The Effect of Adjacent Magnetic Sources on the Interpretation of Magnetic Anomalies

Abstract

In interpreting magnetic profiles from the aeromagnetic map of Iraq, it is usually assumed that the observed anomalies are caused by homogeneous magnetic bodies forming the basement that is concealed beneath a thick cover of sediments. Many unknowns are faced in interpreting magnetic anomalies related to such deep sources. Among these: direction of magnetization in these sources, magnetic susceptibility and the contributions of the adjacent sources are the most important unknowns. Therefore, it is to be assumed that these anomalies are related to igneous bodies within the basement rocks and magnetized by induction only from the present earth’s magnetic field. In other word, the study is focused on one of the unknowns mentioned above, which is the effect of contribution of adjacent igneous body at different depths and sizes on the shape of main magnetic anomaly. Previous studies related to interpretation of aeromagnetic anomalies in Iraq, have assumed that these basement anomalies are not affected by adjacent igneous masses and as such not taken in consideration, (Al Mashhadani, 2000, Najar, 1999, Mohammed 1981, Mahmood, 1981, Aziz, 1981). In this paper ,the effects of such close magnetic sources will be considered . The suggested method is designed at estimating the amount of change in the -ve part of the anomaly occurring between two igneous sources, which in turn depends on how close the adjacent igneous sources to the main one.