fariborz masoudi

Damavand is a young volcanic edifice with an elevation of 5610 meters formed in the middle of the central Alborz Mountain range (N Iran) during the Quaternary. Its edifice is composed of trachyte and trachyandesite rocks, pyroclastic fall and flow deposits and lahars, formed during several eruptions and under different magmatic conditions. To investigate the crystallization trends in the Damavand magma chamber and its evolution over time, plagioclase internal textures in lava flows, pyroclastic flow and ash deposits were studied. Samples from six different lava flows and pyroclastic fall and density current deposits with different ages were collected. Plagioclase crystals with similar dimensions and sizes but with completely different textures, and plagioclases with different dimensions but similar textural characteristics were observed. Twenty-eight different texture types were observed in plagioclase crystals from lava flows, whereas only three texture types were distinguished in the pyroclastic deposits. A large population of plagioclase in pyroclastic deposits reveal the non-equilibrium crstallization in the Damavand magma chamber(s), while in lava flows, a series of plagioclase cumulates present both equilibrium and non-equilibrium crystallization conditions in the magmat chamber. Plagioclase crystals in the source magmas of lava flows have repeatedly remained in a non-equilibrium state without eruption, letting the crystals to overgrow. Changes in the rate of magma ascent, small- and large-scale convection cells in magma chambers, varying temperature and/or pressure, and different volumes of (non-)eruptible mush/melt, are some of the parameters that are revealed by our textural studies. In the period between about 7-450 ky ago, the magma chamber that led to the buildup of the young Damavand volcano, was in non-equilibrium conditions as demonstrated by individual crystals textures and chemistry. However, these conditions have not always led to volcanic eruptions.

This study is aimed to determine the Fe content in natural epidote from Varan area (Urumieh-Dokhtar Magmatic Arc, Iran) by using vibrational FTIR and Raman spectroscopy and EPMA analyses. Fe3+ concentration calculated from FTIR spectroscopic data is in the range of 0.96 to 1 apfu. The results are in complete agreement with EPMA data. The comparison between obtained Raman spectra of studied epidote grains and those from the RRUFF database suggest that epidote from Varan area is rich in Fe3+. High Fe3+ content might reflect moderate to high oxygen fugacity during the crystallization of epidote. This short paper demonstrates that the quantification of the Fe content in epidote via FTIR method is as good as EPMA, whereas the utilization of a low-cost Raman spectrometer  helps in quickly distinguishing between Fe-rich and Fe-poor epidote, which even could be useful in the case of field studies.

Mineralogical studies play a key role in deciphering mineral’s formation and associated geochemical processes in geosciences. This paper presents the application of Raman spectroscopy to the characterization of actinolite in rock samples. The studied actinolite was formed as the pseudomorph of primary pyroxene in gabbrodiorite intrusive rock sample collected from Varan area, Urumieh-Dokhtar Magmatic Arc of Iran. The Raman spectra of micrometer-sized actinolite grains embedded in a crude rock sample are compared with the corresponding literature data for actinolite and tremolite in range of 200-1200 cm-1 and 3600-3700 cm-1 region. The results show that the quantitative estimation of Mg# = Mg/(Mg+Fe2+) can be obtained from the fractional intensities of the OH-stretching bands by applying Raman spectroscopy to micrometer-sized actinolite grains in a crude rough rock sample, which is in good agreement with the results from EMPA. The Raman spectroscopy is a fast method and low-cost for quantitative estimation of Mg# in actinolite.

In this study, irradiation treatment was examined on colorless and clear quartz crystals collected from east of Qazvin (EQ) and southwest of Astane (SWA) regions in Iran. EQ crystals up to 3 cm were found in the geodes in andesite and trachyandesite, while idiomorphic crystals up to 2 cm from SWA formed in cavities and vugs in rhyodacitic host rocks. Crystals of both locations were exposed to gamma rays under the same conditions in steps of 100 kGy, 200 kGy and 300 kGy. No specific color change was observed for EQ crystals, while colorless SWA samples completely turned into dark gray or smoky gray from 100 kGy onwards. Comparing chemical analysis (ICP_MS) of samples revealed that SWA crystals contain more impurities with significantly higher Al. Representative Al contents in EQ and SWA samples are 322 ppm and 3378 ppm respectively. Data from Raman and infrared spectroscopy structural analyses, show similarities between studied samples from both regions. Formation of smoky quartz after radiation is related to color center defects. Field evidence reveal the direct effect of hydrothermal fluids and vapors related to Astane granitic intrusions on country rocks in the aureole, in forming colorless quartz crystals with high concentrations of aluminum impurities substituting Si.

