Evidence for variable provenance of Mercury anomalies during the Smithian–Spathian (Olenekian)

Abstract

Mercury (Hg) enrichment recorded in Smithian to Spathian (Olenekian) marine sedimentary successions has been used to link putative renewed Siberian Traps Large Igneous Province (STLIP) magmatism to climatic and environmental perturbations during this interval. To assess the potential for massive volcanism as a trigger for marine environmental disturbances across the Smithian – Spathian boundary (SSB), the patterns and provenance of Hg sequestration in four Tethyan marine sedimentary successions are investigated in the current study. We present a diverse array of new, temporally calibrated geochemical data including Hg concentrations and isotopic compositions, strontium, and neodymium isotope records, as well as major and trace element concentrations from carbonate-poor and -rich strata alike, including volcanic ashes. Results indicate that Hg anomalies in middle to late Smithian strata vary in magnitude and age. Based on several lines of evidence, the Hg anomalies recorded for the investigated PaleoTethyan successions are interpreted to have been sourced from subduction-related arc volcanism, with potential contributions from terrestrial Hg reservoirs. In contrast, a low-magnitude mercury enrichment interval recorded for NeoTethyan late Smithian strata is attributed to hydrothermal fluid or submarine volcanic activity. These results, together with previously published Smithian to Spathian Hg records, provide evidence that Smithian Hg anomalies cannot be attributed to a singular source such as renewed STLIP activity. Instead, the stratigraphically variable mercury anomalies reflect local patterns of enhanced mercury sequestration from various sources during the middle Smithian to SSB. Consequently, evidence for STLIP magmatism during the Smithian – Spathian transition is still lacking, and regional volcanic activity may have been influential in causing marine environmental upheavals in the Tethys region across the SSB.