Paleomagnetic evidence of the brittle deformation of the Central Patagonian Batholith at Gastre area (Chubut Province, Argentina)

• Autores: Ruiz González, Víctor; Puigdomenech Negre, Carla G.; Zaffarana, Claudia Batriz; Vizán, Haroldo; Somoza, Rubén
• Año de publicación: 2020
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Geofísica; Gastre Fault System; Andean Orogeny; Tectonic Inversion; Gastre Basin; Geofísica
• Institución: Universidad Nacional de Río Negro

Fil: Ruiz González, Víctor. Universidad de Buenos Aires. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Buenos Aires, Argentina.
Fil: Puigdomenech Negre, Carla G. Universidad de Buenos Aires. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Buenos Aires, Argentina.
Fil: Zaffarana, Claudia B. Universidad Nacional de Río Negro. Instituto de Investigación en Paleobiología y Geología. Río Negro, Argentina.
Fil: Vizán, Haroldo. Universidad de Buenos Aires. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Buenos Aires, Argentina.
Fil: Somoza, Rubén. Universidad de Buenos Aires. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Buenos Aires, Argentina.
Fil: Ruiz González, Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: Puigdomenech Negre, Carla G. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: Zaffarana, Claudia B. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: Vizán, Haroldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
Fil: Somoza, Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Buenos Aires, Argentina.
The Central Patagonian Batholith (CPB) in the Gastre area, central Patagonia, constitutes a set of two I-type Late Triassic plutonic suites, the Gastre superunit with a U-Pb zircon age of 221 ± 2 Ma, and the Lipetrén superunit with a U-Pb SHRIMP age of 215 ± 1 Ma. The source of this calc-alkaline batholith is characterized by crustal and mantle contributions, and it registers NW-SE subvertical magmatic and solid-state fabrics. These features, together with its intraplate position away from the inferred proto-Gondwana margin, have made it the focus of different tectonic interpretations. Early studies have interpreted it as the record of major dextral motions along the transcontinental NW-SE-striking Gastre fault system in Jurassic times. Later interpretations have proposed that the magmatic and tectonic foliations of the CPB were formed during a sinistral transpressive regime which was aided by Late Paleozoic widespread NW-SE subvertical structures in the North Patagonian Massif. Paleomagnetism, a unique tool to detect the presence of tectonic block rotations on vertical axes, was applied in the CPB in order to constrain the timing and type of deformation in the area. A paleomagnetic pole was obtained, which statistical parameters are: N = 45, Lat. = 81.4°S, Long. = 207°E, K = 11.5, A95 = 6.6°. Although the position of this pole does not coincide with equivalent Late Triassic poles, this position can be reconciled with the presence of a NE tilting of about 11° of the sampled block of the batholith. The tilting would have been aided by the NW-SE subvertical structures that affect the area. These paleomagnetic results rule out the possibility of vertical axis rotations from Late Triassic to present times and suggest that the ductile syn- to post-emplacement deformation of the CPB in Gastre area occurred during this period (Late Triassic), being the later brittle deformation triggered by the Andean Orogeny a possible explanation for this tilting.
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