The responses of the four main substitution mechanisms of H in olivine to H2O activity at 1050 °C and 3 GPa
Tóm tắt
The water solubility in olivine
$$ \left({C}_{{\mathrm{H}}_2\mathrm{O}}\right) $$
has been investigated at 1050 °C and 3 GPa as a function of water activity
$$ \left({a}_{{\mathrm{H}}_2\mathrm{O}}\right) $$
at subsolidus conditions in the piston-cylinder apparatus, with
$$ {a}_{{\mathrm{H}}_2\mathrm{O}} $$
varied using H2O–NaCl fluids. Four sets of experiments were conducted to constrain the effect of
$$ {a}_{{\mathrm{H}}_2\mathrm{O}} $$
on the four main substitution mechanisms. The experiments were designed to grow olivine in situ and thus achieve global equilibrium (G-type), as opposed to hydroxylating olivine with a pre-existing point-defect structure and impurity content (M-type). Olivine grains from the experiments were analysed with polarised and unpolarised FTIR spectroscopy, and where necessary, the spectra have been deconvoluted to quantify the contribution of each substitution mechanism. Olivine buffered with magnesiowüstite produced absorbance bands at high wavenumbers ranging from 3566 to 3612 cm−1. About 50% of the total absorbance was found parallel to the a-axis, 30% parallel to the b-axis and 20% parallel to the c-axis. The total absorbance and hence water concentration in olivine follows the relationship of
$$ {C}_{{\mathrm{H}}_2\mathrm{O}}\propto {a_{{\mathrm{H}}_2\mathrm{O}}}^2 $$
, indicating that the investigated defect must involve four H atoms substituting for one Si atom (labelled as [Si]). Forsterite buffered with enstatite produced an absorbance band exclusively aligned parallel the c-axis at 3160 cm−1. The band position, polarisation and observed
$$ {C}_{{\mathrm{H}}_2\mathrm{O}}\propto {a}_{{\mathrm{H}}_2\mathrm{O}} $$
are consistent with two H substituting for one Mg (labelled as [Mg]). Ti-doped, enstatite-buffered olivine displays absorption bands, and polarisation typical of Ti-clinohumite point defects where two H on the Si-site are charge-balanced by one Ti on a Mg-site (labelled as [Ti]). This is further supported by
$$ {C}_{{\mathrm{H}}_2\mathrm{O}}\propto {a}_{{\mathrm{H}}_2\mathrm{O}} $$
and a 1:1 relationship of molar H2O and TiO2 in these experiments. Sc-doped, enstatite-buffered experiments display a main absorption band at 3355 cm−1 with
$$ {C}_{{\mathrm{H}}_2\mathrm{O}}\propto {a_{{\mathrm{H}}_2\mathrm{O}}}^{0.5} $$
and a positive correlation of Sc and H, indicating the coupled substitution of a trivalent cation plus a H for two Mg (labelled as [triv]). Our data demonstrate that extreme care has to be taken when inferences from experiments conducted at
$$ {a}_{{\mathrm{H}}_2\mathrm{O}}=1 $$
are applied to the mantle, where in most cases, a low
$$ {a}_{{\mathrm{H}}_2\mathrm{O}} $$
persists. In particular, the higher exponent of the [Si] substitution mechanism means that the contribution of this hydrous defect to total water content will decrease more rapidly with decreasing
$$ {a}_{{\mathrm{H}}_2\mathrm{O}} $$
than the contributions of the other substitution mechanisms. The experiments confirm previous results that the [Mg] mechanism holds an almost negligible amount of water under nearly all T-P-fO2-fH2O conditions that may be anticipated in nature. However, the small amounts of H2O we find in substituting by this mechanism are similar in the experiments on forsterite doped with either Sc or Ti to those in the undoped forsterite at equivalent
$$ {a}_{{\mathrm{H}}_2\mathrm{O}} $$
(all buffered by enstatite), confirming the assumption that, thermodynamically,
$$ {C}_{{\mathrm{H}}_2\mathrm{O}} $$
substituting by each mechanism does not depend on the water concentration that substitutes by other mechanisms.
