DOI: 10.1016/j.epsl.2021.117135
论文题名: Blueschist-facies paleo-earthquakes in a serpentinite channel (Zagros suture, Iran) enlighten seismogenesis in Mariana-type subduction margins
作者: Muñoz-Montecinos J. ; Angiboust S. ; Garcia-Casco A.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 573 语种: 英语
中文关键词: blueschists
; earthquakes
; Mariana-type margins
; paleo-earthquakes
; ultracataclasites
; Zagros suture
英文关键词: Earthquakes
; Faulting
; Feldspar
; Fluidization
; Gasoline
; Magnesia
; Petrology
; Trace elements
; Blueschists
; Mariana-type margin
; matrix
; Paleo-earthquake
; Pressure-temperature conditions
; Seismogenesis
; Serpentinite
; Subduction zones
; Ultracataclasite
; Zagros suture
; Magnesite
英文摘要: The architecture and pressure-temperature conditions reached by a Cretaceous block-in-matrix serpentinite mélange exposed in the Zagros suture resemble those imaged in the active Mariana subduction zone. There, large magnitude-earthquakes (M>w9) have never been recorded but smaller events – of poorly-constrained physical origin – in the range M∼w3-6 are widespread. Field and petro-structural constraints led to a first report of blueschist-facies seismic fault-related rocks in the Zagros serpentinite melange, including breccias, foliated cataclasites and ultracataclasites; all observed within a foliated mafic metatuffaceous block embedded in serpentinite schists. Fine-scale petrological characterization of ultrafine-grained, fluidized cataclastic material reveals the presence of newly-formed glaucophane, lawsonite, phengite, albite and pumpellyite, an assemblage inferred (based on thermodynamic modelling) to have crystallized in the lower lawsonite-blueschist facies at ∼0.6-1.0 GPa and 230-300 °C. Extensional veins containing similar mineral assemblages are observed crosscutting the aforementioned rocks but are also identified as comminuted fragments in all fault-related lithologies. Crosscutting relationships among the multiple generations of fluidized ultracataclasites and brecciated blueschists suggest that episodic faulting and hydrofracturing were contemporaneous processes at ∼20-35 km depth, i.e., at similar conditions as reported for metabasalts expelled by Mariana serpentinite mud volcanoes. Mechanical modelling confirms that the studied fault-related features can only have formed under nearly lithostatic pore fluid pressure conditions, maintaining the system in a critically unstable regime that promoted recurrent seismic faulting, as monitored in the Mariana seismogenic zone. These fluids are likely associated with externally and deeply-generated fluid pulses that may have reached the seismogenic window, imprinting a Ta-Th-Nb-HREEs-enriched trace element signature. This new faulted blueschist occurrence highlights the physical nature and the mechanical processes operating within fluid-saturated fault zones in the serpentinized subduction channel. © 2021 The Author(s) Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165612
Appears in Collections: 气候变化与战略
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作者单位: Université de Paris, Institut de physique du globe de Paris, CNRS, Paris, F-75005, France; Department of Mineralogy and Petrology, Faculty of Sciences, University of Granada, Campus Fuentenueva s/n, Granada, 18002, Spain; Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Armilla, Granada, 18100, Spain
Recommended Citation:
Muñoz-Montecinos J.,Angiboust S.,Garcia-Casco A.. Blueschist-facies paleo-earthquakes in a serpentinite channel (Zagros suture, Iran) enlighten seismogenesis in Mariana-type subduction margins[J]. Earth and Planetary Science Letters,2021-01-01,573