气候变化领域集成服务门户(CCPortal): Rheological Weakening of Olivine + Orthopyroxene Aggregates Due to Phase Mixing: Effects of Orthopyroxene Volume Fraction

CCPortal

DOI	10.1029/2020JB019888
	Rheological Weakening of Olivine + Orthopyroxene Aggregates Due to Phase Mixing: Effects of Orthopyroxene Volume Fraction
	Tasaka M.; Zimmerman M.E.; Kohlstedt D.L.
发表日期	2020
ISSN	21699313
卷号	125 期号:9
英文摘要	To understand the effects of secondary minerals on changes in the mechanical properties of upper mantle rocks due to phase mixing, we conducted high-strain torsion experiments on aggregates of iron-rich olivine + orthopyroxene (opx) with opx volume fractions of fopx = 0.15, 0.26, and 0.35. For samples with larger amounts of opx, fopx = 0.26 and 0.35, the value of the stress exponent decreases with increasing strain from n ≈ 3 for γ ≲ 5 to n ≈ 2 for 5 ≲ γ ≲ 25, indicating that the deformation mechanism changes as strain increases. In contrast, for samples with fopx = 0.15, the stress exponent is constant at n ≈ 3.3 for 1 ≲ γ ≲ 25, suggesting that no change in deformation mechanism occurs with increasing strain for samples with smaller amounts of opx. The microstructures of samples with larger amounts of opx provide insight into the change in deformation mechanism derived from the mechanical data. Elongated grains align subparallel to the shear direction for samples of all three compositions deformed to lower strains. However, strain weakening with grain size reduction and the formation of a thoroughly mixed, fine-grained texture only develops in samples with fopx = 0.26 and 0.35 deformed to higher strains of γ ≳ 16. These mechanical and associated microstructural properties imply that rheological weakening due to phase mixing only occurs in the samples with larger fopx, which is an important constraint for understanding strain localization in the upper mantle of Earth. ©2020. American Geophysical Union. All Rights Reserved.
英文关键词	deformation; olivine; orthopyroxene; phase mixing; rheological weakening
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187617
作者单位	Department of Earth Science, University of Minnesota, Twin Cities, Minneapolis, MN, United States; Now at Department of Geoscience, Shizuoka University, Shizuoka, Japan
推荐引用方式 GB/T 7714	Tasaka M.,Zimmerman M.E.,Kohlstedt D.L.. Rheological Weakening of Olivine + Orthopyroxene Aggregates Due to Phase Mixing: Effects of Orthopyroxene Volume Fraction[J],2020,125(9).
APA	Tasaka M.,Zimmerman M.E.,&Kohlstedt D.L..(2020).Rheological Weakening of Olivine + Orthopyroxene Aggregates Due to Phase Mixing: Effects of Orthopyroxene Volume Fraction.Journal of Geophysical Research: Solid Earth,125(9).
MLA	Tasaka M.,et al."Rheological Weakening of Olivine + Orthopyroxene Aggregates Due to Phase Mixing: Effects of Orthopyroxene Volume Fraction".Journal of Geophysical Research: Solid Earth 125.9(2020).