ASTER Mineral Mapping

ASTER satellite imagery was collected over most of the world in a period from 2000 to 2008. Good quality cloud-free imagery exists in archive for most arid or semi-arid zones. Even in tropical and temperate/boreal zones, some useful geological information can be obtained if cloud-free or low-cloud imagery is available. ASTER has a similar spatial resolution to LANDSAT at 15-30m pixel. The big difference is that ASTER has 6 bands of data in the Short-Wave Infra-Red (SWIR) compared to LANDSAT's 2 bands. This allows better discrimination of mineralogical types via Remote Sensing. MMSL has developed an in-house method - ASTER Mineral Mapping.The ASTER Mineral Map can be used for mapping alteration zones in hydrothermal type mineralisation in volcanic terranes as well as general geological mapping. Three examples are shown here with epithermal gold and porphyry copper areas in the Zagros volcanic arc of Iran, a volcanogenic massive sulphide (VMS) base metal deposit in the Arabian/Nubian shield and a Nickel bearing laterite deposit over a Proterozoic age ultramafic body in Central Africa. ASTER Mineral Mapping is also useful for general lithological mapping of sedimentary and metamorphic lithologies. Other rock types that can be discriminated using ASTER Mineral Mapping include Dolomites and Evaporites.

 

Zagros Volcanic Arc

A copper bearing porphyry system has a central phyllic zone (Phyllic and Phyllic/Goethitic) with discrete argillic zones (Argillic and Argillic/Haematitic) and a peripheral propylitic zone (darker CPS). Epithermal gold deposits are also shown as Argillic, Argillic/Goethitic as well as carbonates in the country rocks (brighter CPS).

Arabian-Nubian Shield

A copper bearing VMS deposit underlies an area of Phyllic/Goethitic alteration. ASTER mineral mapping does not ONLY map mineralogy in hydrothermal alteration. A good deal of the signatures mapped in this area are due to metamorphic lithologies such as greenschists that are mapped as CPS.

Central Africa

In this area, late Proterozoic age mobile belts contain ultramafic bodies. Where geologically recent tropical soils have been developed over these bodies, lateritic Nickel deposits can be formed. ASTER Mineral Mapping can map these by detecting the spectral features of serpentine minerals (dominantly CPS/Haematitic).