Results 161 to 170 of about 45,633 (206)

Deep subduction and mantle heterogeneities

Tectonophysics, 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 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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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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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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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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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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On the scale of mantle heterogeneity

Physics of the Earth and Planetary Interiors, 1992
Abstract A data set comprising 3313 residuals measured from digital records of 429 earthquakes is analyzed for the heterogeneity of the Earth's mantle. The smoothed SS residuals reveal a large pattern of heterogeneity and agree well with the major tectonic features on the Earth's surface and the residual patterns predicted by upper mantle and whole ...
Wei-jia Su, Adam M. Dziewonski
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Large mantle heterogeneity beneath French Polynesia

Nature, 1984
New strontium, lead and neodymium isotope compositions of volcanics from two volcanic island chains of French Polynesia (Marquesas, Australes) are presented. The data from Marquesas fall in the well-established oceanic islands field and are very similar to those of the Society Islands of French Polynesia.
Ph. Vidal, C. Chauvel, R. Brousse
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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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Metallogenesis in relation to mantle heterogeneity

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 1980
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. The extent to which chemical heterogeneities in the mantle may have helped to determine such patterns of variation can ...
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