Fort Portal碳酸岩磷灰石的某些异常晶体化学特征

对Fort Portal(乌干达)碳酸岩中氟羟碑灰石进行了EMPA，XRD，IR谱和单晶x射线结构精化研究；结果表明：CO3^2-是其中A17a样品的最重要替换组分而其P Si S C原子之和超过四面体位置数，达到6．14，与其高CO3^2-含量相对比，它有很大的晶胞参数a值与很小的c/a值，相对其低一中OH^-与Cl^-含量，它的结构通道直径很大(Ca2-Ca2间距达0．4054nm)。上述异常的晶体化学特征暗示：在该磷灰石中，CO3^2-除替换PO4^3-外，还可能进入结构通道而产生A-B混合型替换．在天热羟磷灰石中可能存在下列类质同像替换机理：CO3^2- Co3^2-=PO4^3- OH^-。

Some Anomalous Crystal-Chemistry Features of the Apatite from the Carbonatite of Fort Portal, Uganda

he F-OH apatite of Fort Portal (Uganda) carbonatite was investigated by EMPA, XRD, IR spectra and X-ray single crystal structure refinement. The results show that CO23- is the most important substituent in sample A17a and its atomic sum of P, Si, S, C is up to 6. 14; The apatite has a high cell constant a (0. 94027nm) and a low c/a (0. 7323) with respect to its high CO2-3 content. Its column dimension is large (Ca2-Ca2 distance is 0. 4054nm) with respect to middle-low OH-and Cl- content. These anomalous features imply that CO2-3 substitutes both PO3-4 and OH-,and the sample presents a CO2-3 A-B type subetitution. In hydroxyapatite mineral there may be a new substitution mechanism: CO2-3+CO2-3=PO3-4+OH-