Ordovician igneous and metamorphic units in southeastern Puna: New U-Pb and Sm-Nd data and implications for the evolution of northwestern Argentina

New field, petrological, geochemical, and geochronological data (U-Pb and Sm-Nd) for Ordovician rock units in the southeastern Puna, NW Argentina, indicate two lithostratigraphic units at the eastern-northeastern border of salar Centenario: (1) a bimodal volcanosedimentary sequence affected by low- to medium-grade metamorphism, comprising metasediments associated with basic and felsic metavolcanic rocks, dated 485 +/- 5 Ma, and (2) a plutonic unit composed of syenogranites to quartz-rich leucogranites with U-Pb zircon ages between 462 +/- 7 and 475 +/- 5 Ma. Felsic metavolcanic and plutonic rocks are peraluminous and show similar geochemical differentiation trends. They also have similar Sm-Nd isotopic compositions (T-DM model ages of 1.54-1.78 Ga; epsilon(Nd)(T) values ranging from -3.2 to -7.5) that suggest a common origin and derivation of the original magmas from older (Meso-Paleoproterozoic?) continental crust. Mafic rocks show epsilon(Nd)(T) ranging from +2.3 to +2.5, indicating a depleted mantle source. The data presented here, combined with those in the literature, suggest Ordovician magmatism mainly recycles preexisting crust with minor additions of juvenile mantle-derived material. (c) 2007 Elsevier Ltd. All rights reserved.