Abstract

Volcanic rocks of the Ngezi Group in the Belingwe greenstone belt have been interpreted as continental basalts extruded onto, or oceanic crust obducted onto, a succession of stable-shelf sedimentary rocks that nonconformably overlie continental basement. The volcanic succession locally contains quartzose sandstones, and the stratigraphy is unlike ocean crust. Primary volcanic and sedimentary structures indicate a shallow-subaqueous to subaerial origin. All structural features are compatible with later refolding of an autochthonous successon; there is no structural manifestation of obduction. These criteria refute an oceanic setting for the volcanic rocks; rather, they are consistent with an ensialic origin for the Ngezi Group.

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