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Behaviour of magnesium and strontium during the transformation of coral aragonite to calcite in aquatic environments

1986; Elsevier BV; Volume: 18; Issue: 1 Linguagem: Inglês

10.1016/0304-4203(86)90074-5

1872-7581

Sayoko Yoshioka, Shigeru Ohde, Yotaro Kitano, Nobuko Kanamori,

Groundwater and Isotope Geochemistry

Some coral aragonites transform easily to calcite in aquatic environments. The behaviour of magnesium and strontium in the coral aragonite-to-calcite transformation process was examined through laboratory experiments and field observations; the coral aragonite samples came from Okinawa and Kagoshima prefectures. When powdered coral aragonite is suspended in aqueous solution, hydrophobic and hydrophilic suspensions are observed. The transformation rate of hydrophilic aragonite is higher than that of hydrophobic. The release of strontium from hydrophilic aragonite into solution is very active; it increases with increasing transformation of aragonite to calcite. Magnesium is dissolved very rapidly into solution. The strontium content of calcite transformed from coral aragonite is 1500 ppm or more. These experimental results are supported by the analytical results of natural coral samples collected from Okinawa islands and Kagoshima prefecture, which suggests that the transformation from aragonite to calcite does not occur through the complete dissolution of aragonite and the complete recrystallization of calcite in aqueous solutions.