排序方式： 共有19条查询结果，搜索用时 46 毫秒
11.
Seismic sections and the analysis of lithostratigraphic units from well-log data were used to develop a new stratigraphic correlation of the Winduck, Snake Cave and Ravendale Intervals for the Blantyre Sub-basin. The stratigraphic boundaries of the intervals were defined at marked changes in well-log characteristics, and depth estimates of the boundaries were derived from the well-log data in Mt Emu 1, Blantyre 1 and Kewell East 1. Six seismic-stratigraphic boundaries have been identified in the seismic sections to show the continuity of the latest Silurian to Holocene sediments throughout the Blantyre Sub-basin; from bottom to top they are: H-1, base of the Winduck Interval; H-2, base of the Snake Cave Interval; H-3, base of the Ravendale Interval; H-4/5 base of the undifferentiated Upper Carboniferous/Permian sediments; and H-6 base of the undifferentiated Cenozoic sediments. All stratigraphic boundaries are based on good continuous markers, with strong amplitudes throughout the whole sub-basin. A three-dimensional geological model was developed from the seismic data to map out the geometry of the key reflectors, and hence the structure and stratigraphy of the Winduck, Snake Cave and Ravendale Intervals in the areas where these intervals have been preserved. This model has better defined the Wilcannia High and two smaller highs around the Mt Emu 1 and Snake Flat 1 wells, and further defines the relationships between the stratigraphy, sub-basin geometry and development of complex structures in the Blantyre Sub-basin. 相似文献
12.
Um Bogma area is the most famous mineralized locality in Sinai, Egypt. It is characterized by the presence of manganese, iron,
and copper deposits. Apart from the mill tailings and spoil heaps, the results indicated the decrease of soil contamination
downstream. As a result of random manganese mining activity in Um Bogma area, many hazardous elements such as iron, copper,
manganese, lead, and zinc as well as many others associating heavy metals such as arsenic, selenium, and sulfur are dispersed
in the environment. This study assesses and monitors the environmental impacts of such mining activities in the west central
Sinai, using multitemporal spectral remote-sensing sensors (MSS 1972, TM 1986, and ETM+7 2000). The results have shown the
very high potential of temporal imagery in mining-related contamination either directly through mineral and rock mapping of
the mining waste and residues and related contaminated areas. 相似文献
13.
Metavolcanic rocks hosting base metal sulphide mineralization, and belonging to the Kid
Metamorphic Complex, are exposed in the Samra-Tarr area, Southern Sinai. The rocks consist of slightly
metamorphosed varicolored porphyritic lavas of rhyolite-to-andesite composition, and their equivalent
pyroclastics. Geochemically, these metavolcanics are classified as high-K calc-alkaline, metaluminous
andesites, trachyandesites, dacites, and rhyolites. The geochemical characteristics of these metavolcanics
strongly point to their derivation from continental crust in an active continental margin. The sulphide
mineralization in these metavolcanics occurs in two major ore zones, and is represented by four distinct
styles of mineralization. The mineralization occurs either as low-grade disseminations or as small
massive pockets. The associated hydrothermal alterations include carbonatization, silicification, sericitization
and argillic alterations. The base metal sulphide mineralization is epigenetic and was formed by
hydrothermal solutions associated with subduction-related volcanic activity. 相似文献
14.
This paper describes how the continuous wavelet transform is used to filter multiple waveforms in both time and frequency domains. It is well suited to process the stationary signals, and it shows the signal in both time and frequency scales. This new approach was tested first on synthetic data and then on real data. The results obtained on both cases were good. The method consists of identifying the multiples on which we apply a normal move out using the multiple velocity law. The multiples will be aligned and the primary reflections will not be aligned. This operation allows locating the multiples in the time-scale domain. We compute the continuous wavelet transform (CWT for short) in order to focus on the patterns relative to seismic events. To filter the multiples, we define a zone with frequency and time bounds. These bounds are deduced from the projection of the seismic trace. Then an automatic mask is applied to the pattern to be isolated. Filtering in time–frequency domain is done by keeping only the wavelet coefficients that are outside the mask and assigning zero to the coefficients larger than a threshold amplitude inside the defined zone. The mask shape does not matter, which is not the case in classical filtering, where both the window size and shape play a key role. The mask is defined from three parameters: time, frequency, and the wavelet coefficients. To go back to the time domain, one has to compute the wavelet transform inverse of the trace. This procedure is repeated for all traces. To reset the traces to their initial positions, we apply the dynamic correction inverse with the same velocity law as the multiples. It turns out that the attenuation of multiples by the CWT works fine, in particular, the two identified multiples were quasi eliminated (Fig. 10). 相似文献
15.
