Magmatic evolution and tectonic setting of metabasites from Lützow-Holm Complex, East Antarctica

Metabasites from the Lutzow-Holm Complex, East Antarctica, are the equivalent of metamorphosed ultramafic and mafic rocks with ultrabasic to intermediate compositions, which occur as layers and blocks in the quartzo-feldspathic or metasedimentary gneisses. Field occur- rences and whole-rock geochemistry suggest that the ultramafic rocks are all cumulitic protoliths, whereas the mafic rocks are mostly basaltic protoliths including some cumulates. Moreover, in a regional context, the geochemistry of metabasites shifts from island arc to ocean-floor affinities in a southwesterly direction from the Prince Olav Coast to the Lutzow-Holm Bay area. Neodymium isotopic data suggest that the metamorphic rocks from the Prince Olav Coast and the northern Lutzow-Holm Bay areas were derived from immature continental crust formed by active Meso- proterozoic crustal growth, whereas those from the southern Lutzow-Holm Bay area were derived from mature continental crust and oceanic crust of older age. Thus, these results suggest that the Lutzow-Holm Complex includes lithological units with various origins and ages that were amalgamated by multiple subduction, and underwent high-grade metamorphism as a result of the final collision of East and West Gondwana during the Pan-African orogeny.