Decrease of hydrogen incorporation in forsterite from CO2-H2O-rich kimberlitic liquid
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Virginie Baptiste
,
Shantanu Keshav
Abstract
To test if hydrogen incorporation by ionic diffusion can occur between a volatile-rich kimberlitic liquid and forsterite, results of high-pressure and high-temperature experiments using a piston-cylinder apparatus at 1200-1300 °C and 1 GPa for durations of 1 min, 5 h, and 23 h, are reported here. Kimberlitic liquid in the system CaO-MgO-Al2O3-SiO2-CO2-H2O and synthetic forsterite single crystals were chosen as a first simplification of the complex natural kimberlite composition. Unpolarized Fourier transform infrared spectroscopy was used to quantify the concentrations of OH in the crystallographically oriented forsterite. Scanning electron microscopy, electron backscattered diffraction, electron microprobe analyses, and transmission electron microscopy were performed to identify the run products. After 5 and 23 h, a forsterite overgrowth crystallized with the same orientation as the initial forsterite single crystal. The kimberlitic liquid has crystallized as micrometer-scale euhedral forsterite neocrystals with random crystallographic orientations, as well as a nanoscale aluminous phase and a calcic phase. Despite theoretical water-saturation of the system and long duration, none of the initial forsterite single crystals display signs of hydration such as hydrogen diffusion profile from the border toward the center of the crystal. Most likely, the presence of CO2 in the system has lowered the H2O fugacity to such an extent that there is no significant hydration of the starting forsterite single crystal or its overgrowth. Also, the presence of CO2 enhances rapid forsterite crystal growth. Forsterite growth rate is around 2 × 108 mm3/h at 1250 °C. These experimental results suggest a deep mantle origin of the high OH content found in natural mantle-derived xenoliths transported in kimberlites, as reported from the Kaapvaal craton. In agreement with previous studies, it also points out to the fact that significant hydration must take place in a CO2-poor environment.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Data, ideas, and the nature of scientific progress
- Beyond the equilibrium paradigm: How consideration of kinetics enhances metamorphic interpretation
- Magmatic volatiles (H, C, N, F, S, Cl) in the lunar mantle, crust, and regolith: Abundances, distributions, processes, and reservoirs
- The mafic component of the lunar crust: Constraints on the crustal abundance of mantle and intrusive rock, and the mineralogy of lunar anorthosites
- Degassing pathways of Cl-, F-, H-, and S-bearing magmas near the lunar surface: Implications for the composition and Cl isotopic values of lunar apatite
- Uranium scavenging during mineral replacement reactions
- New structure of high-pressure body-centered orthorhombic Fe2SiO4
- Spectroscopic study of ordering in non-stoichiometric magnesium aluminate spinel
- High-pressure behavior of cuprospinel CuFe2O4: Influence of the Jahn-Teller effect on the spinel structure
- Field and model constraints on silicic melt segregation by compaction/hindered settling: The role of water and its effect on latent heat release
- Formation of rhyolite at the Okataina Volcanic Complex, New Zealand: New insights from analysis of quartz clusters in plutonic lithics
- Experimental investigation of F, Cl, and OH partitioning between apatite and Fe-rich basaltic melt at 1.0–1.2 GPa and 950–1000 °C
- Synthesis, characterization, and thermodynamics of arsenates forming in the Ca-Fe(III)-As(V)-NO3 system: Implications for the stability of Ca-Fe arsenates
- High-pressure phases of cordierite from single-crystal X-ray diffraction to 15 GPa
- Planar microstructures in zircon from paleo-seismic zones
- Ultra-deep subduction of Yematan eclogite in the North Qaidam UHP belt, NW China: Evidence from phengite exsolution in omphacite
- Elastic wave velocity anomalies of anorthite in a subducting plate: In situ experiments
- Current limitations of molecular dynamic simulations as probes of thermo-physical behavior of silicate melts
- Three-component mixed-layer illite/smectite/kaolinite (I/S/K) minerals in hydromorphic soils, south China
- Melting curve of NaCl to 20 GPa from electrical measurements of capacitive current
- Grain size measurement from two-dimensional micro-X-ray diffraction: Laboratory application of a radial integration technique
- Decrease of hydrogen incorporation in forsterite from CO2-H2O-rich kimberlitic liquid
- Provenance determination of sapphires and rubies using laser-induced breakdown spectroscopy and multivariate analysis
- Structural insights and elasticity of single-crystal antigorite from high-pressure Raman and Brillouin spectroscopy measured in the (010) plane
- Magnetic anisotropy in natural amphibole crystals
- Resolving oxygen isotopic disturbance in zircon: A case study from the low δ18O Scourie dikes, NW Scotland
- Accurate determination of Fe3+/ΣFe of andesitic glass by Mössbauer spectroscopy
- Recoil-free fractions of iron in aluminous bridgmanite from temperature-dependent Mössbauer spectra
- Chemical interactions between a sedimentary diapir and surrounding magma: Evidence from the Phepane Dome and Bushveld Complex, South Africa
- The crystal structures of Mg2Fe2C4O13, with tetrahedrally coordinated carbon, and Fe13O19, synthesized at deep mantle conditions
- New Mineral Names
- Book Review: Geodynamics, Third edition.
