Wang, H.L. and van Hunen, J. and Pearson, D.G. and Allen, M.B. (2014) 'Craton stability and longevity : the roles of composition-dependent rheology and buoyancy.', Earth and planetary science letters., 391 . pp. 224-233.
Survival of thick cratonic roots in a vigorously convecting mantle system for billions of years has long been studied by the geodynamical community. High strength of the cratonic root is generally considered to be the most important factor, but the role of lithospheric mantle depletion and dehydration in this strengthening is still debated. Geodynamical models often argue for a significant strength or buoyancy contrast between cratonic and non-cratonic mantle lithosphere, induced by mantle depletion and dehydration. But recent laboratory experiments argue for only a modest effect of dehydration strengthening. Can we reconcile laboratory experiments and geodynamical models? We perform and discuss new numerical models to investigate craton stability and longevity with different composition-dependent rheology and buoyancy. Our results show that highly viscous and possibly buoyant cratonic root is essential to stabilise a geometry in which thick cratonic lithosphere and thinner non-cratonic lithosphere coexist for billions of years. Using non-Newtonian rheology, a modest strengthening factor of Δη=3 can protect compositionally buoyant cratonic roots from erosion by mantle convection for over billions of years. A larger strengthening factor (Δη=10) can maintain long term craton stability even with little or no intrinsic buoyancy. Such composition-dependent rheology is comparable to the laboratory experiments. This implies that a strict isopycnic state of cratonic lithosphere may not be necessary for the preservation of a cratonic root, provided a sufficient level of compositional strengthening is present.
|Keywords:||Craton stability, Composition-dependent rheology, Buoyancy, Non-Newtonian rheology, Dehydration strengthening.|
|Full text:||(AM) Accepted Manuscript|
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|Publisher Web site:||http://dx.doi.org/10.1016/j.epsl.2014.01.038|
|Publisher statement:||NOTICE: this is the author’s version of a work that was accepted for publication in Earth and Planetary Science Letters. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Earth and Planetary Science Letters, 391, 2014, 10.1016/j.epsl.2014.01.038.|
|Date accepted:||26 January 2014|
|Date deposited:||16 June 2014|
|Date of first online publication:||April 2014|
|Date first made open access:||No date available|
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