The subantarctic lithospheric mantle

Abstract

We present a summary of peridotite in the Subantarctic (46 to 60°S) surrounding the Antarctic Plate. Peridotite xenoliths occur on Kerguelen and Auckland islands. Kerguelen islands are underlain by a plume whereas the Auckland Islands are part of continental Zealandia, which is a Gondwana-rifted fragment. Small amounts of serpentinised peridotite has been dredged from fracture zones on the Southeast Indian, Southwest Indian, and Pacific Antarctic Ridge, and represents upwelled asthenosphere accreted to form lithosphere. Supra-subduction zone peridotite has been collected from two locations on the Sandwich Plate. Peridotites from most Subantarctic occurrences are moderately to highly depleted, and many show signs of subsequent metasomatic enrichment. Os isotopes indicate that the Subantarctic continental and oceanic lithospheric mantle contains ancient fragments that underwent depletion long before formation of the overlying crust.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5424956

An introduction to the geochemistry and geophysics of the Antarctic mantle

“…Studies of mantle xenoliths on the subantarctic islands have greatly informed our understanding of the mantle but are included too infrequently in discussions on the Antarctic mantle. Delpech et al (2021) review the information from mantle xenoliths afforded by these island windows into the mantle, as well as discussing serpentinized peridotite dredged from fracture zones and suprasubduction zone peridotite from the Sandwich Plate. They show that the subcontinental and oceanic lithospheric mantle contains ancient fragments that underwent depletion significantly earlier than the formation of the overlying crust, and there are frequent signs of subsequent metasomatic enrichment.…”