Water and Mantle Melting: Water and Mantle Melting How water influences the melting function
- depression of solidus
- dF/dT, dF/dP etc.
Effects on composition of melts
Importance to mantle rheology and dynamics
Water storage in anhydrous minerals : Water storage in anhydrous minerals
Water-saturated solidus: Water-saturated solidus
Water-saturated solidus: Water-saturated solidus
Water-saturated solidus: Water-saturated solidus
Depth to the under-saturated solidus: Approach I. Regression of experimental data. : Depth to the under-saturated solidus: Approach I. Regression of experimental data.
Depth to the under-saturated solidus: Approach I. Regression of experimental data.: Depth to the under-saturated solidus: Approach I. Regression of experimental data.
Depth to the under-saturated solidus: Approach I. Regression of experimental data. II. : Depth to the under-saturated solidus: Approach I. Regression of experimental data. II. =XH2OBulk/[DH2O(1-F)+F]
Depth to the under-saturated solidus: Approach I. Regression of experimental data.: Depth to the under-saturated solidus: Approach I. Regression of experimental data.
Depth to the under-saturated solidus: Approach II. Theory-based & constrained by water-saturated & dry solidi. : Depth to the under-saturated solidus: Approach II. Theory-based & constrained by water-saturated & dry solidi.
Depth to the under-saturated solidus: Approach II. Theory-based & constrained by water-saturated & dry solidi: Depth to the under-saturated solidus: Approach II. Theory-based & constrained by water-saturated & dry solidi water-saturated solidus
aH2O=1 dry solidus aH2O=0 Map contours of aH2O between dry & saturated solidi. This gives Tsolidus(aH2O,P)
Next we need to know aH2O....
Depth to the under-saturated solidus: Approach II. Theory-based & constrained by water-saturated & dry solidi: Depth to the under-saturated solidus: Approach II. Theory-based & constrained by water-saturated & dry solidi 2) Compute fraction saturation XH2O(P)=Col0/ Colsat(P) Olivine water content: Col0 of MORB source Colsat(P) (there’s something wrong with the data &/or analysis used for this part)
Depth to the under-saturated solidus: Approach II. Theory based & constrained by data for water-saturated & dry solidi: Depth to the under-saturated solidus: Approach II. Theory based & constrained by data for water-saturated & dry solidi 2) Compute fraction saturation XH2O(P)=Col0/ Colsat(P) 3) aH2O(P)=lXH2O(P), with activity coefficient l = 1.0
Depth to the under-saturated solidus: Approach II. : Depth to the under-saturated solidus: Approach II. water-saturated solidus
aH2O=1 dry solidus aH2O=0 Map aH2O (in the solid) onto P-T phase diagram, Tsolidus(aH2O,P)
Compute fraction saturation XH2O(P)=Col0/ Colsat(P)
aH2O(P)=lXH2O(P), with activity coefficient l = 1.0
Combine (1) and (3) to get Tsolidus(aH2O (P) ,P) Tsolidus(P)
Depth to the under-saturated solidus: Approach III. adapted from Hirth and Kohlstedt: Depth to the under-saturated solidus: Approach III. adapted from Hirth and Kohlstedt
Depth to the under-saturated solidus: Approach III. adapted from Hirth and Kohlstedt: Depth to the under-saturated solidus: Approach III. adapted from Hirth and Kohlstedt pMELTS can deal with H2O in anhydrous minerals only hydrous minerals, melt, or vapor therefore...
-Compute aH2O in olivine like HK,
-Solves equilibrium mineralogy
-Checks if pMELTS predicts melt or vapor phase
Melting between the hydrous and dry solidus dF/dT, dF/dP: Melting between the hydrous and dry solidus dF/dT, dF/dP I. Katz et al.’s parameterization
Melting between the hydrous and dry solidus dF/dT, dF/dP: Melting between the hydrous and dry solidus dF/dT, dF/dP I. Katz et al.’s parameterization
Melting between the hydrous and dry solidus dF/dT, dF/dP: Melting between the hydrous and dry solidus dF/dT, dF/dP II. Hirth and Kohlstedt water-saturated solidus
aH2O=1 dry solidus aH2O=0 Batch melting equation gives
F=[Col0/Col-1]D0/(1-D0)
Col0=810 ppm at z=115 km
Col=360 ppm at z=92 km
dF/dz~1%/20 km 92 115
Melting between the hydrous and dry solidus dF/dT, dF/dP: Melting between the hydrous and dry solidus dF/dT, dF/dP III. Azimow et al.
Pressure- & concentration- dependent water-mineral D’s
Compute water contents & activities in minerals after HK
Equilibrium mineralogy & melt fraction
Water and Mantle Melting: Water and Mantle Melting How water influences the melting function
- depression of solidus
- dF/dT, dF/dP etc.
Effects on composition of melts
Importance to mantle rheology and dynamics
Importance of Hydrous Melting on Magma Composition: Importance of Hydrous Melting on Magma Composition
Importance of Hydrous Melting on Magma Composition: Importance of Hydrous Melting on Magma Composition Ito and Mahoney [2006, 2006]
Slide24: Azimow et al. [2004]
Data from Mid-Atlantic Ridge near Azores hotspot
Light lines- computed primary magma
Heavy lines- corrected for low-P fractionation
Importance of Hydrous Melting on Mantle Dynamics: Importance of Hydrous Melting on Mantle Dynamics Hirth & Kohlstaedt [1996]: olivine with 810 ppm H2O is ~102 less viscous than dry olivine.
Importance of Hydrous Melting on Mantle Dynamics: Importance of Hydrous Melting on Mantle Dynamics Hirth & Kohlstaedt [1996]: olivine with 810 ppm H2O is ~102 less viscous than dry olivine.
Importance of Hydrous Melting on Mantle Dynamics: Importance of Hydrous Melting on Mantle Dynamics
Importance of Hydrous Melting on Mantle Dynamics: Importance of Hydrous Melting on Mantle Dynamics Controls the flattening of seafloor subsidence and
limits lithospheric thickening on old seafloor? Ritzwoller et al.,
[EPSL, 226, 2004]
Importance of Hydrous Melting on Mantle Dynamics: Importance of Hydrous Melting on Mantle Dynamics Limits buoyant upwelling and melt production at hotspots
Water and Mantle Melting: Water and Mantle Melting How water influences the melting function
- depression of solidus
- dF/dT, dF/dP etc.
Effects on composition of melts
Importance to mantle rheology and dynamics