Sub- continental lithospheric mantle deformation in the Yerer-Tullu Wellel volcanotectonic lineament: A study of peridotite xenoliths.

摘要

Volumetrically, the lithospheric mantle comprises the bulk of the continental lithosphere, yet the mechanisms by which the lithospheric mantle is deformed during rifting are unresolved. Stretching and thermo-mechanical erosion are often cited mechanisms for facilitating lithospheric deformation during continental rift development; however, the infiltration of melt into the lithosphere during rift development also results in chemical alteration of the lithospheric mantle. The purpose of this study is to test the potential mechanisms by which the continental lithospheric mantle is chemically altered during rift development. Here we present a study of mantle xenoliths derived from the lithospheric mantle in Ethiopia that has been deformed during rifting. We find that the lithospheric mantle beneath the this zone exhibits evidence of focused magma-lithosphere interaction, resulting in four distinct types of peridotite xenoliths: a) deformed xenoliths representing the pre-deformation lithospheric mantle; b) granular xenoliths representing overprinted lithospheric mantle; c) replacement dunite xenoliths, evidence of pervasive melt-lithosphere interaction; and d) cumulate xenoliths representing remnants of a metasomatic agent. The deformed xenoliths exhibit a high Mg