Buoyancy rather than rheology controls the thickness of the overriding mechanical lithosphere at subduction zones

Citation
A. Rowland et Jh. Davies, Buoyancy rather than rheology controls the thickness of the overriding mechanical lithosphere at subduction zones, GEOPHYS R L, 26(19), 1999, pp. 3037-3040
Citations number
23
Categorie Soggetti
Earth Sciences
Journal title
GEOPHYSICAL RESEARCH LETTERS
ISSN journal
00948276 → ACNP
Volume
26
Issue
19
Year of publication
1999
Pages
3037 - 3040
Database
ISI
SICI code
0094-8276(19991001)26:19<3037:BRTRCT>2.0.ZU;2-#
Abstract
The thickness of Earth's mechanical lithosphere is poorly defined. To inves tigate whether rheology controls the thickness of the overriding plate's me chanical lithosphere in subduction zones, the thermal structure was modelle d numerically assuming a temperature dependent mantle viscosity. It was fou nd that the overriding lithosphere was ablated such that very high temperat ures reached close to the surface near the apex of the wedge corner, leadin g to unrealistically high heat flow. Since temperature dependent rheology c learly does not control the thickness of the mechanical lithosphere, we sug gest that it is instead controlled by buoyancy. The source of buoyancy we a ssume is compositional, e.g, buoyant crust. Two end-member models with crus tal thickness of 10 and 70 km respectively were then undertaken, these had lower heat flow. This work supports the assumption of some earlier workers (e.g. Plank and Langmuir, 1988) who equated the mechanical lithosphere with the crust of the overriding plate.