فصلنامه زمین شناسی ایران
پیاپی 34 (تابستان 1394)

Identify the factors affecting changes in groundwater quality and pollution of water resources management is essential. The aim of this study was to identify factors affecting groundwater quality in Dezful- Andimeshk plain using multivariate statistical technique principal components analysis. For this purpose, 96 samples were taken from groundwater and parameters of EC, TDS, Ca2 +, Mg2 +, K +, Na +, CaCO3-, Cl-, SO4-, NO3- determined according to standard methods. Using principal components analysis, four main factors affecting the quality of groundwater comprising 88% of the total variance of the data, were extracted. Based on the results of factor analysis in Dezful- Andimeshk, first factor is related to groundwater interaction with the geological formations, sediment size and primary composition of groundwater. The second factor is related to the salts existing in Lahbari and Aghajari formations dissolved in groundwater. The third and fourth factors are related to wastewater effluent from agricultural activities and the sewage from rural and urban wells, respectively.

Kabir-Kuh and Chenareh anticlines are located in the Lurestan Province of the Zagros fold-thrust belt. The geometry and kinematic evolution of folds in the Zagros fold-thrust belt are controlled by thrust faults. In this paper, the geometry of the Kabir-Kuh and Chenareh anticlines is investigated in order to analyze their deformation style. To analyze the deformation style of these anticlines, five structural cross-sections were measured perpendicular to the axial surface trace of the anticlines. Based on geometric and kinematic analysis, Kabir-Kuh and Chenareh anticlines have a geometry similar to faulted-detachment folds with multi-detachment levels. The detachment level above which the folds formed is probably located in the Lower Paleozoic series. Also structural cross-sections represent an important contribution of the Dashtak Formation as intermediate level in the development of deformation in this part of the Lurestan Province.

Kinematic evidence of shear deformation in strain fringes of sphalerite mineral in an overturned limb of a fold structure are studied. Structural observation in Cretaceous rocks of Tiran Mine Area in west Esfahan, reveals a shear deformation in overturned limb of a hanging-wall anticline that has generated with reverse fault in the area. Orientation of strain fibers and their rotations in strain fringes of sphalerite minerals are used for determination of stress orientations and its changes during shear deformation process. This fabric indicates kinematic evolution of the overturned limb of a hanging-wall anticline and related reverse fault during folding. In this study, amount of stretching in strain fringes and their rotation are measured by object-centre path model.

The Plio-Quaternary volcanic cones in N-Qorveh have been comprised of three volcanic facies includings: pumiceous pyroclastics, fall-out scoria deposits and lava flows. The scoria clasts form the main volume of the cones. Because of this, we call them as “scoria cones”. Two types of enclaves are found in the scoria ejecta that are felsic or crustal xenoliths and mafic enclaves. Based on the type and abundances of the minerals, the latter enclaves are subdivided into three types: mica-apatite-hornblende (MAH), mica-apatite-olivine (MAO), and hornblende-apatite-pyroxene (HAP). Because of the textural and compositional similarities between minerals of the mafic enclaves and lava flows and scoria clasts, it must be stated that the mafic enclaves had been the cumulates that brought up the surface by the Strombolian-type explosive eruptions. Moreover, because of high-Mg contents in the mafic minerals and also the co-existences of volatile-bearing and volatile-free minerals, it can be stated that the forming magma of the scoria cones had been produced by the partial melting of the upper mantle due to the mantle metasomatism.

Magnesite deposit in Mazarseidali region is located 105 km South of Birjand in flysch basin in East Iran and within the Neh ophiolitic complex. The host rock for this deposit is serpentinized Upper Cretaceous ultramafic rocks. The results of geochemical analyses show that Mazarseidali magnesite is enriched in MgO and depleted in CaO and SiO2, and thus it can be used in refactory mineral industry. In order to evaluate the origin of Mazarseidali magnesite, oxygen and carbon isotope ratios for 8 samples were measured and the results show that δ13CVPDB and δ18OVSMOW values vary between -6.25 to -8.60 and +29.09 to +30.84 per mill, respectively. Considering the negative values for δ13C and comparing these with the values for similar deposits, it is determined that the source of carbonate (CO2) for the studied magnesites was from an organic carbon that was influenced by atmospheric carbonate. In addition, chemical alteration and serpentization of ultramafic rocks in the region and their transformation to serpentinite resulted in the release of Mg, that following the reaction with carbonates, led to the precipitation of magnesite.

Anbarkuh iron ore deposit is located near the Tutak complex 80 km East of the Safashahr and East of Fars province.This complex is a part of the southern Sanandaj-Sirjan zone. Tutak complex consists of: black mica schist, marble units and granite – gneiss. On the basis of geochemical studies, chemical composition of intrusive rocks are monzogranite, granodiorite and granite. Nature of magma is calc-alkaline and tectonic setting of magmatic – metamorphic Tutak complex is subduction (VAG). On the basis of field, petrography and geochemical studies, Tutak granite is S-type. Result of major, trace and REE elements indicated a genetic relationship between intrusion and metamorphic rocks.Fe-mineralization occurs as lense and vein in the carbonate and especially marbel unites and located near few kilometers of granite mass and gneiss. Mineralogically, the following association could be seen in the Fe-Anbarkuh ore: Hematite, magnetite, calcite, phlogopite, garnet, pyroxene and epidote. Fluid inclusion studies indicated that almost all the fluid inclusions are primary in genesis and two phases vapor-liquid. Thermometry of fluid inclusion, have been shown the average of homogenization temperature is 2600c and salinity is 18.5 wt% aq NaCl, also boiling evidences could be seen in the mineralized fluid. Fluid inclusion density ranges 0.8 to 1.0. Generally on the basis of field, petrographic and geochemical data, Fe- Anbarkuh deposit is formed in the retrograde skarn stage.

Existence of hot springs and geological evidences of north-west of Delijan area indicate that there is an important geothermal system in the depths of study area. In order to investigation geothermal of this area and delineation of geothermal structures with significant magnetic response, a ground magnetic survey was carried out over the hot springs which cover about 300 km2 in 2011. Necessary corrections and reductions were applied over the data. Then investigated the structures associated to the geothermal system using different magnetic map. It was revealed that a main magnetic anomaly in the area and estimated its depth and structural index using Euler method. Results of applying this method indicates a broad magnetic source almost in the depth of more than 2000 m. After Euler method, two other methods applyied over the data: forward modeling and 3D inversion using Model Vision software and Mag3D code, respectively were applied. Mag3D code using of the Li and Oldenburg algorithm gives the best answer based on iteration. Results of these methods show a broad magnetic source in the depth of between 2500 and 5000 m which can be interpreted as the heat source for geothermal system in the area. Results of this work have a good correlation with the known geological evidences.