Tectonomagmatic controls on localization of porphyry cooper deposits, Chile

摘要

Several of the world's largest porphyry copper deposits, including Chuquicamata and La Escondida, occur within the West Fissure Zone, an 800-km-long, N-S-trending corridor of strike-slip faults in northern Chile. Location within this corridor is controlled by intersection of the WFZ with oblique, NW-trending lineaments, which appear to mark deep-seated, long-lived discontinuities in the basement. It is argued that generation of porphyry mineralization at these loci in the Late Eocene-Early Oligocene is a function of:(1) suitable (translithospheric) structural framework; (2) stress field oriented in such a way as to impose tension or transtension on this framework; (3) voluminous shallow-level calc-alkaline plutonism; (4) appropriate oxidation state and contents of water and sulphur in the magmas to promote volatile exsolution prior to sulphur saturation during differentiation; and (5) supergene enrichment. Omission or ineffective operation of any one of these factors will reduce the efficiency of the ore-forming process, or prevent the formation of deposits altogether.