Data sets to be used for interpretation in mapping projects
Cranfield Geoservices (CGSI) uses all available data and knowledge to create or update geological maps and integrate an updated understanding of the regional structure and geological evolution into local prospects. A comprehensive understanding of how airborne geophysical and remotely sensed imagery enhance interpretation of the local geology is vital in designing your exploration program.
Airborne Surveys for geological mapping use both radiometric and magnetic imagery. Radiometric surveys measure gamma rays which are continuously being emitted from the Earth by natural decomposition of some common radiogenic minerals. The use of radiometric imagery to distinguish differences in rock chemistry between and within geological units has been applied most extensively for granitic rocks, but it is gaining in acceptance to use to distinguish chemical difference including:
- Exploration for a range of uranium deposits.
- Special applications such as exploration for diamonds by assisting in location of kimberlite.
- Porphyry copper deposits particularly in zones of potassic alteration
- Exploration for gold using the Au-U association in specific localities.
- Exploration for radioactive halos over hydrocarbon deposits.
Subsurface geophysical techniques for creating a solid geology map and underlying resources (ie on of an interpreted geology below the surface include:-
- Magnetic surveys – which measure variations in the Earth’s magnetic field due to the presence of magnetic minerals. Subtle changes to these minerals are used to interpret rock types and assist in identifying resources. These surveys can be aerial, on the surface or in down-hole logging tools. Magnetic surveys are commonly used in mineral exploration.
- Gravity surveys – include both ground and airborne surveys. The instrumentation identifies variations in rock density in the Earth’s crust. These surveys are commonly used in conjunction with magnetic surveys to locate regions of higher density that may correlated with economic mineralization.
- Induced Polarisation (IP) surveys induce an electric field in the ground and measure the chargeability and resistivity of the subsurface to locate changes in the electric currents due to variations caused by rocks and minerals.
- Electromagnetic (EM) surveys create an induced electromagnetic field and measure the three dimensional variations in conductivity (capacity to conduct electricity) within the near-surface soil and rock. Uses include the location metallic minerals,and to understand groundwater and salinity. In the case of groundwater salinity there is a capacity to model the salinity at different depths.
For any additional information on your projects and details of experience contact me.