Structural evolution of sulphide tectonites and their host rocks, Stratmat mine, New Brunswick

Abstract

The sulphide orebodies at the Stratmat mine in New Brunswick are treated as tectonites, because their primary characteristics have been so modified by deformation, recrystallization, and vein injection that most of their original features have been obscured. Pb–Zn–Cu sulphide orebodies at the Stratmat mine consist of sulphide and sulphide–silicate tectonites, gneisses, schists, phyllites, and slates produced by the mixing of two sulphide precursors and silicate host rocks by polyphase deformation, much of which relates to progressive non-coaxial deformation. Quartz-vein injection during and after this period of deformation, and the intermixing of nonsulphide lithotypes, led to dilution of the initial ore composition. Both the deformation of the orebodies and fluid migration, manifested by vein injection, reflect processes that were operative in a major shear zone. No indisputable primary characteristics of the orebodies are preserved, although a number of tectonic and (or) tectonically modified features mimic depositional features, e.g., quartz mylonites resemble "cherts," festoon veinlets resemble dismembered stockwork veins, sulphide mylonites resemble rock with an original fine-grain size and "extra" fold phases that could be mistaken for soft sediment folds.