Physics
Scientific paper
Jun 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987gecoa..51.1413b&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 51, Issue 6, pp.1413-1423
Physics
13
Scientific paper
Free-drift dissolution data and inverse time plots were used to evaluate the stabilities of synthetic and biogenic magnesian calcites in aqueous solutions at 25°C and 1 atm total pressure. Synthetic phases with MgCO 3 concentrations below 6 mole percent have stoichiometric ion activity products that are less than the value for calcite, whereas the values for phases with higher concentrations are greater than that of calcite. For synthetic phases, stability is a smooth function of composition and all phases (up to 15 mole percent MgCO 3 ) have values of ion activity products less than that for aragonite. These results agree with those of and (1984) derived from precipitation of magnesian calcites in aqueous solutions. "Average" seawater at 25° and 1 atm total pressure is supersaturated with respect to all synthetic phases in the compositional range studied. Biogenic samples are less stable than synthetic phases of similar Mg concentrations and stability is not a smooth function of composition. Biogenic materials with compositions greater than 11-13 mole percent MgCO 3 have ion activity products greater than that for aragonite. The difference in stability between biogenic materials and synthetic phases is due to greater variation in chemical and physical heterogeneities found for the biogenic samples. If it is assumed that the results of the dissolution experiments reflect only differences in Gibbs free energies of formation between synthetic phases and biogenic materials of similar Mg concentration, the biogenic materials are 200-850 j/mol less stable than the synthetic phases. Only the results of synthetic dissolution experiments should be used to model the thermodynamic behavior of the magnesian calcite solid solution. The results for the synthetic phases, however, may not be appropriate to use for interpreting diagenetic reaction pathways for magnesian calcites in modern sediments, except as a basis of comparison with the behavior of natural materials.
Bischoff William D.
Bishop Finley C.
MacKenzie Fred T.
No associations
LandOfFree
Stabilities of synthetic magnesian calcites in aqueous solution: Comparison with biogenic materials does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Stabilities of synthetic magnesian calcites in aqueous solution: Comparison with biogenic materials, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stabilities of synthetic magnesian calcites in aqueous solution: Comparison with biogenic materials will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1817523