Experimental duplication of a high-pressure megacryst/cumulate assemblage in a near-saturated hawaiite

Janice Knutson*, Trevor H. Green

*Corresponding author for this work

Research output: Contribution to journalArticle

46 Citations (Scopus)


The occurrence of corroded megacrysts and cumulates of olivine, clinopyroxene, orthopyroxene, plagioclase, ilmenite and apatite in near-saturated hawaiites from the mid-north coast of New South Wales point to the derivation of these hawaiites at elevated pressures. In an experimental study on one of these hawaiites under conditions ranging from 5-15 kb and 0-5% H2O, orthopyroxene was identified in only one run with 2% H2O at 1040° C and 6.5 kb. In this run it was associated with olivine, clinopyroxene and Fe-Ti oxide. The early appearance of plagioclase in the "dry" experimental runs and amphibole in runs with 5% H2O, indicates that the water content in the natural hawaiite was intermediate to these values. The near-duplication of the natural megacryst-cumulate assemblage suggests that the hawaiite host precipitated these phases at a depth of approximately 20-24 km, prior to rapid eruption to higher crustal levels.

Original languageEnglish
Pages (from-to)121-132
Number of pages12
JournalContributions to Mineralogy and Petrology
Issue number2
Publication statusPublished - Jun 1975


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