sup 13 C and sup 18 O isotopic disequilibrium in biological carbonates: II. In vitro simulation of kinetic isotope effects

Journal Article · Sun Jan 01 04:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90283-4· OSTI ID:7000662

McConnaughey, T ^[1]

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1. Univ. of Washington, Seattle (USA)

Biological carbonates are built largely from CO{sub 2}, which diffuses across the skeletogenic membrane and reacts to form HCO{sub 3}{sup {minus}}. Kinetic discrimination against the heavy isotopes {sup 18}O and {sup 13}C during CO{sub 2} hydration and hydroxylation apparently causes most of the isotopic disequilibrium observed in biological carbonates. These kinetic isotope effects are expressed when the extracytosolic calcifying solution is thin and alkaline, and HCO{sub 3}{sup {minus}} precipitates fairly rapidly as CaCO{sub 3}. In vitro simulation of the calcifying environment produced heavy isotope depletions qualitatively similar to, but somewhat more extreme than, those seen in biological carbonates. Isotopic equilibration during biological calcification occurs through CO{sub 2} exchange across the calcifying membrane and by admixture ambient waters (containing HCO{sub 3}{sup {minus}}) into the calcifying fluids. Both mechanisms tend to produce linear correlations between skeletal {delta}{sup 13}C and {delta}{sup 18}O.

• OSTI ID: 7000662
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:1; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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58 GEOSCIENCES
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59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
ANIMALS
ARAGONITE
BIOCHEMICAL REACTION KINETICS
BIOGEOCHEMISTRY
BODY
CALCIUM CARBONATES
CALCIUM COMPOUNDS
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CARBON COMPOUNDS
CARBON DIOXIDE
CARBON ISOTOPES
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CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
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COELENTERATA
CORALS
DEVELOPING COUNTRIES
ECUADOR
EQUILIBRIUM
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXOSKELETON
GEOCHEMISTRY
GEOLOGIC STRUCTURES
HYDRATION
HYDROXYLATION
INVERTEBRATES
ISOTOPE RATIO
ISOTOPES
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MINERAL CYCLING
MINERALS
NUCLEI
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OXYGEN 18
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SEPARATION PROCESSES
SKELETON
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SOUTH AMERICA
STABLE ISOTOPES