Pathways to pyrite through polysulfides and metastable iron sulfides in marine sediments
Abstract
The formation of pyrite (FeS₂) is a critical process in sedimentary environments, central to the global iron and sulfur cycles and sedimentary redox cycling. However, the mechanisms governing pyrite formation under natural conditions remain poorly constrained. Using Mössbauer spectroscopy and X-ray photoelectron spectroscopy (XPS), we present direct evidence of polysulfides facilitating the transformation of FeS x phases into pyrite in natural sediments from Saanich Inlet, British Columbia. We identify two nanoparticulate FeS 1+x phases: a mackinawite-like phase (np-FeS 1+x −1) and a greigite-like phase (np-FeS 1+x −2). Under persistently sulfidic conditions, the greigite-like phase can compete with pyrite as the prevailing Fe-S mineral. We also demonstrate that sequential chemical extractions underestimate highly reactive nanoparticulate Fe phases owing, in part, to pyrite framboids encapsulated within diatom frustules. Notably, these findings provide direct spectroscopic evidence consistent with polysulfide-mediated Fe-S transformations in low-temperature natural sediments, bridging a long-standing gap between experimental models and environmental observations and refining our understanding of early diagenetic pyrite formation.
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BibTeX
@article{figueroa2026pathways,
title = {{Pathways to pyrite through polysulfides and metastable iron sulfides in marine sediments}},
author = {Maria C. Figueroa and Ravi K. Kukkadapu and Daniel D. Gregory and Anthony Chappaz and Mark H. Engelhard and Timothy W. Lyons},
journal = {Communications Earth \& Environment},
year = {2026},
month = oct,
doi = {10.1038/s43247-026-04161-z},
url = {https://www.nature.com/articles/s43247-026-04161-z},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Pathways to pyrite through polysulfides and metastable iron sulfides in marine sediments
AU - Maria C. Figueroa
AU - Ravi K. Kukkadapu
AU - Daniel D. Gregory
AU - Anthony Chappaz
AU - Mark H. Engelhard
AU - Timothy W. Lyons
PY - 2026
DA - 2026/10/28
JO - Communications Earth & Environment
DO - 10.1038/s43247-026-04161-z
UR - https://www.nature.com/articles/s43247-026-04161-z
AB - The formation of pyrite (FeS₂) is a critical process in sedimentary environments, central to the global iron and sulfur cycles and sedimentary redox cycling. However, the mechanisms governing pyrite formation under natural conditions remain poorly constrained. Using Mössbauer spectroscopy and X-ray photoelectron spectroscopy (XPS), we present direct evidence of polysulfides facilitating the transformation of FeS x phases into pyrite in natural sediments from Saanich Inlet, British Columbia. We identify two nanoparticulate FeS 1+x phases: a mackinawite-like phase (np-FeS 1+x −1) and a greigite-like phase (np-FeS 1+x −2). Under persistently sulfidic conditions, the greigite-like phase can compete with pyrite as the prevailing Fe-S mineral. We also demonstrate that sequential chemical extractions underestimate highly reactive nanoparticulate Fe phases owing, in part, to pyrite framboids encapsulated within diatom frustules. Notably, these findings provide direct spectroscopic evidence consistent with polysulfide-mediated Fe-S transformations in low-temperature natural sediments, bridging a long-standing gap between experimental models and environmental observations and refining our understanding of early diagenetic pyrite formation.
SN - 2662-4435
ER -