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Secondary Alterations of the Shell Apatite of Discinisca tenuis from Lüderlitz, Namibia

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Abstract

A collection of subfossil specimens of Discinisca tenuis from Lüderlitz, Namibia was studied by means of the X-ray diffraction (XRD) technique. Using the whole-pattern fitting procedure refined by the authors, the unit cell dimensions, crystallite dimensions, and number of strains were detected. Post-mortality alterations in shell apatite are related to mineral component content ranging from 69 to 82% in subfossil shells, as compared to 68% in shells of living species. It has been established that the lattice parameter a decreases from 9.380 to 9.370 Å, while parameter c is less involved during the decomposition of organic matter. The post-mortality alteration is assumed to proceed by the subsequent recrystallization of shell apatite. Consequently, primarily elongated hexagonal prisms (150 × 370 Å) turn to smaller ones (120 × 260 Å), and the number of strains tends to increase.

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  1. Institute of Geology, Tallinn Technical University, Estonia av. 7, Tallinn, Estonia

    Juri Nemliher & Toivo Kallaste

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  1. Juri Nemliher
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  2. Toivo Kallaste
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Nemliher, J., Kallaste, T. Secondary Alterations of the Shell Apatite of Discinisca tenuis from Lüderlitz, Namibia. Lithology and Mineral Resources 37, 18–24 (2002). https://doi.org/10.1023/A:1013679304451

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