WATER IN THE EARTH S MANTLE: NATHALIE BOLFAN-CASANOVA LABORATOIRE MAGMAS ET VOLCANS
=> Heterogeneous distribution of water in the mantle > 10000 pmm wt H2O ~ 10000 pmm wt H2O ~ 1000 pmm wt H2O
On what form do we find water? Fluids Hydrous magmas Hydrous phases?? NAMs
Pearson et al. (2005)
Water in the transition zone H2O wt% Mg2SiO4 wadsleyite Inoue et al. (1995) H2O wt % Mg2SiO4 wadsleyite Demouchy et al. (2005) H2O wt % (Mg,Fe)2SiO4 wadsleyite Kawamoto et al. (1996) H2O wt % Mg2SiO4 Ringwoodite Ohtani et al. (2000) 4 3.5 410 km 520 km 670 km 3 H 2 O wt % 2.5 2 1.5 1 0.5 Ringwoodite inclusion in diamond from Pearson et al. (2014) 0 800 1000 1200 1400 1600 1800 2000 T( C) => In agreement with water-saturated conditions
Water recycling through subduction
Peridotite + H 2 O phase diagram redrawn from Iwamory (2004) from Syracuse et al. (2010) => Slabs are not that hot after all
H defects are ubiquituous in most mantle samples Demouchy et al. (2004) Demouchy and Bolfan-Casanova (2015)
Water circulation in cratons => water content in NAMs from enoliths in kimberlite Shirey et al. (2013)
Water circulation in cratons => new messages from NAMs inclusions in diamonds Novella et al. (2015) => Maimum 5 ppm wt H 2 O in olivine Shirey et al. (2013)
Effect of CO 2 on water incorporation Sokol et al. (2013)
Constraints on the water content in the mantle From the water content in MORBs: -> [H2O] MORB ~3000 ppm wt -> water partitioning D solid/liquid ~0.01 -> melting degree F = 10% => [H2O]source = 300 ppm pds
Constraints on the water content in the mantle From the water content in MORBs From the water content in NAMs in mantle enoliths Mineral Water contents (ppm wt H 2 O) Olivine < 1 to > 100 Orthopyroene 100-450 Clinopyroene up to 1200 Garnet < 1 to 200 * kimberlites and alkali basalts 250 ppm by weight in the source, the lithospheric mantle! Volatile loss during ascent Bell and Rossmann (1992)
Diffusion profile of H across olivine Demouchy et al. (2004) => Water content in the source under-estimated
Why is such water important? What are the effects of water on mantle physical properties?
Effect of water on mantle melting Aubaud et al. (2004) The melt fraction is higher Melting starts at higher depth
Effect of water on chemical diffusion Hier-Majumder et al. (2005)
D Me X V and X V C OH Hier-Majumder et al. (2005)
AC r H OHep( RT H ) Gardès et al. (2014)
Seismic discontiuities Frost and Doleij (2007)
Elastic softening Effect of hydration on density Jacobsen (2006)
Jacobsen (2006)
WHAT IS THE STORAGE OF WATER IN THE EARTH S MANTLE NATURAL SYNTHETIC Coutrsy of S. Demouchy Irifune and Isshiki (1998)
Water storage capacity of the Earth s? Eperimental approach + Absorption coefficient (cm -1 ) 450 350 250 150 3630 3612 3599 3579 3566 3491 3550 3542 3532 FTIR 3476 3445 3381 forsterite synthesized hydrothermally at 9 GPa and 1250 C // a ais // b ais 50 3160 // c ais 3600 3500 3400 3300 3200 3100 Wavenumber (cm -1 ) From Bali et al. (2008)
Incorporation of water in NAMs In olivine: Mg 2+ = 2 H +
Incorporation of water in NAMs In olivine: Mg 2+ = 2 H + Notation de Kröger Vink : Mg Me + OO + H2 O = 2 OH O. + VMe + MgO i.e. MgSiO 3 + Mg Me + 2OO + H2 O = 2 OH O. + VMe + Mg 2 SiO 4
Incorporation of water in NAMs In olivine: Mg 2+ = 2 H + Notation de Kröger Vink : Mg Me + OO + H2 O = 2 OH O. + VMe + MgO i.e. MgSiO 3 + Mg Me + 2OO + H2 O = 2 OH O. + VMe + Mg 2 SiO 4 (2H) Me
Incorporation of water in NAMs In olivine: Mg 2+ = 2 H + Notation de Kröger Vink : i.e. MgSiO 3 + Mg Me + 2OO + H2 O = (2H) Me + Mg 2 SiO 4 [(2H a a Mg2SiO4 Me)] K fh2o MgSiO3 n [OH] 2 ep( RT G O ) fh2
Incorporation of water in NAMs In olivine: Mg 2+ = 2 H + Notation de Kröger Vink : soit MgSiO 3 + Mg Me + 2OO + H2 O = (2H) Me + Mg 2 SiO 4 [(2H a a Mg2SiO4 Me)] K fh2o MgSiO3 [OH] A(P) fh2 n ep( O n [OH] 2 ep( RT G O ) fh2 H RT P V ) and n=1
Incorporation of water in NAMs In garnet : Si 4+ = 4 H + Notation de Kröger Vink : Si Si + OO + 2 H2 O = 4 OH O. + VSi + SiO 2
