Year: 2026
Type: article
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.
Authors: Maria C. Figueroa, Ravi K. Kukkadapu, Daniel D. Gregory, Anthony Chappaz, Mark H. Engelhard, Timothy W. Lyons
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,490
Awards: G1202769797, G125460123, G2506945562, G2510423872, G2820049545, Collaborative Research: Trace Elements in Pyrite—Validation and Calibration of a Novel Paleoenvironmental Proxy, Collaborative Research: Trace Elements in Pyrite—Validation and Calibration of a Novel Paleoenvironmental Proxy, G5373841109, G5653134238, G7560550554, G821644656
OpenAlex ID: W4417069995