oeeuring in the Sangan arca was
fonned within two different rock groups· graitoids and
skarns. Based on the new amphibole classification and
nomenclature, the general fonnula of amphibols IS
(AB2C,T,O"OH),. Amphibole of granitoids is a
ferroedenite in which Si = 6.87 - 7.75, CaR> 1.5,
(Na+K)A > 0.5 and Ti < 0.5. Skarn amphiboles are
mostly developed within amphibole skarns and
gamet-pyroxene skarns during retrograde stage of
skarn evolution. High-temperature amphiboles are
rich in Al while low-temperature amphiboles are poor
in AI. Skarn amphiboles are classified in two groups:
(a) hastingsite in which Si = 5.99 - 6.08, CaB> 1.5,
(Na+K)A > 0.5, Ca < 0.5 and Al < Fe+] (b)
ferroactinolite in which Si = 7.61 - 7.90, CaB>1.5,
(Na+K)A < 0.5 and CaA < 0.5. Amphibole in (a) is
AI-rich while amphibole in (b) is AI-poor.

In this work we have prepared nano-sized Bi-YIG powders, using mechanochemical processing. In this process, a part of the activation energy, which is necessary for chemical reactions, is provided by high-energy mills. The as milled powders obtained by this technique need a lower annealing temperature in comparison with those obtained by conventional ceramic technique to become a single phase garnet. The lower temperature itself can produce ultrafine powders by inhibiting grain growth. The optimum calcining temperature was 800 ^oC for 5 hours milling time, which is much lower than 1000^oC needed in conventional ceramic technique. Longer milling times are not recommended, because it produces extra iron into the powders. The average particle size of the powders was in the range 50 to 60 nm, using Scherrer’s formula. Room temperature saturation magnetizations of the samples were measured using a vibrating sample magnetometer (VSM). These were 0.022, 6, 17 and 20 emu/g for the samples annealed at 700, 725, 750 and 800 ^oC, respectively. The lower magnetization values respect to the conventional ceramic technique, are discussed according to core-shell model.

Next to the Ghohroud granitic intrusive body in the south of Kashan, skarns are outcropped, of which some contain garnet crystals with obvious zoning. In order to investigate characteristics of this zonation, garnet crystals were analyzed from core to rim by EDX point analysis, using scanning electron microscope. Obtained data show that garnet crystals belong to grandite (grassolar-andradite) series and oscillatory and complex zoning are widespread. Variation of Al and Fe from center to rim of analyzed crystal indicates sharp variation in X_Gras in grandite solid solution series. Therefore, garnet zoning formed during crystal growth and diffusion has an insignificant effect. However, based on the BSE images, oscillatory zoning has been disturbed by fluid infiltration next to fractures. Pattern of variation on XGras from core to rim indicates that the main factor on formation of oscillatory zonings was immiscibility in grandite series which followed by changes in hydrothermal solution composition. Sharp micron-scale boundaries in zonation and preservation of zoned garnet reveal that skarns have not experienced thermal overprint after formation and emplacement of pluton and formation of skarns were not followed by further thermal geological event like regional metamorphism in the area.

The metabasite rocks from north of Shahrekord, which is a part of structural zone of Sanandaj-Sirjan, are undergone medium temperature – high pressure metamorphism (eclogite facies). These rocks then were subjected to a retrograde metamorphism (amphibolite facies). A distinct compositional zoning is preserved in fresh garnets which are formed during eclogite facies. The compositional or growth zoning in these eclogite rocks shows clockwise P-T-t path.  In the beginning of metamorphism, P and T increased up to reach to the peak of high pressure metamorphism, then P decreased while the T was increasing during uplift and decompression. These growth stages indicate that P_max was not contemporaneous with T_max during eclogite facies metamorphism of the metabasites from North of Shahrekord, in Sanandaj - Sirjan Zone

The conglomerates of Sangestan Formation (Lower Cretaceous)
have been metamorphosed in the vicinity of the leucogranitoid rocks of the
Shir-Kuh batholith and have created the mineral assemblage of garnetepidote-
quartz-calcite-pyrite in the contact halo. Following the contact
metamorphism, hydrothermal alteration (pyrite formation and silicification)
has likely occurred. Based on the trace element contents of the garnets , the
skarn in the contact halo is Cu-Pb-Zn bearing calcic skarn type. The above
mentioned minerals, apparently, indicate that there is a genetic relationship
between intrusion related Cu-mineralization and the skarnification in the
study area.

