Assessing the longevity of porphyry Cu-Mo deposits: examples from the Chilean Andes

Recent geochronological work for the Toki cluster in the Chuquicamata district, Chile indicates that molybdenite mineralization occurred within a very short period of time, probably within 2 Ma and synchronously at similar to 38 Ma. Mineralization preceded the emplacement of the Chuquicamata deposit (35-31 Ma) and indicates that porphyry mineralization occurred episodically over a period of several Ma in the Chuquicamata district. Geochronological data for the Escondida district shows that Escondida Norte was emplaced first at 37-38 Ma, followed by Escondida (36-35 Ma). Zaldivar appears to have formed over a larger time span (37-35 Ma). At the Collahuasi district (Quebrada Blanca, Rosario, Ujina) combined analytical techniques indicate that emplacement of these deposits occurred at 37-35 Ma, within a time span of 2 to 3 Ma. Late Miocene - Early Pliocene porphyry copper deposits are represented by the large Los - Pelambres (12-10 Ma), El Pachon (similar to 8 Ma), San Felipe - Pimenton (12-10 Ma), Rio Blanco - Los Bronces (9-5 Ma) and El Teniente (5-4 Ma). Most porphyry Cu-Mo deposits formed within several short pulses of mineralization over time spans of 2-4 Ma Within a porphyry district deposits can form at the same time or episodically within a period of 2-5 Ma.