Geologic observations in the San Marcos area, Coahuila, Mexico: the case for sediment-hosted stratiform copper–silver mineralization in the Sabinas basin during the Laramide orogeny

The sediment-hosted stratiform copper–silver mineralization in the San Marcos area of Coahuila, northeastern Mexico occurs predominantly at an Early Cretaceous redox boundary between footwall siliciclastic red beds Formation and hanging-wall carbonate strata Cupido Sabinas basin. hypogene is mainly present as chalcocite-group minerals, with additional bornite chalcopyrite, everywhere both disseminated vein/veinlet forms. Supergene copper-bearing oxides (malachite, chalcanthite, azurite, chrysocolla) are, however, dominant surface expression mineralization. Additional also occurs, albeit erratically, lower basin well veins basement granitoids, thus spanning ~3000 m stratigraphy. Where best developed, displays intense structural control proximal to regional fault system. This major bounding fault, nature numerous periods activity, controlled evolution Structural controls on include stacked, shallow-angle, bedding-parallel, northeast-vergent thrust faults associated drag folds, addition numerous, steeply-dipping, northeast-trending veinlets. mineralized veinlets, bedding-parallel thrusts display mutually crosscutting relationships. These elements are all consistent harmony a direction horizontal shortening accompanying reverse motion Inversion along system, entire Paleogene from ~60 40 Ma, resulted wholesale contractional deformation during Laramide (Mexican) orogeny. Hence, emplacement Marcos, elsewhere larger Coahuila region, interpreted natural corollary large-scale, metal-bearing fluid expulsion, migration, precipitation resulting orogenic shortening, lithostatic loading, squeezing Mexican orogen construction. Although sedimentation host took place pericratonic setting opening Gulf Mexico, copper-silver occurred uplift conversion original into orogen-foreland pair, similarities some world´s largest copper provinces.