فهرست مطالب سیدمحسن طباطبایی منش

The occurrence of tourmaline in the metamorphic complex of the north of Golpayegan is observed within the granitoid mass and schists in contact with granitoid and marbles. Speaking of abundance, tourmaline is less frequently a minor mineral found in granites and granitic pegmatites as well as in low- to high-grade metamorphic rocks (Krmícek et al., 2020). The minerals of the tourmaline group can adjust their composition to adapt to varied settings, and therefore show a remarkable stability range in terms of pressure, temperature, fluid composition, and host rock composition (Van Hinsberg et al., 2011). Since tourmaline displays a negligible intra-crystalline diffusion, it can record the physical and chemical conditions of its setting and preserve this information in geological chronicles. Therefore, tourmaline accurately presents the composition of fluids and the melts from which it crystallized (Marks et al., 2013). Although tourmaline is common in many rocks, it is not common in metamorphosed carbonates (Krmícek et al., 2020).A petrographical and geochemical investigation of tourmalines in the north of Golpayegan was undertaken to know the formation mechanism of this mineral and to determine the differences between tourmalines crystallized at the contact, in granitoid and tourmaline in marbles.

Regional Geology:

The Golpayegan Metamorphic Complex is located in the Sanandaj-Sirjan Zone and the occurrence of tourmaline in this complex is observed in two locations. The first location is on the west side of Ochestan farm where tourmaline is found in three forms:1) In the granitoid mass (Gt); 2) In the amphibole schists (At) in contact with the granitoid mass, and 3) In the mica schists (Mt) in contact with the granitoid mass. The second area is in the north of Esfajerd where tourmaline occurs inside the marbles (Ct).

With the completion of field reconnaissance and preparation of thin sections, a petrographic study was fulfilled to determine the texture and mineralogy of the minerals, and then, some samples were selected for electron microprobe analysis.

Petrography:

The tourmaline in granitoid mass (Gt), appears as idiomorphic and coarse-grained without any inclusions. Micaschists (Mt) in contact with the granitoid mass are sieve-shaped or spongy. Inside the amphibole schists (At) in contact with the granitoid mass, it is idiomorphic without any inclusions.Tourmaline in marbles (Ct) is fine-grained and blue, which can be observed around biotites with corrosion marks, indicating its reaction with fluid.

Tourmaline chemistry:

The tourmalines in Ochestan granite-pegmatite (Gt) are of alkali tourmaline variety with schorl composition, enriched in aluminum, and points to the replacement of Al in the Y (R2) position. The substitution type of these tourmalines is Al(NaFe+2)-1 owing to the high amount of Fe versus Mg,The tourmalines in amphibole schist (At) are alkali tourmaline with schorl-dravite composition and the tourmalines in mica schist (Mt) are alkali tourmaline with dravite composition, and both types are characterized by insignificant amounts of aluminum. This demonstrates the replacement of Al in the position of Y (R2) has not occurred. Due to the change in Mg and Fe content, the At-type tourmalines benefit from both Al(NaFe+2)-1 and Al(NaMg)-1 substitution varieties. However, the substitutions of Mt-type tourmalines are mainly Al(NaMg)-1 due to the high content of Mg versus Fe. Indeed, Fe+3Al-1 substitution can be observed in both types of tourmaline.Tourmalines in marble (Ct) are of the alkaline type of dravite composition and rich in aluminum, which indicates the replacement of Al in the Y (R2) position. Their substitution is Al(NaMg)-1 due to the high content of Mg versus Fe.

The composition of tourmaline in Gt is of schorl type (Fe/Fe+Mg= 0.89-0.91) and has an aluminum replacement in the Y position. The composition of tourmaline in Mt type is of dravite type (Fe/Fe+Mg= 0.45-0.47) and the composition of tourmaline in At type is of schorl-dravite type (Fe/Fe+Mg= 0.49-0.51), which, replacement of aluminum in the Y position does not occur in both types of tourmaline in schists. Consequently, hydrothermal tourmalines have less aluminum (i.e. At and Mt-type tourmalines), and tourmalines in the granite-pegmatite mass have much more aluminum (i.e. Gt-type tourmalines). Based on the values of Fe# (FeO/FeO+MgO), it is possible to determine the formation site of tourmalines. If the amount of Fe# in tourmaline is >0.8, it indicates the closed magmatic system, lack of fluids interference, and their contamination with Al-rich sediments. Meanwhile, if the ratio is <0.6, it means that boron is metasomatic with sediments rich in Al and also is of an extrinsic origin.The Gt tourmaline samples in the range of Li-poor granitoids and related pegmatites and aplites related to them, the At and Mt tourmaline samples placed in the range of Ca-poor metapelites, metapsammites and quartz-tourmaline rocks not coexisting with an Al-saturating phase.The tourmalines in the marbles of the north Esfajard (Ct) are of dravite type with the ratio of Fe/Fe+Mg= 0.42-0.45. In these tourmalines, both aluminum replacement in the Y position and Al(NaMg)-1 substitution can be observed, which manifests the non-magmatic origin of these types of tourmalines. The Ct-type tourmalines in the range of metapelites and metapsammites coexist with an Al-saturating phase.The postmagmatic/residual-hydrothermal fluids related to alkali syenite magma of the north Esfajard along with the fluids from the progressive metamorphism in micaschists, have developed these tourmalines in marble.The discrepancy in the results of two types of thermometers (thermometry based on the amount of Ti in biotite and Mg-Fe exchange between tourmaline and biotite minerals) in meta-carbonates, highlights that at temperatures >566°C biotite, and lower temperatures, Ct-type tourmaline is composed of biotites.

