The Tectonic Evolution of Central and Northern Madagascar and Its Place in the Final Assembly of Gondwana

Abstract

Recent work in central and northern Madagascar has identified five tectonic units of the East African Orogen (EAO), a large collisional zone fundamental to the amalgamation of Gondwana. These five units are the Antongil block, the Antananarivo block, the Tsaratanana sheet, the Itremo sheet, and the Bemarivo belt. Geochronological, lithological, metamorphic, and geochemical characteristics of these units and their relationships to each other are used as a type area to compare and contrast with surrounding regions of Gondwana. The Antananarivo block of central Madagascar, part of a broad band of pre‐1000‐Ma continental crust that stretches from Yemen through Somalia and eastern Ethiopia into Madagascar, is sandwiched between two suture zones we interpret as marking strands of the Neoproterozoic Mozambique Ocean. The eastern suture connects the Al‐Mukalla terrane (Yemen), the Maydh greenstone belt (northern Somalia), the Betsimisaraka suture (east Madagascar), and the Palghat‐Cauvery shear zone system (south India). The western suture projects the Al‐Bayda terrane (Yemen) through a change in crustal age in Ethiopia to the region west of Madagascar. Our new framework for the central EAO links the Mozambique belt with the Arabian/Nubian Shield and highlights the power of tectonic analysis in unraveling the complex tectonic collage of the EAO.