Significance of the lithic volcanic detritus and crystalloclasts in development of paleogeography of the Zagros collisional belt: evidence from the Kurdistan Region, Northeastern Iraq

Previous studies modeled paleogeographic developments of the Zagros collisional belt from the Triassic to Eocene in which one or two well-developed island arcs surrounded the Sanandaj-Sirjan Zone (as part of the Neo-Tethys Basin). According to these studies, the survival of the arcs was more than 300 million years around and inside the basin, and had given the high contrast topography that was reflected by a deep seafloor and elevated lands. The present study assumes that this topography was favorable for the high rate of erosions and voluminous influx of the volcanic detritus and crystalloclasts (deposited as greywackes) to the aforementioned basin and they were significant in the development of the Zagros Collision Belt. Conversely, the previous studies ignored the role of volcanic detritus while devoting its development totally to the role of ophiolite obduction. We investigated the erosion products of the volcanic arcs (lands) for the first time and their roles in the paleogeographic development of the Zagros Belt. In the studied area, these volcanic clasts (detritus) now occur as metamorphosed rocks and are more than 350 m thick, while previous studies considered them ophiolites. The detritus includes lithic volcanic clasts and crystalloclasts of plagioclase, hornblende, pyroxene, and olivine, which are common in the Bulfat, Mawat, and Penjween Ophiolite Complexes. The present study concluded the filling of the Sanandaj-Sirjan basin with detritus that were derived from the Urumieh-Dokhtar Magmatic Arc during the Jurassic-Cretaceous. Later, part of the sediments had uplifted as an accretionary prism during Paleocene-Eocene and their erosion supplied detritus to the foreland basin which now consists of the claimed ophiolite complexes in northeastern Iraq.