Metamorphic rocks of the Hamadan region have experienced
regional and also contact metamorphism (due to intrusion of gabbro, diorite
and granitic bodies), therefore, their mineral assemblages have formed in
multiple stages. Evidence of regional metamorphism (M) and contact
metamorphisms at the contact of gabbros (M’1) and porphyroid granites
(M’2) are separatable, hower At the contact of hololeucocratic granites a very
local contact metamorphism (M’3) have occurred (from a few decimeter up
to a few meters, due to small size of these bodies). Minerals such as micas,
garnet, staurolite, cordierite, andalusite, kyanite and sillimanite are usually
produced by several reactions, and participated in other reactions to form
other minerals. The relationship between mineral growth to deformational
events have been found at several stages (i.e. pre-tectonic, syn-tectonic and
post-tectonic minerals are common in metamorphic rocks of the region.)
Pegmatites and silicic veins have played essential role in some metamorphic
reactions as sources for heat and fluids, so that some metamorphic minerals
are common near these veins and disappear far from the veins. Considering
observed mineral assemblages in metamorphic rocks of the region, regional
metamorphism can be correlated with low to moderate P/high T Buchan type
metamorphism. In final stages of metamorphism, high T minerals such as
cordierite experienced retrograde reactions or pseudomorphed and higher
pressure minerals such as kyanite have been more stable.

The injection of I-type granitoid bodies (Hosh intrusion) with calc-alkaline affinity into Lower Cretaceous limestones (Taft Formation) has produced the various types of related skarns and marbles. Thereby, those skarns formed can be undoubtedly divided into four groups, clinopyroxene-plagioclase skarns, clinopyroxene skarns, clinopyroxene- vesuvianite skarns and moreover garnet skarns. Additionally, calc-silicate bearing marbles also show an especial mineral assemblage consisting of olivine, clinopyrocxene, garnet and vesuvianite. Based upon geochemical studies, two types of garnet can be distinguished in these skarns. The first, Type is the garnets with grossular composition in which they are found with calc-silicate assemblages in skarns and the second, Type is the garnets with andradite composition present in garnet skarns. Clinopyroxenes in those skarns feature a composition varying between Ca-rich diopsides, salite and fassaite. Based on the chemical composition of the intrusive body and the related skarns, one can conclude the close relationship of these skarns with Cu and Zn skarns.

The ophiolitic complex of eastern Birjand consists of various rocks of a complete ophiolitic complex. Except for basaltic pillow lavas which are changed to metabasites such as eclogites and blueschists under metamorphic conditions, all other rock types of an ophiolitic complex could be seen in this sequence. Chemistry of garnets and their zoning patterns indicates the occurrence of subduction in the study area. The presence of the low-temperature and medium-temperature eclogites in the study area also may show the collision process between Lut and Afghan Blocks which has occurred after the subduction process. This collision process has lead to the occurrence of medium-temperature eclogites in response to the increase of temperature in the study area and then uplifting of the eclogitic rocks during the emplacement of area ophiolite in the suture zone between Lut and Afghan Blocks.

The determination of mineral quantities is one of the primary purposes of petrology and economic geology studies. When producing skarn zonation, it is necessary for the quantities of minerals in each zone to be known. Currently, various methods of determination for mineral quantities in rock bodies have been developed, but a rapid, accurate and economic method for distinguishing 3D mineral distribution has not yet been understood. This study introduces such a method for distinguishing 3D mineral distribution based on image sequence modelling of rocks. In the studied area, -Hassan-Abaad of Taft, central Iran-  garnet is one of the most important and most frequent minerals found in skarns and is present in a variety of types and places. For our study, we sampled a very thin layer of rock (300 microns) and prepared a digital photo at every stage of our analysis. Prepared images were analyzed using MATLAB software. Each value of the image with its x, y and z coordinates was stored in a new matrix. Matrices were modelled in RockWorks and filtered based on the mean standard deviation of the modelled data, producing garnet networks. The studied zone had 31.4% garnet, allowing to be considered a garnet- wollastonite zone. This method is also useful for different calculations, such as: determining rock type, field zonation, calculation of the amount of mine and waste material, fluid inclusion studies and distinguishing type and volume of rock porosity.

