Remote Sensing for Mineral Exploration
In the field of remote sensing image interpretation, ACA Howe provides a complete service for mineral exploration from data acquisition through processing and interpretation to digital map generation. With a specialist capability in lithostructural interpretation combined with alteration and mineral mapping we are able to identify targets for field investigation. ACA Howe has completed a large portfolio of projects covering a wide range of commodities in an extensive variety of geological and climatic environments. This service comprises the following steps outlined below.
Data Acquisition and Processing
At the outset we are happy to advise on the data best suited to the region under consideration, and then order and acquire the data on our client’s behalf; however we are also willing to use data provided by the client. We undertake processing to ensure that the data is geocoded to the specified projection and datum and enhanced for geological interpretation. We are competent in the application and use of most types of digital image data obtained from satellite and airborne platforms, which includes Landsat, ASTER, High Resolution (HR) optical imagery & satellite and airborne radars. Interpretation of aerial photographs can also make an important contribution.
Spectral mapping uses data from satellite systems such as Landsat or ASTER to differentiate lithologies and alteration mineral suites. This is combined with structural analysis and is used to map hydrothermal systems and other indications of mineral deposits. This involves processing the data to generate ratio images to map any alteration minerals that may represent the surface expression of mineralized zones. These are highlighted on the final map, and in combination with the lithostructural interpretation provide a basis for target selection.
Target Selection and GIS Interpretation
The benefit of compiling the remote sensing interpretation directly into a GIS format means that the results can be integrated into the client’s database. This ensures that the results of the image interpretation can be combined and compared with other sources of data (e.g. geophysics, geochemistry etc.) enabling an integrated assessment of the results to refine and prioritise the targets and plan a field programme.
Lithostructural Geological Mapping
The interpretation methodology involves a process of identifying small-scale features to provide the evidence for large structures. The surface traces of features such as bedding/banding/foliation fabrics, bedrock, surficial cover, contacts, faults/fractures/lineaments, and possible dykes/veins are annotated directly on-screen to the appropriate GIS layer. The fully attributed layers of the lithostructural interpretation map normally include the following:
- Geological boundaries
- Faults fractures/lineaments dykes & veins
- Alteration anomalies possibly related to mineralisation
- Potential targets for exploration
During annotation, reference would be made to the available geological mapping to help guide interpretation and identify lithology and stratigraphy. In some cases it is also important to map geomphological features which may influence the dispersion of trace elements or host placer deposits, and these will be included where appropriate.
Over the past few years projects have been undertaken to aid the exploration for the following commodities:
- Base metals (particularly copper, lead, zinc, nickel, tin & tungsten)
These have been undertaken in the countries listed below, which include climatic zones from tropical rain forest, through temperate and semi arid savanna grasslands to desert regions.
- Burkina Faso