Geological and metallogenetic characteristics of the porphyry copper deposits of México and their situation in the world context

The sustained magmatic activity along the North American Cordillera during late Mesozoic and Paleogene times produced the emplacement of numerous porphyry copper deposits. This activity extended by most of western México, particularly along the northwestern part of the country. This region, along with Arizona and New Mexico in the United States, contains one of the most important centers of copper mineralization on Earth. Most of the Mexican deposits lie in the eastern part of the Laramide magmatic belt (90-40 Ma) and were formed predominantly between 75 and 50 Ma. The largest deposits occur in northeastern Sonora and are represented by Cananea (∼30 Mt Cu) and La Caridad (∼8 Mt Cu). The copper ores are locally accompanied by molybdenum, tungsten, gold, and other metals. However, the metal distribution is apparently coupled with major changes in the basement of emplacement, which can be roughly separated into three domains: a northern domain characterized by Proterozoic crystalline rocks of North American affinity; a central domain composed of Paleozoic deep-marine basin rocks underlain by the Proterozoic North American rocks; and a southern domain, represented by Mesozoic island-arc-related sequences of the Guerrero terrane. Sr and Nd iso- topic data from Laramide plutons along these domains suggest that the basement modified the final composition of the Laramide magmas. Also, the basement seems to have partly controlled the metal commodities along the porphyry copper belt, with relatively larger deposits characterized by Cu-Mo-W mineralization in the northern and central domains, and smaller and more Cu-Au dominated systems in the southern (more oceanic) domain.