The Mesoproterozoic Maz terrane in the Western Sierras Pampeanas, Argentina, equivalent to the Arequipa-Antofalla block of southern Peru?: Implications for West Gondwana margin evolution

The rocks of Sierra de Maz and Sierra del Espinal (Western Sierras Pampeanas) represent pre-Famatinian (Ordovician) basement. Isotope compositions (Nd and Pb) of metasedimentary rocks and SHRIMP U-Pb dating of detrital zircons, combined with other geological evidence, show that three parallel N-S domains can be recognized. The central Maz Domain contains pre-Grenvillian metasedimentary rocks deposited between 1.2 and 1.6 Ga, that underwent Grenvillian granulite facies metamorphism and were intruded by mafic igneous rocks and massif-type anorthosites. Metasedimentary rocks have high Nd T-DM ages (1.7-2.7 Ga) and very radiogenic Pb (mu=9.8-10.2), suggesting provenance from reworked early Proterozoic or Archean continental crust. The domains to the east and west of the Maz Domain consist of three metasedimentary sequences with Nd T-DM ages between 1.2 and 1.6 Ga and variably radiogenic Pb (mu=9.6-10.0). U-Pb SHRIMP dating of detrital zircons, Nd T-DM model ages and comparison with other data suggest that these sequences are post-Grenvillian, i.e., Neoproterozoic and/or early Paleozoic. The Maz Domain is interpreted as a suspect terrane similar to the northern Arequipa-Antofalla craton that forms the basement of the Central Andes; both underwent Grenville-age orogeny and were probably once continuous along the western margin of Amazonia (West Gondwana). (C) 2007 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.