TY - GEN
T1 - Centrifuge Experiments of the Initiation of Self-Sustaining Subduction
AU - Mart, Yossi
AU - Goren, Liran
AU - Aharonov, Einat
PY - 2021/4/26
Y1 - 2021/4/26
N2 - The post-Triassic age of all oceanic lithospheres indicates the
efficiency and the sustainability of lithospheric subduction, which
consumes the basaltic seafloor and recirculates it in the upper mantle.
Since at present the initiation of subduction is very rare,
comprehension of this cardinal process should be carried through
modeling - numeric or analog. While deciphering processes through
numeric modeling is commonly comprehensive, the analog models can
determine major factor that constrain a tectonic procedure. Analog
centrifuge experiments were applied to initiate self-sustained modelled
subduction, trying to determine the critical factors that trigger its
early stages.Analytically we presumed that where densities of two
lithospheric plates, juxtaposed across a weakness zone, exceed a
critical value, then the denser lithosphere eventually will drive
underneath the lighter one, provided the friction across the interface
is not too high. Consequently, analog experiments were carried out in a
centrifuge at acceleration of ca. 1000 g., deforming miniaturized models
of three layers representing the asthenosphere, the ductile and the
brittle lithosphere. The lithospheres were modeled to include lighter
and denser components, juxtaposed along a slightly lubricated contact
plane, where the density difference between these components was ca. 200
kg/m3. No mechanism of lateral force was applied in the experiment (even
though such a vector exists in nature due to the seafloor spreading at
the oceanic ridges), to test the possibility of subduction in domains
where such a force is minor or non-existent.The analog experiments
showed that the penetration of the denser modeled lithosphere under the
lighter one led to extension and subsequent break-up of the over-riding
plate. That break-up generated seawards trench rollback, normal
faulting, rifting, and formed proto-back-arc basins. Lateral
differential reduction of the friction between the juxtaposed plates led
to the development of arcuate subduction zones. The experimental
miniaturization, and subsequent numerical and analytical modeling,
suggest that the observed deformation in the analog models could be
meaningful to the planet as well.Constraints of the analog
experimentation setting did not enable the modeling of the subduction
beyond the initial stages, but there is ground to presume that at depths
of 40-50 km, metamorphic processes of the generation of eclogites would
change the initial mineralogy on the subducting plate. Reactions with
water would convert basalts into metamorphic serpentinites and schists.
Higher temperatures and pressures would melt parts of the subducted slab
to generate felsic magmas, which would ascend towards the surface
diapirically due to their lighter density. Alternately, low availability
of H2O would gradually alter the oceanic basalt and gabbro into
eclogite, which would sink into the mantle due to its increased density.
AB - The post-Triassic age of all oceanic lithospheres indicates the
efficiency and the sustainability of lithospheric subduction, which
consumes the basaltic seafloor and recirculates it in the upper mantle.
Since at present the initiation of subduction is very rare,
comprehension of this cardinal process should be carried through
modeling - numeric or analog. While deciphering processes through
numeric modeling is commonly comprehensive, the analog models can
determine major factor that constrain a tectonic procedure. Analog
centrifuge experiments were applied to initiate self-sustained modelled
subduction, trying to determine the critical factors that trigger its
early stages.Analytically we presumed that where densities of two
lithospheric plates, juxtaposed across a weakness zone, exceed a
critical value, then the denser lithosphere eventually will drive
underneath the lighter one, provided the friction across the interface
is not too high. Consequently, analog experiments were carried out in a
centrifuge at acceleration of ca. 1000 g., deforming miniaturized models
of three layers representing the asthenosphere, the ductile and the
brittle lithosphere. The lithospheres were modeled to include lighter
and denser components, juxtaposed along a slightly lubricated contact
plane, where the density difference between these components was ca. 200
kg/m3. No mechanism of lateral force was applied in the experiment (even
though such a vector exists in nature due to the seafloor spreading at
the oceanic ridges), to test the possibility of subduction in domains
where such a force is minor or non-existent.The analog experiments
showed that the penetration of the denser modeled lithosphere under the
lighter one led to extension and subsequent break-up of the over-riding
plate. That break-up generated seawards trench rollback, normal
faulting, rifting, and formed proto-back-arc basins. Lateral
differential reduction of the friction between the juxtaposed plates led
to the development of arcuate subduction zones. The experimental
miniaturization, and subsequent numerical and analytical modeling,
suggest that the observed deformation in the analog models could be
meaningful to the planet as well.Constraints of the analog
experimentation setting did not enable the modeling of the subduction
beyond the initial stages, but there is ground to presume that at depths
of 40-50 km, metamorphic processes of the generation of eclogites would
change the initial mineralogy on the subducting plate. Reactions with
water would convert basalts into metamorphic serpentinites and schists.
Higher temperatures and pressures would melt parts of the subducted slab
to generate felsic magmas, which would ascend towards the surface
diapirically due to their lighter density. Alternately, low availability
of H2O would gradually alter the oceanic basalt and gabbro into
eclogite, which would sink into the mantle due to its increased density.
U2 - 10.5194/egusphere-egu21-433
DO - 10.5194/egusphere-egu21-433
M3 - Conference contribution
VL - 23
T3 - vEGU21, the 23rd EGU General Assembly, held online 19-30 April, 2021
SP - 1
EP - 1
BT - EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4822
ER -