Applications of Lead Isotopes to Ore Geology, Metallogenesis and Exploration

Abstract

AbstractAlthough lead isotopes are most commonly used to date geological events, including mineralizing events, they also can provide information on many aspects of metallogeny and can be directly used in mineral exploration. Lead isotope data are generally reported as ratios of radiogenic isotopes normalized to the non-radiogenic isotope204Pb (e.g.206Pb/204Pb,207Pb/204Pb and208Pb/204Pb). These ratios can be used in exploration to characterize the style of mineralization, metal (i.e. Pb) source and as vectors to ore. When combined with lead isotope evolution models, the data can be used to indicate the age and tectonic environment of mineralization. The raw ratios and evolution models enable calculation of derived parameters such as μ (238U/204Pb), κ (232Th/238U) and ω (232Th/204Pb), which provide more information about tectonic setting and can be contoured to identify crustal boundaries and metallogenic provinces. In some cases, tectonic boundaries, mapped using gradients in μ and other derived parameters, are fundamental controls on the distribution of certain deposit types in space and time. Moreover, crustal character, as determined by lead and other radiogenic isotopes (e.g. Nd) can be an indicator of province fertility for many deposit types. The development of cost effective analytical techniques and the assembly of large geo-located datasets for lead and other isotope data has enabled significant advances in understanding the genesis and localization of many deposit type, particularly when the isotopic data are integrated with other independent datasets such as potential field, magnetotelluric, passive seismic and geochemical data.