Permo-Triassic metamorphism in the Mérida Andes, Venezuela: new insights from geochronology, O-isotopes, and geothermobarometry
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...
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| Main Authors: | , , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
26 September 2020
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| In: |
International journal of earth sciences
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| ISSN: | 1437-3262 |
| DOI: | 10.1007/s00531-020-01926-5 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1007/s00531-020-01926-5
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| Author Notes: | M. Daniela Tazzo-Rangel, Bodo Weber, Axel K. Schmitt, Reneé González-Guzmán, Alejandro Cisneros de León, Lutz Hecht |
| Summary: | 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. |
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| Item Description: | Gesehen am 30.06.2021 |
| Physical Description: | Online Resource |
| ISSN: | 1437-3262 |
| DOI: | 10.1007/s00531-020-01926-5 |