Evaporative Loss of Volatile Elements during Impact-Induced Melting: Evidence from the Sudbury Impact Structure

Abstract Large impact events generate extensive volumes of high-temperature silicate melt and are widely recognized as fundamental processes in the evolution of terrestrial planets. However, the extent to which impact-induced melting and volatilization can modify volatile element inventories remains poorly constrained. The Sudbury Impact Structure, Canada, preserves one of the largest and best-exposed differentiated impact melt sheets on Earth and provides an exceptional natural laboratory for investigating volatile element behaviour in impact-generated melts. Here, we quantify volatile element abundances in the Sudbury impact melt sheet and evaluate the extent and controls of volatile depletion. Two complementary melt reservoirs were compared: i) the undifferentiated, aphanitic margins of the offset dikes, which approximate the initial impact melt composition and ii) the northern Main Mass, which records subsequent differentiation of the melt sheet. Relative to a locally constrained target crustal composition, most lithophile elements, including high field-strength elements, rare-earth elements, and alkali metals remain near crustal abundances and show little evidence for impact-induced volatilization. In contrast, chalcophile elements display pronounced depletion, with As-Sb-Bi and S-Se-Te depleted by 40-90% relative to the target crust, and Ni-Cu depleted by >80% in the differentiated Main Mass. The primary volatilization signature is best preserved in the offset dike margins, whereas the northern Main Mass records additional modification by fractional crystallization, interaction with sulfide liquids, and hydrothermal alteration. Observed depletion patterns are consistent with volatility scales derived from volcanic systems and silicate melt evaporation experiments, indicating that element volatility during impact melting was governed primarily by high-temperature evaporative processes. In contrast, nebular condensation temperatures are a poor predictor of volatility in impact-melt systems. By documenting systematic volatile element depletion in one of Earth’s largest impact melt sheets, this study provides direct evidence that impact-induced melting and evaporation can modify crustal volatile inventories on a regional scale. These results further suggest that large impacts may have contributed to the volatile evolution of Earth and other terrestrial planets during periods of intense bombardment in the early stages of planetary formation.