Based on field observation and petrographic evidence, by progress in metamorphic degrees, a wide variety of metabasites have formed following the metamorphism at amphibolite facies (metamorphism M1) in the east of Jandaq. Thermobarometry of plagioclase- amphibole pairs indicate temperature ranges were 642-692ºC  and 688-712 ºC for epidote amphibolites and garnet amphibolite, respectively, in a pressure range of 8 and 11 Kbar, correlating with transition from middle amphibolite to upper amphibolite facies. In addition to this metamorphic phase, petrographic signatures indicate further metamorphic phases concerning this region's geological phenomena. Based on brittle deformation in amphiboles, and epidote and quartz formation in their fractures, these rocks have undergone some degrees of retrograde metamorphism (<700 ºC; metamorphism M2) at greenschist to lower amphibolite facies. Rock foliation and mineral orientation, aggregate shape preferred orientation (ASPO) of titanite crystals along foliation, and syn-tectonic euhedral garnets indicate prograde metamorphism toward amphibolite-upper amphibolite facies (metamorphism M3). Finally, under greenschist facies condition, minerals such as chlorite and actinolite were formed in these rocks (metamorphism M4). The formation of chlorite and actinolite in the rims of the primary crystals shows that these rocks were finally affected by metamorphism at greenschist facies (M4 metamorphism).

Granitoids are one of the most abundant and common igneous rocks in the continental crust and they formed the world's largest batholiths. They are widely distributed in Precambrian to Cenozoic orogenic belts (e.g., Raymond, 2002), but some are formed in non-orogenic zones (Blatt et al., 2006). Because much of the continental crusts in orogenic belts are composed of granitoids, they are of particular importance in explaining the petrologic processes in orogenic belts.Cenozoic magmatism of Urmieh-Dokhtar magmatic arc is intruded by Oligo-Miocene plutonic rocks in some regions (Arvin et al., 2004). An outcrop of Oligo-Miocene granites is found in Zafarghand area in the southeast of Ardestan in Isfahan Province. Sarjoughian et al. (2018), Aminoroayaei Yamini et al. (2017), Sadeghian and Ghaffary (2011), Khalatbari Jafari et al. (2016), and Ghalamghash et al. (2019) suggested that this magmatism is a result of lower crust melting during mantle wedge metasomatism, occurred by Neo-Tethys subduction.This study aims to investigate the Oligo-Miocene granodiorites of East Bideshk, which is exposed in the central part of the Urumieh-Dokhtar magmatic arc in the northeast of Isfahan city. Despite the tectonomagmatic importance of this pluton in completing the geological history of Urumieh-Dokhtar magmatic arc, there are no comprehensive petrological studies performed on Bideshk granitoid. Thus, this study considered the mineralogy, geochemistry, tectonic environment, and origin of this granodiorite.

Microprobe analysis of the minerals was performed using a CAMECA SX 100 model with 15 kV accelerator voltage and 20 nA current at Stuttgart University, Germany. The Minpet software was also used to calculate the structural formula of the minerals and plot the diagrams. Intact and less altered rock samples are selected for geochemical analysis of major, trace, and rare earth elements by ICP-MS and ICP-OES methods in the geochemical laboratory of ALS Chemex in Ireland. The LOI values are also obtained by the gravimetric method. Fe2+ and Fe3+ are calculated based on the method by Middlemost (1989). Abbreviations for minerals are from Whitney and Evans (2010).

