Anomalous enrichments of iron monosulfide in euxinic marine sediments and the role of H2S in iron sulfide transformations; examples from Effingham

• Main Authors: Matthew T. Hurtgen, Timothy W. Lyons, Ellery D. Ingall, Anna M. Cruse
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1999
• Subjects: Orca
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.532.8618; http://earth.geology.yale.edu/~ajs/1999/07-09.1999.03Hurtgen.pdf

ABSTRACT. It is well documented that sedimentary pyrite formation proceeds through an iron monosulfide (FeS) precursor. Laboratory studies have tradition-ally indicated that intermediate S species such as elemental sulfur (S0) or polysul-fides (Sx2) are responsible for the transformation of FeS to pyrite (FeS2). Recent experimental work, however, has suggested that H2S may also be responsible for the transformation. The present study extrapolates reaction pathways respon-sible for pyrite formation in the laboratory to two fundamentally different modern anoxic marine systems. We hypothesize that on decadal timescales, H2S (or HS) is responsible for transformations of FeS into FeS2 in natural systems where intermediate S species are isolated from FeS production. The possibility of prolonged coexistence of high levels of H2S and FeS, however, challenges recent experimental predictions of extremely rapid transformations (that is, timescales of hours or less) of FeS to FeS2 via the H2S pathway. Sediments of Effingham Inlet (a fjord on Vancouver Island) and the Orca Basin (an intraslope brine pool in the northern Gulf of Mexico) are both charac-