Eocene Green Tuffs are widespread in Central Alborz in the north of Iran. In parts, they are used as natural Pozzolan. In this study, the Pozzolanic activities of tuff samples from Qazvin to Semnan in Alborz Mountain were examined. The Pozzolanic activity patterns vary in different beds and even change laterally. Chemical examination of the samples indicated that they all belong to acidic rock group and were consistent with related standards. Pozolanic activity calculated for samples using hydraulic factor, thermal analysis and ion concentrations. Data obtained based on thermal analysis, presented a range of Pozzolanic activities for tuffs with similar chemistry and appearance. It was found in this research that mineralogy and texture controlled Pozzolan activity. Tuffs with high activity had glass in their matrix, but weathering and recrystallization reduced the activity. Petrographical examinations play an essential role in evaluating the availability of tuffs as natural Pozzolan in Central Alborz.

Fariman metamorphic complex located in Northeast of Iran and indicative different metamorphism and deformation phases. This area is similar to many others Precambrian metamorphic rocks in central Iran that metamorphed in upper amphibolite facies and Sillimanite zone. In this research microfabric of andalusite schists and magmatic rocks investigated in order to constrain P-T path during metamorphic events. Studied metamorphic complex contain metasandstone (metapsemites), metagraywack and metacarbonates are as interlayered with metapelitic rocks that are major part of metamorphic rocks in study area. The metamorphic volcanic rocks also are seen that named Sibac complex and are in contact with granitic and gabbroic rocks. For petrography and microfabric studies, 80 oriented samples selected from andalusite schists and igneous rocks from Sibac complex. The samples cut and thin sections prepared. Metamorphic rocks of Fariman have effected by two deformation phases, D1 and D2. D1 phase related to M1 that is a regional metamorphism event and D2 as an active deformation is related to dynamothermal metamorphism of M2. M2 reveals emplacement of nap and outcropping of lower crust and present an erosion window of neoprotrozoic rocks that are appeared as an uplift formation from central Iran basement that emplaced close to Paleozoic-Cenozoic sedimentation. The retrograde event has affected metamorphic rocks after M2. Evidences of this retrograde metamorphism are change andalusite to chlorite and muscovite or sericite and muscovite, growth of chlorite and talc in rim or on the other mineral, forming of tourmaline in rim of andalusite or in the veins. The D1 phase created schistosity S1, D2 has folded S1 and has formed S2 schistosite. Microstructure evidence, mineral paragenises and estimated Pressure and temperature show an anticlockwise P-T path that involving advective heating in result of intrusive abundant magma into lower- middle crust. The peak of Metamorphism followed by isobaric cooling. The affect of shearing motion is not equal in throughout of study area and in different rocks. Microtectonic evidences indicate a deformation in both ductile and brittle conditions with dextral component. Shear zones spatially can be observed in south and southwest of study area and has been made mylonites and phylonite type rocks. In Fariman area, first high T-low P metamorphism occurred, and followed by dynamothermal metamorphism with shear zones.

The Ravanj intrusive, with tonalite, quartz-diorite, and microquartz-diorite composition, is exposed in the West of Ravang Village, NE Delijan, in Urmia-Dokhtar zone. Plagioclase is observed in three different sizes (coarse, intermediate, and microcrystalline) in the composition of in Ravanj intrusive. Most of the coarse crystals are zoned while intermediate and microcrystalline show polysynthetic and pericline twins. The lack of inclusions in the center of plagioclase and An versus K2O with a linear trend indicate that plagioclase is the main magma phase. The chemistry of polysynthetic crystals is in the range of An30.96 to An58.75, and the variation of Fetotal is the same as An, which determine normal crystallization state with temperature equilibrium. The chemistry of zoned plagioclase with oscillating zoning are analyzed from rim to rim, which is the minimum and maximum of An in microquartz-diorite is An36.58 to An60.94 and in tonalite is An41.92 to An54.12 respectively. The rim-to-rim trend of An and Fe, Mg, and Ti elements in the zoned plagioclase shown oscillatory zoning which indicate that crystallization process of fractional crystallization accompanied by the recharges of mafic magma in the state temperature equilibrium. The recharges of mafic magma in the center of intrusive are higher than the margin.

