PERIDOTITES FROM THE PARECE VELA RIFT IN THE PHILIPPINE SEA - UPPER-MANTLE MATERIAL EXPOSED IN AN EXTINCT BACK-ARC BASIN

Serpentinized peridotites and gabbros were dredged from the axial zone of the Parece Vela Basin during a cruise of SN Takuyo in 1995. The ce ntral zone of the Parece Vela Basin is characterized by the NS trendin g chain of depressions forming right-step en-echelon alignment. Our pe trological studies suggest that the peridotites are residues of extens ive partial melting of primitive mantle peridotites. Presence of hydro us phases in the peridotites indicates that the peridotites were subje cted to metasomatic event in the upper mantle beneath the Parece Vela Rift.