Abstract

RODRIGUEZ-GARCIA, Gabriel et al. Contributions to the knowledge of plutonism of the Mocoa-Santa Marta Arc during the Early - Middle Jurassic, on the northwestern margin of the Andes, Colombia. Bol. geol. [online]. 2020, vol.42, n.3, pp.15-50.  Epub Aug 31, 2020. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v42n3-2020001.

Based on the integration of field information with petrographic, whole rock geochemical, isotopic and geochronological data, a comparison of the different tectonic blocks that make up the Mocoa-Santa Marta Arc (AMSM) was made. This arc, which crops out in the Upper Magdalena Valley, La Serranía de San Lucas, La Sierra Nevada de Santa Marta and La Alta Guajira, was emplaced in a Neo-proterozoic basement and in granitoids of a Permian arc, which were later dispersed along the South American Paleomargin. The plutonism of the AMSM is characterized by a compositional migration in the W-E direction, with the formation of intrusive quartz monzonite, monzonite, charnockite, tonalites and granodiorites intrusions to the west and the formation of monzogranite and syenogranite plutons towards the east; there is also an enrichment in SiO2 in the S-N direction. AMSM plutons crystallized between the Early Jurassic (~193 Ma) and middle Jurassic (~164 Ma), and were generated by at least four crystallization events. The plutons that make up this arc are I-type, calc-alkaline, with slight variation toward calcium alkaline granitoids. The oldest and western plutons are mostly metaluminous and the youngest and eastern plutons are peraluminous, all formed within the same context of magmatic evolution of an erosive continental margin arc with associated vulcanism. The zircon crystallization temperature (TzircTi) for all western plutons has a crystallization peak at 860°C, while the eastern belt plutons have TzircTi crystallization peaks at 714°C, 807°C and 854°C, with a high dispersion.

Keywords : Jurassic Magmatism; U-Pb dating; Colombia; Chibcha Terrain.

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