Researches in Earth Sciences
Year:2010 | Volume:1 | Issue:2|Papers Count:7

Mohsen Ebneh Ali area is located south-east of Borujerd and in the north-west of Sanandaj- irjan zone. The main lithology of this area includes Mesozoic volcano-sedimentary rocks which were metamorphosed in green schist facies. The study area with the variety of intrinsic geological units, introduce a high potential area for mineral exploration. In this respect, satellite images could give a good help to locate these units in a wide range views. In this research, Landsat ETM+ data were used to study petrology, hydrothermal alteration and tectonic structures. Different approaches were used such as band ratioing, principle component (PCA) and digital filtering. The structures were identified using remote sensing, methods and techniques provide the capability of creating a new lineament map of the study area. Based on this study, it is suggested that three areas are favorable for further exploration. To introduce intrinsic mineralization units, the highest probability of mineralization is considered. There are a close correlation between lineament structures and alteration zones in the area. Based on these studies, one group of alterations is detected to NW-SE faults in carbonate and metavolcanic rocks and others are detected to N-S faults and intersection of faults in areas with plutonic rocks.

The Abouzar Iron skarn deposit is located 110 Km to north-west of Mashhad and 10 Km north-east of Shotorsang village. The calcic-iron skarn formed in Lower Cretaceous limestone. The Exoskarn zones are: garnet skarn, garnet-idocrase skarn, plagioclase skarn, actinolite skarn, zoisite skarn and zoisite-epidote skarn. Granite, granodiorite porphyry, quartz monzonite porphyry, syenodiorite and syenite porphyry are identified. Syenite and syenodiorite are alkaline and granite-granodiorite and quartz monzonite are sub-alkaline. All of the intrusive are met-aluminous only quartz monzonite is per-aluminous. Syenite porphyry is ultra potassium, syenodiorite is high potassium and granitegranodiorite and quartz monzonite is low in potassium. Syenite porphyry has high potassium but other are enrich in sodium. The pattern of spider diagram is quite different among the intrusive, indicating that the source of the magma must be different. In comparison with MORB basalt, the pattern of spider diagram show enrichment of K, Rb, Zr, Ba and Y and depletion of P, Ti and Sr.  Based on mineral paragnesis, andradite was formed during prograde metamorphism (550oC). During retrograde metamorphism (<300oC), actinolite, chlorite, plagioclase, zoisite, calcite and epidote were formed. Abouzar Iron skarn do not contain Cu and Au and magnetite is the main ore mineral. The average ore grade is Fe=41.3%.

The Makran region located in the north of Oman Sea is composed of a large sedimentary prism accreted during the Cenozoic. In this study seismic reflection data, published geological information and regional seismicity have been utilized. Based on recent GPS study in the region the subduction velocity is measured to be at least 19 mm/year. The south-east part of Makran has been historically affected by tsunami. The most recent earthquake of magnitude 8.1 occurred in 1945 creating a huge tsunami in this region killing at least 4000 people and having great economical impact in Pakistan, Oman, and Iran. The western part of Makran lacks the seismicity based on historical as well as instrumental data and there has been no major record of seismic activities in the last 25 years. By assuming the reoccurrence of 1945 tsunami the temporal and spatial location of tsunami wave has been preliminary modeled for the coastal region of the Makran and Oman. Based on the result of this simulation the coastal region of Iran, Pakistan and Oman will be affected in less than 30 minutes. The coastal area of Iran along the Sea of Oman in the vicinity of the Indian Ocean has developed extensively during the last two decades and the high growth of population has increased the risk of death loss due to any future tsunami. Due to the above statement, to reduce the future damage, it is important to develop a tsunami early warning system and required rapid evacuation procedure in the vicinity of the coast.

