Exhumation Process in Oceanic and Continental Subduction Context: A Review
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Date
2009
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Abstract
Although the exhumation of high pressure (HP) and ultrahigh pressure
(UHP) rocks is an integral process in subduction, it is a transient process, likely
taking place during the perturbation in subduction zones. Exhumation of HP to
UHP rocks requires the weakening of a subduction channel and the decoupling of
the exhumed slice from the rest of the slab. Considering more than 60 occurrences of
HP to UHP units of Phanerozic ages, we propose three major types of subduction
zones:
Accretionary-type subduction zones exhume HP metasedimentary rocks by underplating.
The exhumation is slow and can be long-lasting.
The serpentinite-type subduction zones exhume HP to UHP in a 1 to 10 km thick
serpentinite subduction channel. The serpentinite matrix originates from both
subducted abyssal peridotites and hydated mantle wedge. Exhumation velocity is low
to intermediate and the exhumation is driven by the buoyancy and the low-viscosity
of the serpentinite.
The continental-type subductions exhume UHP rocks of continental origin. The
UHP rocks together with garnet-bearing peridotites form units from km-scale unit.
The exhumation is fast, short-lived and occurs at the transition from oceanic subduction
to continental subduction. It is driven by buoyancy forces and asthenospheric
return flow.
Description
Keywords
Oceanic subduction, Continental subduction, Exhumation, HP to UHP rocks, Subduction channel
Citation
Subduction Zone Geodynamics. Part V: Continental and Ridge Subduction Processes (pp. 175-205)