The Colombian magmatic record of the Panama arc collision and subduction of the Nazca plate
Abstract
During the Neogene, northwestern South America experienced a major plate tectonic re-organization of the margin and the subduction zone triggered by the accretion of the Panama-Choco oceanic arc. Here we examine the spatio-temporal and compositional character of Miocene magmatic rocks emplaced both in the accreted Panama arc and the South American margin in Colombia as a tectonic tracer of these events.
New U-Pb geochronology from intermediate to mafic plutonic rocks emplaced in the axis and western flank of the Colombian Western Cordillera (El Botón arc) yielded magmatic crystallization ages between 8.5 and 11.5 Ma, which partially overlap with published Ar-Ar data from related plutonic and volcanic rocks. The compositional character of these rocks reveal evidence of relatively dry mantle melting as suggested by their more tholeiitic character when compared with the more calc-alkaline character of the ca. 11-5 Ma arc-related magmatism exposed inboard the continent (Combia Formation). El Botón magmatism also reveals an enrichment in the LREE and depletion in the HREE (La/Yb(N) 1.5-13 and La/Sm(N) 0.6-5.2) that can be related to lower degree of partial melting and deeper seated fractionation than the younger Combia magmas. This magmatic record temporally restricts the accretion of the Panama-Choco arc to ≥ 12 Ma, and also represents the characteristic signature of early-arc magmatism as the Nazca plate re-initiated its subduction under the continental margin of northwestern Colombia.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T13B..04C
- Keywords:
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- 1099 General or miscellaneous;
- GEOCHEMISTRY;
- 1199 General or miscellaneous;
- GEOCHRONOLOGY;
- 8199 General or miscellaneous;
- TECTONOPHYSICS;
- 8499 General or miscellaneous;
- VOLCANOLOGY