Provenance and tectonic setting of Neoproterozoic to Early Cambrian metasedimentary rocks from the Cordillera Oriental and Eastern Sierras Pampeanas, NW Argentina

Resumen

Major, trace, and
rare-earth element data for the Neoproterozoic to early Cambrian
Puncoviscana Formation and related highergrade metasedimentary rocks
in Eastern Sierras Pampeanas, NW Argentina, were analyzed to
evaluate their provenance, weathering, and tectonic setting during
the upper Neoproterozoic-lower Paleozoic. The studied rocks are
metapelites and metapsammites that were mainly affected by the lower
Cambrian Pampean orogeny. Geochemical analyses indicate that the
Puncoviscana Fm. and related rocks are characterized by moderate
Chemical Index of Alteration (CIA) values. REE element
distributions, Eu/Eu* values, and high Zr/Sc and Th/Sc ratios
indicate that the samples were likely derived from predominantly
upper-crust felsic sources. Tectonic discrimination diagrams based
on immobile trace elements (e.g. Th-La-Sc, Sc-Th-Zr/10),
multi-element patterns, REE characteristics, and diagnostic trace
element ratios (i.e. Th/Sc, Zr/Hf, La/Th, La/Sc) imply that the
tectonic setting of the source area was a continental island arc
and/ or an active continental margin. Geochemical signatures of
low-grade metapsammitic samples (high Hf and Zr content, and high
Zr/ Sc ratios) indicate crustal recycling. The geometry and sequence
of structures and microstructures preserved in all samples are
pervasive and suggest a common and uniform deformational history
during the Pampean orogeny. Geochemical signatures and structures of
the studied samples are consistent with protolithic sediments of the
Puncoviscana Fm. and related rocks initially deposited in an
arc-related basin that was subsequently deformed during the Pampean
orogeny