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K. Bazargani-Guilani M. A. Nekouvaght Tak† M. Faramarzi 《Australian Journal of Earth Sciences》2013,60(3):297-307
A multidisciplinary study including geology, petrography and reconnaissance isotope analyses has been carried out on the Reza-Abad, Reza-Barak and Heydar-Abad Pb–Zn deposits, hosted by different types of Cretaceous dolostone and limestone in northeast of the city of Shahmirzad in the central Alborz region of Iran. Dolostones are dominated by replacement dolomite with minor dolomite cements. The studied deposits are strata-bound vein and breccia type and are associated with tensional faults and fractures. Mineralisation occurs in veins and in karstic and tectonic breccias. Hypogene minerals include galena with minor sphalerite and pyrite. Supergene minerals comprise Fe-oxide, cerussite, anglesite, plattnerite, minimum and mimetite. Calcite, quartz and dolomite form gangue minerals. The δ18O and δ13C values of dolomites vary between –5.8 and +2.1‰ VPDB and between 0.0 and +2.9‰ VPDB, respectively. Isotopic and previous fluid inclusion studies suggest that deposits formed from brines (15–25 wt.% NaCl equiv.) at temperatures of 70 to 110°C. Lead isotope data are homogeneous and represent upper crust source. This study provides an insight into the ore-forming processes of MVT deposits in the northeast Shahmirzad region. 相似文献
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The measured sky twilight brightness of a site is believed to be connected with main factors such as geographical latitude, elevation of the site above sea level, the season of observations and the aerosol pollution. These factors may decrease the sky twilight brightness and thus improve the crescent visibility limits. The effect of these factors on the visibility conditions to see the new Moon are investigated in the present work. The results show that the visibility conditions has improved at sites situated at higher northern geographical latitudes and higher elevation above sea level. The conditions to see the new Moon in winter season is better than the summer season. The aerosol pollution has a great effect on the visibility of the new Moon at sun's depression 5°, while for sun's depression greater than 5° the aerosol pollution has a small effect. 相似文献
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Application of WetSpass model to estimate groundwater recharge variability in the Nile Delta aquifer
Asaad M. Armanuos Abdelazim Negm C. Yoshimura Oliver C. Saavedra Valeriano 《Arabian Journal of Geosciences》2016,9(10):553
Long-term groundwater recharge from rainfall in the Nile Delta is needed as an input for integrated groundwater modelling in the Nile Delta aquifer for more accurate simulation. The main objective is to estimate the spatial and temporal variation of groundwater recharge from rainfall in the Nile Delta aquifer. Water and Energy Transfer between Soil, Plants and Atmosphere under quasi-Steady State (WetSpass) model parameters were identified for the Nile Delta based on the available meteorological data for the area collected in 1991 and 2000. The collected data were rainfall, temperature, wind speed and evapotranspiration. Geomorphological characteristics, such as soil type, topography, groundwater depth and slope, were also collected as input data for the WetSpass model. ENVI software was used to come up with land use classification based on available land cover images of the Nile Delta for 1972, 1984, 1990, 2000 and 2009. The WetSpass model was calibrated by comparing the simulated groundwater recharge with the calculated one by using the water balance equation model. The results indicated close agreement in groundwater recharge between the two model outputs with R 2 of 0.99 and 0.94, while the root-mean-square errors (RMSEs) were 4.86 and 9.39 mm for 1991 and 2000, respectively. The WetSpass model was then applied in respect of 1970, 1980, 1990 and 2010 for the purpose of validation. The overall RMSE and R 2 for the 6 years were 8.83 mm and 0.88, respectively. The results of the WetSpass calibrated model provide information to support integrated groundwater modelling. The results reveal that WetSpass works well in simulating the components of the hydrological balance in the Nile Delta. 相似文献
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Maryam Moridnejad Stewart Cameron Asaad Y. Shamseldin Floris Verhagen Catherine Moore Bruce W. Melville Nick Dudley Ward 《Ground water》2020,58(4):661-673
The Ngongotaha Stream was used as a case study to assess the applicability of fiber optic distributed temperature sensing (FODTS) to identify the location of springs and quantify their discharge. Thirteen springs were identified, mostly located within a 115 m reach, five discharged from the right bank and eight from the left bank. To quantify groundwater discharge, a new approach was developed in which the one-dimensional transient heat transport model was fitted to the FODTS measurements, where the main calibration parameters of interest were the unknown spring discharges. The spatial disposition of the groundwater discharge estimation problem was constrained by two sources of information; first, the stream gains ∼500 L/s as determined by streamflow gauging. Second, the temperature profiles of the left and right banks provide the spatial disposition of springs and their relative discharges. FODTS was used to measure stream temperature near the left and right banks, which created two temperature datasets. A weighted average of the two datasets was then calculated, where the weights reflected the degree of mixing between the right and left banks downstream of a spring. The new approach in this study marks a departure from previous studies, in which the general approach was to use the steady-state thermal mixing model (Selker et al. 2006a; Westhoff et al. 2007; Briggs et al. 2012) to infer groundwater discharge, which is then used as an input into a transient model of the general form of equation to simulate stream temperature (Westhoff et al. 2007). 相似文献
