In late 2023 Metatek completed the acquisition, processing and interpretation of an airborne geophysical survey over an area of 1047 km², for the purposes of further advancing geothermal exploration. The area of interest contains a number of hot-spring resorts and geothermal stations and further development is planned to maximise the geothermal potential of the area. Objectives of the survey were to confirm the location, extent and depth of sedimentary areas surrounding the volcanic magma chambers, model those volcanic centres and identify the faults and lineaments through which the heat source may propagate to surface.

The geophysical tools used were enhanced Full Tensor Gravity Gradiometry (eFTG), conventional gravity (AGMA), magnetics and LiDAR. The survey was acquired over an area of both rural and urban centres (spa and ski resorts), with topography ranging from 91 m to 2037 m. Due to the need to achieve low flight heights, to maximise data resolution, a careful multi-azimuth aircraft flight drape was considered.

Acquisition commenced on 18^th October and 4,930 line km’s of data were acquired within the block, with a total of 7,759 line km’s acquired and processed when run-ins & run-outs and turns were included, giving an additional 57% spatial coverage. Acquisition was over 14 short production flights, within a tight technical specification, at a line spacing of 250 m and tie line spacing of 3 km. Fast track processing (within 24 hours) allowed the data to be analysed prior to further infill acquisition being completed.

Once survey acquisition was completed the data were processed, using an advanced “Equivalent Source” method to combine the result of the gradiometry (Gzz) and conventional gravity (GzHD), to provide a full band-width dataset. Processing was completed within 4 weeks, followed by a 6-week interpretation of all the datasets, to produce both qualitative and quantitative interpretation deliverables, including 2D and 3D modelling.

The eFTG data provided a wealth of information on the density distribution of the subsurface, the location and depth propagation of the major and minor faults and lineaments. In particular, the location of low-density sedimentary depocentres, were of interest surrounding the volcanic centres. The magnetic data provided detailed information on the distribution and character of the volcanic features, and confirmed faulting, lineaments, due to the mineralisation of the fluid pathways.

The fully processed point-cloud LiDAR datasets provided a bare—earth model of the topographic surface, in a highly forested area, allowing surface geology features to be identified; calibrated against legacy geology maps and used alongside the eFTG and magnetic data to propagate from the surface to deep.

The location of the survey was also selected as previously a high-resolution airborne survey had been acquired and the 2023 survey allowed a like-for-like comparison on the methods.