مجله بلور شناسی و کانی شناسی ایران
سال بیست و دوم شماره 3 (پیاپی 57، پاییز 1393)

The Mafic complex of Mishow is exposed in the north-western part of Iran, in the East Azerbaidjan Province (SW of Marand). Two different types of mineralization, sulphides and oxides, occur in the intrusion complex. The sulphide ore bodies are mainly composed of pyrrhotite accompanied by chalcopyrite, pentlandite, sphalerite, pyrite and troilite. The oxides mineralization consists of ilmenite and rarely magnetite. Primary sulfides are replaced by pyrite and violarite during alteration states. Thermometry investigation, based on exsolution texture of chalcopyrite-sphalerite, suggest that sulfide zone probably formed at temperature higher than 400°C. The Co/Ni values of sulfides propose that they formed in a magmatic immiscible sulfide Ni-Fe-Cu system.

Simple folded Zagros has several phosphate horizons with the Cretaceous – Tertiary ages that are present as inter-layer in Pabdeh and Gurpy formations. Therefore, study of combination, texture of mineralogy and determination of genesis of marine phosphate of Zagros basin during Eocene – Oligocene is important. In this study, 28 samples were collected from phosphate Kuhe-e- Sefid and Kuh-e- Lar (Banari) horizons in anticlines for mineralogycal analysis. Mineralogical studied using X-ray diffraction showed that present apatite minerals in the samples are glauconitic, fluorine carbonate apatite and hydroxy carbonate apatite. On the other hand, study of thin sections confirms presence of phosphate such as pellets and ooids. Tracing of the mineral paragenetic sequence, indicate autogenic conditions, high sea levels and finally, shallow continental shelf environment, during the formation of these deposits.

Apatite is the most common phosphate mineral in the Esfordi ore body. Euhedral crystal (2-20 cm) of the apatite occurs as an intergrowth in magnetite and hematite, vein and dike. There are two types of apatite in the Esfordi deposit, based on Petrographic studies: primary and secendary. Fresh and altered parts of primary apatite display dark and light color respectively using BSE images. EMP analyses demonstrate that primary apatites (light area) were chlorapatite in composition and have been partially changed into hydroxyle-flourapatite (dark area) by the metasomatic process. Lighter areas represent more Cl, SiO2, Na2O and LREE+Y enriched apatites. Monazite and xenotime inclusions in apatite can be classified into two types: primary (30-100µm) and hydrothermal (5-20µm). The hydrothermal inclusions are found in the dark area, apatite crack and along grain boundaries. The monazite and xenotime inclusions in the dark areas are enriched in LREE and HREE+Y respectively. Monazite-xenotime thermometer yielded a temperature of about 150-350°C for apatite metasomatism and hydrothermal monazite-xenotime formation, coincides with greenschist facies conditions.

The Bozqush, Kaleybar, and Razgah foid-bearing syenites are located in East Azarbaijan province, NW Iran. Mineral chemistry determined for the amphiboles and clinopyroxenes of intrusions to specify elemental exchange, magmatic affinity, and tectonic setting. Chemical composition of the amphiboles varies from magnasio-hastingsite to ferro-pargasite. This study shows that the Kaleybar amphiboles are richer in Ca+IVAl than the Bozqush ones and CaIVAl=SiNa exchange is the main substitution. According to mineral chemistry, the clinopyroxenes are diopside. Considering the atomic proportion of Wo, En and Fs in the studied clinopyroxenes, variation in end-member components mostly involve the interchange of En and Fs. Moreover there is M2CaM1(Fe2+,Mg) = M2NaM1Fe3+  exchange in the clinopyroxenes. The Composition of clinopyroxenes and amphiboles indicate that they were derived from volcanic arc miaskitic magma at relatively low pressures. Based on Al and Ti contents, thermobarometry of the amphiboles show pressures of 6±1 and 7±1 kbar for the Bozqush and Kaleybar intrusions respectively and temperature of 900±100 ˚C.

