Emplacement of granites in a transitional regime from volcanic arcs to post-collisional: an evidence from the Gabal El-Zeit block, Gulf of Suez region, Egypt
text
article
2015
eng
Gabal El-Zeit block at the western coast of the Gulf of Suez region in Egypt consists of two varieties of Precambrian granites, namely monzogranite and a peripheral zone of alkali granite. Both granitic varieties display moderate (60.1-68.5 wt%) and high silica (73.36-76.16 wt%) contents with high Na2O+K2O (7.21-8.61 wt%), respectively. The investigated monzogranite is calc-alkaline metaluminous whereas the alkali granite is peralkaline. The primordial mantle normalized plots of the Gabal El-Zeit granites indicate that they are characterized by Ba, Sr, P and Ti negative anomalies and a moderate to weak negative Nb anomaly. These geochemical features are similar to those expected for magmas extracted during post-collisional high-K granites from the late Neoproterozoic Arabian Nubian Shield. Tectonic discrimination diagrams show that the monzogranite is formed in a volcanic-arc setting, whereas the alkali granites is a characteristic of post-collisional tectonics. The geochemical characteristics of the monzogranite are consistent with magmatism derived by partial melting of a slightly LILE-enriched amphibole-bearing (i.e. hydrated) mafic source. However, the studied alkali granite perhaps was originated by fractional crystallization process from the monzogranite due to the relative depletion in the contents of Al2O3, MgO, CaO, Ba, and Sr with increasing silica which is also strengthened by other geochemical relationships. The collective field investigations and available geochemical data are consistent with a late- to post-collisional stage magmatism formed at the transition from volcanic-arc to within-plate tectonics. The monzogranite is ilmenite- and magnetite-bearing, either homogenous or as exsolution, whereas alkali granites contains homogeneous magnetite only. Therefore, the Fe-Ti content is a very useful tool to distinguish the two granitic varieties.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
182
202
https://jtethys.journals.pnu.ac.ir/article_2859_57a23db62e5c31ab29687e1d1f4b7d09.pdf
Prediction of heavy metals contamination in the groundwater of Arak region using artificial neural network and multiple linear regression
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article
2015
eng
Prediction of the heavy metals in the groundwater is important in developing any appropriate remediation strategy. This paper attempts to predict heavy metals (Pb, Zn and Cu) in the groundwater from Arak city, using artificial neural network (ANN) algorithm by taking major elements (HCO3, SO4) in the groundwater from Arak city. For this purpose, contamination sources in the groundwater were recorded based on 150 data samples and several models were trained and tested using collected data to determine the optimum model in which each model involved two inputs and three outputs. The results obtained (the comparison between the predicted and the measured data) indicate that Multilayer Perceptron Neural Networks model (ANN) has strong potential to estimation of the heavy metals in the groundwater with high degree of accuracy and robustness.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
203
215
https://jtethys.journals.pnu.ac.ir/article_2860_f4f50e254d8d319458eb7e6dda09d229.pdf
The Co, Ni, Cr and S mineralisations during serpentinization process in the Bou Azzer ore deposits (Anti-Atlas, Morocco)
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article
2015
eng
The serpentinization of the harzburgitic mantle section of the Bou Azzer Neoproterozoic ophiolite is studied by field mapping, structural observations, optical micrography, SEM and X-ray diffractometry, and relationships with Co, Ni, Cr and sulphides minerals are discussed. Serpentinization occurred in two major steps with, i) intra-oceanic pseudomorphic serpentinization materialized by the isotropic serpophite often associated with antigorite fibres preserving the primary form of olivine crystals, and ii) tectonic serpentinization with lizardite and chrysotile crystallisation during ophiolite obduction and deformation in relation with synkinematic granitoid intrusions (ca. 650-635 Ma). Brucite is fairly frequent as inclusions in the serpentine aggregates. The serpentinization processes led to the remobilization of S, Fe, Ni and Co included in the primary magmatic assemblage. The sulfide assemblage varies with the degree of serpentinization, with from low to high degrees: pentlandite + pyrrhotite + pentlandite + heazlewoodite (godlevskite); pentlandite + polydymite (or violarite); pentlandite + millerite, and polydymite + millerite. The presence of orcelite, the only stable Ni arsenide during serpentinization, reflects conditions of high activity of Ni and low activity of Fe in the fluids involved in serpentinization. The relative frequency of maucherite underlines the importance of arsenic in mantle-sourced fluids. The values of the arsenic activity could locally be as high as that of sulfur to form an immiscible As-rich liquid, which is the origin of As-rich paragenesis of high temperature.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
216
236
https://jtethys.journals.pnu.ac.ir/article_2861_a69e4682f69925dabed9fc7ca9d32b3a.pdf
Spatial and Temporal Analysis of the relation of urban heat island with vegetation cover in Tehran
text
article
2015
eng
