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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Isotopic and thermochronologic evidence of extremely cold lithosphere associated with a slab flattening in the Central Andes of Argentina

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Autor(es):
Collo, Gilda ; Davila, Federico M. ; Teixeira, Wilson ; Nobile, Julieta C. ; Sant Anna, Lucy G. ; Carter, Andrew
Número total de Autores: 6
Tipo de documento: Artigo Científico
Fonte: BASIN RESEARCH; v. 29, n. 1, p. 16-40, FEB 2017.
Citações Web of Science: 6
Resumo

We present mineralogic, isotopic and thermochronologic analyses on psammopelitic and tuffaceous levels from the Bermejo and Vinchina basins - both foreland depocentres of the Central Andes of Argentina - that define a low-temperature regime for the crust akin to a slab shallowing and flattening process. The contents of illite in illite/smectite interstratified (I/S) show a progressive illitization into the deeper parts of both basins. The distribution of I/S is compatible with theoretical simulations and predicted heat flow values of ca. 26 mW m(-2) in the 8-3.4 Ma interval for the Vinchina Basin and ca. 42 mW m(-2) since 9 Ma for the Bermejo Basin. The latter shows heat flow values that are comparable to those reported by magnetotelluric analysis (36-40 mW m(-2)) in agreement with previously published heat flow calculations along the modern Andean foreland. The Rb-Sr isochrones in psammopelites (< 2 mu m fractions) show ages between 125 and 165 Ma, whereas the K-Ar ages decrease as the grain size is smaller (136-224 Ma for 1-2 mu m, 112-159 Ma for 0.2-1 mu m, 76-116 Ma for < 0.2 mu and 39.3-42 Ma for < 0.1 mu m). These ages are significantly older than the sedimentation in the basins (ca. 16 Ma for the Vinchina Basin; U-Pb age), and can be explained by the presence of a significant amount of detrital components, mainly illite, even in the finer fractions. The preservation of detrital ages is consistent with the shallow diagenesis related to a low-temperature regime, proposed here for the basins. Younger K-Ar ages (21.3-12 Ma) were obtained for a basal tuffaceous level. Clay mineralogy and R0 ordering in the deepest part of the Vinchina Basin, together with the evolution model of I/S with depth, suggest that the burial temperatures would have not exceeded ca. 100 degrees C in agreement with (U-Th)/He analyses performed on apatite extracted from two tuffaceous units. Thermal indicators from both studied basins confirm the existence of a low-temperature regime during flat subduction. (AU)

Processo FAPESP: 10/52172-1 - Caracterização isotópica de bacias sedimentares espessas com base em interpretações K-Ar, 40Ar-39Ar e Rb-Sr em argilominerais: implicações para a trajetória de soterramento e estimativa de paleogradientes geotérmicos
Beneficiário:Wilson Teixeira
Linha de fomento: Auxílio à Pesquisa - Regular