Nickel isotopes link Siberian Traps aerosol particles to the end-Permian mass extinction

The study investigates the causal link between Siberian Traps large igneous province (STLIP) volcanism and the end-Permian mass extinction (EPME, ~252 Ma), the most severe biotic crisis of the Phanerozoic. Proposed kill mechanisms tied to STLIP include global warming, UV stress, hypercapnia, ocean acidification/anoxia, and toxic metal release. A critical unknown is the nature and timing of volatile and metal emissions to the atmosphere prior to and during the extinction. Emplacement of the Noril’sk nickel sulphide ore deposits may have released Ni-rich gases and aerosols beginning ~300 kyr before the EPME. A Ni spike at Meishan has been proposed to stimulate methanogenic expansion, but its origin is debated. This work tests whether Ni-rich aerosols from STLIP were globally dispersed and affected ocean chemistry by analyzing Ni isotopes (δ60Ni) and concentrations from the Permian–Triassic Buchanan Lake section (Sverdrup Basin, Arctic Canada), aiming to constrain timing and mechanism of Ni loading and its environmental impacts leading up to the EPME.

Prior research links STLIP emplacement to environmental deterioration and the EPME, with evidence for contemporaneous pulses of magmatism, Hg anomalies, carbon cycle perturbations, and shifts to anoxia/euxinia. A Ni enrichment at Meishan near the extinction has been invoked to trigger methanogenic blooms and carbon cycle expansion, though diagenetic origins remain possible. Modern Ni cycling shows riverine dissolved Ni is isotopically heavy (avg δ60Ni ≈ +0.84‰) relative to crust, and open-ocean dissolved Ni is heavier still (≈ +1.44‰). Outputs include sediments and Fe–Mn crusts that typically record heavy values, with some light δ60Ni in deep oxygenated sediments attributed to diagenesis or mineral transformations. Sulfidic settings like the Black Sea exhibit relatively lighter sediment δ60Ni (≈ 0.14–0.51‰). Geological records of organic-rich shales show wide δ60Ni variation (≈ 0.2–2.5‰), likely reflecting variable sources. The lightest known δ60Ni values occur in magmatic Ni-sulfide systems (down to about −1.03‰), suggesting high-temperature fractionation in sulfide formation. These contexts frame interpretations of unusually light δ60Ni in ancient sediments as potential fingerprints of magmatic sulfide-derived Ni inputs.

Sampling and geological context: The Buchanan Lake section (Sverdrup Basin, Canadian High Arctic) records Late Permian black shales (Black Stripe Formation) transitioning through the EPME into Early Triassic (Blind Fiord Formation). Prior studies constrained carbon isotopes, elemental compositions, and redox evolution from oxic to anoxic to sulfidic conditions. Total sulfur contents and pyrite textures characterize redox states across stratigraphy. Nickel isotope measurements: About 100–300 mg of powdered samples were digested sequentially in distilled HF–HNO3, HNO3+HCl, and HNO3, dried, and redissolved in 0.3 N HNO3. Ni concentrations were determined by quadrupole ICP-MS (Agilent 7700). Aliquots containing ~1.5 μg Ni were spiked with a 60Ni–62Ni double spike (target spike:sample 64:36) and equilibrated. Chemical separation: Ni was purified via three-stage cation exchange using Bio-Rad AG50W-X8 resin: (1) 20% 10 M HCl–80% acetone to remove Fe, Mn, Cr; (2) 15% 10 M HCl–85% acetic acid to separate Ni from Mg, Ca, Al, Ti; (3) 0.9 M HNO3 to remove Na, K. Four USGS standards (Nod-A-1, BIR-1, BHVO-1, SCO-1) were processed alongside samples. Yields were >85% with blanks <10 ng. Isotopic analysis: δ60Ni was measured on a Nu Plasma II MC-ICP-MS with an Aridus II desolvating nebulizer, collecting 58Ni, 60Ni, 61Ni, 62Ni on Faraday cups. 57Fe was monitored to correct minor interference on 58Ni. Background on 60Ni was <10−3 V vs sample signals of ~3–4 V. Each sample and standard was run 4 times on different days. Data reduction used Matlab code (Romaniello; Wasylenki et al. 2014). Results are reported in per mil relative to NIST SRM 986. Long-term precision on a pure Ni solution was ±0.05‰. USGS standards yielded δ60Ni: Nod-A-1 +1.08 ± 0.06‰; BIR-1 +0.17 ± 0.02‰; BHVO-1 +0.05 ± 0.05‰; SCO-1 +0.11 ± 0.04‰. Stratigraphic/redox framework: Existing δ13Corg chemostratigraphy, Hg anomalies, and redox reconstructions (oxic to anoxic to sulfidic) were integrated to interpret temporal changes in δ60Ni and Ni content.

