Magnesian calcite stabilities in aqueous solution: contrasts in results from dissolution of biogenic and synthetic phases and biogenic precipitation

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

OSTI ID:6862774

Bischoff, W D; Agegian, C; MacKenzie, F T

Dissolution studies were performed on a series of biogenic and synthetic Mg - calcites to evaluate their stabilities in aqueous solution at 25/sup 0/C. Synthetic phases with MgCO/sub 3/ concentrations below 4 mole% are more stable, whereas those with higher concentrations are less stable than calcite,with stability smoothly decreasing as a function of composition. These results are similar to previous experiments involving inorganic precipitation of Mg - calcite. Biogenic samples are less table than synthetic phases, and the stability decrease does not vary smoothly with composition. For the biogenic materials, those with compositions greater than 11-13 mole% MgCO/sub 3/ are less stable than aragonite. The composition of skeletal Mg - calcite precipitated by the coralline alga Porolithon gardineri in environmentally controlled sea water was measured as a function of temperature, available light, and saturation state. Saturation state is the most important factor that determines Mg concentration. In contrast to dissolution experiments, only small differences in Mg concentration are observed for large changes in saturation state. The concentration of MgCO/sub 3/ in the precipitated material ranges from 15 moles% at a stoichiometric ion activity product (IAP) equal to calcite saturation to 19.5 mole% at an IAP approximately seven times the saturation of calcite.

• Research Organization: Wichita State Univ., KS (USA)
• OSTI ID: 6862774
• 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

550200 -- Biochemistry
58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
59 BASIC BIOLOGICAL SCIENCES
ACTIVATION ENERGY
ALKALINE EARTH METAL COMPOUNDS
BIOGEOCHEMISTRY
BIOSYNTHESIS
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMICAL COMPOSITION
CHEMISTRY
DISSOLUTION
DOLOMITE
ENERGY
GEOCHEMISTRY
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MATERIALS
MINERALS
OXYGEN COMPOUNDS
ROCKS
SATURATION
SOLUBILITY
SYNTHESIS
SYNTHETIC MATERIALS
SYNTHETIC ROCKS