| Title | DIRECT RELATIONSHIPS BETWEEN GEOLOGY AND AIRBORNE MAGNETIC DATA OVER THE TAUPO VOLCANIC ZONE (TVZ), NEW ZEALAND |
|---|---|
| Authors | S. Soengkono |
| Year | 2018 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Airborne magnetic survey, rock magnetisation, rhyolite dome, ignimbrite, geothermal field |
| Abstract | The surface geology of the Taupo Volcanic Zone (TVZ) has been known very well as the results of surface geological mapping since early 1940s by geologists from the NZ Geological Survey, GNS Science and the New Zealand universities. Airborne magnetic data are available over the TVZ at three sets of different flight elevations: (1) detailed measurements at 60m above ground surface (AGS), (2) less detailed measurements at 760 m reduced level (RL) (draped at about 100m where ground elevations are higher than 650m RL) and (3) regional measurements at 1,500 m RL. A simple comparison between these three sets of airborne magnetic data shows that these data are highly consistent with each other. Detailed interpretations and 3-D quantitative modelling of the data measured at 60 m above ground and at 760 mRL had been carried out over almost all geothermal fields in the TVZ. These interpretations were capable to delineate the lateral extents of the high temperature geothermal reservoirs in the TVZ and in providing depth estimates to where the volcanic rocks have been affected by hydrothermal alterations process. There is more information than can be extracted from these airborne magnetic data. These data also directly correlate with the surface geology of the area covered by the surveys. Some geological information are directly shown by the airborne magnetic data. Maps of the airborne magnetic anomalies can be used to draw lithological boundaries beneath the survey area. This paper demonstrates how to extract such geological information without complex interpretations and quantitative modelling of the magnetic anomalies. |