DOI: 10.1016/j.epsl.2018.08.039
Scopus记录号: 2-s2.0-85052757260
论文题名: An experimental study of grain-scale microstructure evolution during the olivine–wadsleyite phase transition under nominally “dry” conditions
作者: Mohiuddin A. ; Karato S.-I.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 501 起始页码: 128
结束页码: 137
语种: 英语
英文关键词: grain-size
; microstructural evolution
; olivine–wadsleyite
; phase transformation
; rheology
; subducting slabs
Scopus关键词: Crystalline materials
; Grain boundaries
; Grain growth
; Grain size and shape
; Growth kinetics
; Growth rate
; High pressure engineering
; Nucleation
; Olivine
; Phase transitions
; Rheology
; Silicate minerals
; Volume fraction
; Equilibrium boundaries
; Grain size
; Interconnected network
; Micro-structure evolutions
; Multi-anvil high-pressure apparatus
; Subducting slabs
; Temperature sensitivity
; Wadsleyite
; Microstructural evolution
; experimental study
; grain boundary
; grain size
; microstructure
; olivine
; phase transition
; rheology
; slab
; subduction
; wadsleyite
英文摘要: The grain-scale microstructure evolution during the phase transformation of olivine to wadsleyite was investigated using a multi-anvil high-pressure apparatus. We identified three stages in the microstructure evolution during olivine to wadsleyite phase transformation: (1) nucleation of wadsleyite along potential nucleation sites (e.g., grain boundaries (and grain corners), inside of grains (dislocations, stacking faults)), (2) development of an interconnected network of fine-grained wadsleyite along grain boundaries (3) growth of wadsleyite into olivine. Our observations suggest that at low over pressures (<3 GPa), phase transformation takes place mainly via inter-crystalline mechanism. As the over-pressure increases (>3 GPa), intra-crystalline nucleation makes a significant contribution to the volume fraction transformed. The rheological properties of a sample undergoing the phase transformation are controlled by the grain-size and the connectivity of newly formed grains. Based on the model of grain-size evolution involving both nucleation and growth, we show that the initial grain-size of wadsleyite is controlled by the competition between nucleation rate and growth rate when phase transformation takes place near the equilibrium boundary (at relatively higher temperatures, >1200 K) but mostly by critical size for nucleation when phase transformation takes place away from the equilibrium boundary (at relatively low temperatures, <1200 K). After the newly formed grains cover the potential sites for nucleation (“site-saturation”), grain-size is governed by grain-growth till ∼50% volume fraction is transformed. Due to the temperature sensitivity of initial size and of the grain-growth rate, the size of newly formed grains in subducting slabs is highly sensitive to the temperature at which the phase transformation occurs. At low temperatures, the size of new grains is small due to small initial grain-size and sluggish grain-growth. In contrast, grain-size during phase transformation is large at high temperatures due to the large initial grain-size and subsequent fast grain-growth kinetics. Consequently, substantial reduction of slab strength is expected in the cold regions of a subducting slab but not in the warm regions. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109676
Appears in Collections: 影响、适应和脆弱性 气候变化事实与影响
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作者单位: Department of Geology and Geophysics, Yale University, New Haven, CT, United States
Recommended Citation:
Mohiuddin A.,Karato S.-I.. An experimental study of grain-scale microstructure evolution during the olivine–wadsleyite phase transition under nominally “dry” conditions[J]. Earth and Planetary Science Letters,2018-01-01,501