Abstract

The Huntingdon mine, situated in the ophiolite belt of the Quebec Applachians, is a 1.9-million-metric-ton copper deposit mined from 1954 to 1957. The deposit is hosted by a pillowed mafic volcanic unit at or near a faulted contact with a serpentinite body located in a highly tectonized zone composed of discontinuous slices of graywackes and slates together with ophiolite-derived rocks. The mineralization consists of disseminated, stockwork, and massive ore types composed of chalcopyrite and pyrrhotite, and minor amounts of pyrite and sphalerite. The gangue minerals are quartz and minor chlorite and carbonate.Mineralogical and textural observations indicate that the mineralization and associated alteration took place prior to orogenesis. Major element geochemistry exhibits hydrothermal alteration patterns typical of volcanogenic deposits in mafic rocks. The host rocks show an almost total loss of alkali elements (mainly Ca) and a simultaneous gain of Fe and Mg toward the mineralized zone. Potassic metasomatism also occurs near massive mineralization. Trace element geochemistry indicates that the volcanic host rocks are similar to the volcanics of the Thetford Mines ophiolite situated in the same belt and that they are boninitic in nature.The Huntingdon deposit is interpreted as a typical ophiolitic, Cyprus-type volcanogenic deposit that was subsequently deformed, recrystallized, and partly remobilized during later tectonic events.

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