مجله پژوهش های دانش زمین
پیاپی 38 (تابستان 1398)

In order to develop management plans for water and soil conservation and erosion control, it is necessary to identify the sources of sediment yield and the contribution of each source in watersheds. The aim of this study was to determine the contribution of different geological units to sediment yield of the Toulbane watershed in Golestan province. In view of this, samples were collected from different geological units. Collecting suspended sediment samples was carried out using Philips time-integrated sediment sampler over a one-year period (2017). Afterward, the concentration of 34 geochemical properties was examined for 41 source samples and 8 suspended sediment samples in the laboratory using the ICP device. Next, the optimal composite fingerprints were determined to discriminate sediment sources by using three statistical tests including mass conservation test, Kruskal-Wallis and stepwise discriminant function analysis. As a result, 15 tracers were selected as the optimal composite fingerprints and the contribution of different geological units to sediment yield was determined using the data derived from these tracers and implementing the multivariate mixing model. According to the results, the Qal and Jsl s.sh units had the highest contribution to sediment yield with the respective values of 68.22% and 28.75%. The Qal contains quaternary deposits and the Jsl s.sh (Shemshak formation) consists of sandstone and shale materials; both of which are highly sensitive to erosion. Hence it is necessary to carry out erosion control actions on erodible units to reduce sediment entrance to the river.

Soil erosion is a geomorphic process that can increase soil losses and affect the dynamics of soil biological diversity. Soil biological diversity can considers as an indicator for assessing adaptation rate of arid ecosystems against environmental changes. This study evaluates variations in soil microbial diversity and physiochemical properties in erosional landscapes. Since, arid and semi-arid ecosystems have a critical role in flux of carbon dioxide to atmosphere; many erosional landforms belonging to these ecosystems can occur a condition for sequestrating carbon and subsequently positive impacts for increasing resilience level against environmental harshness. One of the common landforms in arid landscapes is alluvial fan. Soil samples were collected from different topographic positions of the three alluvial fans for measuring enzyme activities, particle size distribution, soil water, soil microbial activity, and soil organic carbon. The findings showed that different positions exhibit different conditions in terms of carbon mineralization and sequestration causing the heterogeneous dynamics of soil biological properties.

Biological soil crusts are communities composed complex species of algae, fungi, cyanobacteria, lichens, fungi and bryophytes and soil particles associated with them. In this research, the effect of moss and lichen on soil physicochemical parameters in arid and semi-arid region of Takhte-Sultan in Khorasan-Razavi has been investigated. Samples were collected in summer along a linear transect by using 50 x 50cm quadrates. All soil samples were taken in 3 replicates from the 0-5Cm and 5-20 Cm. So, 60 samples were taken to compare lichen and moss crusts effects on the soil physicochemical properties. The results of analysis of variance and Tukey test showed that the presence of bio-crusts have affected the soil parameters. Including by decreasing pH and EC in soils without crusts and increasing organic carbon and calcium carbonate in the presence of moss and lichen at 0-5 cm depth. As a result, there is a significant difference in the physicochemical parameters of soil in the presence or absence of moss and lichen crusts in the desert landscape.

Quantitative forecasting and determining the processes involved in the production of surface runoffs and their transportation to the basin outlet is very crucial. The estimation of runoff production potential of a basin is highly important in soil and erosion conservation, as well as in managing the basins that produce runoffs and sediments. The Lavijrood watershed can produce seasonal floods; this is due to its topographical and physiological situation, climate system, non-compliance with technical construction standards, riverside violation, geology, and the other factors that affect the runoff production. In this research, we investigated the performance of the circular automata (CA) model as a suitable estimation method, and examined the possibility of integrating the method with the ArcGIS application to simulate the flood hazards and the hydrograph flow for the Lavijrood. The runoff level and the flood hazard were obtained through the SCS method. The flood simulation using the SCS method requires the data of land use, hydrologic groups of soils, Digital Elevation Map (DEM), rainfall, and the roughness coefficient of the basin. The raster format of all these layers was prepared with cell sizes of 30×30 m. Also, the flow depth and flow velocity were calculated based on the kinematic wave model and Manning equation; then travel time was obtained from the flow velocity. Based on these input data, the flood discharge time series graph was plotted for 35 maximum 24-hour rainfall events during the years 1994 to 2018. The correlation coefficients between the observational and simulated average discharge values in an hour and the maximum discharge of a 24-hour-rainfall in the Aghooz-Katty station were o.95 and 0.98, respectively. This means that, despite its simplicity, the CA approach provides realistic results for complicated natural events like runoffs. Furthermore, the error values of observational and average simulated discharges over an hour and the maximum discharge of a 24-hour-rainfall were 14 and 8.3 %, respectively, which shows a proper precision for the model.