Incorporation of water in NAMs In garnet : Si 4+ = 4 H + Notation de Kröger Vink : Si Si + OO + 2 H2 O = 4 OH O. + VSi + SiO 2 (4H) Si
Incorporation of water in NAMs In garnet : Si 4+ = 4 H + Notation de Kröger Vink : Si Si + OO + 2 H2 O = 4 OH O. + VSi + SiO 2 [(4H Si )] a K SiO2 f 2 H2O n [OH] 4fH2O ep( RT G )
Incorporation of water in NAMs Dans le grenat : Si 4+ = 4 H + Notation de Kröger Vink : Si Si + OO + 2 H2 O = 4 OH O. + VSi + SiO 2 [(4H Si )] a K SiO2 f 2 H2O [OH] A(P) fh2 n ep( O n [OH] 4fH2O ep( RT G ) H RT P V ) and n=2
Incorporation of water in NAMs In enstatite: incorporation of aluminum Anhydrous case: Mg 2+ + Si 4+ = 2Al 3+ (Mg Al)(Al Si) O 6 (Tschermak) Hydrous case 1: 2 Mg 2+ = Al 3+ + H + (H Al)(Si Si) O 6 Hydrous case 2: Si 4+ = Al 3+ + H + (Mg Mg) (Al H) Si O 6 Keppler and Bolfan-Casanova (2006)
Recycling of H at low temperature in the wedge mantle Thermodynamics of H incorporation [OH] 2 ep( RT G O ) fh2 Pression kj/mole) S J/mole/K) V cc/mole) 2.5-12 GPa 37.1 ±7.6 82.8 ± 6.8 10.6 Kohlstedt et al. (1996) Mosenfelder et al. (2006) Zhao et al. (2006) Bali et al. (2008) Férot and Bolfan-Casanova (2012)
Recycling of H at low temperature in the wedge mantle 10 4 Thermodynamics of H incorporation [OH] 2 ep( RT G O ) fh2 Pression kj/mole) S J/mole/K) V cc/mole) 2.5-12 GPa 37.1 ±7.6 82.8 ± 6.8 10.6 log [H2O] ppm wt 1000 100 10 0.3 GPa 2.5 GPa 5 GPa 7.5 GPa Kohlstedt et al. (1996) Mosenfelder et al. (2006) Zhao et al. (2006) Bali et al. (2008) Férot and Bolfan-Casanova (2012) 1 600 800 1000 1200 1400 T( C)
Recycling of H at low temperature in the wedge mantle 10 4 Thermodynamics of H incorporation [OH] 2 ep( RT G O ) fh2 Pression kj/mole) S J/mole/K) V cc/mole) 2.5-12 GPa 37.1 ±7.6 82.8 ± 6.8 10.6 log [H2O] ppm wt 1000 100 10 0.3 GPa 2.5 GPa 5 GPa 7.5 GPa 3 GPa Kohlstedt et al. (1996) Mosenfelder et al. (2006) Zhao et al. (2006) Bali et al. (2008) Férot and Bolfan-Casanova (2012) 1 600 800 1000 1200 1400 T( C)
410-km Water storage in olivine in simple MFASH system 1600 Férot and Bolfan-Casanova (2012) Ardia et al. (2012) 1450 C Tenner et al. (2012) 1400 C Water content (ppm wt H 2 O) 1200 800 400 0 2 4 6 8 10 12 14 P (GPa)
Partitioning of water into orthopyroene Férot and Bolfan-Casanova (2012)
Partitioning of water into orthopyroene 3 y = 2.9967-0.3097 + 0.0133 ² 2.5 Dp/ol 2 1.5 1 2 4 6 8 10 12 14 P(GPa) Férot and Bolfan-Casanova (2012)
Water storage in the convecting upper mantle For garnet : D water gt/ol of 0.9 Novella et al. (2014) at 6 GPa and 1400 C water storage (ppm wt H O) 2 1400 1200 1000 800 600 400 Ol contribution OPX contribution CPX contribution GT contribution Mantle storage curve +/- 100 ppm 200 0 0 50 100 150 200 250 300 350 400 depth (km)
Water storage in the convecting upper mantle ~ 800 ppm wt H 2 O at the base of the upper mantle => In agreement with estimates for the source of Reunion Island OIB water storage (ppm wt H O) 2 1400 1200 1000 800 600 400 Ol contribution OPX contribution CPX contribution GT contribution Mantle storage curve +/- 100 ppm 200 0 0 50 100 150 200 250 300 350 400 depth (km) From Férot and Bolfan-Casanova (2012)
Rewind Water content in the deep upper mantle is anchored at a minimum of 800 ppm wt H 2 O. Olivine can transport ~1000 ppm wt H 2 O in the subducting slab. Different type of fluids travel through cratons through their history.
Eperimentally determined water storage in olivine Low Velocity Zone P (GPa) 2000 2 4 6 8 10 12 14 Water storage average Water content (ppm wt H 2 O) 1500 1000 500 850 +/- 100 ppm wt H 2 O in simple MFASH system 0 50 100 150 200 250 300 350 400 410 km From Férot and Bolfan-Casanova (2012) depth (km) => Water storage in olivine reaches ~ 1000 ppm wt H 2 0 at the 410 km discontinuity
Implications for the water content determination in the upper mantle Low velocity layer above the 410 km discontinuity Tauzin et al. (2010) LVL interpreted as being due to the occurence of melt The presence of water is necessary to invoke melting
L eau dans le manteau inférieur Bolfan-Casanova et al. (2000)