Relatore: Prof. Christoph A. Hauzenberg, University of Graz, Austria

Titolo: Mantle xenoliths from Thailand, Laos and Vietnam

Contenuti: A large basaltic province with numerous eruption centers developed during the Neogene on the southeast Asian peninsula. In many cases, these basalts contain a variety of xenoliths, mainly of mantle origin, as well as a megacryst suite consisting mainly of clinopyoxene, zircon, and sapphire/corundum. The alkaline basaltic eruption centers are typically characterized by small and highly eroded volcanic cones covered by dense vegetation. The mantle fragments consist mainly of spinel lherzolites and harzburgites, and less commonly pyroxenites and wehrlites. These xenoliths represent portions of the subcontinental lithospheric mantle (SCLM) from different depths beneath southeast Asia, for which thermobarometry yields ~800-1100°C and ~0.7-1.6 GPa, corresponding to depths of ~26-54 km. Mineral textures and phase compositions, as well as clear evidence of modal metasomatism (phosphates, carbonates, silicates) within the mantle xenoliths, indicate different stages of metasomatism, including infiltration of P-REE-CO2-rich melts with low aH2O and alkali-rich silicate melts with basaltic affinity just prior to eruption.