Rb-Sr ages from La Horqueta Formation, San Rafael Block, Argentina

• Autores: Tickyj, H.; Cingolani, Carlos Alberto; Varela, Ricardo; Chemale Jr, F.
• Año de publicación: 2001
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Geología; Rb-Sr ages; La Horqueta Formation; San Rafael Block; Devonian; Argentina
• Institución: Universidad Nacional de La Plata

The San Rafael Block (SRB) lies in west-central Mendoza province, Argentine (35oS-6830'W), and has SSE-NNW structural cenozoic trends in the pre-Andean region. To the North and South it is bounded by the Cuyo and Neuquen oil basins, respectively. To the East the SRB passes into the Pampean plains vanishing under the modern back arc volcanism and sedimentary cover; to the West the boundary is defined by the Frontal Cordillera. The presence of Grenvillian basement rocks (ca. 1100 Ma) in the Sierras Pampeanas Occidentales, and the Cambrian-Ordovician, mainly carbonatic, sedimentary cover of the Precordillera conform a tectonic terrane of 800 km long, which was named as Occidentalia (Dalla Salda et al., 1992), Precordillera Terrane (Astini et al., 1996) or Cuyania (Ramos, 1995). Geotectonic interpretations based on a large amount of geochronological, paleomagnetical, paleobiogeographical and geological evidences stated that both (basement and carbonatic platform) constitute an alochthonous terrane with laurentian affinities, collided on the proto-Andean margin of South America in Upper Ordovician-Silurian (?) times (Ramos, et al., 1998; Astini, 1998; Pankhurst et al., 1998). Paleontological and geological evidences allow interpreting the SRB as a southern extension of the Precordillera (Keller, 1999). On the eastern part of the SRB have been identified a Grenvillian basement and an Ordovician carbonatic sequence at Ponon Trehue (Bordonaro et al., 1996; Cingolani y Varela, 1999; Keller, 1999), and an Ordovician turbiditic deposits at Cerro Bola (Cuerda and Cingolani, 1998). However, the relation with other pre-Carboniferous units of the SRB with Precordillera, e.g. La Horqueta Fm., Rio Seco de los Castanos Fm., El Nihuil doleritic and gabbroic rocks, is controversial due to the scarce geological, paleontological and geochronological data. We present here, as part of a research project on pre- Carboniferous units from SRB, new Rb-Sr geochronological data from La Horqueta Formation (Dessanti, 1956) that contribute to constrain the timing of the main deformation and low grade metamorphism of this unit (au)
Centro de Investigaciones Geológicas