Mineralogical and geochemical properties of clay deposits in parts of Southeastern Nigeria

Abstract

The rocks underlying many parts of Southeastern Nigeria had undergone extensive alterations to form considerable clay deposits. The mineralogical compositions of some of these clay deposits were evaluated with the X-Ray Diffraction (XRD) method to ascertain the suitability of the deposits as raw materials. Results of the analyses indicated that kaolinite (Al2Si2O5 (OH)4) is the dominant clay mineral. Traces of bentonite and dickite were also observed, while the identified non-clay minerals were quartz and iron. Chemical analysis of the clays revealed the predominance of SiO2, Al2O3, Fe2O3 and TiO with values ranging from 31.70 to 56.45%, 19.30 to 29.30%, 3.11 to 29.42% and 2.21 to 7.04%, respectively, while the compositions of CaO, MgO, Na2O, and MnO in the analyzed samples were relatively lower with values ranging from 0.19 to 0.29%, 0.13 to 0.19%, 0.11 to 0.70% and 0.01 to 0.03%, respectively. The Al2O3/TiO2 ratio (3.7 to 13.5) of the studied clays indicated a mafic to intermediate igneous rock origin. Binary plots of TiO2 versus Al2O3 to distinguish between granitic and basaltic sourced clays indicated basalt-rhyolite/granite provenances. The high chemical index of alteration (95.8%), chemical index of weathering (98.3%) and low contents of alkali and alkali earth elements (averaging 0.11%) of the clay-rich sediments, is indicative of a relatively intense weathering source area. The SiO2-K2O/Na2O plots suggested that the sediments in the study area were deposited between passive and active continental margins. In comparison with other reference clays and standard specifications, the clay deposits in the study area possess characteristics satisfactory for economic and some engineering purposes. Key words: Chemical, clay, deposits, economic, mineralogical, potentials, provenance.