Geological features and metallogenic model of the Escondida copper deposit in Chile

The Escondida deposit, located in the Andes copper belt of northern Chile, is the third largest porphyry copper deposit in the world with copper reserves of 31.567 millon tons. The formation of this deposit, controlled by Domeyko Fault System in terms of structure, is associated with the emplacement of a late Eocene-Oligocene quartz monzonitic to granodioritic intrusive stock complex hosted by Paleocene andesite. The typical types of hydrothermal alteration observed in the porphyry Cu-Mo deposit include K-feldspathization, biotitization, quartz-chloritization-sericitization, propylitization and advanced argillitization. The age of intrusive rocks related to mineralization is at about 38Ma. The Re-Os molybdenite ages are between 36.1Ma and 33.7Ma. The characteristics of fluid inclusions show that the regional metallogenic hydrothermal fluids can be divided into two phases: the early magmatic hydrothermal fluid with high temperature and the late hydrothermal fluid with low temperature and low salinity mixed with both magmatic hydrothermal fluid and groundwater, respectively. Negative anomalies of high field strength elements as well as characteristics of rare earth elements La/Yb and Sr-Nd isotope ratios reveal that the ore-bearing porphyries were derived from mantle magma mixed with a small amount of crustal material. The transtensional environment formed in the location of intersection between the SN-trending fault system of Domeyko and NW-trending linear structure played a key role in the emplacement of the ore-bearing porphyries in Escondida area.