Tectonic Controls on the Endowment of Neoarchean Cratons in Volcanic-Hosted Massive Sulfide Deposits: Evidence from Lead and Neodymium Isotopes

Abstract

Review and analysis of initial lead isotope ratios from Archean volcanic-hosted massive sulfide (VHMS) and lode gold deposits and of neodymium isotopes from igneous rocks from the geologic provinces that host these deposits identifies systematic spatial and temporal patterns, both within and between the provinces. The Abitibi-Wawa subprovince of the Superior province is characterized by highly juvenile lead and neodymium. Most other Archean provinces, however, are characterized by more evolved isotopes, although domains within them can be characterized by juvenile isotope ratios. The analysis indicates that the endowment (measured as the quantity of metal contained in geologic resources per unit surface area) of VHMS and komatiite-associated nickel sulfide deposits is related to the isotopic character and, therefore, the tectonic history of provinces that host these deposits. Provinces with extensive juvenile crust have significantly higher endowment of VHMS deposits, possibly as a consequence of higher heat flow and extension-related faults. Provinces with evolved crust have higher endowment of komatiite-associated nickel sulfide deposits, possibly because such crust provided either a source of sulfur or a stable substrate for komatiite emplacement. In any case, initial radiogenic isotope ratios can be useful in predicting the endowment of Archean terranes for VHMS and komatiite-associated nickel sulfide deposits. Limited data suggest similar relationships may hold in younger terranes. Lead isotope data may provide constraints on supercraton reconstructions in the Archean as lead isotope systematics appear to be highly provincial. Similar isotope systematics between the Superior province and the Eastern Goldfields superterrane may indicate a linkage during the Neoarchean, consistent with the similar geologic and metallogenic histories of these provinces.