Chemical analyses of chlorite flakes, as a product of alteration of biotite in the Eocene granitoid rocks of Naghade and Pasveh intrusions have been accomplished by electron microprobe for major elements. Based on 53 point analyses of chlorites from 13 rock samples, their mean structural formula recalculations display that Si cation numbers are less than 5.97 atoms per formula unit (apfu), and the sum of octahedral cations is very close to 12 both an indication of trioctahedral chlorite. The calculated mole fraction of chlorite in interlayered phase, Xc, ranges from. 0.86 to 0.94 confirming the purity of chlorite, i.e., the study chlorites are completely free of any smectite layers. Compositional variations in chlorite are strongly controlled by host biotite and rock type. Chlorite samples from Pasveh intrusion have Fe/(Fe+Mg) ratio ranges from 0.75 to 0.85 and Si contents from 5.14 to 5.69 apfu; those from Naqadeh intrusion possess Fe/(Fe+Mg) ratio ranges from 0.39 to 0.49 and Si contents from 5.45 to 5.97 apfu leading to the classification of chlorites mainly as ripidolite and pychnochlorite respectively. All major elements in the chlorite are strongly correlated with each other. Moreover, Fe/(Fe+Mg) ratio in biotite is well preserved by chlorite. Chlorite geothermometry based on the variation in tetrahedral Al content and Fe/Fe+Mg ratio within the chlorite structure shows a large variation in temperatures from 299 to 399 ºC with an average of 345 ºC for Pasveh intrusion and from 270 to 350 ºC with an average of 320 ºC for Naqadeh intrusion; both mean temperatures correspond with the mean temperatures of chlorite crystallization in a number of granitoid rocks of the world.

Eocene volcanic rocks in SW of Choupanan are exposed along the Choupanan fault as lava with andesite, trachyandesite to dacite composition and pyroclastic rocks. This area is a part of Central Iran (Yazd block). Andesite is the most predominant rock unit of the area and is composed of feldspars (andesine, oligoclase, and sanidine), amphibole (magnesio hastingsite, magnesian hastingsite, magnesio hornblende, and ferropargasite), mica (biotite and phlogopite), quartz, clinopyroxene (diopside, augite), garnet, opaque minerals (ilmenite, magnetite, titanomagnetite, and hematite), zircon, sphene and apatite. Minerals which are produced by alteration are calcite, chlorite (diabantite), and prehnite. SiO2 content of these rocks ranges 55.1 to 61.1 wt% and LREEs exhibit an evident enrichment. These volcanic rocks present a transitional affinity (between calc-alkaline and shoshonitic) and geochemically are similar to the volcanic arc rocks. The field, petrography and geochemical studies reveal that the studied andesites are formed by same petrogenetic processes and affected by magma mixing and contamination during crystallization.

Based on the field observations host rock of tourmaline nodules in the Dehgah and Sarsakhti area are acidic dikes (Aplite) and monzogranite respectively. In these areas, nodules composed of tourmaline, quartz, alkali-feldspar, but leuco minerals component in Dehgah nodule are less than Sarsakhti area. The negative anomaly of Eu, enrichment in the light REE (LREE), decrease of HREE, and  fractionated REE chondrite normalized patterns in host rocks in these area suggest that crustal granites produced by partial melting of metapelitic rocks. Zoning, schorlite to dravite composition, nodules concentration in roof zone of the batholithe, decreases in abundance with depth, low ratio of Fe/Fe+Mg in some nodule (dravite), clear halo and miarolitic cavities in Sarsakhti area are evidences that exsolution of their fluid phase occurred at low rate and reacted to volatile to wall rocks (metapelites) fluids and are composed from magmatic – hydrothermal conditions. However, tourmalines in Dehgah area, with schorlite composition, host rock with planar structural (aplite), lack of zoning and clear halo, and lack of miarolitic cavities suggest that boron rich volatile has not been reacted with wall rocks (metapelites) fluids and in a perfect magmatic condition, immediately percolated to acidic dikes and caused in the final crystallization of tourmaline nodules. Therefore different rates of boron and its fluid behavior in the hydrothermal-magmatic system is the major factor controlling of spherical shape tourmaline nodules in the two studies areas.

