Weathering

The old continental nucleus of Western Australia, known as the Yilgarn Craton, is >2500 million years old and today is a wide, flat, largely featureless terrain. Australia's present location at 20-30° south latitude places it in the globally extensive low latitude arid region caused by the descending masses of dry, high pressure air in the 'horse latitudes' (see the Desert Module elsewhere on this CD). The Western Australia desert seldom has well developed sand dunes; instead it is characterized by highly evolved and drought resistant plants and extensive deflation surfaces covered with pebble to cobble sized rocks.

Interspersed with these types of desert landscapes are large playa lakes surrounded and underlain by very salty soils and deposits. All these surfical weathering effects are superimposed on an Archean craton that has abundant mineral deposits (primarily gold and nickel) which are now hidden beneath deeply weathered regolith. This can be seen in all three of the panoramas as a variably developed red-brown alteration cap extending to depths of 30 meters or more surrounding the pit rims.

Such deep weathering in the arid desert gradually becomes an equally deep tropical weathering profile as one works northward across Australia. Learning to identify minerals and rocks in such profoundly altered crust is an art in itself and is of critical importance to explorationists seeking new mineral deposits.