Amphibole stability, melting, and deep water transport in subduction zones

• Applicant: Professor Dr. Hans Keppler
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559650198

Subduction zones are the main location of seismic and volcanic hazards on Earth, but at the same time also the source of many critical metals. In deep geologic time, subducted slabs transport water back into the mantle, which influences the evolution of global sea level. Nevertheless, many important aspects of this system are not fully understood. In this project, high pressure experiments will be used to better understand the location of the volcanic front and the deep recycling of water at convergent plate margins. Amphibole is one of the main hydrous minerals transporting water into the mantle. There are indications suggesting that the stability range of amphibole was underestimated in previous studies. The maximum pressure and temperature stability field of amphibole will therefore be re-determined by piston cylinder experiments with improved experimental design. The results will be used to test the hypothesis that amphibole dehydration controls the location of the volcanic front in subduction zones. After amphibole dehydration, the nominally anhydrous minerals omphacite and garnet may transport water deeper into the mantle. In order to determine the efficiency of this transport mechanism, the water solubility in omphacite and garnet inside an eclogitic paragenesis will be systematically studied and the implications of this transport mechanism for Earth´s deep water cycle will be explored.

• DFG Programme: Research Grants