The geochemistry and provenance of Ordovician turbidites in the Argentine Puna

Petrographical and major, trace and rare earth element data are combined in a provenance study of Early and Mid-Ordovician volcaniclastic turbidites in the Puna of NW Argentina. The tectonic setting of the depositional basin béhind a west-facing volcanic arc is well established from the literature, so that the new data may be used to test published geochemical discrimination schemes of tectonic setting of sedimentary rocks. However, there is a controversy whether volcanism took place in an island arc or a mature continentalmargin arc. The data show that the arc had a sediment source of average upper crustal composition dominated by silicic and intermediate magmatic rocks. Major elements document that subaerial weathering significantly influenced the detritus composition, whereas the HFS elements in particular retained the original source signal. The HFS and REE characteristics, as well as other parameters, compare favourably with those of Recent deep sea sands derived from continental arcs.