Abstract
The Sierra de Pie de Palo (SPP, Western Sierras Pampeanas) shows evidence of two regional metamorphisms: one Mesoproterozoic attributed to the Grenvillian orogeny and other of Ordovician age related to the Famatinian orogeny. The Neoproterozoic-to-Cambrian sedimentary successions that cover the Grenvillian basement only record the Ordovician event. One staurolite-schist from the Ediacaran Difunta Correa Metasedimentary Sequence collected in the southeastern side of the SPP allows to constrain, by means of pseudosections, a prograde evolution from ca. 3 kbar and 515 ºC up to ca. 9 kbar and 640 ºC corresponding to a high P/T gradient. The SPP and the immediately east Loma de Las Chacras outcrop were part of the famatinian forearc which shows a progressive decrease of P (from ca. 13 kbar to 6 kbar), T (from ca. 900 ºC to 450 ºC), and P/T gradient (from ca. 85 ºC/kbar to 35 ºC/kbar) towards the active continental margin on the west. The Caucete Group, in the western side of the SPP, represents the westernmost part of the forearc, near to the active continental margin. Metamorphism was apparently coeval with the Famatinian magmatism and with ductile underthrusting at ca. 470-465 Ma, which led to burial of the forearc beneath the magmatic arc.
Highlights
Las Sierras Pampeanas de Argentina constituyen un laboratorio natural excepcional donde se exponen rocas asociadas a procesos geológicos atribuidos a la formación y ruptura del supercontinente Rodinia (Meso-Neoproterozóico; e.g., Vujovich y Kay, 1998; Baldo et al, 2006; Colombo et al, 2009; Rapela et al, 2010; Varela et al, 2011) y a la formación de Gondwana (Neoproterozoico-Paleozoico Inferior; e.g., Rapela et al, 1998)
The Sierra de Pie de Palo (SPP, Western Sierras Pampeanas) shows evidence of two regional metamorphisms: one Mesoproterozoic attributed to the Grenvillian orogeny and other of Ordovician age related to the Famatinian orogeny
One staurolite-schist from the Ediacaran Difunta Correa Metasedimentary Sequence collected in the southeastern side of the SPP allows to constrain, by means of pseudosections, a prograde evolution from ca. 3 kbar and 515 oC up to ca. 9 kbar and 640 oC corresponding to a high P/T gradient
Summary
Las Sierras Pampeanas de Argentina constituyen un laboratorio natural excepcional donde se exponen rocas asociadas a procesos geológicos atribuidos a la formación y ruptura del supercontinente Rodinia (Meso-Neoproterozóico; e.g., Vujovich y Kay, 1998; Baldo et al, 2006; Colombo et al, 2009; Rapela et al, 2010; Varela et al, 2011) y a la formación de Gondwana (Neoproterozoico-Paleozoico Inferior; e.g., Rapela et al, 1998). La Sierra de Pie de Palo (SPP) corresponde a una de las sierras más occidentales de las Sierras Pampeanas, ubicada entre la Precordillera al oeste y las rocas del arco magmático famatiniano aflorantes en la Sierra de Valle Fértil-La Huerta al este (Fig. 1). 1.000-1.300 Ma; McDonough et al, 1993; Rapela et al, 2010 y referencias allí citadas), una cubierta metasedimentaria ediacarense de afinidad lauréntica (Galindo et al, 2004; Ramacciotti et al, 2015a, b; Rapela et al, 2016) y rocas ígneas y metamórficas ordovícicas (Casquet et al, 2001; Mulcahy et al, 2011; Baldo et al, 2012) que contribuyen al entendimiento de procesos orogénicos ocurridos entre el Mesoproterozoico y el Paleozoico inferior en este sector de Sudamérica.
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