DOI: 10.1016/j.epsl.2018.01.029
Scopus记录号: 2-s2.0-85044778366
论文题名: Brittle deformation during Alpine basal accretion and the origin of seismicity nests above the subduction interface
作者: Menant A. ; Angiboust S. ; Monié P. ; Oncken O. ; Guigner J.-M.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2018
卷: 487 起始页码: 84
结束页码: 93
语种: 英语
英文关键词: Alps
; fluids
; paleoseismicity
; pseudotachylytes
; subduction
; Valpelline
Scopus关键词: Crystal structure
; Feldspar
; Fluids
; Mica
; Plates (structural components)
; Seismology
; Tectonics
; Alps
; Paleoseismicity
; Pseudotachylytes
; subduction
; Valpelline
; Deformation
; brittle deformation
; gneiss
; granulite facies
; paleoseismicity
; subduction zone
; Alps
英文摘要: Geophysical observations on active subduction zones have evidenced high seismicity clusters at 20–40 km depth in the fore-arc region whose origin remains controversial. We report here field observations of pervasive pseudotachylyte networks (interpreted as evidence for paleo-seismicity) in the now-exhumed Valpelline continental unit (Dent Blanche complex, NW. Alps, Italy), a tectonic sliver accreted to the upper plate at c. 30 km depth during the Paleocene Alpine subduction. Pre-alpine granulite-facies paragneiss from the core of the Valpelline unit are crosscut by widespread, mm to cm-thick pseudotachylyte veins. Co-seismic heating and subsequent cooling led to the formation of Ti-rich garnet rims, ilmenite needles, Ca-rich plagioclase, biotite microliths and hercynite micro-crystals. 39Ar–40Ar dating yields a 51–54 Ma age range for these veins, thus suggesting that frictional melting events occurred near peak burial conditions while the Valpelline unit was already inserted inside the duplex structure. In contrast, the base of the Valpelline unit underwent synchronous ductile and brittle, seismic deformation under water-bearing conditions followed by a re-equilibration at c. 40 Ma (39Ar–40Ar on retrograded pseudotachylyte veins) during exhumation-related deformation. Calculated rheological profiles suggest that pseudotachylyte veins from the dry core of the granulite unit record upper plate micro-seismicity (Mw 2–3) formed under very high differential stresses (>500 MPa) while the sheared base of the unit underwent repeated brittle–ductile deformation at much lower differential stresses (<40 MPa) in a fluid-saturated environment. These results demonstrate that some of the seismicity clusters nested along and above the plate interface may reflect the presence of stiff tectonic slivers rheologically analogous to the Valpelline unit acting as repeatedly breaking asperities in the basal accretion region of active subduction zones. © 2018 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/110010
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: Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ. Paris Diderot, CNRS, Paris, F-75005, France; Géosciences Montpellier UMR-CNRS 5243, Place E. Bataillon, Montpellier, 34090, France; GFZ German Research Center for Geosciences, Potsdam, D-14473, Germany; Sorbonne Universités, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, Paris, 75005, France
Recommended Citation:
Menant A.,Angiboust S.,Monié P.,et al. Brittle deformation during Alpine basal accretion and the origin of seismicity nests above the subduction interface[J]. Earth and Planetary Science Letters,2018-01-01,487