Iranian Journal of Crystallography and Mineralogy
Year:2006 | Volume:13 | Issue:2|Papers Count:20

The studied volcanic alkaline rocks with 32.7±6 Ma years age are croped out along the south - east of Urumiyeh- Dokhtar Volcanic Beltin Kerman province. Based on the TAS classification these rocks are divided in to tephriphonolite and phonolite which belong to high-K alkaline rocks. These rocks are composed of pyroxene, plagioclase, sanidine, nepheline, analcime and titanomagnetite minerals. Diopside is the only pyroxene identified in the study area. In the most of the phenocrysts the amount of MgO in the core is more than the rims while the amount of FeO is high in the rims. This trend shows a normal fractionation during magmatic evolution. The composition of pyroxene phenocrysts is from WO47.8 En38.8 FS13.4 to WO45.6 En35.7 FS18.8-Sanidine is the only K-feldspar present in these rocks and has a composition ranges from Or62.7to Or93.8 Most of the plagioclase phenocrysts have Ca-rich cores and more Na-rich rims which is attributed to normal magmatic fractionation. The composition range of plagioclase is An5o.83 to An59.2. Trapezohedrs of analcime comprise up to 40% of the rocks and the composition of the analcime trapezohedrs are remarkably homogeneous. The analcime is interpreted as having formed by ion-exchange pseudomorphous replacement of primary leucite, either during cooling of the lava or shortly afterwards. Titanomagnetite is a very common equant grain in groundmass of all the studied samples. The Fe-Ti oxide crystals are relatively Ti-rich and are classified as titan magnetite.

The Ham Formation (Santonian-Campanian) is a unit of Bangestan Group, which is overlain on the Sarvak Formation in Tang E-Rashid area, Peyon Anticline (18.5 Km North of Izeh). Due to similar lithology, recognition of the exact boundary between Ham and Sarvak Formations in the study area was difficult. Thus it is not possible to determine boundary between these two formations based on petrographic evidence and field observations. Recognition of original carbonate mineralogy based on petrographic studies is difficult in ancient carbonate rocks, because aragonite (A) and high -Mg calcite (HMC) transformed to low Mg calcite (LMC) during digenesis. In this study major and minor elements and carbon and oxygen isotopes values used to determine the original carbonate mineralogy of Ham Formation in the Peyon Anticline.  Bivariet plots of minor and major elements and oxygen and carbon isotopes values indicate that original carbonate mineralogy was aragonite in Ham Formation. Elemental and isotopic compositions of Ham carbonates also illustrate that they were affected by non-marine digenesis in a closed system. Major and minor element variations (such as Sr, Sr/Ca, and Sr/Na) and oxygen and carbon isotopes were used to distinguish the boundary between Ilam and Sarvak Formations in the Peyon Anticline.

The quartz-aluminosilicate veins in the Hamadan region consist of quartz with one, two or three polymorphs of aluminum silicate (andalusite, kyanite and sillimanite). In some veins other accessory minerals (Le. garnet, chlorite, muscovite, staurolite, biotite and plagioclase) are present. The petrogenesis of these veins and their country rocks have been previously described; this paper studies oxygen isotope ratios of co-existing quartz and Al2SiO5 to determine formation conditions and genesis of these veins. The δ 18O/ 16O values of quartz, andalusite, kyanite and sillimanite range from: + (16.8-17.1)‰,+(14.2-14.5) ‰, +14.1‰ and +14.6‰, respectively. These results indicate a possible metamorphic origin for fluids responsible for the formation of these veins and magmatic origin of fluids is unlikely. The estimate temperature for the formation of veins is about ~ 480-550 ˚C, a range that consistent with petrographic observations in the veins and previous thermometry results on host rocks of veins.

Abstract: Siliciclastic sediments of the Cheleken Series (Lower to Middle Pliocene) are exposed along the northern flank of Elburz Mountain Range. The goal of this study is to identify the clay mineral type in these siliciclastic sediments in Mazandaran and Golestan regions, because this can help in the prediction of drilling mud type that can be used. 23 samples have been collected from Neka, south of Ghaem Shahr and Alamdeh regions. Petrographic and XRD analysis revealed that sandy siliciclastic sediments with conglomerate interbeds are mainly consists of quartz, calcite and clay minerals. Illite and kaolinite is the major and monmorilonite and chlorite are the minor clay minerals in these sediments. Based on these types of clay minerals in study area, we suggest that the best drilling mud for using in these sediments are salt/polymer water - based mud with a suitable amount of potassium salts. Because these materials are available in Iran and they are relatively less expensive as well as potassium with low ionic diameter has the least problems during cation exchange in clay minerals that present in cheleken series.

