SEMINAR: CWR Presents:

Subduction processes, critical for the formation of many magmatic and hydrothermal ore deposits, appear to have been active since about 3.9Ga.

However, the environment to preserve such deposits did not exist until the emergence of the Sub-Continental Lithospheric Mantle (SCLM) between 3.5-3.0Ga. As a residue of high temperature plume melting, pristine SCLM is depleted (Fe-poor), buoyant, refractory and has very high viscosity. Mapping of both crust and mantle, supported by Hf-isotopic studies, indicates that Archean SCLM underlies the majority of continental crust.

The physical properties, architecture, and metasomatic history (linked to prior subduction) of the SCLM has had a profound influence on the location, style and preservation potential of many ore deposit types. Fragmentation of SCLM provided backarc and pericratonic basins that are the setting for many magmatic and hydrothermal deposit types. Translithospheric faults became conduits and hosts for magmas and ore fluids.

Stable continental shelves emerged to host giant bedded deposits, and the mobility of metals in continental sediments gave rise to new styles of ore deposits. The arrival of the SCLM resulted in a proliferation of potential ore deposit settings, and provided a means to preserve mineral deposits beyond the next tectonic accident.