High-pressure reactive melt stagnation recorded in abyssal pyroxenites from the ultraslow-spreading Lena Trough, Arctic Ocean

Georgi Laukert, Anette Von Der Handt, Eric Hellebrand, Jonathan E. Snow, Peter Hoppe, Andreas Klügel

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Pyroxenites are an essential component in petrological and geochemical models for melt formation at mid-ocean ridges and ocean islands. Despite their rarity, their origin has been widely discussed and various processes have been invoked for their formation. Here, we present a detailed study of the microtextures and major, minor and trace element compositions of relatively fresh pyroxenites and associated harzburgites from the ultraslow-spreading Lena Trough, Arctic Ocean. Microtextural and geochemical characteristics suggest an origin by magmatic assimilation-fractional crystallization with a high ratio of mass crystallized to mass assimilated.The major element compositions of pyroxenes suggest that this process occurred at high pressures (>0.7 GPa), although interstitial plagioclase in two of the pyroxenites indicates that melt-rock reaction continued at lower pressures.The parental melt to the pyroxenites was most probably depleted mid-ocean ridge basalt similar to basalts from the North Lena Trough and westernmost Gakkel Ridge; basalts from the Central LenaTrough cannot have functioned as parental melts. The melt was generated close to the garnet-spinel facies transition by variable degrees of partial melting and reacted with the local refractory harzburgite. Pyroxenites from this study provide further evidence, together with plagioclase-bearing and vein-bearing peridotites, for significant melt stagnation below the Lena Trough that occurred over a range of depths, either continuously or stepwise. Comparison with abyssal pyroxenites reveals common characteristics, suggesting that, consistent with results of high-pressure crystallization experiments, they mark the onset of (reactive) crystallization of melts passing through the deeper parts of the mid-ocean ridge plumbing system.

Original languageEnglish (US)
Pages (from-to)427-458
Number of pages32
JournalJournal of Petrology
Volume55
Issue number2
DOIs
StatePublished - Feb 2014

Bibliographical note

Funding Information:
J.E.S. was supported by NSF grant OCE 0648567.

Keywords

  • Arctic Ocean
  • Major and trace elements
  • Melt-rock reaction
  • Pyroxenite
  • Ultraslow-spreading ridge

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