جستجوی مقالات مرتبط با کلیدواژه « peridotite » در نشریات گروه « زمین شناسی »

Ophiolites are slices of oceanic lithosphere obducted onto a continental margin and can be classified as mid-oceanic ridge (MOR) or suprasubduction zone (SSZ) types based on the tectonic setting in which they originally formed (Pearce et al., 2000; Shervais, 2001). The Zagros Orogen extends from eastern Turkey through northern Iraq and northwest of Iran to the Hormuz Strait and Oman (Alavi 1994; McQuarrie, 2003; Homke et al., 2004; Agard et al., 2005; Shafaii Moghadam et al., 2018). The geodynamic evolution of the Zagros Belt is mainly related to the opening and closure of the Neo-Tethys oceanic basin. Ophiolites, as Neotethys oceanic lithosphere remnants, are emplaced along the Zagros Orogen. These ophiolites are emplaced along two main belts (Saccani et al., 2013; Shafaii Moghadam et al., 2018). The Neo-Tethys suture zone coincides with the Main Zagros thrust fault (Agard et al., 2005) and ophiolites are exposed scattered along this zone. 

The Dalampar ophiolite, located between the Piranshahr and Salmas ophiolites. The Dalampar ophiolites consist mainly of strongly sheared serpentinized ultramafic rocks including harzburgite, dunite overlaid by gabbro and basalt units. The emplacement mechanism of the Dalampar ophiolite massifs into the Iranian microcontinent and structural evolution is completely unknown. There has been not performed a systematic investigation of these ophiolites and geodynamic and relation with other ophiolites are not well Studied.
Thus, the main purpose of the present paper is to investigate the petrogenetic processes, tectono-magmatic environment, using mineral chemistry and textural evidences of Dalampar ophiolite which are fundamental for understanding the tectonic evolution of the Neo-Tethyan Ocean.

During the fieldwork, a number of suitable peridotites samples with least alteration effects were selected. Folloing the petrographic studies, a thin polished section was prepared from several harzburgites for microprobe analysis using JEOL JXA-8600 M model,15 kv accelerator voltage and 2-ray current 10-8 Amp, placed at the Department of Earth Sciences and Environment of Yamagata University, Japan.

Harzburgites are the most basic and widespread ultramafic units in Dalampar ophiolite complex. They show evidences including the presence of exsolution of clinopyroxene in orthopyroxene, the orientation and elongation of the crystals indicating these rocks were formed in the upper mantle conditions and reached equilibrium in the crustal environment. Exsolutions of clinopyroxene lamellae from orthopyroxene are one of the textures observed in the rocks under study and is widespread in both abyssal and SSZ peridotites (Tamura and Arai, 2006). The Cr# of spinel in abyssal peridotites is a good indicator of the degree of partial melting for the mantle-derived spinel peridotite. Low Cr# spinels represent less depleted peridotites, whereas the high Cr# spinels highlight more depleted peridotites (Dick and Bullen, 1984; Arai, 1994). in the Mid-oceanic ridges, the degrees of partial melting and depletion are generally low. In contrast, the supra-subduction zone peridotites have a high degree of partial melting and depletion (Niu and Hekinian, 1997). The content of Cr# in presented Cr-spinels are high (78-83%), and associated with boninitic melts formed by high degrees of partial melting or much more extensive melt-rock reaction (Arai, 1994). As the the Cr# of spinel versus the Fo content of olivine diagram shows the harzburgites fall in SSZ domain. Furthermore, all rock types fall into olivine-spinel mantle array (OSMA). This is regarded as the evidence for their residual origin, i.e. they form a trend which was likely caused by partial melting. Experimental studies confirm that the Al2O3 and TiO2 contents, as well as FeO/MgO ratios in chromian spinel are directly related to those of the parental melt (Rollinson, 2008). According to Maurel and Maurel (1982), The Al2O3 contents of the parental melt range from 10 to 11 wt. % for the studied Harzburgites. Such values are consistent with boninitic melts, which typically contain 10–14 wt.%, respectively (Dilek and Thy, 2009). In the Cr# versus TiO2 diagram, the Dalampar peridotites classify as depleted peridotites. In consequence, chemistry of the chromian spinels in the Dalampar peridotites are compatible with a genesis in a suprasubduction zone from boninitic or primitive arc magmas. However, forearc regions may contain both SSZ and abyssal peridotites, although the former are typically dominant (Pearce et al., 2000). Olivine-spinel and orthopyroxene-clinopyroxene thermobarometry in the harzburgites shows equilibrium temperatures of 1000-1100 ºC at a pressure of 28 kbar and suggests that they have been equilibrated in spinel peridotite field.

