Abstract A thermo-rheological model of the Monte Capanne pluton, Elba Island, Italy is proposed as having general relevance for the thermal and tectonic evolution of upper crustal granites and their surrounding rocks in extensional regions. The thermal evolution of the pluton and country rocks is followed for 1 myr after emplacement, which occurred at c. 6.9 Ma. The pluton completely crystallized in c. 210 kyr (±20%). The adjacent rocks reached a thermal peak of 550 °C (±10%), maintaining a temperature higher than 500 °C for c. 100 kyr. The temperature distribution is used to construct a model for the time-dependent rheology of the pluton and surrounding rocks. A series of 2D cross-sections shows an upward migration of the regional brittle−ductile transition, and the formation of a ductile horizon above the pluton. The former is a combined effect of unroofing and middle crust heating; the latter is the result of temperature increase in rheologically weak country rocks. This ductile horizon has a potential role in the tectonic evolution of the region, since it could favour the formation of upper crustal shear zones and listric faults rooting in the transient brittle−ductile transition and playing a major role in further post-emplacement extension.

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.