Geology of Zagros metamorphosed volcaniclastic sandstones: a key for changing the Mawat Ophiolite Complex to a metamorphic core complex, Kurdistan Region, NE-Iraq

Abstract

Mawat Ophiolite Complex is located about 36 km to the northeast of Sulaimani city and directly to the east-northeast of Mawat town near the border of Iran in the northeastern Iraq. The complex has about 600-km2 surface area and consists of high mountain terrains that subjected to intense geological investigations from the fiftieth of previous century till now. According to previous studies, the complex contains tens of igneous rocks such as basalt, metabasalt, tuff, diabase, metadiabase, diorite dykes, periodotite, serpentinite, serpentinite-matrix mélange, gabbro, metagabbro, harzbergite, pyroxenite, plagiogranite, pegmatite, granitiod rocks and dunite. They added occurrences of the volcanic and subvolcanic rocks in the form of dykes or basaltic flows. The present study tries to change the petrology and tectonics of whole complex from Ophiolite Complex to Metamorphic Core Complex. The revision includes refusal of all the above igneous rocks, instead they considered as medium grade regional metamorphism of different types of volcaniclastic sandstones (volcanic wackes), arenites and greywackes (impure sandstones) which sourced predominantly from remote volcanic source area inside Iran. The revision depended on several conjugate field and laboratory evidences inside the complex. These evidences such as absence of pillow basalt, volcanic flows, glass shards, volcanic cones, dykes, sills, contact metamorphism, dilatational structures and flow structures. Other evidences are presence of cross beddings, erosional surfaces, lensoidal channel fills, metamorphosed conglomerate, exposures of thousands of laminated planar beds and transition from fresh volcaniclastic sandstones to its medium grade metamorphosed counterparts, which previously considered as igneous rocks of ophiolite types. Another, evidence, in contrast to ophiolite section, the basalt location is at the base of the claimed ophiolite section while plutonic (dunite and peridotite) rocks located at its top. These locations of the two rocks contradict the definition of ophiolites. Accordingly, the present study changed the geological map of the whole Mawat area from igneous outcrops to metamorphosed volcaniclastic sandstones, arenites and greywackes that belong to Walash-Naoperdan Series. The parent rocks of the series transformed to different types of regionally metamorphosed rocks by deep burial during Eocene. During the burial, diageneses and metamorphisms enhanced by complex mixture of materials from different source areas and seawaters environments. Later, they uplifted, unroofed and exhumed during Pliocene as a core complex.

Geology of recently recognized lithologies inside the Red Bed Series in the Chwarta-Mawat area, Kurdistan Region, NE-Iraq

“…This tectonic feature is called Mawat Nappe by [5] who showed its thrusting over the Red Bed Series and Cretaceous rocks. In contrast to the Ophiolites Complex ideas of the previous authors such as [29,30] changed the area to the metamorphic core complex of a sedimentary origin.…”

Relation between Walash and Kolosh Formations and geology of their equivalent metamorphosed greywackes and arenites in Sulaimaniyah Governorate, Kurdistan Region, Northeast Iraq

“…Karim and Abioui (2021) [26] found a similar conglomerate in several places on Avroman Mountain between Qulqula and Avroman Formations and directly on the conglomerate of the Tanjero Formation. Karim and Ghafur (2021) [27] recorded the same type of conglomerate inside the Walash Formation (group) 100 m above the Shiranish Formation in the Mawat area (1 km south of the Gabra village). Many claimed felsic dykes (granitoid or dioritic dykes) are recorded by [28], Abdulzahra and Hadi (2017) [29], and Abdulzahra, et al ( 2019) [23] in and around the Kata Rash group (present conglomerate) but when inspected in the present study; their presence as a dyke is not proved since they cut nothing and not associated with mineralization, contact metamorphism, and digitation into country rocks.…”

“…In rare cases, the mafic volcanoclastic sandstones (greywackes) are so intensely pulverized and sheared that transformed into massive and amalgamated bodies which are previously called serpentinite in which serpentinization and shearing are observable even on a millimetric scale, especially on the southwestern boundary of the Penjween Ophiolite Complex (present metamorphosed greywackes) on the Milakawa Mountain at 1km north of Kani Manga village. As concerned to the other ophiolites and volcanic rocks outside the Penjween area in northern Iraq, Karim and Al-Bidry (2020) [34], Karim et al (2020) [35], Karim and Abioui (2021) [26], and Karim and Ghafur (2021) [27] studied many of them objectively and amended them to sedimentary successions. In these successions, the latter studies found ten of evidence confirming their new sedimentary origin.…”

Problemy ophiolitów Zagros i ciał bazaltowych, przykłady z Regionu Kurdystanu, północny Irak

“…As an example: a rock sample is very difficult to be proved as a meteorite by the geochemical analysis while boundary conditions and outline features can be more decisive. Therefore, if the sample was strange in its area of occurrence and has signs of burnt outlines, they reveal most possibly a meteorite Karim et al (2020) [29], Karim (2021) [45] and Karim and Abioui, (2021) [27] clarified the inability of textures and geochemistry to indicate the origin of rocks. These latter three articles presented more than ten pieces of evidence for refuting the magmatic origin of the Mawat Ophiolite, Avroman and Gercus basaltic bodies in northern Iraq.…”

“…We think that the regional metamorphism affected the rocks of the latter three complexes and changed the Penjween, Mawat and Bulfat to amphibolite and greenschist facies. Karim and Al-Bidry (2020) [23] and Karim and Abioui (2021) [27] and Karim (2021) [45] discussed tens of signals of sedimentary origins of these claimed ophiolite complexes. The rocks of these complexes consist of alternations of thousands of layers of different rocks such as pure limestone, clayey limestone, sandy limestone, marls, shales, calcareous shales, volcanic detritus, greywackes, arkose, arenites (plagioclase, olivine, amphibole or pyroxene arenites).…”