Speculations on the formation of cratons and cratonic basins

McKenzie, D. P. and Priestley, K. F. (2015) Speculations on the formation of cratons and cratonic basins. Earth and Planetary Science Letters, 435. pp. 94-104. ISSN 0012-821X DOI 10.1016/j.epsl.2015.12.010

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Abstract

Surface wave tomography using Rayleigh waves has shown that Tibet and the surrounding mountain ranges that are now being shortened are underlain by thick lithosphere, of simi- lar thickness to that beneath cratons. Both their elevation and lithospheric thickness can result from pure shear shortening of normal thickness continental lithosphere by about a factor of two. The resulting thermal evolution of the crust and lithosphere is dominated by radioactive decay in the crust. It raises the temperature of the lower part of the crust and of the upper part of the lithosphere to above their solidus temperatures, generating granites and small volumes of mafic alkaline rocks from beneath the Moho, as well as generating high temperature metamorphic assemblages in the crust. Thermal models of this process show that it can match the P, T estimates determined from metamorphic xenoliths from Tibet and the Pamirs, and can also match the compositions of the alkaline rocks. The seismological properties of the upper part of the lithosphere beneath northern Tibet suggest that is has already been heated by the blanketing effect and radioactivity of the thick crust on top. If the crustal thickness is reduced by erosion alone to its normal value at low elevations, without any tectonic extension, over a time scale that is short compared to the thermal time constant of thick lithosphere, of ∼ 250 Ma, thermal subsidence will produce a basin underlain by thick lithosphere. Though this simple model accounts for the relevant observations, there is not yet sufficient information available to be able to model in detail the resulting thermal evolution of the sediments deposited in such cratonic basins.

Item Type:	Article
Uncontrolled Keywords:	2015AREP; IA69; weekly list
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics 08 - Green Open Access
Journal or Publication Title:	Earth and Planetary Science Letters
Volume:	435
Page Range:	pp. 94-104
Identification Number:	10.1016/j.epsl.2015.12.010
Depositing User:	Sarah Humbert
Date Deposited:	22 Dec 2015 16:42
Last Modified:	01 Feb 2017 01:00
URI:	http://eprints.esc.cam.ac.uk/id/eprint/3511

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