estimating mantle temperature and composition from seismic models (and other data)
DESCRIPTION
Estimating mantle temperature and composition from seismic models (and other data). Colleen Dalton, Boston University with Allie Gale, Charlie Langmuir, Uli Faul, Mollie Celnick, and others . Seismological Models. S362ANI 300 km Kustowski et al. (2008). S40RTS 300 km - PowerPoint PPT PresentationTRANSCRIPT
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Estimating mantle temperature and composition
from seismic models (and other data)
Colleen Dalton, Boston University
with Allie Gale, Charlie Langmuir, Uli Faul, Mollie Celnick, and others
![Page 2: Estimating mantle temperature and composition from seismic models (and other data)](https://reader035.vdocument.in/reader035/viewer/2022062521/5681680b550346895ddd90d4/html5/thumbnails/2.jpg)
Seismological Models
S362ANI 300 kmKustowski et al. (2008)
S40RTS 300 kmRitsema et al. (2010)
QRFSI12 300 kmDalton et al. (2008)
Transition Zone ThicknessLawrence & Shearer (2008)
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MORB Composition
Hotter mantle:•melting initiates deeper•larger extent of melting•lower Na in MORB•higher Fe in MORB•thicker oceanic crust•shallow ridge depths
modified fromLangmuir & Forsyth 2007
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540 segments without “8 values”
RIDGE nseg Length (km)
Mid-Atlantic 255 16,594
SE Indian 79 7,268
E. Pacific Rise 76 7,326
SW Indian 67 4,624
Central Indian 61 3,860
Pac-Ant Ridge 46 5,454
Afar 36 3,483
Chile Rise 27 1,462
Gakkel 18 1,907
Juan de Fuca 17 1,003
Galap. Ridge 17 2,127
AAR 10 514
Back Arcs 62 5,242
TOTAL 771 60,864
Definition of Ridge Segments
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Humler et al. (1993)
This study
MORB Composition
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Ridge Depth vs. S-Velocity
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P = Dwwg+Dccg+Drrg+Dmmg
Calculation of Water Depth: Isostasy
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1250oC
1370oC
Calculation of Water Depth and Seismic Velocity
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Comparison of Na8 and Seismic Velocity
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Effect of Composition on VS
3 GPa (~90 km) and 800oC
Mg# = Mg / (Mg + Fe)
garnet faciesspinel faciespyrolite 0.1 km/s ~ 2%
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Cratonic Temperature & Composition
150 km
Lee et al. (2010)
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CIDER
1. Possible themes:tectonic settings: cratons; ridges; transform faults; hotspots
no theme? research projects based on who is there
2. Other things to consider: more time for research: start research projects right away
some research lectures in addition to overview lectures
opportunity to make progress with collaborators
support for meetings in person after summer crucial
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Parameter Velocity AttenuationTemperatureComposition ?Melt Water ?
Transition zone thickness
Seismological Models
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Zhang et al. (1994)
Wiens et al. (2006)
Previous Studies
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Courtier et al. (2007)
Velocity variation (%)
Na 8
.0
Humler et al. (1993)
Previous Studies
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median = -3246 m
Definition of Ridge Segments
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MAR SEIRResolution of Seismic Models
EPR
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Resolution of Seismic Models
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SWIR SEIR
MAR
longitude
longitudelatitude