A new method for estimating parent rock trace element concentrations from zircon

Zircon/bulk rock REE partition coefficients from natural samples correlate with REE concentration in zircon. The correlation is the strongest for the LREE and diminishes with decreasing ionic radius. The relationship between partition coefficient and REE concentration in zircon can be modeled as a power law and the coefficient (α) and exponent (β) terms for each of the REE are empirically determined using new and previously published data. A series of independent tests show that using variable partition coefficients based on the reported α and β terms commonly results in more accurate estimates of bulk rock REE concentrations than average partition coefficients, particularly for the LREE that have previously been difficult to constrain. These results provide a way to account for highly variable REE concentrations in zircon, which may be controlled by numerous processes such as surface enrichment, complex substitution mechanisms, or accidental sampling of sub-microscopic inclusions. The proposed method for estimating bulk rock REE concentrations is especially well-suited to detrital zircon investigations where there is no information available on the parent rock composition.