Abstract
Abstract Hydrous minerals in subducted crust can transport large amounts of water into Earth's deep mantle. Our laboratory experiments revealed the surprising pressure-induced chemistry that, when water meets iron at the core–mantle boundary, they react to form an interlayer with an extremely oxygen-rich form of iron, iron dioxide, together with iron hydride. Hydrogen in the layer will escape upon further heating and rise to the crust, sustaining the water cycle. With water supplied by the subducting slabs meeting the nearly inexhaustible iron source in the core, an oxygen-rich layer would cumulate and thicken, leading to major global consequences in our planet. The seismic signature of the D″ layer may echo the chemical complexity of this layer. Over the course of geological time, the enormous oxygen reservoir accumulating between the mantle and core may have eventually reached a critical eruption point. Very large-scale oxygen eruptions could possibly cause major activities in the mantle convection and leave evidence such as the rifting of supercontinents and the Great Oxidation Event.
Highlights
Among all of the global boundaries on the planet, the interface between Earth’s core and mantle stands out as having the greatest contrast in chemical composition and physical properties [1]
They suggested that goethite sandwiched in layers of SiO2 would transform into the pyrite-type high-pressure phase without loss of any hydrogen at conditions below 2400 K at 111 GPa and 1500 K at 129 GPa
Searching for a possible source of much greater magnitude, we found that, if hydrous minerals go down with slabs to reach the subsolidus side of core–mantle boundary (CMB) [6,7,8,9,10], the nearly inexhaustible iron reservoir in the core will react with the water released from the hydrous minerals to generate an enormous quantity of the Py-phase in oxygenrich patches (ORP) above the CMB
Summary
Among all of the global boundaries on the planet, the interface between Earth’s core and mantle stands out as having the greatest contrast in chemical composition and physical properties [1]. While we worked on the revision of this manuscript, Nishi et al confirmed the formation of the pyrite-type phase of FeOOH [5] They suggested that goethite sandwiched in layers of SiO2 would transform into the pyrite-type high-pressure phase without loss of any hydrogen at conditions below 2400 K at 111 GPa and 1500 K at 129 GPa. They suggested that goethite sandwiched in layers of SiO2 would transform into the pyrite-type high-pressure phase without loss of any hydrogen at conditions below 2400 K at 111 GPa and 1500 K at 129 GPa These studies exemplify the drastic changes of chemistry occurring on the most basic elements under the P-T conditions of the deep lower mantle. We conducted additional experiments in the key Fe-OH ternary system, presented the mechanism for generating widespread oxygen-rich patches consisting of the Py-phase and other iron oxides and hydrides at the base of the mantle, and proposed far-reaching geophysical, geochemical and geodynamic consequences based on the new observations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
