SEGMeNT: Study of Extension and maGmatism in Malawi aNd Tanzania


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Summary of the project on NSF’s website

Supported by NSF-Continental Dynamics

The SEGMeNT project is a multidisciplinary, multinational study focused on the northern Malawi (Nyasa) rift that includes characterizing deformation and magmatism in the crust and mantle lithosphere along several rift segments, quantifying temporal patterns in deformation, and evaluating the source of magmas.  The northern Lake Malawi (Nyasa) region in the East African Rift System is an excellent locality to examine early-stage rifting at slow rates in strong, cold lithosphere. Only a small amount of stretching has occurred, and it appears that rifting is occurring in relatively cold, strong continental lithosphere. It exhibits pronounced tectonic segmentation, which is defined in the upper crust by ~100-km-long border faults rifting is occurring in relatively strong lithosphere. Very little volcanism is associated with rifting, providing a serious test for recent models that require intrusive magmatism to initiate rifting in cold, strong continental lithosphere. Strikingly, the only surface expression of magmatism in this system occurs in an accommodation zone between segments rather than in a segment center, in clear contrast to MORs and mature rifts. This relationship is also observed elsewhere in the Western Rift of the East Africa Rift system and in other early-stage rifts, but the 3D distribution of magma at depth and its role in extension are unknown in all cases. Rifting is associated with significant seismic and volcanic hazards for the densely populated rift valley.

In the SEGMeNT program, we are acquiring a suite of geophysical, geological and geochemical data to better understand this rift system. This program includes: 1) geochemical analysis and dating of rocks from the Rungwe volcanic province north of Lake Malawi to constrain the origin and age of magmas, 2) GPS and InSAR study to measure opening rates and active tectonic processes, 3) onshore/offshore deployment of passive seismic network for lithospheric imaging of deformation and magmatism, and to constrain seismicity, 4) acquisition of magnetotelluric data for lithospheric imaging, particularly detection of magmas and fluids, 5) onshore/offshore active source seismic data acquisition to image sedimentary and crustal structure within and around the lake.