The Age and Evolution of the Lithospheric Mantle in the East Antarctic Craton: Osmium Isotope Composition and the Distribution of Platinum Group Elements in Spinel Lherzolite Nodules

Resumo

The mantle xenoliths of lherzolite composition from Mesozoic alkaline–ultrabasic diatremes of Jetty Oasis were studied. The treated xenoliths represent the mantle section of the East Antarctic Craton down to depths of 60–80 km. The osmium isotope composition of these nodules testifies to the beginning of the formation of the lithospheric mantle in the considered region of the craton 2400 Ma ago. The absence of any signs of Early Archeozoic lithosphere points either to partial destruction of the lithosphere at the convergent boundary of the plates in the Late Archean or to thermal erosion of the Archean lithosphere under the effect of a deep-seated plume in the Mesozoic during rift formation.