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Gomaa, M. M.
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Gomaa, M. M.
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- PublicationOpen AccessRelation between electric properties and water saturation for hematitic sandstone with frequency(2008-10)
; ;Gomaa, M. M.; National Research Centre, Geophysical Sciences Dep., El-Tahrir St. Dokki, 12311, EgyptThis paper focuses on the effect of water saturation on A. C. electrical conductivity and dielectric constant of fully and partially saturated hematitic sandstone sample (Aswan area, Egypt). The saturation of the sample was changed from partial to full saturation. Complex resistivity measurements at room temperature (~16°C), were performed in the frequency range from 0.1 Hz to 100 KHz. Experimental electrical spectra indicate, generally, that the electrical conductivity and dielectric constant vary strongly with water saturations and frequency. The low frequency electrical conductivity and dielectric constant are mainly controlled by surface conduction and polarization of the electrical double layer. The behaviour of the electrical conductivity and dielectric constant, with increasing water content, were argued to the orientational polarization of bound water for very low saturations, displacement of the excess surface charges for relatively low saturations, and free exchange of excess ions in double layer with the bulk electrolyte and generation of transient diffusion potentials which lag behind the applied field for high saturations.476 1022 - PublicationRestrictedKamil Crater (Egypt): Ground truth for small-scale meteorite impacts on Earth(2011-02)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Folco, L.; Museo Nazionale dell’Antartide Università di Siena, Via Laterina 8, 53100 Siena, Italy ;Di Martino, M.; Istituto Nazionale di Astrofi sica, Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy ;El Barkooky, A.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt ;D’Orazio, M.; Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy ;Lethy, A.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Hafez, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;Cordier, C.; Museo Nazionale dell’Antartide Università di Siena, Via Laterina 8, 53100 Siena, Italy ;van Ginneken, M.; Museo Nazionale dell’Antartide Università di Siena, Via Laterina 8, 53100 Siena, Italy ;Zeoli, A.; Museo Nazionale dell’Antartide Università di Siena, Via Laterina 8, 53100 Siena, Italy ;Radwan, A. M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;El Khrepy, S.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;El Gabry, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;Gomaa, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;Barakat, A. A.; Egyptian Mineral Resources Authority, 3 Salah Salem Road, Abassiya, Cairo, Egypt ;Serra, R.; Egyptian Mineral Resources Authority, 3 Salah Salem Road, Abassiya, Cairo, Egypt ;El Sharkawi, M.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Small impact craters (<300 m in diameter) are rare on Earth and mostly deeply eroded, so that knowledge of their formation mechanism and the hazard small impactors constitute to human populations is largely based on physical models. We report on the geophysical investigation of the Kamil Crater we recently discovered in southern Egypt. The Kamil Crater is a <5 k.y. old impact crater 45 m in diameter, with a pristine ejecta ray structure. Such well-preserved structures have been previously observed only on extraterrestrial rocky or icy planetary bodies. This crater feature, and the association with an iron meteorite impactor and shock metamorphism, provides a unique impression of aspects of small-scale hypervelocity impacts on the Earth’s crust. Contrary to current models, ground data indicate that iron meteorites with masses of tens of tons may be able to penetrate the atmosphere without substantial fragmentation.313 33 - PublicationOpen AccessThe Kamil Crater in Egypt(2010-08-13)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Folco, L.; Museo Nazionale dell'Antartide Università di Siena, Via Laterina 8, 53100, Siena, Italy. ;Di Martino, M.; Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy. ;El Barkooky, A.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt. ;D'Orazio, M.; Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy. ;Lethy, A.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt. ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Hafez, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt. ;Cordier, C.; Museo Nazionale dell'Antartide Università di Siena, Via Laterina 8, 53100, Siena, Italy. ;van Ginneken, M.; Museo Nazionale dell'Antartide Università di Siena, Via Laterina 8, 53100, Siena, Italy. ;Zeoli, A.; Museo Nazionale dell'Antartide Università di Siena, Via Laterina 8, 53100, Siena, Italy. ;Radwan, A. M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt. ;El Khrepy, S.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt. ;El Gabry, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt. ;Gomaa, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt. ;Barakat, A. A.; Egyptian Mineral Resources Authority, 3 Salah Salem Road, Abassiya, Cairo, Egypt. ;Serra, R.; Dipartimento di Fisica, Università di Bologna, Via Irnerio 46, 40126 Bologna, Italy. ;El Sharkawi, M.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt.; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We report on the discovery in southern Egypt of an impact crater 45 m in diameter with a pristine rayed structure. Such pristine structures have been previously observed only on atmosphereless rocky or icy planetary bodies in the Solar System. This feature and the association with an iron meteorite impactor and shock metamorphism provides a unique picture of small-scale hypervelocity impacts on the Earth's crust. Contrary to current geophysical models, ground data indicate that iron meteorites with masses of the order of tens of tons can penetrate the atmosphere without significant fragmentation.230 519 - PublicationRestrictedGeological and geophysical investigation of Kamil crater, Egypt(2012-12-14)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Zeoli, A.; Museo Nazionale dell’Antartide Universita` di Siena, Via Laterina 8, 53100 Siena, Italy ;El Khrepy, S.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;Lethy, A.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;Hafez, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;El Gabry, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt ;El Barkooky, A.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt ;Barakat, A.; Egyptian Mineral Resources Authority, 3 Salah Salem Road, Abassiya, Cairo, Egypt ;Gomaa, M.; Museo Nazionale dell’Antartide Universita` di Siena, Via Laterina 8, 53100 Siena, Italy ;Radwan, A. M.; Museo Nazionale dell’Antartide Universita` di Siena, Via Laterina 8, 53100 Siena, Italy ;El Sharkawi, M.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt ;D’Orazio, M.; Dipartimento di Scienze della Terra, Universita` di Pisa, Via S. Maria 53, 56126 Pisa, Italy ;Folco, L.; Dipartimento di Scienze della Terra, Universita` di Pisa, Via S. Maria 53, 56126 Pisa, Italy; ; ; ; ; ; ; ; ; ; ; ; ; We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small-scale hypervelocity impact craters. It is an exceptionally well-preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth-to-diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45 . Newly identified asymmetries, including the off-center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well-preserved craters. Geomagnetic data reveal no buried individual impactor masses >100 kg and suggest that the total mass of the buried shrapnel >100 g is approximately 1050–1700 kg. Based on this mass value plus that of shrapnel >10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t.479 69