Cratonwide Overlap Assemblage Shamvaian Group

The shamvaian Group consists of a sequence of coarse clastic rocks that overlie the upper Greenstones in several locations. These conglomerates, arkoses, and graywackes are well known from the Harare, Midlands, Masvingo, and Belingwe greenstone belts. The Cheshire Formation, the top unit of the Belingwe greenstone belt, consists of a heterogeneous succession of sedimentary rocks including conglomerate, sandstone, siltstone, argillite, limestone, cherty limestone, stromatolitic limestone, and minor banded iron formation. The shamvaian Group is intruded by the circa 2.6 billion-year-old Chilimanzi suite granites, providing an upper age limit on deposition. In the Bindura-Shamva greenstone belt the Shamvaian Group is 1.2 miles (2 km) thick, beginning with basal conglomerates and grading up into a thick sandstone sequence. Tonalitic clasts in the basal conglomerate have yielded igneous ages of 3.2, 2.9, 2.8, and 2.68 billion years. Felsic volcanics associated with the Shamvaian Group in several greenstone belts have ages of 2.66 to 2.64 billion years.

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