Abolfazl Jamshidipour, Dr. Mohammad Khanehbad,
Volume 31, Issue 4 (12-2023)
Abstract
The Sibzar Formation (Middle Devonian) is located about 30 Km east of Neyshabur city and is composed of lower dolostone with intercalations of sandstone, middle basaltic sill, and upper dolostone to limy dolostone, with a thickness of 334 m. The sandstone intercalations of this formation have fine to sometimes medium-grained quartz, with low values of feldspar, and rock fragment. According to petrography studies, sandstones of the Sibzar Formation were mostly quartzarenite and subarkose, however some samples plotted on litharenite. From the perspective of geochemical studies, the most abundant major oxides in these sandstones are SiO2 and Al2O3 with an average concentration of 77.8 and 8.3 (wt%), respectively. According to the ratios of SiO2/Al2O3 and Na2O/K2O and other amounts of major oxides and trace elements, such as CaO, Fe2O3, TiO2, Zr, and V, these sandstones have medium to high values of quartz; therefore have a quartzose sedimentary provenance, and are located in an intracratonic basin on the passive continental margin. Source rocks of these sandstones are intermediate to felsic igneous rock and have been affected by moderate to extreme degrees of chemical weathering. According to the evidence, the source of siliciclastic sediments for Sibzar Formation sandstones may have been Arabian and African plates.