Petit-spot as definitive evidence for partial melting in the asthenosphere caused by CO<sub>2</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 28148927.
- Also identified by DOI 10.1038/ncomms14302 and PMC identifier 5296659.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The deep carbon cycle plays an important role on the chemical differentiation and physical properties of the Earth's mantle. Especially in the asthenosphere, seismic low-velocity and high electrical conductivity due to carbon dioxide (CO<sub>2</sub>)-induced partial melting are expected but not directly observed. Here we discuss the experimental results relevant to the genesis of primitive CO<sub>2</sub>-rich alkali magma forming petit-spot volcanoes at the deformation front of the outer rise of the northwestern Pacific plate. The results suggest that primitive melt last equilibrated with depleted peridotite at 1.8-2.1 GPa and 1,280-1,290 °C. Although the equilibration pressure corresponds to the pressure of the lower lithosphere, by considering an equilibration temperature higher than the solidus in the volatile-peridotite system along with the temperature of the lower lithosphere, we conclude that CO<sub>2</sub>-rich silicate melt is always produced in the asthenosphere. The melt subsequently ascends into and equilibrates with the lower lithosphere before eruption.