Geochemical and Characteristics of Mafic and Ultramafic Rocks of the Suprasubduction Zone Mawat Ophiolite, NE Iraq

Abstract


Introduction
Ophiolites are remnants of ancient oceanic crust and upper mantle.They are located along the destructive continental margins emplaced there by obduction because of accretional and collisional tectonics after the formation of oceanic crust.They have formed in various tectonic settings, such as mid-ocean ridges (MOR), suprasubduction zones (SSZ), intra-oceanic arcs, volcanic arc, forearcs, backarcs and rifting of continental margins (Saccani et al., 2015).
Ophiolites are reported from various parts of the world with ages ranging from Archean to Cenozoic (Furnes et al., 2014).For example, Archean suprasubduction zone ophiolites occur along the margin of microcontinent in the North China Craton (Santosh et al., 2016) and a Proterozoic 870-627 Ma old ophiolite suite in the Arabian Shield (Dilek and Ahmed, 2003).
In the Alpine-Himalayan Orogenic Belt, the ophiolites are classified in two age groups: the Jurassic group (170 to 140 Ma old) and the Cretaceous group (125 Ma to 90 Ma old), but minor Triassic/Permian group is also reported (Furnes et al., 2020).The Cenozoic ophiolites also occur within the Alpine-Himalayan Orogenic Belt.The Eocene ophiolites, that occur along the Iran-Iraq border from Kermanshah in Iran (Moghadam and Stern, 2015) to Hasanbag in Iraq (Ali et al., 2013), are related to intra-oceanic subduction in the Neotethyan ocean, similar to volcanic-arc type ophiolites (e.g.Furnes et al., 2020).Eocene and younger ophiolites occur in southeastern Asia in Indonesia (Ishikawa et al., 2007), Philippines (Yumul, 2007), Taiwan (Jahn, 1986) and Japan (Hirano et al., 2003) as well as in western South America, e.g. in Chile (Veloso et al., 2005).Ophiolite studies have shown a wide variety in their lithology and geochemical characteristics (Saccani, 2015).Therefore, not all ophiolites are products of the conventional mid-ocean ridge processes as identified by the Penrose definition (Anonymous, 1972).
The ophiolites in the vast Alpine-Himalayan Orogenic Belt are subdivided into subductionunrelated and subduction-related type ophiolites in terms of their tectonic setting before becoming incorporated into continental margins (Dilek and Furnes, 2014).The subduction-unrelated ophiolites are subdivided into rift and continental margin types, which show the embryonic stage of ocean crust formation.Continental rifting leads to the onset of seafloor spreading.The subduction-related ophiolites include forearc, backarc to forearc, backarc and volcanic arc ophiolites which all show different geochemical signatures.The backarc and forearc types represent end-members and show low to high and high subduction influence, respectively.The third type of ophiolites are related to plumes which might be part of oceanic plateaus (Dilek and Furnes, 2014).
Within the Alpine-Himalayan Orogenic Belt, the subduction-related ophiolites constitute 76% of the ophiolites and the majority of these are of backarc type (Furnes et al., 2020).Within the Bitlis-Zagros suture zone, the majority of the Neotethyan ophiolites are proposed to have formed in a suprasubduction zone environment, backarc, backarc to forearc and forearc settings (Stern et al., 2012).Mafic and ultramafic rocks are the most abundant components in ophiolites.These are widely used to infer the magmatic events and tectonic histories that occurred in ancient oceanic basins.Different petrological and geochemical characteristics can constrain the nature of the mantle source and provide new insights into the processes that control formation and evolution of mantle-derived melts.These in turn can be used to identify the tectonic environment where they were formed (Piccardo and Guarneri, 2011).
Previous studies on the gabbroic rocks from the Mawat ophiolite (MO) conclude that the gabbros have MORB affinity (Mirza and Ismail, 2007).The metagabbros in the southern part of MO are tholeiitic MORBs formed by partial melting of peridotite (Koyi et al., 2010).Azizi et al. (2013) proposed that the magmatic activity in the MO has some affinity to OIB type and high Mg basalts and conclude that their findings are not consistent with the MORB, island arc or suprasubduction zone as a magma source, but related to plume setting.In this study we describe petrological and geochemical characteristics of the mafic and the ultramafic rocks from the MO.Our findings will be discussed in comparison with previously published data from the MO (Mirza and Ismail, 2007;Koyi et al., 2010;Azizi et al., 2013) and we show that the MO is one of the suprasubduction zone ophiolites within the Alpine-Himalayan Orogenic Belt.

