期刊
GEOPHYSICAL RESEARCH LETTERS
卷 49, 期 16, 页码 -出版社
AMER GEOPHYSICAL UNION
DOI: 10.1029/2022GL098945
关键词
antigorite serpentine; plate boundary; deformation mechanisms; rheology
资金
- European Union [715836]
- Japan Society for the Promotion of Science [JP16H06476, 20KK0078, 21H052303]
This study reveals the deformation mechanisms and rheological behavior of antigorite, suggesting that dissolution-precipitation creep and dislocation activity contribute to the foliation development of antigorite.
Antigorite serpentinite is expected to occur in parts of subduction plate boundaries, and may suppress earthquake slip, but the dominant deformation mechanisms and resultant rheology of antigorite are unclear. An exhumed plate boundary shear zone exposed near Nagasaki, Japan, contains antigorite deformed at 474 degrees C +/- 30 degrees C. Observations indicate that a foliation defined by (001) crystal facets developed during plate-boundary shear. Microstructures indicating grain-scale dissolution at high-stress interfaces and precipitation in low-stress regions suggest that dissolution-precipitation creep contributed to foliation development. Analysis of crystal orientations indicate a small contribution from dislocation activity. We suggest a frictional-viscous rheology for antigorite, where dissolution-precipitation produces a foliation defined by (001) crystal facets and acts to resolve strain incompatibilities, allowing for efficient face-to-face sliding between facets. This rheology can not only explain aseismic behavior at ambient plate boundary conditions, but also some of the contrasting behaviors shown by previous field and laboratory studies.
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