Permo-Triassic metamorphism in the Mérida Andes, Venezuela

• Verfasst von: Tazzo-Rangel, M. Daniela [VerfasserIn]
• Verfasst von: Weber, Bodo [VerfasserIn]
• Verfasst von: Schmitt, Axel Karl [VerfasserIn]
• Verfasst von: González-Guzmán, Reneé [VerfasserIn]
• Verfasst von: Cisneros de León, Alejandro [VerfasserIn]
• Verfasst von: Hecht, Lutz [VerfasserIn]
• Titel: Permo-Triassic metamorphism in the Mérida Andes, Venezuela
• Titelzusatz: new insights from geochronology, O-isotopes, and geothermobarometry
• Verf.angabe: M. Daniela Tazzo-Rangel, Bodo Weber, Axel K. Schmitt, Reneé González-Guzmán, Alejandro Cisneros de León, Lutz Hecht
• E-Jahr: 2020
• Jahr: 26 September 2020
• Umfang: 29 S.
• Illustrationen: Diagramme, Karten
• Fussnoten: Gesehen am 30.06.2021
• Titel Quelle: Enthalten in: International journal of earth sciences
• Ort Quelle: Berlin : Springer, 1999
• Jahr Quelle: 2020
• Band/Heft Quelle: (2020)
• ISSN Quelle: 1437-3262
• DOI: doi:10.1007/s00531-020-01926-5
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1761638947

Abstract

Although there is a consensus about Pangea assemblage in northwestern Gondwana spanning from the Late Carboniferous to the Early Permian, the tectonics of the Permo-Triassic period, including the onset of Pangea breakup, is still controversial. In this context, three regional tectonic features need to be considered: (1) The Ouachita-Marathon-Sonora suture, (2) east-dipping subduction of the Panthalassa oceanic crust beneath Gondwana, and (3) an extensional setting documented in Colombia, Ecuador, and México suggesting Pangea breakup at ca. 240-220 Ma. A chemical, isotopic, and geochronological dataset is presented in this contribution to constrain the effects of these tectonic processes in the metamorphic basement of the Mérida Andes in western Venezuela. U-Pb Secondary Ion Mass Spectrometry analyses on unpolished surfaces of zircons from orthogneisses yielded an average age of 251 ± 4 Ma. The corresponding δ18O values suggest metamorphic recrystallization of zircon instead of high-T fluid interaction. Rb-Sr and Sm-Nd geochronology in white mica and garnet yielded ages of 234 ± 3 Ma and 249 ± 2 Ma, respectively, whereas a younger Rb-Sr date of 197 ± 1 Ma was obtained from biotite. U-Pb and Sm-Nd ages constrain the latest Permian-earliest Triassic metamorphism in the Mérida Andes at 251 ± 4 Ma. Geothermobarometry data suggest amphibolite-facies peak metamorphic conditions at ~ 685 °C and ~ 6.0 kbar. Metamorphism might be related to post-orogenic collapse, after the collision of Gondwana and Laurentia to form Pangea. Rb-Sr ages suggest retrogression and cooling, possibly caused by thermal relaxation of a tectonically overthickened crust and onset of extensional setting, followed by Pangea breakup during the Late Triassic-Early Jurassic.