Petrology and mineralogy of ‘laterites’ in southern and eastern Australia and southern Africa

Brownish yellow saprolite derived from granite gneiss is exposed beneath 1–2 m of reddish brown till along a roadcut in the Cape Breton Highlands. The strongly acid soil is similar to other Podzolic soils of the region except for the presence of gibbsite in the silt and clay fractions. In the saprolite, feldspar and biotite have weathered to poorly crystalline kaolinite, gibbsite, and a minor component of iron oxide. The poorly crystalline kaolinite does not occur in the overlying till.The evidence presented is consistent with the view that the area was covered either by "cold-based" or by stagnant "warm-based" glaciers that eroded the pre-Quaternary surface only slightly and deposited a thin, discontinuous veneer of till derived mainly from local bedrock and saprolite. Weathering products from the saprolite are probably incorporated commonly in tills of the area. During the formation of soils in these tills the poorly crystalline kaolinite and most of the gibbsite are either transformed to other minerals or dissolved and removed in solution.

Saprolite

Gibbsite

Bedrock

Parent rock

Silt

Mylonite

Parent material

10.1139/e83-004

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Citations (30)

Geochemical differentiation in laterite and bauxite formation

CATENA (1994)

W. Schellmann

Laterite

Gibbsite

Bayer process

Diaspore (botany)

Saprolite

Boehmite

10.1016/0341-8162(94)90007-8

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Citations (81)

A Cretaceous laterite in the Negev Desert, southern Israel

Geological Magazine (1975)

Arieh Singer

Summary Kaolinite is the major mineral in the saprolite of a fossil laterite, found intercalated amid basalt flows from the Lower Cretaceous in the Negev desert. The kaolinite was produced by pseudomorphic alteration of plagioclase. Haematite is a secondary product and accumulated in a ferruginous soil horizon. In the saprolite Sr, Mn and Cu were strongly depleted, Zn and Ni were slightly depleted, whereas Co and Cr accumulated. In the ferruginous horizon, Sr, Mn, Cu and Zn were severely depleted, while Cr and Ni accumulated. The lateritic formation is evidence for the possible existence of tropical or intertropical conditions during the Lower Cretaceous in the Negev.

Saprolite

Laterite

10.1017/s0016756800045830

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Citations (18)

A critique of the Schellmann definition and classification of ‘laterite’

CATENA (2002)

Robert P. Bourman Clifford Ollier

Laterite

Saprolite

Regolith

Bedrock