Composition and Crystallization Temperatures of Primary Melts from Hole 896A Basalts: Evidence from Melt Inclusion Studies

Glass and mineral geochemical data are presented for basalts from Ocean Drilling Program (ODP) Hole 896A.Phenocryst assemblages are dominated by calcic plagioclase (An 76 _ 945 ) with olivine (Fo 80 _ 91 6 ), Cr-Al spinel, and clinopyroxene.The origin of the calcic plagioclase phenocrysts was investigated by heating-stage experiments on silicate melt inclusions in plagioclase and olivine mineral separates.Trapping temperatures of 1195°-1215°C are inferred for plagioclase (An 83 _ 945 ).Inclusion compositions, interpreted to be in equilibrium with host plagioclase, are similar to the range of pillow-rim glasses from this hole.Primary melts, in equilibrium with Fo 9 | 6 , are estimated to have -15 wt% MgO and crystallization temperatures of ~1340°C.