The Dalampar Ophiolitic Complex as a part of the Tethyan ophiolites is exposed in the northwestern part of the Iranian-Azerbaijan province, extending to the Anatolian ophiolites in southeastern Turkey. The petrography, geochemistry and microstructural studies of the residual mantle sequence in Dalampar Ophiolitic Complex provide important information regarding the degree of partial melting and deformation in the oceanic mantle lithosphere. Mineral chemistry clearly indicate that Dalampar ultramafic rocks record an episode of boninitic magmatism occurred within the southern Neo-Tethys Ocean in the Late Cretaceous. Boninitic melts in Dalampar Ophiolites were formed by partial melting of depleted peridotite, a residue after MORB-type melt extraction. Mineral chemical data indicate that SSZ peridotites are the residues from ∼30–40% of mantle melting. Nonetheless, the very low (< 0.25 wt. %) TiO2 calculated for the parental melt in equilibrium with chromian spinel are only consistent with boninitic-type parental melts. Based on geothermobarometry calibration the temperature and pressure of crystallization of harzburgite rocks were 1000 to 1200 ° C and 24 Kbar, corresponding to the SSZ tectonic environment.

Shesat Pich region hosts an ophiolitic complex located in the south of Kerman, southeast of Iran. This ophiolitic complex is composed of lherzolite, harzburgite and dunite. Olivine is one of the important minerals found in these rocks, which is observed along with pyroxene (orthopyroxene and clinopyroxene) and spinel in the rocks of the region. The combined range of olivines in the region is in the forsterite range of 84 to 92% and ranges from forsterite to chrysolite. NiO with an average amount of about 0.38% by weight and MnO with an average of 0.14% by weight in olivines show the range related to abyssal peridotites. In addition to serpentinization as a general change in the ultramifics of the region, petrographic studies show evidence of metamorphism in the olivines of some harzburgites along with recrystallized antigorite crystals, which indicate a phase of thermal metamorphism in this harzburgite. These results have been confirmed in mineral chemistry studies too. Metamorphic olivines have an abnormality compared to magmatic olivines with a decrease in calcium. In chemical mineralogical studies, the amounts of forsterite and olivines show a regular increase from lherzolite to harzburgite and dunite. Raman spectroscopy studies on the studied olivines show the relationship between the peak shift of 854 waves/cm and forsterite values of olivine minerals in the region.

The mantle sequence of the Kuh-Siah ophiolitic suite is located in N Sabzevar, Central Iran structural zone and consists mainly of harzburgite, dunite, lherzolite, pyroxenite, and chromitite lenses.  The Fo% of olivines in peridotites ranges between 91-96%, and plotting them in the Ezubonin-Mariana peridotites. The Al2O3 content of orthopyroxene in harzburgites and lherzolites is relatively low, showing a tendency towards orthopyroxenes of forearc-abyssal peridotites. The clinopyroxene in the pyroxenites also has low Al2O3 and TiO2 content and placing it in the forearc peridotite field. While this mineral in harzburgite and lherzolites have a higher content of Al2O3 and TiO2 and plots in the abyssal peridotites field. The spinel in lherzolites resemble oceanic peridotites, while in harzburgites, it shows a tendency towards forearc and oceanic peridotites. The spinels in dunites exhibit high Cr# and appear to be derived from a boninitic melt in high degrees of partial melting from a depleted mantle source under hydrous conditions. Based on minerals chemistry characteristics (indicating the dual nature of the MORB_IAT_BONINITIC), the evolution of this mantle sequence has been involved in a supra-subduction zone, resulting from the northward subduction of the sub-branch of Neotethys Ocean (Sabzevar suture) beneath the Alborz during the Cretaceous.

