Seismic evidence for silicate melt atop the 410-km mantle discontinuity
Nature
By: Justin Revenaugh and S.A. Sipkin
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Abstract
LABORATORY results demonstrating that basic to ultrabasic melts become denser than olivine-rich mantle at pressures above 6 GPa (refs 1-3) have important implications for basalt petrogenesis, mantle differentiation and the storage of volatiles deep in the Earth. A density cross-over between melt and solid in the extensively molten Archaean mantle has been inferred from komatiitic volcanism and major-element mass balances, but present-day evidence of dense melt below the seismic low-velocity zone is lacking. Here we present mantle shear-wave impedance profiles obtained from multiple-ScS reverberation mapping for corridors connecting western Pacific subduction zone earthquakes with digital seismograph stations in eastern China, imaging a ~5.8% impedance decrease roughly 330 km beneath the Sea of Japan, Yellow Sea and easternmost Asia. We propose that this represents the upper surface of a layer of negatively buoyant melt lying on top of the olivine ??? ??- phase transition (the 410-km seismic discontinuity). Volatile-rich fluids expelled from the partial melt zone as it freezes may migrate upwards, acting as metasomatic agents and perhaps as the deep 'proto-source' of kimberlites. The remaining, dense, crystalline fraction would then concentrate above 410 km, producing a garnet-rich layer that may flush into the transition zone.
Suggested Citation
Revenaugh, J., Sipkin, S., 1994, Seismic evidence for silicate melt atop the 410-km mantle discontinuity: Nature, v. 369, no. 6480, p. 474-476, https://doi.org/10.1038/369474a0.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Seismic evidence for silicate melt atop the 410-km mantle discontinuity |
| Series title | Nature |
| DOI | 10.1038/369474a0 |
| Volume | 369 |
| Issue | 6480 |
| Year Published | 1994 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Nature |
| First page | 474 |
| Last page | 476 |