated with bismuthinite and native Bi mineralisation.
Pyrite is the most common sulphide but does not show any direct association with gold mineralisation.
Mineralisation generally outcrops, with locally a maximum of 1 to 2 m of barren superficial material. Weathering extends to an average of around 32 m depth.
Dimensions
• The mineralised domains have a combined strike length of around 6.8 km, with average widths of around 70 m, 100 m, 70 m, and 45 m for the south, northwest, north and east domains respectively;
• The pit shell extends over around 5.8 km of strike and reaches a maximum depth of around 480 m;
• Mineral Resources extend from surfaced to 480 m depth with around 75% from depths of less than 230m and 90% from shallower than 300 m.