---

The Kermanshah Ophiolite Complex (KOC) lies in the structural – tectonic zone of western Iran in northern part of Zagros main thrust and is a part of highly dismembered Kermanshah – Panjvin Ophiolitic belt. The best outcrops of the sheeted and isolated dykes in this complex are present in south of Sahneh area. They are basic in composition. The geochemical studies show parent magma is in its initial melt stage with LIL elements enriched signature. Also, this magma belongs to high Mg and low K, tholeiitic subalkaline series. The patterns of incompatible trace elements demonstrate an island arc affinity for these dykes. The N-MORB- normalized multi-elements plots indicate nearly flat patterns for HFSE. Geotectonic diagrams reveal transitional characteristics between mid-oceanic ridge basalts and island-arc tholeiites. Therefore, the dykes of the KOC may be originated in a back-arc basin tectonic setting.

---

In this research, dolomites of Shahbazan Formation (Eocene) in southwest Kermanshah were studied. Two surface sections were measwred and 98 samples were collected.  Four types of dolomites were identified based on petrographic examinations. XRD results were used for determination of stoichiometry, degree of ordering and proportion of dolomite in samples. Results suggest that dolomicrites and dolomicrosparites formed during (early marine diagenesis) in tidal flat setting. The dolosparites formed during late stage dolomitization from recrystallization and evolution of dolomicrite and dolomicrosparite precursor. Dolosparites exhibit better stoichiometry (ave. 52.98 mole% CaCO₃) than their precursors (ave. 57.69 mole% CaCO₃). Degree of ordering in dolosparites is also higher than dolomicrites and dolomicrosparites (ave. 0.95 and o.68 respectively). Average Mg2+/Ca2+ ratio in studied samples is 0.73. Hence it was concluded that dolomicrites and dolomicrosparites evolved into dolosparites during recrystallization and diagenetic alteration. These evidences along with lack of any evaporates suggest these dolomites formed from dolomitizing fluids with relatively low Mg2+/Ca2+ ratio (probably less 1) in humid climate.

---

The Kermanshah ophiolite complex is located in outer Zagros ophiolitic belt and consists of both mantle and crustal suites as remnants of southern branch of the Neo-Tethys Ocean in Iran. Chemical composition determinative diagram of minerals indicates that olivine in dunite, harzburgite and lherzolites has forsteritic composition and in wherlitic rocks is chrysolite in composition likewise orthopyroxene and clinopyroxene in these rocks are enstatitic and diopside to augitic composition respectively. Textural evidence such as exsolution lamellae of clinopyroxene in orthopyroxene and  chain-like grains of spinel in minerals of ultramafic rocks of Sahneh, Harsin-Nourabad and Myanrahan region displaying clear evidence of cooling with decompression, partial melting and melt-rock reactions. Very low modal of clinopyroxene, Mg rich olivines and high Cr# content and Cr/Al ratio of chromian spinel from ultramafic cumulates indicate that dunites and harzburgitic rocks have formed by high degrees of partial melting. Calculated TiO₂, Al₂O₃ and FeO/MgO ratio in the parental melt that was in equilibrium with chromian spinels and also all of used discrimination diagrams are compatible with a forearc boninitic magma (such as  picrites or island arc tholeiites) in supra-subduction zone setting.

---

The Kermanshah ophiolite Complex is located in the structural – tectonic zone of the western Iran in northern part of Zagros main thrust and is a part of highly dismembered Kermanshah – Panjvin ophiolite belt. The poly metamorphic zone in this region is mainly related to the development and tectonic emplacement of the ophiolite. Some of the metamorphic rocks (Jade and its simulants) have so ​​hardness, density and high specific gravity, containing tremolite, actinolite, plagioclase, clinochlore, grossular and hydrogrossular garnet. Metamorphic rocks containing very condensed and compact tremolite and nephrite found in the area, as well as very compact antigoritic serpentinite so called bowenite, clearly proof that the high-pressure metamorphism took place during subduction. Serpentinites also appear in the region which is characterized by the predominance of antigorite and Cr-magnetite, as well as by their relatively low LOI (10.9-12.1 wt.%), corresponding to medium or high temperature blueschist facies metamorphism. These metamorphic conditions are strongly similar to the high-pressure metamorphic appearing in this serpentinites that formed from serpentinization of highly depleted harzburgitic protoliths where they were subjected to extensive partial melting processes (>15%), consistent with a hydrous subduction-related environment.  Gabbros in this ophiolite complex have been altered rodingitization, the altered rodingitized gabbros, in the continuation were underwent a de-rodingitization process too.

---

Isotropic gabbros of Kermanshah ophiolite include olivine gabbro, gabbro, gabbronorite, olivine gabbronorite and troctolite. The isotropic gabbros are medium to fine grained with euhedral to subhedral orthopyroxenes, clinopyroxenes and subhedral plagioclase, olivine together with rare amphiboles. Mineral chemistry of isotropic gabbros reveal that the clinopyroxenes are diopsidic to augitic in composition within the compositional ranges of En_{(50.91–45.79)}, Fs_{(7.41–3.64)}, and Wo_{(48.5–43.81)}. They are Ca-rich and Na poor (Na₂O < 0.54 wt%) characterized by high-Mg (Mg^# 85.62–89.35) and low-Ti (TiO₂ < 0.28 wt%) contents. Plagioclases are bytownite in compositions (An_{(70.51–90.15)}, Ab_(9.62-29.02) and Or _(0/00-0.63), orthopyroxene are mostly enstatites within the compositional ranges of En_{(78.27-84.94)}, Fs_(13.0-20.07) and Wo_(1.43-3.36), olivine, forstrite and amphiboles are Mg-rich (tremolite, actinolite to actinohornblendes) with Mg^# (64.35-84/86). The presence of highly magnesian olivines (Fo 80.07–84.82), clinopyroxenes (Mg^# 85.62–89.35), and orthopyroxenes (Mg^# 79.59–85.72) as well as highly calcic plagioclases (An 70.51–90.15) and amphiboles in the isotropic gabbros indicates a subduction-related tectonic environment. The tectonic discrimination plots of clinopyroxene data indicate island arc signature of the source magma. The results of studies confirm that the Kermanshah ophiolite formed in a suprasubduction zone environment in the southern branch of Neotethys

---

Sahneh, Harsin-Nourabad ophiolits (Kermanshah Provience) located in outer Zagros ophiolitic zone and are parts of the Cretaceous ophiolitic belt, as remnants of southern branch of the Neo-Tethys Ocean obducted over the Arabic–Tauric platform from Oman to northwestern Syria, Cyprus and Antalya. Calculation of Fe/Mg separation coefficient of olivine indicates the mantle origin of this mineral. Textural evidence of ultramafic rocks displays clear evidence of cooling with decompression, partial melting and melt-rock reactions. Tectonomagmatic discrimination diagrams show that peridotite samples are located in olivine- spinel mantle array and SSZ peridotite field. Based on geothermobarometry calibration the temperature and pressure of crystallization of harzburgite and lherzolite rocks were 1100 to 1500 ° C and 12 to 18 Kbar and the wehrlite sample was 1200 to 1500 ° C and 21 to 23 Kbar, which corresponds to the SSZ tectonic environment.