Late Triassic to Jurassic Magmatism in Colombia: Implications for the Evolution of the Northern Margin of South America

Volcanic and plutonic rocks that compose the Late Triassic to Jurassic magmatic belt in Colombia result from partial melting of lower crustal rocks mixed with mantle melts in a continental margin setting. Lithologies include quartz monzonites, monzogranites, syenogranites (locally leucocratic), granodiorites, tonalites, diorites, gabbros, and volcaniclastic successions intersected by porphyritic hypabyssal rocks of andesitic, dacitic, and latitic compositions. The elongated geometry of plutons suggests that the accommodation spaces of magmatic pulses were related to transtensional environments in a supra–subduction tectonic framework with mantle interaction, melting of slab sediments, and crustal contamination. The nature of magmatism resulted from interactions between crustal and mantle–derived magmas in a continental margin setting that progressively changed from Late Triassic postcollisional extension (associated with orogenic collapse?) to a predominantly Late Jurassic volcanic arc developed in a supra–subduction regime; the evolution of the magmatic belt is marked spatially from east to west and temporally over a time span of approximately 60 my. The sources of the Late Triassic to Jurassic magmatic belt are varied and associated with melting of the supra–subduction mantle wedge and differentiation of tholeiitic or mildly calc–alkaline basalts and intermediate rocks and include partial melting of pelitic rocks, tonalites, granodiorites, tholeiites, and high–aluminum basalts or andesites.