Marie Byrd Land lithospheric mantle: a review of the xenolith record

Abstract

AbstractThe Marie Byrd Land (MBL) lithospheric mantle xenolith record comprises over 100 samples from a range of localities spanning both major crustal terranes that comprise MBL: Ross and Amundsen provinces. Coarse granular to porphyroclastic in texture, the xenoliths are predominantly Type I spinel-bearing lherzolites to harburgites, but include rare dunite and pyroxenite examples. Garnet is absent and no hydrous phases, such as amphibole or mica, have been reported to date, although traces of apatite may be present. Characterisation of the lithospheric mantle composition and its evolution however, is hampered by patchy and uneven geochemical analyses across the xenolith suite. Nonetheless, a picture emerges of a heterogeneous lithosphere beneath both Ross and Amundsen Provinces. Previously published and new data reported here are consistent with samples ranging from variably cryptically metasomatized residua from variable (10–25%) degrees of partial melt extraction to refertilized compositions. Limited isotopic data point to a complex history, providing evidence for both ancient Proterozoic lithospheric mantle and preservation of Ordovician events. The Sr–Nd–Pb composition of the sampled lithospheric mantle overlaps the common low-µ isotopic endmember identified in Cenozoic magmatism from MBL and the wider West Antarctic Rift System.