نشریه علوم زمین
پیاپی 106 (زمستان 1396)

Mn-bearing veins of Jonub -ESehchangi are located 200 km southwest of Birjand, Southern Khorasan province (east of Iran). These veins are hosted by andesitic rocks of Eocene to Oligocene ages. Ore minerals identified by XRD method and mineralographic studies and are Pyrolusite, cryptomelane, psilomelane, hollandite, hematite and goethite, displaying colloform and open-space filling textures. Gypsum, halite, barite, carbonate and silica are the gangue minerals. Alteration zones, specifically argillic alteration zone, are developed along the vein within the andesitic wall rocks. Based on the mineralogical and geochemical data, the primary manganese minerals were Mn oxides and hydroxides, which have gradually been converted to psilomelane and hollandite, and finally pyrolusite. The average grade of Mn within the veins is 38.61%. Considering the average Mn/Fe ratio (about 48.55) in the Mn-bearing veins, as well as the positive correlation of Sr, U and Ba with Mn mineralization in this area show hydrothermal origin.

This study investigated the hydrogeochemistry and environmental water quality of rivers in Sarough watershed using the major ion chemistry and explored multivariate statistical methods for identification of processes which release the solutes in natural waters. Totally, 38 samples were collected along the main streams of the watershed. The mean concentrations of major cations (Na, K, Mg, Ca) and anions (Cl, NO3, CO3, HCO3, SO4) were measured about 15, 4.6, 10.5, 61, 30, 4.49, 89, 156 and 107 mg/l, respectively. The results indicated that the river waters in the Sarough watershed were neutral and fresh water in nature (mean values: pH=7.7 and TDS= 315.8 mg/l). Most of the water samples were categorized in hard and very hard water classes with mean value for TH=197 mg/l and were under-saturated regarding with major carbonates, sulfates and evaporate minerals in most of samples. The major water types were Ca–HCO3–SO4, Ca–Mg–CO3 and Ca–SO4–HCO3. The Na, Cl and NO3 concentration in all water samples fell within the accepted limit of national and international standards for drinking water. Nevertheless, Ca, Mg and SO4 content in some samples were higher than the maximum desirable limits. Schuler diagram showed that majority of the water samples were good and acceptable for drinking. Evaluating the quality of river water for irrigation purposes using Wilcox diagram and SAR, EC and RSC indices indicated that majority of the water samples were suitable for irrigation. The results of multivariate statistical techniques such as correlation coefficient matrix, CA and PCA indicated the strong association between Na-K-Cl-SO4 and Ca-Mg-CO3-TH. It was assumed that weathering of carbonates (limestone/dolomite formations, calcareous marl formation and travertine) in the area were common source of Ca, Mg and HCO3. Also, travertine springs were considered as active point sources which release these elements into the drainage system. Meanwhile, dissolution of halite and gypsum in red marl formations (lower part of Qom F. and Upper Red F.) were the main processes considered as the origin of Na, K, Cl and SO4 in river water of study area.

Evidence of at least ten different tectonic- controlled sedimentary basins can be recognized in the central part of the Alborz Mountains in the Middle part of the Alpine-Himalayan belt. They formed from Neoprotrozoic to recent time as the results of the relative plate motion in southwest of Asia in Tethyan realm. The basins include: (1) Prototethys Late Neo-Proterozoic to Early Ordovician epi-continental/platform basin; (2 Paleotethys Middle Ordovician to Devonian rift basin; (3) Devonian to Middle Triassic continental shelf basin; (4) Upper Triassic to Lower Jurassic foreland basin; (5) Shemshak back arc rift basin; (6) South Caspian carbonate platform basin; (7) Paleocene clastic sedimentary basin; (8) Karaj back arc basin; (9) Oligo-Miocene foreland basin; (10) Pliocene-Pleistocene intramontane basin. Each basin has its own unique history connected to the different stages of the birth, development and destruction of the Prototethys, Paleotethys and Neothethys Oceans in the Middle East region in the southwest of Asia.

Because of the important role of rock mass structural properties on its mechanical behavior, determining the qualitative and quantitative properties of has been a subject of intense research. In this regard, numerous techniques such as scanline surveying, cell mapping, and geologic structure mapping have been proposed. However, applying such field surveying techniques for rock mass properties involves spending substantial costs and times and high risks. Besides, due to the errors induced by operations, measurements, systematic errors, etc., the results of these techniques are not accurate and precise enough. Short-range digital photogrammetry is an state-of-art technique applied for surveying rock mass characteristics. Through this novel approach, rock mass surface is imaged, the obtained images are analyzed, and rock mass characteristics are determined, and finally, the technique is validated by comparing the obtained results with field surveys. In the present work, two digital photogrammetry based methods including digital image processing and laser-based imaging are implemented in rock mass characterization. The results show that short-range digital photogrammetry can be effectively employed in rock mass structure characterization. Moreover, this approach, unlike the existing traditional ones, involves low costs, high speed, and sufficiently accurate and precise results.

