Preprint
Petrological features of the first Cenozoic alkaline magmatic event recorded in northwestern Uruguay, southern extreme of the Paran ́a basin
Fecha
2022Registro en:
Muzio Sauer, R, Olivera Ichazo, L, Fort, S [y otro autor]. "Petrological features of the first Cenozoic alkaline magmatic event recorded in northwestern Uruguay, southern extreme of the Paran ́a basin" [Preprint]. Publicado en: Journal of South American Earth Sciences, 2022, 116: 103796. DOI: 10.1016/j.jsames.2022.103796
Autor
Muzio Sauer, Rossana
Olivera Ichazo, Lucía
Fort, Santiago
Peel Canabal, Elena
Institución
Resumen
The Cenozoic mafic alkaline rocks found in northwestern Uruguay, in the southernmost portion of the Paran ́a
Basin, comprise three subvolcanic plugs composed of Ne-tephrites. They cut through basalts that make up the
Paran ́a Magmatic Province as well as part of the sandstones of the Late Jurassic–Early Cretaceous age. These
mafic rocks are characterized by an aphanitic hypocrystalline texture that is occasionally porphyritic with py-
roxene and olivine macrocrysts/xenocrysts. We present the first lithogeochemical results that also include the
Sr–Nd–Pb isotopes to determine the petrogenetic processes. These mafic rocks are enriched in light rare earth
elements (La/LuN = 23.12–28.81) with respect to chondrite, in large-ion lithophile elements (Ba, U, and La), and
in high-field-strength elements, such as Ta, Nb, and Zr, with respect to primitive mantle, and have a Mg# of
0.53–0.56. The trace element geochemistry and isotopic data (low radiogenic 206Pb/204Pb and low 87Sr/86Sri
between 18.315 and 18.733, 0.70397 and 0.70443, respectively) indicate that the primary magma could be the
product of the melting of an enriched mantle source with the possible involvement of metasomatic processes,
lacking significant contamination by the continental crust. The K–Ar (whole rock) geochronology conducted on
two samples yielded ages of 63.7 ± 2.5 and 51.5 ± 1.7 Ma for this magmatic event