Exploration Technique: Field Sampling
|Exploration Technique Information|
|Exploration Group:||Field Techniques|
|Exploration Sub Group:||Field Sampling|
|Parent Exploration Technique:||Field Techniques|
|Information Provided by Technique|
|Lithology:||Rock samples are used to define lithology. Field and lab analyses can be used to measure the chemical and isotopic constituents of rock samples.|
|Stratigraphic/Structural:||Can reveal relatively high permeability zones. Provides information about the time and environment which formed a particular geologic unit. Microscopic rock textures can be used to estimate the history of stress and strain, and/or faulting.|
|Hydrological:||Water composition and source of fluids. Isotope geochemistry can reveal fluid circulation of a geothermal system.|
|Thermal:||Water temperature. Used to locate active hydrothermal systems. Thermal conductivity of a rock sample can provide information to calculate heat flow. Hydrothermal alteration of a rock sample can indicate certain temperature or fluid compositions.|
Water and gas sampling are routinely used in geothermal exploration and monitoring to characterize the chemical composition of the fluid, measure the temperature, or conduct isotope studies to derive the provenance of thermal fluids. Fluid sampling is a critical aspect of characterizing a geothermal system because the water chemistry, temperature and source can reveal the quality of the resource. Water chemistry is largely controlled by temperature, water-rock interactions, volume of water vs rock, residence time, and contributions from other fluids (mixing), such as cold groundwater, seawater, magmatic fluids, etc. Waters that discharge at the surface are commonly over saturated with silica or carbonate at surface conditions and precipitate sinter or travertine, respectively. Some geothermal fluids that reach the surface form acid-sulfate springs, generated from rising steam and volatile compounds that condense and mix with an overlying freshwater aquifer, whereupon the H2S in the steam oxidizes to form sulfuric acid.
Soil sampling is typically performed in a methodical and structured way, so that the results of the geochemical analysis can be plotted spatially on a map. An active hydrothermal system releases fluids with chemical signatures that are anomalous in typical surface environments. The most volatile gases are able to escape the heat source and permeate through overlying formations and structures, casting an imprint either on the soil or into the atmosphere that is used to locate a potential geothermal resource. Analysis of soil samples is particularly useful for locating blind or covered structures in geothermal areas, which act as conduits for the ascending fluids. The successful identification of these soils can reveal relatively high permeability zones associated with otherwise unknown geothermal resources.
- Data Collection and Mapping
- Field Sampling
No exploration activities found.