Role of degassing of the Noril'sk nickel deposits in the Permian-Triassic mass extinction event

Carbonated magmatic sulfide systems: Still or sparkling?

For decades, there has been debate surrounding the transport of dense metal-rich sulfide liquid in mafic magmas. This topic is crucial to understanding the genesis of valuable resources of nickel, copper, and platinum-group elements, which are essential for a sustainable, emission-free energy future. Recent studies of mineralized mafic magmas suggested that gas bubbles adhere to sulfide globules, reducing their density and favoring upward transport. While this hypothesis may explain sulfide mobility in near-surface magmatic environments, it is at odds with key mineralogic and textural observations and does not explain how long-distance sulfide transport operates. Here, we suggest an alternative hypothesis that builds on previous observations, focusing on the interaction between carbonate melt and sulfide liquid. We demonstrate experimentally that carbonate melt wraps sulfide globules forming a relatively mobile pair that may mediate metal-rich sulfide transport from mantle to crust.

Transfer of sulfur and chalcophile metals via sulfide-volatile compound drops in the Christiana-Santorini-Kolumbo volcanic field

Efficient transfer of S and chalcophile metals through the Earth's crust in arc systems is paramount for the formation of large magmatic-hydrothermal ore deposits. The formation of sulfide-volatile compound drops has been recognized as a potential key mechanism for such transfer but their fate during dynamic arc magmatism remains cryptic. Combining elemental mapping and in-situ mineral analyzes we reconstruct the evolution of compound drops in the active Christiana-Santorini-Kolumbo volcanic field. The observed compound drops are micrometric sulfide blebs associated with vesicles trapped within silicate phenocrysts. The compound drops accumulate and coalesce at mafic-felsic melt interfaces where larger sulfide ovoids form. These ovoids are subsequently oxidized to magnetite during sulfide-volatile interaction. Comparison of metal concentrations between the sulfide phases and magnetite allows for determination of element mobility during oxidation. The formation and evolution of compound drops may be an efficient mechanism for transferring S and chalcophile metals into shallow magmatic-hydrothermal arc systems.

Mercury evidence from southern Pangea terrestrial sections for end-Permian global volcanic effects

The latest Permian mass extinction (LPME) was triggered by magmatism of the Siberian Traps Large Igneous Province (STLIP), which left an extensive record of sedimentary Hg anomalies at Northern Hemisphere and tropical sites. Here, we present Hg records from terrestrial sites in southern Pangea, nearly antipodal to contemporaneous STLIP activity, providing insights into the global distribution of volcanogenic Hg during this event and its environmental processing. These profiles (two from Karoo Basin, South Africa; two from Sydney Basin, Australia) exhibit significant Hg enrichments within the uppermost Permian extinction interval as well as positive Δ¹⁹⁹Hg excursions (to ~0.3‰), providing evidence of long-distance atmospheric transfer of volcanogenic Hg. These results demonstrate the far-reaching effects of the Siberian Traps as well as refine stratigraphic placement of the LPME interval in the Karoo Basin at a temporal resolution of ~10⁵ years based on global isochronism of volcanogenic Hg anomalies.

The critical role of magma degassing in sulphide melt mobility and metal enrichment

Much of the world’s supply of battery metals and platinum group elements (PGE) comes from sulphide ore bodies formed in ancient sub-volcanic magma plumbing systems. Research on magmatic sulphide ore genesis mainly focuses on sulphide melt-silicate melt equilibria. However, over the past few years, increasing evidence of the role of volatiles in magmatic sulphide ore systems has come to light. High temperature-high pressure experiments presented here reveal how the association between sulphide melt and a fluid phase may facilitate the coalescence of sulphide droplets and upgrade the metal content of the sulphide melt. We propose that the occurrence of a fluid phase in the magma can favour both accumulation and metal enrichment of a sulphide melt segregated from this magma, independent of the process producing the fluid phase. Here we show how sulphide-fluid associations preserved in the world-class Noril’sk-Talnakh ore deposits, in Polar Siberia, record the processes demonstrated experimentally.

A new study shows the occurrence of a fluid phase in mafic-ultramafic magmas may represent a significant boost for magmatic sulphide ore forming processes, by favouring sulphide melt accumulation and increasing tenors.

Fluids as primary carriers of sulphur and copper in magmatic assimilation

Magmas readily react with their wall-rocks forming metamorphic contact aureoles. Sulphur and possibly metal mobilization within these contact aureoles is essential in the formation of economic magmatic sulphide deposits. We performed heating and partial melting experiments on a black shale sample from the Paleoproterozoic Virginia Formation, which is the main source of sulphur for the world-class Cu-Ni sulphide deposits of the 1.1 Ga Duluth Complex, Minnesota. These experiments show that an autochthonous devolatilization fluid effectively mobilizes carbon, sulphur, and copper in the black shale within subsolidus conditions (≤ 700 °C). Further mobilization occurs when the black shale melts and droplets of Cu-rich sulphide melt and pyrrhotite form at ∼1000 °C. The sulphide droplets attach to bubbles of devolatilization fluid, which promotes buoyancy-driven transportation in silicate melt. Our study shows that devolatilization fluids can supply large proportions of sulphur and copper in mafic-ultramafic layered intrusion-hosted Cu-Ni sulphide deposits.

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

The end-Permian mass extinction (EPME) was the most severe extinction event in the past 540 million years, and the Siberian Traps large igneous province (STLIP) is widely hypothesized to have been the primary trigger for the environmental catastrophe. The killing mechanisms depend critically on the nature of volatiles ejected during STLIP eruptions, initiating about 300 kyr before the extinction event, because the atmosphere is the primary interface between magmatism and extinction. Here we report Ni isotopes for Permian-Triassic sedimentary rocks from Arctic Canada. The δ⁶⁰Ni data range from −1.09‰ to 0.35‰, and exhibit the lightest δ⁶⁰Ni compositions ever reported for sedimentary rocks. Our results provide strong evidence for global dispersion and loading of Ni-rich aerosol particles into the Panthalassic Ocean. Our data demonstrate that environmental degradation had begun well before the extinction event and provide a link between global dispersion of Ni-rich aerosols, ocean chemistry changes, and the EPME.

The end-Permian mass extinction was the most severe extinction event in the past 540 million years, and the Siberian Traps large igneous province is widely hypothesized to have been the primary trigger for the environmental catastrophe. In this study, Ni isotopes provide the link between Siberian Traps magmatism and early environmental degradation, ultimately leading to the end-Permian extinction.

Fluxing of mantle carbon as a physical agent for metallogenic fertilization of the crust

Magmatic systems play a crucial role in enriching the crust with volatiles and elements that reside primarily within the Earth's mantle, including economically important metals like nickel, copper and platinum-group elements. However, transport of these metals within silicate magmas primarily occurs within dense sulfide liquids, which tend to coalesce, settle and not be efficiently transported in ascending magmas. Here we show textural observations, backed up with carbon and oxygen isotope data, which indicate an intimate association between mantle-derived carbonates and sulfides in some mafic-ultramafic magmatic systems emplaced at the base of the continental crust. We propose that carbon, as a buoyant supercritical CO2 fluid, might be a covert agent aiding and promoting the physical transport of sulfides across the mantle-crust transition. This may be a common but cryptic mechanism that facilitates cycling of volatiles and metals from the mantle to the lower-to-mid continental crust, which leaves little footprint behind by the time magmas reach the Earth's surface.