The subduction and closure of the vast Neo-Tethys ocean between the Arabian and Eurasian plates has left numerous ophiolitic traces, the unique position of Iran in its central part is noticeable. The lack of information, right on the border of Iran with Iraq and Turkey, due to security considerations, has so far prevented the overview of this suture zone in the northwestern border of Iran. Adding Gysian ophiolite in southern Urmia as a missing link in this stretch can partially cover this lack of information. A comparative study of whole rock chemistry of serpentinites in the central part of the Neo-Tethys ophiolites, considering several sectors from Iran (Kamyaran, Marivan and Gysian), Iraq (Penjwin and Mawat) and Turkey (Guleman and Osmanie) in this article, indicates that they belong to subducted serpentinites, whether they were originally formed in the fore-arc environment or the at abyssal oceanic environment. Composition of the serpentinites of the central part of the suture zone is similar to the average global serpentinites which have mostly lizardite/chrysotile. All of them show depletion of Mg resulting sea floor alteration during serpentinization. The mentioned point may be caused to data deviation from abyssal peridotites field. Considering that the transition metals contents the confirmed the above setting. Almost all of the studied serpentinites are from subducted type which indicates refertilization of LILE evidences as a result of rock/fluid interaction through serpentinization.

The petrographical examination of peridotites of the Nehbandan ophiolitic complex revealed that the peridotites of Kalateh Shahpouri, Qadamgah, Lah-Kouh, Cheshmeh anjir, Bandan, and Zolfaghari were of harzburgite type and Sefid-Kouh and Nasfandeh-Kouh were of lherzolite type. Generally, the types of clinopyroxenes in the peridotites of this complex were diopside. The geochemical investigation of clinopyroxenes in Mg# vs. Al2O3, Cr2O3, and TiO2 graphs and Ti vs. Nd, Zr, and Sr graphs shows that the peridotites of Nasfandeh-Kouh, Bandan, Zolfaghari, and Sefid-Kouh with a low degree of partial melting belong to the Abyssal tectonic setting and back-arc basin.on the other side, the harzburgites of Kalateh Shahpouri and Cheshmeh anjir were formed in the Supra-subduction zone tectonic setting and fore-arc basin and have a high degree of partial melting. The study of incompatible elements, LILE and HFSE in spider diagrams normalized to the primary mantle and as well as the study of REEs in spider diagrams normalized to the chondrite for clinopyroxenes confirm this issue. Therefore, Nasfandeh-Kouh and Sefid-Kouh lherzolites as well as Qadamgah, Lah-Kouh, Bandan, and Zolfaghari harzburgites with a low degree of depletion were more consistent with the Mid-oceanic ridgestectonic setting, and the harzburgites of Kalateh Shahpouri and Cheshmeh anjir were close to the Supra-subduction zone tectonic setting with a high degree of depletion.

The Heydarabad ophiolitic melange is hosted by the Nehbandan Ophiolite Complex (NOC), which crops out in the Sistan Suture Zone (SSZ) that marks the boundary between the Lut and Afghan continental blocks. The major rocks of this area include mantle peridotites, listwaenite, gabbronorite, cumulate and layered gabbro, pillow basalt and deep-sea pelagic sediments that were formed in the mid-ocean ridge (MOR). Olivine, orthopyroxene, clinopyroxene and spinel are rock forming minerals of Heydarabad ophiolite mantle peridotite.

After field studies, thin and polished sections were prepared for petrological and mineralogical studies. Whole-Rock major and some trace elements were obtained by X-ray fluorescence (XRF) spectrometer for SiO2, TiO2, K2O, Al2O3, FeO, CaO, Na2O, Cr2O3, MnO, MgO and NiO. Trace element and rare earth element (REE) concentrations were determined by using a Thermo Series X-I inductively Coupled Plasma Mass Spectrometer (ICP-MS). Also, 8 thin- polished samples (least fractured and altered) of wall rock were analyzed by electron probe microanalysis (EPMA), using a Cameca SX100 at the Iranian Mines and Mineral Industries Development and Renovation Organization (IMIDRO) with a 1-3 μm spot size, 20 nA beam current and a 15 kV acceleration voltage.

