Geochemistry of Sandstones From Beduh Formation in Northern Thrust Zone, Kurdistan Region, Northern Iraq: Provenance and Tectonic Setting

Abstract

Petrographic, major, trace, and rare-earth element data for the sandstone of the Beduh Formation, Northern Thrust Zone, Kurdistan Region, were analyzed to constrain their provenance, weathering, and tectonic setting during the Early Triassic. The chemical index of alteration (CIA), chemical index of weathering (CIW), and plagioclase index of alteration (PIA) values and the A-CN-K diagram revealed moderate weathering in the source region. The index of chemical variability (ICV) suggests non-steady-state weathering conditions probably due to the intensity of tectonic activity in the source area. A statistically significant correlation observed between total rare earth elements (ΣREE) versus Al2O3 and Zr indicated that REE are mainly housed in detrital minerals. Petrographic study, microchemistry of heavy minerals, REE patterns, Eu/Eu* anomalies, chemical ratios {(La/Lu)n, Th/Co, Cr/Th, and La/Co} and the diagrams (TiO2 vs. Ni; La/Th vs. Hf) indicate the study sandstone was likely derived from felsic with some effect of intermediate source rocks (igneous and metamorphic). Tectonic discrimination diagrams (SiO2 vs. K2O/Na2O, TiO2 vs. Fe2O3 + MgO, and DF1 vs. DF2) based on major elements, multi-element patterns, REE characteristics, and diagnostic trace element ratios {Ti/Zr, (La/Sm)n} imply that the tectonic setting of the source area was a passive margin and active continental margin; the former confirm with the Arabian Shield and Rutba Uplift and the latter with the volcanic activity at Lower Triassic.