Petrology and stratigraphy of pre-Cambrian Hormuz Series outcrops in Jabal Sanam structure - the oldest surface rocks in Iraq

Abstract

Detailed geological field investigations have been done at Jabal Sanam structure Southern Iraq. More than 150 rock and mineral represented samples were collected, and 130 thin sections of these samples were prepared and examined microscopically. An accurate mineralogical study of these rocks by the analysis of 15 samples with the X-ray diffraction technique. A large number of sedimentary rocks were distinguished through field observations and petrographic studies, such as gypsum, limestone, dolomite, red and green marl, sedimentary ironstones, chert, and salts. Various types of igneous and metamorphic rocks, such as dolerite, schist, slate, and metamorphic sediments, were found as beds or fragments intruded with the evaporite rocks of Jabal Sanam. Distinct mineralizations of hematite, pyrite, and dolomite minerals were observed in these successions. It was also noted that these rocks were subjected to varied geological processes of different degrees that affected their original rock characteristics such as diagenesis, metamorphism, deformation, and dissolution processes. A petrological, stratigraphic, and tectonic correlation has been made with similar structures spread through the region (Iran and Arabian Peninsula) in light of their composition, which, in general; consists of infra-Cambrian evaporates of Hormuz Series. This study supports the previous geological studies on this salt structure and shows a great similarity between the rocks of Hormuz Series Complex and those of Jabal Sanam, which may be considered in terms of stratigraphy and petrology as equivalent rock units. Thus, these rocks may be suggested as the oldest rocks exposed above the earth’s surface in Iraq.