The volcanic setting and paleomorphology of 'giant' bimodal mafic-type VMS deposits ― The case of Tambogrande, Peru

摘要

The Tambogrande volcanogenic massive sulphide (VMS) deposits represent one of the greatest known concentrations of "bimodal mafic-type" pyritic Cu-Zn-Au-Ag-bearing massive sulphide in the world, currently estimated at approximately 300 Mt in three sulphide mounds. The deposits formed in the northernmost of a series of Late Jurassic to Cretaceous continental-margin arc-associated rift basins along the west coast of South America. As with many similar deposits, massive sulphide mineralization at Tambogrande is intimately associated with a felsic volcanic complex within a basalt-dominated sequence. Seafloor pa-leotopographical models indicate that sulphide deposition occurred within steep-sided sub-basins and the geometry of the unusually thick massive sulphide lenses is the direct result of synvolcanic-faulting and dacite dome growth. The focusing of hydrothermal fluids within these restricted basins would have created increasingly efficient traps necessary for anomalously large sulphide deposits.