TY - JOUR
T1 - Slow Si-Al interdiffusion in garnet and stagnation of subducting slabs
AU - Nishi, Masayuki
AU - Kubo, Tomoaki
AU - Ohfuji, Hiroaki
AU - Kato, Takumi
AU - Nishihara, Yu
AU - Irifune, Tetsuo
N1 - Funding Information:
We thank A. Shimojuku, T. Kawazoe, T. Ohuchi, N. Nishiyama, and K. Fujino for their helpful comments and two anonymous reviewers for careful reviews. We are also grateful to T. Shinmei for assistance with the high-pressure and high-temperature experiments. M. Nishi was supported by Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists .
PY - 2013/1/1
Y1 - 2013/1/1
N2 - Si4++M2+↔2Al3+ (M=Mg+Fe+Ca) interdiffusion rates in majoritic garnet have been determined at pressure of 17GPa and temperatures of 1550-1700°C using a Kawai-type high-pressure apparatus. The diffusion profiles were measured across the interface between pyropic garnet and majoritic garnet samples by an analytical transmission electron microscope, and the rate of the Si4++M2+↔2Al3+ interdiffusion was determined to be a DSi-Al (m2s-1)=2×10-10exp [-364 (kJmol-1)/RT]. We found that the diffusion rate is low compared to the Si diffusion rate in other silicate minerals relevant to the deep mantle. Slow kinetics of the pyroxene-garnet transformation due to the low diffusion rate indicates that large low-density metastable regions may exist in the slab, greatly contributing to the slab stagnation around the transition region. Stagnant slabs possibly stay in this region over 108yr because of the sluggish pyroxene-garnet transformation, but may eventually fall into the lower mantle after the completion of the transformation.
AB - Si4++M2+↔2Al3+ (M=Mg+Fe+Ca) interdiffusion rates in majoritic garnet have been determined at pressure of 17GPa and temperatures of 1550-1700°C using a Kawai-type high-pressure apparatus. The diffusion profiles were measured across the interface between pyropic garnet and majoritic garnet samples by an analytical transmission electron microscope, and the rate of the Si4++M2+↔2Al3+ interdiffusion was determined to be a DSi-Al (m2s-1)=2×10-10exp [-364 (kJmol-1)/RT]. We found that the diffusion rate is low compared to the Si diffusion rate in other silicate minerals relevant to the deep mantle. Slow kinetics of the pyroxene-garnet transformation due to the low diffusion rate indicates that large low-density metastable regions may exist in the slab, greatly contributing to the slab stagnation around the transition region. Stagnant slabs possibly stay in this region over 108yr because of the sluggish pyroxene-garnet transformation, but may eventually fall into the lower mantle after the completion of the transformation.
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U2 - 10.1016/j.epsl.2012.11.022
DO - 10.1016/j.epsl.2012.11.022
M3 - Article
AN - SCOPUS:84871381814
SN - 0012-821X
VL - 361
SP - 44
EP - 49
JO - Earth and Planetary Science Letters
JF - Earth and Planetary Science Letters
ER -