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 Pmax was not contemporaneous with Tmax during eclogite facies metamorphism of the metabasites from North of Shahrekord, in Sanandaj - Sirjan Zone.

Trachyandesitic rocks in the Ab-e-Torsh region, western Qazvin, have considerable thickness and extensive outcrops (>200 Km2) that form parts of the Alborz Paleogene volcanic belt. These rocks that can be correlated with the upper member of the Karaj formation, are subaerial eruptions with lava flows and some lava domes. Geochemically, these are classified as shoshonitic .series. Occurrence of some textural evidences (e.g., reaction rims, sieve textures and oscillatory zoning in feldspars and augites phenocrysts) and coexistence of inequilibrium plagioclase phonocrysts (An5-20, An36-61, An77-93), as well as compositional differences between phenocrysts and their surrounded mesostasis, all suggest that the magmatic evolutionary processes could have been occurred in an open system. On the other hand, existence of some alterations such as opacitization in phlogopitic biotites and paragasitic hornblends might be related to the late stages of the magmatic evolution with high 102 and PH20.Considering textural and mineralogical observations, as well as dispersion of the whole rock geochemical data, one may conclude that the magmatic evolution have been occurred by periodic refreshment of alkaline and basic magma by a more acidic intrusion.

KC5 copper exploration prospect is located 80 Km to the northwest of Bardaskan and 4 Km to the Northeast of Dahaneh Siah copper mine in Khorasan Razavi. KC5 and Dahaneh Siah areas belong to Sabzevar geological Zone. Copper mineralization is observable mainly as secondary minerals such as Malachite and Chlorite which fills joints and fractures in a faulty contact at the boundary of the volcanic and Oriyan sedimentary (carbonaceous and tuff) rocks. High intensity ellipsoidal aeromagnetic anomaly overlies the boundary between the volcanic and carbonaceous rocks which follows old abandoned copper mines and extends to the KC5 prospect and Dahaneh Siyah area. Studies indicate the presence of magnetite up to maximum.5% in the volcanic rocks. Magnetic susceptibilities of the volcanic rocks in the KC5 west; KC5 east and Dahaneh Siyah show that this parameter is 2 times smaller in the first area than in the second and third. Magnetic anomalies of the two volcanic units in the KC5 east are similar but their amplitudes are lower than the anomalies produced by the same units in the KC5 west. Anomaly amplitudes of the Dahaneh Siyah volcanic are smaller than those produced by the same volcanic unit in the KC5 west and east. Lower magnetic susceptibilities of surface volcanic samples in the KC5 west and their higher amplitude anomalies in comparison with the anomalies from similar volcanic units in the KC5 east and Dahaneh Siyah implies that the source of the anomaly and main mineralization at KC5 west must be deep. Correlation of aeromagnetic anomaly with old abandoned copper mine (including the Dahaneh Siyah copper mine and the KC5 prospect area), uuper boundary of the volcanic and carbonaceous sediment and geochemical anomaly of the region are indications of the relation of main mineralization with aeromagnetic anomaly.

Abstract: In this paper, results from X-ray diffraction and the variation of electric resistance versus temperature of Gd3AuxAl1-x intermetallic compound are reported. All samples formed in orthorhombic crystalline structure with Pnma space group. In measuring the lattice parameters by X-ray diffraction method, deviation from Vegard's rule has been seen. This deviation at x = 0.4 maximizes. In addition, an abrupt volume change equal to 6% occurs at the critical point x = 0.4. For all samples, by increasing the x-parameter, we have seen increasing in the Curie temperature Tc. Magnetic susceptibility Х(T) is increased versus x-parameter, too. The results of electric resistance measuring in sample with critical value (x = 0.4) shows a behavior like Kondo effect which is not observed in other samples. For compounds based on Gd, this undesirable behavior could be related to 4f sublevel which it concentrates free electrons around Gd ion.  

In this research fly ash (FA) from Iran Ferrosilice Company was converted to zeolite A by hydrothermal procedure. The type and quality of produced zeolite depends on the composition of used FA, concentration of sodium hydroxide solution, and parameters such as temperature, reaction time and liquid/solid ratio. The fly as4 was fused with sodium hydroxide at 550°C for I hour followed by dissolution in water and hydrothermal treatment. It was found that the solutions of fused powders can be occurred at 90°C under hydrothermal condition to precipitate zeolite A. In order to evaluate its ion exchange properties, cation exchange capacity (CEC) of the synthesized zeolite A were also measured.

