Igneous bodies in Manshad-Taft fau lt
zone arc intruded into Shirkuh granitic batllolilic
basement. They also cause different skam-marble
mineralization in dolomitized limestones which are
covered granitic basement. Skarns are composed of
variety of minerals. Marbles consist of variolls
minera ls such as brucite, forste rite, diopsid,
pcriclase,taJc, calcite, dolomite, and hydromagnesite.
Petrographic and geochemical data have revealed
tbat there is several stages duri ng the formation of
marble minerals. At the first stage, anhydrous
minera ls fonned, then fo llowed byhydrous
assemblage. Generation of brucite occurs at the
second stage and is due to latc hydrothermal system
withlow XCOl and high nuids.
Hydromagnesite deposition is occurcd by oxidation
of bruc ite.

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.

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.

Copper-bearing skarn zone in east of Sungun-Chay river is
located about 100 km NE of Tabriz, and was developed along the contact of
the mineralized porphyry granitoid stock (Oligo-Miocene) with impure
carbonate rocks (Upper Cretaceous). Both endoskarn and exoskarn occurred
in this zone. Endoskarn is narrow (~0.5-2m) whereas exoskarn is relatively
broad (25-55m) and contains minerals such as calc-silicates (grandite,
diopside-hedenbergite, tremolite-actinolite, epidote), silicates (quartz,
chlorite, and clays), sulfides (pyrite, chalcopyrite, sphalerite, galena,
bornite), oxides (magnetite, hematite), and carbonates (calcite, ankerite).
Skarnification processes occurred in two distinct stages, including
progradation and retrogradation. Calculations of chemical index of alteration
(CIA) indicate that the exoskarn underwent metasomatic alteration within
the range of 8.41% to 57.29%. Analysis studies of mass changes of
elements, on the basis of Nb (as a monitor immobile element), indicate that
considerable amounts of elements such as Fe, Si, Mg, S, Cu, Pb, and Zn
were added to the skarn system by hydrothermal fluids from the side of
pluton, while substantial amounts of Ca was leached out of the system. The
overall obtained results show that elements such as Fe, Si, and Mg were
introduced into the skarn system by metasomatizing fluids during both
progradatian and retrogradatian stages whereas the ore-forming elements
such as Cu, Pb, Zn, and S were added to the system mainly during retrograde
stage. The inharmonious mass increase of Al and portion of mass changes of
Si are due to the local variations of pelitic impurities within the carbonate
rocks (as protolith).

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.

One of the metamorphic rocks in the Nain ophiolitic mclange is
skarn which is fonned during the contact metamorphism of intrusive
tonalites with their neighboring limestones and carbonate parts of banded
cherts. Minerals of these skarns consist of carbonate (calcite). clinopyroxene
(diopside). garnet (grossular-andradite). wollastonite, sphene and epidote.
Also tonalites contain quartz, plagioclase (albite). alkali feldspar
(orthoclase). garnet (almandine-spessartine) and prchnite, Based on mineral
assemblages ofNain skarns as well as geothennometry of feldspars existing
in relevant granites and also applications of different calibrations of garnet·
clinopyroxene geothennometer. the Nain skams fonn at temperatures of
about 440 to 650 °C al low pressure during a contact metamorphism which
has occurred at hornblende hornfels to pyroxene hornfels facies.

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.

Mineralogical and geochemical investigations indicate two general stages of skarnification i.e, prograde and retrograde stages in the Mohammad-Abad district, south west of Yazd province. Metasomatic skarn (Prograde stage) occurred with precipitation of anhydrous calc-silicate mineral assemblages (andradite and diopside- hedenbergite) within the temperature ranges of 470 to 550 ºC. During the retrograde stage (<470 ºC) considerable amounts of anhydrous calc-silicates were altered and replaced by a series of hydrous calc-silicates (epidote, tremolite–actinolite). Finally, both anhydrous and hydrous calc-silicates were altered to fine aggregates of chlorite, calcite, quartz and clay minerals at temperatures lower than 300 ºC. The absence of wollastonite among the calc-silicate assemblages may suggest that andradite and hedenbergite were crystallized from metasomatizing fluids at lower than 550 ºC in the Mohammad-Abad skarn. The presence of intergrowth texture and non-replacive crystal boundaries between garnets and pyroxenes suggest that they were formed   contemporaneously within the temperature and fO₂ ranges of 430–550 ºC and 10^-26–10^-23, respectively. Andradite converted to quartz, calcite and magnetite below 470 ºC and fO₂ = 10^-24–10^-21. Since, both magnetite and pyrite along with quartz and calcite are present in mineral assemblages of sub-stage III, it can be reasoned that the metasomatizing fluids probably had an approximate fS2 10^-6.5 and a temperature of about 430 ºC.

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.

