The fate of subducted basaltic crust in the Earth's lower mantle

Article Abstract:

The oceanic lithosphere may not subduct uniformly and it has been suggested that subducted basaltic crust could be buoyant at the mantle's 660-km discontinuity and could be gravitationally trapped, forming a garnetite layer. Phase relations and melting temperatures for natural mid-ocean ridge basalt are reported at pressures up to 64GPa. The former basaltic crust did not remain buoyant when it transformed to a perovskitite lithology, and it is predicted that such a basaltic crust would sink gravitationally into the deep mantle.

Observations, Basalt, Mantle (Geology), Subduction zones (Geology), Subduction zones

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Iron partitioning in a pyrolite mantle and the nature of the 410-km seismic discontinuity

Article Abstract:

It has been established that the iron content in olivine alters substantially with rising pressure. This is the result of the emergence of quite iron-rich majorite phase at pressures of between 6 GPa and 16 GPa. The density of olivine becomes much higher with rising iron content, and the seismic velocities of iron-poor olivine should therefore be significantly higher than those of iron-rich olivine. This variation in iron content indicates that the component mineral systems in pyrolite cannot be regarded as separate.

Crust (Geology)

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Stability of magnesite and its high-pressure form in the lowermost mantle

Article Abstract:

In situ X-ray diffraction study of the stability of magnesite (MgCo3) is depicted. The studies indicate that magnesite transforms to an unknown form at pressures above ~115 GPa and temperatures of 2100-2200 K without any dissociation, which may be major hosts for carbon throughout most parts of the Earth's lower mantle.

United States, Science & research, Clay and related minerals, not elsewhere classified, Clay and Ceramic and Refractory Minerals Mining, Magnesite, Research, Chemical reactions

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