The Eocene Granodiorite - diorite rocks outcrop in the east of Bideshk area, in the northeast of Isfahan, and along the Urumieh-Dokhtar magmatic zone. According to lithological studies, they are mainly composed of granodiorite with predominant texture are granular, granophyre, and porphyroid.The major minerals are plagioclase, quartz, K-feldspar, hornblende, and biotite. Accessory minerals include magnetite, and apatite. Calcite and chlorite are the secondary minerals. Embayed plagioclases and quartz with rounded margins and plagioclases with oscillatory zoning, sieved texture, and dusty rims show non-equilibrium conditions during magma mixing. The composition of calcic amphiboles in these rocks is actinolite- tremolite, hornblende, and magnesio- hornblende. Plagioclases in the rocks of the east of Bideshk are andesine to labradorite in composition, and some show oscillatory zoning. Thermobarometry results indicate pressure, temperature, and crystallization depth decrease from the core (average ~ 3.01-3.63 kb, 685-732℃) of hornblende crystals. Geochemical investigations show that this granitoid is metaluminous, calc-alkaline, and I-type. The primitive mantle and the chondrite- normalized patterns of Bideshk whole-rock samples show enrichment of LREE against HREE. It is in accordance with magmatism in a subduction zone. Geochemical diagrams and variation in Rb content relative to Nb can also indicate a subduction-related magma source and mantle wedge metasomatism in the east of Bideshk, during Neo-Tethys subduction beneath central Iran.

Chahrisseh magmatic rocks are located in the northeast Isfahan, in the Sanandaj-Sirjan structural zone and parallel to the Qom-Zefre fault. These magmatic masses are located in a continuous section of Permian-Triassic sediments and rarely enter the Early Triassic beds. These rocks contain anhydrous ferromagnesium minerals (olivine, clinopyroxene and plagioclase), hydrous ferromagnesium minerals (amphibole and biotite) in addition to secondary minerals (chlorite, epidote and actinolite). Based on petrographic studies and geochemical analysis of minerals, these magmatic rocks are among the ultramafic lamprophyres with alkaline nature. Different methods of temperature-barometry of minerals show two completely different ranges of pressure and temperature (the first range of temperature 1000 to 1100 ° C and pressure 16 to 20 kbar and the second range of temperature 900 to 1000 ° C and pressure 6 to 13 kbar) which corresponds to the porphyric texture of the rocks. The chemical properties of primary minerals indicate the formation and placement of alkaline lamprophyres in the intercontinental environment. On the other hand, the presence of crustal xenoliths and xenocrysts provides evidence of the effect of crustal contamination. Therefore, it seems that in the short period of time from the end of the Paleozoic to the beginning of the Mesozoic, following the operation of the technical phase of Hercinian, alkaline lamprophyres form in a continental environment and digested parts of the continental crust during ascending to the earthchr('39')s surface.

In the southwest of Khuni mountain and the north of Kal-e-Kafi intrusion (northeast of Anarak), the igneous rocks of Khuni are cropped out. They dominantly show porphyritic texture and are similar to monzodiorite in composition. The phenocrysts mainly are clinopyroxene (diopside), amphibole (magnesiohastingsite to magnesian hastingsite), and feldspar (orthoclase in the rim and andesine in the core). Accessory minerals include primary biotite, apatite, sphene, and magnetite. The secondary minerals are biotite, calcite, epidote, tremolite- actinolite, and chlorite. Anti-rapakivi texture in feldspar is petrographic evidence of magma contamination. Application of various geothermobarometric methods for clinopyroxene and amphibole crystals in Khuni rocks yielded a crystallization temperature of ~1150°C for clinopyroxene and pressure range of 7-8 kb and temperatures of ~900-950°C for the amphibole phenocryst. Thermobarometry and chemistry of clinopyroxene and amphibole phenocrysts indicate that the rock-forming melt was formed by melting the continental crust in the Anarak area, as a result of the subduction-related magmatism of Eocene during the Neo-Tethys subduction beneath Central Iran.

Javinan skarn is located at 115 km north west of Isfahan (40 km south of Kashan and east of Ghohrud), is included in Central Iran structural zone and spread in contact with Ghohrud granitoid (Middle Miocene age) with shale, sandstone and limestone succession of the Jurassic age known as Shemshak Formation. Skarnification is made up of endo- and exoskarn subzones. Wide mineralization in these skarns hasn’t observed. Endoskarn subzone has limited occurence (from a few millimeters to a few centimeters) and exoskarn has the greatest development (from 1 meter to more than 10 meters). Endoskarn with the formation of the skarn minerals garnet, pyroxene, plagioclase, epidote and sphene, is formed in the intrusive host rock and is in the vicinity of the carbonate part. In its immediate neighborhood, exoskarn subzone starts with the formation of minerals garnet, pyroxene, idocrase, epidote, phlogopite, chlorite, quartz and calcite in the carbonate section. Mineralogical studies and textural relationship of minerals have shown that the metamorphic facies اhas reached to pyroxene hornfels in skarn rocks of this area.