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

The Alvand plutonic complex is composed of various plutonic rocks, mafic and felsic dikes (pegmatites and aplites). Pegmatites and aplites consist of quartz, feldspar, mica, tourmaline, garnet and allanite. Based on the mineralogycal compound, pegmatites can be divided into tourmaline-garnet-muscovite-bearing, aluminosilicate-bearing and tourmaline-bearing pegmatites and aplites are composed of tourmalime – bearing, garnet – bearing, and tourmaline – garnet – muscovite-bearing pegmatites. Based on the geochemical properties, pegmatites and aplites can be divided into sodic and potassic groups. Harker and spider diagrams show that the pegmatitic and aplitic dikes are co-genetic and the mafic dikes and other mafic to intermediate rocks in this area are co-magmatic. The studied felsic dikes are peraluminius and calcalkaline. Mafic dikes are calc-alkaline to tholeiitic and meta-aluminous. Type of garnets in pegmatites are pyralspite )Sps61.5- Alm34.6-Grs3.1-Prp0.8( and plagioclase in pegmatites and aplites are (An2-5) and (An7-13), respectively. K-feldespars in pegmatites have intergrowth of albite up to about 50%. White mica in pegmatites and aplites plots between muscovite and celadonite. Biotites in aplites are of siderophyllite type and allanite in pegmatite is Ce-rich type. Based on geochemical studies, in spider diagrams felsic and mafic dikes and mafic host rocks show depletion of HREE and Zr, Hf, Y, Ti, Ta and Nb elements and enrichment of LIL (K, Rb, Cs) and LREE elementswhich indicate their formation in a subduction environment.

Balazard area is located in west of Nehbandan in the center of Lut Block. Eocene andesite and rhyolite cover most of the area. Subvolcanic rocks such as quartz monzodiorite porphyry, biotite quartz diorite porphyry, pyroxene hornblende diorite porphyry, hornblende pyroxene quartz diorite porphyry and hornblende diorite porphyry intruded the volcanic rocks. Evidence such as disseminated sulfide mineralization and intense alterations, indicates high potential of mineralization for this area. Alteration and mineralization cover more than 20 square kilometer areas. Volcanic and subvolcanic rocks are highly altered, contain argillic, sericite-argillic, silisic-argillic, advanced argillic and propylitic. Mineralization is present as disseminated and veins. Hypogene minerals in intrusive rocks are pyrite and chalcopyrite and in carbonate-quartz veins are pyrite, sphalerite, chalcopyrite and galena. Supergene minerals are chalcosite, covelite, malachite and azurite that seen in carbonate- quartz veins. Geochemical data show high anomalies of Au, Ag, Cu, Zn, Sb, As and Pb respectively, with maximum values are 2470 ppb, 114 ppm, 1250 ppm, 2462 ppm, 103 ppm, 98 ppm and 968 ppm. Geological, mineralogical, alteration and geochemical studies indicate that sulfide mineralization in carbonate-quartz veins has formed by the influence of hydrothermal fluid that moves in faults and shear zone. In addition widespread and disseminated pyrite and chalcopyrite mineralization associated with alteration zones, represents a widespread activity of hydrothermal fluids.

Delbar metamorphic complex composed of schists, amphibolites and gneisses with migmatitic views belong to Neoprotrozoiec (Precambrian) is located in southeast of Shahrood. Debar metamorphic complex crosscut by at least three series of mafic dikes, with different ages (Precambrian, Jurassic and Tertiary). Jurassic dikes intruded in Precambrian metamorphic complex and upper Triassic - lower Jurassic metamorphosed detrital sedimentary rocks (equivalent to the Shemshak Formation), but not continue in the middle Jurassic sandy limestone and lower Cretaceous (Neocomian) limestones. Amphiboles of the mafic dikes are Edenite type Ca group amphiboles. Barometry based on the Al+3 content of the amphiboles indicated 4-5 Kbar presuers equivalent to the final equilibrium of amphiboles, illustrated 14-15 Km depths to the implacement of the studied dikes in the crust. U-Pb Age dating on apatites from the mafic dikes, indicated 152± 35 Ma age which completely confirmed field and stratigraphic relationships. The mafic dikes have alkaline to calc-alkaline nature based on the geochemical characteristics. The parental magma produced from 15% partial melting of a spinel lherzolite mantle source. These mafic dikes generated in a back arc extentional setting related to the continental crust extentions of central Iran caused by Neotethys plate subduction under it. This event is related to the magmatism of early Cimmerian orogeny.

Olivine is one of the major crystals in ultrabasic rocks of Piranshahr Ophiolitic Complex. This mineral occurs as anhedral with cracks and fractures. Commonly, olivine is altered to serpentine along the fractures and rims. In some cases, serpentine crosscut the olivine. According to BSE images and mineral chemistry studies of olivine, the secondary iron- rich olivines occur at the rim of primary olivines. The forsterite content of the secondary olivines is lower than the primary olivines. XFo in the secondary olivines varies 85.6 to 87.7. Textural studies suggest that iron- rich olivines formed during serpentinization. Occurrence of Mg- rich serpentine and lack of magnetite during serpentinization of olivine caused formation of Fe- rich fluids. The iron- rich fluids may infiltrated through the olivine crystal and formed iron- rich rims.

