DOI: 10.1016/j.epsl.2018.03.027
Scopus记录号: 2-s2.0-85044944048
论文题名: Controls on the rheological properties of peridotite at a palaeosubduction interface: A transect across the base of the Oman–UAE ophiolite
作者: Ambrose T.K. ; Wallis D. ; Hansen L.N. ; Waters D.J. ; Searle M.P.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 491 起始页码: 193
结束页码: 206
语种: 英语
英文关键词: mantle wedge
; olivine microstructure
; Oman–UAE ophiolite
; phase mixing
; plate boundary
; strain localisation
Scopus关键词: Deformation
; Grain boundaries
; Grain size and shape
; Olivine
; Silicate minerals
; Viscosity
; Deformation conditions
; Deformation mechanism
; Mantle wedge
; Microstructural analysis
; Phase mixing
; Plate boundaries
; Strain localisation
; Subduction interface
; Grain growth
; deformation mechanism
; grain size
; mantle structure
; olivine
; ophiolite
; peridotite
; plate boundary
; rheology
; rock microstructure
; structural control
; subduction zone
; transect
; viscosity
; Oman
; Semail Ophiolite
; United Arab Emirates
; Indicator minor
英文摘要: Studies of experimentally deformed rocks and small-scale natural shear zones have demonstrated that volumetrically minor phases can control strain localisation by limiting grain growth and promoting grain-size sensitive deformation mechanisms. These small-scale studies are often used to infer a critical role for minor phases in the development of plate boundaries. However, the role of minor phases in strain localisation at an actual plate boundary remains to be tested by direct observation. In order to test the hypothesis that minor phases control strain localisation at plate boundaries, we conducted microstructural analyses of peridotite samples collected along a ∼1 km transect across the base of the Oman-United Arab Emirates (UAE) ophiolite. The base of the ophiolite is marked by the Semail thrust, which represents the now exhumed contact between subducted oceanic crust and the overlying mantle wedge. As such, the base of the ophiolite provides the opportunity to directly examine a former plate boundary. Our results demonstrate that the mean olivine grain size is inversely proportional to the abundance of minor phases (primarily orthopyroxene, as well as clinopyroxene, hornblende, and spinel), consistent with suppression of grain growth by grain-boundary pinning. Our results also reveal that mean olivine grain size is proportional to CPO strength (both of which generally decrease towards the metamorphic sole), suggesting that the fraction of strain produced by different deformation mechanisms varied spatially. Experimentally-derived flow laws indicate that under the inferred deformation conditions, the viscosity of olivine was grain-size sensitive. As such, grain size, and thereby the abundance of minor phases, influenced viscosity during subduction-related deformation along the base of the mantle wedge. We calculate an order of magnitude decrease in the viscosity of olivine towards the base of the ophiolite, which suggests strain was localised near the subduction interface. Our data indicate that this rheological weakening was primarily the result of more abundant minor phases near the base of the ophiolite. Our interpretations are consistent with those of previous studies on experimentally deformed rocks and smaller-scale natural shear zones that indicate minor phases can exert the primary control on strain localisation. However, our study demonstrates for the first time that minor phases can control strain localisation at the scales relevant to a major plate boundary. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/109918
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: University of Oxford, South Parks Road, Oxford, United Kingdom; Department of Earth Sciences, Utrecht University, Utrecht, CD 3584, Netherlands; University Museum of Natural History, Parks Rd, Oxford, OX1 3PW, United Kingdom; Department of Earth, Ocean and Atmospheric Sciences, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
Recommended Citation:
Ambrose T.K.,Wallis D.,Hansen L.N.,et al. Controls on the rheological properties of peridotite at a palaeosubduction interface: A transect across the base of the Oman–UAE ophiolite[J]. Earth and Planetary Science Letters,2018-01-01,491