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Boletín de la Sociedad Geológica Mexicana
http://dx.doi.org/10.18268/BSGM2006v58n1a1 |
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Características metalogenéticas de los depósitos de tipo pórfido cuprífero en México y su situación en el contexto mundial
Martín Valencia-Moreno1*, Lucas Ochoa-Landín2, Benito Noguez-Alcántara3, Joaquin Ruiz4, Efrén Pérez-Segura2
1Estación Regional del Noroeste, Instituto de Geología, UNAM, Apartado Postal 1039, Hermosillo, Sonora, México 83000.
2Departamento de Geología, Universidad de Sonora, Hermosillo, Sonora, 83000.
3Servicios Industriales Peñoles S.A. de C.V., Blvd. Navarrete 277, Hermosillo, Sonora, México, 83170.
4Department of Geociences, University of Arizona, Tucson, AZ, 85721
* This email address is being protected from spambots. You need JavaScript enabled to view it.
Abstract
The widespread magmatic activity that took place during the end of the Mesozoic and the beginning of the Cenozoic along the North American Cordillera produced the emplacement of numerous centers of porphyry copper mineralization. This activity extended through most of western Mexico, particularly along the northwestern part of the country. This part along with the neighbor regions of Arizona and New Mexico, in the United Status, constitutes one of the most important centers of copper mineralization on earth, which may compete in size with the famous deposits of the western Cordillera of South America. Most of the Mexican porphyry copper deposits are located in the eastern part of the Laramide magmatic belt (90-40 Ma) and have ages predominantly between 75 and 50 Ma. The largest and best preserved deposits occur in northeastern Sonora, in the northern part of the belt, where Cananea (~30 Mt Cu) and La Caridad (~8 Mt Cu) accomplish metal concentrations of great relevance at world-level. The copper ores are commonly accompanied by locally important concentrations of molybdenum, tungsten and gold. The metal distribution is apparently associated with regional changes in the type of basement where the ores were emplaced. In general, three main basement domains are distinguished: a northern domain which is characterized by a Proterozoic crystalline basement associated with the North America and the Caborca terranes; a central domain composed by Paleozoic deep-marine water rocks underlain by the crystalline rocks of the Caborca terrane; and a southern domain that is represented by the Mesozoic island-arc related sequences of the Guerrero terrane. The available Sr and Nd isotopic data show that the Laramide plutons in the northern and central domains display more evolved signatures compared to the those of the southern domain, which suggest the that intruded basement played an important role in the final composition of the Laramide magmas, and may have also acted as an important control in the spatial distribution of the porphyry copper metals in the northwestern Mexico systems. In general, although the metals are not geographically restricted, a dominance of Cu-Mo-W can be observed in the north and central domains of the mineralized belt underlain by the ancient rocks of North American affinity, which hosts the most important ore deposits. Moreover, there are several high-grade molybdenum breccia pipe bodies in this part of the belt, just south of the region of Cananea and La Caridad, which may suggest a relatively larger tectonic uplift and erosion. More to the south, the belt is underlain by younger rocks of oceanic affinity, characterized by the Guerrero terrane. The mineralization is typically of Cu-Au, and is well distributed in the southern domain; however, the size of the mineralized centers known so far are relatively small, being the deposits of El Arco in Baja California (~3.6 Mt Cu) and Santo Tomás in northern Sinaloa (~1.1 Mt Cu), the most significant examples. This type of mineralization extends even more to the south through the states of Michoacán, Guerrero and Chiapas, in the southern part of the country, but the economic possibilities of this region appear to be very limited compared to the northern part of the belt.
Keywords: Porphyry, copper, Mexico, magmatism, metallogenesis.
