Iranian Journal of Geology
Year:2010 | Volume:4 | Issue:13|Papers Count:10

At the NE of Baraghan, gabbroic to monzonitic sill, known as Karaj Dam sill, intruded into the tuffs. Based on field observations and microscopic studies, the sill is differentiated from margin toward the center. Plagioclase crystals sometimes show zoning, but the zoning is not present in rocks with myrmekite texture from the lower part of the sill. However, twinning is preserved in unzoned crystals. Myrmekite is wart like type. High temperature ferromagnesian minerals are decomposed but plagioclases are mostly remained fresh. Based on whole rock XRF analyses, there are non-linear trend on Rb-SiO2 and K2O-Na2O diagrams. Based on norm calculations, Na2O values decreased and K2O values increased in samples from the contact with country rocks. It could be due to extraction of Na2O from the rocks by fluids. Such textural, mineralogical and geochemical features are evidences for low potasic metasomatism in lower part of Karaj Dam sill. Fluid had influenced on tuffs and caused kaolinitization of K-feldspar, sosuritization of plagioclase and chloritization of ferromagnesian minerals. In the other hand, fluids made chemical re-mobilization of ore minerals and accumulation of secondary copper minerals in the tuffs.

Weatherablity of clay-bearing rocks and reduction of their geomechanical properties with wetting and drying cycles, which determine with slake-durability test, is one of the most important challenges in construction of structures on such rocks. However, many investigations, including the investigation carried out on this research; show that determining slake-durability index of hard and strong rocks such as sandstones using the initiated method can provide useful information from geomechanical properties of such rocks. In this research, some slake-durability tests have been carried out on some samples from Shemshak Formation and this index has been tested in different sandstones and clay-bearing rocks this formation. Meanwhile, the effect of the number of cycles, period of time the sample is rotating in water and angularity of the rock samples on the slake–durability index as well as the relation between this index and uniaxial compressive strength has been investigated. This study shows that the as the number of cycles increased the slake–durability index of sandstones (different types) and clay-bearing rocks decreased. Investigation on the effect of the time period the sample was rotating in water indicated that this factor has meaningful effect on the studied index of sandstone samples. However, the effect of the angularity of samples is quite considerable on the slake–durability index, so that in the samples with slake–durability index of above 98%, most of the angles are rounded at the end of the second cycle and there is a considerable differences between the slake-durability index in the first and second cycles of the angled samples and rounded samples. But the differences are much reduced in cycles three to five. In clay-bearing rocks with slake-durability index of lower than 98%, the effect of the angled nature on this index is more than sandstone samples, in cycles two and above. Investigation of the relation between the slake-durability index and uniaxial compressive strength shows that the slake-durability index is an acceptable and appropriate mean of estimating uniaxial compressive strength, especially in the sandstones.

Structural originating of the southern Birjand Ophiolite Mélange is required to be an implementation of various stress phases in the evolution history of this region. Separation of different phases in the multiple inverse method shows that the maximum stress axis (s1) in several position of this zone has mainly NE-SW to E-W trends and the minimum stress axis (s3) NW-SE to N-S trends. By using obtained stress orientations and compiling them with the other obtained structural data, such as extensional structures (normal faults and extensional fractures), compressional structures (thrust faults, lineation and foliation trends in flysch units and the orientation of folds axes), shear-comperssional structures (fracture types in the crashed zones) and extensional structures (strike-slip faults with normal tensor, extensional and sigmoidal fractures), it is concluded that paleotectonic of this region has been affected by three stages including comperssional, shear-compersional and extensional.

One of the most important parameters required for tectonic interpretation of the earth’s crust activities is the knowledge of temperature within the earth. However, this parameter is rarely well studied. Having estimated curie depth (forming the base of magnetic crust), a boundary condition of temperature is obtained for continental crust. This paper applies equivalent source magnetic dipole method to calculate curie depth based on satellite magnetic models. In fact, a new and different method of applying geomagnetism to estimate curie depth is discussed. In this paper, the new magnetic field model MF5 is used to calculate curie depth of an area located within 28-36o N and 56-64o E. First, crustal induced field is calculated using magnetic field model MF5. Then, an initial VIS model is prepared and its calculated field, at the satellite altitude, is compared with the observed model. The results show that the curie depth in the study area is shallower than the moho and lies within the earth’s crust. All the programming of this research was done in MATLAB R2008a.

