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Estimating mantle temperature and composition

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Presentation on theme: "Estimating mantle temperature and composition"— Presentation transcript:

1 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

2 Transition Zone Thickness
Seismological Models S362ANI 300 km Kustowski et al. (2008) S40RTS 300 km Ritsema et al. (2010) QRFSI km Dalton et al. (2008) Transition Zone Thickness Lawrence & Shearer (2008)

3 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 from Langmuir & Forsyth 2007

4 Definition of Ridge Segments
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 2,127 AAR 10 514 Back Arcs 62 5,242 TOTAL 771 60,864

5 MORB Composition Humler et al. (1993) This study

6 Ridge Depth vs. S-Velocity

7 Calculation of Water Depth: Isostasy
P = Dwwg+Dccg+Drrg+Dmmg

8 Calculation of Water Depth and Seismic Velocity

9 Comparison of Na8 and Seismic Velocity

10 Effect of Composition on VS
3 GPa (~90 km) and 800oC garnet facies spinel facies pyrolite 0.1 km/s ~ 2% Mg# = Mg / (Mg + Fe)

11 Cratonic Temperature & Composition
150 km Lee et al. (2010)

12 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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14 Seismological Models ? Parameter Velocity Attenuation Temperature
Composition ? Melt Water Transition zone thickness

15 Previous Studies Wiens et al. (2006) Zhang et al. (1994)

16 Previous Studies Na8.0 Velocity variation (%) Courtier et al. (2007)
Humler et al. (1993)

17 Definition of Ridge Segments
median = m

18 Resolution of Seismic Models
MAR SEIR EPR

19 Resolution of Seismic Models

20 SWIR SEIR longitude longitude MAR latitude


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