Mineralization in Qaleh-Zari copper mine has occurred as a vein type and in the fractures of dextral shear zone with N135 trend. The azimuth of main fractures in order of significance is NW-SE, NE-SW, ESE-WNW according to dominant fault trend in the area, and they are orderly in the same trend with riedel and anti-riedel and extension fractures. The veins are in two phases, and follow the shear zone geometry. Simultaneous with increase of shear strain, primary vein phase has gained dextral rotation and then second vein phase has formed, therefore, the type of eformation in the area is non-coaxial. Average of strain ratios indicates constructional strain ellipsoid in flinn diagram for the area. Ramsay logarithm drawing using main strain plate logarithmic ratio also confirms oblate form strain ellipsoid for area. Relation between three parameters, u, K-value, k describing strain ellipsoid, strain ellipsoid shape of study area could be general oblate form. Dilatation value is 0.59 with mohr circle method.

Average precipitation of Iran is less than one forth in comparison with its global average. Because of the sensitivity of soil and water resources in western Iran as a relatively humid and mountainous region, the recognizing of Precipitable Pressure Systems (PPSs) is necessary. In this study firstly, we extracted 12 Monthly Heavy Rainfalls (MHRs) based on the daily rainfall data of 11 weather stations in western Iran and secondly, we analyzed daily weather maps at two levels including sea and 500 HPA for designing of monthly, quarterly and annual synoptic models. The results showed that most PPSs in western Iran originated from Mediterranean Sea. It was presented that Red Sea dispatched less PPSs during summer (zero percent) than spring (48 percent) towards the study area. The spring time of Red Sea correspond with the Mediterranean Sea ones. Also based on synoptic patterns, we found PPSs routes had slow regression from 20 degrees latitudes to North during spring and quick advance from North to 60 degrees latitudes during the autumn. It can explain the high frequency of PPSs during spring that was dispatched from Red Sea with its vertical shape. It may be causes the increasing share of PPSs dispatching from Red Sea toward Western Iran during spring in comparison with its autumn one. Therefore, Mediterranean, Red and Black Seas as huge water bodies respectively dispatched PPSs towards western Iran.

Soil erosion is a very essential problem in most countries, particularly in developing countries with arid and semi-arid climate. Soil loss, decrease of agricultural lands and products, dam's fillings, destruction of jungles, pastures and rural migration are all results of soil erosion. In this study, using AHP and RUSLE methods, rate and amount of soil erosion in Mamlou watershed (eastern Tehran) have been estimated. By means of, using satellite images and maps and applying effective factors including DEM, slope, precipitation, land cover, lithology and NDVI,. The final map of estimation of soil erosion is subdivided into five erosion groups; namly very high, high, mid, low and very low. The results showed that about 13% of the basin surface has high and very high erosion. The average amount of soil erosion in the basin surface is about 10.7 ton/hectare per year. In some western and southern subbasins, the amount of soil erosion is up to 80 tons. These subbasins show critical and crucial conditions and in connection with the construction of Mamlou dam priority should be giving to executing watershed management and soil conservation plans. The results also showed that, AHP method together with GIS is a powerful means for estimation, representation and zoning of soil erosion rate. Nevertheless, some more quantitative and new models can be used for attaining this goal.

Solar energy is the most important effective factor in evapotranspiration that can be change with the amount of any changes in the energy that reached to the ground surface.The aim of this study is to show the impact of altitude, slope and direction on the amount of estimated ETP in the Sabzevar Township.Results showed that there is 23.34% more ETP in the south compared to the north.Then, in a GIS environment, the map of DEM was created by using topographic map, and then the ETP map (according to dip direction). This map showed that the most area was occupied by the north face of slopes.Finally, the main ETP map (according to altitude and dip direction) was made, based on the obtained coefficient at the first step, multiplied to this ETP map. In the last step, by using tables in the GIS environment, the amount of ETP of each pixel on the ETP map multiplied by occupied area, the average of ETP for Sabzevar Township was calculated.This study showed that the amount of ETP by this method is 1164.8 mm.