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Location: 8 km NE from Dunkwa-On-Offin, Ghana
17 Jungle Avenue East LegonAccraGhana
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Within the Birimian and Tarkwaian lithologies of Ghana there are three major types of gold mineralisation: Type 1: Reef, Vein or Lode gold deposits associated with regional scaled shear zones, such as the Obuasi gold mine to the north of Kubi. Type 2: Granitoid-hosted, mesothermal gold mineralisation, such as Ayanfuri gold mine to the south west of Kubi. Type 3: Auriferous quartz-pebble conglomerate deposits such as at Tarkwa and recent alluvial gold concentrations. The Kubi deposit mineralisation style is Type 1: Birimian aged, shear hosted, reef, vein or lode gold deposit.Mineralisation The mineralisation occurs in a 1.0 to 15.0 metre thick garnetiferous horizon within Birimian metasediments. This garnetiferous horizon contains fine grained gold associated with minor (5-15%) pyrite, arsenopyrite and pyrrhotite as well as some coarser gold which is associated with relatively narrow quartz veins. Some mineralisation occurs in quartz veins and veinlets that cross-cut the Birimian-Tarkwaian contact, outside of the main garnetiferous horizon.SEM (scanning electron microscope) and polished section studies have observed gold and associated sulphides such as pyrrhotite, pyrite, arsenopyrite and occasionally chalcopyrite, rimming and often replacing the included garnet blasts. The garnets are often highly tectonised with native gold, often coarse, and with sulphides coating the micro-fractures.The grades exhibited on the Birimian-Tarkwaian contact (the “Contact” zone) are variable but generally low in tenor. The mineralisation is associated with moderate silicification and quartz veining. The predominant sulphides are pyrite and arsenopyrite.The footwall and hanging wall zones are comparable to the traditional styles of Ashanti lode gold deposits, with the exception that the gold is free milling and not refractory - predominantly quartz vein hosted within faults and shears, with attendant pyrite and arsenopyrite haloes. Grades tend to be moderate to low, but continuity exists and potential high-grade pods are observed over restricted strike lengths.Gold is native, is often coarse and nuggetty, hosted within quartz veins and microfractures in the host sulphides or alteration minerals. It is not intimately bound within the lattice of the sulphides. Kubi mineralisation is “free milling”, not refractory, hence 95% expected recoveries. Whilst higher gold grades are often associated with quartz veins and zones of appreciable silica flooding, gold mineralisation within the host selvage proximal to the fracturing is also of economic tenor.
