Paper No. 9
Presentation Time: 11:30
METALLOGENIC EVOLUTION OF MEXICO DURING THE MESOZOIC: A COMPARISON WITH THE REST OF THE CORDILLERA OF WESTERN NORTH AMERICA AND THE ANDES
Many similarities arise between Mexico and the rest of the Cordillera of western North America from both the tectonomagmatic and metallogenic standpoints: (1) the accretionary oceanic, pericratonic (intermontane) and subduction-complex terranes along the western margin are similar in their nature and time-space dynamics, (2) deposits of the oceanic magmatic ‘realm’ (VMS deposits, and deposits associated with ultramafic-mafic complexes) were controlled by such terranes, and young southwards, (3) transitions between the oceanic to the continental ‘realm’ of ore deposits occur along the Cordillera in the Mesozoic, and also obey to a younging southwards pattern, (4) the resulting types of ore deposits in either the oceanic and continental magmatic, and in the sedimentary-diagenetic and orogenic-metamorphic ‘realms’ are very similar in the northern, central, and southern Cordillera, and (5) the time and space distributions of such deposits are analogous, they reveal that the shift from the oceanic to the continental magmatic ‘realm’ of ore deposits is complete during the Cenozoic, having progressed cratonwards and southwards. Such broadening in the distribution of magmatism, daughter ore deposits, and orogenic pulses responds to flattening of the subducted slab in the USA and Mexican sections of the Cordillera during the Late Mesozoic.
Although such analogies can be extended at some degree to the Andes, the most obvious similarities between the Cordillera of western North America and the Andes can be drawn as the ‘continentalization process’ of magmatism and ore deposition in the Cordillera completes towards the Cenozoic. This process also occurs in the northern half of the Andes. The cratonward and southward broadening in the distribution of magmatism, daughter ore deposits, and orogenic pulses, supports the theory of the flattening of the subducted slab in the USA and Mexican sections of the Cordillera during the Late Mesozoic, which might have started as early as in the Middle-Late Jurassic. Contrastingly, the subducted slab is steeper in the Andes and accounts for a much narrower distribution of ore deposits, with the exception of the time and space frames (e. g., presently, the Argentine Sierras Pampeanas) where flat-slab subduction occurred due to the consumption of the Juan Fernández ridge.