Most of the olivines from mantle peridotites are serpentinized. The detailed electron microprobe study revealed very high Mg# (62.4 to 67 wt.%), Cr# (18.1 to 34.5 wt.%) and very low TiO2 content (averaging 0.05 wt.%) for chromian spinels in mantle peridotites. The Fe+3 is very low (averaging 0.02 wt.%) in the chromian spinel of mantle peridotites which reflects crystallization under the low oxygen fugacity. The composition of olivine shows that forsterite type (Fo90.07-90.90), orthopyroxene is enstatite, clinopyroxene is diopside and spinels are Al-rich Cr-spinel. Tectonic environment discrimination diagrams for the harzburgite and lherzolite shows abyssal environment.

Hyderabad ophiolite melange consists of peridotite rock units (serpentine and listonite), lherzolite, gabbro, gabbronorite, plate dykes, and pillow lava, which are faulted. The mantle peridotite of this area is composed mostly of harzburgite and lherzolite. Based on mineral chemistry studies, harzburgite and lherzolite have olivine which is forsterite, orthopyroxene which is enstatite and clinopyroxene that is diopside. The peridotites of the study area contain Mg-rich olivines, Cr-spinels and Al-orthopyroxenes and are in the range of deep peridotites based on spinel and olivine chemistry. Also, high Mg value in mentioned minerals and high percentage of forsterite in olivines indicate the tectonic origin of these rocks. Orthopyroxenes and clinopyroxenes are Cr-rich, indicating limited partial melting of peridotites. Mineralogy studies show the relationship of these rocks with the oceanic environment. The composition of spinels in the peridotites shows that the type of high Al, with Mg and Cr is 62.4 to 67 wt% and 18.1 to 34.5 wt%, respectively. They are considered as spinels formed in Abyssal peridotites. Geochemical studies show that Hyderabad peridotites are mantle peridotites that are formed by melting 11 to 16% of a prepared mantle of lherzolitic spinel. The composition of chromium spinels in these peridotites is in the Alpine type range and their tectonic environment is more compatible with MOR peridotites.

Oxygen fugacity (fO2) and zircon crystallization temperatures (Ti-in-zircon) of ore-bearing quartz monzonite intrusive rocks of ChahShaljami and Dehsalam Cu-Mo porphyry deposits were measured by using calculations of zircon trace element values and oxidation conditions of parental magma were investigated. The Ce4+/Ce3+ values for ChahShaljami and Dehsalam are in a range of 8 to 295 with an average of 125 and 3 to 171 with an average of 35, respectively, therefore they were not in the favorable range for porphyry mineralization. The estimated fO2 values for ChahShaljami and Dehsalam are in the range of ∆FMQ -1.8 to MFMQ +0.6 with an average of ∆FMQ -0.6 and ∆FMQ -1.3 to ∆FMQ -0.4 with an average of ∆FMQ -0.8 which is at least ∆FMQ +1 less than the values of porphyry copper mineralization in the world.. Based on the zircon log fO2 values of ore-bearing intrusive rock, the parental magma originated from partial melting of supra-subduction mantle peridotite zone within oceanic slab. Melting under unfavorable conditions (under magnetite-hematite (HM) buffer and in faylite-magnetite-quartz (FMQ) buffer condition, and lack of sufficient Cu and sulfur at the source), which is supported by evidences in deposit such as lack of magnetite-hematite intergrowths, was not ideal for porphyry Cu porphyry mineralization in the two regions. The results are supported also by previous whole-rock major and trace element geochemistry and Sr-Nd isotopic values.

The mineralogical composition and geothermobarometry of the peridotites from the Marivan-Kamyaran ophiolitic complex, as a part of the Neo-Tethyian ophiolites in the Zagros Mountains, western Iran, are investigated. The studied samples are belonged to mantle and crustal peridotite types. Results of electron probe microanalysis in peridotites indicate that olivine is forsterite (Fo87-Fo92), clinopyroxene is augite-diopside (En48-56Fs3-6Wo39-49) and orthopyroxene is enstatite (En90-91). Cr-number (Cr#) and Al-number (Al#) in spinels of the mantle peridotites are 33-59 and 41-67, respectively. The same values in spinels of the crustal peridotites are 67-98 and 2-32, respectively. Geothermobarometry calculations for the mantle peridotites show average temperature of ~1104°C and average pressure of ~14 kbar. The crustal peridotites are formed at ~900 °C and ~7 kbar. Two distinct mineral chemistry of the mantle peridotites indicate existence of two types of mantle peridotites in the area, suggesting the possibility of the influence of melt-rock interaction on the chemical composition of the mantle peridotites in the area.

