Thickness and thermal history of continental crust and root zones |
| |
| Authors: | Geoffrey F Davies |
| |
| Institution: | 1. Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130 U.S.A.;2. McDonnell Center for Space Sciences, Washington University, St. Louis, MO 63130 U.S.A. |
| |
| Abstract: | The survival to the present of the Archean nuclei of Precambrian shields requires special explanation if, as seems likely, the rate of heat flow out of the earth was two or three times greater in the late Archean (2.5 b.y. ago) than at present, since such a high heat flux would have melted the base of the Archean crust. It is proposed that there must have existed beneath stable continental crust a root zone (or lithosphere, or tectosphere) at least 200 km thick which has acted as a thermal buffer between the crust and the convecting mantle; this is virtually the same model as has been proposed to explain the present distribution of heat flow between continents and oceans. The strong temperature dependence of silicate rheology insures that the mantle temperature at the base of the root zone was no more than about 150°C higher in the late Archean than at present; the greater Archean heat flux would have been removed mainly through faster sea-floor spreading. To have survived, the root zone must be mechanically and chemically distinct from the rest of the mantle, and its formation was probably intimately related to the differentiation and stabilization of the continental crust. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
