Sabzevar Ophiolite Zone (SOZ) is located in northern Central Iran (north of Great Kavir fault and south of Miamey fault) and separates Kopp e Dagh sedimentary basin (in the north) from the Central Iran plateau (in the South). The evolution and replacement time of this ophiolite complex has been in the Upper Cretaceous) Santonian – Campanian) and the Middle Campanian to Upper Maastrichtian respectively. This ophiolite belt contains a high amount of ultramafic rocks, small masses of gabbros and a thick sequence of submarine basaltic lavas with Upper Cretaceous pelagic limestone and radiolarite, which are angular unconformable and have a base of conglomerates of volcanic and sedimentary rocks. This study examines the brittle structures of SOZ and carries out a geometrical analysis. The purpose of this study is to obtain a suitable structural model consistent with the area structures. In this paper, the geometrical condition is compared with all the area structures and a logical relationship between fractures has been identified. Also the relationship between the regional macro-structures and area fractures has been identified. For this purpose during the field visits and study of the satellite imagery, structures and exposure which make the base of a structural map of the area have been provided.. Then with the surveyed data and provided rose and contour diagrams the main direction of fractures and the pattern of orientation were obtained. This direction is N59W, the same trend as the Miamey fault. The structures in the region are affected by this fault. If this direction is considered the main right-lateral shear trend, other trends are consistent with pattern of fractures orientations Related to fault cutting. Generally the fractures with N14E, N68E, N86E, N77W, N59W and N41W trend, respectively are consistent with type X, R', T, R, D and P fractures.

The Sabzevar complex ophiolite as a part of Khorasan ophiolite belt is located in 175 Km Northwestern of Sabzevar (L., 560 50' 20" and A., 360 35' 30"). These complexes are including igneous rocks consist of both peridotites (lherzolite, dunite and harzburgite), serpentinite, gabbros and a volcanic sequence composed of basalts, andesites, rhyolites and basanites. Based on the geochemical characteristics and petrographic observations, the mentioned rocks have been classified both in terms of tectonic settings and the chemistry. According to this research, it is proven that the basic to intermediate igneous rocks are very similar to that of Arc Island type setting rocks, and also very similar to each other in terms of genesis. It means, they are formed from unit melt segregation. But, the ophiolite complexes are very close to that of ocean ridge basalt-like composition, in the extrusive units of Neo-Tethyan. All of this rock unites could be the result of the oceanic spreading center development activities, when, through changing the extension regime to the compression one, it could penetrate into the previous continental plate to form colored mélange.        

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.

There are many chromite pods in the Sabzevar ophiolite but the high topography and mountainous condition and inability to trace the hidden lenses, many of them are not explored yet. A mathematical genetic model could be helpful to overcome the problem. So a very detailed investigation about the geology, mineralogy and petrology of the studied area has been done. The parameters that we need in the model are critical genetic factor (CGF) and critical reconnaissance criteria (CRC). Then with a linear combination of the factors, we have a function called intrinsic geological unit (IGU). By using characteristic analysis, the priority of each parameter would be defined. By running the model for Sabzevar area, a 3D space of lithological units would be highlighted which is called IGU. After running the program model, an area with a high precision of mineralization has been defined.

Sabzevar ophiolitic pillow lavas contain variolitic, porphyritic with microlitic matrix, intersertal and amygdaloidal textures and include plagioclase, clinopyroxene (augite-diopside), olivine, amphibole (magnesiohastingsite) and opaque minerals. The chemical composition of clinopyroxenes show a calc-alkaline magmatic series and a tectonic environment within plate alkaline basalts. Geochemically, these rocks are divided into two groups. Group 1 is basically calc-alkaline andesite with low TiO2 and group 2 is alkali basalt with high TiO2. N-MORB normalized trace elements diagram shows that group 1 is enriched in Th, U, La and depletion in Ta, Nb, Ti and group 2 is enriched in Th, Ta and Nb. Calc-alkaline rocks have produced in a subducted tectonic environment by a continental crust and erupted southwards on the Turan plate. In contrast, alkaline rocks formed within plate oceanic and then tectonically accreted in the forearc setting.

Research and experiences have shown that the geophysical exploration of chromite, compared to many other mineral ores, has been less confident and less successful. In Iran, many promising areas of chromite deposits have been left unplanned due to the lack of a definitive method for exploration and exploitation, which could cause economic prosperity for the area. In the present research, two geophysical methods, namely “electric resistivity tomography” and “very low frequency electromagnetic”, using 9 electromagnetic and 4 resistivity profiles, are used to identify chromite ore's geoelectric and electromagnetic properties. Laboratory studies, including electrical resistivity measurements on the rock cores and mineralography studies, have been conducted to evaluate the field results better. The resistivity was measured between 2800-3600 for one chromite ore, between 5500-8600 for the other, and between 2000-2300 Ω.m for a serpentinite, which is the chromite ore host rock. VLF-EM parameters (real magnetic field component) were obtained using different radio signals, including 29.6 and 18.1 kHz. The map of the real component of the vertical magnetic field of VLF-EM and the use of the Karous and Hjelt filter (1983) showed acceptable results in revealing fault zones and joints in serpentinized ultramafic rocks. The resulting maps showed that the lower resistances are along the faults and discontinuities in the rock, which are sometimes accompanied by chromite ore in their planes. I applied electrical resistivity tomography with the Wenner alpha array in areas with known chromite deposits, revealing, to some extent, that the zones with higher resistivity were related to chromite-bearing areas. The results of the interpretation of geophysical data were, in some cases, confirmed by the excavations and exploratory boreholes in the study areas. It can be concluded that if the required conditions are met, the methods employed can potentially reveal hidden chromite deposits..