Based on field observation, magnetic data results and chemical analysis of the samples in the Haj - Elyas area northwest of Nehbandan, an iron ore body within the Lower Cretaceous dolomitic limestone, was identified. The intrusion of a Fe-bearing porphyritic diorite into the dolomitic limestone caused the occurrence of iron mineralization in the area. Studies of 750 meters of diamond drill Core logs, indicated that the mineralization occurred at the contact of porphyritic diorite and dolomitic limestone. The ore minerals in this zone are magnetite, hematite and limonite. Gangue minerals are plagioclase, quartz, calcite, dolomite, garnet, clinopyroxene, hornblende, tourmaline, hercynite, serpentine, epidote, pyrite, sphalerite and chalcopyrite. Garnet is more andradite in composition. Magnetite is altered to hematite and limonite in fractures. The average iron grade within mineralized zone is about 70 percent. Copper and zinc show very low grade. Based on mineralogical data, the mineralization at Haj - Elyas is associated with calcic – magnesian skarn type.

Mazraeh granidiorite is part of Shyvardag plutonic batholith which is located in eastern Azarbajan, 20 km north of Ahar town and 5 km north of Mazraeh Village. It is a part of Mesozoic –Tertiary igneous belt of the Sanandaj-Sirjan. From petrography and geochemical point of view, rocks are acidic to intermediate and the main part of the body is granodiorite. Texturally, the rock is mainly granular, containing plagioclase, alkali feldspars, quartz, and hornblende. The accessory minerals include biotite, sphene, magnetite, apatite and epidote. Geochemicaly, this granodioritic rocks are calk alkaline an I type series and is Metaaluminous with VAG characteristic. Based on Harker type diagrams, the incompatible elements as well as compatible elements have a continuous trends, which indicate fractional crystallization of magma during the evolution of intrusion of the rock in the region and other processes are in second order. The presence of amphibole minerals indicate that the primary magma was rich in water (%3). In addition, enrichment of magma from elements like Fe, Ca, Mg, Co, Ni   and reduction of elements like K,Na, Th in low Si  samples proved that the amphibole have been crystallized at the intail stages of fractional crystallization but minerals like albite, alkali feldspar and biotite were crystallized at the final stage. Intrusion of this body to in the carbonate rocks caused the skarn mineralization which indicate the potential of mineralization of these grandiorities. Comparison of Mazraeh granodiorite with other granodiorite, such as Qulong of Chinese, Rio_Narcea belt in Spain, Celebi in Turkey, Songun and Tokmedash in Iran indicate that   Mazraeh granodiorite enriched in elements like Th,Nb,La,P,Pb. These geochemical differences with other granodiorite could be due to their different shares from enriched mantel and crust during the formation of these granodiorites.

Tang-e-Hana skarn is located at part of the Zagros ophiolitic sequence, and then it is considered as a part of the Zagros structural province. According to the current study, this skarn is classified in 4 main groups: 1- Wollastonite skarn 2- Augite wollastonite skarn 3- Grossular wollastonite skarn 4- Andradite titanite augite wollastonite skarn. Geochemical characteristics indicate that Tang-e-hana skarn is lies in the calcic skarn domain. In addition, percentage of TiO₂ in the fourth type of these skarns (bearing titanite) reaches 4%. This fact is important for concentration of REE and other trace elements in titanite. The field and mineralogical evidence illustrated that the studied skarns are endoskarns. These evidences include a high percentage of calc-silicate and non-metallic minerals and in contrast a low percentage of metallic minerals. Therefor, Tang-e-hana skarn is important for its non-metallic minerals such as wollastonite and garnet. The study of mineral paragenetic sequence and the variation diagrams of %TiO₂ and %Al₂O₃ per %CaO suggested that wollastonite skarn is formed at the early stage and andradite – titanite – augite - wollastonite skarn at the late stage of skarnification.

Galali orebody is located in Sanandaj-Sirjan zone in west of Iran in the Karamkhani slops in Almogholagh mountains. The main ore is magnetite association with hematite, goethite, secondary limonite, malachite and pyrite. This orebody is located on north Galali fault; mineralization is made by fault movements in this orebody. Three types of ores have been seen in the Galali orebody as below: Type I: this ore is made of compact, high density and high grad magnetite. Fine grain, subhedral to unhedral pyrite has found in this type as minor mineral. Pyrite is dispersed in magnetite. Type II: this ore type are made of silicates, oxides and sulfides, this phase is injected in the   type I minerals. Type III: the hydrothermal goethite is the third type of ore in the Galali orebody. Skarn, epydotization, dolomitization and some argilic veins are alteration haloes around the orebody. Evaporatic origin is recognized for sulphur isotopes in this study.

Intrusion of granodioritic bodies into the lime stones of Ghorveh area led to the formation of calc-silicate marbles and various types of skarns. These skarns consist essentially of calcite, clinopyroxene, garnet, wolastonite, vesuvianite and epidote. Based on geochemical studies, garnets were identified as grossular and anderadite. The clinopyroxene found in the skarns is diopside. With respect to mineral assemblages identified in the skarns and using various calibrations of garnet-clinopyroxene geothermometery, the temperature of skarns is estimated to be in the range of 450 to 587^oC corresponding to hornblende hornfels to lower field of pyroxene hornfels facies.