Tài liệu tham khảo
Aranovich LY, Newton RC (1996) H2O activity in concentrated NaCl solutions at high pressures and temperatures measured by the brucite-pericalse equilibrium. Contrib Mineral Petrol 125:200–212
Aubaud C et al (2007) Intercalibration of FTIR and SIMS for hydrogen measurements in glasses and nominally anhydrous minerals. Am Mineral 92(5–6):811–828
Bai Q, Kohlstedt DL (1993) Effects of chemical environment on the solubility and incorporation mechanism for hydrogen in olivine. Phys Chem Miner 19:460–471
Balan E, Ingrin J, Delattre S, Kovács I, Blanchard M (2011) Theoretical infrared spectrum of OH-defects in forsterite. Eur J Mineral 23(3):285–292
Bali E, Bolfan-Casanova N, Koga KT (2008) Pressure and temperature dependence of H solubility in forsterite: an implication to water activity in the Earth interior. Earth Planet Sci Lett 268(3–4):354–363
Bell DR, Rossman GR, Maldener J, Endisch D, Rauch F (2003) Hydroxide in olivine: a quantitative determination of the absolute amount and calibration of the IR spectrum. J Geophys Res 108
Berry AJ, Hermann J, O'Neill HSC, Foran GJ (2005) Fingerprinting the water site in mantle olivine. Geology 33(11):869
Berry AJ, O’Neill HSC, Hermann J, Scott DR (2007a) The infrared signature of water associated with trivalent cations in olivine. Earth Planet Sci Lett 261(1–2):134–142
Berry AJ, Walker AM, Hermann J, O’Neill HSC, Foran GJ, Gale JD (2007b) Titanium substitution mechanisms in forsterite. Chem Geol 242(1–2):176–186
Blanchard M, Balan E, Wright K (2009) Incorporation of water in iron-free ringwoodite: a first-principles study. Am Mineral 94(1):83–89
Blanchard M, Ingrin J, Balan E, Kovács I, Withers AC (2017) Effect of iron and trivalent cations on OH defects in olivine. Am Mineral 102(2):302–311
De Hoog JCM, Gall L, Cornell DH (2010) Trace-element geochemistry of mantle olivine and application to mantle petrogenesis and geothermobarometry. Chem Geol 270(1–4):196–215
Demouchy S, Mackwell S (2006) Mechanisms of hydrogen incorporation and diffusion in iron-bearing olivine. Phys Chem Miner 33:347–355
Demouchy S, Mackwell SJ, Kohlstedt DL (2007) Influence of hydrogen on Fe–Mg interdiffusion in (Mg, Fe)O and implications for Earth’s lower mantle. Contrib Mineral Petrol 154(3):279–289
Denis CMM, Demouchy S, Shaw CSJ (2013) Evidence of dehydration in peridotites from Eifel Volcanic Field and estimates of the rate of magma ascent. J Volcanol Geotherm Res 258:85–99
Eggins SM, Rudnick RL, McDonough WF (1998) The composition of peridotites and their minerals: a laser-ablation ICP-MS study. Earth Planet Sci Lett 154:53–71
Evans TM, O’Neill HSC, Tuff J (2008) The influence of melt composition on the partitioning of REEs, Y, Sc, Zr and Al between forsterite and melt in the system CMAS. Geochim Cosmochim Acta 72:5708–5721
Faul UH, Cline CJ, David EC, Berry AJ, Jackson I (2016) Titanium-hydroxyl defect-controlled rheology of the Earth’s upper mantle. Earth Planet Sci Lett 452:227–237
Férot A, Bolfan-Casanova N (2012) Water storage capacity in olivine and pyroxene to 14 GPa: implications for the water content of the Earth’s upper mantle and nature of seismic discontinuities. Earth Planet Sci Lett 349–350:218–230
Gaetani GA et al (2014) Hydration of mantle olivine under variable water and oxygen fugacity conditions. Contrib Mineral Petrol 167(2):965
Grant KJ, Wood BJ (2010) Experimental study of the incorporation of Li, Sc, Al and other trace elements into olivine. Geochim Cosmochim Acta 74(8):2412–2428
Grant KJ, Kohn SC, Brooker RA (2007a) The partitioning of water between olivine, orthopyroxene and melt synthesised in the system albite-forsterite-H20. Earth and Planet Sci 260: 227–241.
