Geophysical Exploration of a Complex Metavolcanic Environment

The Triassic stratovolcanic complex of the East Bükk Mts. in North Hungary was the target of our geophysical exploration because of its previously known REE and critical element occurrence. There is no direct geophysical survey to locate these elements, for this reason complex geophysical survey including magnetic, very low frequency (VLF) electromagnetic, spectral radiometry, multielectrode resistivity and multielectrode induced polarization measurements were made along profiles to gain more knowledge about the possible host rocks of REE and critical elements being relatively close (5–30m) to the surface. In the course of interpretation the core description and well logs of the boreholes drilled earlier were also taken into account. It was experienced that the ore zones were overlying mainly high resistivity and low chargeability metarhyolites. The combination of the magnetic and VLF measurements were used to locate a covered boundary separating limestone and metarhyolite. Among the applied geophysical methods the simultaneous interpretation of the multielectrode resistiviy and induced polarization measurements provided the best geological image.