The Kaleybar intrusion with an area of 750 km² is located in the north east Azerbaijan, NW Iran. Based on structural subdivisions of Iran, it  is located in the West Alborz-Azerbaijan Zone wich is intruded into the Azerbaijan continental crust during Eocene to Oligocene following the Pyrenean Orogeny. It consists of various rock types including nepheline syenite, syenite, nepheline diorite together with minor diorite and microgranite. The rock forming minerals of the investigated nepheline syenites are plagioclase, orthoclase, nepheline, biotite and amphibole. Clinopyroxene, plagioclase, amphibole and nepheline are dominant minerals in nepheline diorite. Titanian garnet is uncommon accessory phase of the both rock types. Chemically, garnet from the nepheline syenite has TiO₂ contents ranging from 1 wt% to 5.0 wt%. Its composition is consistent with Ti-Adr_{67 to 78 mole %}Grs _{21 to 33 mole %}. Ti-garnet from the nepheline syenite is euhedral to subhedral with reddish to deep brown colours which is different from light brown anhedral and fine grain garnet from the nepheline diorite. Magmatic origin of the Ti-garnet from nepheline syenite is suggested on the basis of petrographic studies, mineralogical criteria and chemical properties whereas the secondary garnet in the nepheline diorite seems to originate from metasomatic source.

The Kaleybar alkaline igneous intrusion contains fine- to coarse-grained, anhedral to euhedral brown garnets. Most of the garnets are zoned. Generally, they occur in foid-bearing leucocratic rocks and the phenocrysts typically have analcime inclusions. According to mineral chemistry, the garnets of Kaleybar are Ti-andradites and melanites. The chemical zoning is characterized by a decrease in mole percent grossular, almandine, and spessartine and an increase in andradite from core to rim. On the basis of the present data, it can be concluded that the garnets in the Kaleybar intrusion are in the primary igneous phase that formed during the late magmatic stage and Ti-Si exchange in the tetrahedral site is the main substitution.

The Zaroo Cu-skarn is located NW of Yazd province, within the Cenozoic magmatic belt of Central Iran. The widespread rocks in the region are Eocene age volcanic with granitoids intrusives. The Cretaceous limestones in western parts of West Zaroo are hosted by skarn – marble mineralization. The skarns are distal type and are characterized by assemblage: Clinopyroxene, garnet, ilvaite, vezovianite, termolite, epidote, chalcopyrite, magnetite, calcite and quartz. The paragenetic relationships of these minerals have revealed a polygenetic nature of skarn assemblage reveal a polygenetic nature. Black crystals and masses of ilvaite have a close association with hedenbergite clinopyroxene and andradite garnet zone, likely as replacement bodieds. The formation of ilvaite is related to following reactions:

Andradite + Fe (OH)₂ + CO₂ = ilvaite + magnetite + quartz + calcite + H₂

Hedenbergite + magnetite + Fe (OH)₂ = ilvaite

The early skarn minerals are formed at 550 ºC and the decomposition of early minerals to formation of final hydrous assemblages started below 470 ºC in fO₂.

The study area is a part of the Sanandaj- Sirjan metamorphic belt. The Hamadan metamorphic rocks can be divided into three groups including regional metamorphic rocks, contact metamorphic rocks and migmatites. Garnet crystals are usually common in all of the metamorphic rocks (except for slates and phyllites) and in the igneous rocks (i.e. aplite, pegmatite and monzogranite). These garnets, from point of morphological view, can be divided into three groups: special rhombic dodecahedron form, special trapezohedron form and composite forms that made up of particular dodecahedron form, mature composite forms and particular trapezohedron form. Particular dodecahedron forms are common in these rocks: garnet amphibole schists, seldom in garnet mica schists, rarely in mesosome of migmatites and in garnet mica hornfelses. Garnets in aplites and pegmatites have special trapezohedron form. Garnet crystals in other rocks of the study area have composite forms. The important factor, which is effective in changing these crystal forms, is chemical composition. With increasing of Mn/Ca and (Mn+Mg)/Ca ratio, garnet crystal forms change from dodecahedron to trapezohedron.

