AIRBORNE SPECTROMETRY AND MAGNETOMETRY OF GEBEL HADA YIB AREA, SOUTH EASTERN DESERT EGYPT, IN SUPPORT OF GEOLOGICAL MAPPING AND MINERAL EXPLORATION

Abstract

The aim and purpose of this study is to help delineate, modify and correct the regional lithological and structure as well as to define the anomalous radiometric zones of G. Hadayib area, South Eastern Desert of Egypt.

The aerospectrometric survey data have been statistically analyzed and treated qualitatively and quantitatively by applying various geophysical techniques. Regional remapping of the different rock units of the study area was carried out through the application of the factor analysis technique. Twenty-one interpreted radiometric-lithologic IRL units, have been distinguished and correlated with the compiled geological map of the study area. Corresponding statistical characteristics have been computed and established for each IRL unit in the area. According to this technique, the boundaries of some geological units have been corrected. Meanwhile, the others have been subdivided and/or modified. These units were treated statistically to determine the significant levels of radioactive anomalies. The defining of significant radioactive anomalies has been performed by two ways. The first one is by calculating the significant factor (threshold) of the aerospectrometric data for each IRL unit. The second way is by examining the stacked profiles for regions of high eU, eU/eTh and eU/ K. The degree ofremobilization of uranium in each IRL unit is also shown as reflected from the trend variations of uranium and thorium with their ratio. The utilization of the two-dimensional power spectrum technique to determine the depths of the causative magnetic bodies within the basement rocks concluded that the causative magnetic bodies in the area are aggregated at two disturbing interfaces having average depths 1.01 and 2.2 km.

Filtering combined with the analytical downward continuation at the two assigned interfaces could simply assist in discriminating between the shallow (near-surface or residual) and deep (deep- seated or regional) causative anomalies bodies. Four maps were drawn, two at each interface: one for the regional component of the magnetic field and the other for the residual one. Also, the normalized total and horizontal magnetic vector (gradient) of the field intensity and the variations of the total and horizontal phase angle were calculated at the two stated interfaces to assist in construction of the two basement tectonic maps at the two interfaces. These were aided by the available geological information of the study area. Spectral frequency analysis using Pilon Fourier Transform "FFT' for

depth determination technique was applied on 64 selected magnetic anomalies on the RTP aeromagnetic map. The results obtained from this technique were tabulated and contoured to show the degree of variation in the basement relief. Statistical trend analysis using autocovariance and rose diagram techniques were conducted for the different aeromagnetic and aerospectrometric maps as well as the compiled geological map in order to obtain accounted with the predominant tectonic trends affected the studied area.