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Using air-borne gamma ray spectrometry and remote sensing data for detecting alteration zones around Wadi Saqia area, Central Eastern Desert, Egypt
Journal of African Earth Sciences ( IF 2.2 ) Pub Date : 2021-03-12 , DOI: 10.1016/j.jafrearsci.2021.104181
S.M. Ghoneim , S.H. Abd El Nabi , M.A. Yehia , S.M. Salem

This study presents the air-borne geophysical Gamma Ray Spectrometry data have been used for detecting the alteration zones related to hydrothermal activity. Areas enriched in potassium may indicate the existence of potassic alteration zone that is often associated with hydrothermal alteration accompanied by economic mineral deposits. The radioelements (K (%), eTh (ppm), and eU (ppm)) concentration distribution and the ratios of (K/eTh and K/eU) over the study area were presented. A Potassium Point anomaly map was obtained from the statistical treatment of the K (%), K/eU, and K/eTh spectrometric data. Anomalously High (X+3σ or more) areas were delineated and considered the most preferred areas for potassic alteration. If the maximum values exceed the (X+3σ) threshold, then (X+2σ) or (X+σ) is applied instead. Sixteen areas were delineated and suggested for the presence of potassic alteration. The F-Parameter of Efimov (K*(eU/eTh)) was also implemented as proved approach for delineating the most preferred areas for hydrothermal alteration. The result of the Potassium point anomaly mapping was compared to that of the F-Parameter technique that was used as reference for validating the results. The sixteen anomalous areas revealed from the Potassium point anomaly technique showed perfect correlation with the areas of highly anomalous F-parameter.

Remote sensing study supported by field data and laboratory spectral analyses was also implemented in this study as another useful powerful cost-effective approach for alteration mapping. A field study was conducted; samples from the different observed alterations were collected. The spectral signatures of these samples were measured using the “ASD TerraSpec Halo mineral identifier” hand-held spectroradiometer. Spectral analyses were performed to obtain the spectral characteristics of the alteration zones of the study are. The end-members were identified through comparing the measured spectra against the United States Geological Survey (USGS) spectral library in ENVI v.5.1. software. The identified end-members include; Kaolinite, Sericite, Montmorillonite, Chlorite, Epidote and iron oxides. Subpixel Mixture Tuned Matched Filtering (MTMF) mapping technique was finally used for mapping the distribution of these end-members on ASTER nine Visible Near Infra-Red (VNIR) and Short Wave Infra-Red (SWIR) bands. The remote sensing data were validated as Semna gold mine and the identified alterations during the field study were successfully mapped by the remote sensing technique. Finally; Most of the delineated areas using the proposed Potassium point anomaly technique were also evidenced by the approached remote sensing technique. Moreover remote sensing suggested more alteration areas than did the gamma ray spectrometry data.



中文翻译:

利用机载伽马射线能谱和遥感数据检测埃及中部东部沙漠瓦迪·萨卡地区附近的蚀变带

这项研究表明,航空地球物理伽马射线光谱数据已用于检测与热液活动有关的蚀变带。钾含量高的区域可能表明存在钾盐蚀变带,该蚀变带通常与热液蚀变有关伴随着经济的矿藏。介绍了研究区域内的放射性元素(K(%),eTh(ppm)和eU(ppm))浓度分布以及(K / eTh和K / eU)的比率。从K(%),K / eU和K / eTh光谱数据的统计处理中获得了钾点异常图。划定了异常高(X +3σ或更大)的区域,并被认为是钾盐蚀变的最优选区域。如果最大值超过(X +3σ)阈值,则改为应用(X +2σ)或(X +σ)。划定了十六个区域,并建议存在钾质改变。Efimov的F参数(K *(eU / eTh))也已被证明是划定水热蚀变最优选区域的方法。将钾点异常映射的结果与用作验证结果的参考的F参数技术进行了比较。钾点异常技术揭示的16个异常区域与高度异常F参数的区域显示出完美的相关性。

在这项研究中还实施了由野外数据和实验室光谱分析支持的遥感研究,这是另一种有用的,功能强大,成本效益高的蚀变图方法。进行了实地研究;收集了来自不同观察到的变化的样本。这些样品的光谱特征是使用“ ASD TerraSpec Halo矿物识别器”手持式光谱仪测量的。进行光谱分析以获得研究变化区的光谱特征。通过将测得的光谱与ENVI v.5.1中的美国地质调查局(USGS)光谱库进行比较来确定最终成员。软件。确定的最终成员包括;高岭石,绢云母,蒙脱土,亚氯酸盐,附子和氧化铁。最终使用亚像素混合调谐匹配滤波(MTMF)映射技术在ASTER九个可见近红外(VNIR)和短波红外(SWIR)波段上映射这些末端成员的分布。遥感数据被确认为塞姆纳金矿,并通过遥感技术成功地绘制了实地研究中发现的蚀变。最后; 使用拟议的钾点异常技术的大多数划定区域也通过接近遥感技术得到了证明。此外,与γ射线光谱数据相比,遥感显示了更多的蚀变区域。

更新日期:2021-03-19
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