Pathways to Pyrite: Direct Evidence for Metastable Precursors in Marine Sediments

Pathways to Pyrite: Direct Evidence for Metastable Precursors in Marine Sediments | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Pathways to Pyrite: Direct Evidence for Metastable Precursors in Marine Sediments Maria Figueroa, Ravi Kukkadapu, Gregory Daniel, Anthony Chappaz, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7755294/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The formation of pyrite is a critical process in sedimentary environments, central to the global iron and sulfur cycles and redox-sensitive biogeochemical processes. Yet the pathways and mechanisms driving pyrite formation, particularly the roles of metastable iron sulfide (FeSx) phases and polysulfides (Sn2-), remain poorly understood under natural conditions. Here we provide the first direct evidence for polysulfide-mediated pyrite formation in marine sediments, using Mössbauer spectroscopy and X-ray photoelectron spectroscopy, on cores from Saanich Inlet. We identify two distinct nanoparticulate FeS1+x phases: a mackinawite-like and a greigite-like phase. We find that under highly reducing conditions the greigite-like phase can compete with pyrite as the prevailing Fe-S mineral. Our results also reveal limitations of sequential chemical extractions, particularly in underestimating highly reactive mineral phases. These findings highlight the advantage of high-resolution deterministic spectroscopic tools for the identification of nanoparticulate complexes. While the polysulfide pathway has been widely inferred, direct detection of polysulfides and intermediate FeSx phases in marine sediments has remained elusive. Our study confirms the polysulfide pathway, bridging a long-standing gap between experimental models and environmental observations. These findings refine our understanding of early-diagenetic Fe-S transformations and how sulfide minerals form and persist in Earth’s dynamic sedimentary environment. Earth and environmental sciences/Biogeochemistry/Element cycles Earth and environmental sciences/Ocean sciences/Marine chemistry Full Text Additional Declarations There is NO Competing Interest. Supplementary Files FigueroaetalNGeoSupplementaryInformation.pdf Supplementary Information Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7755294","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":527075027,"identity":"e21656e6-40f2-4abf-8987-853d4121f199","order_by":0,"name":"Maria 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