مجله بلور شناسی و کانی شناسی ایران
سال یازدهم شماره 1 (پیاپی 21، بهار و تابستان 1382)

Montmorillonite is the main bentonite forming mineral which has special characteristics such as suspension, swelling and colloidal properties. It can absorb water to become larger in volume.Good absorbents are extensively used in industry eithersimply dried or after chemical activation. The chiefconsumer of these clays is the oil refinering industry whichuses them to purify fractionation products of suspendedmatter and as drilling muds.This study on bentonite shows that mineralogicalcomposition and concetration of Al2O3, MgO in montmorillonite are the most important characteristics forchemical activation of bentonite.In addition to above factors, the temperature, acidconcentration and time are also considered for activation.

Mineralogy and chemical composition of Deh Mohammad, Shirgesht, Chah Cam-1 and Chah Cam-2 bentonite deposits were studied in detail. Tests for foundry moulds uses carried out on raw and processed. Deh Mohammad with 300000 tons reserve is the biggest deposit. Deh Mohammad consists of 75 – 95% montmorillonite, 5 - 25% cristobalite, 0 -3% calcite, and less than 1.5% halite. The colloidal index for raw bentonite (24 hour) is 20 – 30. Based on chemical composition, Deh Mohammad is Na-bentonite and is good for foundry moulds. Shirgesht has about 135000 ton bentonite. It contains of 74 – 92% montmorillonite, 8 - 28% cristobalite, 3 - 10% calcite, and 0 - 1.5% halite. The colloidal index for raw bentonite (24 hour) is 14 - 22. Based on chemical composition, Deh Mohammad is Na-bentonite and in most part is good for foundry moulds. The bentonite reserve at Chah Cam 1 and 2 mines are 73000 and 62500 ton 60 - 80% montmorillonite, 15 – 35 % quartz- cristobalite, 1 - 5% calcite, and 1 - 5% Halite. The colloidal index for raw bentonite (24 hour) is 0 - 20. Based on chemical composition, Deh Mohammad is Na-bentonite. The colloidal index of some samples are good for foundry use but high halite content is a problem, therefore this bentonite must be mixed with a bentonite having low or no halite such as Shirgesht.

Identification of randomly interstratified illite – smectite, the most abundant of the mixed-layer clay minerals, is occasionally difficult. The so-called magnesium chloride and ethylene glycol treatment does not always reveal all the peaks necessary for identification of these clay minerals. Therefore a new modality, lithium chloride treatment, is suggested. With the application of this treatment, the characteristic peaks related to the mixed-layer as well as smectite will appear clearly. So, the illite proportion in the mixed-layer can be determined easily.

In this research the Fourier transform of electric field in a three-layered model with thickness tj and dielectric rj is computed, after solving three dimensional Laplace equation for Fourier transform of potential under suitable boundary conditions.Then, by studying the behavior of spread function, a three-layered photoreceptor is designed. After designing and constructing of all of the subsystems, the depostion of Al and formation of Al2O3 are carried out at 210-5 to 510-7 mbar pressure. Then coating of Se is carried out under 210-7 mbar pressure, 250 C boat temperature and 95C substrate temperature in 120 min. Electrical resistance of the prepared sample was measured to be higher than 1012  in dark and about zero in than light, this values are suitable for making electrostatic latent image. To test its function in practice, the sample was mounted in Xerox machine and images were copied successfully.

The mineralogical composition of soils formed on phyllite and alluvium as well as examination of their mineral weathering characteristics should provide an insight into the stage of weathering. Three soil profiles from mountain, plain and low lands were selected. Based on XRD analysis, clay fractions were dominated by chlorite–vermiculite, vermiculite, HIV, illite, mica–vermiculite or mica-smectite. Persistance of 13.9 Å peak on 550 °C treated specimens indicate discrete chlorite, however, presence of 12.2 Å peak on 550 °C pattern, further suggesting partial, random removal of interlayer hydroxide sheets and then, interstratified chlorite-vermiculite formation. Therefore, decrease in chlorite and illite is accompanied by increasing vermiculite in surface horizon. Higher intensity of even-ordered reflections (002,004) than odd ordered reflections (001,003) in chlorites revealed the presence of iron ions which further increased the susceptibility of them to chemical weathering through oxidation process and caused to degrade the interlayer sheets. The shoulder on the low angle side of 10 Å peak upon 550 °C pattern and on the high angle side of 14 Å peak under glycol solvation as well as gradual decrease in 14 Å peak intensity and gradual enhancement in 10 Å peak intensity at higher temperature may confirm Al- polymers within the interlayered space and HIV formation. Consequently, presence of mixed layer mineals indicate the effect of acid – leaching weathering on clay mineral transformation.

The energies of the emission spectral lines originating from vacancies in deep atomic shells change if the elements are in different oxidation states. These changes of energies cause small shifts in spectral lines. For Sulfur and Magnesium, these shifts are shown in this work, and also the influence that they may have on the calibration of wavelength-dispersive spectrometers and in consequence, on quantitative and qualitative analysis by XRF. Also, these changes prove to be useful in identifying oxidation states and in some cases phases in different oxidation states.

Crystal size distribution (CSD) in metamorphic rocks provide fundamental information about crystal nucleation and growth rate, growth time and the degree of overstepping. CSD data for garnet, staurolite, kyanite and andalusite crystals from the aureole demonstrate that the earliest formed of these minerals, garnet, has the highest population density and the shortest growth time. The last formed mineral, andalusite, has the lowest population density and longest growth time. Kyanite and staurolite have the similar population density and growth times intermediate between those of garnet and andalusite. These data demonstrate the effect of the degree of overstepping on the nucleation and growth rates of minerals during metamorphism.

Khezr-Abad pluton is cropped out in North-West of Taft. This granitoid seems to be younger than the surrounding metamorphosed rocks, particularly the lower cretaceous limestones and probably is implaced during Oligo-Miocene. The most volumetric abundances of the igneous rocks are: granodiorite, granite, quartzmonzo-diorite, quartz-diorite, and in a lesser amount tonalite, quartz-syenite and syenite. All granitoid rocks show Ba, K, Rb enrichment, and Nb, Sr, Ti depletion.From the economical potential point of view, mineralization of marble, Fe-Cu-Pb-Zn skarn and non-metalic minerals such as kaolinite are considerable.Geothermobarometry of rock forming minerals of this pluton indicates temperature of 810- 985 ˚C and pressures of 2.43 – 6.2 kilobars (kbar).