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 orthopyroxene and low contents of TiO2 (<0. 06 wt%) indicating that harzburgites fall whitin the olivine-spinel mantle array (OSMA), and plot in abyssal and forearc peridotites fields and are residual of moderate degrees of partial melting (about 15 to 26%) from moderately depleted mantle. But, the content of Cr# in Cr-spinels of dunites, chromitites and pyroxenites are high (between 81-. 85%), and associated to boninitic melts and indicate that formed by high degrees of partial melting. Consequently, minerals chemistry of Cr-spinel, clinopyroxene, orthopyroxene and olivine of mantle section from Forumad ophiolite indicate that genesis of this ophiolite have been involved in a suprasubduction zone, and developed as a result of northward subduction of the sea/ocean of the Neo-Tethys in response to the convergence between the Central-east Iranian microcontinent and Alborz (Turan) plates.

In the eastern part of the Sabzevar ophiolite, southeast of Soleymanieh, there are white to pale greenish veins of diopsidite with 1– 15 cm width inside mantle serpentinized harzburgites. The center of these veins is rather homogeneous and includes a monomineralic clinopyroxen with granular texture. The contact between the pure clinopyroxene and its host peridotite is always progressive and characterised by replacement textures and minerals. The host harzburgite has also been affected by diopsidization. There are patches of cores grain altered plagioclase and clinopyroxen with inclusions of serpentine in the host harzburgite. The mineral assemblage, field relationships and mineral chemistry of the mantle diopsidites in the eastern part of the Sabzevar ophiolite indicate that they are product of circulation of very high temperature hydrothermal fluids (550– 900 ° C) rich in Si, Ca, Mg, CO4 2– , SO4 2– and Cl– in the upper mantle. These fluids leached plagioclase rich lithologies before penetrating the mantle.

Sabzevar ophiolitic belt is located in the northwest of Iran, north of Sabzevar. The current study is carried out for the first time in Iran with an exploration approach in the western part of the belt. Study of Platinum Group Elements (PGE) is of high importance for determining the genesis and economic evaluation of chromite deposits specifically in ophiolitic complexes. Chondrite-normalized PGE patterns of the chromitites related to ophiolites have a negative slope suggesting that during initial stages of magma crystallization, chromite preferentially removed compatible PGE from the magma. These patterns in the Sabzevar chromitites imply that these rocks are related to ophiolitic complexes (Alpine type). Chromite ore bodies which exhibit a relatively high incompatible/compatible element (Pd/Ir, Cu/Ni) ratios are derived from a more evolved magma with a lower fractional melting degree and do not seem to be of economic importance; this ratio in Al-rich chromites is higher than that of Cr-rich type. Pd/Ir ratio in Sabzevar chromitites on the average is less than 1, similar to many important chromite ore bodies related to ophiolitic complexes throughout the world. This ratio being low, as well as high chromium number (Cr/Cr+Al>0.60) suggests that this complex can be considered to contain a significant potential for economic and metallurgical chromite. Furthermore, the complex does not contain chromitites of uniform composition in chalcophile elements. PGE patterns of peridotites in the study area also show that these units in upper parts of the Gaft area are similar to ultramafic cumulates of oceanic crust, while in lower parts of Faroumad area related to mantle sequences.

Around Soleymanieh village in the NE of Sabzevar, there are a numerous gabbros and microgabbros dykes that have interruped Sabzevar's ophiolites. Most of these dykes turn from black to green, white, yellow and reddish. The surrounding ophiolites have highly altered to serpentine, too.The petrographic studies of discoloured dykes show that, olivine, clino- pyroxenes, orthopyroxenes and calcic plagioclases, (high energy level minerals) have been converted to: wolastonite, prehnite, chlorite, epidote, hydrogrossular, pectolite, and xenotlite (low energy level minerals).Furthermore: XRD, thermic analysis and micropropic studies confirme the mineralization studies and rodingite reactions recognized by polarized microscope. Assemblages minerals and textures show that this complex is a rodingite association. Generally, rodingite mechanism start with serpentinization of olivine and pyroxenes in harzburgites and lherzolites and release of Ca+2 from their structures. These Ca+2 cations can not be accommodated in serpentine crystal structure, therefore, they are concentrated in the fluid associated with serpentinization. Oversaturated fluids of calcium, and with low amount of CO2, under suitable condition, (presence of reactional rocks like gabbros) react with above meantioened rocks and form calcium rich minerals. These fluids will react with basic roch minerals especialy Plagioclasis and creat a host of roddingites minerals (Xenotlite, grossular, Pectolite and others). In Some cases, somme minerals, such as pectolite and xenotlite are replaced in the form of veins within rodingites.