Melting Regions of the Mantle
Terry Plank: LDEOwith C-T. Lee (Rice)D. Forsyth (Brown)E. Hauri (Carnegie )K.Fischer (Brown)G. Abers (LDEO)D.Wiens (Wash U)
Boundary Layers and Melting
b.holtzman 2009
Boundary layerdynamics drive melting
melt extractioncreates lithosphere
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East Pacific RiseMELT Experiment
Forysth et al (1998)
Japan Volcanic ArcP-wave tomography
Zhao et al (1992)
What does RED mean?
1. Hot ?2. Wet?3. Melt ?
from Yang and Forsyth, 2006, JGR
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Southern California shear velocity anomaly (70-90 km depth)
0
1
2
3
1100 1200 1300 1400 1500
Temperature (°C)
Pre
ssu
re (
GP
a)
Melt Thermobarometers
drysolidus
Solidus from Hirschmann (2000)
olivine-melt thermometer
MgOol MgOliq
D = = f (T)
40km
70
100
+/- 30 °C
0
1
2
3
1100 1200 1300 1400 1500
Temperature (°C)
Pre
ssu
re (
GP
a)
Melt Thermobarometers
drysolidus
Solidus from Hirschmann (2000)
olivine-melt thermometer
silica-melt baromometer
MgOol MgOliq
D = = f (T)
Mg2SiO4ol + SiO2
liq =
Mg2Si2O6opx
a(SiO2)liq ~ 1/K
Thermobarometer parameterizations from C-T Lee et al, EPSL, 2009
40km
70
100+/- 0.2 GPa
+/- 30 °C
0
1
2
3
1100 1200 1300 1400 1500
Temperature (°C)
Pre
ssu
re (
GP
a)
Melt Thermobarometers
drysolidus
Solidus from Hirschmann (2000)
olivine-melt thermometer
silica-melt baromometer
MgOol MgOliq
D = = f (T)
Mg2SiO4ol + SiO2
liq =
Mg2Si2O6opx
Thermobarometer parameterizations from C-T Lee et al, EPSL, 2009
4.5 wt%H2O
40km
70
100
a(SiO2)liq ~ 1/K
For H2O, we need melt inclusionsin olivine from well-quenched tephra
Benjamin, Plank, Wade, Hauri & Alvarado (JVGR, 2007)
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1. East Pacific Rise
3. Central American Arc
4. Basin and Range
Examples of Melting Regions
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1. East Pacific Rise(MELT and GLIMPSE)
Ridge
Harmon, Forsyth, Weeraratne (EPSL, 2009)
Shear velocity model
0
1
2
3
4
1100 1200 1300 1400 1500 1600
Temperature (°C)P
ress
ure
(GP
a)
oceanic crust
Pacific off-axis
Nazca off axis
on-axis
80 km
50 km
110 km
15 km
P-T calculated from thermobaromters in Lee et al (EPSL, 2009): Fo90, 100% Fe2+; H2O = 0.1 wt%
Most MORB data from Sinton et al (JGR, 1991) and Hall et al (G3, 2006); all > 8.2 wt% MgO
method in LKP92and Wiens et al (2006)
100 ppm H2 O
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Ridge
Harmon, Forsyth, Weeraratne (EPSL, 2009)
Shear velocity model
dry solidus
magmas
solidus with 100 ppm H2O
Tp = 1470°C
0 50 100
0
40
80
120km
1300 1400 1500 0 10 20
Harmon, Forsyth, Weeraratne (EPSL, 2009)
Shear velocity model
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Ridge
dry solidus
magmas
solidus with 100 ppm H2O
Temperature (°C)
ppm H2O
% Melting
km
Tp = 1470°CTp = 1470°C
Wet melting model after Langmuir et al (2006)
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From Conder et al (JGR, 2002)
test dynamic models
0
50
100
150
2003.8 4.0 4.2 4.4 4.6 4.8
Shear velocity (km/s)
Depth(km)
Model that satisfiesQ = 80; Tp = 1350°C
derived fromRayleigh waves
melt?
…or Tp = 1450°C
After Yang & Forsyth (EPSL, 2007)
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2. Back-arc Basins
Wiens, Kelley & Plank (EPSL, 2006)
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S wave velocity (km/s) N. Lau & N. Fiji
Mariana Tr. & Scotia
Wiens, Kelley & Plank (EPSL, 2006)
(dry melts only)
MELT
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Wiens, Kelley & Plank (EPSL, 2006)
S.EPR(MELT)?
Temperature variations on Vs
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3. Volcanic Arc
Rychert, Fisher, Abers, Plank, Syracuse, Protti, Gonzalez, Strauch (G3, 2008)
Syracuse, Abers, Fischer, MacKenzie, Rychert, Protti, Gonzalez, Strauch (G3, 2008)
Syracuse, Abers, Fischer, MacKenzie, Rychert, Protti, Gonzalez, Strauch (G3, 2008)
Rychert, Fisher, Abers, Plank, Syracuse, Protti, Gonzalez, Strauch (G3, 2008)
Olivine-liquidus depression due to water from Medard and Grove (2007))
US Array:Transportable Array
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from Deuker et al, 2001, JGR
from Yang and Forsyth, 2006, JGR
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LV = Long ValleyBP = Big PineGT = Golden TroutC = Coso
70-90 km depth
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Lathrop Wells volcano70,000 yrs old18 km south of Yucca Mnt
Yucca Mnt
Wang, Plank, Walker and Smith, JGR, 2002
Mantle Melting Profile Across B&R
dark green columns =
+ ε(Nd) (astheno.)
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120°W 118 116 114 112
0km
50
100
150
Transect at 37°N
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Courtesy of Yingjie Yang (Yang, Ritzwoller, Lin, Moschetti, Shapiro, JGR, in press)
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120°W 118 116 114 112
0km
50
100
150
Transect at 37°N
BP
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Courtesy of Yingjie Yang (Yang, Ritzwoller, Lin, Moschetti, Shapiro, JGR, in press)
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120°W 118 116 114 112
0km
50
100
150
Courtesy of Yingjie Yang (Yang, Ritzwoller, Lin, Moschetti, Shapiro, JGR, in press)
Transect at 37°N
BP
LW SC
1200-1340°C1.8 wt% H2O
1365-1390°C3.2 wt% H2O
1445-1460°C0.9 wt% H2OTp=1350
Tp=1390 Tp=1440
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1. East Pacific Rise
3. Central American Arc
4. Basin and Range
Examples of Melting Regions
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presence of melt
mantle Tp variations
effect of water on Q
mapping T, melt and H2O