Apatite parameters

The logarithm of the solubility product for hydroxyapatite is -58.6 and that of fluorapatite (CajtPO jF) is -60.6 (57), and thus, D = 0.01 in favour of fluoride incorporation into the solid apatite precipitate. Accordingly, it should be difficult to prepare solid solutions of these compounds by precipitation from aqueous solution and if prepared batchwise, they are expected to contain logarithmic gradients in their internal composition. Yet, Moreno et al.(M3) report linear changes in the lattice parameters of such solid solutions. They also determined their solubility behavior. 

Fluorapatite (FA) corresponds to the chemical formula Caio(P04)eF2 and crystallises in the hexagonal space group PGs/m, with Z = 1 and unit-cell parameters a = b = 9.367 A and c = 6.884 A [1] (Fig. 2). From a structural viewpoint, fluorapatite is often considered as a crystalline model for other apatites and is seen as a reference apatitic array [2]. It is one of the very first apatite structures to have been solved. It has been thoroughly studied since the 1930s [3] and is well documented in the literature. In particular, Sudarsanan et al. [1] reported the single crystal refinement of X-ray diffraction (XRD) data, and the detailed description of atomic positions and local symmetry is fully available [4,5],... 

The XRD pattern of FA is reported in Fig. 4. It is characteristic of the apatite structure. This pattern is very analogous to that of HA. Fluoride substitution for OH is related to a decrease in the a unit-cell dimension and a very slight increase in the c unit-cell parameter. 

The spectral-kinetic parameters of the green laser-induced luminescence of the sedimentary apatites allow its association with emission. The spectra... 

The spectra of the green laser-induced luminescence represented in Fig. 4.4a, together with their decay time, also allows its association with These luminescence spectra strongly differ from the spectral parameters of all known uranyl minerals. For this reason it is not possible to connect this type of green luminescence with finely dissipated uranyl phases. On the other hand, this luminescence is very similar in such different host minerals as sedimentary apatites, opalites, chalcedony, chert, quartz and barites. Luminescence independence from the minerals structure evidences that it may be connected with uranyl adsorption on the minerals surface, supposedly in the form of (UO2 X nH20)2+. 

The aforementioned DQ technique is well suited to characterize the spatial distributions such as phosphorus nuclei in biomaterials or apatitic systems (vide infra). However, it should be noted that the variation in the parameter A, if any, could be due to a number of factors such as the change in the protonation states and motional dynamics, not necessarily reflecting any change in the second moment. Therefore, 31P DQ NMR is a very useful method in the study of biomineralization but the results should be largely interpreted in a qualitative manner. In principle, the second moment can also be obtained by measuring the attenuation of... 

Figure 24 Chondrite-normalized abundances of REEs in a wall-rock harzburgite from Lherz (dotted lines— whole-rock analyses), compared with numerical experiments of ID porous melt flow, after Bodinier et al. (1990). The harzburgite samples were collected at 25-65 cm from an amphibole-pyroxenite dike. In contrast with the 0-25 cm wall-rock adjacent to the dike, they are devoid of amphibole but contain minute amounts of apatite (Woodland et al., 1996). The strong REE fractionation observed in these samples is explained by chromatographic fractionation due to diffusional exchange of the elements between peridotite minerals and advective interstitial melt (Navon and Stolper, 1987 Vasseur et al, 1991). The results are shown in (a) for variable t t ratio, where t is the duration of the infiltration process and t the time it takes for the melt to percolate throughout the percolation column (Navon and Stolper, 1987). This parameter is proportional to the average melt/rock ratio in the percolation column. In (b), the results are shown for constant f/fc but variable proportion of clinopyroxene at the scale of the studied peridotite slices (<5 cm). All model parameters may be found in Bodinier et al. (1990). As discussed in the text, this model was criticized by Nielson and Wilshire (1993). An improved version taking into account the gradual solidiflcation of melt down the wall-rock thermal gradient and the isotopic variations was recently proposed by Bodinier et al. (2003).

Fitzgerald P. G., Sorkhabi R. B., Redfield T. F., and Stump E. (1995) Uplift and denudation of the central Alaska range a case study in the use of apatite fission track thermochronology to determine absolute uplift parameters. J. Geophys. Res. 100, 20175-20191. 

LeGeros R. Z. (1965) Effect of carbonate on the lattice parameters of apatite. Nature 206, 403 -404. 

The CP kinetics for BRU and various synthetic apatites were measured and interpreted [40,48,49]. We realized [29,40] that the CP behaviour of bone mineral closely matches that of CHA-B, as in both cases there were two, slow and fast-relaxing, clear-cut components of the CP signal. They followed Eq. (1) and Eq. (2), respectively, with similar kinetic parameters for bone mineral and CHA-B. Figure 13 shows the deconvolution of the overall curve A from Fig. 12 into those components, while the fitted CP kinetic parameters are collected in Table 3. In view of these new experimental facts and modified computer fit-... 

Table 19 Unit-cell parameters/A of calcium-rare-earth oxysilicate apatites...

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