Regional Geology
The Zagros Orogenic Belt (ZOB) between the Arabian shield and the Sanandaj-Sirjan Zone (SSZ; Fig. 1) contains ophiolitic remnants including Mawat, Penjwen, Bulfat, Pushtashan and Hasanbag in Iraq (Ali et al., 2019;Al Humadi et al., 2019;Ismail et al., 2020) and Piranshah, Sardasht, Marivan and Kermanshah in Iran (Allahyari et al., 2014;Ao et al., 2021;Saccani et al., 2014).They occur discontinuously along the southern boundary of the SSZ.The ophiolites were emplaced within the forearc accretionary complex of the Eurasia active margin (Zhang et al., 2017).The ZOB formed by long-lasting convergence between the Eurasian and Arabian shields with three major tectonic events: 1) early to late Cretaceous subduction of the Neotethyan oceanic plate beneath the Eurasian continental plate, 2) emplacement of the late Cretaceous Neotethyan ophiolites onto the Arabian continental passive margin, and 3) the Cenozoic collision of the Arabian and Eurasian continental plates (Moghadam et al., 2019).
The ZOB is composed of three tectonic subdivisions: (a) the Zagros Fold-Thrust Belt is ~ 2000 km long and is folded and shortened after the Miocene.The belt consists of 12-13 km thick Cambrian to Quaternary sediment cover on the Arabian plate passive margin (Agard et al., 2011), (b) the Sanandaj-Sirjan Zone represents a micro-continent rifted from the Arabian plate in the late Permian and accreted to the southern margin of Eurasia in the late Triassic (Agard et al., 2011), and (c) the Urumieh-Dokhtar Magmatic assemblage is 150 km wide and a distinctively linear and voluminous magmatic arc of the Tertiary age (Omrani, 2008) (Fig. 1).Dilek et al., 2007).The tectonic units and boundaries of the Zagros Orogenic Belt are modified from Alavi (2007).

Geology of the Mawat Ophiolite
The MO crops out over ~ 250 km 2 in an elevated and rough topographic area northeast of the city of Sulaimani in northeastern Iraq and lies between two thrust sheets (Figs. 2 and 3).The eastern sheet is the Walash group, which comprises metamorphosed red shales, limestones and mafic volcanic rocks (Ali et al., 2013).The western sheet is the Naopurdan group of volcano-sedimentary successions (Ali et al., 2013).The MO comprises mantle and crustal sections: the mantle peridotites include serpentinized harzburgitess, dunite, chromitites and minor lherzolites.Numerous pyroxenite dykes intruded the mantle peridotite and dunites (Fig. 4c, d and g).The crustal section makes two-thirds of the exposed ophiolite consisting of layered and amphibole-rich gabbros intruded by minor diorite and diabase dykes (Jassim and Goff, 2006).The crustal section is lacking the sheeted dykes.The gabbro is the main component and form most of the central part of the MO (Jassim, 1973) and covers an area about 170 km 2 (Fig. 3).The layered gabbro, which consists of alternating plagioclase-rich and pyroxenerich bands, is the main type surrounded by the sheared gabbro and ultramafic rocks in the east and by metabasalts and amphibolites in the west, southwest and south (Buda and Al-Hashimi, 1977).
The pegmatitic gabbro occurs as lenses within the layered gabbro in the western, northern, and southern parts (Jassim, 1973).In the east, the pegmatitic gabbro occurs within the ultramafic rocks (Jassim and Goff, 2006;Al Humadi et al., 2019).The plagiogranite/tonalite dykes intruded the gabbros in the west (Mirza and Ismail, 2007) and leucogranites/granites intruded the mantle peridotite in the central MO (Mohammad et al., 2014).These two types of felsic dykes intruded the mantle section in the eastern part (Al Humadi et al., 2021).The volcanic rocks occur in two groups: the lower one is the metavolcanic Mawat group and the upper one is the volcano-sedimentary Gimo group.The volcanic rocks are exposed in the northern and southern parts and are composed of alternating white siliceous carbonate and dark calcschist with thin metavolcanic interlayers (Fig. 3).The contacts between the layered gabbro, peridotite and volcanic rocks are thrust faults (Mirza and Ismail, 2007).The Mawat group is overlain by the Gimo group and both groups underwent low-grade metamorphism (Jassim and Goff, 2006).
The radiometric dating of the felsic rocks from the MO yielded the crystallization ages of 94.6 ± 1.2 Ma (U-Pb monazite in a felsic dyke; Al Humadi et al., 2019), 96.8 ± 6.0 Ma (U-Pb zircon in a granite; Mohammad and Cornell, 2017) and 93.4 ± 1.8 Ma (Rb/Sr mineral isochron of a granitic dyke; Azizi et al., 2013).The pegmatitic gabbro in the eastern part of the MO yielded an age of 81 ± 3 Ma (zircon: Al Humadi et al., 2019).