The study area known as ‘Chahar-Dahaneh’ is part of the Iranian southeast ophiolites related to Alpian-Himalayan Mesozoic orogeny belt, and is located in the western margin of the Makran subduction zone. Chahar Dahaneh peridotite section consists of three major lithologies including: 1.dunite lenses 2. harzburgites and 3. Lherzolite. Based on electron microprobe analysis ,we estimated pressure of 5kb with 10%wt H2O for magma with temperature of about 1150-1200C for the origin of clinopyroxene crystallization and chrome spinels are ferrian palenaste in composition. Enrichment of Al3+ ratio to Fe3+ in spinels from lehrzolites suggest that they formed in lower oxygen fugacity and higher pressure than those spinels in dunites and olivines are forsterite in type with  88-91 Mg#. Based on microprobe datas, Chahar Dahaneh peridotites are related to back arc metasomatised mantle in SSZ tectonic setting.

Weathering is one of the important and controller factors of the physical and mechanical properties of peridotites. The engineering properties of rocks undergo significant changes due to the weathering process. Weathering depends on the mineralogical composition and peridotite texture properties. In this research, the effects of mineralogical characteristics of Harsin peridotites in Kermanshah province were studied. The studies Contains Field surveys and laboratory studies. In vitro studies, thin sections of peridotites were first considered with different weathering conditions. Then, by performing physical and mechanical tests, specific gravity, unit weight, moisture content and porosity were determined, respectively. In the following, the values of unixial compressive strength, Young's modulus, point-load index and hardness of samples were calculated. In this study, due to the mineralogical characteristics and the degree of weathering of the peridotites, based on the degree of serpentinization of the rock in each stage of weathering, the effect of these factors on the engineering properties of the rock was evaluated. By using Excel 2013 regression correlation software the relationship between weathering, mineralogy and texture properties was determined by geological characteristics of peridotite engineering. These relationships have been linear functions. Also, F, t tests confirmed the 95% confidence level of proposed experimental relationships. Based on the results, the highest correlation 0.95, is founded between the point-load indexes with the index of micro-cracks. The results obtained in this study showed that the importance of texture properties is more important than mineralogical properties in determining the geological engineering properties of rock. This means that the characteristics of kernel such as shape and size, type of contact, degree of weathering, and the index of micro-crack shave an important effect on the geological characteristics of the engineering of peridotite rocks.

Because of the diversity in petrography, peridotites have variable physical and mechanical properties. For this reason, knowledge of resistance properties and their deformation will help with the prediction of engineering behavior of these rocks. Due to the large spread of igneous rocks, especially peridotite, in Zagros, northeastern and central Iran, special attention has been paid to their petrographic, physical and mechanical characteristics. The construction of the structure within or on the peridotites and the choice for the purpose of the stone borrow depends on the recognition of its engineering geology characteristics. In this paper, in addition to the field and laboratory study, the geological characteristics of peridotite engineering has been investigated.

In order to study the geological characteristics of the peridotites of Harsin region, 15 suitable blocks were selected and transferred to the laboratory. Accordingly, from collected rock samples, 150 cylindrical cores of diameter 54 mm were prepared and physical and mechanical tests were performed according to (ISRM, 2007) and (ASTM, 2001) guidelines. In this research, after sampling of the study area and preparing the core for the lithological characteristics of the samples by providing thin sections of them with polarizing microscopy was studied.

