Hydrothermal deposits have been suggested as locations of high importance in the search for fossilized forms of ancient biota on Earth [Walter and Des Marais, 1993]. They occur where spatially confined warm (50 O) to hot (500O) fluids are in disequilibrium with their host rocks [Piranjo, 1992]. By the action of such a system, solutes can be concentrated to form ores at certain horizons within or on the surface of a rock body. Such concentrations may be developed where a drop in temperature, pressure, or alteration of the permeability or chemistry of the host rocks created conditions suitable for the solute to be precipitated from the hot fluid.

Hydrothermal systems usually feature layered horizons of altered rocks which are able to be detected using hyperspectral remote sensing surveys [Huntington, 1996]. Such a survey has recently been carried out in northern Western Australia. The target of this survey was the North Pole Dome, a 600 sq. km region of the ancient Pilbara craton. The survey was conducted over a half day period using the Hymap instrument [Cocks et al., 1998].

Geological evidence suggests the North Pole Dome underwent alteration during the Archean by a shallow marine low temperature hydrothermal system [Nijman et al., 1998]. The hydrothermal system was heated by a magmatic intrusion causing crustal doming and partial convective overturn [Van Kranendonk, 2000].

The North Pole Dome encloses many prominent stromatolite horizons [Hoffman et al., 1999]. The opportunity to correlate stromatolite horizons and alteration mineral occurrences is a compelling attraction of the Pilbara site.

The objectives of this project are threefold. (1) The VNIR-SWIR remote dataset will be analysed and followed up with further on site surveys with hand held SWIR spectrometers. The utility of particular alteration mineral assemblages and spatial arrangements of such horizons in a hydrothermal system will be assessed. (2) A model of the hydrothermal system will be constructed, following methods suggested by earlier researchers [eg. Griffith and Shock, 1997]. (3) A Martian analog of such a hydrothermal system will be developed using software simulation, with the aim of predicting alteration features that may be visible by a spatially fine grained (5m GIFOV) SWIR hyperspectral instrument in orbit around the planet. References

Project