Tectonomagmatic evolution and controls on formation of significant Miocene porphyry Cu-Au-Mo deposits and the giant Yanacocha Au deposit, northern Peru

摘要

The data presented show significant changes in the tectonic regime and magmatic source region were intimately associated with the timing and formation of the Miocene hydrothermal deposits. Structural data suggest counter-clockwise rotation of the dominant fault trend from NE to NW was linked with clockwise rotation of the subducting Nazca plate. Miocene faults superimposed on oblique pre-existing deeply tapping regional structures influenced the emplacement of diorite stocks, whilst upper crustal conjugate NE and NW faults possibly related to near NE-directed convergence provided important dilatant channelways for ascending hydrothermal fluids. Significantly, Early-Mid Miocene porphyry-related mineralisation was temporally associated with crustal thickening and development of an amphibole-rich source region from which hydrous- and sulphur-rich melts were generated. Continued uplift and crustal thickening throughout Miocene times led to magma generation from an amphibole-garnet source. Late Miocene high-sulphidation deposits formed toward the end of this period in conjunction with a flattening subduction zone. These results illustrate the complex tectonomagmatic processes associated with formation of these giant and/or significant hydrothermal ore deposits in the northern Peruvian Andes. Investigation of regionally extensive structural trends and their relative timing may provide a powerful tool for exploration in hidden terrains or extending exposed structures beneath volcanic cover for exploring potentially hidden mineralised stocks. This exploration tool is further enhanced by indepth analyses of mineralisation-related tectonic and magmatic processes.