Extensive Lateritic
Duricrust Co-Ni target areas identified.
6c): (1) water percolation through and evaporative salt concentration within the Cenozoic sediments, with associated salt scald development around the periphery of remnant Cenozoic gravels and
duricrusts; (2) partially confined lateral flow through the pallid deep weathering profile (paleosol) formed on metasedimentary rocks, underlying the Cenozoic
duricrust, where flows intercept the salt partitioned into the weathering profile as it is formed; (3) localised land salinisation at the break in slope; and (4) behind subsurface impediments to flow (structural controls), as observed at the other localities.
The lithology is made up of lateritic
duricrust terranes, migmatites and gneisses (ortho), schist referred to as the Lom Schist belt (Figure 3(c)), metaleucogranites, meta-granodiorites, porphyritic granites (Figure 3(b)), fine grained granites, and some pegmatite veins [1].
There is also a small proportion (<1%) of microcrystalline (matrix) silcrete (the
duricrust silcrete of Morwood 1981).
The intact lateritic profile was mostly formed by weathering of granitoids and other rock types and these profiles commonly consist of sand and pisolitic gravels over lateritic
duricrust (cemented ferruginous material), mottled and pallid zones (quartz and clay rich materials), saprolite and saprock (isovolumetrically weathered materials with retention of parent rock fabric), and rock (Anand and Paine 2002).
Calcretes (caliche, hardpan,
duricrust) are formed mainly in semiarid and arid regions and consist of hard, dense deposits of secondary carbonates that occur as nodules, lumps, crusts, or thick concrete-like layers in the lower soil zone.
The remobilization process of gold in savannah systems and particularly in
duricrust profiles occurs over different lengths of time and under differing hydrologic and physico-chemical conditions than in more humid climates.
Many mission scientists think they may be similar to the sulfur- and chlorine-rich
duricrust deposits seen at the Viking landing sites.
Iron oxide cemented materials (Zh) are usually removed during bauxite mining and constitute the
duricrust and friable zones (Fig.
Anand RR, Gilkes RJ (1987) Variation in the properties of iron oxides within individual specimens of lateritic
duricrust. Australian Journal of Soil Research 25, 287-302.