Dome Lemieux nothing if not complicated

SITE VISIT

Sainte-Anne-des-Monts, Que. — “Are we sitting on a magmatic deposit?” asks an investor on a recent tour of Threegold Resources’ (THG-V, TRLDF-O) Dome Lemieux project, as he joins other visitors congregating on the Dome’s southeastern flank to enjoy a lunch of Gaspsie salmon.

Noront Resources’ (NOT-V, NOSOF-O) new discovery at the Double Eagle project in the James Bay lowlands is fresh on the minds of some of the retail investors and brokers visiting the Threegold site, 50 km southeast of Sainte-Anne-des-Monts in the Gasp region of Quebec.

As they eye samples of high-grade mineralization on display outside the lunch tent, a few are wondering if this could be another Double Eagle, a high-grade nickel-copper discovery that sent Noront’s shares soaring from pennies to more than $5 per share in a matter of weeks.

Double Eagle, roughly 1,000 km west of Dome Lemieux, has some of the signatures of a magmatic deposit similar to the rich Voisey’s Bay nickel deposit in Labrador, though much more drilling will be needed to better understand the extent and geology of the zone.

The styles of mineralization at Dome Lemieux, though varied, appear to be entirely different.

Since the early 1900s, when two prospectors discovered mineralized boulders containing galena (lead sulphide), there have been several waves of exploration on the Dome. Some companies looked for skarn deposits (Noranda, Sullico Mines, SOQUEM), or for porphyry copper mineralization, while others investigated the area’s potential to host iron oxide copper-gold (IOCG) deposits similar to the rich Olympic Dam deposit in Australia.

“The mineralization styles change dramatically within a couple of hundred metres,” says Antoine Fournier, president of Threegold, as he steers investors towards a mineralized hematite breccia typical of the area. Other than mineralization typical of skarns, porphyries and IOCG deposits, there is plenty of evidence on surface of epithermal mineralization in the form of sulphide-rich fractures and quartz veins.

Despite the confusing array, the visitors like what they see at Dome Lemieux. Threegold’s share price added 19 to an intraday high of 85 the day after the mid-October tour, before settling back to a pre-tour range of 65-75.

Threegold is a spinoff of diamond explorer Dianor Resources (DOR-V, RSDNF-O) with a mandate to acquire and explore for base and precious metal deposits while Dianor focuses on diamonds. The new company’s shares were listed on the TSX Venture Exchange in June 2006.

Since then, Threegold has focused its attention on the Dome Lemieux, a 100-sq.-km subcircular formation of sedimentary rocks that is cut by numerous mafic and felsic sills and dykes of Silurian to Late Devonian age. The emplacement of the underlying pluton is thought to have caused widespread epithermal mineralization throughout the Dome, with zinc-lead mineralization following southeast-northwest structures and copper-gold mineralization occurring near, or within, north-south faults.

For instance, the Federal mine in the southern part of the Dome comprises a series of subvertical quartz-carbonate-sphalerite-galena veins associated with felsic dykes. The veins produced about 600,000 tonnes grading 3.95% zinc and 1.31% lead when they were mined chiefly for their lead content during the First World War.

By contrast, the northern half of the dome is characterized by occurrences such as Pardiac, a copper-gold showing lying within a north-south-trending fault where a mafic dyke is cut by quartz-hematite-pyrite veins. Mineralization is hosted by stockworks and breccias over a strike length of 175 metres with a thickness of 10-40 metres. Previous drilling returned grades of up to 1% copper over 10.5 metres and 91 parts per billion gold over 3.5 metres.

Current exploration

Threegold is the first company to hold rights to the entire dome structure and, with all the different mineralization styles and a plethora of showings to choose from, the company’s geologists have their work cut out for them. A 7,000-metre, 31-hole diamond-drilling program now under way is designed to intersect mineralization present on surface at 11 distinct locations.

The first target is Big Pioneer, a fault structure that has been traced for about 1 km on surface. Big Pioneer consists of a series of parallel, mineralized zones with quartz veins that assayed as high as 4.2% copper, 8.2% zinc and 41 grams gold per tonne in individual grab samples. The 12-hole program is designed to intersect the mineralization at depths of 100-150 metres over the entire structure.

“We’re focusing on Big Pioneer because, on surface, it’s our most continuous zone,” Fournier says. “It’s a complex structure with veining and the veins are sometimes folded within the shear corridor.”

After Big Pioneer, Threegold will test several other structures with two holes each, including high-grade copper in the Gasse Showing, copper-gold mineralization at Pardiac and Brandy South, the Eagle-Gaspsie mineralized occurrences, the zinc-lead showing at the former Federal mine site, and other sites.

The property package includes the Mont-de-l’Aigle property, where Threegold is earning a 50% interest from Rimouski, Que.-based Ressources Appalaches (APP-V, ALHRF-O) by spending $2 million over five years. The rest of the package has either been acquired by option or by map staking.

IOCG potential

Mont-de-l’Aigle, in the northern part of the Dome, has been extensively investigated for its IOCG potential. The property is characterized by copper-iron oxide veins, stockworks and breccias (including Pardiac) with gold values up to 2.2 grams per tonne. Mineralization is associated spatially with faults and mafic to felsic intrusions, and consists of abundant hematite and large breccia bodies.

Many of the features of Mont-de-l’Aigle (abundant hematite, the breccia association) are consistent with IOCG deposits, except for the Palaeozoic age of the host rocks. Fournier, however, is uncomfortable with the IOCG label for the area, preferring to limit the model to Olympic Dam-type deposits of Proterozoic age.

The other styles of mineralization are skarn-type and copper porphyry-type, similar to the styles at Gasp Copper, a mine to the northeast of Dome Lemieux that produced 142 million tonnes of ore grading 0.85% copper from 1955-1999.

“This is typical of what they had at Gasp Copper — skarns close to the intrusive and, further away, porphyry mineralization,” Fournier says. “At the Lemieux project, it appears that there is quite bit of epithermal mineralization too.”

Fournier and his team will get a better handle on the various styles of mineralization and their economic potential once the drilling is complete and they can see how the veins behave at depth and in three dimensions. One thing they won’t find, though, is another Double Eagle.

— The author is a freelance writer specializing in mining issues, and principal of Toronto-based GeoPen Communications ( www.geopen.com ).