Determining the basement parameters of south Sitra area at north Western Desert of Egypt using the contribution of gravity and magnetic modeling technique

The main objective of this study is to determine the basement parameters; depth, dip, width, extension, location, source configuration and susceptibility for the magnetic data, or density for gravity data of south Sitra area using gravity and magnetic modeling technique. The study was initiated by reducing the total intensity aeromagnetic data to the northern magnetic pole map. This followed by description of both the Bouguer gravity and RTP magnetic maps. Depth determination to the basement surface was applied on 31 gravity and 45 magnetic profiles using four spectral analysis methods. In addition, tentative depth to the basement contour map was constructed using the depth estimation results. Moreover, two different modeling techniques were applied on the data; the first one is the single anomaly modeling was applied on 31 gravity and 45 magnetic single, isolated and homogenous anomalies to reflect the near surface features with their parameters. Meanwhile, the second one is the 2.5-D gravity and magnetic modeling, was generated along eight cross-sections to support and refine the interpreted structures. Moreover, the areal distribution of the magnetic susceptibility was estimated by doing two tentative magnetic susceptibility maps at two main levels; on the surface and at the 3 km. The results of this study show that, the depth values to the basement surface (thickness of the sedimentary succession) range between 2.6 km. and 5.80 km. The models illustrate that the area is greatly affected by a number of normal and step-like faults resulting a great number of tilted faulted blocks and forming number of horsts and grabens. They indicate that the dip regime in the study area is in the northern direction. The basement rocks vary greatly in their composition as reflected by wide range of magnetic susceptibility of the different blocks. It ranges between 0.0001 and 0.0045 c.g.s unit, reflecting that, this area is composed of anticlinal uplifted blocks of shallow depth and high susceptibilities alternating with downfaulted basinal or grabenal blocks of greater depth and lower susceptibilities. Also, density values of the modeled profiles vary greatly from site to site ranging from 2.5 to 3.37 g/cc. Finally, this study shows excellent agreement between the results of modeling and the magnetic characters, shape, elongation, frequency and magnitude of the magnetic anomalies along these eight profiles.