Physico-chemical controls on the rate of dedolomitization of protodolomites and dolomite: an experimental study

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6194468

Kastner, M

Dedolomitization, the partial or complete replacement of dolomite by calcite, is well documented in the literature. Texturally, the replacement process proceeds in a centripetal, centrifugal, or irregular manner. These reactions were studied in laboratory experiments conducted between 150/sup 0/C and 200/sup 0/C in Ca, Mg, and Na chloride solutions of various Ca/Mg ratios, both in the absence and presence of dissolved sulfate. The rate of dedolomitization is mainly controlled by (1) the Ca/Mg ratio of the dedolomitizing solution, (2) the nature of the mineral undergoing dedolomitization, (3) the temperature, (4) the concentration of dissolved sulfate, and (5) the solution/rock ratio. The rates of dedolomitization of both protodolomites and dolomites increase with increasing Ca/Mg ratios, temperature and water/rock ratios, and decrease with increasing concentration of dissolved sulfate. At moderate temperatures the rates of calcite and aragonite dolomitization, in solutions with molar Ca/Mg ratios of 0.60 to 0.75, are rather rapid, whereas the dedolomitization reaction is sluggish, and proceeds rapidly only well within the stability field of calcite at molar Ca/Mg ratios of >5. Thus, dedolomitization is not merely a near-surface chemical weathering process; it is primarily a diagenetic reaction which proceeds in the presence of solutions within the stability field of calcite. Chemical zoning in dolomite and local or regional chemical inhomogeneities in dolomites will control the sequences and rates of the dedolomitization reaction, and thus the textures of the resulting sedimentary rocks.

• Research Organization: Scripps Institution of Oceanography, La Jolla, CA (USA)
• OSTI ID: 6194468
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ACTIVATION ENERGY
ALKALINE EARTH METAL COMPOUNDS
BENCH-SCALE EXPERIMENTS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
DIAGENESIS
DISSOLUTION
DOLOMITE
ENERGY
GEOCHEMISTRY
KINETICS
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MINERALS
OXYGEN COMPOUNDS
PRECIPITATION
REACTION KINETICS
ROCKS
SEDIMENTARY ROCKS
SEPARATION PROCESSES
TEMPERATURE EFFECTS