Opal, known as Aghigh in Persian, is one of the main semi-precious rock in Iran that is present in Bayag active mine in NW of Torbat Heidarieh. Mineralogy of agate is crucial for its treatment and cutting. In this research, mineralogy of agate in Bayeg mine investigated using SEM, Raman analyses and ICP methods.  Chalcedony introduced as the main constituent of agate in literature. However, this research revels opal, chalcedony and moganite are main minerals of Bayeg mine respectively. In hand specimen, chalcedony show white and milky color, and opals are gray to dark. ICP-MS analysis showed that amounts of AL and Na, Ba and Sr present as trace of meteoric and hydrothermal fluids and igneous activities during the formation of opals

Application of mathematics increasing in science in recent years, cause the mathematical models use to explain the geological processes. The researchers introduced a method based on mathematical calculations and algebraic model for metamorphic reactions. Pelitic metamorphic aureole is formed in North of Borujerd granitoid complex in the region east of Borujerd city. In this research for the first time, using a mathematical method for metamorphic reactions for high temperature of Pelitic metamorphic aureole based on algebraic model. Based on petrography, mineral assemblages of a rock are known and a thermodynamic system and components could be drive. SiO2, Al2O3, MgO, FeO, K2O and H2O Accepted as components and the system KFMASH chosen for calculation. Based on mineral assemblages, metamorphic reactions calculated using 6 by 6 and 6 by 8 matrices. Components put in Matrix and when Matrix’s elements below the diagonal are zero, then the calculation is applied over the second matrix to find metamorphic reactions. Equilibrium reactions could be written based on both microprobe analyses and general mineral formula. The main reactions in the intermediate zones toward the contact, in order from low to high temperature, are cordierite formed after reaction of biotite, quartz and andalusite followed by equation of andalusite to sillimanite. Potassium feldspar appears in the same rocks with sillimanite. Potassium feldspar and cordierite formed close to the contact zone, Petrographic result confirmed paragenetic minerals which appeared in algebraic analysis. The results show that reactions constrain based on algebraic analysis, could be used to estimated pressure and temperature in petrologic grids

The Agh-Daragh study area in the north of Ahar is located in Ahar-Arasbaran zone. The area is distinguished by W, Cu and Au metal endowment and has been explored during stream sediment and heavy mineral exploration. At least, three mineral occurrences are detected in Agh-Daragh area including Cu stockwork-disseminated mineralization in Chupanlar (occurred in Omz quartz-monzonite), Cu-Au±W vein-type mineralization in Ayran Goli (occurred in Og granodiorite), and Fe±Cu skarn in Gowdal (occurred between quartz-monzonite unit and crystallized carbonate). Chemically, Agh-Daragh mineralization-related metaluminous granitoids belong to oxidized, I-type and high-K calc-alkaline to shoshonitic series. They have SiO2 = 63.5–67.6 wt%, Al2O3 = 14–16.5 wt%, and K2O/Na2O = 0.5–1.8. Moreover, LILE enrichment relative to HFSE depletion and HREE in the granitoids and the dikes occurred due to fluid-melt interaction, which are characteristics of subduction tectonic environment. In their magmatic evolution, the Agh-Daragh intrusive rocks underwent a transition from the early intrusive phases belonging to granodiorite (Og unit) with low K/Na and Fe2O3/FeO ratios and to the late intrusive phases belonging to quartz-monzonite (Omz unit) enriched in K (K/Na >1) and oxidized (Fe2O3/FeO >1). It seems that high content of volatiles in high-K and oxygenate magmas occurs due to saturation of magmatic melt in water under a lower degree of quartz-monzonite crystallization immediately preceding Cu-Au±W mineralization at Agh-Daragh intrusive suite. Combining our field geology and geochemical-metallogenic evidences, we conclude that the mineralization in Agh-Daragh area mostly occurred in accompany with late quartz-monzonite stocks; as a result, identification of high-K intrusive rocks and related dikes have important implications for proceeding exploration planning specially indicating of drilling points, and further refines the basis for mineral exploration in Sheyviar Dagh intrusive suite and subsequently in Ahar-Arasbaran metallogenic zone.

