Iranian Journal of Crystallography and Mineralogy
Year:2005 | Volume:13 | Issue:1 |Papers Count:16

Eastern Birjand ophiolitic complex consist of different rock types of a complete ophiolitic sequence. Three groups of amphiboles which exist in metabasites of this ophiolitic complex are of: calcic amphiboles, such as actinolite-tremolite and magnesio-hornblende; calcic-sodic amphiboles, e.g. vinchite and barroisite; and sodic-amphiboles, e.g., glaucophane, magnesio-riebeckite and ferro-glaucophane. Petrographic studies, geothermobarometry results and composition of minerals, especially amphiboles in mineral assemblage of different metamorphic rocks clearly indicate pressure-temperature variations of metabasites within different evolutionary stages. This indicates that subduction and subsequent thrusting are occurred in the studied area.

In this research N(2-chloro-phenyl)4-nitro-thiobenzamide as a ligand was synthesized. One mmol of mercury oxide was added to the solution of 1 mmol ligand in 45 ml chloroform and after 90 min the mixture through celite or BaS to remove unreacted mercury (II) compounds. The yellow crystals, which formed by slow evaporization, was separated and recrystallized from chloroform as fine yellow crystals with 87% yield and dried in vacuo. The crystal structure of above complex was determined by single crystal X-ray diffraction method. The complex crystals in a monoclinic unit cell with a = 8.2822(9)A°, b = 12.2907(9) A°, c = 13.1243(13) A° a=90°, B = 98.729(5)°, g = 90° and Z = 2 and space group P21/c. The S-Hg-S is linear with angle of 180°.

Two types of tungsten mineralization have been recognized in southwest of Astaneh: 1. Stratabound type at Bamsar with calcareous schists and siliceous tuffs as host rocks, 2. Quartz-tourmaline vein type at Nezamabad, Revesht and Fizaneh hosted in quartzdiorite-granodiorite intrusions. Scheelite is the main tungsten ore mineral in both types. Generally, two distinct REEN patterns are observed in the scheelites from the region: Nezamabad, Revesht and Fizaneh patterns have a convex feature varying from Eu-free to highly negative Eu anomaly, having high Na and SREE contents. The samples are enriched in HREE. Bamsar type REEN pattern has lower SREE and Na, a relatively flat feature and small to large positive Eu anomalies. The samples are enriched in LREE. According to the REE trends, presence of high-temperature minerals, exsolution textures, presence of organic and graphitic parts, the two types of mineralization share a high temperature and reducing environment, but some differences lie in REE controlling processes. Surface absorption at Bamsar and mixing of complexes mechanism at Nezamabad, Revesht and Fizaneh control the REE patterns. Therefore, it can be concluded that the origin of REE in scheelites in the mineralized areas of Bamsar, Nezamabad, Revesht and Fizaneh share the same source and the differences in SREE result from the influence of host rocks in the areas with vein-type mineralization.

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 XGras 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.

In Khoy ophiolitic massif (NW of Iran) three types of quartzite and also quartz bearing veins can be distinguished: massive quartzite, quartz bearing veins in the amphibolites and siliceous veins in the radiolarian cherts. Massive quartzites contain quartz porphyroclasts associated with very   small- deformed quartz neoblasts. These quartzites are deformed in regime I and recrystallized as grains bulging. Siliceous veins in the cherts have Cu-carbonate impregnations in the field. Very large grains of quartz with well-developed triple point junctions can be distinguished in thin section. Their pattern of c-axes distributions doesn’t show any special orientation.  The pattern of c-axes distributions in the quartz bearing veins in the amphibolites is consistent with prism and rhomb slip system along <a> direction. Water in these veins is at the origin of soluble structures and precipitation of clay minerals. SEM analysis on the soluble fovea as the result of water operation has revealed high amount of water.

The Late-Eocene, Early-Oligocene Zahedan granitic rocks are intruded the felysch zone of the east Iran. They are mainly granodiorite, I-type and calc-alkaline. F and Cl contents in biotite from the Zahedan granitic rocks range from 0. 1 to 0.66 and 0.01 to 0.09 wt. %, respectively.  F contents in the biotites are negatively correlated with XTi and Cl contents and positively are correlated with XSi and Mg/(Mg + Fe). Values of the calculated log(ƒH2O/ƒHF) and log(ƒH2O/ƒHCl) of fluid in equilibrium with the chemical composition of biotite range from 3.98 to 4.90 and 1.41 to 2.63, respectively. The contour lines representing these values are different with slope of trend of biotite composition suggesting, the fluid composition also play some role in incorporation of F in biotite in addition to the chemical structure of biotite. IV (F) for biotites in the Zahedan granitic rocks is similar to those of igneous rocks and porphyry Cu ore deposits and IV (Cl) of biotites in the Zahedan granitic rocks is similar to those of hydrothermal and ore forming systems and those of granitic rocks.  Based on the IV (Cl), biotites from the Zahedan granitic rocks tend to be more Cl rich than comparable values from biotites in other granitic rocks and less Cl rich than those of porphyry Cu ore deposits. Calculated IV (F/Cl) of biotites from the Zahedan granitic rocks is more similar to ore-forming systems such as porphyry Cu ore deposits. Therefore, the chemical composition of biotites from the Zahedan granitic rocks was interacted with hydrothermal solutions.

