Polyphase Deformation in the Mozambique Belt, Northern Malawi
Malawi is mainly within the Malawi Province of the Mozambique Belt, which is now divided into northern and southern sub-provinces. In the northern sub-province, the Ubendian and Irumide belts also occur and all three belts can be described within the framework of two major metamorphic/structural events. The first event consists of at least four episodes of mainly plastic deformation and medium- to high-grade metamorphism. Age determinations indicate that the Ubendian Orogeny (? 2100 to 1950 m.y.) occurs within the later episodes of this event; earlier episodes may reflect older orogenies. The first event is separated from the second event by the unconformable deposition of the psammitic sediments of the Mafingi Group, which is, therefore, a Precambrian marker of major importance. The second event consists of four episodes of mainly brittle deformation in the green-schist facies. The Irumide Orogeny (? 1300to 1100 m.y.) and the Mozambique Orogeny (? 700 to 400 m.y.) occur within the second event.