The logic is that it would have been subducted as a function of plate tectonics billions of years ago, then encased in a forming diamond deep in the mantle, and ultimately sent back up near the surface again. (manyworlds.space)
Entitled «Geological History of the Turkana Basin,» this workshop covered topics such as plate tectonic setting of the Turkana Basin, relation of the Turkana Depression to the Ethiopian Rift and Kenya Rift, timing of major faulting, sedimentary sequences, dating of volcanic sequences, volcanic rocks and volcanic history, geochemistry of ancient lakes, and geology and its relation to paleontology. (turkanabasin.org)
This is a unit study on plate tectonics in geology or earth science subject. (tes.com)