Results 1 to 10 of about 9,129 (164)

Small-Scale Heterogeneities of the Upper Mantle

1997
Models derived from controlled source seismology (reflection and refraction data) and long-period seismology provide the impression that the upper mantle is rather homogeneous. For near-vertical reflections the mantle appears transparent if compared to the reflective lower crust.
Wenzel, Friedemann, Fuchs, Karl, Tittgemeyer, Marc, Ryberg, Trond   +3 more
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Confidence regions for mantle heterogeneity

Journal of Geophysical Research: Solid Earth, 1994
Least squares tomographic models of mantle P and S velocity structure from travel times have shown large‐scale variations correlated with surface tectonic features, as well as coherent structures in the lowermost mantle. The reliability of these global features of velocity models depends on whether velocity throughout the features can be estimated well
R. Jay Pulliam, Philip B. Stark
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Deep subduction and mantle heterogeneities

Deep Sea Research Part B. Oceanographic Literature Review, 1987
Abstract The globe-encircling isotopic anomaly centred on latitude 30°S defined from the geochemistry of mid-ocean ridge and particularly intraplate basalts has been previously shown to be correlative with degree-2 features of the Earth's geoid. The same region appears to show a correlation with zones of low seismic velocities, perhaps indicative of ...
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Lateral heterogeneity in the convecting mantle

Journal of Geophysical Research: Solid Earth, 1986
Thermally induced lateral heterogeneity in the earth's mantle has been studied in terms of idealized two‐dimensional, constant viscosity, numerical models of mantle convection. Steady model solutions of the temperature and velocity fields were analyzed with respect to both the spatial and spectral signatures of their inherent lateral heterogeneity.
G. T. Jarvis, W. R. Peltier
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Chemical and seismological constraints on mantle heterogeneity

Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 2002
Recent seismological studies that use scattered waves to detect heterogeneities in the mantle reveal the presence of a small, distributed elastic heterogeneity in the lower mantle which does not appear to be thermal in nature. The characteristic size of these heterogeneities appears to be ca.
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Imaging Mantle Heterogeneity with Upper Mantle Seismic Discontinuities

2015
We use underside reflections of S wave seismic energy arriving as precursors to the seismic phase SS to image the depth and impedance contrast present across mantle discontinuities in the depth range of 230–380 km beneath the Pacific basin . A number of past studies have identified seismic discontinuities at these depths, known as the X-discontinuities,
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Seismic heterogeneity in the upper mantle

Journal of Geophysical Research: Solid Earth, 1994
This paper gives an overview of recent seismological evidence on heterogeneity in the upper mantle. While there is a growing consensus among seismologists on the low‐order spherical harmonic expansion of upper mantle structure, short‐ and intermediate‐wavelength features remain the subject of intense debate.
G. Nolet, S. P. Grand, B. L. N. Kennett
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Metallogenesis in relation to mantle heterogeneity

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 1980
Abstract Regional variations in the type and abundance of metalliferous mineral deposits formed at a given time depend on environmental factors operating not only at the sites of deposition but also in the source regions supplying the metals.
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Chromium isotope heterogeneity in the mantle

Earth and Planetary Science Letters, 2017
Abstract To better constrain the Cr isotopic composition of the silicate Earth and to investigate potential Cr isotopic fractionation during high temperature geological processes, we analyzed the Cr isotopic composition of different types of mantle xenoliths from diverse geologic settings: fertile to refractory off-craton spinel and garnet ...
Xia, Jiuxing, Qin, Liping, Shen, Ji, Carlson, Richard W., Ionov, Dmitri, Mock, Timothy D.   +5 more
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Lateral heterogeneity and mantle dynamics

Nature, 1975
Recent work on the nature of the Earth's lateral heterogeneities yields two conclusions with implications for mantle dynamics: seismic velocity differences between continents and oceans extend to depths exceeding 400 km, and strong lateral velocity gradients at depths greater than 800 km characterise the mantle beneath many subduction zones.
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