Geology, Mineralization, Alteration, and Structural Evolution of the El Teniente Porphyry Cu-Mo Deposit

This is the authors' abstract. We don't add key points for this paper.

El Teniente is a typical porphyry Cu-Mo deposit-in terms of its alteration and sulfide assemblage zonation, with felsic intrusions, and predominance of quartz vein-hosted copper mineralization. It is anomalous size, with >94 million metric tons (Mt) of contained fine copper making it the worlds largest known Cu deposit. There is an intimate spatial and temporal association between all stages of mineralization latest Miocene to early Pliocene felsic intrusions at Teniente. of the copper was emplaced during the late magmatic stage (5.9-4.9 Ma), contemporaneously with intrusion the dacite porphyry dike and dacite pipes into a mafic to intermediate sill-stock complex. Mineralization the late magmatic stage is mainly hosted by a quartz-anhydrite-dominated stockwork associated with -feldspar alteration in the dacites and Na-K-feldspar, biotite, and propylitic alteration of the mafic intrusive . Minor copper-mineralized hydrothermal biotite-cemented breccias formed at this time. The late stage was followed by two stages of mineralized phyllic alteration, referred to as the principal hydrothermal (4.9-4.8 Ma) and late hydrothermal (4.8-4.4 Ma) stages, during which thicker, Cu-rich veins were . A 1,200-m-wide breccia pipe, the Braden Breccia, formed during the late hydrothermal stage and to have destroyed a large amount of ore from the center of the deposit. late magmatic and principal hydrothermal vein stages have predominantly concentric and radial vein centered on the Braden Pipe. Most of the concentric veins are shallowly dipping, whereas the radial are subvertical. We present a model in which vein distributions were controlled by the local stress generated by the intrusion of a large, deep magma chamber that is interpreted to be the source of the , the Braden Pipe, and ultimately, the copper and molybdenum mineralization. The late hydrothermal are steeply inward dipping and concentric to the Braden Pipe. In contrast to the late magmatic and principal vein stages, radial veins and shallow-dipping concentric veins are rare, consistent with formation a stage of subsidence due to relaxation of intrusion-induced stresses. Resurgence of the magma reactivated the steep concentric structures in a reverse sense, and a build up of magmatic and/or fluid resulted in explosive brecciation and fluidization, producing the Braden Pipe. A predominantly late set of northeast-trending faults, associated with movements on the district-scale Teniente fault zone, is the only evidence for far-field stresses exceeding local stresses in the deposit.