Summary:
Goldex property
The Goldex property is located near the southern boundary of the Archean-age (2.7 billion years old) Abitibi Subprovince, a typical granitegreenstone terrane located within the Superior Province of the Canadian Shield. The southern contact of the Abitibi Subprovince with the Pontiac Subprovince is marked by the east-southeast trending Cadillac-Larder Lake fault zone, the most important regional structural feature. The Goldex deposit is hosted within a quartz diorite sill, the "Goldex Granodiorite", located in a succession of mafic to ultramafic volcanic rocks that are all generally oriented west-northwest. The satellite Goldex deposit known as the South Zone is hosted within the volcanic rocks (basalts, gabbro, komatiite) located south of the Goldex main deposit.
The M Zone has an approximate length of 440 metres, a height of 350 metres and a thickness of 130 metres. The E Zone, adjacent to the eastern end of the GEZ, has an approximate length of 250 metres, a height of 290 metres and a thickness of 130 metres. The Deep Zone (including the Deep 1 Zone and the Deep Zone Extension) is the continuity of the GEZ mineralization at depth. For safety purposes, a 90-metre thick pillar has been left below the GEZ, so that mining of the Deep Zone starts at 850 metres below surface, and extends to 1,800 metres below surface. It appears to have an approximate strike length of 350 metres, a height of 950 metres and thickness of 120 metres.
Mineralization
The primary gold mineralization type at Goldex corresponds to the classical quartz-tourmaline vein lode-gold deposit type. The gold-bearing quartztourmaline pyrite veins and vein stockwork, hosted within a quartz-diorite dyke, are the result of a strong structural control, related to ductile shearing and brittle faulting. The most significant structure directly related to mineralization is a discrete shear zone, named the Goldex Mylonite, which is up to five metres wide and occurs within the Goldex Granodiorite, just south of the Deep 1 Zone and north of the M Zone.
Several vein sets exist within the M, E and Deep 1 zones, of which the main set consists of extensional-shear veins dipping approximately 30 degrees south. The vein sets and associated alteration halos combine to form stacked envelopes up to 30 metres thick.
Moderate to strong albite-carbonate alteration of the host-rock quartz diorite surrounds the quartz-tourmaline-pyrite veins and covers almost 80% of the mineralized zone; outside of the envelopes, prior chlorite alteration affects the quartz diorite and gives it a darker grey-green colour. Occasionally, enclaves of relatively unaltered medium grey-green-coloured quartz diorite (with no veining or gold) are found within the M, E and Deep 1 zones. They are removed with the rest of the stope's ore to allow for a smooth stope shape, which is required for mining purposes.
Most of the gold occurs as microscopic particles that are almost always associated with pyrite, generally adjacent to pyrite grains and crystals but also 20% included within the pyrite. The gold-bearing pyrite occurs in the quartz-tourmaline veins and in narrow fractures in the albite-carbonatealtered quartz diorite (generally immediately adjacent to the veins).
Gold mineralization in the South Zone corresponds to a quartz-biotite-sulphide vein deposit. Gold is mainly associated to sulphides (pyrrhotite, chalcopyrite, sphalerite and pyrite) along horizons altered in silica and biotite. The host rocks are a sequence of volcanic rocks (andesite, basalts, gabbro and komatiite) located south of the Goldex main deposit. The deposit presents a strong structural control, related to ductile shearing and brittle faulting as based on the actual observations. Studies are underway to better understand the geological model.
Akasaba West property
The satellite Akasaba West property located 30 km from Goldex hosts a low-grade, gold-mineralized envelope characterized by the widespread presence of finely disseminated chalcopyrite; the mineralization is primarily contained within the quartz diorite unit.
The mineralization zone on the Akasaba West property consists of a low-grade mineralized envelope characterized by the widespread presence of finely disseminated chalcopyrite; the mineralization is primarily contained within the quartz diorite unit.
The gold was thought to be associated with stratiformed disseminated to semi-massive lenses of pyrrhotite-chalcopyrite hosted in mafic lapilli tuffs and brecciated basalt altered with epidote- hornblend-actinolite related to contact metamorphism. The genesis of the deposit remains very controversial. Two master thesis present two different hypothesis. One of those masters (Lev Vorobiev, 1998) supports the hypothesis that the mineralization is emplaced during skarn development whereas the other the (Jeanne Lebel, 1987) was in favor a VMS genesis hypothesis. It is possible that the actual Akasaba deposit characteristics and geometry is a result of an overprinting of several gold mineralization events (hydrothermal, orogenic and skarn).