Geochemical Soil Surveys: An Exploration Technique for Low-Enthalpy Geothermal Resources
- Key words
- Exploration; New Zealand; Naike; Soil Surveys; Faults; Thermal Springs; Geology; Soil Ammonia
- Location
- Naike Hot Springs, New Zealand
- Conference
- Geothermal Resources Council Transactions
- Year
- 1990
- Session
- Exploration; Geochemical surveys; Soil gas surveys; Ammonia;
- Language
- English
Abstract
A geochemical soil survey was conducted over a sediment hosted low enthalpy resource at Naike, New Zealand. Samples were taken on a 250m x 250m grid, covering about 2.5 km2, from both the A and B horizons. Soil ammonia was selected as the pathfinder species since this attains high levels in geothermal fluids from sedimentary hosted reservoirs. The A horizon showed a stronger anomaly contrast than the B horizon. In the A horizon, the mean background concentration was 2mg NH3/kg, with anomalous values up to 25 mg NH3/kg and a threshold of 4mg NH3/kg. The results define a pattern of anomalies which parallel known faults, thereby implying a fracture dominated hydrology a conclusion supported by previous geophysical surveys. This study demonstrates that soil surveys can be useful in the exploration for low enthalpy resources, and shows that ammonia is an effective pathfinder to this type of geothermal field.
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