فصلنامه زمین شناسی ایران
پیاپی 7 (پاییز 1387)

The rate of sedimentation in basins is strongly dependent on their geomorphologic effects. These effects appear in the shape of weathering formations, erosion of surface sediments and specially soils. In this study Kahab basin in Zanjan province is selected as the case study. Since, the construction of a dam on this basin is predicted; therefore, considering erosion and morphological aspects are required. The goal of this study is investigation of relationship between the geomorphologic effects and erosion and sediment in every part of basin by using of the geomorphologic units (qualitative) and experimental EPM (quantitative) methods. In this matter, landform’s characteristics and resistance of formations were selected as important factors in selecting and separating zones of geomorphologic units. Then, main data and the other effective factors were analyzed by those models. The results show the quaternary’s formations and Neogene’s deposits mainly as the weak formations (silt and marl) are important resources of producing sediment in Kahab basin. According to the model’s estimates the rate of sedimentation is about 23400 m3 per year. In order to increase the life of dam, performance of policies for controlling the erosion and sediment of Kahab basin is necessary.

In order to determine the effective factors in groundwater quality of Bandar Gaz water sources were tested graphical and multivariate statistical methods, the related data of seven well was used. The groundwater sources were seen differently according to Stiff and Drouv diagrams. The drawn composite plots were shown the linear procedure between Na+ and Cl-, due to mixture of saltwater and soft water. Dolomite saturated index(SId) was more than calcite saturated index(SIc), because the dolomite dissolve in direction of groundwater flow. According to correlation matrix, other ions (except SO42- and NO3-)were correlated respect with electrical conductivity. Cl- has more combination with Na+ and K+. The cluster diagrams show that there are similarity between Cl- -Na+ ions and Cl- -K+ in groundwater more than 95%, and 85%. With respect to cluster diagrams, the dominated type of groundwater was Ca-SO4-HCO3. According to the analysis method; five factors were effective on chemical combination of groundwater. First factor: intrusion of salt water because the Na+, K+ and Cl- ions have high factor loading. Second factor: Human activities (seepage of wastewater, absorbing wells and…), because nitrate had the highest load in third factor. The nitrate concentration in groundwater was influenced by wastewater and irrigation of agriculture fertilizers. Third factor: Aquifer hydrogeochemical process, because factor loading of Ca2+ and Mg2+ was decreased and Na+ was increased. Fourth factor: Feeding by surface water (river, runoff…) because of HCo3- and Na+ increment. Fifth factor: Dolomite solution caused to increase of Mg2+ factor loading.

The Ziyarat Formation is an Upper Paleocene to Middle Eocene carbonate sequences, located in North of Tochal Village (south-east of Tehran), near Emam Zadeh Abdollah. The Ziyarat Formation with the total thickness of 212.5 m is conformably overlies the Fajan conglomerate and is overlain by greenish tufaceous siltstone of the Karj Formation. The age of Upper Paleocene to Middle Eocene was considered for the Ziyarat Formation at the type section. Carbonate sequences of the Ziyart Formation mainly consist of large benthic foraminifera (e.g., nummulites and discocyclina) along with other skeletal and non-skeletal components. In this formation the water depth during deposition was determined based on the variation and type of different benthic foraminifera, and other components in different facies. Microfacies analysis led to recognition of 11 microfacies that are related to 3 sub-environments such as: inner ramp, middle ramp and outer ramp. Five microfacies such as evaporite, dolomudstone, ooid intraclast packstone to grainstone, miliolidae wackestone and alveolina nummulite packstone were recognized in the inner ramp. Four microfacies such as nummulite packstone, red algae nummulite packstone, discocycline nummulite wackestone and nummulite discocycline wackestone to packstone are belong to middle ramp. And finally, two microfacies such as benthic foraminifera packstone and radiolar sponge spicule wackestone were distinguished in outer ramp sub-environment. In this study, an absence of calciturbidite deposits, reefal facies, gradual facies changes and widespread tidal flat deposits, support that the Ziayart Formation was deposited in a (homocline) carbonate ramp environment. Due to the great diversity and abundance of larger benthic foraminifera, this carbonate ramp is referred to as a "foram-dominated carbonate ramp system".

In this research, hydrothermal alteration zones in Meshgin Shahr – Ahar area, located in the north-west of Iran, have been investigated using image processing techniques of remotely sensed data. Landsat ETM+ images have taken in 29/7/2002 was used for mapping alteration. General alteration trend in the area was mapped by conventional methods consisting Color Composite, Band Ratio, Principal Component Analysis, Crosta technique and Density Slicing. Detailed mineral mapping also carried out by using analysis of spectral library data.The results achieved from different methods indicate same alteration trend in the study area. The accuracy from Crosta technique relative to the ancillary alteration data was 81.95%. The accuracy achieved from analysis of spectral library data and density slicing were respectively 53.24% and 49.37%

Dezful Embayment is located in the SW of Zagros orogenic belt. This embayment consists of long anticlines with distorted fold axis. Fold axis curvature is the main reason for highly fractured zone in the anticlines and very important for the studies in the oil reservoirs. Identification of main factors of deviation in fold axis trend, can helping us to identify different regions with high density fractures. These factors are very useful in the development of the reservoir, which can give us a comprehensive understand for the detail analysis of the oil field structures. This research has been highlighted the effective factors of Aghajari fold axis curvature. The main reasons for this phenomena are special mechanism of the shear system which is dominated in the study area and, the effect of basement faults. Also, present research offered, a simple model for basement faults of Dezful embayment. Based on this model Dezful Embayment consist of three basement blocks with faulted boundries. Dextral movement of these faults is caused an en echelon pattern in the region, also several reidel fractures has been recognized.

The Chahar-Borj stratigraphic section in north-west of Esfaraien, East Alborz, consists of Frasnian fossiliferous limestone succession. The main part of these carbonate is composed of solitary and compound corals. Up to 11 species of corals belonging to 8 genera have been distinguished. These are as follow: Scenophyllum sp., Tabulophyllum mcconnelli, Tabulophyllum gracile, Tabulophyllum sp., Sinodisphyllum variable, Sinodisphyllum litvinovitshae, Disphyllum virgatum, Temnophyllum lapparanti, Charactophyllum nanum, Michelina sp. and Syringopora sp.Based on the identified coral fossils, an age of Frasnian has been quoted to the unit. All identified species here, introduced for the first time from the studied area. Some identified index Frasnian species here have been reported from other parts of Iran: Alborz Mountains and Central Iran. This evidence display all this areas have been covered by the same sea. In a larger scale, similar situation have been reported from South of China, Australia and Afghanistan. This indicates similar latitude position for these areas.

There are different interpretations on ultramafic rocks suite which are located at the North of Fariman- Torbat - Jam lineament, NE of Iran. Most authors interpreted these rocks as oceanic crust remnants wheras some authors believe that they are lavas with komatiitic to tholeiitic affinity. Obviously,These diffetent intetpretations have contrary geodynamic implications. Here, on the basis of incompatible trace rocks. Our observations including various immobile trace elements rations and position of rocks in (Nb/Th)N versus to (Nb/La)N, Nb/Th versus Zr/Nb diagrams indicating that they are not comparable to MORB like magmas. Moreover in a clear contrast to MORB most samples are plotted on or upper than Nb line in Zr/Y versus Nb/Y diagram, a geochemical feature that demonstrate their petrogenesis relation to the heterogeneous mantle plume source. The same inference may be bring up by spinels chemistry, as they have high and low contents of TiO2, Al2O3 respectively and set between spinels of plume related magma in the related diagrams. Key words: