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

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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.