Mineralogies, densities and seismic velocities of garnet lherzolites and their geophysical implications

Jordan, Thomas H.

doi:10.1029/sp016p0001

Cited by 237 publications

(244 citation statements)

References 42 publications

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“…This depleted, less dense layer beneath Iceland hotspot was proposed by Jordan [32] in 1979. Because melt generated in the plume conduit migrates upward, the residual mantle left behind becomes more depleted and Mg-rich, and will be associated with a higher velocity [32][33][34]. The fast anomaly we imaged is centered at ~135 km depth, while the initial depth of melting beneath Iceland is estimated at ~110 km depth from geochemistry data [35], which is adopted in geodynamical modeling [29][30][31].…”

Section: Origin Of the Fast Anomalymentioning

confidence: 99%

Seismic structure of Iceland from Rayleigh wave inversions and geodynamic implications

Detrick

2006

Earth and Planetary Science Letters

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Section: Origin Of the Fast Anomalymentioning

confidence: 99%

Seismic structure of Iceland from Rayleigh wave inversions and geodynamic implications

Detrick

2006

Earth and Planetary Science Letters

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“…Temperatures in the mantle are thought to be lower under the craton compared with the surrounding mantle at the same depth [Jordan, 1988]. We may also expect a contrast in chemical composition across the edge with the material under the shield being more depleted than the surrounding [Jordan, 1981]. the lithospheric root region only, where we compare the deformed eratonic root containing partially oriented olivine with the hotter mantle around it, which we assume to be isotropic (randomly oriented olivine).…”

Section: Variable Thickness Anisotropic Lithospherementioning

confidence: 99%

Mantle variation within the Canadian Shield: Travel times from the portable broadband Archean‐Proterozoic Transect 1989

Bokelmann¹,

Silver²

2000

J. Geophys. Res.

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Abstract. We report travel times from the Archean-Proterozoic Transect 1989. This type of data set recorded by a transect of portable broadband instruments allows us to make inferences about mantle structure in the region between the Wyoming Craton and the Superior Province of the Canadian Shield. With station separations of 50 to 100 km and frequencies up to 5 Hz the resolution of lateral changes is increased by nearly an order of magnitude over previous studies to a scale that allows us to study the relation between velocity variation in the continental upper mantle, surface geology, tectonic features and age provinces. Travel times of direct and later phases are obtained from waveform matching. The values are corrected for crustal contribution and inverted for the vertical path upper mantle delay 5tUM under each station as well as the azimuthal dependence of this quantity. The prominent feature in the upper mantle delays 5tUM is the variation by at least 1.5 s for $, much of which occurs over a narrow zone of just a few hundred kilometers width. This suggests a major lateral upper mantle transition which does not coincide with the surface geological edge of the Canadian Shield but is located within the shield. This same transition is also observed in shear wave splitting delay times. Surprisingly, however, the P delays do not exhibit a corresponding variation. We address this apparent contradiction and show how it may be explained in conjunction with anisotropy in the subcontinental lithosphere. A simplified thermal model of the lithospheric transition zone, in which temperature controls the degree of crystallographic alignment and thus seismic anisotropy, predicts this phenomenon.

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“…•e ironrich component of olivine melts preferentially, leaving a magnesium-rich residuum (forsteritc or Fo) that is less dense but of higher seismic velocity [Jordan, 1979]. A change in peridotitc composition from Foss to Fo92, (~10% basaltic melt extraction) would cause a 1% increase in V•, [Jordan, 1979].…”

Section: Compositionmentioning

confidence: 99%

“…A change in peridotitc composition from Foss to Fo92, (~10% basaltic melt extraction) would cause a 1% increase in V•, [Jordan, 1979].…”

Section: Compositionmentioning

confidence: 99%

Upper mantle P wave velocity structure of the eastern Snake River Plain and its relationship to geodynamic models of the region

Saltzer¹,

Humphreys²

1997

J. Geophys. Res.

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Abstract. Tomographic inversions of ~5(• teleseismic P wave travel time residuals image a narrow, deep, low-velocity region centered beneath the eastern Snake River Plain, Idaho. Aligned in the direction of North American plate motion, the eastern Snake River Plain is the locus of time-progressive volcanism leading to the Yellowstone hotspot. The low-velocity anomaly extends to depths of at least 200 km and is flanked by high-velocity manfie to either side. These results are inconsistent with standard manfie plume models which predict a shallow, wide, low-velocity anomaly. By considering the effects of composition, partial me!t, and temperature on both P wave velocities and upper manfie densities (assnming local isostasy), we conclude that the low-velocity region is partially molten peridotitc and the high-velocity regions on either side are depletext residuum. Swell relief at hotspots has generally been attributed to thermal effects and is commonly used to estimate plume thermal buoyancy fluxes. However, we demonstrate that the compositional effects of manfie melting and depletion can account for at least one fifth and possibly all of the swell relief at Yellowstone. These results sa•est that melt generation and segregation are dominant pr•esses within the upper manfie of Yellowstone and allow for the possibility that the fundamental origin of the Yellowstone hotspot is something other than a deep-seated mantle plume.

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Mineralogies, densities and seismic velocities of garnet lherzolites and their geophysical implications

Cited by 237 publications

References 42 publications

Seismic structure of Iceland from Rayleigh wave inversions and geodynamic implications

Seismic structure of Iceland from Rayleigh wave inversions and geodynamic implications

Mantle variation within the Canadian Shield: Travel times from the portable broadband Archean‐Proterozoic Transect 1989

Upper mantle P wave velocity structure of the eastern Snake River Plain and its relationship to geodynamic models of the region

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