High-P/T experimental studies and water in the silicate mantle

Water(or H) in the silicate mantle is a key element in influencing Earth's climate, habitability, geochemical evolution, geophysical properties and geodynamical processes, and has received increasing attention in the past decades. Experimental work under simulated high-pressure and high-temperature conditions is a powerful tool in characterizing the species, distribution, storage capacity and various physicochemical impacts of water in the mantle. In recent years, significant approaches have been acquired about some key physical, chemical and dynamical properties of water in the mantle and their various impacts, as a result of extensive studies by high-pressure and temperature experiments, and our knowledge of Earth's water cycle, especially the deep water cycle, on both temporal and spatial scales has been greatly enhanced. In this paper, a brief review based mainly on experimental studies is presented concerning the current understanding and some recent approaches of water in the silicate mantle, such as the possible origin, amount, storage and the effect on mantle properties.

Experimental constraints on trace element partitioning between coesite and hydrous silicate melt at 5 GPa and 1500-1750℃

Trace element partitioning between coesite and hydrous silicate melt has been investigated at 5 GPa and 1500-1750℃.High-P experiments successfully produced large coesite crystals in equilibrium with large silicate melt pools(plus kyanite and corundum crystals in some cases).Scanning electron microscopy and micro-Raman spectroscopy were employed to characterize the phases and the textures.Wavelength-dispersive electron microprobe analyses were performed to quantify conventional major elements,and laser ablation-inductively coupled plasma-mass spectrometry analyses were successfully conducted to quantify trace elements.Eventually,high-P partition coefficients were obtained for 33 elements.In general coesite is a very pure phase.With a few possible exceptions like Sc,Ti,and V,nearly all other trace elements are incompatible in coesite.Moreover,the partitioning behaviors of nearly all trace elements except some 4+cations cannot be readily described by the lattice strain model,presumably implying a minor role for the cation size in the trace-element partitioning.Combining our experimental results with the results in the literature,some T and P effects on the element partitioning behavior have been observed:T seemingly has different effects on different trace elements,but P might negatively correlate with the partition coefficients in all cases.Due to its large modal fraction in some subducted materials such as the continental crustal material,coesite might play an important role in the distributions of some trace elements,Ti for example.