Industrial mineral potential in the Appalachians

N'Golo Togola
Géologie Québec

The Appalachian orogenic belt in Québec offers great potential for asbestos (chrysotile), talc, steatite (soapstone), high-purity limestone, silica, peat and salt. It also hosts a few undeveloped deposits of barite, chromite and gypsum.

Several chrysotile orebodies associated with the ophiolite zone in the Appalachians of southwestern Québec (Estrie and Beauce regions) were once mined in the late 19^th century and throughout the 20^th century. This ophiolite zone lies along the Baie Verte- Brompton Line, a regional-scale intense deformation corridor. Numerous talc and steatite deposits associated with this zone have also been mined in the past. However, the only talc operation in Québec, located near Saint-Pierre-de-Broughton, shut down in 2001 due to the presence of asbestos fibres in the ore. Nevertheless, steatite is still being extracted at the Fraser mine near East-Broughton.

In the Appalachians of Québec, limestones are quarried in the Lake Champlain area (Missisquoi Bay) south of Saint-Jean-sur-Richelieu, and in Lime Ridge northeast of Sherbrooke. Other potential sources of pure limestone were identified in the Bas-Saint-Laurent region and in eastern Québec, in the Gaspésie region. In the Lake Champlain area, mined limestones are part of the Corey and Strites Pond formations (Philipsburg Group). In Lime Ridge, where lime production has been going on for over 150 years, quarries operated by Graymont Inc. are located in a very pure, partly recrystallized reef limestone. In the Bas-Saint-Laurent region, limestones of the Témiscouata, Sayabec, Rivière-Ouelle and Romieu formations offer good potential for industrial stone purposes. Argillites of the L’Orignal Formation in Lepage Township (Mont-Joli area) were once extracted to manufacture clay products. An obsidian deposit occurs in the easternmost part of the region, in the Mont Tuzo and Mont Squaw Cap area. In the Gaspésie region, important deposits of pure limestone associated with the West Point and de la Vieille formations (Chaleur Group) were identified in Lefrançois Township south of Rivière-Madeleine, as well as in the Port-Daniel area south of Baie des Chaleurs.

In the Bas-Saint-Laurent and Gaspésie regions, quartz-rich sandstones of the Val-Brillant and Kamouraska formations have a silica content greater than 96%, and constitute potential sources of silica. These two sandstone units have been mined in the past as a source of siliceous flux.

The Bas-Saint-Laurent region plays a major role in Québec’s peat industry. There are at least twenty peat deposits in the region, primarily located along the fleuve Saint-Laurent. Production figures for the region represent 50% of the total peat output in Québec. Most of the harvested peat is shipped to some forty different countries.

The Permo-Carboniferous basin of the Appalachians (Magdalen Basin) hosts salt and gypsum deposits and also constitutes a source of silica sand. Seven important salt deposits, some with interesting potassium grades, were discovered in the bedrock of the Îles-de-la-Madeleine, at depths ranging from 30 to 300 metres. The most important, the Rocher-au-Dauphin orebody, has been mined since 1982 by Mines Seleine Inc.

Dunes and tombolos on the Îles-de-la-Madeleine, along with part of the continental platform along the eastern margin of the archipelago, consist of silica sand, essentially derived from sandstones. This sand deposit, located in the Sandy Hook channel between Île-d’Entrée and Île-du-Havre-Aubert has been evaluated as a source of silica sand for smelting and glass. This sand contains a significant proportion of feldspar however, which must be removed.

Sedimentary basins in the Appalachian orogenic belt host a few barite deposits. The Upton orebody (Robex), associated with the Upton Group, and the Saint-Fabien deposit located in the Saint-Damase Formation (Trois-Pistoles Group) are currently the two largest known barite deposits in Québec. They have not been the object of mining operations however.

Ophiolitic complexes in the Appalachians (Thetford Mines, Asbestos and Orford area) host numerous podiform chromite deposits. The latter are hosted in dunite lenses within tectonized harzburgites, and in dunite horizons within cumulate sequences overlying the harzburgite. Several of these deposits were mined during the two world wars.

The main gypsum deposits occur as 5 cm to 5 m beds in a breccia with mudstone and sandstone fragments of the Maisons Formation (Windsor Group). Tiphane (1970) estimates at some 100,000 tonnes the amount of good-quality gypsum that could be easily extracted from the bedrock of the Îles-de-la-Madeleine.

Outlook and Opportunities

The ophiolitic complex in the Appalachian orogenic belt of southwestern Québec constitutes a prospective geological setting for the discovery of new chrysotile asbestos, talc and steatite deposits. Sedimentary basins in the Appalachians, on the other hand, offer good potential for industrial stone (limestone, silica) and for salt and gypsum deposits.

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