By considering the results of laboratory tests and analysis from Harsin peridotites in Kermanshah province, we can acclaim that with increasing the percentage of minerals in olivine and pyroxene in rock, the strength was decreased and the levels weaknesses, which is due to the weak structure of the mineral-olivine and pyroxene. According to the physical properties test and Anon classification, the porosity percentage in porosity percentage is low and as a result the amount of water absorption index is low. Based on the Gamble classification, all peridotites are very resistant to durability and based on the Franklin and Chandra classification, all samples are extremely resistant. The results of this study showed that the single axial compressive strength, elasticity modulus, point load index and tensile strength were decreased with an increase in humidity content of peridotite samples. This is due to the fact that with the increase of humidity pore pressure of water increases. According to the Anon classification, the peridotites are very high in terms of the length of the longitudinal passage through the rock. The highest compliance between the Brazilian Tensile strength test (BTS) and Schmidt hammer (SHV) was achieved in the dry condition and the determination coefficient (R2) equals to 0.95 was obtained. Also there is an acceptable relation between the Brazilian Tensile Strength Test (BTS) and the dry volume unit weight (γd) with the determination coefficient (R2) of 0.93. In addition, there is an admissible relationship between durability test and single-axial compressive strength, with a coefficient determination (R2) of 0.94. Regarding the obtained regressions in this study, the physical and mechanical properties show good agreement and most of the equations have an acceptable coefficient determination.

Forumad area is located in NW of Sabzevar, in NE of central Iran structural zone and in western part of Sabzevar ophiolite suite. The mantle section of Forumad ophiolite consists mainly of harzburgites, dunites, pyroxenitic dikes and choromititic lenses that contain brown to black Cr-spinels. The content of Cr2O3 and Al2O3 of Cr-spinels in harzburgites are between 32.6-53.1 and 15.6-34.8 wt%, respectively, and their Cr# ([100 × Cr/(Cr + Al]) atomic ratio]) is between 39- 69%. Relationship between Cr# of Cr-spinels and Fo of coexisting olivine (Fo=91-92%) and low contents of TiO2 (

Niabad-Qalaje ophiolitic complex is part of Sarvabad ophiolites in Kurdistan that exposed in northwest of Iran and the north of Kermanshah Ophiolites. The complex located in north of Zagros orogeny, consists of lens form, tectonically dismembered ophiolitic sequences located along the main Zagros trust. The ultramafic part includes serpentinized dunite and wherlite, serpentinite and chromitite that outcropped as consecutive lenses. Small lentiform chromitites present podiform and shear fabrics. The major minerals in peridotites are olivine (Fo= 88-91), clinopyroxene and chromian spinels.  Low Ti value and high content of Al and Cr# in peridotite chromian spinels reveal a high rate of partial melting (25-35%). Mineral chemistry and whole-rock chemistry clearly indicate that the Kurdistan ultramafic cumulates and chromitites record an episode of boninitic magmatism.  Boninitic melts in Niabad-Qalaje ophiolites were formed by partial melting of a depleted peridotite which made up the residual mantle after MORB-type melt extraction. The chemistry of peridotites shows the abyssal to supra-subduction zone source. Comparing the lithological and geochemical characteristics of the studied ophiolites with some other complexes in the world denotes that the Kurdistan ophiolitic complex formed in a fore arc basin close to the Sanandaj-Sirjan zone continental margin.

Rock strength parameters, especially the Brittleness is one of the most important features controlling the behavior of the rock material.Brittleness is a function of strength, which indicates the rock strength against deformation in the elastic range. rock damage is largely the function of rock properties.
Given the Brittleness of engineering projects stones are crucial and direct methods for measuring the Brittleness not standardized, in this study using p-wave speed test, dry density, water absorption percent, Schmidt hammer test, Point Load Test and also Single Axial Compressive Strength Brazilian elasticity on 10 samples of peridotites located in Harsin, Kermanshah Province to determine the implications of Brittleness fracture parameters determined by physical and mechanical characteristics.
According to the results, there is no reasonable and acceptable relationship between dry density and sound speed tests with the brittle rock.The highest adaptation between water absorption test, Schmitt hammer test and point load testwith brittleness indexes is BI , BI B3. That The correlation coefficient of these indices is 0.76(r) , 0.79(r) and 0.98(r) Respectively.
In fact, the mechanical properties of these rocks toward the physical properties are more consistentwith Brittleness index

