Iranian Journal of Geology
Year:2019 | Volume:12 | Issue:48 |Papers Count:9

Wetlands are the most important and yet vulnerable environmental resources which are vital as water resources to agriculture, springs, ground water recharge and ecology. Therefore, the management and restoration of the wetlands are of great importance and require hydrogeological scrutiny. Barm-e-Shour is one of the most important wetlands in Khuzestan province and is utilized for drinking and agricultural purposes. The wetland is situated on Gachsaran evaporate formation. There are no permanent surface inflows, yet the wetland maintains a steady reservoir, despite the recent drought and water supply limitations. Water and recharge origin which require calculating hydrogeological balance have not been studied so far. To achieve this goal, the iso-depth map, annual water level fluctuation, catchment area and different parameters of water balance were determined. The maximum depth during the dry season was about 3 meters. According to hydrogeological surveys the water balance was positive so that the yearly inflow of water was about 10912 m3 indicating the main role of ground water in wetland recharge. Considering the karst development and isotopic results, carbonates of the Asmari anticline is the most probable source of Barm-e-Shour wetland water.

Pattern recognition methods are able to identify the hidden relationships between exploration data, especially in the case of limited number of data. The geochemical distribution patterns of the elements are identified and generalized using these methods. Multilayer perceptron, MLP, is one of the pattern recognition methods which is used for the estimation of geochemical element concentrations in mineral deposit studies. In the current study, multilayer neural network was used to estimate the concentration of geochemical elements based on 1755 surface and borehole samples, analyzed by ICP. Fuzzy c-means, FCM, clustering algorithm was used to increase the neural network estimation accuracy. The optimal number of clusters in the dataset was identified by validation indices and was used to design estimator. The clustering data on average showed an increase of 13% accuracy compared to normal mode. The average accuracy was increased from 75 percent to 88 percent. Elements with the lowest estimation accuracy showed an acceptable increase on the estimation accuracy by using clustering data. Mean squared error was 0. 079 using all data and decreased to 0. 025 while using hybrid developed method.

With the east– west exposure trend, Peshtasar basalts are in the sedimentary basin of Moghan (Talesh structural zone), in the northwest of Iran. The Peshtasar complex lithologically includes basalt, andesitic basalt or basaltic andesite, megaporphyric andesite, leucite tephrite and volcanic breccia. The main constituent minerals are plagioclase, clinopyroxene, and iddingsitized olivine in basalts and plagioclase megacryst, clinopyroxene, and leucite in tephrite. The results of the microprobe analyses of clinopyroxene reveal the diopside composition. Clinopyroxenes of Peshtasar basalts have igneous nature originated from alkaline and continental magmatic serries. The results of termobarometry studies indicate the crystallization range from 800-1200 degrees centigrade and crystallization pressure less than 5 kb. There was no water in composition of the parent magma of these rocks. The titanium contents of clinopyroxenes were low, indicating the presence of titano-magnetite (opaque minerals) in the rock. The ferric iron values in clinopyroxenes represents a high oxygen fugacity of magma.

In this research, present-day tectonic stress field affecting North Tabriz Fault and surrounding areas was reconstructed by using 37 compiled earthquakes focal mechanism from various sources. Triangle diagrams were used to determine the sense of the earthquakes focal mechanism. The sense of these data varies from strike-slip to thrust regime. Stress separation process was applied on data set for separation of the various tectonics regimes from a poly-phase system to obtain reduced stress tensors. This was done because most of the data participated in them and reconstructed stress fields completely cover the stresses affecting the region. The results of inversion analysis and internal separation of the data set show three stress regimes acting in this region. Considerably, all three stress regimes have a horizontal pressure stress with NW-SE to NNW-SSE trend. The direction of maximum pressure in each first, second and third regimes is 09/329, 28/310 and 03/138, respectively.

Fluorite mineralization in Kamar Posht mine, east of Central Alborz, is mostly occurred in dolomitic limestone rocks of the Elika Formation. The aim of this current research was to recognize the types of breccia and dolomite based on microscopic studies (transmitted and cathodoluminescence light) and ore fabric and texture applying to the genesis of this deposit. Using the above methods combined with time-space relationship between dolomites and fluorite led to recognition of 2 main groups of dolomites including (1) pre-mineralization dolomicrites without luminesce in the matrix of host dolomitic limestone and (2) dolomicrosparite-dolosparites associated and coeval with mineralization that show red to orange-yellow luminescence color. Pre-mineralization dolomicrites introduced as shallow buried diagenetic-type, whereas syn-mineralization dolomicrosparite-dolosparites interpreted to form due to re-crystallization of primary dolomicrites of host rock and/or precipitation of hydrothermal solution (basinal brine) causing dolomitic alteration. Dissolution-collapse and faults breccias dominated over diagenetic breccia and were main features of mineralization in Kamarposht mine. They were interpreted as evidence of epigenetic origin of fluorite mineralization in high-grade zones of the KamarPosht mine. They were probably formed as a result of post-diagenetic processes (tectonic and basinal brines) on dolomitic limestone host rocks overlaying clastic rocks of Shemshak group.

In order to identify the main effective factors in the Sonajil Cu-Au porphyry-epithermal deposit, remote sensing, mineralogical and geochemical studies were carried on the deposit. After removing vegetation and topographic features by Normalized Difference Vegetation Index (NDVI), solar radiance, instrumental errors and albedo effects by Log Residual (LR), Band Ratio (BR), False Color Composite (FCC), Principal Component Analysis (PCA) and Mixture-Tuned Matched-Filtering (MTMF) were used to reveal main alteration zones of the study area. The phyllic, advanced argillic and propylitic altered rocks were identified and the results were validated by field and mineralogical studies. Also, geochemical data showed microdiorite, and shoshonite composition and also post-orogenic tectonic setting of the Sonajil porphyry-copper deposits. Eventually, the faulting density, composition, and the depth of mineralization were the affecting factors on the Sonajil deposit mineralization.

Eocene-Oligocene intrusive stock of basic bodies of south Germi are intruded into and cropped out in Eocene basaltic lavas. Studied gabroic intrusive rocks generally show granular texture with assemblages characterized by Cpx + Pl + Bi + Amph. Pyroxenes have augitic composition, plagioclase have labradoritic and amphiboles have pargasitic compositions. The studied amphiboles show (Na+K)A ≥ 0. 5 with variable amount (0. 57-0. 99), Fe+3 content ranges from 0. 00 to 1. 17, also AlVI ranges from 0. 00 to 0. 68 and AlVI

Shotori active fault zone (in the northern end of Nayband fault) has a dextral strike-slip mechanism with a revers component. Landsat image studies show that this fault is uncontinuous and segmented. In this research, based on fault geometric discontinuity, two segments, were determined on both the northern (with trend of N40w) and southern segments (with trend of N20w). Both of them are reverse with a right lateral slip movement component. The southern segment is the most active segment, based on fractal earthquake and fractal fractures (Ds= 1/60, DN=1/73) and earthquakes (Ds=0/43, DN=0/68) morphotectonic parameters such as river slope indicator (SLs=1703/27, SLN=1526/7), sinuosity river channel (SS=1/24, SN=1/27), the V ratio (Vs=0/7, VN=0/9) and structural and seismic data. The most frequent recorded earthquakes and the biggest registered earthquake with a magnitude of 7. 4 on the Richter scale have taken place in the southern segment. This indicates a high potential of seismic activity on this segment of the Shotori fault.