The suitability of apatite as an age indicator by the uranium-lead isotope method |
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| Authors: | EJ Oosthuyzen AJ Burger |
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| Institution: | 1. Group for Geochronology of the National Physical Research Laboratory, C.S.I.R.,South Africa;2. the Geological Survey of South Africa,South Africa |
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| Abstract: | Experimental data obtained for 14 samples from the granitic terrain surrounding the Barberton Mountain Land in the Republic of South Africa is used to demonstrate that the common accessory mineral, apatite, is suitable for age measurements by the U-Pb isotope method and may in many cases be a more reliable age indicator than the co-existing zircon. The ages calculated for apatite separated from the granitic rocks are in most cases concordant or nearly so (the biggest difference between two uranium-lead ages exhibited being less than 7%); while the ages calculated for co-existing zircon are mostly grossly disconcordant. It is proposed that the theoretical explanation for this observation is found in the crystal chemical stability of the apatite structure as compared to that of zircon. Zircon is probably much more susceptible to loss of members of the U-Pb decay system especially when metamict. |
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