The role of basin-scale transgression and sediment compaction in stratiform copper mineralization: implications from White Pine, Michigan, USA

We present a paleohydrologic model of stratiform copper mineralization in t he Keweenawan Midcontinent Rift System. We attribute regional-scale mineral ization in the basal facies of the transgressive Nonesuch Formation to comp action of the subjacent fluvial Copper Harbor Formation in response to depo sition of the superjacent fluvial Freda Formation. The transgressive sequen ce focused compaction-driven discharge of cupriferous brines in the Copper Harbor Formation to the basin margins, where leakage into the overlying Non esuch Formation drove redox-controlled copper precipitation. Intense fluid focusing atop a basement high formed the White Pine ore body. The timing of this simulated event is consistent with the inferred timing of stratiform mineralization. Our model satisfies mass-balance constraints at White Pine for a geologically plausible range of permeabilities and copper concentrati ons. (C) 2000 Elsevier Science B.V. All rights reserved.