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51.
Yves Missenard Omar Saddiqi Jocelyn Barbarand Pascale Leturmy Geoffrey Ruiz Fatima‐Zahra El Haimer Dominique Frizon de Lamotte 《地学学报》2008,20(3):221-228
In North Africa, the High Atlas belt culminates at more than 4000 m. In Morocco, recent work shows that a lithospheric thinning explains about 1000 m of the mean topography, the remaining topography being related to crustal shortening. We combine regional geology with new apatite fission‐track (AFT) ages to constrain the timing of these events in the Marrakech High Atlas (MHA). In the inner belt, 10 AFT ages are comprised between 9 ± 1 and 27 ± 3 Ma. These Neogene ages indicate that the MHA underwent significant denudation during that time. In the southern foreland domain of the belt, three samples give scattered AFT ages between 27 ± 2 and 87 ±5 Ma. Geological evidences allow us to constrain the age of a major denudation event during Middle Miocene age. We propose that it is linked to the thermal doming highlighted in the whole Moroccan Atlas domain. 相似文献
52.
A genetic algorithm (GA)-based neuro-fuzzy approach is used for identification of geochemical anomalies by implementing a Takagi, Sugeno and Kang (TSK) type fuzzy inference system in a 5-layered feed-forward adaptive artificial neural network. This paper investigates the effectiveness of GA-based neuro-fuzzy for separating zone dispersed mineralization (ZDM) from blind mineralization, and its application for identification of geochemical anomalies in the arid landscape of the Lut metallogenic province in eastern Iran. Other classification algorithms such as metallometry, zonality, criteria, and back-propagation artificial neural network classifiers are also used for comparison. The genetic operators are carefully designed to optimize the artificial neural network, avoiding premature convergence and permutation problems. The results show that the GA-based hybrid neuro-fuzzy model can provide accurate results in comparison with those results obtained by other techniques. Neuro-fuzzy and GA-based neuro-fuzzy techniques appear to be well-suited for routine exploration geochemistry applications. In conjunction with statistics and conventional mathematical methods, hybrid approaches can be developed and may prove a step forward in the practice of applied geochemistry. 相似文献
53.
The Bayesian approach is an effective method of identifying the probability of mineralogical and geochemical type (MGT) mineralization of trace elements in galena, pyrite and other distributions in ore mineralization. Monomineralic samples have been identified using a computer-based Bayesian method and exploration geochemical techniques of Au deposits for MGT. In order to employ the method, a data bank was used consisting of the results of analysis of more than 12,000 monomineralic samples collected from the main hydrothermal Au deposits in Tajikistan (a territory of CIS). The Bayesian approach applied to geochemical data, such as posterior probabilities and discriminant analysis, provide numerical and graphical means through which the relationships between the trace elements and samples can be studied. The method used here, along with GIS, to find MGT can be used as geochemical indicators of regions with Au mineralization. The results of analyzing 100 monomineralic samples of pyrite from the Au–Ag Shkolnoe deposit (Tajikistan) show a multi-MGT anomaly superposition which is a combination of three MGT: (1) Au–Ag type (85% and more), (2) Au–sulfide-polymetallic type (46%), and (3) Au–sulfide type (40%). Mineralogical and geochemical maps (MGM) can be drawn based on results of MGT anomalies in a GIS environment. These maps can replace traditional metallogenic maps. The advantage of MGM substitutions is that a qualitative tool is replaced by a quantitative one. This helps one to make optimal managerial and more economical decisions. 相似文献
54.
