Abstract:
The Wa-Lawra Belt which is situated in the northern part of Ghana consists of
Paleoproterozoic Birimian fine metasedimentary rocks metamorphosed to greenschist facies,
particularly, in the western part. A whole-rock geochemical study of these metasedimentary
rocks was undertaken to unravel their source area weathering, provenance and tectonic
setting. Geochemical characteristics of the studied shales show that they are immature in
nature and first cycle in origin, with little or no recycled component. Compared to Post-
Archaean Australian Shales (PAAS), the studied shales indicate reduction in Zr, Hf, La, Nb, Th
and Ta being the high field strength elements and evidences of transition metal enrichments
in V, Ni, Sc, Co, and Cr. Major element geochemistry indicates that the shales were subjected
to slight potassium metasomatism after deposition. Pre-metasomatized Chemical Index of
Alteration calculations indicates that weak to moderate degree of chemical weathering took
place at the sediment source area. Co-Th-La-Sc systematics reveals a combination of mafic
and felsic provenances for the shales. Eu/Eu* together with values of Th/U and some
abundances of trace elements show that the shales were mainly derived from juvenile
rocks. Average REE model calculations suggest that the source materials are composed of
about 49% basalt, 16% TTG and 35% granite.
