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

Abstract

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