The pegmatitic and aplitic dikes in the Alvand plutonic complex and metamorphic rocks of its contact aureole (hornfelses) are the latest magmatic phase in this area. In addition, at distances away from the Alvand plutonic complex, various pegmatitic-aplitic dikes intruded in the regional metamorphic rocks. Tourmalines from Alvand dikes, observed as nodules and sometimes with graphic intergrowths between tourmaline-feldspar and tourmaline-quartz and as sun tourmalines (luxolianite). While in the pegmatite from the Zaman abad-Mangavie area tourmalines have pegmatitic euhedral shapes. The studied tourmalines lie in alkali tourmaline group and have shorl-dravite composition. Based on the observed trends in diagrams, replacement reaction in these tourmalines is  } ,Al{{(Mg,Fe)Na}-1,   replacement of Al in Y position and   AlNa-1Mg-1. Based on the geochemical characteristics of these tourmalines such as variation of Fe/(Fe+Mg) ratio, plotting of some sampls between proton and alkali deficient vectors and some samples out of these two vectors and wide range of F in these samples;  both magmatic and hydrothermal processes involved in the formation of these tourmalines. The studied tourmalines are related to Li-poor granitoids and associated pegmatites and aplites.

Shekaste Sabz area is located in eastern Iran, about 96 km north west of Birjand. Preliminary prospecting in the area using ASTER mineral mapping (SAM) detected propylitic, argillic and sericitic alteration which was confirmed by field observation. The area comprises outcrops of Paleocene to Eocene volcanics, which was intruded by intermediate subvolcanic bodies. The main alterations zones are propylitic, argillic and silicified- carbonate. Mineralization is observed as vein (in central and west of area), veinlet and disseminated (in east and west). Veins show North West - South East to North East - South West trend and dip 85 to 90 degrees. Due to the great influence of weathering processes on the hypogene mineralization, secondary sulphide and oxide minerals spread widely and formed malachite, azurite, chalcocite, covellite, goethite and hematite. Relicts of the hypogene minerals such as pyrite, chalcopyrite and magnetite are also seen. Gangue minerals are quartz, calcite and barite. The maximum amount of copper and zinc distribution in stream sediments are located in the areas that vein mineralization and propylitic, argillic- sericitic and silicified alteration zones exist in their upstream. The range of variation for elements in the lithogeochemistry samples are as follows: Cu from o.6 to 2.4 Percent, Mo from 77 to 2290 ppm, Zn from 23 to 2990 ppm, Pb from 24 to 754 ppm, Ag from 1.4 to 8 ppm. The maximum amount of elements in the lithogeochemistry samples are in places which veinlet and disseminated mineralization are associated with andesite.  These are as follows:  Cu 450 ppm, Zn 162 ppm, Pb 309 ppm, Mo 77 ppm. According to alteration type, Anomalous Cu, Zn, Ag and Mo and relation of mineralization with fractures system, Shekaste Sabz mineralization can be placed in the category of vein- type epithermal deposits.

The Aligoudarz granitoid occurs in the central part of the Sanandaj-Sirjan Zone, western Iran. It comprises three distinct facies mainly of tonalite, granodiorite and granite composition. Magmatic microgranular enclaves (ME) extensively occur in granodiorite. Field, textural, whole rock and mineral chemistry data of the ME and the host rocks does not support magma mixing as the ME-forming mechanism. Major and trace elements variation diagrams, similarities in spider diagrams and geochemical modeling indicate the cogenetic relation of the ME and host rock. Fractional crystallization is the main process in the geneses of ME. Rapidly-cooled borders of the magma chamber can best explain formation of the ME. ME are the result of later fragmentation and dispersal of the rapidly-cooled borders in the host magma. These enclaves recorded the least degree of chemical exchange with the host. Biotite and amphibole crystallize with more rapid nucleation rates in rapid cooling zones. This process can explain different chemical behavior of the ME and the host rock.

In this study, we have prepared nanopowders of Yttrium Iron Garnet (YIG). Phase formation and crystalline structure were investigated by X-ray diffraction (XRD) and IR spectroscopy. Room temperature saturation magnetizations (Ms) of the samples were evaluated using a vibrating samples magnetometer (VSM). The results show that the size of nanoparticles renge from 70 to 250 nm. The results of structure investigation show correlation between Lattice constant and particle size of samples. The Critical size was obtained about 200 nm.