The groundwater in Wadi Queh exists in two main hydrogeological units; fractured Precambrian basement and sedimentary rocks with high contribution for groundwater recharge. To study the impacts of phosphate mining activities on the groundwater quality in the area, three groundwater samples that represent all water wells in the area were collected and analysed for major ions and some heavy metals. In addition, three bulk samples representing the phosphatic sediments collected from upstream and downstream of the drainage basin were collected and analysed to understand the source of groundwater contamination. The total concentrations of dissolved solids suggest that the groundwater in the area grades from fresh to brackish water (961–1,580 mg/l), and is characterized by sodium–calcium–sulphate–chloride and sodium–magnesium–sulphate–chloride chemical types. The results showed high concentrations of the heavy metals in well nos. 1 and 2 in downstream parts compared to well no. 3 in upstream part reflecting their influence by the mining activities. 相似文献
16.
17.
Muhammad Khalifa Nadir Ahmed Elagib Bashir Mohammed Ahmed Lars Ribbe Karl Schneider 《水文科学杂志》2020,65(Z3):153-168
ABSTRACTUnderstanding the human–water–food–climate nexus is central to achieving sustainable intensification (SI) in agriculture. This research uses a socio-hydrological approach to understand the underpinning for implementing SI in the Gezira Irrigation Scheme, Sudan, by integrating vegetation indices derived from remote sensing, ancillary, gridded soil and precipitation data, supplemented by interviews with 393 farmers. The productivity gap was estimated as the difference between the potential and actual productivities. Based upon data on farmers’ socio-economic status and field practices, a regression tree model was built to determine the factors that control the sorghum yield. The model revealed that the financial status of farmers and access to water are the most influential factors on sorghum yield. A conceptual framework that elucidates SI and its bi-directional feedback to the environment, society and the economy is proposed. Implementing SI in the scheme has implications on water and food security in Sudan and beyond its borders. 相似文献
18.
Issa?El-HussainEmail author Rachid?Omira Ahmed?Deif Zaid?Al-Habsi Ghazi?Al-Rawas Adel?Mohamad Khalifa?Al-Jabri Maria?Ana?Baptista 《Arabian Journal of Geosciences》2016,9(15):668
The Sultanate of Oman is among the Indian Ocean countries that were subjected to at least two confirmed tsunamis during the twentieth and twenty-first centuries: the 1945 tsunami due to an earthquake in the Makran subduction zone in the Sea of Oman (near-regional field tsunami) and the Indian Ocean tsunami in 2004, caused by an earthquake from the Andaman Sumatra subduction zone (far - field tsunami). In this paper, we present a probabilistic tsunami hazard assessment for the entire coast of Oman from tectonic sources generated along the Makran subduction zone. The tsunami hazard is assessed taking into account the contribution of small- and large-event magnitudes. Results of the earthquake recurrence rate studies and the tsunami numerical modeling for different magnitudes were used through a logic-tree to estimate the tsunami hazard probabilities. We derive probability hazard exceedance maps for the Omani coast considering the exposure times of 100, 250, 500, and 1000 years. The hazard maps consist of computing the likelihood that tsunami waves exceed a specific amplitude. We find that the probability that a maximum wave amplitude exceeds 1 m somewhere along the coast of Oman reaches, respectively, 0.7 and 0.85 for 100 and 250 exposure times, and it is up to 1 for 500 and 1000 years of exposure times. These probability values decrease significantly toward the southern coast of Oman where the tsunami impact, from the earthquakes generated at Makran subduction zone, is low. 相似文献
19.
A pore-scale network model based on spherical pore bodies and cylindrical pore throats was developed to describe the displacement of water by DNAPL. The pore body size and the pore throat size were given by statistical distributions with user-specified values for the minimum, mean and maximum sizes. The numerical model was applied to a laboratory experiment conducted on a sand-filled glass column. The parameters relative to pore body size and pore throat size that were used in the construction of the equivalent network were derived from the discrete grain-size distribution of the real porous medium. The calculated arrival times of the DNAPL front were compared with those measured using optic fibre sensors placed at different points on the control section of the experimental device. Furthermore, the model simulated DNAPL pressure measured at the entrance section of the system. In general, the numerical results obtained with the model were in good agreement with the actual measurements. 相似文献