Early Cretaceous alkaline volcanism of the Sierra Chica de Cordoba (Argentina): Mineralogy, geochemistry and petrogenesis

Distinct groups of volcanic rocks, mainly of potassic character, were recognized from the different localities of the Sierra Chica de Cordoba (SCC) (1) alkali basalt to trachyte suite, (2) transitional basalt to latibasalt suite and (3) basanites. Magma evolution would have taken place at crustal level(s) from distinct parental magmas, mainly through fractional crystallization in an open system magma chamber. Source composition supports garnet and phlogopite as residual phases in the mantle. Melting degrees (5-7%) from an enriched mantle source are in accordance with the peripheral position related to the great thermal anomaly that triggered the voluminous Parana flood tholeiites. SCC volcanism is of high-Ti, with multi-elemental patterns similar to those from Alto Paranaiba (Brazil) and clearly distinct from the ones of low-Ti provinces, as Eastern Paraguay. Though associated with a mobile belt of the Pampean Crogeny, volcanism of SCC does not reveal compositional features that can be related to slab-derived mantle meta-somatism, so that the small-scale heterogeneity of the SCC lithospheric mantle source must be related to enrichment events involving volatile-rich small-volume melts from the asthenosphere. (C) 2008 Elsevier Ltd. All rights reserved.