Cooling of the earth in the Archaean: Consequences of pressure-release melting in a hotter mantle

N. J. Vlaar*, P. E. van Keken, A. P. van den Berg

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

A model is presented to describe the cooling of the Earth in the Archaean. At the higher Archaean mantle temperatures pressure-release melting starts deeper and generates a thicker basaltic or komatiitic crust and depleted harzburgite layer compared with the present-day situation. Intrinsic compositional stability and lack of mechanical coherency renders the mechanism of plate tectonics ineffective. It is proposed that the Archaean continents stabilised early on top of a compositionally stratified root. In the Archaean oceanic lithosphere, hydrated upper crust can founder and recycle through its high-pressure phase eclogite. Eclogite remelting and new pressure-release melting generates new crustal material. Migration of magma and latent heat release by solidification at the surface provides an efficient mechanism to cool the mantle by several hundreds of degrees during the Archaean. This can satisfactorily explain the occurrence of high extrusion temperature komatiites and lower extrusion temperature basalts in greenstone belts as being derived from the same source by different mechanisms.

Original languageEnglish
Pages (from-to)1-18
JournalEarth and Planetary Science Letters
Volume121
Issue number1-2
DOIs
Publication statusPublished - Jan 1994

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