Examinando por Autor "Bernet M."
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Ítem Late Cenozoic to modern-day volcanism in the Northern Andes: A geochronological, petrographical, and geochemical review(Springer Verlag, 2019-01-01) Marín-Cerón M.I.; Leal-Mejía H.; Bernet M.; Mesa-García J.The Northern Andean Block is the result of complex tectonic interaction between the Farallon-Nazca, South American, and Caribbean Plates. Abundant late Cenozoic volcanism (and associated hypabyssal porphyritic plutonism), beginning in the mid- to late Miocene, is the result of subduction-related mantle-derived magmatic activity, superimposed upon a compositionally varied and structurally complex basement during the late stages of the Northern Andean orogeny. Tectonic consolidation and subduction of the segmented Nazca Plate during the late Miocene-Pliocene led to conformation of the modern-day Colombian segment of the Northern Andean Volcanic Zone. The Colombian arc segment represents the northernmost expression of subduction-related volcanism within South America’s Andean Cordillera. © Springer Nature Switzerland AG 2019.Ítem Thermochronological, petrographic and geochemical characteristics of the Combia Formation, Amagá basin, Colombia(PERGAMON-ELSEVIER SCIENCE LTD, 2020-01-01) Bernet M.; Mesa Garcia J.; Chauvel C.; Ramírez Londoño M.J.; Marín-Cerón M.I.; Bernet M.; Mesa Garcia J.; Chauvel C.; Ramírez Londoño M.J.; Marín-Cerón M.I.; Universidad EAFIT. Departamento de Ciencias; Geología Ambiental y TectónicaThe Amagá basin between the Western and Central Cordilleras of the Northern Andes of Colombia hosts the Neogene volcanic and volcaniclastic Combia Formation. Deposition of the Combia Formation in relation to Nazca plate subduction and arc volcanism is still a matter of debate. Therefore, the timing, petrography and geochemical characteristics of Combia Formation rocks were studied in the western and eastern parts of the Amagá basin, in order to gain more information on the type of magma generation and volcanic activity that led to the deposition of the Combia Formation. Apatite and zircon fission-track dating largely confirm a 12-6 Ma age for the deposition of the Combia Formation. Petrographic and major element analyses show that mainly trachy-andesite ignimbrites with a calc-alkaline composition were deposited in the western Amagá basin, whereas the volcanic rocks of the eastern Amagá basin are lavas flow and fall-out deposits of basaltic andesites of tholeiitic affinity. Trace element and isotopic analyses show that slab dehydration and sediment melting/decarbonation were important in primary magma generation in the mantle wedge, but the primary magma was mixed with lower continental crustal melts (e.g. High-Pb radiogenic), resulting in characteristic isotope signatures in the western and eastern Amagá basin. Then, the hot-zone developed a high Pb-radiogenic, garnet-bearing lower continental crustal (LCC) level as a consequence of the quantity of dehydration of the subducting slab and of changes in the tectonic regime. An extensional pull-apart event (12- 9 Ma), likely facilitated rapid magma ascend to the uppermost crust along a subvertical magma plumbing system throughout the Romeral Fault zone in the eastern Amagá basin, and calc-alkaline magmas with adakite-like signature, which may indicate contractile tectonics that allow the formation of middle-to upper-crustal magma chambers with a garnet fractionation at depth and the evolution of silicate melts into the hot zone mainly related to the amount of water (>4 wt %) present. © 2020 Elsevier Ltd