Gomoa East Project

The Proposed Sikakoku concession sits within what is generally referred to as the Cape Coast Basin. The Lower Proterozoic rocks of southwestern Ghana compromise turbiditic sedimentary rocks and mafic-to-intermediate volcanic/hypabyssal rocks of the Birimian Supergroup, fluvial molasse sediments of the Tarkwaian Group and various granitoid intrusions as well as lithium bearing pegmatites. Turbiditic sedimentary rocks and mafic-to-intermediate volcanic rocks of the Birimian Supergroup constitute separate NE-striking belts. Felsic volcanic rocks and ultramafic rocks form small components of the volcanic belts. Tarkwaian Group sedimentary rocks include both the gold-bearing Banket and the unmineralized Kawere Series conglomerates, various fluvial sandstone units and minor shales. The Tarkwaian Group is commonly found in close proximity to Birimian volcanic rocks either as unconformable stratigraphic contacts or as imbricated fault-bounded slices. The Birimian hosts the world class Obuasi gold deposit of the Ashanti Goldfields Company; it also hosts the Prestea, Bogoso, Ayanfuri, Amansie, Konongo and Yamfo gold deposits among others. Gold deposits in the Tarkwaian include Abosso, Tarkwa, Iduapriem and Akyempim.

Recent radiometric dating has led to the new interpretation of the chronological history of SW Ghana. New radiometric dating of the Birimian volcanics indicates that the belts are ~50-60Ma older than Birimian sedimentary belts. (Leube et al. 1990; Taylor et al. 1992; Davis et al. 1994; Oberthur et al. 1998). Previously these volcanic packages within the Birimian were referred to as upper Birimian (considered to be younger than the Birimian sediments) due to their apparent stratigraphic location. The volcanic Birimian packages are most likely the base of the Birimian Group and have been thrust faulted into their current position, overlying the younger Birimian Sediments. The Tarkwaian Group has previously been interpreted to be much younger than the Birimian (Junner 1935).Tarkwaian Banket Formation Conglomerates have previously been interpreted as being generated from the uplift and weathering of the Birimian quartz veins and gold systems. However, recent radiometric dating indicates that the Tarkwaian Group sediments disposition commenced a few million years of the disposition of Birimian sedimentary rocks (Allibone et al. 1998). Structural analysis of the Birimian sedimentary rocks and basal conglomerates of the Tarkwaian Group indicate that they were deformed together (Milesi et al. 1991; Eisenlohr 1992).

New radiometric dates for Western Ghana basement rocks (Leube et al. 1990; Taylor et al. 1992; Davis et al.1994; Oberthur et al. 1998) indicate that they developed during 2 separate orogenic Cycles. The first orogenic cycles, the "Eburnean 1", between 2240--2150 Ma, involved the eruption of Birimian volcanic rocks, intrusion of the granitoid rocks which cut the earlier volcanic rocks, and an episode of metamorphism , uplift and erosion. The second major orogeny, the "Eburnean 2", between 2130--2088Ma, deformed and metamorphosed (greenschist facies) both the Birimian and Tarkwaian rock packages as well as generated intrusions of granitoids into rocks (Allibone et al. 1998). The regional pervasive NE-striking structural grain of Birimian andTarkwaaian Group rocks was established during the "Eburnean 2" orogeny. Birimian sedimentary and Tarkwaian Group rocks were deposited during the hiatus of the deformation between the two orogenies (~2150-2130Ma). Southwest Ghana's history is characterized by NW-SE compressional shortening that deformed Birimian, Tarkwaian and early intrusive rocks.

Compression of the Birimian and Tarkwaian rocks gave rise to a thrusted and orogenic belt. Thrust faulting appear to have occurred along the Birimian volcanic-sedimentary contact as is evident by the imbricate slices of volcanics within the Central Structural Corridor.