Near-solidus melting of the Shallow Upper Mantle: Partial melting experiments on depleted peridotite

Laura E. Wasylenki, Michael B. Baker, Adam J.R. Kent, Edward M. Stolper

Research output: Contribution to journalArticlepeer-review

210 Scopus citations

Abstract

We present the results of melting experiments on a moderately depleted peridotite composition (DMMI) at 10 kbar and 1250-1390°C. Specially designed experiments demonstrate that liquids extracted into aggregates of vitreous carbon spheres maintained chemical contact with the bulk charge down to melt fractions of ∼0·02-0·04 and approached equilibrium closely. With increasing melt fraction, SiO2, FeO*, and MgO contents of the partial melts increase, Al2O3 and Na2O contents decrease, and CaO contents first increase up to clinopyroxeneout at a melt fraction of 0·09-0·10, then decrease with further melting. A linear fit to melt fraction vs temperature data for Iherzolite-bearing experiments yields a solidus of 1272 ± 11°C. The melting reaction is 0·56 orthopyroxene + 0·72 clinopyroxene + 0·04 spinel = 0·34 olivine + 1 liquid. Above clinopyroxene-out, the reaction is 1·24 orthopyroxene = 0.24 olivine + 1 liquid. Near the solidus, DMMI glass compositions have lower SiO2, TiO2, Na2O, and K2O contents, higher FeO*, MgO, and CaO contents, and higher CaO/Al2O3 ratios compared with glasses from low-degree melting of fertile peridotite compositions. Recent computational models predict partial melting trends generally parallel to our experimental results. We present a parameterization of 10kbar peridotite solidus temperatures suggesting that K2O and P2O5 have greater effects on solidus depression than Na2O, consistent with theoretical expectations. Our parameterization also suggests that abyssal peridotites have 10 kbar solidi of ∼1278-1295°C.

Original languageEnglish (US)
Pages (from-to)1163-1191
Number of pages29
JournalJournal of Petrology
Volume44
Issue number7
DOIs
StatePublished - Jul 2003
Externally publishedYes

Keywords

  • Depleted
  • Experimental petrology
  • Mantle melting
  • Near-solidus
  • Peridolite

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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