Rock and Mineral Physics Lab University of Minnesota Dept of Geology & Geophysics

Takehiko Hiraga, Research associate

PhD., Earth Science, 2000, Tohoku University

Contact Information

Dept. of Geology & Geophysics
310 Pillsbury Dr SE
Minneapolis, MN 55455

 

Office: Kolthoff Hall P168

Ph: 612-626-0572
Fax: 612-625-3819
Email: hirag001@umn.edu

 

Current Project

I have been investigating grain boundaries in rocks since my PhD work in Tohoku University. Even though they are "tiny" (like me), I have a strong opinion that they play fundamental roles in Earth dynamics, via grain boundary diffusion, grain boundary melting, grain boundary fracture, grain boundary sliding, grain boundary segregation, grain boundary migration, etc. Also, whenever we are looking at rocks microstructures, people try to get geological information from the shape of the grains; however, we look it as the shape of grain/interphase boudaries instead, since the boundaries do determine the shape of grains! Therefore, the boundary structures produce wide varieties of the rocks texture.

We are focusing on grain boudary structure, energy, and chemistry. Recently, we are proposing that the grain boundaries can be the main storage sites for incompatible elements in the Earth's mantle. Grain boundary segreation, a new concept for geochemisry certainly affects the basis of geochemistry; elemental partitioning of crystal-fluid and crystal-crystal. We are proposing that grain boundaries must be taken into account.

The progress of grain boundary studies is parallel to the development of transimission electron microscope. The microscopy enables us to obtain structural and chemical information with spatial resolution of sub-nanometer. Such resolution is necessary for the grain boundary studies, since they are very narrow (< 0.5 nm, see our work). We are slowly unveiling the mystery of the grain boundaries in the Earth's interior....

Publications

Hiraga T, Nagase T, Akizuki M (1999) The structure of grain boundaries in granite-origin ultramylonite studied by high-resolution electron microscopy. Physics and Chemistry of Minerals 26:617-623 3.

Masuda T, Hiraga T, Ikei H, Kanda H, Kugimiya Y, Akizuki M (2000) Plastic deformation of quartz at room temperature: a Vickers nano-indentation test. Geophysical Research Letters 27:2773-2776 @@@

Hiraga T, Nishikawa O, Nagase T, Akizuki M (2001) Morphology of intergranular pores and wetting angles in pelitic schists studied by transmission electron microscopy. Contributions to Mineralogy and Petrology 141:613-622

Hiraga T, Nishikawa O, Nagase T, Akizuki M, Kohlstedt DL (2002) Interfacial energies for quartz and albite in pelitic schists. Contributions to Mineralogy and Petrology 143:664-672

Mei S, Bai W, Hiraga T, Kohlstedt DL (2002) Influence of melt on the creep behavior of olivine-basalt aggregates under hydrous conditions. Earth and Planetary Science Letters 201:491-507 @

Hiraga T, Anderson IM, Zimmerman ME, Mei S, Kohlstedt DL (2002) Structure and chemistry of grain boundaries in deformed, olivine + basalt and partially molten lherzolite aggregates: Evidence of melt-free grain boundaries. Contributions to Mineralogy Petrology 144: 163-175

Hiraga T, Anderson IM, Kohlstedt DL (2003) Chemistry of grain boundaries in mantle rocks. American Mineralogist 88: 1015-1019

Holtzman BK, Kohlstedt DL, Zimmerman ME, Heidelbach F, Hiraga T, Hustoft J (2003) Melt segregation and strain partitioning: implications for seismic anisotropy and mantle flow. Science 301: 1227-1230@@@@

Hiraga T, Anderson IM, Kohlstedt DL (2004) Grain boundaries as reservoirs of incompatible elements in the Earth's mantle. Nature 427: 699-703

Wang Z, Hiraga T, Kohlstedt DL (2004) Effect of hydrogen on Fe-Mg interdiffusion in olivine. Applied Physics Letters 85: 209-211

Invited and seminar talks

Earthquake Research Institute, Tokyo University (9/6/02)

American Geophysical Union, Tectonophysics Section (12/6/02)

University of Yale (12/1/03)

Woods Hole Oceanographic Institute (12/2/03)

American Geophysical Union, Tectonophysics Section (12/10/03)

Univesity of Montpellier (7/22/04)

Brown University (11/4/04)

Awards

2004 Young researcher award of the Japanese Association of Mineralogists, Petrologists and Economic Geologists

Favorite Links

 Jason Amundson My personal web My parents' web