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Hydrogen partition coefficients between nominally anhydrous minerals and basaltic melts
Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA
Department of Terrestrial Magnetism, Carnegie Institute of Washington, Washington, D. C., USA
Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota, USA
We have measured hydrogen partition coefficients between nominally anhydrous minerals (olivine, pyroxenes) and basaltic melts in 13 hydrous melting experiments performed at upper mantle P-T conditions (1–2 GPa and 1230–1380°C). Resulting liquids have 3.1–6.4 wt.% H2O and average mineral/melt partition coefficients as follows: D H ol/melt = 0.0017 ± 0.0005 (n = 9), D H opx/melt = 0.019 ± 0.004 (n = 8), and D H cpx/melt = 0.023 ± 0.005 (n = 2). Mineral/mineral partition coefficients are D H ol/opx = 0.11 ± 0.01 (n = 4), D H ol/cpx = 0.08 ± 0.01 (n = 2) and D H cpx/opx = 1.4 ± 0.3 (n = 1). These measurements confirm that water behaves similarly to Ce during mantle melting (D H peridotite/melt is ∼0.009). For mantle water concentrations of 50–200 ppm, the onset of melting is 5–20 km deeper than the dry solidus, less than previous estimates.
Received 24 August 2004; accepted 11 October 2004; published 30 October 2004.
Citation: (2004), Hydrogen partition coefficients between nominally anhydrous minerals and basaltic melts, Geophys. Res. Lett., 31, L20611, doi:10.1029/2004GL021341.
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