Using an advanced seismic velocity–temperature conversion technique, we infer the temperature and melt distribution
in the uppermantle (down to 300 km) beneath Italy and surroundings, starting from absolute S-wave
velocity models. The presence of melt, indicated by the seismic reconstruction of the mantle structure in the
Tyrrhenian Sea area, requires an extension of the standard conversion procedure to allow for a correction of
seismic velocities for the effect of hydrous melt occurrence.
The thermal structure of the upper mantle along four sections crossing the Tyrrhenian basin and the Italian
peninsula is investigated. Some characteristics of the obtained thermal structures and melt distributions
are well delineated and in accordance with recent models of the evolution of the Tyrrhenian Sea area. The
negative thermal anomalies observed in all sections clearly delineate the subduction process of the Adriatic
plate (beneath Umbria, Calabria and the Aeolian arc), or the episode of post-continental convergence
(beneath Tuscany), or the thermal effect of the remnant of the Adriatic plate (Campania).
Temperature values at Moho seem to be generally correlated with surface heat flow determinations in the
Tyrrhenian Sea area and surroundings, although most sectors of the study area (like Tuscan–Tyrrhenian
area, Apennines and Adriatic trough) have not yet reached the steady-state thermal regime. The thermal
gradients evaluated in the Adria foreland are high in comparison with those of the back-arc area (Tyrrhenian
Sea) and could be an effect of the eastward mantle flow beneath Adria lithosphere or a result of the presence
of low fraction of melts ≤1 wt.%, which cannot rise in compressive regimes, or both.
The melt fraction distribution obtained by the conversion procedure is approximately correlated with the age
of the magmatism, the highest abundance occurring in the southern Tyrrhenian Sea, in accordance with
widespread active volcanism in this area.
