فصلنامه زمین شناسی ایران
پیاپی 31 (پاییز 1393)

The study area is located in north of eastern Alborz range. In this study، it was evaluated the pattern of neotectonic in eastern Alborz and the distribution of seismicity and geomorphic pattern of Southern Golestan province. To assess tectonic activities in 22 separated subbasins، we have analysed neotectonic indices: the stream– gradient index (SL)، drainage basin asymmetry (Af)، reveres symmetry of topography (T)، hypsometric integral (Hi)، drainage basin shape (Bs) and mountain front sinuosity (Smf). The results of the analysis is accumulated and expressed as an index of relative active tectonics (Iat)، which divided into four classes from relatively low to highest tectonic activity. The high class values of tectonic activity for Iat mainly occur in the south and southwest of the Gorganrud- Gharasu drainage basin، while the rest of the study area has classes of Iat suggesting moderate to low tectonic activity. The rate of tectonic activity in this area will increase from north to south. This increase can be related to the position of peaks steam gradient index along the faults and segment faults. Also value of drainage basin asymmetry is calculated for all of the subcatechments greater or less than 50 that shows tilt for each stream toward West or East. The results of this study show that the distribution of seismicity، geomorphic and tectonic movements of studied area has been affected especially by Khazar and North Alborz faults movement and thrust fault in north of Gorgan. Areas with high tectonic activity and the high measure of tilting indicate that there may be a thrust fault، with a NNE-SSW approximate trend. On the other hand، this seismicity trend may be related to a deep and relatively young thrust splay in north of the Alborz range front.

Statistical and probabilistic methods to evaluate the uncertainty in the data and the validation of the answers obtained from the calculations are widely used. In this study، Monte Carlo simulation method is used in order to exactly determine the coordinates of the discontinuities and the validation of the results of the Dips software calculations. In this method by considering all possible states for variables with estimation of the probability distribution function and the sampling of the variables، the final function was simulated. In this study، the data of discontinuities related to the Saidi ornamental quarry stone are used. In the first step، by the use of the Dips software، major joint sets were identified. Then for calculation of coordinates of joint sets with use of Monte Carlo simulation for each joint set، 50،000 random data of dip and dip direction were simulated. In the final step، the statistical characteristics of dip and dip direction of each joint set were identified by use of simulated data. Finally، the simulation results were compared with the results of Dips software. The results of this study show that the level of accuracy in Dips software for the dip direction of discontinuities is an average of 99. 38% and for dip is an average 94. 34%.

The North Tabriz Fault is one of the major strike-slip faults (trending NW-SE) in NW Iran، that trends from Sofian to Bostan Abad. Generally، the fault consists of two main fault segments. In present research، to study the last active tectonics at the North Tabriz Fault region، evaluated young morphotectonical features and paleoseismology of northwestern fault segment evaluated. On the basis of morphotectonic approaches on this region، horizontal slip last event (MW = 7. 4، 1780 AD) are found in the ranges 3. 5 ±0. 5 m and vertical slip between 0 and 0. 5 m. However، by attention to H/V ratio can propose that NW segment of North Tabriz Fault act as pure strike slip which confirm by new GPS data on this part of Iran. On the basis of paleoseismological researchs، by examining a wall perpendicular to the North Tabriz Fault in North Sahlan Village، four old paleoearthquakes with relative magnitude of MW = 6. 4 has been detected. A young magnitude of the event، recorded in deposits of the paleoseismologic trench of the study area، close to 7 have been estimated that according to geographic and stratigraphic location، this event can be associated with historical earthquakes since 1780 AD (MW = 7. 4).

Abbas Abad ore district lies in a volcanic and volcanosedimentary belt in East Shahroud and hosts eight copper deposits. This belt is part of volcanic arc in north of central Iran. Copper mineralization is dominated by chalcocite with minor bornite، digenite and covellite. Mineralization occurs as disseminated، veinlet، and stock works. Four alterations (silicification، carbonatization، epidotization and chloritization) are detectable in the host rocks. Lithologies of the volcanic rocks are trachyandesite، trachyandesit basalt and trachybasalte and they have high potassium calc-alkaline to shoshonitic nature. Fractional crystallization and crustal contamination processes are involved in magma evolution. Plagioclase and pyroxene are main minerals and the most important texture (porphyric and glomeroporphyritic) has been observed in this rocks. Zoning، sieve textures and re-absorption in plagioclases، and sieve textures، the effects of corrosion on the margins of pyroxene، and roundness of mineral implies the existence of non-equilibrium conditions during solidification of magma. LREE and LILE enrichment and depletion of HFSE with negative anomalies of Nb، Ti and Ta elements in studied samples show the alkaline nature associated with arc (active continental margin). Ratio of Ba/La and Th/Ta in rocks confirm subducting continental arc for tectonic environment of this rocks.