Grant KJ, Brooker RA, Kohn SC, Wood BJ (2007b) The effect of oxygen fugacity on hydroxyl concentrations and speciation in olivine: implications for water solubility in the upper mantle. Earth Planet Sci Lett 261(1–2):217–229
Green DH, Hibberson WO, Kovacs I, Rosenthal A (2010) Water and its influence on the lithosphere-asthenosphere boundary. Nature 467(7314):448–451
Hermann J, O’Neill HSC, Berry AJ (2005) Titanium solubility in olivine in the system TiO2-MgO-SiO2: no evidence for an ultra-deep origin of Ti-bearing olivine. Contrib Mineral Petrol 148:746–760
Holland TJB, Powell R (2011) An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids. J Metamorph Geol 29:333–383
Ingrin J et al (2013) Low-temperature evolution of OH bands in synthetic forsterite, implication for the nature of H defects at high pressure. Phys Chem Miner 40(6):499–510
Ingrin J, Kovács I, Deloule E, Balan E, Blanchard M, Kohn SC, Hermann J (2014) Identification of hydrogen defects linked to boron substitution in synthetic forsterite and natural olivine. Am Mineral 99:2138–2141
Jollands MC, Padrón-Navarta JA, Hermann J, O’Neill HSC (2016) Hydrogen diffusion in Ti-doped forsterite and the preservation of metastable point defects. Am Mineral 101(7–8):1571–1583
Karato S-I, Wang D (2013) Electrical conductivity of minerals and rocks. In: Karato S-I (ed) Physics and Chemistry of the Deep Earth. Wiley-Blackwell, New York, pp 145–182
Karato S-I, Paterson MS, FitzGerald JD (1986) Rheology of synthetic olivine aggregates: Influence of grain size and water. J Geophys Res 91(B8):8151
Kohlstedt DL (2006) The role of water in high-temperature rock deformation. Rev Mineral Geochem 62:377–396
Kohlstedt DL, Keppler H, Rubie DC (1996) Solubility of water in the α, β and γ phases of (Mg, Fe)2SiO4. Contrib Mineral Petrol 123:345–357
Kovacs I et al (2008) Quantitative absorbance spectroscopy with unpolarized light: Part II. Experimental evaluation and development of a protocol for quantitative analysis of mineral IR spectra. Am Mineral 93(5–6):765–778
Kovacs I, O'Neill HSC, Hermann J, Hauri EH (2010) Site-specific infrared O-H absorption coefficients for water substitution into olivine. Am Mineral 95(2–3):292–299
Lamb WM, Popp RK (2009) Amphibole equilibria in mantle rocks: determining values of mantle aH2O and implications for mantle H2O contents. Am Mineral 94(1):41–52
Lemaire C, Kohn SC, Brooker RA (2004) The effect of silica activity on the incorporation mechanisms of water in synthetic forsterite: a polarised infrared spectroscopic study. Contrib Mineral Petrol 147(1):48–57
Mackwell SJ, Kohlstedt DL (1990) Diffusion of hydrogen in olivine: implications for water in the mantle. J Geophys Res 95:5079–5088
Mallmann G, O’Neill HSC (2009) The crystal/melt partitioning of V during mantle melting as a function of oxygen fugacity compared with some other elements (Al, P, Ca, Sc, Ti, Cr, Fe, Ga, Y, Zr and Nb). J Petrol 50(9):1765–1794
Matveev S, O’Neill HSC, Ballhaus C, Taylor WR, Green DH (2001) Effect of silica activity on OH− IR spectra of olivine: implications for low-aSiO2 mantle metasomatism. J Petrol 42(4):721–729
Mei S, Kohlstedt DL (2000) Influence of water on plastic deformation of olivine aggregates: 1. Diffusion creep regime. J Geophys Res Solid Earth 105(B9):21457–21469
Miller GH, Rossman GR, Harlow GE (1987) The natural occurrence of hydroxide in olivine. Phys Chem Miner 14:461–472
Mosenfelder JL, Deligne NI, Asmiow PD, Rossman GR (2006) Hydrogen incorporation in olivine from 2-12 GPa. Am Mineral 91:285–294
Mosenfelder JL et al (2011) Analysis of hydrogen in olivine by SIMS: evaluation of standards and protocol. Am Mineral 96(11–12):1725–1741
