Sediment-Hosted Stratiform Copper (SSC) Deposits

Nomenclature for this class of sediment-hosted, Cu-dominated sulfide deposits is problematic. It has been variously described as, to name a few, sediment-hosted copper deposits (Edwards & Atkinson 1986), stratiform copper deposits (Brown 1978), strata-bound copper deposits (Maiden et al. 1984), sediment-hosted stratiform copper deposits (Kirkham 1989), a subclass of stratiform sulfides of marine and marine-volcanic association (Stanton 1972), and examples of sedimentary-type stratiform ore deposits formed in intracratonic basins (Morganti 1981). None of these names is entirely appropriate. The term sediment-hosted stratiform copper (SSC) deposits is considered to be the best compromise as it emphasizes, in addition to the sedimentary host rocks, two other characteristics — the stratiform nature of mineralization and the dominance of copper — that separate this class of deposits from other classes of sediment-hosted deposits. The descriptor ‘stratiform’ is not entirely accurate, because mineralized zones are not always conformable with bedding, but quite adequate if it is allowed to include slightly transgressive morphologies of such zones (Brown 1989). To describe such mineralization as strata-bound would be a greater distortion of the overall picture. The native copper (-native silver) deposits of the Keweenaw district, Michigan (USA), are not considered to be members of this class, because those are volcanic-hosted, flow-top deposits and their configurations are generally too irregular to qualify as stratiform, although the genesis of the two types of deposits have many features in common.