Great Mining Camps of Canada 3. The History and Geology of the Buchans Mine, Newfoundland and Labrador

The 1905 mineral discovery at Buchans River resulted from efforts by the Anglo-Newfoundland Development Company Lim ited (AND) to establish a pulp and paper industry in central Newfoundland. The discovery is attributed to Matty Mitchell, a legendary Mi’kmaq guide, who was employed by AND to assist William Canning in prospecting for sulphur on company leasehold land. The company explored the prospect and developed a small deposit, under the supervision of William Scott; however, early attempts to create a producing mine were frustrated by metallurgical difficulties and ended in 1911. Harry Guess, a director of the American Smelting and Refining Company Incorporated, (later ASARCO) had heard about the discovery, and in 1916 contacted William Scott. ASARCO conducted extensive research on samples of Buchans ore, and by 1925 had developed a successful metallurgical method of separating the fine-grained zinc, lead and copper minerals. In 1926, ASARCO entered into a 25-year agreement with AND and its subsidiary, Terra Nova Properties, to develop Buchans; Guess also made the decision to hire pioneer Swedish geo-physicist Hans Lundberg to conduct electrical prospecting on the property. In June and July of that year, Lundberg used his new geophysical technique to discover the Lucky Strike and Oriental orebodies. They would ultimately prove to be the first discoveries in North America attributed to the emerging science of electromagnetic prospecting. A production shaft was collared at Lucky Strike in 1926 and under the supervision of J. Ward Williams, construction began the following year on a 450 tonne per day mill as well as the townsite, railroad, hydroelectric plant and other facilities. The complex began production in September 1928 and by the end of 1929, ore reserves were approximately 5.6 million tonnes. The mill was enlarged to 1100 tonnes per day in 1931; by the end of 1947, ore reserves had declined to 1.4 million tonnes. However, renewed exploration resulted in two discoveries in 1947 and 1950, named the Rothermere and MacLean orebodies, respectively. The Buchans orebodies are part of the Middle Ordovician Buchans Group, which comprises an allochthonous sequence of bimodal, submarine volcanic rocks that were deposited in the Iapetus Ocean near the margin of Laurentia. These ore-bodies are classified as volcanogenic massive sulphide (VMS) deposits and are among the highest-grade examples of this class worldwide. From 1928 to 1984, ASARCO mined approximately 16 million tonnes from five orebodies, with an average mill head grade of 14.51% zinc, 7.56% lead, 1.33% copper, 126 g/t silver and 1.37 g/t gold. Apart from their high grade, these deposits are remarkable for the extensive development of debris-flow ores, which provided important evidence for seafloor deposition of VMS deposits in an era when this concept was not widely accepted. SOMMAIRE La decouverte minerale de 1905 a Buchans River, decoule des activites deployees par Anglo-Newfoundland Development Company Limited (AND) pour etablir une industrie des pâtes et papiers dans le centre de Terre-Neuve. La decouverte est attribuee a Matty Mitchell, un guide Micmac legendaire a l’emploi d’AND comme assistant de William Canning qui cherchait des indices de soufre sur des terres a bail de l'entreprise. L'entreprise a poursuivi des travaux sur le gisement et developpe un petit depot, sous la supervision de William Scott; cependant, cette premiere tentative pour creer une mine n’a pas aboutie a cause de problemes metallurgiques et en 1911, les travaux ont cesse. Harry Guess, un administrateur d’American Smelting and Refining Company Incorporated, (qui deviendra ASARCO) avait entendu parler de la decouverte a contacte William Scott en 1916. ASARCO a realise des recherches approfondies sur les echantillons de minerai de Buchans et, en 1925 a mis au point un procede metallurgique efficace permettant de separer les grains fins de mineraux de zinc, plomb et cuivre. En 1926, ASARCO a conclu une entente de 25 ans avec ADN et sa filiale, Proprietes Terra Nova, pour la mise en valeur de Buchans; Guess a egalement decide d'embaucher le pionnier suedois de la geophysique Hans Lundberg, afin de proceder a la prospection electrique de la propriete. En juin et juillet de cette annee, Lundberg a utilise sa nouvelle technique geophysique pour delimiter les gisements Lucky Strike et Oriental. Ce seront les toutes premieres decouvertes en Amerique du Nord attribuees a la nouvelle technique de prospection electromagnetique. Un puits a ete fonce a Lucky Strike en 1926 et l’annee suivante, sous la supervision de J. Ward Williams on a commence la construction d’une usine de traitement d’une capacite de 450 tonnes par jour ainsi que l’amenagement d’une ville miniere, d’un chemin de fer, d’une centrale hydroelectrique et d'autres installations. Le complexe a commence la production en Septembre 1928 et a la fin de 1929, les reserves de minerai totalisaient environ 5,6 millions de tonnes. En 1931, la capacite de l'u-sine a ete portee a 1100 tonnes par jour; vers la fin de 1947, les reserves de minerai avaient diminue a 1,4 millions de tonnes. Cependant, une nouvelle campagne d’exploration a conduit a deux decouvertes en 1947 et 1950, soit le gisement de Rothermere et le gisement de MacLean. Les gisements mineralises de Buchans font partie du Groupe de Buchans de l’Ordovicien moyen, et qui comprend une sequence allochtone bimodale de roches volcaniques sous-marines deposees dans l’ocean Iapetus pres de la marge de Laurentia. Ces gisements mineraux sont des depots de type sulfures massifs volcanogeniques (SMV) et sont parmi les exemples a plus haute teneur de ce type dans le monde. De 1928 a 1984, ASARCO a extrait environ 16 millions de tonnes de cinq gisements, avec une teneur moyenne du minerai traite de 14,51 % de zinc, de 7,56 % de plomb, de 1,33 % de cuivre, 126 g/t d’argent et 1,37 g/t d'or. Outre leur haute teneur, ces depots sont caracterises par leur forte proportion de minerai en coulee de debris, ce qui a constitue un indice determinant en faveur de l’hypothese de depots de SMV sur les fonds marins, a une epoque ou ce concept n’etait pas encore bien accepte.

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