Origin of shallow, sediment-hosted ‘hybrid’ orogenic-epithermal/intrusion-related gold-quartz vein systems in the Menneval-Saint-Quentin district, Aroostook-Percé Anticlinorium, northwest New Brunswick, Canada

Abstract

The genetically-related Maisie and Lavoie gold occurrences, respectively located west of Menneval and east of Saint-Quentin, New Brunswick, Canada, represent a new style of non-refractory Au mineralization in the Aroostook-Percé Anticlinorium. Veins are hosted in a flysch sequence (the Whites Brook Formation), and transition from early laminated, to massive, to late bladed/vuggy quartz(-carbonate) textures. Gold in the veins has a close spatial and textural relationship to trace amounts of partially hematitized pyrite, and other base metal sulfides (galena, sphalerite, chalcopyrite) and is paragenetically late-stage, infilling crystal-lined vugs and fractures in quartz. Pyrite chemistry, S-O-C-Sr isotope systematics of vein minerals, and geochronological considerations suggest magmatic involvement, providing heat and exotic metals (Au, Bi, Te, and possibly As, Pb, Sb, Se) to the hydrothermal systems otherwise dominated by an inherited sedimentary metamorphic fluid and metal signature. The Au occurrences are classified as a hybrid gold style with characteristics of both epizonal (shallow) orogenic Au and low-sulfidation epithermal or intrusion-related Au deposits. Rapid fluid boiling (“flashing”) combined with meteoric water mixing are suggested to be the primary mechanisms triggering Au precipitation. The Au occurrences are likely related to magmatic activity during the late Acadian Orogeny (<370 Ma).