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Along‐Axis Variations of Rift Width in a Coupled Lithosphere‐Mantle System, Application to East Africa
Author(s) -
Koptev Alexander,
Calais Eric,
Burov Evgueni,
Leroy Sylvie,
Gerya Taras
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl077276
Subject(s) - rift , geology , east african rift , lithosphere , mantle plume , mantle (geology) , geothermal gradient , plume , crust , geophysics , hotspot (geology) , transition zone , seismology , tectonics , geography , meteorology
Narrow and wide rifts are end‐member expressions of continental extension. Within the framework of passive rifting, the transition from wide to narrow rifts requires lowering the geothermal gradient. Reconciling this view with observational evidence for narrow rift zones in regions underlain by sublithospheric hot plume material, such as the eastern branch of the East African Rift, requires invoking preexisting weak zones for strain to localize in a warm crust. Based on thermomechanical numerical models, we show that along‐rift width variations can develop spontaneously as a consequence of spatial variations of the geotherm over an evolving mantle plume impinging a lithosphere subjected to ultraslow extension. The eastern branch of the East African Rift, with a narrow Kenya segment underlain by a mantle plume head and widening to the north and south in the colder regions of the Turkana depression and North Tanzania divergence, is in agreement with this numerical prediction.