Mapping basement relief of Abu Gharadig Basin, Western Desert of Egypt using 3D inversion of pseudo-gravity data

Summary

There are a number of magnetic inversion methods that have been developed to map the structure and depth of sedimentary basins, assuming that sediments are nonmagnetic and underlain by magnetic basement. Gridding/mapping the basement depth estimates from such methods has two significant problems: 1) the magnetic results are dominated by signals coming from the top edges of basement faults such that the depth information from the down thrown sides of the faults is not captured and 2) within the centres of large basins there is often little variation in the magnetic anomaly to provide depth estimates such that when gridding the depth data, grid interpolation has to rely on a sparse distribution of estimated depths.

In this study we convert the magnetic data into pseudogravity which is then inverted to produce a 3D basin model with a constant susceptibility basement. This overcomes the interpolation problem since the 3D model now uses the complete pseudo-gravity field as well as the magnetic depth estimates to constrain the depth model. The method is applied to the Abu Gharadig basin, Western Desert, Egypt and generates results which match well controls on basement depth. The advantages of this method over 3D gravity inversion are that the pseudogravity response is not affected by structure within the sediments and is not compensated isostatically as the gravity response of basins often is affected.

Key words::

• magnetic
• inversion
• pseudo-gravity
• depth
• basement