Detrital modes in Lower Mesozoic sandstone of the Wulgai Formation : implications for provenance

The detrital modes of twenty-five sandstone samples from Triassic Wulgai Formation have been studied in Zhob and Qila Saifullah districts of Balochistan province in order to determine their provenance and tectonic setting. The sandstone is mostly fine- to medium-grained. Quartz is the most abundant framework grain in sandstone, while heavy minerals include rutile, tourmaline, staurolite, zircon, and hornblende. Among the lithic fragments, metamorphic lithic fragments are the most abundant rock fragments. The sandstone of the Wulgai Formation is classified as quartz arenite (Q96F4L0.2). The Qt-F-L (Qt96F4L0.2) and Qm-F-Lt (Qm96F3Lt1) plots show the craton interior as the source terrain for the sandstone, in which metamorphic and plutonic terrains were the most dominant sources. The very-high content of monocrystalline quartz indicates high maturity of the sandstone, which may be attributed to quartz-rich, acidic igneous and high-grade metamorphic terrains. The most quartzose sands are usually derived from stable craton interiors having low relief.