The Guaviare Complex: new evidence of Mesoproterozoic (ca. 1.3 Ga) crust in the Colombian Amazonian Craton

The Guaviare Complex is a new unit defined in the Colombian Amazonian Craton, which is part of the Precambrian basement located in southeastern Colombia. It is divided into three units according to their textural and compositional characteristics, termed Termales Gneiss, Unilla Amphibolite, and La Rompida Quartzite. Termales Gneiss rocks are petrographically classified as gneisses and quartz-feldspar granofels, with the local formation of blastomylonite-like dynamic rocks. The Unilla Amphibolite consists of only amphibolites, and La Rompida Quartzite consists of muscovite quartzites, quartz-feldspar granofels, and quartz-muscovite schists. The protoliths of Termales Gneiss and Unilla Amphibolite were formed in the Mesoproterozoic at 1.3 Ga due to bimodal magmatism (felsic and mafic) derived from mantle material, with some crust contamination that was probably related to the formation of extensional arcs associated with trans-arc basins in the NW section of the Amazon Craton. La Rompida Quartzite rocks originated from sediments derived from granite rocks and from other, older areas of the craton. These rocks have a maximum age of 1.28 Ga. The low-to-medium grade metamorphism that affected these units occurred from 1.28 to 0.6 Ga, most likely concurrently with the Putumayo orogeny of approximately 1.0 Ga, although it may have been an independent event.