Publication: Electron spin resonance studies of Mn<sup>2+</sup>in freshwater snail shells: Pomacea canaliculata lamarck and fossilized snail shell
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Issued Date
2005-07-01
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ISSN
0256307X
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2-s2.0-22044439997
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Mahidol University
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SCOPUS
Bibliographic Citation
Chinese Physics Letters. Vol.22, No.7 (2005), 1780-1783
Suggested Citation
N. Udomkan, S. Meejoo, P. Limsuwan, P. Winotai, Y. Chaimanee Electron spin resonance studies of Mn<sup>2+</sup>in freshwater snail shells: Pomacea canaliculata lamarck and fossilized snail shell. Chinese Physics Letters. Vol.22, No.7 (2005), 1780-1783. doi:10.1088/0256-307X/22/7/060 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/17180
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Title
Electron spin resonance studies of Mn<sup>2+</sup>in freshwater snail shells: Pomacea canaliculata lamarck and fossilized snail shell
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Abstract
We study paramagnetic Mn2+ions present in the nowadays shells of univalve freshwater snails of Pomacea canaliculata lamarck (PCL) and the fossilized freshwater snail (FFS), Viviparus. All these shells are abundant in Thailand. The PCL shells were ground into fine powder. A set of seven samples were then separately annealed for 2 h in air atmosphere at different annealing temperatures while the FFS powder was characterized as-received. The PCL shells mainly consist of aragonite and a fraction of calcite. The heat treatments of the PCL powder samples at temperature higher than 450 degrees C resulted in an irreversible phase transformation from aragonite to calcite. However, it is found that the FFS shell is mainly made of calcite, with a minor fraction of aragonite. The crystal structure of the high-temperature-annealed PCL samples are quite similar to that of FFS, which indicates that the metamorphosis (aragonite → calcite) in the FFS shell had occurred but was not yet completed, although it had remained under the pressure and temperature of the Earth's crusts over millions of years. Our detailed ESR spectral analyses of PCL and FFS show that Mn2+ions enter the Ca2+sites during a biomineralization process. Simulated ESR parameters of PCL-500 of Mn2+at a uniaxial site of calcite are reported. It is surprising to find that the ratio of Mn2+concentration present in FFS to those in PCL shells evaluated from ESR spectra is as much as 10:1. © 2005 Chinese Physical Society and IOP Publishing Ltd.