Journal
JOURNAL OF SOUTH AMERICAN EARTH SCIENCES
Volume 98, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsames.2019.102438
Keywords
U-Pb apatite chronology; Apatite fission-track thermochronology; Olivine gabbro; Amazonian craton; Neoproterozoic; Grenvillian
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Funding
- COLCIENCIAS
- Research Foundation Flanders (FWD)
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The 1.80-1.76 Ga crystalline basement in Colombia as part of the W-Amazonian Craton is composed mainly of gneisses, granitoids and migmatites, affected later by several compressive and extensional events resulting for example in A-type granites, but also mafic intrusions and dikes. Here we present, after a revision of main geological features, research results obtained on the NW-SE trending ilmenite-apatite-rich Cafio Viejita gabbro in the SW-Vichada department some 500 km east of Bogota. Petrographic and geochemical data hint to a metaluminous continental alkaline gabbro enriched in K, Ti and P, possibly due to continental crust reworking or magma mixing, as also confirmed by trace elements characteristics in the apatites like HREE enrichment (Ce/Yb)(cn), 12-13, negative Eu-anomaly, and Y, Th, Sr, Mn ratios. LA-ICP-MS U-Pb apatite geochronology suggests an early Neoproterozoic emplacement age between 975 +/- 9 and 1002 +/- 21 Ma related with rifting triggered by the Amazonia-Baltica-Laurentia collision during the Rodinia Supercontinent assembly and associated Grenvillian events. These events also caused mafic intrusions in other parts of the craton. Apatite fission track thermochronometry and thermal history modelling on one sample suggest the onset of the final exhumation stage during Jurassic (similar to 180 Ma), which brought the rocks slowly to their current outcrop position.
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