The Nabar skarn is located about 35 km southwest of Kashan and within the Urumieh- Dokhtar magmatic belt and is formed along the contact between limestone of Qom formation with a probably middle to upper Miocene intermediate and basic intrusion body. The main minerals forming this skarn are garnet, clinopyroxene, epidote and accessory minerals are vesuvianite, chlorite, tremolite- actinolite, sphene, quartz and calcite. Ore minerals are pyrrhotite, pyrite with smaller amounts of chalcopyrite, sphalerite and magnetite. According to the presence of magnesium minerals like diopside and calcium minerals such as garnet, vasuvianite and epidote the type of host rock is probably calcite-dolomite. Skarn formation and mineralization in this region was occurred during three development stages. Presence of high temperature anhydrous minerals such as grossular and diopside specifies the formation of the first Stage in these rocks. Stage 2 is associated with the formation of andradite and sphene. Stage 3 is specified by replacement of anhydrous minerals at temperatures below 470 ° C by hydrous minerals such as tremolite-actinolite, epidote, chlorite and vesuvianite.

On the base of petrology, the Mirabad- Chehel Khane granitoid, east of Bouin-Miandasht, dominantly consists of syenogranite, monzogranite, alkali granite and granodiorites. The main minerals of these rocks are quartz, alkali feldspar (Orthoclase), plagioclase (Albite - Oligoclase), biotite, ± amphibole with minor amount of allanite, zircon, titanite, apatite, ± tourmaline. The biotite from the granites are Fe-rich type (annite) and primary magmatic in origin. The composition of the biotites studied principally falls in the calc-alkaline subduction related I-type granite on the tectonomagmatic discrimination diagrams, which stand on their major element oxides. Which is consistent with the nature of their host rocks. The studied amphiboles are classified as calcic (ferro-hornblende) which points to the I-type nature of the granitoid. The tourmaline composition plots on the schorl - foitite field. The temperature for the alteration, on the base of chlorite composition from the syenogranite, is estimated around 350°C and from the monzogranite rocks about 341°C. Based on the application of Al-in amphibole, a 3 Kbar pressure was determined for the syenogranite unit corresponding to the depth of 8-11 Km for the emplacement of the pluton. Hornblende- plagioclase thermometer shows 694 to 700°C for the equilibrium of these two minerals.

The study area is located in the northern part of the Sanandaj-Sirjan structural zone, between Daran and Aligudarz towns, near Darreh Sary village. Based on field and petrographical evidences, exposed metaplitic metamorphic rocks in this region, consist of five categories: phyllites, slates, muscovite biotite schists, garnet schists and staurolite schists. Mineral chemistry compositions of the metaplites are from garnets that are rich in almandine, plagioclases are mostly rich of albite, black micas are annite and siderophyllite, white micas are almost in the end member of muscovite and chlorites are ripidolite. Reactions that took place in these rocks, have caused the reduction of chlorite and muscovite and have led to the formation of some minerals such as biotite, garnet and staurolite in metamorphism progress. The chemical composition of the minerals such as garnet shows progressive metamorphism with homogenization of these minerals. Presence of secondary chlorites in these rocks exhibit uplift and retrograde metamorphism up to greenschist facies. Thermodynamic study of the mineral chemistry of mineral such as garnet, biotite, muscovite and chlorite suggests thermic peak of 630°C and pressure peak of 6.5 kbar. Thermobarometric data reveal barovian metamorphism type or orogenic trend with the passing of greenschist to middle amphibolite facies.

The studied area is located in the east of Nabar village and southwest of Kashan¡ a part of the Urumieh – Dokhtar magmatic arc. The volcanic rocks belonging to Eocene age¡ are composed of pyroxene andesites¡ andesites¡ dacites and rhyolites. Porphyritic¡ glomeroporphyric¡ microlitic¡ and sieved textures are the most common textures of these rocks. Plagioclase¡ clinopyroxene and amphibole are the predominant minerals in the pyroxene andesites and andesites¡ whereas dacites and rhyolites are characterized by the presence of plagioclase¡ amphibole¡ quartz¡ biotite¡ and K-feldspar. Inequilibrium textures including embayed plagioclases and quartz with rounded margins¡ and oscillatory zoning in the plagioclases¡ sieved texture¡ and dusty rims are evidences of magma mixing. The enrichment in LREE and LILE and the HREE and HFSE depletion in the chondrite and primitive mantle normalized diagrams point to calc-alkaline nature of the rocks studied and they are related to volcanic arcs setting. High ratio of La/Nb (2-4.36) and negative Ti and Nb anomalies in spider diagrams can support crustal contamination hypotheses of these rocks. Also¡ low ratio of Nb/La (0.23-0.5) and high ratio of Sr/Ce (8.4-19) indicate contamination of parental magma with crustal materials. The rocks studied are formed from magma which is derived from enriched-mantle with 1-5 percent partial melting of spinel-lehrzolite.

