ABSTRACT
As an accessory mineral apatite is almost always present in many varieties of magmatic and some metamorphic and metasomatic rocks. In ultramafic rocks the apatites are quite rarely present, more often – in gabbro rocks and very often – in the granitoids and various rocks of heightened alkalinity. Depending on the composition of the anions the apatites are divided into two subgroups: fluorapatites (Ca5[PO4]3F) and chlorapatites (Ca5[PO4]3Cl), and the latter might contain some amount of F, OH and CO3 as anions. It is estimated that in fluorapatites the average contents of the following elements are (wt%): CaO (55.5), P2O5 (42.3), F (3.8), and in chlorapatites – CaO (53.8), P2O5 (41), Cl (6.8). Apatites are able to concentrate in their structure significant amounts of REE, among which the leading role belongs to LREE. In addition to REE there are sometimes Na, Fe, Al and some other elements presented as an impurity [Betekhtin, 1956].
