Provenance and tectonic setting of Upper Devonian sandstones from Ilanqareh Formation (NW Iran)

Abstract

Provenance and tectonic setting of the Upper Devonian sandstones in NW Iran have been interpreted on the basis of petrography and trace-element analysis of samples from two different stratigraphic sections. Modal analysis data of 27 samples with medium sand size and well-sorted properties from Ilanlu section and 23 samples from Ilanqareh section reveal that monocrystalline and polycrystalline (average 6% for Ilanlu section and 3% for Ilanqareh section) quartz grains with inclusions, such as rutile needle and apatite, can be derived from felsic igneous rocks of a craton interior setting. Geochemically, trace-element concentrations, such as La, Th, Sc and Zr, and ratios, such as La/Sc, Th/Sc, La/Co, and Th/Co, of sandstones from Ilanqareh Formation at both localities indicate felsic igneous source rocks and a passive continental margin setting for the source area. Furthermore, the evidence of recycling (for example, well rounded zircons) in the studied samples indicates that recycled sedimentary rocks should also be considered as one of the major source rocks. Enrichment in Zr, negative Sr anomalies and Th/U ratios higher than 3.8 for these sandstones are further evidence for recycled sources, which can be related to the effect of the Hercynian orogeny in NW Iran.