Granitoid bodies of  south of Damghan with northeast-  southwest trend have intruded into the  Eocene volcanic,volcanoclastic and Cretaceous carbonate deposits. Recent studies have revealed that the Al content of hornblende in calc-alkaline granitoids varies linearly with pressure of crystallization, thereby providing a mean of determining depth of pluton emplacement. Based on results of electron microprobe analyses, amphibole minerals present in these bodies, according to Leake are ploted in the field of calcic amphiboles and show Actinolite, Actinolite-Hornblende and Magnesio hornblende composition. Calculated pressures of emplacement , using the Al-content of Hornblende, for these bodies ranging from about 0.51 to 0.98 Kbar (about depth of 1.8 to 3.5 Km).The altimate equilibration temperatures of minerals were calculated using different thermometers ranging from 613 to 772 oC.

Adsorption, storage and release of nutrient elements are related to clay minerals in agriculture and environmental activities. In this study, mineralogy of soils in a chronosequence of Sefidrud river terraces in Gilan province was investigated. After removing organic matters, carbonates and iron and aluminum oxides, fractionation of soil particles was performed by centrifuge. Soil minerals were identified using X-ray diffraction. Primary minerals were also identified in thin sections using micro-morphological techniques. Quartz, micas, feldspars, chlorite and epidote were the primary minerals observed in sand and coarse silt fraction. Chlorite was transformed to smectite, hydroxy interlayer smectite and other mixed minerals. In the middle terrace (T2) soil, chlorite is completely disappeared but the relative amount of smectite is increased. With time smectite becomes dominant in clay particles, specially fine clay size. Smectite was increased with depth in Bt horizon on middle and upper terraces. Three different methods were tested to remove hydroxy interlayers from 2:1 clays, but only one of these methods which consisted of washing coarse clay fraction by 0.05 M HCl, heating to 400°C and finally boiling it in 0.5 M NaOH was able to remove hydroxy interlayer. The results showed this mineral is primarily hydroxy interlayer smectite (HIS).

The studied area is a part of Tarom Mountains and is located in 40 km north of Zanjan. The area is formed mainly by Tertiary volcano-sedimentary and plutonic rocks, which are mostly altered. Based upon geological setting, the hydrothermal alterations in the area are divided into two groups: (1) Regional alterations consisting of potassic, sericitic and propylitic types. (2) Structurally controlled alterations consisting of three argillic & alunitic types. The mineralogical studies show that, the major minerals characterizing the argillic – alunitic alterations are APS minerals (especially alunite and jarosite) + clay minerals (kaolinite, montmorillonite, illite, mixed–layer illite/smectite) + chlorite + sericite + quartz + gypsum + pyrite, that their quantity, grain size and crystallinity vary in the different alteration types. In order to determine the temperature of argillization, the illite crystallinity factor is used and the results of calculations showed that the formation temperature of illites is about 200 to 240 oC. The results of this study indicate that the argillic-alunitic alterations of studied area considerably resemble high-sulfidation type of the epithermal argillic alterations in the continental arc subduction zones.

Colorless sodic and sodic-calcic amphiboles occur in piemontite-quartz schists in the Asemi-gawa (garnet zone) and Besshi (albite-biotite zone) areas of high P-low T Sanbagawa metamorphic belt in central Shikoku, Japan. Colorless sodic amphiboles in the Asemi-gawa area are glaucophane while colorless sodic-calcic amphiboles from the Besshi area are barroisite and magnesiokatophorite. Colorless sodic and sodic-calcic amphiboles are richer in Mg and poorer in Fe in comparison with the colored sodic and sodic-calcic amphiboles from the epidote-quartz schists of the same metamorphic grade. Optical characters of the glaucophanes from the Asemi-gawa area are identified by their colorless and lack of pleochroism in the a, b and g directions; ng ^ Z = 13, 2V(a) = 20 and b = Y. Optical characters of magnesiokatophorite from the Besshi area are: colorless and without pleochroism in the a, b and γ directions; ng ^ Z =17, 2V(a) = 25 and b=Y. Chemical composition of the coexisting minerals with colorless sodic and sodic-calcic amphiboles have shown a very high oxygen fugacity condition in which iron exists only as Fe3+ and occurs mostly in hematite.  Therefore, such condition was responsible for formation of sodic and sodic-calcic amphiboles which are very rich in Mg.

