SUPERCONTINENTS AND MINERAL DEPOSITS

It has been more than thirty years since workers such as Meyer and Hutchinson first emphasized that the age distributions of mineral deposits can serve as guides to the geologic history of Earth. Geochronological advances now allow for a more precise understanding of the distinctive temporal patterns of different mineral deposit types. Some age patterns (e.g., uranium, iron) mainly reflect shifts in global redox conditions. But many patterns for precious and base metal deposits show a broad association with periods of supercontinent amalgamation or break-up, and thus may serve as sensitive indicators of lithospheric evolution.

Gold-bearing vein and base metal-rich VMS deposits are related to convergent margin geodynamic processes during periods of supercontinent growth. Those, however, formed in the shallow crust (e.g., epithermal gold) have a low preservation potential and are poorly represented back through geologic time. Others, particularly orogenic gold, show a well-developed episodic pattern correlating with formation of Kenorland, Columbia, Gondwana, and Laurasia; changing styles of plate tectonics on a cooling planet help explain a lack of Rodinian gold. Processes of cratonization and related development of a thick subcontinental lithospheric mantle are only consistent with a Late Archean paleoplacer origin for the unique Witwatersrand gold ores, with a primary lode source on 3.0 Ga Ur. The large post-Triassic, circum-Pacific gold endowment is supportive of Condie's (2002) suggestion that Pangea break-up may overlap growth of a new supercontinent.

It is still controversial as to whether or not patterns of sedimentary rock-hosted ore deposits relate to supercontinent break-up or assembly. Most MVT Pb-Zn deposits are now widely accepted as forming in carbonate platforms, inboard of orogenic belts, during contractional events. However, Cu, Pb, and Zn deposits in clastic sedimentary rocks have formation ages that overlap both initiation of supercontinent dispersion when basins are intracratonic and supercontinent assembly when the basins are in a craton margin setting. Deposits related to intracratonic rifting that are products of plume-related alkalic (diamonds, IOCG) or mafic (PGE, Cr, Fe-Ti-V) magmatism appear to best record timing of the initiation of supercontinent fragmentation.