New Ages and Geochemical Data for Gorgona Island, Colombia: A 27 Ma Long History of Mantle Melting in the Formation of the Caribbean Large Igneous Province
Located 50 km off the Pacific coast of Colombia, Gorgona is a tectonic fragment affected by reverse and oblique faulting with a general E to NE vergence, which exposes an ultramafic suite including the world youngest known komatiites. Previous works yielded ages of ~89 Ma (Ar-Ar) and a large spread in radiogenic isotopes and incompatible trace element ratios. More recently it was proposed that the island does not belong to CLIP but would be the result of a plume whose present expression is the Salas y Gomez hotspot (Kerr and Tarney, 2005).
Using laser step heating, we obtained high quality Ar-Ar ages for basalts and gabbros whose range overlap that reported for the CLIP and the western coast of Colombia (92-65 Ma). Our age-controlled geochemical data displays a secular variation from enriched to more depleted composition, shows substantial differences with respect to Salas y Gómez and Galápagos, and overlap with the more primitive CLIP rocks. Accordingly, we propose that Gorgona is part of the CLIP and was produced by several magmatic pulses with progressively higher grades of mantle melting. Thus our results seem to fit better in a scenario of progressive opening of a slab window within an intraoceanic subduction system.