Geochemical and Sr-Nd-Pb isotopic insight into the low-Ti basalts from southern Parana Igneous Province, Brazil: the role of crustal contamination

摘要

The south hinge of the Torres Syncline in southernmost Brazil hosts a volcanic succession of pahoehoe and rubbly Gramado-type lavas belonging to the similar to 132Ma Parana-Etendeka Igneous Province. We evaluate the geochemical and Sr-Nd-Pb isotopic variations using local-scale stratigraphy in order to discuss the petrogenesis of lava flows in a single magma type and to estimate the role of crustal contamination and the potential contaminants involved. The geochemical and isotopic variations along the lava pile are not systematic, implying that the magma chamber could have undergone successive replenishments of basaltic magma. The process of crustal assimilation explains the high and widespread initial Sr isotopic ratios at 0.707798-0.715751 and the very low epsilon(Nd) at -8.36 to -5.41, with associated Pb isotopic variations (18.42