EARLY CRETACEOUS VOLCANISM IN CENTRAL AND EASTERN ARGENTINA DURING GONDWANA BREAK-UP

LAGORIO SILVIA L.; VIZÁN HAROLDO; GEUNA SILVANA E.

Springer

Año: 2015 p. 144

978-3-319-29591-6

The objective of this contribution is to analyse the geochemistry, petrogenesis andgeodynamics of the Early Cretaceous volcanism in Argentina, mainly located inCórdoba and Misiones provinces, during the break-up of Gondwana.In Córdoba (central Argentina), the analysed volcanic rocks are outcropping inSierra Chica and different groups of lithological types were recognized in variouslocalities. These are mainly alkaline basalts that reflect a lithospheric mantle source.In Misiones (north-eastern Argentina), the volcanic rocks are tholeiitic basaltsand belong to Paraná Magmatic Province (PMP) which is regionally extended inSouth America and has a counterpart in Africa (in the localities of Etendeka andAngola). This large igneous province (LIP) has been widely studied by severalauthors, and different models have been considered to explain its origin. Datingobtained by various methodologies (40Ar/39Ar, U?Pb, and Re?Os isochrons) andthat were published in different studies indicate an Early Cretaceous age between131.6 ± 2.3 and 134.7 ± 1 Ma for PMP. Anyway, interbedded acid volcanic rocksyielded even 137.3 ± 1.8 Ma.A new 40Ar/39Ar age of 129.6 ± 1 Ma from an alkaline rock of Sierra Chica ofCórdoba (SCC) presented in this contribution, points out that this volcanism wasslightly posthumous in relation to PMP.It is suggested that the volcanism in Misiones and in the overall LIP could havebeen linked to an ascending limb of a large-scale convective roll induced by thesubduction in the western margin of Gondwana. This ascending limb might havemainly affected weak cortical areas (old sutures between cratons). On the otherhand, the volcanism of Sierra Chica might have been related to a small-scaleedge-driven convection triggered by the great contrast in thickness between the Ríode la Plata craton and the Pampia terrane.v