There are a number of intrinsic properties of cratons unified in their pre-dispersal position in Gondwana. Exposure of deep crustal levels of this supercontinent is an essential precursor to continental weathering being vital to the on set and nature of the continental weathering process itself. These cratonal attributes include: the petrological and imeralogical character of the bedrock parent material, its unique thermal history, depletion in water and heat-producing elements, uplift, erosion and ultimate stability necessary for attainment of a state of tectonic quiescence when subjected to intense weathering. This transcontinental belt of deep continental crust exposed as graulite-charnockite-anorthosite bodies parallels the Gondwanide Orogen of Paleozoic and Early Mesozoic plate convergence affecting South America, Africa, India, Australia and Antarctica implicating Gondwana supercontinental scale weathering as the appropriate crustal unit of analysis rather than individual continental land masses. The necessity of viewing lateritic weathering on a supercontinental scale is further accentuated by the fact that the classical "residual" origin of lateritic bauxites is inconsistent with a recent discovery that wind-blown foreign dust consisting of gibbsite, hematite and goethite also bearing a component of resistant detrital minerals derived from basement rocks elsewhere (zircon, ilmenite, rutile and monazite) dominates near surface metal enrichment of bauxites and laterites. By considering the crustal processes preceding continental weathering as well as the surficial recycling and redistribution of chemically-resistant minerals accessed as a direct consequence of the petrology and mineralogy of the deep crust, we have formulated a testable model of deep crustal weathering systems. An integrated three-part project is planned addressing (1) the provenance of chemically-stable detrital minerals, especially zircon contaminating the upper portions of laterites, (2) age and duration of lateritic weathering in combination with correlations of paleo-weathering surfaces in Australia, West Africa and Brazil, and (3) mechanisms of subsurface transport and incorporation of detritus into the lateritic regolith during dilational biomechanical mixing of eolian dust by root growth cycles. Part I utilizes U-Pb ion microprobe dating of zircon using the SHRIMP to define the sources of mobile minerals and the depths of their translocation into laterite and bauxite weathering profiles. Part II involves 40Ar/39Ar laser dating of jarosite as well as manganese and iron oxides. Part III is laboratory experimentation using a soil mechanics cell capable of simulation root growth cycles. The proposed interdisciplinary research can contribute to further development of a much-needed long-term continental record of surficial environments to complement the marine stratigraphic record of global processes.