The Fahliyan Formation of Khami Group is hosting important hydrocarbon reserves in Iran and also is a main reservoir rock in the Abadan Plain oil fields which is Neocomian in age. In the studied wells its thickness is about 406 meters. In the Abadan Plain, the Fahliyan Formation transitionally overlies of the Garau Formation and its upper boundary changes into the Gadvan Formation. According to thin sections examinations prepared from cores analysis 11 microfacies is recognized by various facies including dolostone and dolomudstone of tidal flat, skeletal wackestone to packstone of the open and restricted lagoon, bioclastic intraclastic grainstones, peloid grainstone and coralinrudist-algae grainstone (boundstone) of the barrier setting and fine grained echinoderm rudist bearing deposits of the slope. high frequency of core facies belong to restricted and open marine lagoon deposits composed of benthic foraminifera, shell fragments and peliods. They are often observed in wackestone to packstone fabrics. The remained rock facies is composed of the bioclastic skeletal lime grainstones characterizing by large rudists and echinoderm debries which are interpreted to constitute the platform margin in this well. Tidal flat dolomudstone with a few bioclast contribute, which they often show moderate reservoir quality.

This paper analyzes in-situ stress field in the Asmari formation with in the complex structures of the Zeloi and Lali oilfields located in the Dezful embayment, SW Iran. The orientation of the maximum horizontal stress, SHmax is determined on the basis of compressive borehole breakouts and drilling-induced tensile fractures observed in eight oil wells, in which we focus on well-log based methods and drilling data to estimate stress magnitudes. In situ stress magnitude in studied fields obtained from 1D mechanical earth modeling in key wells. The maximum horizontal stress trend in this area is NE–SW in accordance with the World Stress Map however a stress perturbation has been recognized in some wells of the Lali field which is approximately perpendicular to the expected direction of the maximum horizontal stress. In situ stress magnitudes in the Lali oil wells are consistent with a strike-slip regime, while in the Zeloi oilfield, normal faulting regime is estimated. The observed strike-slip and normal faulting regime in the Lali and Zeloi wells respectively, Supports the idea that the role of overburden stress magnitude is higher than the horizontal stresses. Undoubtedly, the structural position of the wells, structural framework, faults location, fold geometry, pore pressure changes and mechanical properties of rocks are main factors and have played an important role in stress condition and in situ stress regime in these two hydrocarbon structure.

Magnetotellurics is an exploration method which is based on measurement of natural electric and magnetic fields of the Earth and is increasingly used in geological applications, petroleum industry, geothermal sources detection and crust and lithosphere studies. In this work, discrete wavelet transform of magnetotelluric signals was performed. Discrete wavelet transform decomposes signals into coefficients in multi-scales. Noise and signal portions are separable in multi-scale mode. Therefore, noise can be discarded in each scale; a threshold value is constructed dependent to coefficients of the scale then, the noise coefficients are discarded by thresholding the coefficients with the proper values. Proportional threshold values can be used to remove white and 1/f noise from time series. After that, a new signal is constructed using clean coefficients. This method is widely used in various fields of sciences from image processing to seismic studies. This work tried to show the effectiveness of this technique in decreasing pervasive noise from magnetotelluric signals. The results emphasized the advantageous effect of wavelet techniques in magnetotelluric data noise removing process.

During recent years, groundwater exploitation and thereby decreasing hydraulic head in the compressible sedimentary aquifer which is placed in the district 19 of Tehran have been caused noticeable land subsidence. The land subsidence has been damaging the infrastructures which have been being built in the south of Tehran Basin, especially in the district 19 of Tehran. A finite-difference groundwater flow model (MODFLOW) and a synthetic aperture radar (SAR) method have been used to estimate and predict the rate of land subsidence in this area, and help hydrogeologists manage the vital groundwater resource correctly. The data have been imported into the model, and the change of the amount of land subsidence and head have been obtained for 39 years. Then the available radar images have been processed. Afterwards, the head calibration and subsidence calibration have been done. The results of the calibrations confirmed the accuracy of the results obtained by the model. Finally, this study suggests that 118 mm of land subsidence and an 11.6 m piezometric head decline are likely to occur from 2014 until 2043.

Climate change and essentiality of the food security have motived scientists to try innovative approaches, among which, crop growth models can help to predict crop yield. In order to simulate tomato (Solanum lycopersicum) growth, phenological characteristics of a short-life variety of tomato were assessed. Phenologic characteristics included leaf area index (LAI), specific leaf area (SLA), crop height (H), leaf fresh and dry weight (LFW and LDW), and stem fresh and dry weight (SFW and SDW). These parameters were measured at four different times (i.e. 33, 45, 55, and 87 days after planting) during tomato growth and development. Fruit fresh and dry weight (FFW and FDW), harvest index (HI), and water efficiency () were measured at the end of the crop season. This study was done in a randomized complete block design with three levels of irrigation (i.e. at 48h (i1), 72h (i2), and 96h (i3)) in three replications. Irrigation treatment had significant effects on LAI1, LAI2, H2, FLW1, FLW2, DLW1, DLW2, DL2, FSW1, DSW1, DSW2, and DS2 at the 0.01 level, while its effect on SLA1, SLA2, H1, and FSW2 was significant at the level 0.05. Two-tailed correlations among characteristics were investigated and regression models developed for DFW. Dry fruit weight was simulated using both AquaCrop and regression models, separately. It was found that regression model could predict DFW of tomatoes under different treatment better than AquaCrop. It was also concluded that the phenologic characteristics measured at 55 DAP provide good criteria for predicting tomato fruit production.