The area studied is located north of Azna (Lorestan Province) in a small portion of the Sanandaj – Sirjan structural zone (Mohajjel et al., 2003).This area is part of the Zagros orogenic belt, formed by the opening and closure of Neotethyan ocean. From NE to SW, it consists of three parallel tectonic regions: the Orumieh-Dokhtar magmatic belt, the Sanandaj-Sirjan structural zone and the Zagros thrust-fold belt (Ghasemi and Talbot, 2005).
The Sanandaj-Sirjan structural zone is a metamorphic belt composed mostly of greenschist, amphibolite and eclogite facies rocks. The development of the zonetook placeduring the opening of the Tethys ocean and its subsequent closing during the Cretaceous and earlyTertiary convergence of the Afro-Arabian and Eurasian plates (Mohajjel and Fergusson, 2000). The second stage of metamorphism and deformation of the zone, designated D2, is the most important, resulting from the opening and closure of the Neotethyan ocean and the collision of the Arabian plate with the southwestern part of central Iran in the Late Cretaceous to Tertiary (Laramideorogenic phase) (Ghasemi and Talbot, 2005; Aghanabati, 2004; Mohajjel et al., 2003; Mohajjel and Fergusson, 2000; Alavi, 1994). In the Sanandaj-Sirjanzone, which includes the Azna area, Cretaceous granitic intrusions into the schists were followed byfolding and faulting. The intrusions produced contact metamorphism, and have lens-shaped outlines, trendingNW-SE. Consequently, the Azna area has a varied petrologic assemblage with polyphase metamorphism and deformation, including schists, metabasites and mylonitic granites. The phases include: 1. Deformation D1, and dynamothermal metamorphism (M1),a result of the subduction of Neotethysoceanic crust beneath the Iranian plate in the Late Jurassic. 2.Deformation D2, and thermal metamorphism (M2),a result of Paleocene continental collision and 3. Deformation D3, and dynamic metamorphism (M3). This deformation is a progressive deformation that hasproduced the current morphologyof the Sanandaj-Sirjan zone (Shabanian Borujeni, 2008).
In this paper we focused on petrography and mineral chemistry and thermodynamic conditions of the metapelites.
The chemical compositions of minerals were determined by a CAMECA SX100 electron microprobe (EMP) at Universität Stuttgart (Germany). The instrument is equipped with five wavelength dispersive spectrometers. The beam current and acceleration voltage were 15 nA and 15 kV, respectively.
Discussion and The Azna regional metamorphic rocks include quartz-feldspar schists, mica schists, andalusite-bearing schists and quartzites.
The Azna metapelites are schists, containing quartz, feldspars, andalusite, muscovite, biotite, muscovite, chlorite and garnet, in variable proportions, characterized byporphyroblastic and lepidoblastic textures. Based on mineralogy, minerals of these rocks contain andalusite, garnet, feldspar, muscovite, biotite, quartz and chlorite. Microprobe analyses show that the mineral compositions are as follows: White micas in the andalusite-bearing schists are muscovite, plagioclases are albite-oligoclase, garnets are almandine-spessartine with weak chemical zoning and biotites are siderophylite-annite.
Based on geothermobarometry, these rocks formed in the hornblende-hornfels facies and the low pressure part of the amphibolite facies,with temperatures about 562-692 °C and pressures1.07-4.12 kbar. After the regional metamorphism of these rocks,granitoidintrusions causedthermal metamorphism of these rocks and the formation of andalusite-bearing schists.

Studied metabasites of The Zayandehrood River and Dam margin are located at about 100 km West of Isfahan town. These metabasites are part of the Sanandaj-Sirjan Structural zone including eclogites, amphibolites and green schists. Studies suggest that the eclogites were formed at high-pressure condition in eclogite facies and were finally changed to eclogitic amphibolites under the retrogressive metamorphism. Geochemical characteristics of immobile trace elements that are less affected by alteration and High-Pressure deformation suggest that the origin of these metabasites are mid oceanic ridge basalts (MORB). In fact, these eclogites are the same Neo-Tethys MORBs that caused by the subduction of the oceanic crust to beneath of the Iranian microcontinent were formed during a high to medium temperature, progressive dynamo-thermal regional metamorphism and then returned to the surface were transformed to the eclogitic amphibolites caused by retrogressive metamorphism. Along with final collision between Neo-Tethyan oceanic crust and the Iranian microcontinent at Late Cretaceous, an intense metamorphism phase occurred in the region and deeper high pressure metamorphic rocks were uplifted to the Surface.

The Khuni skarn has been developed in the contact between small tongues of the Late Eocene-Oligocene I-type Kal-e kafi granitoidic intrusive body and the Precambrian Lakh marble-dolomite unit، Located 220 km northeast of Esfahan in the Central Iran structural zone. Skarnification could be divided into two subzones: endoskarn and exoskarn. There is no significant mineralization in relation to this skarn system. The extent of the endoskarn subzone is very limited (often from 2 mm to 2 cm)، but the exoskarn has the most extension across the contact. The endoskarn subzone can be recognized by formation of euhedral garnets adjacent to the carbonate part. In the immediate vicinity of the endoskarn، the exoskarn subzone initiates with formation of garnet and clinopyroxene in the carbonates and is extended far away from the contact as represented by vesuvianite and phlogopite minerals. Garnet is one of the most abundant minerals in this skarn system and is found in different sizes and forms. In this paper، the zonation pattern of garnet crystals in the exoskarn subzone in the immediate vicinity of intrusive body is investigated. These garnets are mainly euhedral and isotropic and in some cases anhedral and anisotropic. They are commonly cored by a grossular-rich inner part، and a sharp considerable increase in their andradite content is found toward the rim in most cases. Most studies on skarn systems consider boiling to be the most important cause for this phenomenon. This means that boiling increases the Fe content and oxygen fugacity in the final stages of the system evolution، which consequently increases the andradite content of garnet in its solid solution

The Bultaq shear zone is located 185 km north-west of Isfahan. The study area is a part of the Sanandaj–Sirjan zone, which is affected by ductile and brittle–ductile deformation and consists of slate, schist(garnet-muscovite schist, enriched quartz-muscovite schist and biotite-muscovite schist), amphibolite marble, metavolcanic, andesite and tuff. There are several duplex structures and thrusts with NW-SE-trend and NE dip in the Bultaq shear zone. This shear zone is parallel to the Zagros Organic thrust. Also, boudinage structures geometric analysis, mesoscopic scale asymmetric folds, microscopic studies of S-C, S-Ć cleavages and σ- type porphyroclast confirmed right-lateral strike-slip movement. These fabrics show right rounded cuts in region in some parts. Mylonitic foliations were used to calculate elongation (e) and stretch (s) in this area. The microstructures were formed under green schist to amphibolite facies conditions. The metamorphic rocks have been formed in a Barrovian metamorphism type (medium temperature - pressure) and affected by three metamorphic and deformation phases. The metamorphic phases include dynamothermal, dynamic and retrograde and the deformation phases are D1, D2 and D3.

Garnet-micaschists from Haji Qara high, north of Golpayegan, are part of the metamorphic rocks of the Sanandaj-Sirjan Zone (SSZ). Lepidoporphyroblastic and porphyropoikiloblastic are the main textures and the mineral assemblages consist dominantly of Fe-biotite, muscovite and ferriphengite, metamorphic Fe-Mg chlorites (I-type and IIb), garnet and quartz. Staurolite, andalusite, plagioclase carbon, Fe-oxides and tourmaline are present as accessories. Petrographic evidences as well as mica chemistry along with other paragenesis and thermometric estimations indicate a path change from amphibolites facies to lower pressure and higher temperature gradient suggesting the presence of a local pluton which led to garnet porphyroblast, biotite and muscovite (overprinted in different orientation) and andalusite crystallization. The occurrence of chlorite, ferriphengite and Fe-oxides demonstrate a retrograde metamorphism during uplift and decompressional cooling path in the area.

The east Nabar volcanic rocks with Eocene age are located in the southwest of Kashan and Uromieh-Dokhtar magmatic belt. These rocks are composed of basaltic andesite، andesite، dacite and rhyolite. Plagioclase، amphibole، clinopyroxene، biotite and quartz are the essential minerals of these rocks. Very few apatites are observed in some plagioclases. Epidote، calcite، chlorite، sphene and opaque are secondary minerals. Porphyritic، glomeroporphyric، microlitic and poikilitic textures are common textures in these rocks. On the base of microprobe analyses the composition of plagioclase ranges from oligoclase to labradorite، the clinopyroxenes are diopside and the amphiboles are magnesio-hornblende and tremolite. The chemistry of clinopyroxenes show that these rocks belong to sub-alkaline series and volcanic arcs. On the base of barometry of clinopyroxenes، the study rocks formed in medium to low pressure during their ascending. The volume of water in the crystallization environment of clinopyroxenes was high and the rocks studied formed in high oxygen fugacity. The thermometry of clinopyroxenes reveals the temperature of 975 oC for their crystallization. The amphiboles thermobarometry shows the pressure of 2. 97 kbar and the temperature of 700-750 oC.

