Making Archean cratonic roots by lateral compression: A two-stage thickening and stabilization model

Archean tectonics was capable of producing virtually indestructible cratonic mantle lithosphere, but the dominant mechanism of this process remains a topic of considerable discussion. Recent geophysical and petrological studies have refuelled the debate by suggesting that thickening and associated v...

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Bibliographic Details
Published in:Tectonophysics 2018-10, Vol.746, p.562-571
Main Authors: Wang, Hongliang, van Hunen, Jeroen, Pearson, D. Graham
Format: Article
Language:English
Subjects:
Compression
Cooling
Craton formation
Craton stabilization
Cratons
Depletion
Geophysics
Gravitation
Gravitational collapse
Gravitational self-thickening
Lithosphere
Mantle
Mathematical models
Numerical experiments
Plate tectonics
Roots
Secular cooling
Stabilization
Tectonic shortening
Tectonics
Thickening
Vertical motion
Viability
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Summary:Archean tectonics was capable of producing virtually indestructible cratonic mantle lithosphere, but the dominant mechanism of this process remains a topic of considerable discussion. Recent geophysical and petrological studies have refuelled the debate by suggesting that thickening and associated vertical movement of the cratonic mantle lithosphere after its formation are essential ingredients of the cratonization process. Here we present a geodynamical study that focuses on how the thick stable cratonic lithospheric roots can be made in a thermally evolving mantle. Our numerical experiments explore the viability of a cratonization process in which depleted mantle lithosphere grows via lateral compression into a >200-km thick, stable cratonic root and on what timescales this may happen. Successful scenarios for craton formation, within the bounds of our models, are found to be composed of two stages: an initial phase of tectonic shortening and a later phase of gravitational self-thickening. The initial tectonic shortening of previously depleted mantle material is essential to initiate the cratonization process, while the subsequent gravitational self-thickening contributes to a second thickening phase that is comparable in magnitude to the initial tectonic phase. Our results show that a combination of intrinsic compositional buoyancy of the cratonic root, rapid cooling of the root after shortening, and the long-term secular cooling of the mantle prevents a Rayleigh-Taylor type collapse, and will stabilize the thick cratonic root for future preservation. This two-stage thickening model provides a geodynamically viable cratonization scenario that is consistent with petrological and geophysical constraints. [Display omitted] •We study the geodynamics of the cratonization process numerically.•Two stages occur: tectonic shortening and gravitational thickening.•Secular cooling plays a role in craton stabilization.•Results are consistent with petrological and geophysical constraints.
ISSN:0040-1951
1879-3266
DOI:10.1016/j.tecto.2016.12.001