Early Cretaceous Volcanism in Eastern Argentina

Abstract

Volcanic rocks of Parana Magmatic Province (PMP) are mostly located within the area of the intracratonic Parana basin and covered an extensive region of Brazil, Paraguay, Uruguay and north-eastern Argentina. In the latter, the main outcrops are located in Misiones and Corrientes provinces, while a thick volcanic pile remains buried under the surface of Entre Rios Province and in Chaco–Parana basin (southern Parana). The geochemical data presented here complement those published by other authors. In Misiones Province, rocks are tholeiitic lavas of high- and low-Ti varieties, whereas to the south, in Corrientes Province, lavas of low-Ti types prevail. Cu contents are high, comparable to those reported from lavas of Brazil. Evolution of HTi and LTi magmas must have occurred from two different parental magmas through fractional crystallization at low pressures, involving crustal contamination only for the Gramado variety, in agreement with the general trend recognized in the PMP. Geochemical features point out that different ancient subduction processes could have affected the source of the PMP basalts from Misiones Province, as those that occurred during Late Proterozoic–Early Cambrian associated to Paraguay belt, as well as even older ones related to the Nico Perez terrane.