Provenance of shales and sandstones from the Devonian Accraian Group, southern Ghana

摘要

Petrographic and whole rock geochemical studies were carried out on sandstones and shales of the Devonian Accraian Group of southern Ghana to constrain their provenance and tectonic setting. Modal petrographic analysis on the sandstones show that the framework grains are sub-angular to rounded in shape. Upper continental crust normalized multi-element plots, as well as trace element ratios, suggests that the sandstones and shales were mainly derived from felsic and recycled sources. Modal mineralogy of the sandstones, and major and trace element geochemistry of sandstones and shales further suggest that they are of recycled orogenic provenance. Discriminant function based major-element diagram suggests that the Accraian sandstones and shales were deposited in a Passive margin setting. Weathering indices suggest high degree of source area weathering. It is of the view that the Accraian sandstones and shales, most probably, received sediment input mostly from the Paleoproterozoic Birimian metasedimentary rocks and their associated granitoids and/or the Neoproterozoic sedimentary rocks from the Volta Basin which are both positioned northwest and north, respectively, of the Accraian sedimentary rocks.