The mylonitic granitoids of Gole Gohar, south east of Sirjan, are located in a key area which their study is important for understanding the history of Precambrian basement of Sanandaj- Sirjan zone and its metamorphic and magmatic evolution during the subduction of Neo- Tethys. Field studies show that these granitoids are located in the basement of the metamorphic rocks such as metapelite, calc schist and amphibolite. In this Study the granitoidic intrusions are classified in two types based on lithology and their geochemistry. Type I is garnet- biotite granitoid and type II is hastingsite granitoid. Both of these granites show some evidence of mylonitic fabric, which is more clear in garnet- biotite granitoid. These plutons are Meta aluminous, I Type granitoid and have high K calc-alkaline nature. Based on U-Pb dating of zircon, the age of all granitoids is between 538.6–580.7 Ma (Late Precambrian- Early Cambrian). Based on the results of this study, despite the mineralogical and geochemical differences, all granitoidic intrusions formed in the Precambrian during the Pan African orogeny. The old age of the granitoids is similar to those introduced in other parts of Sanandaj-Sirjan zone that may indicate the presence of Precambrian basement in almost the entire Sanandaj-Sirjan zone.

The Garmab copper deposit is located northeast of Qaen (South Khorasan province) in the1:100,000 scale map of Abiz in the eastern tectonic zone of Iran. It is hosted by Late Paleocene-Eocene lava flows consisting mainly of andesite, trachy andesite, andesite-basalt and basalt lavas, as well as pyroclastic rocks, including tuffs and ignimbrites. The Lut Block has undergone intense magmatic activitywith a variety of geochemical characteristics due to changing tectonic conditions (e.g., compression during subduction followed by tensional conditions; Karimpour et al., 2012; Zarrinkoub et al., 2012). The Lut Block has a great potential for the discovery of new mineral deposits, like the Mahrabad and Khonik porphyry copper-gold deposits (Malekzadeh shafarodi, 2009), the Dehsalam porphyry copper deposit (Arjmandzadeh, 2011), high sulfidation epithermal gold deposits such as Chah Shalghami (Karimpour, 2005) and IOCG deposits such as Kuh-E-Zar and Qaleh Zari (Mazlomi et al., 2008).
After field studies of the Garmab area, 32 thin sections and 21 polished sections were prepared for petrological and mineralogical studies.In addition, 10 least-altered and fractured samples of volcanic rocks were selected for geochemical studies. Major oxides were determined using XRF analyses at the Zarazma laboratory. Induced polarization and resistivity geophysical data were collected and correlated with geological and alteration maps. The geophysical datawere collectedfrom 420 individual points, using a dipole-dipole arrangement along five profiles separated 60m apart.This covered the study area entirely. After a change in the mineralization trend was observed,additional profileswere designed, twoon bearings of 25º and three on 75º.
The Garmab volcanic rocks exhibit typical geochemical characteristics of subduction zone magmas including strong enrichment in LILE and depletion in HFSE. Based on the discrimination plot of Irvine and Baragar (1971), all samples belong to the calc-alkaline series, and based on the TAS diagram of Cox et al., 1979, the volcanic ore host rocks of Garmab range from andesite to basaltic andesite to trachyandesite.
Hydrothermal alteration, associated with deposition of copper sulfide mineralization, occursmostly along the fault zones. .Mineralization also occurs disseminated and as veinlets, restricted to uppermost parts of the volcanic sequences. The deposit has the form of a layer of supergene enrichment characterized principally by chalcocite as the main ore mineral accompanied by digenite, covellite, bornite and chalcopyrite.
The locationof the anomalies has been determined from their medium chargeability and low to medium resistivity values. This can be attributed to the presence of sulfide minerals in the mineralized zones. The average sulfide mineral grain size was determined using the results of time constant parameter. Since the results of raw data do not indicate accurate information about the depth and geometry of mineralization, smooth inverse modeling was applied to determine probable zones and vertical and horizontal extension of mineralization.Geophysical studies show that zones of mineralization are small and scattered.