Jurassic deposits a section in south of Zanjan contain various taxa of macro and microfloras. Six plant macrofossil species belonging to five genera of various orders such as Equisetales, Cycadales, Bennettitales, and Pinales (Coniferales) are identified. This section contains seventeen species of palynomorphs in which six spore species allocated to six genera, eight pollen species allocated to five genera, and three dinocyst species allocated to two genera are present. Based on the occurrence of Index fossils such as Ptilophyllum harrisianum, Nilssonia sp. cf. N. bozorga, and Equisetites sp. cf. E. beanii, an early Middle Jurassic (Aalenian-Bajocian) age suggested for these sediments. Therefore, these deposits considered to belong to the Dansirit Formation. Moreover, based on the stratigraphic distribution of index fossils of plant macrofossils, miospores, and dinocysts, three assemblage biozones recognized. These biozones are Nilssonia sp. cf. N. bozorga-Ptilophyllum harrisianum, Klukisporites variegatus-Cycadopites crassimarginis,and Pareodinia ceratophora-Nannoceratopsis triceras Assemblage Zone, respectively. All these biozones are comparable to the other Known Iranian biozones. Therefore, it is concluded that uniform environmental conditions are dominant through North, Central, and East Central of Iran during this interval. Furthermore, because of the occurrence of dinoflagellates, this area was located at the margin of Tethys Ocean.

Garesoo river basin in Doab-Merek, as studying area of this research, located in northwest of Kermanshah province in west part of Iran. There is long-term hydro climatologic data in this basin about rainfall, temperature, etc. (more than 50 years) and main river data (about 35 years). Due to intense fall down groundwater level and seasonal river drying, in the past 10 years .It was necessary that studies be done to the management water resources of region. Studies performed at first by linking MODFLOW to WEAP model with information and initial understanding of the geology and the others information of the area. The results were not satisfactory especially regarding the prediction runoff basin in outlet, despite the long term data. After these initial studies, and based on complete studying, it was cleared that complicated geological conditions with new Tectonics activities were key to the adaptation of the model to reality. In addition, geophysical surveys using radar approach showed that the fault is in match with the trend of river, and it can recharge river in wet season from hard rock water resources. Finally we achieved a good acceptance matching between calculated and observed discharge of river in Doab-Merek station with satisfactory results.

Main aim of this study is to determine relationship between lead and silver mineralized zones using the Concentration-Volume (C-V) fractal modeling and logratio matrix based on subsurface data in Mehdiabad Zn-Pb-Ag deposit, central Iran. First, Pb and Ag raw data were analyzed by statistical processes and their histogram have similar shape. Next, Geostatistical modeling was carried out for the Pb and Ag data and their distributions were estimated by ordinary kriging. Then, the C-V log-log plots were created for the Pb and Ag which show five populations as mineralized zones for both of them. Moreover, correlation between the Pb and Ag different mineralized zones were calculated by the logratio matrix. Overall accuracies (OAs) are higher than 90% for enriched and highly mineralized zones of these elements. However, these zones were validated with geological particulars which indicate that oxidized mineralization is situated in Black Hill (gossan) and Calamine mine and silver was enriched in cerussites. Results obtained by the fractal modeling represent that the main mineralization for Pb and Ag occur in the central and NW part of the Mehdiabad deposit especially in the oxidized mineralization.

Eocene magmatism with intermediate-acid tuffs and volcanic rocks, the host to the Nodoushan deposit in Yazd province, intruded by Oligocene early diorite and later granite plutonic rocks. The former involved in iron skarn (containing epidote and euhedral grossularite) to the north and northern part of the deposit, the latter contributed to fault-controlled Zn-Pb deposit. The structural features controlled both the mineralization and consequent alterations which ranged from silicification (central) to argillic (northern). Propylitic alteration and dolomitization considered the minor ones, the iron contamination of which could be provided by earlier iron mineralization. Sulfide minerals dominantly pyrite, sphalerite and galena followed by chalcopyrite and late stage copper minerals such as covellite, digenite, bornite, chalcocite. Oxide minerals developed to the depth of 40m as a result of faults. Sphalerite which is of high-Fe type was characterized by extensive chalcopyrite disease, the iron content of which provided by earlier iron concentration. The concentration of chalcopyrite exsolution along sphalerite margins as well as galena veinlets is due to the thermal shock of later stage hydrothermal fluids that deposited galena and chalcopyrite. Negligible fossil replacements indicate both mineralization and alteration. It was concluded that the Zn-dominant mineralization was deposited under the structural controlling faults which reflects part of its earlier iron mineralization.