• δ60Ni in Buchanan Lake black shales spans −1.09‰ to +0.35‰, among the lightest values reported for sedimentary rocks; only magmatic Ni-sulfide deposits are lighter.
• Pre-EPME oxic interval (Black Stripe Fm., −86 to −62 m): very light δ60Ni from −0.89‰ to −1.09‰; Ni concentrations 157.1–247.1 ppm (well above average shale Ni ~68 ppm).
• Transition to anoxia (−62 to −2 m): δ60Ni increases from −0.99‰ up to +0.32‰ (minor fluctuation to +0.37‰ between −50 and −40 m); Ni contents 117.5–247.1 ppm with a weak decreasing trend.
• Near extinction level (−2 to 0 m; anoxic to sulfidic): δ60Ni remains positive (+0.07‰ to +0.34‰) with a sharp Ni drop from 142.8 ppm to 36.4 ppm.
• Post-extinction lower Blind Fiord Fm. (0–19.4 m; sulfidic): δ60Ni ~0.00‰ to +0.34‰; Ni contents 25.5–61.7 ppm.
• Temporal covariation: Ni enrichment and light δ60Ni coincide with episodes of coal ash fallout and Hg anomalies, and the onset of declining δ13Corg, consistent with early STLIP activity beginning ~500 kyr before the EPME and aligning with initial STLIP pulses ~300 ± 126 kyr prior.
• Source inference: The exceptionally light δ60Ni and elevated Ni levels indicate dominant input of isotopically light, Ni-rich aerosols derived from degassing and dispersal of STLIP magmatic Ni-sulfide systems (e.g., Noril’sk), consistent with magmatic sulfide δ60Ni signatures.
• Environmental linkage: The inferred Ni aerosol loading likely altered ocean Ni isotopic composition and chemistry globally and preceded the extinction; subsequent δ60Ni values and redox indicators resemble modern sulfidic settings (e.g., Black Sea).

The data demonstrate that isotopically light, Ni-rich aerosols from STLIP eruptions were widely dispersed and loaded into the Panthalassic Ocean well before the EPME. The light δ60Ni values, elevated Ni concentrations above shale background, and synchronicity with coal ash and Hg deposition strongly support a volcanic aerosol source rather than weathering or hydrothermal inputs. This external Ni input likely increased marine Ni availability, potentially stimulating primary productivity and methanogenic activity. Enhanced productivity and remineralization would have driven progressive deoxygenation from oxic to anoxic and eventually sulfidic conditions, aligning with independent redox proxies. Near the extinction horizon, the sharp decline in Ni abundance may reflect reduced aerosol loading and/or accelerated biological drawdown (e.g., methanogens). Main-phase STLIP degassing of greenhouse gases (CO2, CH4) from sills and contact-metamorphosed sediments likely amplified warming, expanded euxinia, and contributed 13C-depleted carbon to the ocean-atmosphere, explaining the pronounced negative δ13C excursion. Thus, Ni isotope records provide a mechanistic link between STLIP aerosol emissions, evolving ocean chemistry, and the cascade of environmental stresses culminating in the EPME.

This study provides isotopic evidence that Ni-rich aerosols from Siberian Traps eruptions were globally dispersed and significantly altered ocean chemistry hundreds of thousands of years before the end-Permian mass extinction. The Buchanan Lake δ60Ni record captures exceptionally light sedimentary values and elevated Ni concentrations consistent with a magmatic sulfide aerosol source, temporally aligned with early STLIP activity, coal ash loading, Hg anomalies, and the onset of carbon cycle perturbations. The results establish a causal chain linking atmospheric metal aerosol input to increased productivity, progressive deoxygenation/euxinia, greenhouse gas forcing, and mass extinction. Nickel isotopes emerge as a powerful tracer for volcanically driven environmental change. Future work should extend Ni isotope analyses across global Permian–Triassic successions to refine temporal-spatial patterns, quantify fluxes, and integrate with multiproxy records and models of ocean-atmosphere dynamics.

Interpretations rely on a single, albeit well-preserved, basin record (Buchanan Lake), so global representativeness requires corroboration from additional sections. The Ni aerosol source is inferred indirectly from isotopic signatures and stratigraphic correlations; no direct measurements of Late Permian aerosols or seawater Ni exist. Alternative processes (e.g., sorption to Mn oxides, diagenetic remobilization, continental weathering of Ni-sulfides) could in principle produce light δ60Ni, though the study argues these are inconsistent with the mineralogical context and regional geology. Lack of direct constraints on Late Permian hydrothermal δ60Ni also adds uncertainty, despite no evidence for local hydrothermal activity. Quantifying exact Ni fluxes and biological uptake pathways remains beyond the scope of the available data.