Gabbroic stocks and dykes associated with Ophiolitic Basalts and peridotites are outcropped in the Sawlava town area. Sawlava ophiolite is part of Kurdistan Ophiolitic complex that located in sheared zone between high Zagros and northern Sanandaj-sirjan Zone. This study focused geochemistry and dating of granular and pegmatoid gabbros that due to closing to main recent fault (MRF) some part of them found milonitic fabric. Gabbros have 47. 84 to 51. 65 percent SiO2 and almost formed from tholeiitic magma. Labradorite plagioclase and diopside and augite clinopyroxens with Mg# of 83. 90 to 88. 90 respectivly are main minerals of gabbros. Based on geochemical and geotectonic diagrams، gabbros generated from slightly deplete magma which formed in back arc supra-subduction zone. U-Pb dating of zircons presents an average age of 38. 3±1. 3 Ma for gabbros. Late Eocene age from Sawlava gabbros and similar gabbros bodies related to ophiolites along Zagros suture، could indicate that neo-tethyan ocean closed after Eocene in the Kurdistan region.

Zagros ophiolites are mainly exposed in Oman، Neyriz، Kermanshah، Kurdistan and north western of Iraq. The Sawlava ophiolitic complex is a member of Kurdistan ophiolites. In this research petrogenesis and geodynamic of this part of Zagros ophiolites have been investigated. Basalt، microgabbro، gabbro with serpentinized dunite and wherlite are the main rock units of the complex. The phenocryst in the basalta and the microgabbros are plagioclase and clinopyroxene and the main textures in the basalts are porphyric and microlitic-glassy whereas intersertal and microgranular are dominant in the microgabbros. The main minerals in the gabbros are clinopyroxene (augite-diopside)، plagioclase with labrador composition. In the peridotites، the major minerals are olivine (Fo= 88-91)، clinopyroxene (diopside-clinoenstatite) and chromin spinels (picotite). By analogy with the global standards، the obtained geochemical data reveal that basalts and microgabbros in Sawlava ophiolitic complex are tholeiitic in nature، and their magma source tends towards N-MORB and E-MORB. Gabbros are in tholeiite to calc-alkaline magma series and show the abyssal MORB to oceanic ARC features. The chemistry of peridotites shows the abyssal to supra-subduction zone source. The high volume of basalt-microgabbro، low Ti value and high content of Al and Cr# in peridoitite chromian spinels، reveal a high rate of partial melting (25-35%) indicating that the depleted mantle subjected to high degree of partial melting can be the Sawlava complex source. According to geochemical data a depleted mantle may be the source of Sawlava ophiolitic complex. This feature is more remarkable in the studied gabbros and peridotites. Comparing the lithological and geochemical characteristics of the studied ophiolites with some other complexes in the world documented that the complex under discussion formed in an oceanic back arc setting.

In the northern hillside of Central Alborz, south of Kamarbon village, there is an outcrop of alkaline gabbroic intrusion that its petrogenesis and tectonic environment have been studied in this research. The studied intrusion has fine grained theralite in the margins whichconverted to coarse grained teschenite toward the center. The Mg number is decreased from theralite towards teschenite. The occurrence of theralites in the fine grained margin can reveal early crystallization of the margins due to rapid fall of temperature. The studied rocks on the spider diagrams show the enrichment of LILE (Rb, Ba) and HFSE (Nb) and the depletion of P, K, HREE (Y, Yb). These trends are similar to those of interacontinental alkaline rocks. Low values (less than 1) of HFSE/LREE can represent the astenospheric mantle as the source of magma. The YbN<10, high values of (La/Yb)N (19.98-28.41) and high values of (Dy/Yb)N (1.39-1.68) may indicate the presence of garnet as residual phase in the mantle source of the magma that generated the Kamarbon gabbroic alkaline rocks. In gabbro classification diagrams, the studied rocks are located in the field of interacontinental rift gabbros. The development of this gabbroic intrusion can be related to the plutonism of interacontinental rift that had been activated in late Triassic time in Central Alborz.