MAPPING CONCEALED TERTIARY VOLCANICS, ABU-ZAABAL AREA, EGYPT USING GROUND MAGNETIC SURVEY | ||||
| Journal of Egyptian Geophysical Society | ||||
| Volume 7, Issue 1, 2009, Page 51-59 PDF (604.6 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jegs.2009.380877 | ||||
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| Author | ||||
| A.A. NIGM | ||||
| Nuclear Materials Authority, P. O. Box 530 El Maadi, Cairo , Egypt | ||||
| Abstract | ||||
| Tertiary volcanics were erupted accompanying tectonic activity, mainly tensional faulting, in Northern Egypt and Sinai Peninsula. They are mostly of basaltic composition, forming sheets and dykes. Previous geological studies, confirmed by drilling, reported multilayered basaltic sheets imbedded in the sedimentary section, at Abu-Zaabal area, 35 km to the northeast of Cairo. Because of its high magnetic susceptibility, these basaltic rocks can be efficiently mapped using magnetic survey. They are characterized, mostly, by dipolar magnetic anomalies of large amplitude and short wavelength. However, magnetic expression of basaltic rocks is commonly dominated by remanent magnetization that stumbling block quantitative interpretation. This study presents the utilization of ground magnetic survey data to determine the location, shape, depth and thicknesses of the sheeted basalt in Abu-Zaabal area and its vicinity, Egypt. The magnetic data shows linear magnetic anomalies of strong amplitudes trending in the NW direction, parallel to the main trend of the Red Sea and Gulf of Suez rift. Besides, there are several magnetic anomalies with different intensities reflecting different depths, thicknesses and sizes of the causative basaltic intrusions. The ground magnetic data have been subjected to three advanced interpretation techniques, which provide automatic delineation and depth estimation of the basaltic sheets. These techniques include horizontal gradient (HG), Euler deconvolution and local wave-number (LWN). The interpreted results supported by a drilling program show that the basaltic flows at the study area are represented mainly by sheets at three levels. The shallower sheet is at 26 m to 30 m depth crossing the study area from SE to NW and bifurcated to two sheets in the NW direction that dip to the NE. The depth of sheet to the intermediate level ranges between 54 m and 58 m. Meanwhile, the deepest sheet is, generally, sub-horizontal with varying thicknesses and depth ranges from 100 m to 150 m. These sheets are dissected by N-S and NE-trending fault systems. The depth to the basaltic intrusions was found to increases due south and east of the study area. | ||||
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