HR: 1340h
AN: MR43A-0982 [Abstracts]
TI: Rheology of Partially Molten Spinel Lherzolite at High Temperature
AU: * Wang, Y
EM: luckyyfwang1@sina.com
AF: State Key Laboratory of Geological Processes and Mineral Resources, China University of
Geosciences, Wuhan, 430074,
AU: Jin, Z
AF: State Key Laboratory of Geological Processes and Mineral Resources, China University of
Geosciences, Wuhan, 430074,
AU: Zhang, J
AF: State Key Laboratory of Geological Processes and Mineral Resources, China University of
Geosciences, Wuhan, 430074,
AU: Jin, S
AF: State Key Laboratory of Geological Processes and Mineral Resources, China University of
Geosciences, Wuhan, 430074,
AB:
Uniaxial creep experiments were performed on synthetic spinel lherzolite samples with grain sizes of 25-
50μm in a gas medium dead-load creep rig to investigate the deformation behavior of partially molten upper
mantle. The room pressure experiments were conducted at conditions of elevated temperatures of 1140-1200
°C and well-controlled oxygen fugacities of 10-6-10-10atm. Differential stresses of 4-74MPa were
applied to yield strain rates between 10-8 and 10-5 s-1. By fitting the steady-state creep strength
with empirical power law, we obtain an oxygen fugacity exponent of 0.05 ± 0.02, a stress exponent of 1.5
± 0.4, and an activation energy of 1428 ± 48 KJ/mol for the high-temperature deformation of a partially
molten spinel lherzolite. The oxygen fugacity exponent, m, is comparable to those obtained for deformation of
olivine single crystal, which suggests that deformation of pyroxene doesn't depend significantly on oxygen
fugacity as olivine. The creep activation energy obtained in this study is about twice of those from previous
studies. SEM observations show about 2-4% melt existing as melt pockets in triple junctions and melt films
between grain boundaries in deformed spinel lherzolite. The stress exponent of 1.5 suggests that both
dislocation creep and melt-enhanced diffusion creep contribute significantly to the deformation of lherzolite. Our
results provide constrains on the rheology and deformation microstructures of partially molten upper mantle.
DE: 3621 Mantle processes (1038)
DE: 3630 Experimental mineralogy and petrology
DE: 5112 Microstructure
DE: 5120 Plasticity, diffusion, and creep
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting