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Petrological influence on differential weathering and inselberg development in the Kora area of central Kenya
Author(s) -
Pye K.,
Goudie A. S.,
Watson A.
Publication year - 1986
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3290110106
Subject(s) - migmatite , gneiss , weathering , geology , geochemistry , outcrop , metasomatism , metamorphic rock , mantle (geology)
In the Kora area of central Kenya domed inselbergs are well developed on outcrops of granitoid migmatite, while positive relief features are rare on the surrounding gneiss. Block‐strewn, vegetated hills occur on restricted areas of granoblastite, gabbro, and metagabbro. Schmidt Hammer measurements have shown that the apparent differences in resistance to weathering and erosion are not due to variations in rock hardness, since all the rock types have similar ‘R’ values. The results of geochemical analyses have shown that the migmatites are significantly more potassic than the surrounding gneiss. Samples of migmatite from the inselbergs were also found to be slightly richer in potassium than migmatite samples from the inter‐inselberg areas. The variations in potassium content probably reflect differences in protolith composition, chemical fractionation during partial melting, and the effects of metasomatism. These findings support earlier suggestions that, other things being equal, potassium‐rich granitoid rocks weather more slowly than less potassic rocks.