Iranian Journal of Geology
Year:2008 | Volume:2 | Issue:7|Papers Count:10

The rate of sediment yield in basins is strongly depending upon their geomorphologic effects. These effects reflect in the type of weathering rocks, erosion and transport of surface sediments, especially soils. In this study, Kahab basin in Zanjan Province is selected as the case study. Since, the construction of a dam has been proposed to build in this basin; therefore, study of erosion and sediment products are required. The goal of this study is investigation of relationship between the geomorphologic effects and erosion and sediment yield 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 rock units to erosion were selected as important factors in zoning of geomorphologic units. Then, the major data and other effective factors were analyzed by those models. The results show that Quaternary alluvial sediments and Neogene deposits are relatively erodable (silt and marl) and are important sources for producing sediment in Kahab basin. Based on the model, the rate of sediment yield is estimated to be about 23400 m3 per year. In order to increase the life of dam, it is necessary to study the controlling factors for erosion and sediment yield in the Kahab basin.

In order to determine the effective factors in groundwater quality of Bandar Gaz, the related data of seven well was used for testing water sources by graphical and multivariate statistical methods,. 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 S042- and N03-) were correlated respect with electrical conductivity. CI- has more combination with Na+ and K+. The cluster diagrams show that there are similarity between CI- -Na+ ions and CI- -K+ in groundwater more than 95%, and 85%. With respect to cluster diagrams, the dominated type of groundwater was Ca-S04-HC03 .According to the analysis method; five factors were effective on chemical combination of groundwater. First factor is related to intrusion of salt water because the Na+, K+ and CI- ions have high factor loading. Second factor is human activities (seepage of wastewater, absorbing wells etc), 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 is also related to aquifer hydro geochemical process, because factor loading of Ca2+ and Mg2+ was decreased and Na+ was increased. Fourth factor could be related to feeding by surface water (river, runoff) because of HC03- and Na+ increment. Fifth factor is related to dissolution of dolomite that causes to increase of Mg2+ factor loading.

The Ziyarat Formation (Upper Paleocene to Middle Eocene) is a carbonate sequences, exposed north of Tochal Village (south-east of Tehran), near Emam Zadeh Abdollah. The Ziyarat Formation with the total thickness of 2l2.5 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 consist mainly of large benthic foraminifera (e.g., nummulites and discocyclina) along with other skeletal and non-skeletal components. The water depth during deposition of this formation was determined based on the variation and type of different benthic foraminifera, as well as 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 belonging to middle ramp. Finally, two microfacies such as benthic foraminifers' packstone and radiolar sponge spicule wackestone were distinguished to have been deposited 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 "foramdominated carbonate ramp system".

In this research, hydrothermal alteration zones in Meshgin Shahr - Ahar area, located in the northwest 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 the 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 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 is very important for the studying of the reservoirs in oil fields. Identification of main factors for 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 understanding for the detail analysis of the oil field structures. This research has been highlighted the effective factors in Aghajari fold axis curvature. The main reasons for these 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 consists of three basement blocks with faulted boundaries. Dextral movement of these faults is caused an en echelon pattern in the region, also several redial fractures has been recognized.

The Chahar-BOIjstratigraphic section, 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 identified. 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 identified coral fossils, an age of Frasnian has been quoted to the unit. All identified species in this measrured section have been introduced for the first time from the studied area. Some identified index Frasnian species trom Chahar-Borj have been reported from other parts of Iran such as Alborz Mountains and Central Iran. This evidence indicates that all these areas have been covered by the same sea. At 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 north of Fariman- Torbat - Jam lineament, NE of Iran. Most authors interpreted these rocks as oceanic crust remnants whereas some authors believe that they are lavas with komatiitic to tholeiitic affinity. Obviously, these different interpretations have contrary geodynamic implications. Here, on the basis of incompatible trace elements and chemistry of spinel, petrogenesis and tectonic setting have been studied. 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 MORE, 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 Ti02, Al203 respectively and set between spinels of plume related magma in the related diagrams.