The Nabar plutonic rocks is located in the northwest of Isfahan and in the Urumieh-Dokhtar magmatic belt. Based on the petrologic studies, the Nabar complex is composed of gabbro, gabbro-diorite, diorite, quartz diorite, tonalite and quartz monzonite. Mineral chemistry shows that pyroxenes are Na-poor in composition and are classified as clinopyroxenes and orthopyroxenes which are diopside and hypersthene. The composition of these minerals can be correlated to pyroxenes of calc-alkaline series. The composition of amphiboles plot in two groups of Fe-Mg-Mn amphiboles and calcic amphiboles. The plagioclase compositions are variable from oligoclase to bytownite in the analysed samples. Using Al barometry in hornblend, pressures of about 2 Kbar are estimated for the intrusive body.

The Ghohroud intrusion is a part of the Orumieh-Dokhtar magmatic belt. This pluton with probably Oligo-Miocene age، occurred due to intensive volcanic activity during the Alpine orogenic which is composed of granodiorite to tonalite rocks. The pluton is mainly composed of felsic minerals، such as quartz، plagioclase and alkali feldspar. Ferromagnesian minerals are biotite، amphibole and clinopyroxene. Dioritic enclaves are common in the pluton which vary extensively in diameters. Mineral chemistry of the pyroxenes from the diorite enclaves indicate augite - diopside composition that locally have undergone oralitic alteration. Chemical composition of the clinopyroxenes confirmed a subduction geological setting، the pressure of 6-15 kbars and the temperature of 1250-1300 °C as well as the presence of high percent water content in the magma. High oxygen fugacity and water content increment during magmatic evolution could represent that the clinopyroxenes were crystallized during magma ascent and within different pressures.

The Ghaidou monzogranite in the southeast of Khomein constitute a part of rock complex from the northern part of the Sanandaj-Sirjan zone. This body intruded into the Jurassic micaschists and created a metamorphic aureole. Also، aplitic veins، tourmaline bearing pegmatitic dikes، felsic microgranular enclaves and surmicaeous enclaves are observed in this area. The predominant minerals of these rocks are K-feldspar (orthoclase and microcline)، Na-plagioclase (Albite- oligoclase in the monzogranite and oligoclase in the felsic microgranular enclaves)، quartz and black mica (Annite) -as the main minerals- with minor amount of tourmaline (schorle)، garnet، white mica (phengite)، sillimanite، kyanite، zircon، apatite and ilmenite. On the basis of biotites mineral chemistry، these phases are enriched in FeO and Al2O3 and relatively low in TiO2. These minerals are magmatic and primary and thermometry results yielded 660-690 ºC. According to the chemical composition of primary igneous biotites in the enclaves and monzogranites، these rocks have calc-alkaline، peraluminous and an orogenic continental collision affinity characteristics of S-type granites. Also، the biotite composition and the presence of ilmenite point to low oxygen fugacity and redox conditions during magma crystallization. Based on the available data، the generation of these rocks can be related to Arabian-Eurasia collision zone.

The studied volcanic rocks، in the middle part of the Central Iranian volcanic belt (Urumieh-Dokhtar magmatic arc) belong to a vast magmatic province located in the north of the Bitlis-Zagros suture zone. Petrographically، these rocks show dacite to andesite composition and include phenocrysts of plagioclase، amphibole and biotite with a prevailing porphyritic texture in a matrix composing of feldspar، quartz، microlite and glass. Having a relatively invariable composition، plagioclases are all andesine. Amphiboles are calcic and tschermakite type. Estimation of temperature and pressure of crystallization resulted from graphically integrating amphibole and amphibole-plagioclase geothermo-barometry equations indicates that the amphibole-plagioclase phenocrysts were crystallized in the temperature range of 763-823 °C with average of 797 °C and in the pressure range of 2. 2-4. 5 kbar with the average of 3. 4 kbar. The maximum depth of crystallization is evaluated at 17 km in continental crust.

The skarns of the Ochestan area are located in the Sanandaj- Sirjan zone، about 60 Km south of Mahallat. The rock complex in this area consist of intrusive bodies and metamorphic rock such as: schist، phyllite، slate، hornfels، amphibolite and metavolcanic. The injection of magma in the Cretaceous-Paleocene with syenogranite and monzogranite composition into the Paleozoic limestone and dolomite led to formation of skarn and marble. Clinopyroxene (diopside)، olivine (forsterite)، tremolite، talc، serpentine، phlogopite، margarite، wollastonite، opaque minerals، calcite and quartz are observed minerals in contact metamorphism rocks. According to the mineralogical studies، the Ochestan skarns are exoskarn-type and the presence of minerals such as: forsterite، diopside، tremolite، antigorite and phlogopite show that the host rock is dolomitic the in study area. These skarns show zoning of intrusive body into the host rock: wollastonite skarn، pyroxene skarn، forsterite- serpentine marbles، mica marbles، tremolite- talc marbles، calcite and dolomite marbles.

