APATITE, PHOSPHORUS AND TITANIUM IN ECLOGITIC GARNET FROM THE UPPER-MANTLE

The existence of apatite exsolution lamellae in garnet supports earlie r suggestions that garnet is a major repository for P in the mantle, a nd that P is strongly coupled to Na+Ti. The bulk P content (approximat ely 250 ppm) of mantle eclogites is unexpectedly similar to estimates for the P content (130-220 ppm) of the upper mantle; both rocks are de pleted relative to chondrites and to ocean floor basalts. Eclogites ha ve either equilibrated with the mantle at large, or have undergone sec ondary melting, and based on P contents are unlikely to have had subdu cted protoliths.