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Petrografía, geoquímica y geocronología U/Pb en circones de rocas ígneas y metamórficas a lo largo del Río Cuiarí enel sur del Departamento de Guainía, Colombia

Abstract : In order to archive a better understanding of the Rio Negro-Juruena Geochronological Province (1.55-1.8 Ga) ofthe Amazonian Craton in SE-Colombia, we performed analyses of metamorphic, igneous and metasedimentaryrocks outcropping in vicinity of the Cuiarí-River in the south of Guainía Department, near the Brazilianborder. Based on field observations, mineralogical, geochemical and U/Pb LA-ICP-MS analysis in zircons,we could identify in the study area a Statherian basement which forms the Mitú Complex. It is composed by S-type granitoides, mainly monzogranitic to a lesser amount of quartz-monzodioritic to granodioritic, with calc-alkalic metato peraluminosos, syncollisional to post orogenic characteristics and with U/Pb crystallization ages between 1760 to 1800 Ma.Additionally, in the study area more alkalic granitic intrusions with ovoidal K-feldspar phenocrysts forming a porphyritic textureoutcrop where U/Pb zircon data suggest a crystallization age of ~1750 Ma (probably associated to the Tiquié Intrusion Suitedefined in Brazil).Over this Statherian basement, a sedimentary sequence (which may represent the Upper Member of the Tunuí Group in Brazil)was deposited some 1750-1600 Ma ago, where metarenites and quartzites were impregnated by tourmalines as a result of metasomatic processes related to the intrusion of a porphyritic two-mica granite crystalized 1550 to 1600 Ma ago (associated with the Rio Içana Intrusive Suite in Brazil). Some ~1780 Ma old inherited zircons from the Mitú Complex in this intrusion suggest a magma origin by partial melting of cratonic cortical material triggered by sufficient water and low pressures for melting point decrease generating a magma enriched in fluids and incompatible elements like Rb and K. Younger paragneisses withdetrital zircon ages between 1000 to 1800 Ma close the Precambrian geological cycle identified in this area of Colombia. Itsmineralizing potential as well as a tectonic and paleogeographic history still to be deciphered in detail.
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Amed Bonilla, Thomas Cramer, Marc Poujol, Haroold Cano, José Alejandro Franco, et al.. Petrografía, geoquímica y geocronología U/Pb en circones de rocas ígneas y metamórficas a lo largo del Río Cuiarí enel sur del Departamento de Guainía, Colombia. Boletin de geologia, 2019, 41 (1), pp.55-84. ⟨10.18273/revbol.v41n1-2019003⟩. ⟨insu-01977739⟩

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