EPISODIC PRODUCTION OF CONTINENTAL CRUST AND THE TEMPORAL DISTRIBUTION OF MINERAL DEPOSITS

Although the temporal distribution of mineral deposits in space and time reflects an interplay between processes of ore formation, tectonic setting and preservational history, many metallic mineral deposits correlate with major periods of continental crust production. Peaks in abundance of volcanic-hosted massive sulfides (VHMS) occur at 2.7, 1.9, and 0.5-0.3 Ga; in orogenic gold at 2.7, 1.9, 2.1, and 0.5-0.3 Ga; in iron-oxide copper-gold (IOCG) deposits at 2.6, 2.1 and 1.6 Ga; in platinum-group elements (PGE) at 2.7 and 2.0 Ga; in banded iron formation (BIF) and associated Mn carbonates at 2.5 and 1.9 Ga; in Mississippi Valley type base-metal (MVT) deposits at 0.5-0.3 and 0.1 Ga; and in sedimentary-exhalative base metal (SEDEX) deposits at 1.7-1.6 and 0.5-0.3 Ga.

Of the known or probable episodes of juvenile continental crust production at 2.8, 2.7, 2.5, 2.1, 1.9, 0.5-0.3 and 0.1 Ga, only the 2.7 and 1.9 Ga events appear to be global in extent and may reflect global mantle plume events. VHMS and orogenic gold deposits are directly related to subduction where new continental crust is formed. PGE, which occur in layered intrusions or associated with komatiites, very likely reflect mantle plume magma sources. Peaks in BIF and Mn carbonates at 2.5 and 1.9 Ga may also reflect mantle plume sources, with the Fe and Mn coming from plume-related submarine volcanism. IOCG are associated with alkaline granitoids formed after peaks in crust formation at 2.6 and 1.6 Ga and coincident with crust formation at 2.1 Ga. Fluids responsible for MVT deposits come from distant orogenic belts associated with juvenile continental crust formation and SEDEX deposits are formed from submarine hydrothermal fluids associated with rifting during or following peaks in crustal production. The correlation of some metallic mineral deposits with juvenile continental crust production suggests that the metals are either extracted directly from the mantle during crust formation (BIF, Au, VHMS, PGE, SEDEX) or/and from remobilization of metals derived from older crust (IOCG, MVT).