Creator

Toth Attila

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Publication Date

January 2002

Keywords

Hungary, Geology, Anthropology

Description

Though it is the metastable polymorph of calcite at high temperature and pressure, aragonite can form, when certain conditions are met, at normal pressure and temperature. According to the Ca-Mg-C-O-H state diagram, aragonite deposition is mainly favoured by the Ca/Mg ratio and the concentration of CO2 from solution (fig. 1). Fischbeck and Muller (1971) have shown that, at a ratio of 2.9 Mg/Ca, aragonite is the main calcium carbonate that forms, while at a ratio of 4.4 is the only one. Filipov (1990) established that at a temperature of 10?C and a pH = 7, aragonite forms when the Mg/Ca ratio reaches 0.4. Aragonite precipitation is also influenced by other ions, such as Na+ and SO42-. Thus, at a variation of the concentrations of Mg2+ and Na+ ions (from hypersaline to normal marine), magnesium calcite and aragonite crystals grow fastly in the direction of the c axis, and very slowly in the direction of the other axes (Lippmann, 1960). SO42- and Mg2+ ions inhibit the development of calcite crystals and determine crystal growth parallel with the c axis (Bischoff and Fyfe, 1969). -- Author Open Access See Extended description for more information.

Subject: topical

Geology; Anthropology

Subject: geographic

Hungary

Type

Article

Genre

Article; serial

Identifier

K26-01252

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