Quantitative interpretation of magnetic anomalies from bodies approximated by thick bed models in complex environments

Abstract

Magnetic prospecting is a rapid and inexpensive geophysical tool and one of the most widely used methods for geophysical prospection throughout the world. However, the noise factors—such as inclined magnetization, complex geological structure of investigated areas, and uneven terrain relief—strongly obscure the interpretation of observed magnetic anomalies. The developed methodology of magnetic anomalies’ interpretation from models of thin beds and horizontal circular cylinders (spheres) in complex environments (oblique magnetization, rugged relief and unknown levels of the normal magnetic field) using improved versions of characteristic points and tangents was presented in detail in the author’s previous publications. However, many geological targets have a geometrical form of thick beds and thin horizontal plates and intermediate forms that crop up between these two models. In this paper, a methodology for interpreting magnetic anomalies produced by thick bed models in complex environments is explicitly described. It shows that quantitative analysis of magnetic anomalies due to intermediate targets could be successfully carried out using the methodology developed for the thick bed model. In the case of a thin horizontal plate with a large horizontal size, two distinct anomalies (from the left and right ends) may be interpreted as anomalies from thin beds. The interpretation methodology was successfully tested, both on typical models and on real geological targets. It was concluded that these methods could be effectively applied for quantitative analysis of magnetic surveys for geological–geophysical mapping, archeological target delineation, ore body searching, revealing oil and gas traps, and solving other geological and environmental problems.