The lithologies of regions near the collision zone are different from another region. Mapping in these areas need extensive and exact studies and tools because of the variety of rocks، intensive uplift and clutter of units. Hyperspectral sensor is one of the most advanced tools that can do imaging from hundred of delicate and continuous bands in visible and infrared spectrums، so it can identify many of terrain despite spectral similarities and complications. In present study، as the first survey of hyperspectral data efficiency of hyperion sensor in Iran to separate the rock units، spectral based method of spectral angle mapper applied on hyperion image in Tabas، East of Birjand. Based on various laboratory- field studies، the lithology of study area can be separated into five general groups: (ophiolite series، metamorphic units، Oligo-Miocene volcanic units، limestone and flysch units). Igneous units in this area include Cretaceous ophiolite complex and young volcanic set (Oligo-Miocene، Pliocene-Quaternary). Dispersed outcrops of metamorphic rocks are seen in parts of ophiolitic series. In this region، for calculation of processing results accuracy rate، some scarred locations and points were sampled according to field surveys. Some of these samples were analyzed in microscopic thin section and by electron microprobe system، based on these works، criterion points for processing results accuracy rate، are evaluated. According to calculation، the user accuracy coefficient of spectral angle mapper method on hyperspectral data in hyprion sensor reach more than 64% in some parts of colored- melange in the East of Iran that is acceptable ratio in separation of blended complicated units.

Neyriz ophiolite in Fars Province which formed as the result of the closure of Neo-Tethys ocean and Arabian-Iranian plate collision in Late Cretaceous، has high potential for ore deposits، in particular chromite. Pyroxenite is one of the main constituent units of ophiolites and electron microprobe analysis (EMP) shows that clinopyroxene (diopside)، orthopyroxene (enstatite) and olivine (cherysolite) are the most abundant minerals. The abundances of MgO، Fe2O3، Al2O3، Cr2O3 and TiO2 in chromites of Neyriz pyroxenites show affinities with the podiform chromites which formed from magma with bonititic composition with high Cr# (100 Cr/(Cr+Al)) and low content of TiO2. The results of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) analyses accompanied with the fire assay precon-centration demonstrate that platinum group elements in Neyriz ophiolite are more enriched relative to those of the primitive mantle. In addition، the concentrations of Pt and Pd in chromites within pyroxenites are higher than those of the pyroxene phases. In general، the amounts of these elements in Neyriz pyroxenites are much less than of economic threshold (5 ppm).

The aim of this study is to recognize diagenetic processes، microfacies and geochemical evidence for original carbonate mineralogy of Oligocene- Miocene Asmari limestone deposited in the Rig anticline at Rig mountain oil field. In this area، the Asmari Formation with a thickness of 364 m have been exposed as a sequence of thin، medium، thick، and massive carbonate rocks. Twelve microfacies types have been distinguished on the basis of depositional textures، petrographic analysis and fauna. These carbonate microfacies belong to four major sub-environments including tidal flat، lagoon، bar/ shoal، and open marine. Absence of turbidite deposits، reefal belt and gradual changes in facies indicated that the Asmari Formation was deposited in a homoclinal carbonate ramp environment. The main diagenetic processes includes: dolomitization، cementation، micritization، dissolution، and compaction. Petrographic evidence and variation of major and minor element and compare this information with modern aragonite warm water and calcitic cool to cold temperate carbonate and originally aragonite mineralogy of Ordovician sub-tropical carbonate، the calcite mineralogy of Permian sub-polar cold water of Tasmania، the Upper Jurassic aragonite Mozduran limestone، the Ilam carbonate formation، and the Fahliyan Formation indicate that original carbonate mineralogy was aragonite in the Asmari Formation. High Sr/Na ratio suggests original aragonite mineralogy. Variation of Sr and Na values versus Mn confirm replacement of aragonite by calcite during the two stages of diagenetic stabilization. The bivariate plot of Sr/Ca versus Mn shows that Asmari limestone have been influenced by meteoric diagenesis in a closed to semi-closed diagenetic system.

Adsorption is one of the effective and frugal methods that used for removal of toxic metals-such as lead- from wastewater. In this paper، effect of three parameters including pH، adsorbent dosage and initial concentration of lead has been studied by two inexpensive adsorbents including natural goethite and Hormoz island ochre. The effect pH on lead adsorption by each of adsorbents shows that lead adsorption percent increase with pH increasing to 5%. On the other hand، experiments showed that with increasing adsorbent dosage، adsorption percent increase in both adsorbents. But ochre unlike goethite has high ability for lead adsorption even in adsorbent dose 2 g/L. Investigations showed that in high lead concentrations ochre toward goethite is more effective adsorbent for lead. So that ochre under condition with initial concentration 150 mg/L، ambient temperature (23. 5◦C)، pH=5، adsorbent dose 6g/L، reaction time 60 min and particle size smaller than 230 mesh removes 97. 57% of lead. Goethite removes 78. 53% of lead at the same condition. In this condition، maximum lead adsorption capacity for ochre and goethite is 24. 39 and 19. 63mg/g respectively. Initial concentration and adsorption percent shows direct relation for ochre، but reverse for goethite. Langmuir and Frundlich adsorption isotherms show that goethite follows Langmuir model with correlation coefficient of 0. 995، but ochre almost follows both models of Langmuir and Frundlich.