Hardness of a mineral is one of its important physical properties and several methods have been presented for its determination. Mohs hardness determination is the most versatile method by which the mineral hardness is determined somewhat qualitatively with respect to another mineral and has no unit. In this paper, because of the need to measure the mineral hardness more accurately and give a meaningful unit to it, a new method is proposed to determine the mineral hardness based on its other related physical properties. In the proposed method the coefficient of friction is taken as the base, where the effects of other related factors like temperature, normal force, surface hardness, velocity and its direction are considered and then the direct and inverse relations of these factors on the coefficient of friction are discussed. The new method (which is called as FH (Frictional Hardness) method) is also compared with the three existing methods i.e. Mohs hardness, Rockwell hardness (R) and Penetration hardness (p). The main advantages of the FH method are: (i) Hardness has a specific unit and dimension, (ii) The hardness of different minerals can be determined accurately so that they can be distinguished from each other in a better way, and (iii) A lot of minerals in which their hardness are very close to each other will not have equal hardness. Maximum temperature which is an important factor in FH hardness can be obtained through equations of heat and energy or it can be measured by a thermocouple.

Tanbour metamorphic complex east of Sirjan is compoused of metasediments and metabasic rocks. Petrofabric study of this complex shows two metamorphic and two deformational phases. Chemical studies of index minerals indicate that second phase of metamorphism occurred with a degree up to lower amphibolite facies. Mineral assemblage of first phase are biotite, muscovite and garnet while staurolite appears in peak of second phase of metamorphism. Mineral chemistry studies indicate that second phase of metamorphism occurred up to staurolite zone. Tempretures and pressures about 550-590°C and 7-8/48 kb were also estimated using geothermobarometry. The data suggest that these metamorphic rocks underwent a medium P metamorphic event.

On the basis of mineralogy and geochemistry analysis, the listvenites in east of Iran are divided into three main carbonate, silica carbonate and silica groups. Magnesite, dotomite, huntite and hydromagnesite are the major minerals in carbonate type. Silica listvenites contain mainly quartz, chalcedony and opal. Silica - carbonate listvenites contain minerals of carbonate and silica listvenites. The common structures in listvenites are vein and brecciaed type and the main textures are open space filling and colloidal. Mass balance consideration in listvenites and their host serpentinized ultramafic show that all the elements are loosed in ultramafic, are gained in listvenites. Nehbandan fault activity in east of Iran, produces suitable conduits for penetrating the meteoric water into deep levels, increase its temperature and solubility and then alteration the ultramafic unit of colored melange during its path. Hydrothermal fluid flow-up through shear zones and wash the rocks during the path, and then under suitable condition of Eh and pH at the surface or low level open spaces of the earth, deposit its load as different types of listvenites.

Abstract: In the upper Proterozoic Anarak ophiolite, the marbles are present and havr excellent exposures in different areas. Their best exposure is in southern slope of Chah-Gorbeh mountain (Chah-Mahdi valley). In the field, marbles have massive and dike like exposures. Petrographic studies and geochemistry of minerals show that marbles consist of carbonate (calcite), gamet (andradite), clinopyroxene (diopside and magnesian-augite), amphibole (tremolite), serpentine, chlorite, epidote, chromian spinel, magnetite and chromian-magnetite, that are alteration products of chromian spinet. Field and microscopic studies show that the marbles have been produced by regional metamorphism of old listvenites at different phases of metamorphism. The protoliths of these metamorphosed listvenites were ultrabasic dikes and intrusions, and mantle peridotites. Presence of serpentine, relic chromian spinel, magnetite and chromian magnetite that have changed to garnet, supports this interpretation. Therefore, the marbles of Anarak ophiolite, are productions of regional metamorphism of old listvenites.