The Eocene volcanic rocks in the SW Jandaq that outcrop in the south of Doruneh fault constitute a part of the Central Iran zone. The predominant rocks consist of basalt andesite، trachyandesite and dacite that porphyritic، microlitic porphyritic and hyaloporphyritic textures are common. The essential minerals are represented by intermediate plagioclase، diopside، augite، phlogopite and magnesiohastingsite and the secondary minerals are Fe -oxide and chlorite. Based on geochemical data، these rocks belong to high-K calc-alkaline and shoshonitic series which with K2O، Ta/Yb، Th/Yb and Ce/Yb. Lava eruption in subduction setting can be demonstrated by highly negative Nb and Ti anomalies، and also by comparison with mantle normalized trace element trend with that of the volcanic arc. In addition، the discrimination diagrams (TiO2/Al2O3 and Zr/Y) display a continental volcanic arc setting for these rocks. The REE patterns (chondorite normalized) and their ratios plus positive Pb anomaly، point to the effective role of low grade partial melting of a metasomatized mantle and garnet amphibolites source accompanied by crustal contamination in the course of formation these rocks.

In the south west of Jandaq area, the Eocene volcanic rocks crop out, near the Doruneh Fault in a large area. These rocks are composed predominantly of basalt, quartz andesite, andesite, dacite and latitewith porphyritic, microliticporphyritic and hyaloporphyric textures. The main constituents are plagioclase, amphibole, clinopyroxene, quartz, minor alkali feldspar and biotite and opaque minerals as accessory minerals. The secondary minerals are opaque, sericite, calcite and chlorite. The composition of the plagioclase ranges from andesine to labradorite, the clinopyroxene is diopside-augite and the amphiboles are magnesio-hastingsite some plagioclase phenocrysts show oscillatory zoning. The study of chemical composition of clinopyroxenes classifies these rocks as sub-alkaline series and volcanic arc. The geothermometry of clinopyroxene reveal the temperature of 941-959 ºC for pressure of 1-10 kbars. Clinopyroxenes barometry point to their formation in defferent depths during their ascending. The Hlb-Plg thermometry shows the temperature of 858-941 ºC for pressure of 1-10 kbars. The high volume of water in the crystalization environment of the pyroxenes as well as variations on AlIV+Na/ AlIV+2Ti+Cr diagram indicate the high oxygen fugacity of the environment. Field observations and some petrographic evidences demonstrate traces of hydrothermal alteration.

The Ochestan granitoids are located 60 Km South of Mahallat in Markazi province and in Sanandaj-Sirjan zone. Based on petrographic studies, these rocks are alkali feldspar-granite, granite (syenogranite and monzogranite) and granodiorite. Alkali feldspar (orthoclase and microcline), plagioclase (albite and oligoclase), quartz and muscovite are present as the major minerals and tourmaline, biotite, zircon, garnet, apatite, opaque minerals, rutile and chlorite as the secondary ones. Foliation is found in many parts of the pluton indicating mylonitization process. Geochemical studies show sub-alkaline (calc-alkaline), peraluminous and S-Type for the granitoid studied. According to spider diagrams, upper crust is considered as the magma source, and syncollision as the geotectonic setting. Partial melting of metapelites can be assumed as a source of magma generation in regard to the type of granitoids, geochemical data and metamorphic rocks exposing in this area.

The Kalut area is located at about 70 km northeast of Ardakan (Yazd), which is a part of the structural zone of Central Iran (Yazd block). The igneous rocks of the area belong to Tertiary and are subdivided into intermediate (microdiorite) and basic rocks (basalt and microgabbro). The majority of these rocks show intergranular textures. Plagioclase (albite to bytownite), clinopyroxene (diopside) and olivine are the main minerals of basic rocks. Mica (biotite), apatite and Fe-Ti oxides are accessory minerals. Albite, calcite, chlorite, epidote, amphibole, opaque, sphene, prehnite formed during alteration process. The main textures of intermediate rocks are intergranular. Plagioclase (oligoclase to labradorite), amphibole and clinopyroxene (diopside) are the significant minerals of the aforementioned rocks. The chemistry of clinopyroxenes and the existence of pillows in exotic magmas of mafic rocks, imply that during formation of magma it was mixed with another basic magma, which the nature and the sources of these magmas were likely similar. The results of petrogenetic studies by using mineral-chemistry of clinopyroxene indicate that the composition of magma is tholeiitic to calc-alkali basalts which is related to volcanic arc zone.