Dyke detection as the main target of groundwater exploration using Magnetometry and Electromagnetic data.

Dolerite structures, such as dykes and sills are the main target for groundwater exploration in the Karoo Supergroup area which is the main stratigraphic unit in South Africa. Morgenzon Farm is one of the sites in the Karoo Supergroup, including a dolerite dyke, which is of interest here. The magnetization/susceptibility and resistivity of the dolerite dyke are significantly larger than those of the encompassing sedimentary materials. Therefore, the low induction number electromagnetic (EM-LIN) and magnetometry approaches may be useful for its detection. The EM-LIN is composed of three techniques: EM38, EM31, and EM34, with the latter being manipulated. Since both EM34 and magnetometry inverse problems are linear, a regularized weighted minimum length solution algorithm is utilized for their inverse modelling, but with one main discrepancy: the model weighting function for the magnetometry method is attained from the multiplication of depth weighting and compactness constraints, while the model weighting function is only equal to depth weighting for the EM34 approach. Recovered susceptibility and conductivity sections derived respectively from magnetic and EM34 data sets show high consistency. Inverted models represent a dolerite dyke in the middle of the profile with a depth range of 4 to 15m. [ABSTRACT FROM AUTHOR]