ORIGIN AND DISTRIBUTION OF CLAY MINERALS IN THE MUDSTONES OF THE KOLOSH FORMATION INRAWANDOZ AREA, NORTHEASTERN IRAQ

Abstract

The mudstone/ shale units constituted 60% of the Kolosh Formation of 170 m thickness, which were studied and the clay minerals were identified to conclude the origin and paleoclimate. The studied area is located near the suture of Zagros Thrust Ophiolite Zone in NE Iraq. Kolosh mudstones contain chlorite, vermiculite, illite, nontronite, serpentine with varieties of mixed-layer clays. These clay minerals are of detrital and diagenetic origin, which are controlled mainly by the source rocks, paleoclimatic conditions and the burial diagenesis. Some of chlorite, chlorite/ vermiculite mixed layer, nontronite and smectite refer to hydrothermal origin comes from submarine basaltic flows and the high-temperature pore waters.The distribution of the clay minerals in the stratigraphic section of the Kolosh Formation controlled by episodic thrusting, episodic volcanic eruptions and interbedded sedimentary rock units. These are controlled by the changes in the paleoclimatic conditions, chemical weathering and the diagenetic processes.The clay mineral assemblages refer to be derived mainly from Fe-Mg rich minerals with minor Si-Al rich silicate minerals, which are very common in the ophiolites and associated basic volcanic rocks. These rocks composed the major lithological units in the Zagros Thrust Belt of NE Iraq.