Today, tourism is considered as one of the most sustainable economic resources of different regions,; the Qasarshirin district in Kermanshah province is a suitable place for the development of war tourism which results in economic prosperity and job creation. This descriptive-analytical study of the area seeks to introduce tourism as a potential opportunity for economic development in Qasr-e-Shirin region, and to gather information to prove it through library and field research. The data was analyzed using 311 questionnaires in three groups (residents, managers, tourists). The SWOT strategy was used. The results show that the collection of internal environment (strength, weakness) is 3.2 and the set of environmental points (opportunity and threat) is 2.1 which consist of conservative strategy (ST). Therefore, according to SWOT table, strategies including the use of local forces for employment and activities in the opportunities created, recognizing the threats of this type of tourism and trying to eliminate it, creating museums and exhibitions of this kind of tourism, training local community , attracting private sector investment, creating a supportive package in the form of this type of tourism, determining target areas for this type of tourism in neighboring countries, and strengthening the social and collective participation and development of productions related is necessary for the development of war tourism.

The present study used two methods of circulation to peripheral and peripheral to circulation. To study and analyze the spatial movement of sub-tropical jet, the data of the website http://www.esrl.noaa.gov was used. The maps of jet for a 21 year statistical period (from October to May) were produced using Grads software, and the axis of jets for every month were drawn on the basic maps produced in ARCGIS10.4 software. Afterwards, the monthly precipitation data of nine synoptic stations in Fars province during the crop year of 1996-2017 was extracted, and the samples were selected. Examination of jet axis in different months showed that jet axis has relatively much northward and southward movement. From the early October, gradually the jet streams locate in proper places following the eastern movement of Arabian high pressure, and provide proper condition for atmospheric instability. In January and December, the jet is located in its best place. The results of the synoptic patterns of heavy rains showed that from a few days before the start of precipitation, a deep ridge develops over Africa and central Mediterranean to the north of the latitude of 60 degree and cause fractures in the Rossby waves. The resulting sever thermal gradient causes a deep trough over the eastern Mediterranean which is intensified following the advection of cold sub polar over Sudan system, and proper moisture advection over the southern warm seas of sub-tropical jet stream, and creates sever instability over the region.

Flood is a common natural disaster that causes immense damage to the natural environment, construction and casualties worldwide every year. The control factors of the flood are power, magnitude, and frequency, duration of the flow and changes of cross-sections. In this research, the quantitative fringe of Gamasiyab River (located in the Kermanshah province) has been investigated using DLSRS model. The DLSRS is the first mathematical model for calculation of quantitative fringe according to the rules and regulations of the country. First, the cross-sections were extracted by the HEC-GeoRAS extension in GIS software. Then the quantitative fringe of Gamasiyab River has been calculated for 130 cross-sections by five indexes including discharge (25 years return period), location of the river, stability of the bed and bank, flow regime and social tension. The results of the model show that the quantitative fringe was 3 to 13 meters on average in different reaches so that the highest value of the fringe in the Gamasiab River was in the reach 1 and the lowest was in the reach 11. Also results show that this model was not suitable for all of the rivers in the country and it is suitable for the rivers that have different stream orders. Therefore the results of this model will not be acceptable for the Gamasiyab River (the stream order of this river is 5th). This model is suitable for the rivers which have bare and non- proprietary riparian.

