ISSN:
1432-0967
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Based on a detailed mineral-chemical investigation of apatite from a series of carbonatites and associated silicate volcanic rocks of the Kaiserstuhl tertiary alkaline volcanic centre, evidence for a new substitution mechanism was found within the hydroxyapatite group, yielding the following simplified formula: (Ca, Sr, LREE)10(SiO4)x(CO3)x(PO4)6−2x(OH, F)2 with 0〈x〈1.2 LREE represents light rare-earth elements such as Ce, La, and Nd. Other elements were detected included Cl, S and traces of Mg, Al, K, Fe, Mn, and Th, however they have no effect on the substitution mechanism found. F is present in varying amounts, although well under half of the total possible halogen content (3.7 wt.% F), and shows a distinct antipathetic concentration correlation with REE and Si (and in turn with C). Charge balance is generally maintained by the coupled substitution of CO 3 2− and SiO 4 4− for PO 4 3− ; however, excess charge may be subsequently adjusted by CO3OH3− partly accompanied by the REE in the Ca site.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374692
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