The first crystal structure of a phenylcyanamide Rh (III) complex, [Rh (terpy) (bpy) (2,5-Cl2pcyd)] (PF6)2 (terpy = 2,2':6',2"- terpyridine, bpy= 2,2' -bipyridine, and 2,5-Cl2pcyd = 2,5-dichlorophenylcyanamide) has been reported in this paper. Crystals of [Rh (terpy) (bpy) (2,5-Cl2pcyd)] (PF6)2 .0.5CH3CN were grown by ether diffusion into an acetonitrile solution of the complex. Crystal structure data: orthorhombic system, space group Fdd2, with a = 84.228(3), b = 8.7162(3), c = 21.4921(7)Å, V=15778.4(9) Å3, and Z=16. The structure was refined by using 4971 independent reflections with I>2σ(I) to a R factor of 0.0644 and Rw= 0.1752. ORTEP drawing of [Rh (terpy) (bpy) (2,5-Cl2pcyd)] (PF6)2 .0.5CH3CN shows that the terpy and bpy ligands are coordinated to the RhIII through their nitrogen atoms in a mutually perpendicular fashion. The anionic cyanamide group is coordinated end-on by the nitrile nitrogen to the RhIII. The RhIII-NCN bond is bent, having an angle of 125.4°. This bent bond is largely determined by the σ-bonding interaction of a cyanamide non-bonding electron pair in a Sp2 hybrid orbital.

The Dinuclear Cu (II) complex [{CuCl}2(µ- tppz)](PF6)2, where tppz represents tetra-2-pyridinylpyrazine, has been prepared and characterized by elemental analysis, H-NMR, IR and UV-vis spectroscopies. A crystal structure of the complex showed the Cu (II) are surrounded by three N atoms of tppz bridging ligand and one Cl atom. Crystal structure data are as follows: crystal system monoclinic, space group C2/m, a= 13.314(3), b= 12.901(2), c= 8.9039(17) Å, β= 99.260°, V=1509.4(5) Å3 and 2=2. The structure was refined to a final R factor of 0.0416. The crystal structure revealed that the Cu(II) are respectively above and below the plane of the pyrazine moiety of the bridging tppz ligand with the pyridine moieties moving out of the pyrazine plane in order to coordinate to Cu(II). Each chloride ligand bonds equatorially to Cu (II) in a [{CuCl}2(µ-tppz)]2+ ion and axially to a neighboring [{CuCl}2(µ-tppz)]2+ ion so as to form a one-dimensional chain in the solid state.

Thermal behavior of the Shahreza dolomite ore is investigated in this paper. The hydration of the calcined dolomite was studied as a function of the calcination temperature. The DTA results exhibit three endothermic peaks at 800, 900 and 1050˚C, corresponding to decomposition of MgCO3 and CaCO3, both are present in dolomite and free calcite, respectively. The results also indicated that the degree of calcination is increased by increasing the calcination temperature from 800 to 1400 cc. As the calcining temperature increases from 800 to 900°C, the hydration degree of the dolime increases too because of more humid absorbing phases produced at higher temperature. However, the hydration degree declines with further increase in the calcination temperature and became negligible when the sample is calcined at 1400°Cprobably due to the sintering process occurred at elevated temperatures.

Qaleh-Zari specularite-rich Cu-Ag-Au deposit is located 180 Km south of Birjand, in eastern Iran. Host rocks are mainly Tertiary calc-alkaline to K-rich calc-alkaline of 40.5±2 Ma and Jurassic sandstones and shales. Three major sub-parallel steep quartz veins are identified in different rock types, in particular andesitic rocks. The Qaleh-Zari deposit is a specularite-rich hydrothermal, Cu-Ag-Au vein type deposit. Several complex Cu-Pb-Bi and Ag- Pb-Bi sulfosalt minerals have been identified in samples from different vein mineralization. Based on the paragenesis and fluid inclusion data temperature of homogenization, four ore-forming stages are identified in the area. In the first stage, specularite, chlorite, chalcopyrite and Bi-sulfosalts, (aikinite, matildite and wittichinite) were formed. The temperature of the homogenization of the fluid inclusions for the first stage ranges as 380 to 290°C. In the second stage, pyrite, chalcopyrite, chlorite, aikinite, cosalite, wittichinite and bismuthinite-aikinite were deposited. Homogenization temperature of fluid inclusions for the second stage of the mineralization are between 290 and 230°C. Within the third and fourth stages of the mineralization, specularite, quartz, calcite, pyrite, Ag-bearing aikinite, and an unknown Ag-sulfosalt were formed. The homogenization temperature for this stage ranges between 250 and 180°C. The unknown Ag-rich sulfosalts and arcubisite have the highest Te, As, st, and Se contents. The salinity of ore fluid was between 1.0 and 6.0 Wt% equiv. NaCl and the CO2 was < 0.1 mole%. Based on mineral paragenesis, the fluid was very oxidizing with a log £02 between -13 and -28 (assuming a temperature of 300°C).