Melting Regions of the Mantle

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

QuickTime™ and a decompressor

are needed to see this picture.

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





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)


drysolidus



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)


drysolidus



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)







1. East Pacific Rise

3. Central American Arc

4. Basin and Range

Examples of Melting Regions


are needed to see this picture.2. Back-arc Basins





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



Ridge



dry solidus

magmas

solidus with 100 ppm H2O

Tp = 1470°C

0 50 100

0

40

80

120km

1300 1400 1500 0 10 20





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)





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)



2. Back-arc Basins

Wiens, Kelley & Plank (EPSL, 2006)





S wave velocity (km/s) N. Lau & N. Fiji

Mariana Tr. & Scotia


(dry melts only)

MELT




S.EPR(MELT)?

Temperature variations on Vs



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



from Deuker et al, 2001, JGR

from Yang and Forsyth, 2006, JGR



LV = Long ValleyBP = Big PineGT = Golden TroutC = Coso

70-90 km depth



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.)



120°W 118 116 114 112

0km

50

100

150

Transect at 37°N



Courtesy of Yingjie Yang (Yang, Ritzwoller, Lin, Moschetti, Shapiro, JGR, in press)



120°W 118 116 114 112

0km

50

100

150

Transect at 37°N

BP








120°W 118 116 114 112

0km

50

100

150


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







1. East Pacific Rise

3. Central American Arc

4. Basin and Range

Examples of Melting Regions


are needed to see this picture.2. Back-arc Basins

presence of melt

mantle Tp variations

effect of water on Q

mapping T, melt and H2O

Documents

Melting Regions of the Mantle