Geochemistry of inorganic and organic sulphur in organic-rich sediments from the Peru Margin

Journal Article · Sun Dec 01 04:00:00 EST 1991 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(91)90057-C· OSTI ID:7049709

Mossmann, J R; Curtis, C D ^[1]; Aplin, A C; Coleman, M L ^[2]

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1. Univ. of Manchester (United Kingdom)
2. BP Research International, Middlesex (United Kingdom)

The authors have determined (1) the abundance and isotopic composition of pyrite, monosulfide, elemental sulfur, organically bound sulfur, and dissolved sulfide; (2) the partition of ferric and ferrous iron; (3) the organic carbon contents of sediments recovered at two sites drilled on the Peru Margin during Leg 112 of the Ocean Drilling Program. Sediments at both sites are characterized by high levels of organically bound sulfur (OBS). OBS comprises up to 50% of total sedimentary sulfur and up to 1% of bulk sediment. The weight ratio of S to C in organic matter varies from 0.03 to 0.15 (mean = 0.10). Such ratios are like those measured in lithologically similar, but more deeply buried petroleum source rocks of the Monterey and Sisquoc formations in California. Most inorganic Sulfur occurs as pyrite. Pyrite formation occurred within surface sediments and was limited by the availability of reactive iron. But despite highly reducing sulfidic conditions, only 35-65% of the total iron was converted to sulfide; 10-30% of the total iron still occurs as Fe(III). In surface sediments, the isotopic composition of pyrite is similar to that of both iron monosulfide and dissolved sulfide. Likely stoichiometries for the reaction between ferric iron and excess sulfide imply a maximum resulting FeS{sub 2}:FeS ratio of 1:1. Where pyrite dominates the pool of iron sulfides, at least some pyrite must have formed by reaction between monosulfide and elemental sulfur and/or polysulfide. Elemental sulfur (S{sup 0}) is most abundant in surface sediments and probably formed by oxidation of sulfide diffusing across the sediment-water interface.

• OSTI ID: 7049709
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 55:12; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200 -- Petroleum-- Reserves
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& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
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& Exploration
58 GEOSCIENCES
580000* -- Geosciences
CALIFORNIA
CARBON COMPOUNDS
CENOZOIC ERA
CHARGED PARTICLES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHEMISTRY
COMPARATIVE EVALUATIONS
CONTINENTAL MARGIN
CONTINENTAL SHELF
DEVELOPED COUNTRIES
DEVELOPING COUNTRIES
DIAGENESIS
ELEMENTAL MINERALS
EVALUATION
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC MODELS
GROUND WATER
HYDROGEN COMPOUNDS
INTERFACES
INTERSTITIAL WATER
IONS
IRON IONS
ISOTOPE RATIO
LATIN AMERICA
MATTER
MINERALS
MIOCENE EPOCH
NORTH AMERICA
ORGANIC COMPOUNDS
ORGANIC MATTER
ORGANIC SULFUR COMPOUNDS
OXYGEN COMPOUNDS
PERU
PYRITE
QUANTITY RATIO
REDOX REACTIONS
REDUCTION
RESERVOIR ROCK
SEDIMENT-WATER INTERFACES
SEDIMENTS
SOURCE ROCKS
SOUTH AMERICA
SULFIDE MINERALS
TERTIARY PERIOD
UPWELLING
USA
WATER