Receiver function investigation of crustal structure in the Malawi and Luangwa rift zones and adjacent areas

Abstract

Stacking over 2300 P-to-S receiver functions recorded by 33 SAFARI (Seismic Arrays for African Rift Initiation) broadband seismic stations that we installed in the vicinity of the Malawi and Luangwa rift zones (MRZ and LRZ, respectively) reveals significant variations of crustal thickness (32.8–46.3 km) and Vp/Vs (1.69–1.85). The resulting crustal stretching factor is about 1.05–1.08 for the MRZ, which is approximately 10–40% lower than that observed in the mature segments of the East African Rift System (EARS). The low stretching factor is consistent with the general absence of volcanism in the MRZ, and the relatively high Vp/Vs (≥ 1.81) beneath the southern MRZ, when combined with observations from previous studies, indicate the possible existence of crustal partial melting, elevated temperatures or fluid-filled deep crustal faults that are likely associated with lithospheric stretching. In sharp contrast with the southern MRZ, low Vp/Vs measurements in the range of 1.69–1.72 are observed along the western boundary of the northern MRZ, which could be attributable to the infiltration of magma-derived CO2 into the crust. The LRZ shows negligible crustal thinning and a Vp/Vs that is comparable to the globally averaged value for continental crust, suggesting a complete post-rifting recovery of crustal properties in terms of crustal thickness and Vp/Vs.

Department(s)

Geography, Geology, and Planning

Document Type

Article

DOI

https://doi.org/10.1016/j.gr.2020.08.015

Keywords

Crustal structure, Luangwa Rift Zone, Malawi Rift Zone, Receiver function

Publication Date

1-1-2021

Journal Title

Gondwana Research

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