The petrology and geochemistry of Cretaceous to Recent volcanism in Colombia: the magmatic history of an accretionary plate margin

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Abstract
The Pacific margin of Colombia records a complex history of subduction-related magmatism from at least Cretaceous times. Cretaceous lavas from the Western Cordillera and part of the Central Cordillera of the Colombian Andes exhibit some chemical characteristics typical of island-arc tholeiites, including low LIL-element abundances and flat to light depleted REE patterns, but also have chemical and geological affinities with deposits from marginal basins, and with transitional type ocean floor basalts. An appraisal of the geological and chemical evidence leads to the conclusion that these rocks were erupted in an oceanic environment in close proximity to the continent. A suite of basic rocks from the Coastal Cordillera of Upper Cretaceous to Tertiary age has been interpreted elsewhere as abyssal tholeiites. Following accretion of the Cretaceous sequences on to cratonic S America, volcanism continued in the upper Miocene with the eruption of basalts and basaltic andesites on the eastern flanks of the Western Cordillera. This tholeiitic suite is LREE and LIL-element enriched compared with the Cretaceous lavas, and represents the trenchward portion of an ensialic island-arc sequence. Subduction-related magmatism continued from the Miocene with the formation of composite calc-alkaline strato-volcanoes, mostly along the axis of the Central Cordillera. These Miocene to Recent lavas are dominantly andesitic, with strong LIL and LREE enrichment and 87 Sr/ 86 Sr ratios of 0.7042:0.7047.