Measurement of Activation Volume for Creep of Dry Olivine at Upper-Mantle Conditions
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Apple Inc., Cupertino CA (United States)
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Olivine is the most abundant and among the weakest phases in Earth's upper mantle, and thus, its rheological properties play a critical role in governing thermal structure and convective flow in the upper mantle. A persistent obstacle to constraining the in situ flow properties of olivine by laboratory experiment has been the difficulty in resolving the effect of pressure, which is weak within the 0- to ~2-GPa pressure range of conventional laboratory deformation instruments but potentially strong over the 1- to ~14-GPa range of the upper mantle. Using a deformation-DIA, one of a new generation of bonafide deformation devices designed for operation to ≥10 GPa, we have deformed dry, polycrystalline San Carlos olivine in high-temperature creep with the singular intent of providing the best achievable measurement of activation volume V* and a comprehensive statement of uncertainty. Under strictly dry conditions, at constant temperature (1,373 K) and strain rate (1 × 10-5 s-1), varying only pressure (1.8 to 8.8 GPa), we measure V* = 15 ± 5 cm3/mol. We have reproduced the well-known mechanism change from [100]-slip to [001]-slip near 5 GPa and determined that, whatever the change in V* associated with the change in slip system, the effective value of 15 ± 5 cm3/mol is still accurate for modeling purposes in the 2- to 9-GPa pressure range. This is a substantial pressure effect, which in the absence of a temperature gradient would represent a viscosity increase from the top to bottom of the upper mantle of 5 ± 2 orders of magnitude.
- Research Organization:
- Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- Grant/Contract Number:
- FG02-07ER15839
- OSTI ID:
- 1609770
- Alternate ID(s):
- OSTI ID: 1476971
- Journal Information:
- Journal of Geophysical Research. Solid Earth, Vol. 123, Issue 10; ISSN 2169-9313
- Publisher:
- American Geophysical UnionCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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journal | December 2019 |
Low‐Temperature Plasticity in Olivine: Grain Size, Strain Hardening, and the Strength of the Lithosphere
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journal | June 2019 |
The Thermal State and Interior Structure of Mars
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journal | November 2018 |
Low-Temperature Plasticity in Olivine: Grain Size, Strain Hardening, and the Strength of the Lithosphere
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text | January 2019 |
The thermal state and interior structure of Mars
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text | January 2018 |
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