Geopersia
Volume:6 Issue: 1, Winter-Spring 2016

The protoliths of metamorphosed argillaceous rocks from the Garmichay area in the East Azerbaijan province of NW Iran were clayrich sediments of reworked nature, originating most likely from an andesite to andesite-basalt source and deposited in an active continental margin tectonic setting. The protoliths of the Garmichay metapelites experienced low to moderate chemical weathering. Andalusite, cordierite, biotite, and muscovite are produced due to metamorphism under low-pressure and medium-temperature conditions. Cordierite throughout the whole assemblages is altered to the pseudomorphs pinite. Some rock samples contain both andalusite and altered cordierite as porphyroblasts, whereas others contain only andalusite or altered cordierite. Pressure and temperature estimates indicate that pressure for metamorphism was in the range 1-2.5 kbar with temperature between 500-600C. Major oxides abundance show similar values in all analyzed samples, while concentration of some minor elements, especially zinc, show meaningful differences in rocks with different metamorphic mineral assemblages. The variations in the abundance of these minor elements may have played important role in the control of the mineral assemblages present.

The cold climate is a favorable parameter for the development of tension cracks and decrease of rock brittleness. Therefore, this paper attempts to investigate the Hamekasi porous limestone in order to predict the brittleness indices during freeze-thaw cycles. The freeze– thaw test was executed for one cycle including 16 h of freezing, and 8 h of thawing. The geo mechanical properties and brittleness indices (B1, B2, B3) of limestones were measured across freeze-thaw cycles from cycle 0 (fresh rock) to cycle 40. Statistical analyses, including simple and multiple regressions, were applied to identify those geomechanical parameters that are most influenced by the progression of freeze-thaw cycles and more appropriate for the brittleness prediction. Based on simple regression, all geomechanical properties including tensile strength ( t  ), uniaxial compressive strength ( c  ), P-wave velocity (Vp), porosity (n), and quick absorption index (QAI) (except dry density ( d  )) demonstrated good correlations with brittleness index (B3). The integrated prediction of brittleness is put forward to develop some models by multiple regression (MR) and artificial neural network (ANN) with some statistic parameters (R, RMSE, VAF and ME), based on all geomechanical properties examined in this research. It is concluded that models based on n, Vp and d  exhibited high performance according to the obtained statistic parameters. In spite of the fact that Vp has good correlation coefficient (R) with freeze-thaw cycles, and B3 (R2= 0.74, and 0.55, respectively) in simple regression, it does not have a prominent effect on B3 in MR models. Also, parameters with low correlation coefficient in simple regression ( d  =0.15) cannot improve the model performance in ANN methods.

A research program was conducted on different clay-bearing rocks selected from the Ilam, Sarpol-e Zahab and Tajarak regions (Iran) to predict their slaking characteristics. The new durability apparatus (nested mesh drums) separates disintegrated particles varying from > 25.4 to

Iranian Cenozoic magmatic belt, known as Urumieh-Dokhtar, is recognized as an important polymetallic mineralization which hosts porphyry, epithermal, and polymetallic skarn deposits. In this regard, multivariate analyses are generally used to extract significant anomalous geochemical signature of the mineral deposits. In this study, stepwise factor analysis, cluster analysis, and concentration– area fractal model have been used to delineate geochemical anomalies associated with skarn mineralization, based on Au, Cu, Pb, Zn, Ag, Mo, W, Sn, and As stream sediment data. These results indicate that the Urumieh-Dokhtar belt potentially hosts Au skarn deposits. The hybrid method combining the statistical analysis and C-A fractal model is an effective tool to identify geochemical anomalies.

Infiltration rate and hydraulic conductivity are immensely important parameters for evaluating the hydrology of subsurface environments. Specifically, in disposal wells schemes and in artificial recharge plans both properties must be correctly assessed to better analyze the performance of these installations. In a new research, tanker water and rainfall runoff were injected into a 22.5 m deep well dug in a 15 m thick dry overburden and the underlying impermeable marl bedrock (7.5 m) to evaluate the feasibility of using the well to store winter runoff in the overburden for recovery in the summer. Rates of rise and fall in the hydraulic head were measured, and infiltration rate in various depths were calculated. Also, hydraulic conductivity of the overburden was calculated using particle distribution curves of the overburden samples. Infiltration rate showed close correlation with the hydraulic conductivity. Maximum infiltration rate occurs at depths of 10-11 m; depth of 10 m is the most conductive interval. New findings have come out of this experience including 1. negative correlation between maximum head generated in a specific injection event and the rate of infiltration and 2. the important role of the contact zone between bedrock and the overburden in draining the injected water.

Nowadays the use of remote sensing and Geographic Information System (GIS) is one of the most powerful cost effective tools to identify and discover the available groundwater resources. In this paper, Lithological Units, Lineaments, Slope, Topography, Drainage density, Vegetation and Isohyets lines have been achieved by stations and through remote sensing and GIS techniques. All layers of different classes were initialized through hierarchical analysis to potential areas of groundwater and after modeling in GIS Environment, Mahdishahr zone was classified according to the potential groundwater basins. The results show that in the 7 reviewed criteria by the expertise and Analytical Hierarchy Process, geological criterion and lineaments with the relative importance of 0.33 and 0.22, respectively, have greatest importance and priority for potentiality of groundwater in the region. Also in the studied area, Quaternary Alluvium consisted of old and new terrace and river sediments have the highest relative importance and desirability and terrace resources and the elevated old and low height new Foothill Alluvial fans are considered as good potential areas of groundwater. Shemshak Sandstone formations and Barut with a high density lineaments and Tizkouh formation with the thick layers of limestone and Barut are also good areas for groundwater.