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Metacarbonate rocks (including marble and skarn deposits) at Bahrah area are confined to a Precambrian island-arc suite made up mostly of massive basalts and volcaniclastics aligned in a NE-trending belt. The marbles are either pure (almost made up of calcite) or contain considerable amounts of tremolite, actinolite, epidote, and diopside. Garnet-bearing rocks at Bahrah area are classified into garnetiferous marble and skarn calc-silicate assemblages that are described here for the first time. The calc-silicates become more abundant when the marble becomes interbedded with foliated metabasalt. Such contact is delineated by an epidote zone of variable thickness. Microscopically, the skarns are enriched in Ca-bearing minerals such as grossular garnet, epidote, titanite, diopside, and augitic salite. There are evidence that calc-silicate skarns were formed due to a thermal effect of a concealed underground shallow granitic intrusion. The basaltic rocks furnished Mg2+, Fe2+, Ti4+, and Al3+ that were first concentrated in the epidote zone. This was followed by pervasive replacement of epidote by large idiomorphic garnet (grossularite) that attains up to ～1.5 cm wide. It is evident that diopside is earlier than garnet with no replacement fabrics between the two minerals. Two types of titanite (sphene) can be distinguished: The first is secondary in the metabasalt host where titanite develops after titanomagnetite during regional metamorphism (i.e., metamorphic). On the other hand, the second type of titanite is found in the garnet-bearing calc-silicate skarn where it is typically euhedral with no link to any opaque phase and it is believed to be formed due to the event of superimposed thermal metamorphism (i.e., metasomatic). There are several evidence of the thermal metamorphic effect such as distinct granoblastic and annealing textures and K-metasomatism and formation of phlogopite at the expense of tremolite in the marble, in addition to poikiloblastic hornblende in the metabasalt host with distinct recrystallization. Also, there are some evidence of shearing such as brecciation along microshear planes, microfolding, introduction of fine euhedral pyrite, and presence of injected silica postdating crystallization of garnet in the calc-silicates. 相似文献
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The Jabal Al-Hassir ring complex is located between latitudes 19°21′ and 19°42′ N, and longitudes 42°55′ and 4312′ E, Southern Arabian Shield. It is an alkaline to highly fractionated calc-alkaline granite complex consisting of an inner core of biotite granite followed outward by porphyritic sodic-calcic amphibole (ferrobarroisite) granite. U–Pb zircon geochronology indicates that the Jabal Al-Hassir ring complex was emplaced at ca. 620 Ma. The granites display highly fractionated geochemical features (i.e., Eu/Eu* = 0.05–0.35; enrichment of K, Rb, Th, U, Zr, Hf, Y and REE; depletion of Ta, Nb, Ba, Sr, P, Eu, and Ti). Jabal Al-Hassir granites are post-collisional plutonic rocks and contain abundant microcline perthite and sodic-calcic amphibole, sharing the petrological and chemical features of A2-type granites. Sri values range from 0.70241 to 0.70424, are similar to those expected for magmas extracted from a Neoproterozoic depleted source and much lower than what would be expected, if there was minor involvement of pre-Neoproterozoic continental crust. The geochemical characteristics indicate that their magma was most plausibly represented by partial melting of juvenile lower crust following the collision between East and West Gondwana at the final stage of the Arabian Shield evolution. The data presented in this study are therefore consistent with an intraplate, post-collisional magmatism formed at the beginning of a transition from convergent to extensional tectonics. 相似文献
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An RES-Based Model for Risk Assessment and Prediction of Backbreak in Bench Blasting 总被引：1，自引：1，他引：0
F. Faramarzi M. A. Ebrahimi Farsangi H. Mansouri 《Rock Mechanics and Rock Engineering》2013,46(4):877-887
Most blasting operations are associated with various forms of energy loss, emerging as environmental side effects of rock blasting, such as flyrock, vibration, airblast, and backbreak. Backbreak is an adverse phenomenon in rock blasting operations, which imposes risk and increases operation expenses because of safety reduction due to the instability of walls, poor fragmentation, and uneven burden in subsequent blasts. In this paper, based on the basic concepts of a rock engineering systems (RES) approach, a new model for the prediction of backbreak and the risk associated with a blast is presented. The newly suggested model involves 16 effective parameters on backbreak due to blasting, while retaining simplicity as well. The data for 30 blasts, carried out at Sungun copper mine, western Iran, were used to predict backbreak and the level of risk corresponding to each blast by the RES-based model. The results obtained were compared with the backbreak measured for each blast, which showed that the level of risk achieved is in consistence with the backbreak measured. The maximum level of risk [vulnerability index (VI) = 60] was associated with blast No. 2, for which the corresponding average backbreak was the highest achieved (9.25 m). Also, for blasts with levels of risk under 40, the minimum average backbreaks (<4 m) were observed. Furthermore, to evaluate the model performance for backbreak prediction, the coefficient of correlation (R 2) and root mean square error (RMSE) of the model were calculated (R 2 = 0.8; RMSE = 1.07), indicating the good performance of the model. 相似文献
18.
Twana Kamal Haji Asaad Faramarzi Nicole Metje David Chapman Farough Rahimzadeh 《国际地质力学数值与分析法杂志》2020,44(3):418-431
The accurate modelling of gravity is of crucial importance for a variety of issues including, but not restricted to, the identification of buried objects. Gravity is an unbounded problem, which causes challenges when applying numerical models, i..e.., it results in computational difficulties when specifying the relevant boundary conditions. In order to address this, previous research has tended to generate artificial boundary conditions, e.g., truncating the simulated domain and adding many unrealistic zero-density layers, which introduces more unknown parameters and unnecessarily excessive computational time. In order to overcome such inaccuracies, this paper proposes an innovative development of the finite element modelling technique, which represents a step change in the field of gravity forward modelling. A comprehensive formulation of an infinite element to reproduce the far-field boundary effect using only one layer of infinite elements is presented. The developed model considerably reduces the computational time while obtaining high degrees of accuracy. The model is validated against the exact solution of the problem, and its results show an excellent performance. The proposed method can significantly improve the postprocessing and interpretation stages of data analysis relevant to micro-gravity sensors. The new method is applied to subsurface civil engineering although its applicability is manifold. 相似文献
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