Drainage of subduction interface fluids into the forearc mantle evidenced by a pristine jadeitite network (Polar Urals)
Metadatos
Mostrar el registro completo del ítemAutor
Angiboust, Samuel; Glodny, Johannes; Cambeses Torres, Aitor; Raimondo, Tom; Monié, Patrick; Popov, Michael; García Casco, AntonioEditorial
Wiley Online Library
Materia
fluids jadeite mantle wedge
Fecha
2020-09-13Referencia bibliográfica
Angiboust, S. et. al. J. Metamorph. Geol. 2021;39:473–500. [https://doi.org/10.1111/jmg.12570]
Patrocinador
IdEx ANR-18- IDEX-0001; State budget topic IGG UB RAS AAAA-A18-118052590032-6Resumen
The physical and mechanical processes rooted in the hydrated, serpentinized mantle
above subduction zones remain insufficiently explored despite fundamental implications
for our understanding of rheology and fluid recycling along subduction
interfaces. Through a field-based investigation, serpentinized peridotites and jadeitite
samples from a fossil forearc mantle in the Polar Urals (Russia) are studied
here to document fluid–rock interaction processes in the high-P field, as well as
the long-term evolution of the base of the mantle wedge. Petrographic, geochemical
and microstructural observations reveal a complex, protracted evolution of the
jadeitite-forming fluid pathway throughout the gradual cooling of the forearc mantle
and increasing serpentinization of the host. It is shown that the jadeitite lenses in the
studied locality (a) derive for a large part from a trondhjemitic dyke earlier emplaced
in a warm subduction environment, and (b) record the cooling of the subduction
hangingwall under high-P conditions associated with increasing host serpentinization.
In the studied locality, the majority of the jadeitites formed at relatively high
temperatures (>600°C) by the influx of Na–Al-rich, slab-derived metamorphic fluids
that were drained along the base of the mantle wedge, parallel to the subduction interface.
Changes in bulk-rock geochemical signatures and in paragenetic sequences
also constrain the compositional evolution of the fluid channelized along this drainage,
with an increasing sedimentary component. The phlogopite-bearing walls of
the dyke exhibit Rb–Sr and Ar–Ar ages ranging between c. 405 and c. 390 Ma, a
range partly overlapping within uncertainty with the previously dated zircons from
the jadeitite core (410–400 Ma; U–Pb). This study opens a unique window on the
pristine structures formed above the plate interface by melting and fluid–rock interaction
in the early subduction stages, as well as their evolution during secular cooling
of the base of the mantle wedge.