Structure and properties of forsterite-MgSiO3 liquid interface: molecular dynamics study
Tóm tắt
The mechanical properties of partially molten rock, such as their permeabilities and viscosities, are important properties in geological processes. We performed molecular dynamics simulations in terms of structures and diffusivities in forsterite-MgSiO3 liquid interfaces to obtain the nanoscale dynamic properties and structure of the interface. The characteristic structure of the forsterite-MgSiO3 liquid interfaces was observed in the simulations. In the layered structure of the altered surfaces, Si-rich and Mg-rich layers exist alternately in the vicinity of the crystal-liquid interfaces. The layered structure might be formed by the strength difference between Si-O covalent bonds and Mg-O ionic bonds. The difference in the layered structure, indicated by the thickness of the MgSiO3 liquid film, might be caused by the difference in degrees of freedom of the configuration in the liquid film. The two-dimensional diffusivity of oxygen atoms parallel to the interface is controlled by two factors. One factor is the thickness of the liquid film, which decreases oxygen diffusivity with decreasing film thickness. The other is the composition of the sliced layer, where oxygen diffusivity increases with increasing Mg/Si ratio. The effect of the crystal-liquid interface found in this study is negligible in texturally equilibrated rocks. However, the interface can affect the melt flow in deformed samples because a grain boundary melt film with a thickness of several nanometers exists stably in deformed partially molten rock.
Tài liệu tham khảo
Adjaoud O, Steinle-Neumann G, Jahn S: Transport properties of Mg 2 SiO 4 liquid at high pressure: physical state of magma ocean. Earth Planet Sci Lett 2011, 312: 463–470. doi:10.1016/j.epsl.2011.10.025 doi:10.1016/j.epsl.2011.10.025 10.1016/j.epsl.2011.10.025
Angel RJ, Hugh-Jones DA: Equations of state and thermodynamic properties of enstatite pyroxenes. J Geophys Res 1994, 99: 19777–19783. doi:10.1029/94JB01750
Bockris JO'M, Mackenzie JD, Kitchener JA: Viscous flow in silica and binary liquid silicates. Trans Faraday Soc 1955, 51: 1734–1748. doi:10.1039/TF9555101734
De Kloe R, Drury MR, van Roermund HLM: Evidence for stable grain boundary melt films in experimentally deformed olivine-orthopyroxene rocks. Phys Chem Min 2000, 27: 480–494. doi:10.1007/s002690000090
De Koker NP, Stixrude L, Karki B: Thermodynamics, structure, dynamics, and freezing of Mg 2 SiO 4 liquid at high pressure. Geochim Cosmochim Acta 2009, 72: 1427–1441. doi:10.1016/j.gca.2007.12.019 doi:10.1016/j.gca.2007.12.019
Duffy TS, Zha C, Downs RT, Mao H, Hemley RJ: Elasticity of forsterite to 16 GPa and the composition of the upper mantle. Nature 1995, 378: 170–173. 10.1038/378170a0
Dunn T: Oxygen diffusion in three silicate melts along the join diopside-anorthite. Geochim Cosmochim Acta 1982, 46: 2293–2299. doi:10.1016/0016–7037(82)90202–2
Faul UH, Jackson I: The seismological signature of temperature and grain size variations in the upper mantle. Earth Planet Sci Lett 2005, 234: 119–134. doi:10.1016/j.epsl.2005.02.008
Fujino K, Sasaki S, Takeuchi Y, Sadanaga R: X-ray determination of electron distributions in forsterite, fayalite and tephroite. Acta Crystallogr B 1981, 37: 513–518. doi:10.1107/S0567740881003506
Gurmani SF, Jahn S, Brasse H, Schilling FR: Atomic scale view on partially molten rocks: molecular dynamics simulations of melt-wetted olivine grain boundaries. J Geophys Res 2011, 116: V12209. doi:10.1029/2011JB008519
Hiraga T, Anderson LM, Zimmerman ME, Mei S, Kohlstedt DL: Structure and chemistry of grain boundaries in deformed, olivine + basalt and partially molten lherzolite aggregates: evidence of melt-free grain boundaries. Contrib Mineral Petrol 2002, 144: 163–175. doi:10.1007/s00410–002–0394–1
