Predictions of diagenetic reactions in the presence of organic acids

Journal Article · Sat Feb 01 04:00:00 EST 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90082-T· OSTI ID:5319850

Harrison, W J ^[1]; Thyne, G D ^[2]

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1. Colorado Schools of Mines, Golden (United States)
2. Univ. of Wyoming, Laramie (United States)

Stability constants have been estimated for cation complexes with anions of monofunctional and difunctional acids between 0 and 200C. Difunctional acid anions form much more stable complexes than monofunctional acid anions with aluminum; the importance of the aluminum-acetate complex is relatively minor in comparison to aluminum oxalate and malonate complexes. Divalent metal cations such as Mg, Ca, and Fe form more stable complexes with acetate than with difunctional acid anions. Mineral thermodynamic affinities were calculated using the reaction path model EQ3/6 for waters having variable organic acid anion (OAA) contents under conditions representative of those found during normal burial diagenesis. Organic acid anions are ineffective at neutral to alkaline pH in modifying stabilities of aluminosilicate minerals whereas the anions are variably effective under a wide range of pH in modifying carbonate mineral stabilities. Reaction path calculations demonstrate that the sequence of mineral reactions occurring in an arkosic sandstone-fluid system is only slightly modified by the presence of OAA. A spectrum of possible sandstone alteration mineralogies can be obtained depending on the selected boundary conditions: EQ3/6 predictions include quartz overgrowth, calcite replacement of plagioclase, albitization of plagioclase, and the formation of porosity-occluding calcite cement, smectite, and illite, all of which are commonly documented in rocks. In the scenarios modeled in this study the role of OAA in fluid-rock interactions is to contribute to the total alteration assemblage but not necessarily to dominate it, except under exceptional circumstances that might include, for example, hydrocarbon contaminant plumes in aquifers, wetland environments, and within hydrocarbon source-rocks.

• OSTI ID: 5319850
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 56:2; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ACTIVATION ENERGY
CHEMISTRY
DIAGENESIS
DISSOLUTION
ENERGY
FELDSPARS
GEOCHEMISTRY
KINETICS
MINERALIZATION
MINERALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
POROSITY
REACTION KINETICS
ROCK-FLUID INTERACTIONS
ROCKS
SEDIMENTARY ROCKS
SILICATE MINERALS
SOLVENT PROPERTIES
THERMODYNAMIC ACTIVITY