Abstract
Metallic ores of economic values often occur within profiles above basement rocks in tropical regions due to weathering and secondary enrichment. This study is carried out to determine the geochemistry and appraise the potential for metallic ore enrichment in the weathered profiles over Syenite and Younger Granite in Pankshin area. Top-soil, laterite and rock samples are collected from two lateritic profiles above Syenite and Younger Granite. The syenite rock is composed of alkali feldspars (perthite), nepheline, clinopyroxene, with minor amount of orthopyroxene, hornblende, plagioclase and few quartz grains, indicating oversaturation. The Younger Granite contains plagioclase feldspars, microcline, quartz, biotite, hornblende and reibeckite. Quartz (61.0%), kaolinite (32.0%) and microcline (7.0%) are the dominant minerals in the X-ray diffraction (XRD) of the decomposed rocks. The Chemical Index of Alteration (CIA) of both rocks is generally >90. There are enhancements of V, Sc, Zr and TiO2 in the Syenite profile and Fe2O3, Zr, V and TiO2 in the Younger Granite profile as reflected in the Accumulation Factor (AF), loss and gain of elements (K), though the values were too low for ore mineralization except for iron and titanium in the Younger Granite profile.
Highlights
The chemical compositions of laterite within a soil profile vary according to the nature of the rock
This study is carried out to determine the geochemical characteristics of the lateritic profiles over syenite and Younger Granite in Pankshin area in order to appraise their economic potentials in terms of metallic ore enrichment
The sequioxide ratio (SR) and alumina-iron oxide ratio (AR) values in this study strongly suggest that true laterite is produced only from the weathering of the Younger Granite
Summary
The chemical compositions of laterite within a soil profile vary according to the nature of the rock. Pankshin area in the north central part Nigeria (Figure 1) is underlain by migmatite, granite gneiss, basalt, Syenite and Younger Granite (Figure 2). Previous studies in the area are mainly on the tin-bearing Jurassic Younger Granites (Macleod, 1971; Turner, 1989) with little attention on the residual profiles over other rock types (Du Preez, 1956; Tietz, 1983; Matheis, 1983; Valeton & Beissner, 1986; Zeese, 1991; Bernhard & Tietz, 1997). Metallic ores of economic values often concentrated within lateritic profiles above basement rocks in tropical regions due to supergene enrichment. This study is carried out to determine the geochemical characteristics of the lateritic profiles over syenite and Younger Granite in Pankshin area in order to appraise their economic potentials in terms of metallic ore enrichment
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