Locally layered convection inferred from dynamic models of the Earth's mantle

Article Abstract:

The topography of the surface mantle flow obtained using an empirical method to account for the 660-km boundary topography in a model using seismically derived density heterogeneities is comparable to that obtained by observations. Traditional modeling methods using density anomalies from seismic tomography result in significant underestimations because of the failure to account for 660-km boundary deflections. The results of this study show that the 660-km boundary topography affects the calculation of the mantle circulation and induces local layering in the convection flow. A viscous flow model where the lithospheric plates are at the surface has been used for the compressible mantle.

Methods, Earth, Mantle (Geology), Relief models

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Nitrogen content of the mantle inferred from N2-Ar correlation in oceanic basalts

Article Abstract:

The ratio of N2 to 40Ar in the mantle is stable and correlates well with the current atmospheric N2/40AR ratio. The N2/36Ar in the mantle is, however, twice that found in the atmosphere. A static mass spectrometry method for the simultaneous analysis of carbon, nitrogen, helium and argon that is trapped in vesicles of mid-ocean-ridge basalt glasses has been developed. These correlations allow for estimates of the mantle's nitrogen content and its early interactions with the atmosphere.

Research, Usage, Observations, Mid-ocean ridges, Mass spectrometry, Atmosphere, Noble gases, Gases, Rare

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