Kighal quartz-monzonite porphyry stock is located north of Varzeghan city, East Azarbaidjan Province, NW Iran. This stock has intruded into older volcanic units, during magmatic activities of Pyrenean orogenic phase and produced hydrothermal alteration zones and Cu-Mo mineralization in the region. After its emplacement, numerous cross-cutting dikes, ranging in composition from diorite through quartz diorite, granodiorite, microdiorite and monzodiorite, along with a smaller granodioritic body have intruded into porphyry stock. The granodioritic body has not produced mineralization and hydrothermal alteration. Based on chemical analyses of the samples of porphyry stock and dikes, it is concluded that they belong to high-K calc-alkaline to shoshonitic magma series. These intrusive rocks have emplaced in post-collisional volcanic arc and active continental margin setting.

The study area is located in eastern Iran, about 15 Km southeast of Gonabad. Low grade regional metamorphism (Jurassic-Cretaceous orogeny) has turned shale and sandstone of Jurassic into slate and quartzite. Slates are metamorphosed to different types of schist around the contact of granodiorite. Both magnetite and ilmenite granitoids were identified. Biotite granodiorite batholith belongs to ilmenite series. Monzonitic subvolcanic forms as stock and they are younger than granodiorite. Based on mineralogy and high values of magnetic susceptibility [(>500)×10-5 SI], the monzonite is classified as the magnetite-series of oxidant type granitoids (I-type granitoids). Alteration zones associated with granodiorite are: sericitic, propylitic, silicification, argillic and tourmalinization. Heavy minerals (stream sediment) originated from granodiorite of the eastern section shows anomalies of Sn, Au, As, Pb, Zn, Cu, W. The highest values of these elements are: Sn=445 ppm, Cu= 321 ppm, As=399 ppm, W=59 ppm, Pb=980 ppm, and Zn=608 ppm. Analytical results of 77 samples, taken from granodiorite and monzonite (altered and mineralized), show high anomalies of Sn, Cu, Au, Pb, Zn, W within granodiorite outcrop in the eastern section of the study area.

In this research, the data of LISS-III sensor used for mapping saline soils on the vicinity of Tashk and Bakhtegan Lake, Fars Province. After the corrections of the imagery, the training and control pixels selected and the soil samples (depth of 5 cm) prepared. Then pixels of the imagery classified in different approaches by maximum likelihood algorithm. Analysis of spectral graphs of classes indicated that the most reflectance of saline soils was in visible spectral. The highest correlation coefficient between salinity values and digital numbers of bands (0.45) observed in band 2. Investigation of feature space graphs indicated, almost single clusters formed in all of the classes except in low and moderate saline soils. The white salt crusts lied in the highest portion of soil line and black salt crusts in lower parts. The roughness and moisture were the main factors in reflectance decreasing of salt crusts in studied region. In non-saline soils, the roughness are produced by large clods in ploughed areas was the effective factor of reflectance decreasing. Presence of plant cover and residual of the straw are the reasons for error in identifying of saline soils. Results of classification of different approaches indicated the highest accuracy of procedure, user, overall and kappa index was observed in integration of all bands. In all of approaches, soils with low and moderate salinity had low accuracy. The produced map of LISS-III sensor indicated that when the salinity values is above 16 dS/m, this is on the soils at the vicinity of the lake and as move further, it is decreased and in the central parts of the plain and in agriculture lands, it is increased again.

In this study, depositional environment of the Faraghan Formation has been interpreted in Darang #1 well. Petrography studies of the cuttings led to identification of five petrofacies that according to their abundance include: lithic arenite, quartz arenite, greywacke, hybrid arenite and mudstone. More than 90 percent of this succession is composed of lithic arenites with volcanic rock fragments and fine grained quartz arenite. In this study, we combined petrofacies analysis and gamma ray logs to reconstruct sedimentary environment of this formation. According to our data, six sedimentary facies has been identified. Therefore the Faraghan Formation has been deposited in the upstream parts of delta plain to delta front in the lower part and shallow marine in the upper part of the succession which grades upward into a carbonate shelf deposit of Dalan Formation.