Horbach J, Kob W, Binder K, Angell CA: Finite size effects in simulations of glass dynamics. Phys Rev E 1996, 54: R5897-R5900. doi;10.1103/PhysRevE.54.R5897 doi;10.1103/PhysRevE.54.R5897 10.1103/PhysRevE.54.R5897
Ichikawa Y, Kawamura K, Nakano M, Kitayama K, Seiki T, Theramast N: Seepage and consolidation of bentonite saturated with pure- or salt-water by the method of unified molecular dynamics and homogenization analysis. Eng Geol 2001, 60: 127–138. doi:10.1016/S0013–7952(00)00095–8
Jung I, Decterov SA, Pelton AD: Critical thermodynamic evaluation and optimization of the FeO-Fe 2 O 3 -MgO-SiO 2 system. Metall Mater Trans B 2004, 35: 877–889. doi:10.1007/s11663–004–0082–9 doi:10.1007/s11663-004-0082-9 10.1007/s11663-004-0082-9
Keller H, Schwerdtfeger K: Tracer diffusivity of Si31 in CaO-SiO 2 melts at 1600 °C. Metall Trans B 1979, 10: 551–554. 10.1007/BF02662556
Keller H, Schwerdtfeger K, Petri H, Hölzle R, Hennesen K: Tracer diffusivity of O18 in CaO-SiO 2 melts at 1600 °C. Metall Trans B 1982, 13: 237–240. 10.1007/BF02664580
Lacks DJ, Rear DB, van Orman JA: Molecular dynamics investigation of viscosity, chemical diffusivities and partial molar volumes of liquids along the MgO-SiO 2 join as functions of pressure. Geochim Cosmochim Acta 2007, 71: 1312–1323. doi:10.1016/j.gca.2006.11.030 doi:10.1016/j.gca.2006.11.030 10.1016/j.gca.2006.11.030
McKenzie D: Some remarks on the movement of small melt fractions in the mantle. Earth Planet Sci Lett 1989, 95: 53–72. doi:10.1016/0012–821X(89)90167–2
Momma K, Izumi F: VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data. J Appl Crystallogr 2011, 44: 1272–1276. doi:10.1107/S0021889811038970
Morimoto N, Koto K: The crystal structure of orthoenstatite. Z Kristallogr – Cryst Mater 1969, 129: 65–83.
Noritake F, Kawamura K, Yoshino T, Takahashi E: Molecular dynamics simulation and electrical conductivity measurement of Na 2 O▪3SiO 2 melt under high pressure; relationship between its structure and properties. J Non-Cryst Solids 2012, 358: 3109–3118. doi:10.1016/j.noncrysol.2012.08.027 doi:10.1016/j.noncrysol.2012.08.027 10.1016/j.jnoncrysol.2012.08.027
Oishi Y, Terai R, Ueda H: Oxygen diffusion in liquid silicates and relation to their viscosity. In Mass transport phenomena in ceramics. Material science research, vol 9. Edited by: Cooper A. New York: Springer; 1975:297–310.
Rubie DC, Ross CR, Carroll MR, Elphick SC: Oxygen self-diffusion in Na 2 Si 4 O 9 liquid up to 10 GPa and estimation of high-pressure melt viscosities. Am Mineral 1993, 78: 574–582.
Sakuma H, Kawamura K: Structure and dynamics of water on muscovite mica surfaces. Geochim Cosmochim Acta 2009, 73: 4100–4110. doi:10.1016/j.gca.2009.05.029
Sakuma H, Tsuchiya T, Kawamura K, Otsuki K: Large self-diffusion of water on brucite surface by ab initio potential energy surface and molecular dynamics simulations. Surf Sci 2003, 536: L396-L402. doi:10.1016/S0039–6028(03)00577–6
Shimizu N, Kushiro I: Diffusivity of oxygen in jadeite and diopside melts at high pressures. Geochim Cosmochim Acta 1984, 48: 1295–1303. doi:10.1016/0016–7037(84)90063–2
Von Bargen N, Waff HS: Permiabilities, interfacial areas and curvatures of partially molten systems: results of numerical computations of equilibrium microstructures. J Geophys Res 1986, 91: 9261–9276. doi:10.1029/JB091iB09p09261
Waff HS, Bulau JR: Equilibrium fluid distribution in an ultramafic partial melt under hydrostatic stress conditions. J Geophys Res 1979, 84: 6109–6114. doi:10.1029/JB084iB11p06109
Zhu W, Hirth G: A network model for permeability in partially molten rocks. Earth Planet Sci Lett 2003, 212: 407–416. doi:10.1016/S0012–821X(03)00264–4