Temperature-induced amorphization in CaCO<sub>3</sub> at high pressure and implications for recycled CaCO<sub>3</sub> in subduction zones.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31036817.
- Also identified by DOI 10.1038/s41467-019-09742-5 and PMC identifier 6488655.
- 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
Calcium carbonate (CaCO<sub>3</sub>) significantly affects the properties of upper mantle and plays a key role in deep carbon recycling. However, its phase relations above 3 GPa and 1000 K are controversial. Here we report a reversible temperature-induced aragonite-amorphization transition in CaCO<sub>3</sub> at 3.9-7.5 GPa and temperature above 1000 K. Amorphous CaCO<sub>3</sub> shares a similar structure as liquid CaCO<sub>3</sub> but with much larger C-O and Ca-Ca bond lengths, indicating a lower density and a mechanism of lattice collapse for the temperature-induced amorphous phase. The less dense amorphous phase compared with the liquid provides an explanation for the observed CaCO<sub>3</sub> melting curve overturn at about 6 GPa. Amorphous CaCO<sub>3</sub> is stable at subduction zone conditions and could aid the recycling of carbon to the surface.