Stability of melt-rich channels in Earth’s mantle

High Pressure and Temperature Experiments of Olivine, Chromite and Mid-Ocean Ridge Basalt (MORB)

Kristyn RodzinyakDan King, PhD student,

Rock and Mineral Physics Lab, Department of Geology and Geophysics, University of Minnesota, Minneapolis

Mark Zimmerman, UMNDavid Kohlstedt, UMN

Melt Transport

•Modeling Mantle Convectionhttp://www.yorku.ca/esse/veo/earth/image/1-3-2.JPG

Stress Driven Melt Segregation

• Mid-Ocean Ridges

•Subduction Zones

http://www.waterencyclopedia.com/images/wsci_03_img0352.jpg

http://sio.ucsd.edu/volcano/about/images/recycle.gif

http://visearth.ucsd.edu/VisE_Int/platetectonics/hotspot2.jpg

•Hot Spots

Samples

Composition• 4 to 1 by volume 8 µm olivine and 2 µm chromite • 4% mid-ocean ridge basalt (MORB)

Torsion Static Anneal

Sample Preparation

Deformation Assembly

Experiments

Gas-medium deformation apparatus PI-10

Torsion Actuator

Pressure Vessel

Leak Detector

Thermocouple

300 MPa

~10 Km depth

Torsion, 1473K, 300 MPA Data during first deformation.

A slow leak (1MPa/ 6 mins) caused the termination of the experiment.

Torsion, 1473K, 200MPa Second deformation on sample once rejacketed.

Run terminated due to a slip along a boundary indicated by a drastic drop in plots.

Melt-Rich Bands

1000µm

No Bands

BandsBands

Results-Torsion

20 µm

0510152025

0 5 10 15 20Melt Percentage

Distance (microns)Dis

tan

ce (

mic

ron

s)

Results-Static Anneal

20 µm

0510152025

0 5 10 15 20 25Melt percentage

Distance (microns)Dis

tan

ce

(mic

ron

s)

2 µm

Scanning Electron Microscope

Que

nche

d

1 ho

ur a

nnea

l

10 h

our

anne

al

Conclusions

• Bands still visible after 10 hour anneal • Suggests driving force for segregation

stronger than the dissipation force • Surface tension driven flow tends to

homogenize melt distribution through time• On planetary objects where gravity is less

than that of Earth, surface tension would likely play a larger role

David Kohlstedt’s Rock and Mineral Physics Lab

Special Thanks To…

• David Kohlstedt’s Rock and Mineral Physics Lab

• Funding provided by NASA’s PGGURP: Planetary Geology and Geophysics Undergraduate Research Program