Geochemical variations in Archean volcanic rocks, southwestern Greenland: Traces of diverse tectonic settings in the early Earth

Abstract

The primary driving force behind present-day structural, magmatic, sedimentary and metamorphic processes is plate tectonics, resulting from the fl ow of matter and energy between the lithosphere and mantle along divergent, convergent, and transform plate boundaries. Operation of plate tectonics and eruption of hot spot lavas from mantle plumes, stemming from the core-mantle boundary, appears to be coupled in that subducting oceanic plates pile up at the core-mantle boundary and then rise as buoyant plumes to feed hot spot volcanoes (see Hofmann, 1997; Burke, 2011). How far back in Earth history were these geological processes driven by plate tectonics? Were Archean geological processes dominated by density-driven, vertical crustal overturns and diapirs, without modern analogs? How did Archean continents grow? How did Archean oceanic crust form? Did Archean oceanic crust recycle into the mantle at subduction zones? These questions remain controversial. Excellent exposures and a prolonged geological record spanning 3.85‐2.5 Ga in the Archean craton of southwestern Greenland provide a unique opportunity to test hypotheses proposed for the early evolution of Earth. This craton consists mainly of Eoarchean to Neoarchean (ca. 3.8‐