Materials and Methods
Sixteen mafic and sixteen ultramafic whole-rock analyses for major and trace elements were carried out at Acme Analytical Laboratories Ltd. (Acme) in Vancouver, Canada.The samples were pulverised in a mild steel swing mill and after the LiBO2 fusion and HNO3 dilution, the major elements were analysed by inductively coupled plasma-emission spectrometry (ICP-OES).The trace elements were analysed by inductively coupled plasma-mass spectrometry (ICP-MS).The analytical precision is 1-5% for the major oxides and ±10% for the other elements.Due to the extremely low concentrations of many elements (below detection limits), the second batch of six mafic and seven ultramafic samples were reanalysed with a method of lower detection limits.These samples were analysed in Acme Analytical Laboratories Ltd. (Acme) in Perth, Australia.The samples were crushed and then pulverised in a mild steel swing mill and cast using a 66:34 flux with 4% LiNO3 added to form glass bead.The major elements were analysed by X-Ray Fluorescence Spectrometry (XRF) on oven dry (105°C) sample.The trace elements were analysed by Fused Bead for Laser Ablation inductively coupled plasma-mass spectrometry (ICP-MS).In this study, the analysed data from the first batch were used.In cases where these analyses were below detection limit, the analyses from the second batch were used which are above detection limit.The analysed data are presented in the Appendix.The geochemical data were plotted with the GCDKit software (Janoušek et al., 2006).Thirty-one mafic and ultramafic samples from published sources were used for the comparison and discussion.They include four gabbro samples from the western part of the MO (Mirza and Ismail, 2007), fourteen mafic and ultramafic samples from the central part of the MO (Azizi et al., 2013) and eleven mafic samples from the southern part of the MO (Koyi et al., 2010).

Mafic rocks (basalts and gabbros)
The petrographic study for the mafic rocks is carried out on sixteen samples.The basalts are predominantly aphyric or micro porphyric with equigranular to intergranular groundmass.They are composed of subhedral plagioclase and clinopyroxene ± orthopyroxene in a groundmass of chlorite, epidote, and opaque minerals.The plagioclase is partially altered to sericite, calcite and epidote minerals.The pyroxene is altered to secondary amphibole and chlorite.Small amygdules are filled with quartz or calcite and chlorite (Fig 5a).The layered gabbro is medium to coarse-grained with hypidiomorphic granular texture and composed of plagioclase, pyroxene, chlorite and opaque minerals.Accessory minerals are quartz, chlorite, magnetite and ilmenite.The plagioclase is partly altered to sericite.The pyroxene is partially or completely altered to secondary amphibole (Fig 5c) and chlorite.The pegmatitic gabbro is medium to coarse-grained and some crystals are up to 1.5 cm (Fig. 4b).The samples display porphyric, poikilitic and sub-ophitic textures.The plagioclase is partly to completely altered to sericite.The pyroxene is partially or completely altered to amphibole.The epidote, chlorite, opaque minerals and undefined minerals are the accessories (Fig. 5d).