The studied volcanic rocks are located in south of Sarab at the northern part of the Bozghoush mountaion. The rocks are megaporphyry andesite flows and trachy andesite basalt lavas associated with tuff. In the northern part of the study area these rocks are covered with younger sediments of Quarternary age. These rocks are containing phenocrysts of analcime, olivine, pyroxene and plagioclase. The major textures of these rocks are porphyry with intersertal matrix.  According to whole rock analysis of the study area, rocks they are trachy andesite and tephro-phenolite. Also these rocks are high potassic to shoshonitic nature with peralluminous character. Based on textural evidence analcime seems to be primary and formed directly from magma. The rocks of north Bozghoush shows a pronounced enrichment in LILE (Rb, Ba, Tb, U, k). Enrichment of incompatible elements of k and Rb and negative anomaly of Ti and Nb in these rocks are comparable with melts of lower crust. The spider diagrams and REE patterns show that the rocks of the study area are formed from the same source. Enrichment of incompatible elements can be related to mantle metasomatism or contamination of continental crust. In this regards negative anomaly of Ta, Nb and Tb (T N T) and also with respect of eventual Neo-Thetys subduction in this area and most probably enrichment of incompatible elements indicates effects of subduction on mantle sources.  According to REE investigation  most probably the main source of  these rocks were  phologopite-bearing garnet lherzolite ,  with partial melting rate of 4-6 percent, at  a pressure of 30-35 Kb  and the depth of 90-100 Km.  

There are scattered exposures of young volcanic rocks in Hamun Lake Area in south western and north western of Zabol in east of Iran. The microscopic evidences and geochemical analysis show that these rocks are olivine basalt and basalt to trachy basalt. The main textures of these rocks are porphyry, microlitic porphyry and vesicular. The main phenocrysts of these rocks are olivine, clinopyroxene (Diopside) and some plagioclase (Labradorite). Tectonomagmatic studies indicate that these rocks are formed in intracontinental environment in Helmand block and have sodic alkaline nature. These rocks can be the production of extension which has occurred after compressional regime in east of Iran. Enrichment of LREE to HREE ratio indicates that the parent magma has probably formed by low partial melting of garnet lherzolitic mantle.

Hornblende biotite bearing tonalite from the west of Dehnow comprises of quartz, calcic plagioclase (andesine-labradorite), garnet (mostly almandine), biotite (annite to siderophyllite), calcic amphibole (mainly ferrohornblende) and accessory minerals of chlorite, epidote, calcite and ilmenite. According to thermobarometry of amphibole, plagioclase as well as the chemistry of garnet that shows CaO content of about 4.91-5.48 wt% and MnO content of about 1.89-2.40 wt%, the garnet in tonalite has crystallized in the temperature and pressure range of 696 to 950°C and 6.4 to 12 kbar, respectively, and which is in a greater depth than that of amphibole and plagioclase.

The S-type granitoid batholith of Shir-Kuh, which is part of central Iran Zone, is located in SW of Yazd and consists of three main granodioritic, monzogranitic and leucogranitic units. The systematic changes in the composition of plagioclase reveal that the granodiorite have been a calcic core plagioclase-rich magma, the monzogranites is a differentiated melt, and the leucogranite is a late residual melt. Totally, all biotites have high Al^VI (3.2 to 6.2 apfu) which is characteristic of peraluminous granites. The high almandine component of garnet is similar to those in other peraluminous plutons and, in particular, to the magmatic garnets. Muscovite appears as both primary and secondary-looking grains. Monazite occurs as two types of chemically crystals: monazite and brabantite [CaTh (PO₄)₂]. The observed homogeneous grains of Th and U poor monazite and tiny microcrystals of brabantite inside the apatite indicate dissolution of apatite during anatexis of sedimentary-metamorphic rocks. Little hematite (less than 10%) composition, which included within restitic biotite ± silimanite assemblages consistent with the idea that the Shir-Kuh granite is generated from the sedimentary source materials contained graphite. Considering the mineral assemblages, presented in the batholith, the fact that some biotites may represent restite and the mean temperature of 820°C is in agreement with the saturation thermometry; such liquids may have formed at a temperature 750 to 850°C by dehydration melting of biotite.

