Controls of Basement Fabric on the Linkage of Rift Segments

Abstract

AbstractThe Rukwa and North Malawi Rift Segments (RNMRS) both define a major rift‐oblique segment of the East African Rift System and are often regarded as discrete rifts due to the presence of the uplifted Mbozi block between them. Here we investigate the influence of basement fabrics on the coupling and linkage of border faults across an interrift transfer zone between discrete juvenile rift segments. We utilized satellite digital elevation model to investigate the morphological architecture of the rift domains and aeromagnetic data to assess the relationships (plan view) between the rift structures and the prerift basement fabrics. Our results show that the present‐day morphology of the RNMRS is characterized by along‐rift alternation of rift shoulder polarity, characteristic of coupled rift segments. Interpretation of filtered aeromagnetic maps along the boundaries of the RNMRS reveals striking alignment of the rift‐bounding faults with colinear NW‐SE trending preexisting basement fabrics. We find that rift coupling along the NE boundary of the Mbozi transfer zone is accommodated by fault‐assisted magma plumbing, whereas coupling along the SW boundary is accommodated by strike‐slip and oblique‐normal faulting that reactivated the Proterozoic Mughese shear zone, within the collisional boundary between the Tanzania craton and the Bangweulu cratonic block. Further, we show how the configuration of the basement fabrics may influence the formation of rift bifurcation across inter‐rift transfer zones. We suggest that the structural connectivity of the boundary faults along the RNMRS and their alignment with colinear basement fabrics demonstrate the influence of structural inheritance on the amalgamation of approaching rift segments.