Water in Subduction Zones

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EAR-0309292 PeslierWater has a strong influence on the chemical and physical properties of silicate minerals, fluids, and melts in the lithosphere. Water released from the mantle via melt transport to the crust, or degassing, may be recycled back into the mantle in subduction zones. Subduction processes likely add significant quantities of water back into the mantle. The reactions occurring during the dehydration of a down-going slab, the quantity of water being kept by the slab and that expelled to the overlying mantle wedge, how water is stored in these various components, and in what form it can be released, are therefore important factors in understanding the water budget of the mantle. This project proposes to estimate the water content of the down-going slab and that of the overlying mantle wedge, in order to shed light on the water transport budget at subduction zones. This study focuses on the primary phases of the mantle, olivine, pyroxene and garnet. These nominally anhydrous minerals may represent an important site for storing water (or more exactly hydrogen) in subducted slabs and in the mantle above slabs at depths where hydrous minerals may not be stable. The samples will be prepared for analysis at the University of Houston. The analyses of water will be performed by Fourier transform infrared spectrometry (FTIR) at NASA Johnson Space Center in Houston, Texas. Fe3+/Fe ratio measurements from which oxygen fugacities will be calculated will be performed with Mossbauer equipment at the Bavarian Research Institute at Bayreuth, Germany. The first broader impact of this project is that Anne Peslier will be able to work in a collaborative setting with local and international partners. This project will also provide infrastructure support for the laboratory facilities at the University of Houston. Finally this grant will help support an early-career female PI to maintain active research and as such will help increase the representation of women in the science enterprise.