© UB-ICTJA 319

New SHRIMP U-Pb zircon ages are reported for igneous and sedimentary rocks of the Famatina Complex, con-straining the age of the magmatism and the ensialic basins. Together with whole-rock and isotope geochemistry for the igneous rocks from the complex, these ages indicate that the voluminous parental magmas of metalumi-nous composition were derived by partial melting of an older lithosphere without significant asthenospheric contribution. This magmatism was initiated in the Early Ordovician (481 Ma). During the Mid-Late Ordovician, the magmatism ceased (463 Ma), resulting in a short-lived (no more than ~20 Ma) and relatively narrow (~100–150 km) magmatic belt, in contrast to the long-lived cordilleran magmatism of the Andes. The exhuma-tion rate of the Famatina Complex was considerably high and the erosional stripping and deposition of Ordovi-cian sediments occurred soon after of the emplacement of the igneous source rocks during the Early to mid-Ordovician. During the upper Mid Ordovician the clastic contribution was mainly derived from plutonic rocks. Magmatism was completely extinguished in the Mid Ordovician and the sedimentary basins closed in the early Late Ordovician