Comment on “Channel flow, tectonic overpressure, and exhumation of high-pressure rocks in the Greater Himalayas” by Marques et al. (2018)
<p>The upward-tapering channel model proposed by Marques et al. (2018) for the Himalayas has a “base” that forms part of the subducting footwall and therefore does not close the channel. This configuration does not produce return flow, and no dynamic overpressure develops in the channel. The g...
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Solid Earth |
| Online Access: | https://www.solid-earth.net/10/357/2019/se-10-357-2019.pdf |
| Summary: | <p>The upward-tapering channel model proposed by Marques et
al. (2018) for the Himalayas has a “base” that forms part of the subducting
footwall and
therefore does not close the
channel. This configuration does not produce return flow, and no dynamic
overpressure develops in the channel. The geometrical and kinematic
configuration they actually use for their calculations differs from this and
is both geologically and mechanically improbable. In addition, the fixed
upper boundary condition in their models is mechanically unrealistic and
inconsistent with geological and geophysical constraints from the Himalayan
orogen. In reality, the dynamic pressures calculated from their model, which
exceed lithostatic pressure by as much as 1.5 GPa, would cause elastic
flexure or permanent deformation of the upper plate. I estimate that a
flexural upwarp of 50 km of the upper plate would be required to balance
forces, which would lead to geologically unrealistic topographic and gravity
anomalies. The magnitude of the dynamic overpressure that could be confined
is in fact limited by the shear strength of the upper plate in the Himalayas,
which is likely to be < 120 MPa.</p> |
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| ISSN: | 1869-9510 1869-9529 |