Results 251 to 260 of about 771,265 (286)

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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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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Heterogeneity of the Upper Mantle: ABSTRACT

AAPG Bulletin, 1963
In their investigations of the interior of the earth, geophysicists have generally regarded the mantle as composed of homogeneous shells and have considered the crust of the earth as varying laterally in composition and thickness. Evidence from measurements of the gravitational field and of the heat flow to the surface have suggested that differences ...
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Upper mantle heterogeneities and dynamics

Nature, 1985
The width of geochemical and residual elevation anomalies along the Mid-Ocean Ridge System decrease as both the distance between migrating ridge segments and related hotspots and the local geochemical dispersion in the anomalies increase. These observations provide further evidence that flows of mantle plumes in the upper mantle are deflected by ...
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Short-Lived Chemical Heterogeneities in the Archean Mantle with Implications for Mantle Convection

Science, 1994
The neodymium isotope and samarium-neodymium systematics of 2.7-billion-year-old mantle-derived magmas indicate that the lifetime of chemical heterogeneities was much shorter in the Archean mantle than in the modern mantle. Isotopic evidence is compatible with a Rayleigh number 100 times larger and convection 10 times faster in the Late Archean ...
J, Blichert-Toft, F, Albarede
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A mantle heterogeneity in the Southwest Pacific

Tectonophysics, 1988
Abstract The occurrence in time and space of Tertiary intraplate central volcanoes and associated lava fields in the eastern Australia-New Zealand-Campbell Plateau region of the Southwest Pacific is more consistent with derivation from a large-scale mantle anomaly than from discrete plumes.
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HETEROGENEITY OF THE UPPER MANTLE

International Geology Review, 1992
A. V. Yegorkin, S. L. Kostyuchenko
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The survival of mantle geochemical heterogeneities

2005
The survival of mantle geochemical heterogeneities depends on the relative values of the residence times of individual elements in the mantle and of the scale-dependent mixing rate imposed by convection. Major and trace element data on fresh glasses from the PETDB data base were compiled to extract statistics on MORB compositions. It was found that the
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Modeling a Heterogeneous Mantle

Science, 2002
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