Full Tensor Magnetic Gradiometry Processing and Interpretation Developments
Des FitzGerald, Dominik Argast, Rod Paterson and Horst Holstein
Event name: 11th SAGA Biennial Technical Meeting and Exhibition
Session: Numerical Methods
Publication date: 16 September 2009
Info: Extended abstract, PDF ( 494.38Kb )
In recent years, Anglo/De Beers have championed the development of a Full Tensor Magnetic gradient (FTGM) signal instrument from IPHT. Multiple surveys of this quantity have been made in Southern Africa. With the advent of this new potential field full tensor gradient instrumentation, new methods have been developed to de-noise and process these curvature gradients. Traditional Fourier domain and minimum least squares residual of the linear differential tensor relationships have been adapted. This leads to levelling, gridding and grid filtering innovations. The result is a full tensor grid representation of the curvature gradients that is coherent and compliant with the physics at all points in the grid. All of the observed data is thus honoured in the Tensor grid. Isolating the signal and then refining it to be sure there are no distortions have dominated efforts to date. Superior anomaly interpretation regarding the full magnetic history and inferences can then be made. A survey from the Groblersdal Platinum mine is shown in the context of the structural geology interpretation. In particular, the dolerite dykes and faults are seen. The Hornfels footwall contact is very strong. The phase map traces the Platreef contact. The Upper Zone magnetites are more pervasive and fine layered structure is revealed there. None of the granites can be seen. A 3D geology model is in preparation. The observed FTG signal will be compared to the predicted thin-body responses from the model. There is more directly inferable structural geology in this tensor signal than can be found in a conventional TMI signal.