Lateritic weathering of granite-gneiss in Obudu Plateau, south eastern Nigeria

Abstract

Obudu Plateau (Latitudes 60 30`N, 6045`N and Longitudes 9015`E, 10000`E) is a basement Horst bordered in the East by the Cameroun volcanic line, both of which form the Bamenda massif. This is a zone of migmatite-gneissschist complex with subordinate occurrence of amphibolites, charnockites and minor intrusive of granites, dolerites
and Gabbros. Its tropical location pre-disposes it to climatic conditions (high temperature and pressures, heavy rainfall) that induce deep and severe weathering to form lateritic rocks. This paper reports the chemical, mineralogical and textural changes involved in the lateritization of granite-gneiss in Obudu plateau and establishes that the susceptibility of constituent minerals to lateritic weathering is in the sequence; feldspar, Hornblende, Biotite, Quartz. Most of the chemical constituents of the basement rocks in these changes. Al2O3 and Fe2O3 are enriched in the upper horizons in preference to SiO2. Kaolinite is also abundant compared to other clays whereas Ba takes the opposite trend as it increases with severity of weathering.