The 40th anniversary of the Chilenia terrane: Where is its Grenville-age basement?

Abstract

As is well known, the advent of plate tectonics in the early 1960s brought about a worldwide revolution in the Earth Sciences. In Argentina, a pioneer in applying plate tectonic thinking in the early 1980s was Dr. Víctor Ramos, who introduced provocative ideas about the presence of various terranes that formed Argentina and South America. Many of the proposed terranes were quickly adopted by the national and international geological community, although some crucial data were still lacking to be conclusive. One of these terranes, called Chilenia, corresponds to an alleged extensive continental block of near 1100 km long and 200 km wide, with a Grenville-age basement outcropping in the Cordón del Portillo, Frontal Cordillera of Mendoza province. This terrane is thought to have been accreted to the southwestern margin of Gondwana during the Late Devonian. Forty years after the birth of this idea, we revisit the existence (or not) of a Grenville-age basement within this terrane, integrating previous and new U-Pb zircon ages. New findings reveal no evidence of a Grenville-age basement, but instead indicate a Neoproterozoic or middle to upper Cambrian sedimentary succession overprinted by late Devonian metamorphism occur, i.e., the Guarguaráz Metamorphic Complex.