Provenance analysis and tectonic setting of Late Neoproterozoic metasedimentary successions in NW Argentina

MARGARITA DIANA DO CAMPO; RIBEIRO GUEVARA, SERGIO

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

Elsevier

Año: 2005 vol. 19 p. 143 - 153

0895-9811

Major, trace, and rare earth element data for Puncoviscana Formation metasediments were used to constrain their provenance and tectonic setting. This unit, which crops out in NW Argentina, mainly consists of pelite-greywacke turbidite sequences. An incipient regional metamorphism and a polyphase deformation, with a main deformation during the latest Proterozoic – earliest Cambrian Braziliano orogeny, affected the sedimentary sequences. The enrichment in LREE and other incompatible trace elements over compatible ones, as well as the high and uniform Th/Sc ratios, indicate a predominance of upper-crust acid rocks as parent material. Some chemical characteristics of these rocks, such as their high Th/U, Rb/Sr and Zr/Sc ratios, imply sedimentary recycling. Based on tectonic discriminant diagrams employing trace elements considered relatively immobile during low-grade metamorphism, a passive margin setting could be inferred. Moreover, comparison of the trace element contents of Puncoviscana metapelites with those of mudstones deposited in known tectonic settings shows the closest matching with passive margin shales.