34 Ore Deposits and Ore Genesis in the American Cordillera

Saturday, 31 March 2012
8:30 AM - 12:50 PM
Goyesco 1

METALLOGENIC AND TECTONOMAGMATIC EVOLUTION OF MEXICO DURING THE MESOZOIC: A REVIEW AND NEW INSIGHTS

Paper number: 34-9
Program: Theme Sessions
Time: 11:10 AM – 11:30 AM

Authors

Abstract

The Mesozoic types of ore deposits in Mexico belong to various realms. The magmatic oceanic realm includes volcanogenic massive sulfide or VMS, and various types of deposits hosted by ultramafic-mafic complexes. The magmatic continental realm includes various types of magmatic-hydrothermal iron oxide deposits (IOCG ‘clan’), deposits of the extended porphyry-type family, and skarns. The orogenic-metamorphic realm includes orogenic/lode gold deposits. The sedimentary-diagenetic includes MVT and SEDEX deposits, sedimentary phosphorites, and clastic sequence-hosted Cu-Co or U deposits. Three main Mesozoic metallogenic epochs in Mexico are hereby proposed: (1) Triassic to Middle Jurassic, ill defined, (2) Oxfordian to Albian-Cenomanian, and (3) Albian-Cenomanian to Maastrichtian, which continues and booms into the Paleocene. In these epochs, no less than twelve metallogenic provinces or belts are regionally defined. The departure from the magmatic oceanic realm of ore deposits to the continental occurs between the mid-Aptian and the mid-Cenomanian, and their recognizable belts are recorded in the southern and northern Pacific margin of Mexico, respectively.

Nearly all of the Mesozoic VMS deposits respond to the Kuroko-type model, and most of them occur in volcanosedimentary sequences close to terrane boundaries, especially along those of the southern Guerrero composite terrane (GCT) and mostly within it. However, new evidence suggests that they occur within the Sierra Madre terrane as well. This is compatible with their formation in back-arc settings between volcanic arcs, epicontinental seas and positive lands of eastern Mexico, or within juvenile and slightly evolved arcs. Contrastingly, no VMS deposits are known to occur in the northern half of the GCT, as the widespread extensional unroofing in the south did not seemingly propagate northwards. An important feature for the metallogeny of the Late Cretaceous and the Cenozoic is that the reactivation of crustal-scale discontinuities controlled the emplacement of shallow intrusives, volcanism, and also hydrothermal fluids from magmatic, meteoric or basinal sources. Thus, ore deposits of either the magmatic continental or the sedimentary-diagenetic realms were bound to such control despite being mutually exclusive realms.