Ultramafic rocks
The petrographic study for the ultramafic samples is carried out on 16 samples.The rocks are most common in the eastern and less abundant in the southern and northern parts of the MO (Jassim 1972).The studied ultramafic rocks fall into two group: the first group comprises dunites and serpentinites and the second group pyroxenite dykes.The dunites occur in two types: the first is irregular, ellipsoidal type and the second is massive block type.The first irregular type is of various sizes and occur within the peridotite host rocks (Fig. 4c).Olivine is dark green to black in colour in the hand samples, meanwhile it is microscopically partly to completely altered to serpentine and magnetite along the fractures and grains rims to produce a mesh texture (Fig. 5g).Irregularly shaped fine-grained spinel occurs disseminated in the dunite.Commonly, the dunite and peridotite host chromitite pods in the Ser Shiw valley (Fig. 4h).The dunite has a graded contact relation with the chromitite pods.The spheroidal dunite bodies and the peridotite were intruded by pyroxenite dykes and their contact relations with the dykes are sharp (Fig. 4c and g).Mohammad (2020) classifies the dunite as a tectonite dunite.
The second type of dunite is massive blocks (Fig. 4d and f).In the thin section, the samples show xenomorphic granular textures and are composed of fresh olivine with accessory chromian spinel and pyroxene relics (Fig. 5e).The olivine is anhedral and > 0.3 mm in size.Small amount of serpentine occurs in the olivine fractures.The euhedral to subhedral black chromian spinel crystals are up to 1.5 cm in diametre in the lower part of the dunite massive block (Fig. 4f).This type of dunite is a cumulate (Mohammad, 2020).In some samples, the olivine has survived in the core of the mesh (Fig. 5f).Some serpentinite samples are composed of primary olivine, pyroxene, serpentine and chromian spinel and talc as well as opaque minerals observed within the mesh texture of olivine pseudomorphs.The finegrained grey pyroxenites occur as 5 to 15 cm thick dykes and sills intruding the ultramafic rocks (Fig. 5c).The 2-5 cm light grey margin in some pyroxenites gradually become dark toward the central part (Fig. 4d and g).The margins have sharp contacts with dunite and peridotite host rocks.The dykes are composed of pyroxenes partially altered to secondary amphibole and minor olivine, plagioclase and Crspinel along the cleavage (Fig. 5h).
The N-MORB-normalized immobile multi-element diagram shows that the gabbroic samples fall parallel and partly above the N-MORB reference line (Fig. 9b).In the N-MORB-normalized diagram, the gabbros show LILE enrichment except for some samples which show depletion in Rb and K.The HFSEs show a depletion in Nb, Zr and Ti (Fig. 9c).

Petrogenesis
The mafic and ultramafic rocks are affected by various degrees of alteration, which resulted in partial to complete replacement of many of the essential rock-forming minerals and increased the loss on ignition (LOI).Three serpentinites have the highest LOI ranging between 13 and 14 wt.%, whereas, the highest LOI in the mafic rocks is < 5.9 wt.%.During such alterations, many of the major elements such as SiO2, K2O, Na2O and MgO, as well as LILEs and LREEs, generally show variable degree of mobilization.In contrast, the HFSEs (e. g., Ti, Zr, Y, Nb, Ta, Hf and Th), MREEs and HREEs as immobile elements, are useful for petrogenetic and tectonic studies (Karakaya, 2009).

