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Título:
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O–H–Sr–Nd isotope constraints on the origin of the Famatinian magmatic arc, NW Argentina
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Autores:
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Alasino, Pablo H. ;
Casquet, César ;
Galindo Francisco, Mª del Carmen ;
Pankhurst, R.J. ;
Rapela, Carlos W. ;
Dahlquist, Juan A. ;
Recio, C. ;
Baldo, Edgardo G. ;
Larrovere, Mariano Alexis ;
Ramacciotti, Carlos
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Tipo de documento:
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texto impreso
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Editorial:
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Cambridge University Press, 2020
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Dimensiones:
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application/pdf
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Nota general:
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info:eu-repo/semantics/restrictedAccess
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Idiomas:
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Palabras clave:
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Estado = Publicado
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Materia = Ciencias: Geología: Geoquímica
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Materia = Ciencias: Geología: Petrología
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Tipo = Artículo
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Resumen:
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We report a study of whole-rock O–H–Sr–Nd isotopes of Ordovician igneous and metamorphic rocks exposed at different crustal palaeodepths along c. 750 km in the Sierras Pampeanas, NW Argentina. The isotope compositions preserved in the intermediate rocks (mostly tonalite) (average ?18O = +8.7 ± 0.5‰, ?D = ?73 ± 14‰, 87Sr/86Srt = 0.7088 ± 0.0001 and ?Ndt = ?4.5 ± 0.6) show no major difference from those of most of the mafic rocks (average ?18O = +8 ± 0.8‰, ?D = ?84 ± 18‰, 87Sr/86Srt = 0.7082 ± 0.0016 and ?Ndt = ?4 ± 1.1), suggesting that most of their magmas acquired their crustal characteristics in the mantle. The estimate of assimilation of crustal material (?18O = +12.2 ± 1.7‰, ?D = ?89 ± 21‰, 87Sr/86Srt = 0.7146 ± 0.0034 and ?Ndt = ?6.9 ± 0.7) by the tonalite is in most samples within the range 10–20%. Felsic magmas that reached upper crustal levels had isotope values (?18O = +9.9 ± 1.5‰, ?D= ?76 ± 5‰, 87Sr/86Srt = 0.7067 ± 0.0010, ?Ndt = ?3.5 ± 1.4) suggesting that they were not derived by fractionation of the contaminated intermediate magmas, but evolved from different magma batches. Some rocks of the arc, both igneous (mostly gabbro and tonalite) and metamorphic, underwent restricted interaction with meteoric fluids. Reported values of ?18O of magmatic zircons from the Famatinian arc rocks (+6 to +9‰) are comparable to our ?18O whole-rock data, indicating that pervasive oxygen isotope exchange in the lower crust was not a major process after zircon crystallization.
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En línea:
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https://eprints.ucm.es/id/eprint/60722/1/O%E2%80%93H%E2%80%93Sr%E2%80%93Nd%20isotope%20constraints%20on%20the%20origin%20of%20the%20Famatinian%20magmatic%20arc.pdf
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