Over the past decade, land development activities on hillsides in northern Utah have resulted in a significant increase in
landslide activity throughout the region. The majority of recent landslides are shallow and they occurred on cut gentle slopes
especially during spring and early summer due to snowmelt induced elevated groundwater tables. The geologic material documented
at numerous landslide sites is a soft gray-green completely decomposed Norwood Tuff. The present study addresses the mechanism
of a shallow landslide in completely decomposed Norwood Tuff based on field, laboratory and numerical investigations. Detailed
slope surface geometry obtained from laser-scan surveys together with strength and stress–strain parameters derived from laboratory
triaxial tests on undisturbed samples of completely decomposed Norwood Tuff collected from the landslide site are employed
with finite-element modeling to examine the effects of ground surface deformation patterns on the yielding behavior of the
slide mass. The numerical results indicate a gradual retreat of the yield zone with progressive landslide deformation, which
eventually becomes concentrated within the accumulation zone of the landslide, compared to a well-developed yield zone within
the entire slide mass at the onset of landslide movement. Limit equilibrium stability analyses along potential sliding surfaces
of extent limited within the yield zone of the displaced slide mass produce lower safety factors than an analysis based on
the original sliding surface comprising the entire slide mass. 相似文献
55.
Data inadequacy is a common problem in designing or updating groundwater monitoring systems. The developed methodologies for the optimal design of groundwater monitoring systems usually assume that there is a complete set of data obtained from existing monitoring wells and provide a revised configuration for the system by analyzing the current data. These methodologies are not usually applicable when the current groundwater quantity and quality data are highly sparse. In this paper, a new simulation–optimization approach based on Bayesian maximum entropy theory (BME) is proposed for revising spatial and temporal monitoring frequencies in a sparsely monitored aquifer. The BME is used to simulate the spatial and spatiotemporal variations of groundwater indicators, incorporating the space/time uncertainties due to insufficient data. Comparing the obtained estimations with observations, the best BME model was selected to be linked with an optimization model. The main goal of optimization was to find out the spatial and temporal sampling characteristics of the monitoring stations using the concepts of Entropy theory and a groundwater vulnerability index. The results show the BME estimations are less biased and more accurate than Ordinary Kriging in both spatial and spatiotemporal analysis. The improvements in the BME estimates are mostly related to incorporating hard (accurate) and soft (uncertain) data in the estimation process. The applicability and efficiency of the proposed methodology have been evaluated by applying it to the Tehran aquifer in Iran which is suffering from high groundwater table fluctuations and nitrate pollution. Based on the results, in addition to the existing monitoring wells, seven new monitoring stations have been proposed. Few stations which potentially can be removed or combined with other stations have been identified and a monthly sampling frequency has been suggested. 相似文献
56.
Quantifying the uncertainty of semiarid flash floods using generalized likelihood uncertainty estimation 总被引：1，自引：0，他引：1
This paper aims to address the question of how the parameter uncertainty associated with a mixed conceptual and physical based rainfall-runoff model (AFFDEF) has influences on flood simulation of the semiarid Abolabbas catchment (284 km2), in Iran. AFFDEF was modified and coupled with the generalized likelihood uncertainty estimation (GLUE) algorithm to simulate four flash flood events. Analysis suggests that AFFDEF parameters showed non-unique posterior distributions depending on the magnitudes and duration of flash flood events. Model predictive uncertainty was heavily dominated by error and bias in soil antecedent moisture condition that led to large storage effect in simulation. Overall, multiplying parameter for the infiltration reservoir capacity and multiplying parameter for the interception reservoir capacity along with potential runoff contributing areas were identified the key model parameters and more influential on flood simulation. Results further revealed that uncertainty was satisfactorily quantified for the event with low to moderate flood magnitudes while high magnitude event exhibited unsatisfactory result. 相似文献
57.
Kayhomayoon Zahra Ghordoyee Milan Sami Arya Azar Naser Kardan Moghaddam Hamid 《Natural Resources Research》2021,30(6):4165-4185
Natural Resources Research - In this study, a new 3-stage approach that consists of clustering, simulation, and optimization stages is proposed for the simulation of groundwater level (GWL) in an... 相似文献
58.
