In this manuscript we review experimental constraints for the viscosity of the upper mantle. We first analyze experimental data to provide a critical review of flow law parameters for olivine aggregates and single crystals deformed in the diffusion creep and dislocation creep regimes under both wet and dry conditions. Using reasonable values for the physical state of the upper mantle, the viscosities predicted by extrapolation of the experimental flow laws compare well with independent estimates for the viscosity of the oceanic mantle, which is approximately 1019 Pa s at a depth of ~100 km. The viscosity of the mantle wedge of subduction zones could be even lower if the flux of water through it can result in olivine water contents greater than those estimated for the oceanic asthenosphere and promote the onset of melting. Calculations of the partitioning of water between hydrous melt and mantle peridotite suggest that the water content of the residue of arc melting is similar to that estimated for the asthenosphere. Thus, transport of water from the slab into the mantle wedge can continually replenish the water content of the upper mantle and facilitate the existence of a low viscosity asthenosphere.
|Original language||English (US)|
|Title of host publication||Inside the Subduction Factory, 2004|
|Publisher||Blackwell Publishing Ltd|
|Number of pages||23|
|State||Published - 2004|
|Name||Geophysical Monograph Series|
Bibliographical noteFunding Information:
Acknowledgments. We arc grateful to Ihe many colleagues with whom we have discussed the issues presented in this manuscript. In particular, we want to thank Shenghua Mei. Steve Mackwell, Mark Zimmerman, Peter Kelemen, Glenn Gaetani. Brian Evans, Magali Billen. Mike Braun. Laurent Montesi and Mathew Jull. We are also grateful for helpful reviews from Jed Mosenfelder and John Eiler. In addition, we want to thank Karen Hanghoj for assistance in preparing the manuscript. Finally, we would like to thank Sally Gregory Kohlstcdt and Ann Mulligan for patience during several week long get-togethers where the authors hashed over endless details on olivine rheology. This work was supported by OCE-0099316 (GH), EAR-9910899 (GH), EAR-9906986 (DLK). OCE-0002463 (DLK), EAR-0126277 (DLK) and INT-0123224 (DLK).
© 2003 by the American Geophysical Union.