Sessions of interest at the Goldschmidt 2016

Convenors: Jun-Ichi Kimura, Junichi Nakajima, Peter van Keken, Georg F. Zellmer, Tatsuhiko Kawamoto

Keynote: Shuichi Kodaira (JAMSTEC)

Subduction zones usually consist of a descending oceanic plate slab, a wedge mantle, and an overriding arc crust. Various geodynamic phenomena occur, such as deep and shallow seismicities, intensive deformation, high heat flux, geothermal fluid flow, and magmatic activities. These phenomena are due to the particular structure of subduction zones, such as an inverted geotherm, and large amounts of water in the system. The water descents with the subducted slab and is released at sub-arc depths. In addition, fluids and magmas well up and react with the mantle and the crust. These liquid fluxes and the associated heat flux affect to the dynamics of the solid arc system. This session aims to combine cutting-edge research results on the geophysical, geochemical, and geodynamic processes in a subduction zone. Furthermore, the overall structure of a subduction zone and operating processes will be discussed. The discussions will focus on geophysical and geochemical constraints, including (1) seismic activities in the subducting oceanic plate slab with relevance to hydration, dehydration, and melting of the slab, (2) dynamic processes in the wedge mantle related to convection of solids and liquids with reference to the conditions of fluids and magmas, and (3) seismic activities and deformations in the crust relevant to thermal structure, geofluids, and magma storage. We invite contributions that model these links or that can provide some insights to the various phenomena in subduction zones.

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07b: Geochemical Recycling in Subduction Zones: What Goes in, What Comes Out, and What Happens in between

Conveners: Thomas Pettke, Susanne Skora, Tatsuki Tsujimori, Sarah Penniston-Dorland, Matthias Konrad-Schmolke

Keynote speaker: Katy Evans (Curtin University)

This session aims at attracting geochemists and petrologists contributing to our better understanding of geochemical cycling and mass transfer of elements and isotopes in the subduction factory. Such processes are often at the onset of the global-scale dynamics that formed and have modified Earth’s geochemical reservoirs through time. Recent experimental, (micro)analytical and field-based research advances now allow us to gain unprecedented insights into how geochemical cycling has operated to form and continuously modify Earth’s geochemical reservoirs. We invite contributions that focus on what enters subduction zones, how this material evolves with progressive subduction and what is eventually recycled to the continental crust via arc magmatism or back to the convecting mantle. Studies dealing with element abundance and isotope ratio systematics, aqueous and carbonic fluid chemistries, halogens, fluid – solid phase petrology, thermal conditions, modelling, and field-based or experimental investigations are equally appreciated. We particularly encourage contributions that present provocative ideas and concepts, and unconventional approaches, to foster inspiring scientific exchange on the physical and chemical processes operating down to subarc depth.

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04f: Mantle melting in Earth and planetary interiors

Conveners: Sarah Lambart (UC Davis), Ananya Mallik (Bayerisches Geoinstitut), Sylvain Petitgirard (Bayerisches Geoinstitut)

Mantle melting processes are of crucial importance for the differentiation of the Earth and planetary bodies. Melts affect physical properties of planetary mantles such as the rheology, conductivity and density along with governing the formation and redistribution of geochemical and volatile reservoirs. This session aims at understanding physical and chemical properties of melts in shallow to deep interiors of terrestrial and planetary bodies, from early accretion to present day dynamics. We especially encourage experimental studies on the melting of planetary interiors using large volume press, diamond anvil cell, and dynamic shock compression techniques. We invite submissions exploring melt chemistry, extraction of melt, effect of volatiles on the process of melting, physical properties of melt such as density, viscosity, structure and their effect on local to large-scale physical and chemical properties of the Earth and planetary bodies.