Experimental Constraints on the Formation of Niningerite and Oldhamite Under Highly Reducing Conditions: Implications for Sulfide Formation in EH3 ChondritesOPEN ACCESS 

· by · in , , ,

N. Imae

JGR Planets, First Published: 10 August 2026

LINK (OPEN ACCESS)
PDF (OPEN ACCESS)

“Key Points

  • Ultra-reducing, sulfur-rich EH3 conditions were reproduced by vacuum-sealed experiments separating Mg-silicates from an Fe–S reservoir
  • Niningerite and oldhamite formed on Mg-silicates but not within the Fe–S reservoir
  • Sulfidation and segregation between silicate and metal-sulfide melts may explain sulfide-rich EH3 metal nodules”

“Enstatite chondrites record highly reducing conditions in the early solar nebula, yet the origin of their abundant sulfides remains unclear. Niningerite (MgS) and oldhamite (CaS) are ubiquitous in EH3 enstatite chondrites and distinguish them from other chondrite groups. To investigate sulfide formation, we conducted sulfidation experiments under ultra-reducing conditions using evacuated silica-glass tubes to reproduce extremely low oxygen pressure environments. Experiments at 1,200–1,420°C and IW−5 to −6 with pyrrhotite–troilite buffers examined reactions of Mg- and Ca-bearing silicates with sulfur-rich gas. Niningerite formed from forsterite–enstatite, and oldhamite from diopside, producing granular niningerite surrounding olivine and enstatite and granular oldhamite associated with diopside, coexisting with cristobalite and enstatite. Mg–Fe compositions of synthetic niningerite are included in those in EH3 chondrites. In the experiments, niningerite and oldhamite did not form within the coexisting Fe-S reservoir, whereas natural EH3 meteorites show enrichment of these sulfides in metal-sulfide nodules, a key discrepancy with natural EH3 textures. This suggests that the precursors of chondrules and metal nodules—aggregates of chondrules and metal nodules—underwent melting and segregation events, during which niningerite and oldhamite preferentially partitioned into the metal nodules. These multi-stage high-temperature processes provide new constraints on the physicochemical environment of sulfide formation in the inner solar nebula.”

Related posts (automatically generated):

  1. Magmatic sulfides in the porphyritic chondrules of EH enstatite chondritesOPEN ACCESS 
  2. Partitioning of Ru, Pd, Ag, Re, Pt, Ir and Au between sulfide-, metal- and silicate liquid at highly reduced conditions: implications for terrestrial accretion and aubrite parent body evolution
  3. An experimental study of chondrule formation interacting with the surrouding gas under the nebular conditions of reducing and 10-3 bars
  4. The First Discovery of Presolar Graphite Grains from the Highly Reducing Qingzhen (EH3) Meteorite
  5. Enstatite chondrites: condensation and metamorphism under extremely reducing conditions and contributions to the EarthOPEN ACCESS 
  6. The formation conditions of enstatite chondrites: Insights from trace element geochemistry of olivine-bearing chondrules in Sahara 97096 (EH3)
  7. Insights on the origin of oldhamite in enstatites meteorites from Ca stable isotopes
  8. Trace element partitioning between sulfide-, metal- and silicate melts at highly reduced conditions: Insights into the distribution of volatile elements during core formation in reduced bodies
  9. Experimental chondrite–water reactions under reducing and low-temperature hydrothermal conditions: Implications for incipient aqueous alteration in planetesimals
  10. Oxygen isotope compositions of chondrules in enstatite chondrites: insights from relict olivine, chondrule size and redox state
Tags: , , , , , , ,