U-Pb detrital zircon ages and Sm-Nd isotopic features in low-grade metasedimentary rocks of the Famatina belt: implications for late Neoproterozoic-early Palaeozoic evolution of the proto-Andean margin of Gondwana

摘要

The Famatina belt, Central Andes, is part of an ancient accretionary margin built along, Western Gondwana in the early Palaeozoic. U Pb ion microprobe analysis of detrital zircons and Sm-Nd whole-rock analysis of two early Palaeozoic low-grade metasedimentary units record the early evolution of this region. Detrital zircons in the Negro Peinado and Achavil formations have ages ranging front Palacoproterozoic to Cambrian, consistent),with derivation front Gondwanan sources, T-DM ages suggest that the sedimentary rocks were derived From a composite solace area, which separated from the mantle during the Palaeoproterozoic (c. 1.8 1.6 Ga). Constraints from the youngest detrital grains indicate accumulation in a Mid- to Late Cambrian foreland basin adjacent to the inboard Pampean orogenic tract. The dominance of Cambrian ages ill the Negro Peinado Formation suggests derivation principally Front the eastern Pampean belt whereas the dominance of late Neoproterozoic ages in the Achavil formation suggests that input from the Pampean belt was overwhelmed by older Sources, The paucity of Palaeoproterozoic ages argues against direct input front older areas such as the Rio de la Plata craton. The predominance or Meso- and Neoproterozoic ages over older sources suggests that a Brasiliano-age magmatic are developed oil a Mesoproterozoic basement, probably a southern extension of the Arequipa Antofalla massif.