The study area is located in the central part of the Siahrood geological map, Kharvanagh of Ahar town, in the East Azerbaijan Province. The volcanic rocks of the Kharvanagh area include trachybasalt, trachy-andesi-basalt and trachy-andesite. The main minerals in the rocks are plagioclase, pyroxene, olivine and hornblende and the main textures are microlitic-porphyry. At the contact between the volcanic rocks and Miocene sandstones, epidote and calcite are formed due to thermal effect. Based on the geochemical data of major and trace elements, these rocks belong to High K alkaline to shoshonitic magmatic series. The absence of distinct Eu anomaly and relatively enrichment in LILE (Ba, Rb, and K) and LREE in these rocks indicate a back arc tectonic setting. Also enrichment of incompatible elements can be related to mantle metasomatism or contamination by continental crust. The chemistry of back arc rocks is relatively complicated and the geochemical features depend on the degrees of partial melting, heterogeneity in the sources mantle, etc. Considering the geological features and the Miocene age of the rocks, it can be concluded that the parental magma belongs to extensional basins magmatism, which produced from partial melting of the garnet lherzolite mantle.

Pyralespite garnet group (Almandine group) is common minerals in the metamorphic and igneous complex of Boroujerd area. Moreover, Almandin (Fe enriched garnet) is the most common mineral but the content of Spessartin (Mn enriched garnet) is high in this area. The changes of mineral composition in different grains show that these minerals are zoning chemical and core to rim composition is varied. The garnet composition in core to rim respectively in granodiorite changes to Alm_0.65, Prp_0.05, Sps_0.264, Grs_0.193 in core to Alm_0.76, Prp_0.05, Sps_0.14, Grs_0.04 in rim, in pegmatite, Alm_0.71, Prp_0.02, Sps_0.26, Grs₀ in core to Alm_0.76, Prp_0.03, Sps_0.2, Grs_0.007 in rim of pegmatite, and in hornfels, Alm _0.81, Prp_0.07, Sps _0.09, Grs_0.03 in core to Alm _0.63, Prp_0.06, Sps _0.3, Grs_0.002 in rim. Petrography (for exampl, crystallization of tourmaline to garnet pegmatites and Andalusite to granodiorites) and mineral chemistry (oscillatory zoning Al in pegmatite garnet, Mg decrease and Mn increase in granodiorites garnet and liner trend Al in garnet hornfelse) show that metamorphic source for garnet in granodiorite and hornfels and magmatic source for pegmatites.

Khut skarn deposit, located in the 50 Km NW of Taft,has formedin the result of Khut granodiorite intrusion into the upper Triassic impure carbonate rocks.Field evidences and mineralogical studies show Khut skarn is calcic type and exoskarn is the major skarn zone in area which associated with ore mineralization.The microprobe analyses show that there are two major types of garnet at garnet-pyroxene skarn zone: (1) Anisotropic garnets with 51_/76-63_/17 mol% grossular and (2) Isotropic garnets with 17_/77-28_/10 mol% grossular. Petrographic observations of anisotropic garnets show marked zoning and sector twining.Study of garnet zonation with electron microprobe in Khut skarn show chemical variations in Ti, Al, Fe, Mn, and Mgvalues form core to rim. In various zones, variations of Al, Ti and Fe are repeated alternatively. Hence, garnet zonation is caused by alternative variations of Fe, Al and Ti in composition of the fluid phase. This indicates multiple pulses of hydrothermal fluid flow.