Ore deposits and lithosphere evolution in the early Earth

Plate tectonic processes, including subduction-related magmatism, rifting and collision are critical for the formation of many types of magmatic and hydrothermal ore deposits. Given the evidence for the existence of plate tectonic processes from as early as 3.9 Ga, the absence of significant mineral deposits older than about 3 Ga is attributed to either of a failure to survive, or the absence of another key ore-forming environment. Subcontinental Lithospheric Mantle (SCLM), which appeared between ca 3.6-3.0 Ga, provides the solution to understanding both of these issues. Pristine SCLM, formed as a residue of high temperature plume melting, is depleted (Fe-poor), buoyant, refractory, and has very high viscosity. These traits make for a durable lithosphere, a home for mineral deposits, in contrast to the easily removed (subducted, delaminated) dense oceanic lithospheric mantle. Integration of geological, geophysical and geochemical data from the crust and mantle, indicates that Archean SCLM underlies the majority of today's continental crust. Plate tectonics (forces, fluids, magmas) has resulted in metasomatism, fracturing, melting and suturing of the SCLM. These processes, along with the impact of mantle plumes and the rise of atmospheric oxygen, have provided the metals, energy and focus for ore systems in a range of associated crustal environments.