Geochemistry of the sandstones of the Ojaggheshlagh Formation (Late Eocene-Early Oligocene), Eastern Moghan area, NW Iran: application for parent rock, climate and tectonic setting

Petrography and geochemistry analysis of the sandstones of the Ojaggheshlagh Formation (Late Eocene-Early Oligocene) of the Moghan Basin, was carried out to evaluate their tectonic setting, climate, weathering degree, and parent rock. Sandstones include litharenite and feldspathic litharenite and minor arkose and greywacke. In a general view, sandstones are immature, characterized by the poorly sorted and poorly rounded grains including volcanic fragments and feldspars and minor heavy minerals, mica, monocrystalline quartz and clay minerals. Geochemical diagrams including discriminate function, TiO2 vs. Al2O3, TiO2 vs. Zr, as well as trace elements diagrams/data as La/Th vs. Hf, Zr/Sc and Th/Sc indicate a predominantly basic to intermediate (and minor acidic) volcanic parent rocks for the Ojaggheshlagh sandstones. Low chemical index of alteration plus SiO2 vs. Al2O3+K2O+Na2O and Al2O3-CaO+Na2O-K2O diagrams emphasis sub-arid climate and short transportation distance of the Ojaggheshlagh sandstones from the source area, which led to the preservation of the unstable minerals and poor compositional and textural maturity of the Ojaggheshlagh sandstones of the Moghan Basin. Al2O3/SiO2 vs. Fe2O3+MgO, K2O/Na2O vs. SiO2 and La-Th-Sc diagrams and La/Th and Th/Sc content reveal an island arc tectonic setting The archived results of the paper are useful for the paleogeographical and tectono-sedimentary reconstruction of the Moghan Basin.