Non plume, no rift magmatism in the West Antarctic rift.

The West Antarctic Rift system is one of the largest areas of crustal extension in the world. Current interpretations of its driving mechanisms rely mostly on the occurrence of one or more mantle plumes that was active during the Cenozoic or the Mesozoic. The plume hypotheses are mainly based on the similarity between the basalts from the West Antarctic Rift and those associated with long-lived hotspot tracks. The geochemical signature of the mafic rocks is indeed typical of ocean island basalts (OIB), from a source with a tendency to high , i.e., high U/Pb (HIMU) mantle. However, these features cannot be exclusively interpreted in terms of a plume sampling very old slab material recycled at great depth for a long time (10^9 yr): a metasomatic event at a time on the order of 10^8 yr (i.e., Cretaceous) is sufficient to have produced the required source features. Geometric-chronological relationships between magmatism and local tectonic activity further constrain the scenario. In Victoria Land, the occurrence of plutons, dike swarms, and volcanic edifices since the Middle Eocene indicates that magma emplacement is guided by the dextral strike-slip fault systems that dissect the rift mantle already decompressed or veined during the Late Cretaceous amagmatic extensional rift phase.