@misc{10481/62668,
year = {2020},
month = {3},
url = {http://hdl.handle.net/10481/62668},
abstract = {High pressure–low temperature metamorphic
rocks from the late Paleozoic accretionary wedge
exposed in central Chile (Pichilemu region) are
characterized by a greenschist-blueschist lithological association with interbedded metasediments
that reached peak burial conditions of ~400 °C
and 0.8 GPa during late Carboniferous times. We
herein combine new extensive field observations,
structural measurements, and geochemical and
petrological data on vein and matrix material from
Pichilemu transitional greenschist-blueschist facies
rocks. The studied veins were first filled by albite, followed by quartz and calcite as well as glaucophane
and winchite. Field, structural, and microscopic
zoning patterns show that these rocks underwent
a protracted sequence of prograde vein-opening
events, which have been largely transposed to the
main foliation before and during underplating in
the basal accretion site near 25–30 km depth. While
some of the earliest albite-filled vein sets may have
formed after prograde breakdown of sub–greenschist facies minerals (<250 °C), our thermodynamic
modeling shows that relatively minor amounts of
fluid are produced in the subducted pile by dehydration reactions between 250 and 400 °C along
the estimated geothermal gradient. It also confirms
that the formation of interlayered blueschist and
greenschist layers in Pichilemu metavolcanics is a
consequence of local bulk composition variations,
and that greenschists are generally not formed due
to selective exhumation-related retrogression of
blueschists. The early vein sets are a consequence
of prograde internal fluid production followed by
sets of hydrofractures formed at near-peak burial
that are interpreted as a record of external fluid
influx. We postulate that such a fractured sequence
represents a close analogue to the high-Vp/Vs
regions documented by seismological studies
within the base of the seismogenic zone in active
subduction settings.},
organization = {This work has been funded by an
Initiative D’EXcellence (IDEX) grant 16C538 to S.A. The University of Granada is acknowledged for partial funding. Part of this
work was also supported by the TelluS Program of CNRS/INSU.
This is Institut de Physique du Globe de Paris contribution 4124.},
publisher = {Geological Society of America},
title = {Multiple veining in a paleo–accretionary wedge: The metamorphic rock record of prograde dehydration and transient high porefluid pressures along the subduction interface (Western Series, central Chile)},
doi = {10.1130/GES02227.1},
author = {Muñoz Montecinos, Jesús and Cambeses Torres, Aitor and García Casco, Antonio},
}