Basalts and gabbros
The mafic samples show compositional variations, which could be related to mantle heterogeneity.(Pearce and Norry, 1979;Pearce, 1983).The differences in the REE-patterns and the key element ratios (e.g.La/YbN, Zr/Y, Nb/Y) between the basalts and gabbros cannot be explained by various degree of partial melting alone.Instead, differences in the magma sources are more likely.The basaltic rocks are slightly enriched in the HREEs relative to LREEs [(La/Yb)N =0.22-0.49]with positive Ba, U, K, Pb and Sr anomalies and negative Nb, Zr, and Ti in the N-MORB normalized diagram (Fig. 9d) suggesting that the basalts formed by partial melting of a depleted mantle.These features resemble those of the boninites formed in a forearc setting related to initial intra-oceanic subduction settings (Shervais et al., 2019).The subduction additions and degree of fluid flux from the subducting slab to the mantle wedge can be deduced from the ratios of highly fluid-mobile to less fluid-mobile or fluid-immobile elements (e.g.Sr/Ce) (Wehrmann et al., 2014).Based on the Sm/Lu vs. Sr/Ce diagram, the basaltic rocks show higher degree of partial melting relative to the gabbros (Fig. 10a) and the La/Yb vs. La diagram (Pinto-Linares et al., 2008) confirms the results of Fig. 10a, showing that both the gabbros and basalts follow the partial melting trend and the basalts have higher degree of partial melting (Fig. 10b).High Ce/Y and LaN/YbN ratios in mafic rocks are an indication for low degree of partial melting process or that the mafic rocks were derived from enriched sources (Saccani et al., 2003;Fig. 10c).Therefore, the values of Ce/Yb (0.08-0.2) and LaN/YbN (0.22-0.49) in the basaltic samples are lower than those in the gabbroic samples (1.18-2.7 and, 3.9-10.3 respectively).This suggests that the basalts formed by higher degree of partial melting of a depleted-mantle source compared to the gabbros.The basaltic samples show low Nb (0.1-0.79 ppm) and Zr (5.7-11.5 ppm) contents relative to N-MORB (Nb = 2.33 ppm and Zr =74 ppm, respectively) indicating that the basaltic rocks were formed from a depleted mantle source.In contrast, the gabbroic samples show high Nb 5.4-26.7 ppm, and Zr 63.6-158.2ppm implying that these rocks were derived from an enriched mantle source (Sun and McDonough, 1989).The mafic rocks from the central MO show variable low consentrations of Nb (0.9 -6.0 ppm) and low Zr (1.3 -6.7 ppm) except for one sample which has Zr content of 66.0 ppm.The gabbros from the western MO are low in Nb (0.24-0.71 ppm) and Zr (7-28 ppm).(Serri, 1981), (b) Ce vs Yb diagram (Hawkesworth et al., 1993), (c) Ni vs Ti/Cr diagram shows indication of island arc region for the mafic and ultramafic rocks (Beccaluva et al., 1983).Symbols and colours as in Fig. 6.
Ophiolites have been grouped into high-Ti, low-Ti and very low-Ti types.The high-Ti ophiolites display characteristics of the MORB-like magmas, occurring at mid-ocean ridges and well developed marginal basins.The low-Ti, and very low-Ti ophiolites are comparable to IAT and boninitelike magmas, respectively, formed in an intra-oceanic island arc setting (Beccaluva et al., 1989;Fig. 11a).Partial melting and re-melting of the mantle peridotite can lead to Ti-poor magmas (Hébert and Laurent, 1990).Low-Ti magma is a source for the basaltic and plutonic rocks formed in a suprasubduction zone setting (Camuzcuoğlu et al., 2017).The compositions in the Mawat data show that the basaltic rocks are low in Ti and classifies to the low-Ti ophiolites.Accordingly, the basaltic rocks derived from a low-Ti magma.The gabbroic rocks show high-Ti contents characteristic for MORB-like magmas (Fig. 11a).

Ultramafic rocks
The REE patterns of the ultramafic samples are slightly enriched in LREEs compared to MREEs and HREEs, showing a spoon-shaped pattern with extremely low ΣREEs.Both the dunite/serpentinite and the pyroxenite groups plot below the N-MORB reference line (Fig. 9h).The N-MORB and primitive mantle-normalized multi-element diagrams show two pattern types.The first type is the dunites and serpentinites which are extremely depleted in LIL and some HFS elements.The second type is the pyroxenite group which is less depleted in LIL and some HFS elements compared to the dunite/serpentinite group.The ultramafic samples show positive U, Pb and La anomalies and negative Nb, Ta and Zr anomalies.These features suggest that their parental magmas are derived from highly depleted mantle (Fig. 9g).
The low Ce/Yb ratios in the ultramafic samples show an island arc-related trend (Fig. 11b).The Ni vs. Ti/Cr diagram also indicates an island arc setting.(Fig. 11c).The Ti/V diagram suggests a boninitelike magma (Fig. 12b).The pyroxenite dykes are characterized by high MgO and SiO2 (Table 3) and the low Nb/Yb ratios are consistent with their derivation from a highly depleted mantle source.

