Why bother about gradients? – SQUID based full tensor magnetic gradiometer for mineral exploration

Superconducting Quantum Interference Devices (SQUIDs) are still known to be the most sensitive detectors of magnetic flux. The recent sensor techno-logies reached a mature state and thus enabled to build reliable systems for geophysical purposes which open a wide range of different applications in Geosciences. In this work is a new SQUID based instrument for measurements of the full magnetic gradient tensor of the Earth’s magnetic field in survey scenarios was implemented using planar-type first-order gradiometers. The new instrument was deployed in different geologic settings. As an example in 2012-2014 the system was flown in a sedimentary basin in Thuringia, a local province in Germany. In order to assess the instruments performance innovative processing, inversion, and inter¬pretation techniques were developed for data acquired with this instrument. The recent instrument state and data processing techniques are presented. The use of the new instrument provides advantages compared to commercially available high-resolution aeromagnetic survey instruments. Firstly, high resolution vector information is delivered which allow detecting weaker magnetic anomalies. Secondly, more detailed information even on remanence of the geologic structures is available. One example of preliminary inversion results is discussed which indicates remanent magnetization of the rocks which cause a magnetic anomaly.