Sr-Nd isotope data of basement rocks from the northernmost Argentine Precordillera and its implications for the early Paleozoic evolution of western Gondwana margin.

MARTINA, F.; ASTINI, R.A.; PIMENTEL, M.M.

Antofagasta

Congreso; XIII Congreso Geologico Chileno; 2012

Universidad Catolica del Norte

The r¨ªo Bonete region in NW Argentina is suggested as the northern extent of the Precordillera terrane. We present new Sr-Nd data of otho-derived greenschist, garnet amphibolites and quartz-phyllites belonging to the basement of the r¨ªo Bonete in order to constraint the affinity of this region with Precordillera. The Nd systematic of the greenschists/metabasites (¦ÅNd(470) = +2.14 - -0.19; TDM = 0.99 - 1.2 Ga) suggest a Mesoproterozoic poorly depleted mantle source. Similar Nd values have been recognized in Sierra de Umango, Pie de Palo, the anorthosites of Sierra de Maz and the southernmost Arequipa-Antofalla Massif. Nd model ages between 1 and 1.4 Ga are also present in the Mesoproterozoic Grenvillian basement of SE Laurentia. In contrast, the garnet-amphibolite and the the quartz-phyllite have ¦ÅNd(470) (-0.53 - -3.83) and TDM ages (1.32 - 1.55 Ga) more compatible with typical basement rocks of SW Gondwana. According to our interpretation, some lithotypes included within the basement of the r¨ªo Bonete area could have been part of the basement of the Precordillera terrane.