Space-time distribution, crustal setting and Cu/Mo ratios of central Andean porphyry copper deposits: metallogenic implications.

Abstract

At least 80 porphyry copper centres, 18 of them major deposits, exist in the central Andes. They belong to four N-S belts younging from late Cretaceous in the W to late Miocene in the E, and are underlain by sialic crust 35-60 km thick. Pre-Mesozoic basement ranges from 2000 m.y. old granulites to Palaeozoic magmatic and sedimentary units. Hypogene Cu/Mo ratios range from 22 to 88 with no pattern. This suggests a subcrustal origin for the metals and the fact that the belts are parallel to the Peru-Chile trench indicates that subduction processes are involved in the liberation of the metals.-R.E.S.