Contents lists available at ScienceDirect Journal of South American Earth Sciences journal homepage: www.elsevier.com/locate/jsames Apatite LA-ICP-MS U–Pb and fission-track geochronology of the Caño Viejita gabbro in E-Colombia: Evidence for Grenvillian intraplate rifting and Jurassic exhumation in the NW Amazonian Craton Amed Bonilla a,∗ , Jose A. Franco a , Thomas Cramer a , Marc Poujol b , Nathan Cogné b , Simon Nachtergaele c , Johan De Grave c a Geoscience Department, National University of Colombia, Bogotá, Colombia b Universitè de Rennes, CNRS, Géosciences Rennes - UMR 6118, F-35000, Rennes, France c Department of Geology, Ghent University, Krijgslaan 281.S8, WE13, 9000, Ghent, Belgium ARTICLE INFO Keywords: U-Pb apatite chronology Apatite fission-track thermochronology Olivine gabbro Amazonian craton Neoproterozoic Grenvillian ABSTRACT 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 Caño Viejita gabbro in the SW-Vichada department some 500 km east of Bogota. Petrographic and geochemical data hint to a meta- luminous 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 thermo- chronometry and thermal history modelling on one sample suggest the onset of the final exhumation stage during Jurassic (~180 Ma), which brought the rocks slowly to their current outcrop position. 1. Introduction The Amazonian Craton is one of the largest Precambrian continental nuclei in the world comprising huge parts of NW-South America, mainly in Brazil, but also in Venezuela, Guyana, Suriname, French Guyana and NE-Colombia. It formed during the Paleo-Mesoproterozoic due to several accretion events, was affected by extensional and crust consuming episodes, which all resulted in complex geochronological provinces (Fig. 1). These provinces have been (re)defined and refined over the last years and the exact positions of their boundaries are still a matter of debate (Cordani et al., 2009, 1979; Kroonenberg, 2019; Santos et al., 2000; Tassinari and Macambira, 1999; Teixeira et al., 1989). The NW Amazonian Craton that outcrops in Eastern Colombia yields ages between ~1.86–1.70 Ga and is defined as part of the Mitú Migmatitic Complex (Galvis et al., 1979; Rodriguez et al., 2011) or better the Mitú Complex (Bonilla et al., 2019; López et al., 2007). This Mitú Complex is itself a portion of the 1.86–1.55 Ga Rio Negro-Juruena Geochronological Province (Tassinari et al., 1996; Tassinari and Macambira, 1999). Older (~1.98 Ga) metavolcanic rocks of the Ata- bapo-Río Negro Gneiss may testify remains of the Trans-Amazonian basement (Kroonenberg, 2019) and not of the Mitú Complex accretion. This complex was affected by several magmatic and tectonic episodes during the Mesoproterozoic (1.6–1.0 Ga), among them (in Colombia 1.40–1.34 Ga) intraplate A-type granite emplacements like the Par- guaza and Matraca rapakivi granites (Bonilla et al., 2013, 2016; Gaudette et al., 1978) and the Nickerie-K’Mudku thermal event 1.3–1.0 Ga ago deduced from far-reaching K/Ar and Rb/Sr ages reset- ting. The youngest of the geochronological Amazonian Craton provinces identified hitherto is the 1.25–1.0 Ga old Sunsás Province (Fig. 1), a late Mesoproterozoic collisional metamorphic belt in the southwestern margin of the Amazonian Craton which constitutes an important pa- leogeographic link between the late Meso- and the early Neoproter- ozoic, when Amazonia, Baltica and Laurentia became part of the https://doi.org/10.1016/j.jsames.2019.102438 Received 10 September 2019; Received in revised form 21 November 2019; Accepted 21 November 2019 ∗ Corresponding author. Calle 23c # 69f-65 Int 27 Apto 502, Colombia. E-mail address: abonillape@unal.edu.co (A. Bonilla). Journal of South American Earth Sciences 98 (2020) 102438 Available online 26 November 2019 0895-9811/ © 2019 Elsevier Ltd. All rights reserved. T