DOI: 10.1016/j.epsl.2017.12.008
Scopus记录号: 2-s2.0-85039806931
论文题名: Transfer of subduction fluids into the deforming mantle wedge during nascent subduction: Evidence from trace elements and boron isotopes (Semail ophiolite, Oman)
作者: Prigent C. ; Guillot S. ; Agard P. ; Lemarchand D. ; Soret M. ; Ulrich M.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 484 起始页码: 213
结束页码: 228
语种: 英语
英文关键词: boron isotopes
; fluid migration processes
; mantle wedge
; metasomatism
; ophiolite
; subduction
Scopus关键词: Analytical geochemistry
; Boron
; Deformation
; Isotopes
; Shear flow
; Temperature
; Trace elements
; Boron isotopes
; Fluid migration
; Mantle wedge
; metasomatism
; ophiolite
; subduction
; Transport properties
; boron isotope
; fluid flow
; igneous geochemistry
; mantle structure
; metasomatism
; ophiolite
; partial melting
; petrology
; subduction
; trace element
; Oman
英文摘要: The basal part of the Semail ophiolitic mantle was (de)formed at relatively low temperature (LT) directly above the plate interface during “nascent subduction” (the prelude to ophiolite obduction). This subduction-related LT deformation was associated with progressive strain localization and cooling, resulting in the formation of porphyroclastic to ultramylonitic shear zones prior to serpentinization. Using petrological and geochemical analyses (trace elements and B isotopes), we show that these basal peridotites interacted with hydrous fluids percolating by porous flow during mylonitic deformation (from ∼850 down to 650 °C). This process resulted in 1) high-T amphibole crystallization, 2) striking enrichments of minerals in fluid mobile elements (FME; particularly B, Li and Cs with concentrations up to 400 times those of the depleted mantle) and 3) peridotites with an elevated δ11B of up to +25‰. These features indicate that the metasomatic hydrous fluids are most likely derived from the dehydration of subducting crustal amphibolitic materials (i.e., the present-day high-T sole). The rapid decrease in metasomatized peridotite δ11B with increasing distance to the contact with the HT sole (to depleted mantle isotopic values in <1 km) suggests an intense interaction between peridotites and rapid migrating fluids (∼1–25 m.y−1), erasing the initial high-δ11B subduction fluid signature within a short distance. The increase of peridotite δ11B with increasing deformation furthermore indicates that the flow of subduction fluids was progressively channelized in actively deforming shear zones parallel to the contact. Taken together, these results also suggest that the migration of subduction fluids/melts by porous flow through the subsolidus mantle wedge (i.e., above the plate interface at sub-arc depths) is unlikely to be an effective mechanism to transport slab-derived elements to the locus of partial melting in subduction zones. © 2017 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110071
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: Univ. Grenoble Alpes, Univ. Savoie Mont Blanc, CNRS, IRD, IFSTTAR, ISTerre, Grenoble, 38000, France; Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Institut des Sciences de la Terre de Paris (ISTeP), 4 place Jussieu, Paris, 75005, France; Laboratoire d'Hydrologie et de Géochimie de Strasbourg, EOST-CNRS-UMR 7517, Université de Strasbourg, France; Institut de Physique du Globe de Strasbourg, EOST-CNRS-UMR, Université de Strasbourg7516, France
Recommended Citation:
Prigent C.,Guillot S.,Agard P.,et al. Transfer of subduction fluids into the deforming mantle wedge during nascent subduction: Evidence from trace elements and boron isotopes (Semail ophiolite, Oman)[J]. Earth and Planetary Science Letters,2018-01-01,484