What exactly are you trying to locate in the study area? Mineral deposits? Where is the study area? What is the vegetation cover? And what data forms are you using?

I prospecting for mineral deposits using Landsat ETM+ images. The area is located in Sudan and it is approximately free of vegetation.

Do you know the signature of the deposits or the associated minerals?

One more thing, does sand cover the materials you are looking for?

yes, you can use Aster remote sensing

" ASTER standard data products, and applications of the most recently developed image processing methods applied to ASTER data as a tool for mapping hydrothermal alteration mineral zones associated with porphyry copper and epithermal gold mineralization and related host-rock lithology."

Consider using L band radar if your areas are covered with sand. L band sees through sand to materials below due to it's long wavelength. Keep in my that with all other data products, you are seeing only the surface sand/dirt/ veg/ rock whatever. Aster is great, but I am a fan of believing the more data, the better the project!

I use a variety of methods when exploring data. I like using Sprectral Angle Mapper (SAM) but I also like using Minimum Noise transform (MNF). Both are available in ENVI.

thanks for all responses, special thanks are due to Susan Buckingham