• Tectonic Setting
Ophiolites can form in various subduction-unrelated and subduction-related tectonic settings (e.g., Furnes et al., 2020).The tectonic setting of the MO has been controversial.An earlier work on the mafic rocks from the western MO indicated a MORB and volcanic arc basaltic affinities and tectonic settings (Mirza and Ismail, 2007).Ismail et al. (2010) suggested the suprasubduction zone affinity which is supported by the chemical composition of the chromitites and presence of associated boninites in the MO.A more recent work on the mafic and ultramafic rocks by Azizi et al. (2013) concluded that the isotope ratios, REE patterns and major and trace element contents are not consistent with the MORB, island arc or suprasubduction zone settings.Instead, the geochemical data suggest a mantle plume setting.Geochemical compositions, especially trace elements, are effective tools to infer the tectonic settings of ophiolites.Several proxies have been developed to geochemically separate different ophiolite types and their tectonic settings (e.g., Pearce, 2014, Furnes et al., 2020).In this study, we use the Nb/Y vs Zr/Ti diagram (Pearce, 1996) for classification purposes, Zr/Y vs Th/Yb diagram to distinguish tholeitic from calc-alkaline basalts (Furnes et al., 2020), Nb/Yb vs Th/Yb diagram (Pearce, 2008) to separate the subduction-unrelated ophiolites from the subduction-related ophiolites, as well as the Ti/V diagram (Shervais, 1982) to identify the forearc basalts.These are based on immobile elements to minimise the effect of alteration.
Tectonic setting can be determined by using discrimination diagram of Th/Yb vs. Nb/Yb (Pearce, 2008).It shows that the mafic rocks fall above the MORB-OIB array.The basaltic rocks fall in the oceanic arc field and the gabbros in the continental arc field.The data above the MORB-OIB array is explained by variable enrichment of elements transported by hydrous fluids with or without melts released from subducted oceanic slab.This suggests a subduction-related type setting (Furnes et al., 2020;Fig. 12a).The subduction-related type includes backarc, backarc to forearc, forearc, and volcanic arc settings.Their compositions plot in the oceanic arc and overlap the oceanic arc/continental arc fields in the Th/Yb vs Nb/Yb diagram (Pearce, 2008).Moreover, the backarc type is characterized by the MORB basalts and the backarc to forearc and forearc types are characterized by IAT and boninite type magmas.
The Ti/1000 vs. V diagram discriminates the magmas of boninite, island-arc (IAT), MORB and alkali basalts.The ultramafic and basaltic samples plot in the boninite field, where the Ti/V ratio is <10.The gabbroic samples plot in the MORB field.The mafic rocks from the western and central parts from the MO (Mirza and Ismail, 2007;Azizi et al., 2013) (Shervais, 1982).Symbols and colours as in Fig. 6.
The suprasubduction zone ophiolites often contain geochemical stratigraphy of island arc tholeiites IAT, boninite affinity and lavas of MORB compositions (Pearce, 2003).The mafic rocks of MO have boninite, IAT and MORB-like compositions.Therefore, these rocks (MORB, IAT and boninites) were formed within the same forearc region, probably with early MORB-like (Reagan et al., 2010) and younger boninitic lavas, as is common in forearc settings (Ishizuka et al., 2014).In Mawat the stratigraphic order is disrupted by thrusting (Fig. 13) and now the ultramafic (harzburgite and dunite) rocks are on the top, the amphibole gabbros are in the middle and the basalts are at the bottom.The MORB-like rocks (Koyi et al., 2010;Azizi et al., 2013) are located in the southern and central part of the MO on top of the younger sedimentary rocks (Red Beds).The boninitic rock are located in the northern MO.This indicate that, in spite of thrusting, the MO has at large preserved some of its internal stratigraphy with MORB-like rocks at botttom and boninites on top (cf.Furnes et al., 2020).
The basaltic and gabbroic rocks were derived from different sources.The gabbros were dated at ~ 80 Ma, while the felsic dykes crosscutting the mafic rocks are ~ 95 Ma (Al Humadi et al., 2019).The gabbros are interpreted as rift-related in an extensional setting above the subduction zone setting after the ophiolite formation (Al Humadi et al., 2018).The gabbros of the similar age are found in the Kermanshah ophiolite (Ao et al., 2016).Recent studies on the Tethyan ophiolites show that most ophiolites have subduction zone chemical characteristics of the suprasubduction zone ophiolite type.(Dilek, et al., 2007).The ultramafic and mafic rocks of the MO show subduction influence in terms of the trace-element contents and is very similar to other ophiolites formed by initial subduction in a forearc of suprasubduction zone environment.That is similar to the late Jurassic-Cretaceous ophiolites in the Tauride-Pontide (Turkey), Zagros (Iran) and Himalayan ophiolites to the east showing geochemical characteristics of suprasubduction zone environment (Malpas et al., 2003).