Determination of water balance equation components in irrigated agricultural watersheds using SWAT and MODFLOW models : A case study of Samalqan plain in Iran 
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下载免费PDF全文 Increasing water demands,especially in arid and semi-arid regions,continuously exacerbate groundwater as the only reliable water resources in these regions.Samalqan watershed,Iran,is a groundwater-based irrigation watershed,so that increased aquifer extraction,has caused serious groundwater depletion.So that the catchment consists of surface water,the management of these resources is essential in order to increase the groundwater recharge.Due to the existence of rivers,the low thickness of the alluvial sediments,groundwater level fluctuations and high uncertainty in the calculation of hydrodynamic coefficients in the watershed,the SWAT and MODFLOW models were used to assess the impact of irrigation return flow on groundwater recharge and the hydrological components of the basin.For this purpose,the irrigation operation tool in the SWAT model was utilized to determine the fixed amounts and time of irrigation for each HRU(Hydrological Response Unit)on the specified day.Since the study area has pressing challenges related to water deficit and sparsely gauged,therefore,this investigation looks actual for regional scale analysis.Model evaluation criteria,RMSE and NRMSE for the simulated groundwater level were 1.8 m and 1.1%respectively.Also,the simulation of surface water flow at the basin outlet,provided satisfactory prediction(R2=0.92,NSE=0.85).Results showed that,the irrigation has affected the surface and groundwater interactions in the watershed,where agriculture heavily depends on irrigation.Annually 11.64 Mm3 water entered to the aquifer by surface recharge(precipitation,irrigation),transmission loss from river and recharge wells 5.8 Mm3 and ground water boundary flow(annually 20.5 Mm3).Water output in the watershed included ground water extraction and groundwater return flow(annually 46.4 Mm3)and ground water boundary flow(annually 0.68 Mm3).Overally,the groundwater storage has decreased by 9.14 Mm3 annually in Samalqan aquifer.This method can be applied to simulate the effects of surface water fluxes to groundwater recharge and river-aquifer interaction for areas with stressed aquifers where interaction between surface and groundwater cannot be easily assessed. 相似文献
59.
Zahra Yazdi Alireza Jafari Rad Mehraj Aghazadeh Peyman Afzal 《Journal of the Indian Society of Remote Sensing》2018,46(10):1581-1593
The Sonajeel prospect is located in the Arasbaran belt which is one of the significant copper mineralization belts in NW Iran. There are mostly Eocene volcano-sedimentary rocks and Post Eocene intrusive units which are the source for mineralization in the area. ASTER multispectral images were used for delineation of alteration zones as a key feature of porphyry copper mineralization. Due to the need for geometric correction and ortho-rectification of the ASTER images, a high resolution QuickBird image with pixel width of about 60 cm (in PAN) was employed as a reference image in order to boost the rectification process. Ortho-rectification has been done by using digital elevation model which is created by topographic map in scale 1:1000. Potassic alteration as one of the essential alteration types in porphyry copper deposits, distributed mostly in the north of the Sonajeel prospect that determined by Thermal infrared bands processing. Phyllic and argillic alteration zones detected by creating relative absorption band-depth grids which are comparable to field observations. Moreover, silica rich areas which are remnants of hydrothermal circulation and form at the top of porphyry copper systems were detected for recognition of epithermal deposits (with 1 km distance from Sonajeel porphyry system). Finally, Remote Sensing results were compared by field evidences especially for determination of an epithermal system. Most parts of the alteration zones were observed of the surface confirmed with the remote sensing alteration (in average about 75% matched fittingly), displayed concentrations anomalous in the NE and NW parts of the studied area. 相似文献
60.
Rahmani Javanmard Somayeh Tahmasbi Zahra Ding Xing Ahmadi Khalaji Ahmad Hetherington Callum J. 《Mineralogy and Petrology》2018,112(6):837-856
Mineralogy and Petrology - Pegmatite-hosted garnets from four localities in the Boroujerd region, Lorestan (Western Iran), have been analysed for major and selected trace element compositions. The... 相似文献