The widespread stratigraphic sequences, from Precambrian to Cenozoic have been affected by metasomatic and thermal- metamorphic events of the Pliocene age by the Alam- Kuh alkali-granitic intrusion. Skarnification is the main metasomatic type in the studied area with 1-2km in extent. This intruded alkali-granite is probably related to syn-collision and post collision tectonic regimes as A-type granite. Intrusion of alkali-granitic rocks into the surrounded wall rocks caused to form the skarn zones and oxide-sulfide mineralization, mainly consists of magnetite and some chalcopyrite as well as pyrite. The fluid inclusion studies show five types of inclusions in quartz synchronous with mineralization as V + L + S, V + L, L + V, L, and V. Geothermometric evidences indicate temperatures of 478°C- 488°C and 368°C- 378°C for oxide phase formation and sulfide mineralization respectively. Magmatic and meteoric fluids mixing are effective in generation of fluids during mineralization processes. The field geology evidences, microscopic and geothermometery characteristics suggest a skarn origin for the metallic mineralization of the Alam- Kuh intrusive body.

Triassic (mostly volcanic-carbonate) and Jurassic (mainly shale and sandstone) rocks in west of Malayer were affected by a number of shear zone, folding, deformation and metamorphic events. Regional metamorphism in the area led to the formation of Triassic and Jurassic rocks such as phyllite, slate and crystalline carbonate which folded during deformational events. In the contact metamorphism event, granitoid plutons with predominantly granodiorite to quartz-diorite composition intruded the metamorphic rocks, forming mineralized skarn zones in Anjireh, Iraneh and SarabSaman areas. The present research shows that plutons producing the mineralized skarn zones in the area are on average granodioritic in composition. Pyroxene and garnet minerals in the skarn zone comprise of diopside, augite and grandite (mainly andradite), respectively. In these skarns, various sub-zones are recognized and defined on the basis of their mineral paragenesis. High temperature facies (pyroxene-fels) formed in the temperature range of 650-800 ºC and wollastonite up to 800 ºC. However, hornblende-fels and albite-epidote-fels facies formed in the temperature ranges 500-650 and 350-500 ºC, respectively.

The study area is located at the Soghanchi village (east of Miyandoab city, NW of Iran). The Oligocene age Soghanchi stock is intruded into Permian carbonate rocks during Pyrenean orogenic epoch. Petrographically, the main minerals of this intrusive are plagioclase, biotites, pyroxenes, olivines, hornblendes, and alkali-feldspars. The microscopic and geochemical assessments of intrusive, show gabbro-dioritic, monzo-gabbroic and monzonitic composition with high potassic- calc-alkaline to shoshonitic and meta-aluminous characters. Based on this investigation, the Soghanchi pluton has formed in a continental arc setting. Intrusion of this stock into the Permian limestones, results in different degrees of recrystalization and skarnification. The Soghanchi calcic skarn is mainly composed of anhydrous calc-silicates, retrograde metasomatic products, some calcite, and quartz. Magnetite and minor hematite are the main metallic minerals in this area. Physco-chemical investigations showed 450-650^oC for skarnification (prograde stages) and 400-450^oC for retrograde metasomatic event and iron mineralization.

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.

Panah Kuh skarn is located about 50 km northwest of Taft City in Yazd province. The intrusion of Panah- Kuh stock with granodiorite-quartz diorite composition into the limestone Jamal Formation has led to the skarnification in this area. Field and mineralogical observations show that Panah-Kuh skarn included two endoskarn and exoskarn zones. Exoskarn is calcic type and magnesian skarn which formed in contact with the marbles whereas endoskarn formed with restrict development into intrusion. Dominated minerals are garnet (andradite) and pyroxene (diopside-hedenbergite) in the calcic skarn and forsterite, diopside, serpentine and talc in the magnesian skarn. At least two paragenetic stages of skarn formation have been recognized. The early skarn formation (stage I) was dominated by anhydrous minerals such as pyroxene and garnet in the calcic skarn and forsterite and diopside, in the magnesian skarn. According to mineral assemblages which formed at this stage, it can be concluded that the temperature range was less than 500 ⁰C. The hydrous skarn assemblage such as serpentine and talc (stage II) replaced early-formed skarn assemblages. The mineralogy and geochemical characters of Panah-Kuh skarn is consistent with deposition under oxidized conditions, formation at shallow crustal levels and similar to those of Fe bearing skarn system.                    

Garnet is the most abundant calc-silicate mineral in the Darreh Zereshk skarns, and occurs as grained euhedral, to massive anhedral, isotropic to anisotropic crystals and display concentric and sector zoning or no zoning. Based on mineralogical investigations and paragenetic relations, garnet formed during progrademetasomatic stage of skarn formation. Geochemically they display two different patterns, i.e: (1) LREE-enriched and HREE-depleted, with strong positive Eu anomaly and (2) HREE-enriched and LREE-depleted with small Eu anomalies characteristic of andraditic and grassuleritic garnets, respectively. Electron probe micro analyzer (EPMA) identifies the garnets from Darreh Zerreshk skarn as grossular–andradite (grandite) solid solution series, with a less contents of spessartine and pyrope components. This is significant of a composition similar to Cu, Fe and Au skarn.