The northwestern border of the Caribbean plate in Guatemala: new geological and petrological data on the Motagua Ophiolitic Belt

The Motagua Suture Zone is a complex Mesozoic-Tertiary collisional system ("eo-Caribbean') where several ophiolitic units, representing remnants of a "proto-Caribbean' oceanic domain, occur between the Maya and Chortis continental blocks, to the north and south respectively. Petrographic and geochemical analyses, carried out on the most representative ophiolitic lithotypes have been used to define the magmatic affinity of ophiolites and their original tectonic setting. Low-Ti ophiolitic associations with island arc tholeiitic affinity prevail in the units overthrusting onto the Maya block, whereas pure mid-ocean ridge affinity characterizes ophiolites onto the Chortis block. Paleogeographic reconstruction of the "proto-Caribbean' basin should therefore take into account both MORB and suprasubduction oceanic lithosphere between the Maya and Chortis continental blcoks; they underwent progressive subduction during Upper Cretaceous-Paleocene times, culminating in delamination and obduction...