Ammonium in high-pressure minerals - a sink for hydrogen and nitrogen in the Earth´s mantle

• Applicant: Professor Dr. Wilhelm Heinrich
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2006 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 24817682

At conditions of the Earth¿s crust the ammonium ion NH4 + replaces potassium to small but significant amounts in many K-bearing minerals. It is controversially debated if a substantial amount of nitrogen is recycled into the deeper mantle during subduction processes. The crucial point of the debate is that very little is known about the geochemical behaviour of nitrogen in mantle rocks. Incorporation of ammonium into high-pressure K-bearing phases possibly provides the means for nitrogen recycling into Earth¿s mantle. Moreover, this would also provide a formidable mechanism for hydrogen transport into the deeper mantle. It appears that the potential of ammonium for large-scale recycling of hydrogen and nitrogen is unexplored. High-pressure experiments using multi anvil equipment will test the hypothesis that high-pressure K-bearing crystal structures are able to accommodate NH4, and determine up to which extent this might be possible.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1236: Synthesis, "In Situ" Characterisation and Quantum Mechanical Modelling of Earth Materials, Oxides, Carbides and Nitrides at Extremely High Pressures and Temperatures