Mishan Formation is one of the Neogene stratigraphic units that is widely distributed in the south and southwest of Iran. In recent years, in order to achieve the exact age of this formation, studies have been carried out using fossil data and the use of strontium isotopes. In the young folded areas, such as Zagros folded belt that containing sediments that have not been deeply buried, using magnetostratigraphic study is one of the most appropriate methods for obtaining the age of sediments. This method can be used for non-marine sediments such as alluvial deposits that often lack the biostratigraphic and radiometric properties for age determination can also obtain the sedimentation rate of the studied sequence. In the present study, the age of the Mishan Formation was studied using magnetostratigraphic method in Jarik anticline on the northeast of Dezful embayment. In the studied section, the age of the lower and upper boundary of the Mishan Formation, is estimated to be 14.1 and 13.6 million years (middle Miocene) respectively. Also the average sedimentation rate for this formation (after secondary compaction) was obtained 38 cm / 1000 years.

Small gneissic granite body of Abadchi is a deformed, folded and metamorphosed granitoid which occurred in North of the lack of Zayandeh-Rud dam, as a part of Sanandaj-Sirjan Zone. The mineralogical composition contains quartz, plagioclase, K-feldspar, biotite, amphibole and muscovite as main minerals, as well as zircon, titanite and allanite as accessory minerals. Zircon typology of the gneissic granite body mostly introduces the fields P2. The morphology of zircon grains represents a slightly crust to mantle origin for protolith magma of the gneissic granite. According to the zircon morphology, as geothermometer, the crystallization temperature of the zircon crystals is about 750 -800 ° C.

The Lar carbonate formation has a high potential for karstification, with extensive expansion in the southern parts of Behshahr. Different types of karstic phenomena such as caves and sinkholes have been identified in this formation. For more accurate study of karst in the around of Gelevard dam, 101 thin sections of rock samples related to GV1 borehole located at the left side of the dam were prepared and studied. Then, according to lithological changes and observation of karstic cavities in the cores, 20 rock samples were selected and geochemically analyzed by XRF method. Investigating the changes of trace elements, and Sr / Mn and Na / Mn ratios, showed that the penetration of surface water and the increase of meteoric diagenesis in the karstic zone increased the amount of iron and manganese (1500-90 ppm respectively) and reduced the sodium and strontium (around 390-360 ppm respectively) and their ratio to manganese. Therefore, along with karstification, the alteration of the trace elements occurs at the margin of karst, which goes back to normal by distancing from it. Hydrchemistry analysis of water samples from Gelevard reservoir and drawing of Piper and Duro diagrams shows that the water type in most springs is calcium-magnesium bicarbonate, which corresponds to the type of karst aquifers. Calculating of saturation indexes using the PHREEQC 2.6 software indicates that spring waters are often supersaturated from calcite and aragonite and also dolomite in the dry period. The study of water discharge (Q) and electrical conductivity (Ec) of some springs alongside the saturation index, shows that flow system in karst springs is often conduit- diffuse type.

The intrusions of Boroujerd Granitoid Complex and Alvand batholith in the pelitic rocks have caused the formation of pelitic hornfels and partial melting migmatite in the metamorphic aureole. In the Tuyserkan and Boroujerd areas, the partial melting and migmatization phenomenon occurred in high grade metamorphic rocks owing to the influence of mafic and ultramafic rocks. Leucosomes are composed mainly of quartz and K-feldspar minerals, in which the potassium feldspar is subhedral to euhedral and quartz has filled interstitial texture between them. Paragenesis mineral of these two regions are very similar. The presence of spinel and corundum minerals and the abundance of andalusite is evident in the mesosome of Boroujerd's migmatite while there is no corundum in the mesosome of Hamadan's migmatite, and there are more abundance of cordierite and garnet. In the Hamadan region, the And + Spl + Crd symplectic exists in the part of the mesosome of the migmatitis, while in the Boroujerd region there is And + Spl + Crn symplectic in part of the mesosome of migmatitis. Based on field observations and petrography, the formation of the migmatite in both regions is occurred as the result of partial melting process. The effective reactions in the melt formation and the leucosum of the migmatite include melting reactions in the presence of a fluid phase and melting reactions without the presence of a fluid phase. The reaction Bt +And = Crd + Spl + Kfs + melt are the most important melt development reactions in the metapelite rocks of Alvand aureole while the reaction of Bt + And = Crd + Kfs + Spl + Crn + L are the most important reactions of melt development in metapelite rocks of Boroujerd aureole.

