Equilibration during mantle melting: a fractal tree model.

Hart, Stanley R.

doi:10.1073/pnas.90.24.11914

Cited by 127 publications

(87 citation statements)

References 34 publications

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“…[27] The self-similar,``fractal'' branching of this hypothetical network is similar to that proposed by Hart [1993] Figure 5B. In the numerical model a solvent enters the bottom boundary of the model, and rises through a partially soluble, viscously compacting porous medium.…”

Section: Discussionmentioning

confidence: 52%

Spatial distribution of melt conduits in the mantle beneath oceanic spreading ridges: Observations from the Ingalls and Oman ophiolites

Kelemen

Braun

Hirth

2000

Geochem Geophys Geosyst

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[1] Ophiolites are on-land exposures of igneous crust and residual upper mantle formed beneath submarine spreading ridges. Upper mantle outcrops in ophiolites provide insight into focusing of melt transport from a $100 km wide region of partial melting into an $5 km wide zone of igneous crustal accretion beneath the ridges. Dunite veins, composed of the minerals olivine and spinel, mark conduits for melt transport through at least the uppermost 30 km of the mantle. New data in this paper, on dunite veins in the Ingalls ophiolite, central Washington Cascades, show a power law relationship between frequency and width, in which frequency/m %0.02 width À3 over a size interval from $0.1 to 2 m. There may be several ways to generate this relationship, but we favor the hypothesis that the dunites represent a coalescing melt transport network. This conclusion is broadly consistent with the related hypothesis that mantle melt extraction occurs in a fractal, branching network, and with recent results on formation of a coalescing network of dissolution channels via flow of a solvent through a partially soluble, compacting porous medium.

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Section: Discussionmentioning

confidence: 52%

Spatial distribution of melt conduits in the mantle beneath oceanic spreading ridges: Observations from the Ingalls and Oman ophiolites

Kelemen

Braun

Hirth

2000

Geochem Geophys Geosyst

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“…Suffice to say that melts that are being erupted in close proximity on-axis may have sampling domains that are large and distinct in the Z-direction (especially with a fractal plumbing system; Hart, 1993).…”

Section: Case B: the Very-slow-spreading Sw Indian Ridgementioning

confidence: 99%

Scale length of mantle heterogeneities: Constraints from helium diffusion

Hart

Kurz

Wang

2008

Earth and Planetary Science Letters

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A model of coupled He production/diffusion is used to constrain the question of whether Earth's peridotitic mantle contains ubiquitous mesoscale veins or slabs of other lithologies. The high diffusion rates of helium preclude survival of He isotope heterogeneities on scales smaller than a few tens of meters, especially if they represent long term in-growth of 4 He in the mantle. He variability for these 3 areas is very small, and independent of spreading rate: 0. 13, 0.19 and 0.21 Ra (±1σ). Since these ridges range from ultraslow to very fast-spreading, the variability in size of along-axis magma chambers will lead inevitably to various scales of melt averaging. We conclude that these ridge areas are not sampling mantle that contains enriched veins or recycled oceanic crust slabs of significant size (> tens of meters). It appears difficult to sustain a view of the upper mantle as a ubiquitous mixture of veins and depleted matrix, with MORB always representing an averaging of this mixture.

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“…A non-dimensional scaling of melt production rate to equilibration rate by diffusion with solids provides an estimate of the mantle melting conditions required for equilibration (Hart, 1993;Figure 2.10). At tm/tD=l, the melt produced would achieve -83% of melt equilibration with the mantle minerals.…”

Section: Morb Generationmentioning

confidence: 99%

Kinetic processes of mantle minerals

Koga¹

1999

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This dissertation discusses the experimental results designed to constrain the processes of MORE generation. The main focus of this study is to investigate the location and the related processes of the transformation boundary from spinel to garnet peridotite facies at subsolidus conditions, because the presence of garnet in melting residues has significant influence to the conclusion drawn from geochemical/geophysical observations. Using an approach that monitors the rate of reaction progresses, the experimental results confirmed the presence of a region that garnet and spinel coexist in peridotite compositions. The trace element distribution among the product phases (opx and cpx) subsequent to the garnet breakdown reaction is in disequilibrium, due to the differences of diffusivity between major and trace elements. The presence of disequilibrium distribution in nature may be used to infer time scales of geodynamic processes. Diffusion coefficients of Al in diopside are experimentally determined, and used for modeling the equilibration of major elements in pyroxene during MORE genesis. In summary, this dissertation contributes two major inferences: the location of the transformation boundaries of the gamet-spinel peridotite; the presence of disequilibrium trace elements distribution with equilibrium major elements distribution in mantle pyroxenes.3

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Equilibration during mantle melting: a fractal tree model.

Cited by 127 publications

References 34 publications

Spatial distribution of melt conduits in the mantle beneath oceanic spreading ridges: Observations from the Ingalls and Oman ophiolites

Spatial distribution of melt conduits in the mantle beneath oceanic spreading ridges: Observations from the Ingalls and Oman ophiolites

Scale length of mantle heterogeneities: Constraints from helium diffusion

Kinetic processes of mantle minerals

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