Petrography, Major and Trace Elemental Geochemistry of the Ordovician-Silurian Siliciclastics in North of Tabas Block, Central Iran: Implications for Provenance and Paleogeography

The upper part of Shirgesht (UPS) and lower part of Niur (LPN) formations (Ordovician-Silurian) consist of sandstone, shale and limestone, respectively. The petrography and geochemical analysis conducted to evaluate provenance of siliciclastic deposits in order to understand the paleogeography of Central Iran during the Early Paleozoic time. This study shows that quartz and K-feldspar are the most abundant minerals in these siliciclastic rocks and the felsic igneous rock, probably granite, is the possible source rock. The average CIA (71) value and rare earth elements diagram, such as Th/U ratio versus Th, reveal a high degree of paleo-weathering in the source area. The craton interior and transitional continent were interpreted as a tectonic setting for UPS and LPN formations, respectively. Furthermore, the geochemical analysis revealed active continental margin and mostly passive margin during deposition of these two formations, respectively. Rifting in Central Iran during Ordovician-Silurian time generated normal faults at the edge of platform which had a major role in production of siliciclastic deposits.