Potassium upper mantle composition

Konzett J. and Fei Y. (2000) Transport and storage of potassium in the Earth s upper mantle and transition zone an experimental study to 23 GPa in simplified and natural bulk compositions. J. Petrol. 41, 583-603. 

The composition of the upper mantle clearly does not provide information on the degassing history of the mantle, but rather reflects the small fluxes into this reservoir from the deep mantle, from production within the upper mantle, and possibly from subduction. The transfer of "Xr from the cmst throughout much of Earth history has been dictated by the degassing of the cmst, where the potassium has been stored. 

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