**7.1.4. Genetic classification of phosphate rocks**

The genetic classification proposed by EGOROV [50] includes three types of apatite ores according to the mineral assemblages [6],[51],[52],[53],[54],[55]:


**Fig. 8.** The location of upper mantle on the cross-section of the Earth, core and mantle drawn to scale [44] (a). Ternary equilibrium phase diagram of the apatite bearing ijolite-urtite rock (b) approximated by the system NaAlSiO4-CaMg‐ Si2O6-Ca5(PO4)3F [6]: olivine (Ol), melilite (Me), silicophosphate (Sph), apatite (Ap) and immiscibility field (L1+L2).

<sup>17</sup> Ijolite, theralite and teschenite belong to phanerites (prelenic rocks characterized by equal or nearly equal amounts of femic components) [55].

<sup>18</sup> Urtite is medium-grained and light gray rock composed of about 70% nephelite, 25% aegirite or aegirite-augite [55].

<sup>19</sup> In the work [58], the name camaforite, i.e. Russian neologism [59], denotes the calcite-magnetite-forsterite assemblage, used as a synonym with phoscorite.

The endogenous apatite deposits can be classified20 into the following types [60],[61]:


**7.1.4. Genetic classification of phosphate rocks**

**i. Silicate-apatite** (**ijolite**<sup>17</sup>

urtite.18

femic components) [55].

used as a synonym with phoscorite.

according to the mineral assemblages [6],[51],[52],[53],[54],[55]:

350 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

**ii. Silicate-magnetite-apatite** (**phoscorite**): phoscorites19

The genetic classification proposed by EGOROV [50] includes three types of apatite ores

composed of nephelite and aegirite-augite, or other pyroxene, in nearly equal proportions. There are varieties richer in nephelite, approaching the composition of

associated with carbonatites, often forming multiphase phoscorite-carbonatite series [56]. The term "phoscorite" was originally used to describe the magnetite-

temperature carbonate melts that have been evolving from the upper mantle (**Fig. 8**) for at least the past 2 Ga. Many are associated with crustal complexes of alkali-rich

olivine-apatite rock with a carbonate core by RUSSELL et al [57],[58],[59].

**iii. Carbonate-apatite** (**carbonatite**): the crystalline products of low-volume and high-

silicate rocks from which they may have evolved by liquid immiscibility.

**Fig. 8.** The location of upper mantle on the cross-section of the Earth, core and mantle drawn to scale [44] (a). Ternary equilibrium phase diagram of the apatite bearing ijolite-urtite rock (b) approximated by the system NaAlSiO4-CaMg‐ Si2O6-Ca5(PO4)3F [6]: olivine (Ol), melilite (Me), silicophosphate (Sph), apatite (Ap) and immiscibility field (L1+L2).

<sup>17</sup> Ijolite, theralite and teschenite belong to phanerites (prelenic rocks characterized by equal or nearly equal amounts of

18 Urtite is medium-grained and light gray rock composed of about 70% nephelite, 25% aegirite or aegirite-augite [55]. <sup>19</sup> In the work [58], the name camaforite, i.e. Russian neologism [59], denotes the calcite-magnetite-forsterite assemblage,

 Nephelite is an equant anhedrons, pyroxene forms euhedral crystals with zonal structure and margin of more sodic pyroxenes than that in the center, which is commonly titaniferous. Some varieties contain titaniferous melanite and iivaarite. Apatite is a prominent constituent and titanate is generally present in small amounts.

): ijolite is a medium- to coarse-grained equigranular rock

are spatially and temporally

	- **Geosynclinal sea**: e.g. in the Late Cretaceous and in Paleogene on the shelf of the Tethys geosyncline with the deposits in Morocco (Khouribga and Youssoufia), Algeria (Djebel Onk, El Kouit), Tunis (Gafsa), of the Permian geosyncline of the Rocky Mountains, with the deposits in the Phosphoria Formation in Idaho, Wyoming, Utah and Montana (USA), of the Caledonian geosyncline Karatau (Russia), large deposits are in the Upper Cretaceous in Kazakhstan, in the neighborhood of Aktyubinsk.
	- **Epicontinental sea**: e.g. in the Cenomanian of the south Russian digression and in the Jurassic of the Moscow region, at the margin of the African Shield in the Eocene complex near Hahotoe (Togo) and Taiba (Senegal), in the upper Cretaceous of Egypt [60].
