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

Journal Article · Sun Dec 01 00:00:00 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), Vol. 55:12; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

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