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No 49
Vol. 49 No. 13
2019
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A thick sequence of Late Cretaceous volcano-sedimentary rocks crops out on the northern margin of Central Iran, in the southwest of the Sabzevar. The igneous rocks include extrusions (trachy-andesite, dacite and rhyolite) and shallow depth intrusions (gabbro, gabbrodiorite, diorite and granite). These igneous rocks have geochemical signatures of magmatic rocks of island-arc subduction zones and plot within field in different tectonic setting discrimination diagrams. The parental magma of these rocks has island arc tholeiitic nature and was produced via partial melting of a depleted spinel lherzolite mantle source during closing of the Sabzevar Neo-Tethyan oceanic basin in the Late Cretaceous. This depleted mantle source was affected by the metasomatic fluids released from dehydration of the Neo-Tethys subducted oceanic slab.
Zakieh Kazemi - Habibollah Ghasemi - Fardin Mousivand - Wilyam Griffin
Keywords : Igneous rocks ، Magmatism ، Sabzevar ، Central Iran ، Late Cretaceous ، Neo-Tethys
Plastic behavior and significant thickness of the Gachsaran incompetence formation on top of middle carbonate units in the sedimentary sequence of the southern Dezful Embayment led to the emergence of different styles of folding above and below of this formation. So that the structures in the upper and lower parts of this formation are completely separated and do not match each other. In the upper anticlines, above the Gachsaran horizon, the calculation of the limbs angle, the main thrust slope and the percentage of forelimb thickening indicate the fault detachment fold style. This style marks the geometry of fold at the early stage of the development of this anticline. Also the seismic profiles below the Gachsaran horizon also show the fault-propagation folding style. In the south Dezful Embayment, folding in the Gachsaran Formation occurs with shorter wavelengths in the form of disharmonic folds. This folding acts as the decoupling surface for the lower folds so that the synclines in this moving horizon directly cover the lower anticlines. The rounded folds in the carbonates in lower anticline are the imposed folds associated with steepened up reverse faults, detached on the basal decollement level and ultimately faulted by progressive deformation. The interpretation of seismic sections in the southern Dezful Embayment shows that lateral migration occurs in the salt units of the GS2 and GS4, and the upper and lower units of the Gachsaran Formation do not play a role in salt migration. Lateral migration in Miocene salts of the Gachsaran Formation is accomplished by the growth of sub-anticline during folding and loading of upper formation at the upper Gachsaran Formation.
Mehdi Yosefi - Seyd Morteza Moussavi - Mohammad Mahdi Khatib
Keywords : Rag sefid anticline ، Folding styles ، Gachsaran formation ، Detachment folding
For management and planning valuable groundwater resources, it is very important to predict groundwater level and have a correct understanding about aquifer changes. In this paper for the first time, the wavelet Halt-Winters hybrid models (WHW) were used and tested for groundwater forecasting. A monthly data set of 16 years consisting of groundwater level fluctuations was used in two observation wells of Urmieh coastal aquifer. In the WHW, the dataset was converted into several sub-dataset with different time scales. Then, the sub-series were used in the HW model as inputs. Subsequently, the performance of the WHW model was compared with ARIMA, HW, and SARIMA as linear models and neural network models (ANN) and Support Vector Regression (SVR) as nonlinear models. The results showed that the NSE and RMSE values of the WHW model were upgraded up to 30% and 60% respectively, in comparison with linear models. The WHW hybrid model also has the same performance compared to nonlinear models. This research reflects that if there are multiple seasonal fluctuations in the groundwater time series, the performance of the WHW model compared with linear models will be more accurate.
Ali Mirarabi - HamidReza Nasseri - Farshad Alijani
Keywords : Halt-Winters ، Wavelet transform ، Neural network ، Support vector regression ، Groundwater
The Dehsheikh peridotite massif, as a part of the Esfandagheh ophiolitic mélanges, is located in the south of Baft, Kerman province. Structural analysis of the ophiolitic complexes play an important role in understanding geodynamics of the orogenic belts. In this research, structural elements of the eastern part of the Dehsheikh peridotite massif as well as prevailing deformational patterns of the area and its relation to the Zagros orogenic belt was studied. The chromitite folds, dunitic/pyroxenitic dykes and ductile to brittle shear zones (faults and magnesite veins) constitute the principal structures of this area. Structural evidence indicate two successive tentional/transtentional and dextral transpressional deformational phases. The early D1 deformation took place in a back-arc basin during ascending of the Dehsheikh Peridotite massif. This caused emplacement of the lithospheric mantle in the low crust level, and was accompanied by deformation of the chromitites and intrusion of the dunitic/pyroxenitic dykes. The next D2 right-lateral transpressional deformation with development of the brittle-ductile shear zones accommodated emplacement of this massif in the high pressure-low tempretaure Sanandaj-Sirjan metamorphic zone.
Sahra Jalalat Vakil-Kandi - Majid Shahpasandzadeh - Mahdi Honarmand - Hamid Ahmadipour
Keywords : Esfandagheh ophiolite mélanges ، Structural analysis ، Dehsheikh peridotite massif ، Zagros
The marbles of the Khalaj area constitute a part of the Mashhad metamorphic complex which was affected by three stages of deformation. Stretches of the boudins, which occurred during the first stage of the regional deformation, are measured in seven stations. The data are used for two dimensional finite strain analyses by Mohr circle. The results indicate the ellipticity of the strain ellipsoids vary between 1.05 to 1.36, and the maximum shear angle is between 4 to 20 degrees. These results are in agreement with field observations indicating dominant pure shear deformation during the first stage. This deformation is marked by generation of continuous folds and chocolate box boudins. These types of boudins were formed due to the stretching in two directions. Results of two dimensional strain analyses also show half to one time positive volume change during first stage of deformation.
Keywords : Khalaj ، Boudin ، Deformation ، Finite strain ، Mohr circle

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