The effect of basement’s upper surface morphology on the accommodation development is investigated in this study, through a case study from the Asmari Formation in Dezful Embayment and Abadan Plain. Considering the depth of the basement’s upper surface, position of the studying formation’s bounding surfaces, its thickness and total thickness of basin fill sediments are calculated. Based on the available data from previous researches and data extracted from more than 200 drilled oil wells in the studied area, the maps of basement surface, the Asmari Formation bounding surfaces, isopach maps of the Asmari Formation and total basin fill deposits are created. Results from this study shows the minimum and maximum depth of the basement’s upper surface 7,000 and 15,000 meters respectively. The deepest level of the surface is in the north Dezful Embayment, while the shallowest level in the southern Dezful and Abadan plain. The maps of the formations bounding surfaces well correlates with the basement’s upper surface map, especially in the north Dezful embayment area. Similar results are achived from the correlation of created isopach maps with that of basement’s top. However, slight discrepancy in the correlations is observed in the south Dezful embayment. Results of present study clearly show that development of accommodation space of the Asmari Formation in the north Dezful embayment and Abadan plain was mainly affected by the basement upper surface during different sedimentation periods. The accommodation space in the southern Dezful embayment was most likely affected from the basement faults’ actvities. Highest rate of sediment supply was recorded in the middle part of the north Dezful embayment.

Morphometric parameters of catchments such as area, slope and main stream length can affect some physical characteristics of aggregates including roundness, surface texture, and micro-cracks. In this study,12 alluvial fans with similar catchment lithology were selected based on satellite images, geological maps and field works. In mid part of each fan,150 samples from 3 different sizes of gravel (50 samples for each size) were collected and the above mentioned characteristics were measured. Results show that roundness increases, surface texture soothes and micro-crack decreases with decreasing in slope and increase in area and main stream length of catchments. The lowest rate of roundness belongs to alluvial fans having catchments areas of 33 and 27 hectares and to smallest aggregates (12.5-16 mm), whereas, the highest value of roundness is related to alluvial fans with largest catchments (309 and 206 hectares) and aggregates (37.5-25 mm). In terms of surface texture, the highest crenulation is related to alluvial fans with catchment of 25 hectares and to aggregates size of 16-12.5 mm, whereas the lowest crenulation belongs to alluvial fans with largest catchments (309 hectare) and largest aggregates (37.5-25 mm). In terms of micro-cracks, the lowest percent of cracks (10%) is related to smallest aggregates, and alluvial fans with largest catchment. While the highest percent of cracks (32%) is observed in largest aggregates and in alluvial fans with catchments having areas of 29 and 33 hectares. The main stream length effect on the aggregates characteristics is similar to the effect of catchment area.

Examination of geochemical distribution pattern of trace and rare earth elements in the rocks affected by metasomatic processes revealed a magmatic origin for Th-REE mineralization at the Se-Chahun ore deposit. Chondrite and primitive mantle-normalized patterns of REE and trace elements for the rhyolitic host rocks (which formed in a subduction setting) compared with the patterns of the Th-REE mineralization zone also provides evidence that the origin of the Th-REE mineralization zone is similar with rhyolitic magma or a magmatic chamber from which the rhyolitic magma was originated. This is also supported by oxygen and hydrogen isotopic data in actinolite paragenetically associated with Th-REE bearing minerals. Thorium minerals at the Se Chahun ore deposit include huttonite and thorite. O and H isotopic data for actinolite paragenetically associated with Th-silicates revealed a magmatic source for Th-REE mineralizing fluids in the ore deposit δD and δ18O for actinolite paragenetically associated with Th silicates are calculated between -73.29 to -42.04 and 6.65 to 7.71, respectively, which lie within the field of magmatic fluids.