Evidence from oceanic gabbros for porous melt migration within a crystal mush beneath the Mid‐Atlantic Ridge
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In this article, the evolution of a gabbroic crystal mush under the Mid-Atlantic Ridge has been investigated using evidence from gabbros recovered from Ocean Drilling Program (ODP) Hole 923A (Leg 153).Abstract:
[1] The evolution of a gabbroic crystal mush beneath the Mid-Atlantic Ridge has been investigated using evidence from gabbros recovered from Ocean Drilling Program (ODP) Hole 923A (Leg 153) Lithological variations occur on a vertical scale of meters and correlate with mineral compositions This defines a detailed chemical stratigraphy in which variations in olivine, plagioclase, and clinopyroxene solid-solution component compositions correlate with each other The volumetrically dominant lithology (plagioclase + clinopyroxene ± olivine ± orthopyroxene gabbros) has variable grain size, grain shape, and mineral compositions These variations correlate, such that coarser grained samples have more granular textures and lower mafic phase Mg/Fe ratios than adjacent finer grained samples Clinopyroxene trace element systematics, determined by ion probe, cannot be explained by growth from a melt that evolved along either an equilibrium or a fractional crystallization trend Clinopyroxene crystals are strongly zoned and enriched in Zr with respect to rare earth elements (more to less incompatible elements) These textural and geochemical characteristics are not expected from simple crystal accumulation processes or the crystallization of trapped melt Instead, melt migration within a crystal mush is suggested as the most likely process to explain them The meter-scale mineral compositional variations, which correlate between phases (eg, olivine forsterite content and plagioclase anorthite content), suggest that the porous melt flux after the formation of this layering was insufficient to destroy this correlationread more
Citations
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Melt–rock reaction in the lower oceanic crust and its implications for the genesis of mid-ocean ridge basalt
TL;DR: This paper showed that high-Mg# clinopyroxene in the Kane gabbros formed as a result of reaction between primitive cumulates and migrating melt in the lower oceanic crust.
Journal ArticleDOI
Near-solidus evolution of oceanic gabbros: insights from amphibole geochemistry
TL;DR: In this article, the major and trace element compositions of amphiboles in a suite of gabbros from the Mid-Atlantic Ridge were used to discriminate between amphiboles of magmatic and hydrothermal origin.
Journal ArticleDOI
Geochemical and petrographic evidence for magmatic impregnation in the oceanic lithosphere at Atlantis Massif, Mid-Atlantic Ridge (IODP Hole U1309D, 30°N)
TL;DR: In this article, a trace element study was carried out on a series of olivine-rich troctolites, and neighbouring troctolis and gabbros, from olivines-rich intervals in Hole U1309D, and the results indicated that clinopyroxene and plagioclase crystallized concurrently, after melts having the same trace element composition.
Journal ArticleDOI
Pervasive reactive melt migration through fast-spreading lower oceanic crust (Hess Deep, equatorial Pacific Ocean)
TL;DR: In this article, the authors demonstrate that the evolution of lower crustal rocks exposed in Hess Deep (equatorial Pacific Ocean) is controlled by reactive porous flow, leading to a strong enrichment in, and fractionation of, incompatible trace elements in the melt (as recorded by clinopyroxene compositions).
Journal ArticleDOI
Multi-stage melt-rock interaction in the Mt. Maggiore (Corsica, France) ophiolitic peridotites: microstructural and geochemical evidence
TL;DR: Spinel and plagioclase peridotites from the MtMaggiore ophiolitic massif record a composite asthenosphere-lithosphere history of partial melting and subsequent multi-stage melt-rock interaction.
References
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