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Water and partial melting in mantle plumes: Inferences from the dissolved H 2 O concentrations of Hawaiian basaltic magmas
Author(s) -
Wallace Paul J.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl02805
Subject(s) - geology , plume , basalt , mantle (geology) , olivine , upwelling , partial melting , mantle plume , geochemistry , silicate , melt inclusions , mineralogy , lithosphere , oceanography , chemistry , thermodynamics , paleontology , physics , tectonics , organic chemistry
Knowledge of dissolved H 2 O in primary Kilauean magmas provides a constraint on H 2 O abundance in the deep mantle region that feeds the upwelling plume beneath Hawaii. Given an H 2 O/K 2 O mass ratio of ∼1.3 for basaltic glasses and melt inclusions from Kilauea, the mantle source is estimated to contain 450±190 ppm H 2 O. This value is ∼3 times greater than that estimated for the mantle source for mid‐ocean ridge basalts. Consideration of OH solubility in olivine suggests that water undersaturated melting of the upwelling Hawaiian plume probably begins at a depth of ∼250 km. Thus during plume ascent through most of the upper mantle, water is partitioned between nominally anhydrous silicates and a small mass fraction of entrained hydrous silicate melt. Because water strongly influences the viscosity of olivine aggregates, partial melting and melt extraction will have important effects on the rheology of the upwelling plume beneath Hawaii.