ENSIALIC ORIGIN FOR THE NGEZI GROUP, BELINGWE GREENSTONE-BELT, ZIMBABWE

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