Conclusions
The major and trace element analyses of the mafic and ultramafic rocks from the Mawat ophiolite lead to the following conclusions: • Three rock types occur in the mantle section: the dunites, serpentinites and later pyroxenites dykes.
They were derived from an extremely depleted mantle.• Three geochemical types of mafic rocks occur in the crustal section: boninites, IAT and MORB.
The ≥ 15 Ma younger gabbros are enriched compared to the other mafic rocks.• The geochemical data indicate that MORB-like rocks occur at the bottom and the boninites on the top of the ophiolite.This stratigraphy is typical for suprasubduction zone ophiolites.• The mafic rocks were formed in a forearc region and the geochemical data are consistent with the suprasubduction zone tectonic setting.The geochemical characteristics show that Mawat is one of the suprasubduction zone ophiolites in the eastern Mediterranean region.

Fig. 3 .
Fig. 3. Simplified geological map of the Mawat ophiolite, modified from Aziz (2008).The samples of this study and the comparison samples are indicated.

Fig. 5 .
Fig. 5. Photomicrographs (cross-polarized light) of mafic and ultramafic thin sections, (a) basalt sample showing aphyric and micro-porphyric and equigranular textures, composed of fine-grained plagioclase and pyroxene with amygdule structure, (b) basaltic sample is porphyric with equigranular to intergranular groundmass texture composed of subhedral plagioclase and clinopyroxene ± orthopyroxene, (c) and (d) gabbroic samples are medium to coarse-grained of porphyric, poikilitic, and subophitic textures, plagioclase and pyroxene are the main components, (e) massive dunite sample showing the xenomorphic granular texture of fresh olivine grains, (f) serpentinized peridotite sample showing serpentines replacing olivine and display mesh texture, (g) serpentinite sample shows pseudomorphic texture, the olivine completely replaced by serpentines and exemplified by mesh texture, (h) pyroxenite dyke composed of fine to coarse-grained of pyroxene and olivine.Plg = Plagioclase; Epi = Epidote; Ser = Sericite; Cpx = Clinopyroxene.

Fig. 9 .
Fig. 9. Chondrite-normalized REE patterns(Boynton, 1984) for (a) gabbros and basalts, (h) pyroxenite group and dunite and serpentinite group.Multi-elements diagrams of immobile elements of(Sun and  McDonough, 1989 in Pearce, 2014)  for (b) gabbros and basalts, (f) pyroxenite, dunite and serpentinite samples.N-MORB-normalized diagrams for (c) gabbros, the green colour line for basaltic sample(Azizi et al., 2013) and (d) basalts.Multi-elements diagrams of Primitive Mantle for (e) gabbros and basalts and (g) pyroxenite, dunite and serpentinite samples.The light brown shaded field for the mafic rocks from the central Mawat ophiolite(Azizi et al., 2013).The grey shaded field for the mafic rocks from the southern Mawat ophiolite(Koyi et al., 2010)  and the light blue shaded field for the gabbros from the western Mawat ophiolite(Mirza and Ismail, 2007).Symbols and colours as in Fig.6.
The chondrite-normalized ultramafic samples show spoon-shaped REE patterns (Fig 9h).The ΣREE values are extremely low (0.1-2.47 ppm).The LREEs of the pyroxenites are slightly enriched relative to HREEs (LaN/YbN = 0.68-3.58).The dunites and serpentinites are LREE-enriched compared to HREEs (LaN/YbN = 1.2-16.33).The MORB-normalized immobile multi-element diagram shows humps in La and Hf and troughs in Nb, Ce and Zr and are poorer in all elements relative to N-MORB (Fig. 9f).The primitive-mantle normalized trace element diagram shows a depletion in LILEs except Cs, Pb and HFSEs which display depletion in all elements except U (Fig. 9g).The pyroxenite dykes are depleted in the LILEs and the HFSEs Th, Nb, Zr and Ti.The dunites/serpentinites show extreme depletion in the LILEs and HFSEs compared to the pyroxenites.
plot in the boninite-IAT fields with Ti/V is <10-20, while the samples in Koyi et al. (2010) from the southern MO plot in the MORB field (Fig. 12 b).

Fig. 13 .
Fig. 13.Simplified section of the Mawat ophiolite showing the main rock types and the locations of the boninites and MORBs.

Table 2 .
The whole rock geochemistry for the gabbroic rocks from the Mawat ophiolite.

Table 3 .
The whole rock geochemistry for the ultramafic (dunite and serpentinite group and pyroxenite group) from the Mawat ophiolite