Geologic evolution of the Escondida area, northern Chile: a model for spatial and temporal localisation of porphyry Cu mineralisation.

A programme of geological mapping and lithogeochemical and geochronological sampling has been carried out over 745 km2 around La Escondida, Zaldivar and Chimborazo. Andean-cycle arc magmatism began in the Triassic, moving eastward in the Palaeocene and producing widespread calc-alkaline intermediate to felsic volcanism throughout the Eocene. Stress relaxation at the end of the period coincided with the emplacement of voluminous diorites and also with porphyry development. Porphyry emplacement was localised within a broad zone of intersection between the West Fissure zone and a regionally extensive NW-trending structural corridor. The geometry of this junction may have been conducive to the formation of dilational structures, which focused the ascent and pooling of magma in the upper crust and maximised the potential for formation of magmatic-hydrothermal ore deposits.
A programme of geological mapping and lithogeochemical and geochronological sampling has been carried out over 745 km2 around La Escondida, Zaldivar and Chimborazo. Andean-cycle arc magmatism began in the Triassic, moving eastward in the Palaeocene and producing widespread calc-alkaline intermediate to felsic volcanism throughout the Eocene. Stress relaxation at the end of the period coincided with the emplacement of voluminous diorites and also with porphyry development. Porphyry emplacement was localised within a broad zone of intersection between the West Fissure zone and a regionally extensive NW-trending structural corridor. The geometry of this junction may have been conducive to the formation of dilational structures, which focused the ascent and pooling of magma in the upper crust and maximised the potential for formation of magmatic-hydrothermal ore deposits.