Abstract Neogene volcanism is widespread in northern Victoria Land, and is part of the McMurdo Volcanic Group. It is characterized by multiple coalesced shield volcanoes but includes a few relatively small stratovolcanoes. Two volcanic provinces are defined (Hallett and Melbourne), with nine constituent volcanic fields. Multitudes of tiny monogenetic volcanic centres (mainly scoria cones) are also scattered across the region and are called the Northern Local Suite. The volcanism extends in age between middle Miocene ( c. 15 Ma) and present but most is <10 Ma. Two centres may still be active (Mount Melbourne and Mount Rittmann). It is alkaline, varying between basalt (basanite) and trachyte/rhyolite. There are also associated, geographically restricted, alkaline gabbro to granite plutons and dykes (Meander Intrusive Group) with mainly Eocene–Oligocene ages (52–18 Ma). The isotopic compositions of the plutons have been used to infer overall cooling of climate during the Eocene–Oligocene. The volcanic sequences are overwhelmingly glaciovolcanic and are dominated by ‘a‘ā lava-fed deltas, the first to be described anywhere. They have been a major source of information on Mio-Pliocene glacial conditions and were used to establish that the thermal regime during glacial periods was polythermal, thus necessitating a change in the prevailing paradigm for ice-sheet evolution.

Abstract In various ancient authors (e.g. the ‘Argonautika’ of Apollonios Rhodios) curious news about the Island of Elba can be found, concerning the existence, somewhere on the shore near Portoferraio, of pebbles that are ‘dirty’ from the Argonauts’ sweat. The Argonauts are said to have stopped on the island during their journey back from the looting of the ‘Golden Fleece’. These pebbles are found to be typical of the gravelly beaches below the Capo Bianco cliffs. Such walls are made up of a bony-white aplitic rock dotted with blue-black tourmaline spots. Capo Bianco aplite is the uncommon result of the solidification of a boron-rich magma in a subvolcanic setting. Here, the separation of a boron-rich fluid phase gave way to the crystallization of peculiar spherical dark tourmaline clots in a very fine-grained white groundmass. This rock was noted by Argonauts (i.e. the ancient travellers they represent) and used as a lighthouse to the harbour of Argoos limen (now Portoferraio). Also in the myth, the unique mottled pebbles were recorded as stained by the Argonauts’ sweat. The occurrence, within the same, complex myth, of ‘data’ concerning navigation (the white cliffs) and geology (description of the spotted aplite) identify the Argonauts as a blending of mineral prospectors, explorers and early eighteenth century-like naturalists, legitimatizing the commercial/political presence of Greeks in the region.

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 µ, 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 shoulder in this area. The faults were active at their Ross Sea termination in Cenozoic time, coeval with magma emplacement, as demonstrated by the ca. 34 Ma age of a pseudotachylyte generated in the right-lateral fault system exposed in northern Victoria Land. Middle Eocene activity is also inferred for the Pacific termination of the faults from apatite fission track thermochronology. In a wider perspective, these faults are in striking continuity with Southern Ocean fracture zones, and mantle tomography depicts a thermal anomaly of linear (not circular) shape overlapping the belt of the same fracture zones, suggesting that the anomaly is related to lithospheric geometry and movements rather than to deep plumes. The lack of any decisive evidence for plume activity is thus associated with the evidence that large-scale tectonic features drove magma emplacement: the Cenozoic fault systems reactivated Paleozoic tectonic discontinuities, and their activity is dynamically linked to the Southern Ocean fracture zones. As an alternative to both active (plume-driven) rifting and passive rifting, we propose that lithospheric strike-slip deformation could have promoted transtension-related decompression melting of a mantle already decompressed or veined during the Late Cretaceous amagmatic extensional rift phase.