The structural of Haft Tapph’s cuneiform were studied by XRD and thermal methods. Complementary chemical analysis showed that cuneiform were made of marl. The studied of thermal behavior of cuneiform tablets by STA indicated very valuable treatment of cuneiform tablets by firing.

The Qaleh-Zari specularite- rich Cu-Au-Ag deposit is located 180 Km south of Birjand. Host rocks are mainly Tertiary andesites and andesitic basalts and some Jurassic shales and sandstones. Andesitic rocks from the western region of Qaleh-Zari were dated to 40.5±2 Ma. Four trends of faults and joints are identified in the mine area.  The oldest is mineralized. Three major sub-parallel quartz veins are present. No. 2 vein is the main vein and can be traced for more than 3.5 km along strike (N40°W) and more than 350 m down dip. Paragenesis: Stage I: specularite, quartz, Fe-chlorite, chalcopyrite and sulfosalts. Specularite deposited first and forms 10 to 25 percent of the vein. Ore grade is 2 to 9% Cu, Ag 100 to 650 ppm, and Au 0.5 to 35 ppm. Propylitic alteration is dominant and epidote is very abundant. Argillic alteration is locally present. Silicification is mainly found within the vein zone. Temperature of homogenization of primary fluid inclusions in quartz associated with specularite and Cu, Ag, and Au mineralization was between 240°C and 360°C. The salinity of ore fluid was between 1.0 and 6.0 wt% equiv. NaCl and the CO2 was < 0.1 mole%. Based on the presence of hematite, chalcopyrite, Fe-rich chlorite, and, locally pyrite, and on the absence of magnetite and pyrrhotite, the ore fluid was very oxidizing. Some important differences between Qaleh-Zari and other iron-Oxides Cu-Au deposits are: (1) The salinity is very low (< 6 wt% NaCl equiv.), (2) absence of magnetite and apatite, (3) low REE and P., and 4) high grade Cu, Ag, and Au. Differences in the amount of Cu, Au, REE, P, U, F and some other elementals in iron-oxides Cu-Au deposits are related to: Tectonic setting, depth of magmatism, source of magma, degree of partial melting, physicochemical condition of melting, rate of ascending, crystal assimilation, degree of fractionation, and depth of emplacement.

The reaction of gallium (III) nitrate octahydrate with the proton transfer compound (pydaH2)2+ (pydc)2– ( where pyda  is 2,6-pyridinediamine and pydcH2 is 2,6-pyridinedicarboxylic acid) leads to the formation of (C5H8N3) [Ga(C7H3NO4)2]. 4H2O· CH3OH. The crystal system of the anionic complex is triclinic with space group Pi and two molecules per unit cell. The unit cell parameters are a=10.238(2) A, b=10.428(2) A, c=13.838(2) A, a =70.375(3)°, b=77.938(3)°, g=64.120(3)°. The structure has been refined to a final value for the crystallographic R factor of 0.0579 based on 4703 reflections with I > 2s(I).

The study of morphological and mineralogical changes within a natural acid saline seep affected landscape revealed that seasonal differences in surface mineralogy, reflecting the operation of sulfidization and oxidative sulfide weathering processes. During the wet season, the surface and near surface of the waterlogged seep and marsh areas is dominated by black sulfidic materials (pyrite) and minor salt crusts, with negligible iron oxides and oxyhydroxides. The Fe and S emerging from seeps contribute to the sulfidization processes operative in reducing conditions within the waterlogged zones. During the dry season, the surface mineralogy of the natural seepage zone is dominated by salts (halite), sulfates (gypsum and barite) and importantly, iron oxyhydroxides gel precipitates and crusts (ferrihydrite, goethite, schwertmannite). The gradual drying of previously waterlogged zones during summer facilitates oxidative weathering of the sulfides, which together with rapid oxidation of Fe2+ emerging from the still persisting minor seeps, results in the formation of iron oxyhydroxides and acid generation. The visible near infra-red (VNIR) reflectance spectra of the surface minerals from unaffected, salt crusted and acid seep areas, showed spectral differences expressed in the VNIR region due to absorption bands of iron oxides and hydroxides. The spectral difference can be utilized for regional scale mapping of acid seeps and acid sulfate soils of affected areas via hyperspectral and multispectral remote sensing.