Articles | Volume 8, issue 1
Solid Earth, 8, 45–81, 2017
Solid Earth, 8, 45–81, 2017

Research article 16 Jan 2017

Research article | 16 Jan 2017

The Kenya rift revisited: insights into lithospheric strength through data-driven 3-D gravity and thermal modelling

Judith Sippel1, Christian Meeßen1,2, Mauro Cacace1, James Mechie1, Stewart Fishwick3, Christian Heine4, Magdalena Scheck-Wenderoth1, and Manfred R. Strecker2 Judith Sippel et al.
  • 1GFZ German Research Centre for Geosciences, Sections 6.1 & 2.2, Telegrafenberg, 14473 Potsdam, Germany
  • 2Institute of Earth and Environmental Science, University of Potsdam, 14476 Potsdam, Germany
  • 3Department of Geology, University of Leicester, Leicester, LE1 7RH, UK
  • 4New Ventures, Upstream International, Shell International Exploration & Production B.V., 2596 HR, The Hague, the Netherlands

Abstract. We present three-dimensional (3-D) models that describe the present-day thermal and rheological state of the lithosphere of the greater Kenya rift region aiming at a better understanding of the rift evolution, with a particular focus on plume–lithosphere interactions. The key methodology applied is the 3-D integration of diverse geological and geophysical observations using gravity modelling. Accordingly, the resulting lithospheric-scale 3-D density model is consistent with (i) reviewed descriptions of lithological variations in the sedimentary and volcanic cover, (ii) known trends in crust and mantle seismic velocities as revealed by seismic and seismological data and (iii) the observed gravity field. This data-based model is the first to image a 3-D density configuration of the crystalline crust for the entire region of Kenya and northern Tanzania. An upper and a basal crustal layer are differentiated, each composed of several domains of different average densities. We interpret these domains to trace back to the Precambrian terrane amalgamation associated with the East African Orogeny and to magmatic processes during Mesozoic and Cenozoic rifting phases. In combination with seismic velocities, the densities of these crustal domains indicate compositional differences. The derived lithological trends have been used to parameterise steady-state thermal and rheological models. These models indicate that crustal and mantle temperatures decrease from the Kenya rift in the west to eastern Kenya, while the integrated strength of the lithosphere increases. Thereby, the detailed strength configuration appears strongly controlled by the complex inherited crustal structure, which may have been decisive for the onset, localisation and propagation of rifting.

Short summary
The Kenya Rift is a zone along which the African continental plate is stretched as evidenced by strong earthquake and volcanic activity. We want to understand the controlling factors of past and future tectonic deformation; hence, we assess the structural and strength configuration of the rift system at the present-day. Data-driven 3-D numerical models show how the inherited composition of the crust and a thermal anomaly in the deep mantle interact to form localised zones of tectonic weakness.