Mantle Plumes in the Archean

Abstract

Introduction There is considerable interest in the role that mantle plumes may have played in Archean (≥2.5 Ga) magma production, crustal underplating, production of oceanic plateaus, and in cooling of the mantle (Abbott 1996; Tomlinson and Condie 2001). Mantle temperatures must have been higher in the Archean, and hence the sinking of buoyant oceanic lithosphere into the mantle can account for only a small fraction of Archean heat loss (Bickle 1986; Davies 1992). Although plumes today account for no more than about 10% of the Earth's heat loss, the question of whether plumes were more important in cooling the mantle during the Archean is an important unknown in terrestrial thermal history (Davies 1993). If plumes were more important in the early stages of Earth history, as suggested by Fyfe (1978), perhaps the Archean Earth was more like Venus is today. In this chapter we will review methods that have been used to identify Archean mantle plumes by using igneous rocks derived from plume sources and discuss the results in terms of mantle evolution. Tracking Plumes into the Archean with Greenstones Overview How do we evaluate the role of mantle plumes in the early history of Earth? Three general approaches to this question are well established. First, it is well known that rock associations in oceanic plateaus and flood basalts differ from those in oceanic crust, oceanic islands, and arc systems (Condie 1997a; Kerr et al. 2000).