Data and supporting information for: From source rock to cinnabar – how the giant mercury deposits in earth’s crust formed
Data files
Dec 10, 2025 version files 844.10 KB
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AJS_FINAL_D_SI.pdf
840.77 KB
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README.md
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Dec 10, 2025 version files 844.14 KB
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AJS_FINAL_D_SI.pdf
840.77 KB
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README.md
3.37 KB
Abstract
The largest concentrations of Hg on Earth exist as giant deposits of cinnabar (HgS). How such enrichments of Hg formed, based on its known crustal abundance has never been fully resolved, nor has the source(s) of Hg been unequivocally established. Hg isotopes were used to elucidate crustal processes leading to the concentration of Hg during thermal maturation of Hg and organic matter enriched sediments and cinnabar formation. Mass dependent fractionation (MDF) of Hg isotopes shows remarkable enrichment of 202Hg in cinnabar relative to its upper mantle source. Two mechanisms contribute to this enrichment: one is the low temperature, early diagenetic loss of volatile 198Hg0(g) to an extant gas phase; the other is oxidation during cinnabar deposition. Loss of 198Hg0(g) results in 202Hg enrichment of Hg in residual organic matter in source sediments. Evidence for this significant loss of 198Hg0(g) is observed as large depletions in the δ202Hg isotopic composition of proximal gas condensate liquids in high pressure – high temperature (HP/HT) reservoirs in the central North Sea (CNS). Migration of hydrocarbons and formation brines from Hg-enriched sediments transports reduced Hg0(org, aq) to the site of cinnabar deposition, where oxidation of Hg0(org, aq) and H2S further enhances enrichment of 202Hg in cinnabar. The large changes in MDF are independent of mass independent fractionation (MIF) of mercury isotopes.
Approximately 80% of the cinnabar samples examined in this study plot within ± 0.1‰ of the origin on a Δ199Hg - Δ201Hg MIF Hg isotope plot and have a Hg isotopic composition similar to that of continental flood basalts (CFB), consistent with an upper mantle source for Hg. MIF trends defined by coals and euxinic sediments on Δ199Hg - Δ201Hg MIF plots have Δ199Hg /Δ201Hg slopes ~ 1. These tend to be the most reduced Hg-enriched sediments, deposited in anoxic or euxinic environments in which the dominant Hg species is Hg0. In open marine environments the dominant Hg species is likely to be Hg2+. Δ199Hg /Δ201Hg slopes >1 deviating from these reduced sediment trends appear to be controlled by the fugacity of H2S (fH2S), and variable proportions of reduced Hg0 to oxidized Hg2+ in progenitor sediments, reflecting their environments of deposition and redox state.
Dataset DOI: 10.5061/dryad.2547d7x5j
This Data and Supporting Information file (AJS_FINAL_D_SI.pdf) includes the following sections:
Mercury isotopes: Includes a brief description of nomenclature used in reporting both mass dependent and mass independent mercury isotopic data, together with a detailed description of laboratory and analytical procedures used in sample preparation and analysis of mercury isotopic composition in natural mercury-bearing samples discussed in this study.
Table S1: MC-ICP-MS operating parameters and measurement conditions for isotope ratio measurements.
Supporting references
Hg isotope data for cinnabar from each deposit discussed in this study
Hg isotope data for each deposit were compiled from previously published studies, and together with a short summary of the geological setting are given in supplementary tables S2-S8, together with the published source of the data.
Table S2: Mercury isotope data for cinnabar and Hg ore minerals from Terlingua (SW Texas), McDermitt (Nevada), and New Idria (California Coast Range), USA
Table S3: Mercury isotope data for cinnabar ore from Huancavelica, Peru
Table S4: Mercury isotope data for cinnabar ore from Indrija mercury mine, Slovenia
Table S5: Mercury isotope data for Hg0 and cinnabar ore from Almaden, Spain
Table S6: Mercury isotope data for cinnabar ore from Monte Amiata, Tuscany, Italy
Table S7: Mercury isotopic data for Almaden cinnabar and corresponding Pb-Pb ages
Figure S1. A) MDF versus MIF plot for Hg0 and HgS from Almaden (Spain). B) HgS and Hg0 isotope data plotted as a function of their respective Pb-Pb ages.
Table S8: Mercury isotope data for Hg0 and cinnabar ore from Wanshan, China
Hg isotope data for subsurface formations, hydrocarbons, and source rocks are given in supplementary tables S9-S15
Table S9: Mercury isotope data for subsurface formations – Central North Sea
Table S10: Mercury isotope data for hydrocarbons
Table S11: Mercury isotope data for source rocks and hydrocarbons from Bohai Bay and Sichuan Basin
Table S12: MDF (δ202Hg) and MIF (Δ199Hg) Hg isotope data from OAE-2 rocks, including limestone, marl, black shale and claystone from Rehkogelgraben, Austria.
Figure S2. Caption same as for figure 5 in main text.
Table S13: MDF (δ202Hg) and MIF (Δ199Hg; Δ201Hg) Hg isotope data from Cambrian black shales and tuffs, South China
Table S14: MDF (δ202Hg) and MIF (Δ199Hg) Hg isotope data from PTB sediments
Table S15: MDF (δ202Hg) and MIF (Δ199Hg) Hg isotope data from LPE sediments
Figure S3. fH2S versus Δ199Hg in gas condensate reservoirs from the CNS
Table S16: Estimated temperatures of cinnabar (HgS) formation from δ202Hg isotopic composition and assuming equilibrium with 198Hg0(g) evaporation temperatures (based on the experimental data from Estrade et al., 2009).
D&SI References
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