TY - JOUR
T1 - High-pressure reactive melt stagnation recorded in abyssal pyroxenites from the ultraslow-spreading Lena Trough, Arctic Ocean
AU - Laukert, Georgi
AU - Von Der Handt, Anette
AU - Hellebrand, Eric
AU - Snow, Jonathan E.
AU - Hoppe, Peter
AU - Klügel, Andreas
N1 - Funding Information:
J.E.S. was supported by NSF grant OCE 0648567.
PY - 2014/2
Y1 - 2014/2
N2 - 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.
AB - 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.
KW - Arctic Ocean
KW - Major and trace elements
KW - Melt-rock reaction
KW - Pyroxenite
KW - Ultraslow-spreading ridge
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U2 - 10.1093/petrology/egt073
DO - 10.1093/petrology/egt073
M3 - Article
AN - SCOPUS:84930384809
SN - 0022-3530
VL - 55
SP - 427
EP - 458
JO - Journal of Petrology
JF - Journal of Petrology
IS - 2
ER -