Talk by Antoni Camprubí: IOCG deposits in Mexico: more questions than answers?

Title: IOCG deposits in Mexico: more questions than answers?

Lecturer: Antoni Camprubí (Centre of Geosciences and the institutes of Geophysics and Geology-UNAM)

Date: Thrusday October 31st 2013. 13:00h

Place: Room 2

Abstract: Magmatic-hydrothermal iron oxide deposits, or IOCG "clan", are a group of ore deposit types that formed in a wide range of tectonomagmatic environments and depths of emplacement: from intra-arc or back-arc environments to those related with anorogenic magmatism (even in association with carbonatites), and from near-surface to deeper than 10 km deposits. The occurrence in Mexico of these deposits spans from Lower Cretaceous to Miocene examples, whose minimum distance from their respective hypothetical subduction trenches in the Pacific convergent margin suggests the existence of at least two groups of IOCG types of deposits from the tectonomagmatic standpoint.

On the one hand, there is a large amount of these deposits located near the edge of the present Pacific coast, running from the Baja California peninsula to the state of Chiapas. Such distribution is very similar to that of similar deposits in the Andean coastal ranges, and suggests that their formation might have occurred in a similar setting, likely to be due to extensional intra-arc magmatism. The latter would have fringed the buildup of continental crust prior to and simultaneously to part of the Laramide orogeny (~80 a 40 Ma), which ultimately deactivated the formation of IOCG deposits and led to the formation of other types of ore deposits.

On the other hand, many other IOCG deposits are clearly distal to the Pacific margin before the Baja California rift-off, between ~500 and ~1000 km inland. Such is the case of the Eastern Mexican Alkaline Province (EMAP), which formed entirely in the Cenozoic and also contains carbonatites. This feature suggests additional tectonomagmatic environments for IOCG formation in Mexico, which also occur in the Cordillera of Western North America, but not in the Andes. The EMAP as a whole poses an interesting topic for further research in the metallogeny of Mexico, as its tectonomagmatic setting remains ill-defined to date.