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Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

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Compositional stratification in the deep mantle

Kellogg¹, Hager, van der Hilst RD

¹Department of Geology, University of California, Davis, CA 95616, USA. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 01239, USA.

Science (New York, N.Y.)

|March 19, 1999

Summary

A distinct layer in Earth's lower mantle may explain seismic observations and geochemical signatures. This dense, stable layer influences mantle dynamics and heat flow, reconciling discrepancies in Earth's thermal budget.

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Area of Science:

Geophysics
Geochemistry
Mineral Physics

Background:

Seismic observations reveal complexities in Earth's lower mantle.
Isotopic signatures in basalts suggest deep mantle reservoirs.
Discrepancies exist between observed heat flux and heat production models.

Purpose of the Study:

To explain seismological and geochemical observations in Earth's lower mantle.
To reconcile discrepancies in the mid-ocean ridge basalt source region's heat budget.
To investigate the stability and characteristics of a deep mantle compositional boundary.

Main Methods:

Analysis of seismological data from Earth's lower mantle.
Modeling of thermochemical convection using numerical simulations.
Investigation of isotopic signatures in mid-ocean ridge basalts and oceanic island basalts.

Main Results:

A compositional boundary at ~1600 km depth is proposed.
Numerical models confirm the dynamic stability of a denser deep mantle layer.
This layer's properties reconcile heat flux and heat production discrepancies.

Conclusions:

The deep mantle boundary explains seismic and geochemical data.
Thermochemical convection models support a stable, denser layer.
This layer influences mantle dynamics, heat flow, and basaltic signatures.