The rapid change of land use and land cover in the Metropolitan area of Tehran has influenced the distribution pattern of land surface temperature (LST). In this study, a spatial autocorrelation analysis is adopted to process the spatial-temporal changes of LST and Normalized Difference Vegetation Index (NDVI) in Tehran during the period of 1987 to 2010. Global spatial autocorrelation analysis revealed that global Moran’s I of LST has increased while that of NDVI has decreased with time. While the newly hot clusters of LST were appeared in west and southwest of Tehran, the spatial extents of the old hot clusters have been increased. The Local Indicators of Spatial Association (LISA) analysis confirmed the intensifying and expansion of the hot clusters and weakening of the cold clusters of LST. The spatial pattern of LST and UHI expanded toward west and southwest of Tehran and UHI effect was intensified. Based on LISA analysis, the occurrence of increasing trend of HH cluster of LST is related to the decrease of HH cluster of NDVI in Tehran. Accompanying with decreasing of vegetation cover, green cover cooling effect also decreased, and consequently, UHI effect was intensified from 1987 to 2010. The results demonstrate the usefulness of spatial autocorrelation technique for analysis of spatial-temporal changes of UHI and green cover in urban areas. Ordinary Least Squares regression (OLS) and Geographically Weighted Regression (GWR) were used to investigate the relationships between LST and NDVI. The results indicate that the performance of the GWR model is significantly better than OLS.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
237
250
https://jtethys.journals.pnu.ac.ir/article_2862_2c2a96f7fc7d7d468b21adec072124d4.pdf
Microfacies and depositional basin analysis of Cretaceous deposite at Korkouh area
text
article
2015
eng
In order to microfacies studies of the Cretaceous deposits, a section called Korkouh was selected in Kerman province in Central Iran area. The Korkouh is on the Bidou Formation with angular unconformity and underlain by paleogene conglomerates with an erosional surface. The studied section basically contains lime and dolomitic limestone with the thickness of 146 meters with new fossils such as foraminifera, bivalves and bryozoans. In general, foraminifera obtained from Korkouh section indicate the existence of sediments in the age of Albian and Cenomanian. Based on microfacies studies on the section three facies belts have been identified in Karkouh section that include intertidal, lagoon and inner ramp. Studying of identified facies and comparing them with the present sedimentary environment showed that Korkouh outcrop facies have been deposited.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
251
259
https://jtethys.journals.pnu.ac.ir/article_2863_f531b803be6eb5a97eff9a9815247341.pdf
1D modeling of long-term morphodynamics: Application to the Adige River, Italy
text
article
2015
eng
The morphological river evolution at long-time (centuries and even millennia) and large spatial scale (watersheds of several square kilometres) can be described by means of simplified 1D models, able to simulate the variation of bed elevation and grain size composition at non-detailed scales, involving a reduced computational effort. The erosion and deposition phenomena acting along rivers can be modeled by a simplified approach based on the Local Uniform Flow hypothesis and on the instantaneous propagation of the water flow. Such an approach computes the sediment yield of large watersheds at long-time scale relatively quickly, taking into account the non-sorted granulometry of river systems. In the paper, a 1D simplified model is described and applied to the Adige River (Italy), in order to study the morphological evolution of the watercourse after a redesign of some cross sections in its lowland part. Local variations of river altimetry propagate downstream and upstream, in relation to the Froude number and to the changes magnitude. The results highlight the reliability of the code to simulate the long-term effects of human works in rivers at non-detailed scale. In addition, the outcomes of 1D simulation can be used as input data for detailed models (2D or 3D) to study local changes at shorter time scale.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
260
272
https://jtethys.journals.pnu.ac.ir/article_2864_4f5c37780f083878370ef4e17c766aaf.pdf
Hybrid ANN with Invasive Weed Optimization Algorithm, a New Technique for Prediction of Gold and Silver in Zarshuran Gold Deposit, Iran
text
article
2015
eng
Because of high cost of drilling and analysis of samples, it needs to predict gold and silvers based on pathfinder such as As, Sb, Cd, Pb and Zn and decrease the cost and time exploration project implementation. In this paper, the model based on a multilayer perceptron artificial neural network (MLP-ANN) optimized by invasive weed optimization algorithm (IWO) to predict of gold and silver in Zarshuran gold deposit, Iran is proposed. The IWO is used to decide the initial weights of the ANN. The ANN-IWO model is trained using an experimental data set to approximate the relation between Sb, Cd, Pb and Zn as inputs and gold and silver as output. Furthermore, the performance of the ANN-IWO model is compared with multiple linear regression (MLR). The results obtained indicate that the ANN-IWO model has strong potential to prediction of gold and silver with high degree of accuracy and robustness.
Quarterly Journal of Tethys
Payame Noor University
2476-7190
3
v.
3
no.
2015
273
285
https://jtethys.journals.pnu.ac.ir/article_2865_7f601223c226ec0095dc9790e30f7987.pdf