GEOLOGICAL JACKPOT

The Louvicourt copper-zinc-silver-gold massive sulphide deposit, 24 km east of Val d’Or, Que., has 35.9 million tons (32.5 million tonnes) of geological reserves. These grade 3.11% copper, 1.34% zinc, 0.55 oz. silver and 0.025 oz. gold per ton (18.7 grams silver and 0.86 grams gold per tonne), based on cutoff grades of 2% copper or 4% zinc. Included in this reserve and based on cutoff grades of 4% copper or 6% zinc, is a high-grade core of 17.4 million tons (15.9 million tonnes) grading 5.64% copper, 2.27% zinc, 1.05 oz. silver and 0.044 oz. gold (36 grams silver and 1.5 grams gold per tonne).

The property is being explored by Aur Resources under the terms of a joint venture with La Societe Miniere Louvem. Most of the area covered by the current property was originally explored by Dome Mines in 1949. In 1960 it was acquired by the Brossard group of companies, and from 1963 to 1964 part of the property was optioned to Hollinger Quebec Exploration. Then in 1967, SOQUEM (Societe Quebecoise Exploration Miniere) optioned the entire property. The Louvem copper deposit and the east and west zinc zones (discovered in 1968 and 1969) were mined from 1971 to 1981 by La Societe Miniere Louvem, the operating subsidiary of SOQUEM.

In 1987, Aur Resources optioned the property and began a systematic re-evaluation of the exploration work conducted on it. The potential of the Louvem horizon was assessed below 1,000 ft. (300 metres) depth by drilling a series of deep holes on 300-metre spacing from west to east across the property. The combination of lithogeochemistry, geology and borehole pulse electromagnetic survey identified a large hydrothermal system that appeared to be increasing in size to the east and coincided with copper enrichment with depth. Follow-up drilling, which began in mid-April, 1989, led to the discovery of a major copper-zinc-silver-gold deposit, announced June 12. A horizon of cherty tuffs was intersected stratigraphically above the copper stringer zone. In late 1988, a hole deepened beneath the Louvem horizon intersected mineralization in the “Aur horizon,” which resulted in the discovery of a new massive sulphide deposit in June, 1989.

The Aur/Louvem property lies within the west-striking, north-dipping Val d’Or formation, which consists predominantly of ash and lapilli tuff, agglomerate, cherty tuff and lesser abundant diorite sills and intermediate volcanic flow rocks. The Val d’Or formation is about one mile (1.6 km) in thickness and more than 25 miles (40 km) in length and hosts a number of base metal sulphide and gold deposits.

At the property, the stratigraphic sequence strikes west, and dips to the north at about 70^o (deg). The younging direction has been determined to be to the south and consequently the sequence is overturned. The stratigraphic footwall to the north is composed of massive and pillowed andesite with auriferous quartz- carbonate-pyrite veins associated with feldspar porphyry dykes. The andesite is stratigraphically overlain by a sequence of poorly sorted heterolithic ash and lapilli tuff which, in turn, is overlain by felsic agglomerate with bomb-sized quartz porphyritic rhyolite clasts in a green chloritic matrix termed the “white fragment breccia.” The agglomerate is overlain by an altered volcano-sedimentary sequence (“tuff sequence”) of finely bedded ash, lapilli and cherty tuff, which hosts the massive sulphide mineralization. This sequence is overlain by irregularly distributed intermediate volcanic flow rocks termed “caprock,” and felsic pyroclastic rocks farther to the south.

The volcano-sedimentary sequence is strongly altered throughout and contains two mappable sulphide horizons: the formerly producing Louvem horizon (near the north contact with the white fragment breccia) and the Aur horizon (which hosts the new deposit and which is 600 ft., or 180 metres, stratigraphically above the Louvem horizon).

Mineralization in the Aur horizon consists of massive pyrite and chalcopyrite. Chalcopyrite is also abundant in stringer ore in the stratigraphic footwall. Sphalerite occurs in bedded chert in the rocks of the hangingwall. The black chlorite alteration (which forms a semi-conformable layer beneath, and occasionally above, the massive sulphide mineralization) grades outwardly to strongly sericitized rock characterized by intense sodium and calcium depletion and magnesium and potassium enrichment. In places, aluminum enrichment has resulted in the formation of garnet. Other alteration minerals include chlorite, magnetite, and chloritoid.

The new discovery, 2,000 ft. (600 metres) east of the old Louvem mine workings, starts at a vertical depth of about 1,000 ft. and has a known strike length of at least 390 metres. The deposit averages 80 to 100 ft in thickness (24 to 30 metres) and in places it is up to 90 metres thick. It has a moderately steep plunge to the east and is open down plunge. A program of delineation drilling is under way.

The author would like to thank Howard Stockford, executive vice-president of Aur Resources, and George Mannard, senior project geologist for the company, for their assistance.