The studied area is located in the north of Rudan city and is a part of Kahnuj - Rudan - Minab ophiolite belt. The studied rock are harzburgite and lherzolite and are composed of olivine, orthopyroxene, clinopyroxene and chrome – spinel (as a minor). According to microprobe data, the amount of MgO in the olivines ranges between %50.17 to %50.55, so these olivines are forsterite. Clinopyroxenes are diopside and spinels contain chrome. Detail microprobe studies on the chrome - spinel of ultramafic lherzolites prove that they are high in Mg#(%71-%77) and Al2O3 (52.98 to 46.31 Wt%) ) and low in Cr# (%0.14 - %0.22). (Cr/Al) ratio in the spinel of lherzolites is 0.19. The amount of Fe3 in the chrome - spinel of ultramafic Peridotites is very low (

The LerdGarm peridotite complex is one of the ultramafic complexes in south-east Iran . This complex is composed mainly of harzburgite dunite, lherzolite, and secondary listvenite and magnesite. The detailed electron microprobe study revealed very high Cr # (39.9-64.0), Mg # (51.2-65.63) and very low TiO2 content (averaging 0.05 wt %) for chromian spinels in peridotites. The Fe3# is very low (C± 60 at a pressure of 26 Kbar. Tectonic environment discrimination diagrams for dunites show a suprasubduction environment of the arc setting and for the harzburgite and lherzolites show abyssal environment.

The Neyriz ophiolitic complex with NW-SE trend، is located parallel to and out of the Main Zagros Thrust. Mantle sequence of this ophiolitic complex، is comprising predominantly of harzburgite and minor lherzolite، dunitic sheaths and chromite pods. Base on petrographic studies، the essential minerals of these rocks are orthopyroxene، clinopyroxene and olivine; and chrome spinel is present as secondary phase. Geochemical studies show that these samples are enriched in refractory elements. On spider diagram normalized with the primitive mantle، large ion lithophile elements (LILE)، show enrichment relative to the high field strength elements (HFSE). On petrogenesis diagrams، the studied samples lie on island arc and supra-subduction zone environment. These features suggest a depleted source for these rocks، and are characteristics of magmas that formed at a marginal basin in a supra subduction zone environment.

The study area is located in the Soredal mountains, southern Mashkan village in the border of Iran with Iraq. The rock compositions are harzburgite to dunite which metamorphosed under various degrees of serpentinization. On the basis of mineral chemistry studies, main compositions of olivine and orthopyroxene are Fo (85.07- 91.55) and En (0.89- 0.92) respectively. Composition of clinopyroxene is diopside and Al/(Al+Fe3++Cr) ratio is between 0.02 and 0.57. Spinel end- member composition is as Mag (0.04- 0.06), Chr (0.62- 0.66) and Spl (0.51- 0.58). Mg number of spinel is varied between 0.52- 0.62 and Cr number is about 0.59- 0.69. The mineral chemistry studies indicate an oceanic property of the Soredal peridotites. The rocks are formed in forearc supra-subduction zone (SSZ) setting. The investigated rocks in the  the end part of north western Zagros ophiolitic belt are remnants of oceanic lithosphere of southern branch of Neo-Tethyan which are formed during late Cretaceous between Arabian (toward south) and Eurasia (toward north) continental margins. They are very similar to Kermanshah and Iraq ophiolites in the ophiolitic Zagros belt.

The objective of this study was to investigate the clay mineralogy of soils derived from different parent materials in Binaloud zone, western Mashhad. Two soil profiles on the summit of granitic, ultrabasic and metamorphic rocks were described and sampled from genetic horizons. Clay fraction of the soils was analyzed using X-ray diffraction method. Chlorite, smectite, mica, amphibole and regularly interstratified chlorite/smectite and chlorite/mica are the most important clay minerals in the studied soils. Chlorite in ultrabasic soils and parent material of metamorphic soil is Mg-rich in contrast to Fe-rich chlorite in granitic soil. Amphibole was common in ultrabasic soil and metamorphic soil had much less amphibole. The eolian origin has been identified for mica in ultrabasic soil. As a result of higher weathering intensity in ultrabasic soil, the aboundance of regularly interstratified clay minerals were higher than the other soils.