A Novel Semi-airborne EM System for Mineral Exploration - First Results from Combined Fluxgate and Induction Coil Data

Nittinger C, Cherevatova M, Becken M, Martin T, Petersen H, Steuer A, Meyer U, Siemon B, Matzander U, Friedrichs B, Mörbe W, Yogeshwar P, Tezkan B, Rochlitz R, Günther T

Zusammenfassung

A novel semi-airborne frequency domain system is developed within the DESMEX project. The system is designed to achieve a penetration depth of about 1km with an areal coverage of about 6×6km2 per source installation on the ground. Here, we report on first results achieved with the new system. Horizontal electric dipole transmitters were used to inject time-varying electrical currents into the ground, and both a three-axis induction coil set up (Metronix MFS-11e) and a fluxgate (Bartington MAG-03) were installed on a helicopter-towed platform. We measure the induced magnetic field in the air in a frequency range from 1Hz to 10kHz. Additionally recorded attitude data can be used for correction of motion noise and for in-flight calibration to determine orthogonality and scaling errors in the fluxgate data as well as orientation errors of all sensors within the bird. In a first flight test the corrected fluxgate data shows a good signal-to-noise-ratio in the range 10ߝ400Hz with a noise level generally below 50pT/√Hz. The coils yield superior noise levels of less than 1pT/√Hz at frequencies higher than 400Hz. Frequency-domain response functions between the magnetic field and the source current are found to be consistent with subsurface conductivity structures.

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