Lithospheric Structure Underneath the Archean Tanzania Craton and Adjacent Regions from a Joint Inversion of Receiver Functions and Rayleigh-Wave Phase Velocity Dispersion


Lithospheric structure beneath the Archean Tanzania craton and adjacent regions, including segments of the East African rift system (EARS) and the Proterozoic-early Paleozoic orogenic belts between the EARS and the craton, is imaged by a joint inversion of receiver functions and Rayleigh wave dispersion measurements derived from ambient seismic noise for shorter periods and teleseismic data for longer periods. Our resulting crustal thickness, crustal VP= VS measurements and 3D shear-wave velocity model for the upper 120 km show a clear spatial correspondence with major surficial geological features. The new results suggest the presence of a mafic layer in the bottom of the crust of the entire Archean craton, which is previously only identified beneath the southern portion of the craton. High crustal VP= VS values measured in the Rungwe Volcanic Province and most areas of the Kenya and Tanganyika rift segments can be attributed to a combined result of basaltic sediments atop the crust, magmatic intrusion, and crustal partial melting. The Kivu Volcanic Province and parts of the Kenya rift segment are characterized by localized lower-than-normal crustal VP= VS values and shear velocities in the lower crust and uppermost mantle, which, given the presence of large volume of CO2 from surficial observations, can be best interpreted by CO2-filled fractures or conduits. Lower-than-normal shear velocities in the uppermost mantle are revealed beneath almost the entire study region with the lowest values found in all the three volcanic provinces. The lowvelocities are indicative of an underplated layer formed by mantle-derived magmatic materials trapped below the Moho. The relatively low velocities beneath the volcanic provinces might be caused by a higher degree of partial melting in the uppermost mantle.


Geosciences and Geological and Petroleum Engineering


IRIS Data Services are funded through the Seismological Facilities for the Advancement of Geoscience (SAGE) Award of the National Science Foundation (NSF) under Cooperative Support Agreement EAR‐1851048. The study was partially supported by the U.S. NSF under Grants 1009946 to K. L. and S. G., 1919789 to S. G., and the American Chemical Society under Grant PRF‐60281‐ND8 to S. G.

International Standard Serial Number (ISSN)

1938-2057; 0895-0695

Document Type

Article - Journal

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Publication Date

01 May 2022