Subduction zones play a fundamental role in the deep water cycle making the Earth unique among other terrestrial planets. During subduction dehydration of hydrous minerals produces a fluid phase. A part of this fluid phase will be recycled water back to the Earth’s surface through hydrothermal aqueous fluids or through hydrous arc magmas, whereas another part of the water will be transported to the deep mantle by Nominally Anhydrous Minerals (NAMs) such as olivine, pyroxene and garnet. The partitioning of water between these two processes is crucial for the understanding the deep water cycle which has profound implications for the rheology of the upper and lower mantle. However, the transition from hydrous minerals to NAMs has been very little explored and only rough estimations are available.
The main thrusts of the project are (1) to undertake a series of novel experiments with hydrous mantle compositions using high-pressure experimental facilities to constrain the actual water contents that are recycled in NAMs in shallow subduction zones (1.5-5.5 GPa and <900ºC) and (2) compare the products with natural assemblages that underwent extensive dehydration during subduction (through antigorite and chlorite high-pressure breakdown reactions). Additionally this project will investigate the link between mechanisms of deformation and mechanism of hydrogen incorporation in NAMs and how they may affect the rheology of the incoming slab and uppermost mantle.
This project will be arrange by assuming two years at Australian National University (outgoing host institution), during which experiments will be performed and natural rocks will be analyzed for trace elements and water contents, and one year at Géosciences Montpellier (Return host institution), where microstructural investigations of natural samples will be carried out.
Fields of science
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