Abstract
We found possible prograde deserpentinized peridotites from the Happo complex central Japan. High-P and low-P prograde peridotites show differences in their field relation and mineral assemblage. The high-P prograde peridotites have a mineral assemblage, Opx + Olv + Tlc + rare edenite and phlogopite. Olivine has low Fo91, in contrast to olivine in the low-P deserpentinized peridotites from the talc zone, due to a reducing environment. Their bulk chemistry confirms serpentinites as a protolith. The low-P, high-T peridotites metamorphosed by Cretaceous granitic intrusion from the talc zone are composed of prograde tremolite, metamorphic olivine, antigorite and talc. Prograde tremolite is very low in Al2O3,Na2O,Cr2O3,Li,La,Ce,Sr,Ti,Yb,Sc,and V, but is high in SiO2 and Mg# relative to retrograde tremolite. This depletion of mobile elements is due to their mobility during deserpentinization process, whereas immobile-element depletion is related to the parental source. Olivine containing opaque inclusions is high in Fo, 93.5 to 96.4. It is enriched in B,Sc,Ti,Y,Zr,Nb and Ni relative to mantle olivines because of its opaque inclusions.