Important karstic aquifers exist in west and southwest of Iran. Mansour-Abad Karstic region is located in Shiraz, southwest of Iran. It supplies the drinking water for the whole area by 4 pumping water wells, some of which have water turbidity problem. The present research aims to assess the hydrogeochemistry and turbidity problem in the karstic water production wells. The EC varies between 703 (in well No.1) and 1096 µmohs/cm (in well No.4). All water wells have similar ion concentration trend, indicating the same origin. The dissolution of gypsum during dedolomitization process induces the transformation of dolomite to calcite in the study area, especially in well No.4. The concentrations of most trace elements in the study area are lower than the standard value. Bacteriological water parameters are outside the accepted limits recommended by WHO for drinking water. Wells No. 1, 2 and 3 have turbidity values greater than limited values for drinking water which is about 5 TU; therefore, only well No.4 is used as drinking water resource in the study area. Most probably, interference of clay mineral layers with groundwater flow is one of the main causes of turbidity in some wells.

This study aims to recognize effect of Ordinary Kriging (OK) and Inverse Distance Weighted (IDW) estimation methods for separation of geochemical anomalies based on soil samples using Concentration-Area (C-A) fractal model in Irankuh area, central Iran. Variograms and anisotropic ellipsoid were generated for the Pb and Zn distribution. Thresholds values from the C-A log-log plots based on the estimation methods revealed the presence of various geochemical anomalies within estimation variances which were compared in both methods. The comparison among the estimation variances for different geochemical anomalies based on the C-A fractal model indicated that the estimation variance is less in the OK method especially for extremely and highly Zn-Pb anomalies. The estimated variances for different Zn anomalies via OK and C-A fractal method are lower than fractal modeling obtained by IDW estimation. However, extremely and highly Pb anomalies due to OK method have estimation variances lower than IDW method. Based on the results, main Zn and Pb anomalies are situated in the NW part of the area.

Study of a late Late Santonian to Late Campanian hemipelagic succession from Abtalkh Formation at the Bahadorkhan section (Central Kopet-Dagh) enabled us to verify paleoecology changes based on planktonic and benthic foraminifera assemblage. Bahadorkhan section is consisted of calcareous shale, lime marl, marl, and a few dispersed chalky limestone beds. Upper and lower boundaries of Abtalkh Formation are conformable with Abderaz and Neyzar formations. Since foraminifera are proper tools for paleoecological investigations, we used them in three methods to analyze the changes of paleobathymetry: 1) Van der Zwaan’s equations of determining depth and method (the ratio of planktonic foraminifera to benthic), 2) Leckie''s morphotype model, and 3) investigating the changes of benthic foraminifera and the ratio of agglutinated benthic foraminifera to the utilized calcareous benthic foraminifera. Trox model (the ratio of epifaunal to infaunal (Ep/In)) was also used with the goal of identifying oxygen level and nutrients. According to the statistical counting, four stages of changes in depth and environmental conditions in this section with age range of late Late Santonian- Late Campanian were observed. According to the analysis, in the Early Campanian, P/B ratio and infaunal benthic are high which indicates the high level of water and eutrophic environment. In such an environment, nutrient and oxygen levels are respectively high and low. Then, at end of the Early Campanian and the beginning of Middle Campanian, water level decreases, and the environment moves toward oligotrophic conditions. During Middle Campanian and the early Late Campanian, water level increases again. Finally, during Late Campanian and along with the change of lithology to Neyzar Formation sandstones, we will witness the decrease of P/B ratio, water level drop, oxygen level increase, and nutrient decrease.

A succession of Late Campanian- Early Maastrichtian is analyzed from Gurpi Formation with regard to the calcareous nannofossils. Correlation Matrix was applied for the first time to the entire nannofossil assemblage to reconstruct environmental conditions. A detailed quantitative calcareous nannofossil analyses is performed on samples in order to further investigate the climate events, and interpret changes of surface water temperature. The calcareous nannofossil assemblage is divided into 3 groups as cold, cool and warm water taxa. Although cold water taxa (Ahmuellerella octoradiata and Gartnerago segmentatum) are rare (less than 1%), cool (Eiffellithus turriseiffelii, Prediscosphaera cretacea, Micula staurophora, Zeugrhabdotus spp., Arkhangelskiella cymbiformis, Biscutum constans, Tranolithus orionatus and Lucianorhabdus cayeuxii) and warm (Watznaueria barnesae, Uniplanarius trifidus, Uniplanarius sissinghii, Ceratolithoides spp. and Broinsonia spp.) water taxa are more frequent. The number of warm water taxa is higher than the number of cool water taxa and a reverse trend can be observed between them. Concerning the temperature index (TI), four important trends of climate variability from warmer to cooler phases (two cooling phases and two warming phases) have been documented at the studied interval. According to the recorded data, two pronounced cooling event are observed at Late Campanian and Early Maastrichtian, respectively.