O’Neill HSC (1998) Partitioning of Fe and Mn between ilmenite and olivine at 1100 °C: constraints on the thermodynamic mixing properties of (Fe, Mn)TiO3 ilmenite solid solutions. Contrib Mineral Petrol 133:284–296
Otsuka K, Karato S-I (2011) Control of the water fugacity at high pressures and temperatures: applications to the incorporation mechanisms of water in olivine. Phys Earth Planet Inter 189(1–2):27–33
Padrón-Navarta JA, Hermann J, O’Neill HSC (2014) Site-specific hydrogen diffusion rates in forsterite. Earth Planet Sci Lett 392:100–112
Pownceby MI, O’Neill HSC (2000) Thermodynamic data from redox reactions at high temperatures. VI. Thermodynamic properties of CoO–MnO solid solutions from emf measurements. Contrib Mineral Petrol 140(1):28–39
Sambridge M, Gerald JF, Kovacs I, O’Neill HSC, Hermann J (2008) Quantitative absorbance spectroscopy with unpolarized light: Part I. Physical and mathematical development. Am Mineral 93(5–6):751–764
Schmädicke E, Gose J, Witt-Eickschen G, Bratz H (2013) Olivine from spinel peridotite xenoliths: hydroxyl incorporation and mineral composition. Am Mineral 98(10):1870–1880
Shen T, Hermann J, Zhang L, Padrón-Navarta JA, Chen J (2014) FTIR spectroscopy of Ti-chondrodite, Ti-clinohumite, and olivine in deeply subducted serpentinites and implications for the deep water cycle. Contrib Mineral Petrol 167:992–1009
Smyth JR, Frost DJ, Nestola F, Holl CM, Bromiley G (2006) Olivine hydration in the deep upper mantle: effects of temperature and silica activity. Geophys Res Lett 33(15)
Soustelle V, Tommasi A, Demouchy S, Ionov DA (2010) Deformation and fluid-rock interaction in the supra-subduction mantle: microstructures and water contents in peridotite xenoliths from the Avacha Volcano, Kamchatka. J Petrol 51(1–2):363–394
Soustelle V, Tommasi A, Demouchy S, Franz L (2013) Melt-rock interactions, deformation, hydration and seismic properties in the sub-arc lithospheric mantle inferred from xenoliths from seamounts near Lihir, Papua New Guinea. Tectonophysics 608:330–345
Spandler C, O’Neill HSC (2010) Diffusion and partition coefficients of minor and trace elements in San Carlos olivine at 1,300 °C with some geochemical implications. Contrib Mineral Petrol 159(6):791–818
Tollan PME, O’Neill HSC, Hermann J, Benedictus A, Arculus RJ (2015) Frozen melt–rock reaction in a peridotite xenolith from sub-arc mantle recorded by diffusion of trace elements and water in olivine. Earth Planet Sci Lett 422:169–181
Umemoto K, Wentzcovitch RM, Hirschmann MM, Kohlstedt DL, Withers AC (2011) A first-principles investigation of hydrous defects and IR frequencies in forsterite: The case for Si vacancies. Am Mineral 96(10):1475–1479
Walker AM, Hermann J, Berry AJ, O’Neill HSC (2007) Three water sites in upper mantle olivine and the role of titanium in the water weakening mechanism. J Geophys Res 112(B5)
Withers AC, Hirschmann MM (2008) Influence of temperature, composition, silica activity and oxygen fugacity on the H2O storage capacity of olivine at 8 GPa. Contrib Mineral Petrol 156(5):595–605
Withers AC, Bureau H, Raepsaet C, Hirschmann MM (2012) Calibration of infrared spectroscopy by elastic recoil detection analysis of H in synthetic olivine. Chem Geol 334:92–98
Xue X, Kanzaki M, Turner D, Loroch D (2017) Hydrogen incorporation mechanisms in forsterite: New insights from 1H and 29Si NMR spectroscopy and first-principles calculation. Am Mineral 102:519–536
Yang X, Liu D, Xia Q (2014) CO2-induced small water solubility in olivine and implications for properties of the shallow mantle. Earth Planet Sci Lett 403:37–47
Zhao Y-H, Ginsberg SB, Kohlstedt DL (2004) Solubility of hydrogen in olivine: dependence on temperature and iron content. Contrib Mineral Petrol 147:155–161