Jacket transition zone

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The mantle transition zone (MTZ) is characterized in the seismological IASP91 model by increases in speed

The mantle transition zone is geophysically defined by significant jumps in speed of seismic waves and lies on average between 410 and 660 km depth. The transition zone is characterized by an increase in density from 3.42 g / cm³ in the lowest upper mantle to 3.9 g / cm³ in the uppermost lower mantle .

Phase transitions

The changes in wave speeds can today be traced back to essentially three phase transitions of certain minerals (the depth data are global mean values):

Significance for geodynamics

Due to the phase transitions and the denser rocks that occur here, the mantle transition zone initially represents an obstacle to further subduction and thus full mantle convection . According to more recent findings, however, a submergence of the plate remains to the core-mantle boundary seems very likely.

According to a study, there could also be partial melting and / or drainage of the former oceanic crust in the transition zone , which could result in mantle diapirs . Inclusions of majorite in diamonds prove that rocks originate at least from the mantle transition zone.


Individual evidence

  1. http://www.nature.com/ngeo/journal/v6/n5/pdf/ngeo1772.pdf
  2. M. Okrusch (2011): Mineralogy - An introduction to special mineralogy, petrology and deposit science. 8th edition p. 490f