Petrogenesis of the Eudialyte Complex of the Lovozero Alkaline Massif (Kola Peninsula, Russia)

minerals

Article Petrogenesis of the Eudialyte Complex of the Lovozero Alkaline Massif (Kola Peninsula, Russia)

Julia A. Mikhailova *, Gregory Yu. Ivanyuk, Andrey O. Kalashnikov , Yakov A. Pakhomovsky, Ayya V. Bazai and Victor N. Yakovenchuk

Kola Science Centre, Russian Academy of Sciences, 14 Fersman Street, Apatity 184209, Russia; [email protected] (G.Y.I.); [email protected] (A.O.K.); [email protected] (Y.A.P.); [email protected] (A.V.B.); [email protected] (V.N.Y.) * Correspondence: [email protected]; Tel.: +7-81555-79333

Received: 2 August 2019; Accepted: 21 September 2019; Published: 25 September 2019

Abstract: The Lovozero Alkaline Massif intruded through the Archaean granite-gneiss and Devonian volcaniclastic rocks about 360 million years ago, and formed a large (20 30 km) laccolith-type body, × rhythmically layered in its lower part (the Layered Complex) and indistinctly layered and enriched in eudialyte-group minerals in its upper part (the Eudialyte Complex). The Eudialyte Complex is composed of two groups of rocks. Among the hypersolvus meso-melanocratic alkaline rocks (mainly malignite, as well as shonkinite, melteigite, and ijolite enriched with the eudialyte-group minerals, EGM), there are lenses of subsolvus leucocratic rocks (foyaite, fine-grained nepheline syenite, urtite with phosphorus mineralization, and primary lovozerite-group minerals). Leucocratic rocks were formed in the process of the fractional crystallization of melanocratic melt enriched in Fe, high field strength elements (HFSE), and halogens. The fractionation of the melanocratic melt proceeded in the direction of an enrichment in nepheline and a decrease in the aegirine content. A similar fractionation path occurs in the Na2O-Al2O3-Fe2O3-SiO2 system, where the melt of the “ijolite” type (approximately 50% of aegirine) evolves towards “phonolitic eutectic” (approximately 10% of aegirine). The temperature of the crystallization of subsolvus leucocratic rocks was about 550 ◦C. Hypersolvus meso-melanocratic rocks were formed at temperatures of 700–350 ◦C, with a gradual transition from an almost anhydrous HFSE-Fe-Cl/F-rich alkaline melt to a Na(Cl, F)-rich water solution. Devonian volcaniclastic rocks underwent metasomatic treatment of varying intensity and survived in the Eudialyte Complex, some remaining unchanged and some turning into nepheline syenites. In these rocks, there are signs of a gradual increase in the intensity of alkaline metasomatism, including a wide variety of zirconium phases. The relatively high fugacity of fluorine favored an early formation of zircon in apo-basalt metasomatites. The ensuing crystallization of aegirine in the metasomatites led to an increase in alkali content relative to silicon and parakeldyshite formation. After that, EGM was formed, under the influence of Ca-rich solutions produced by basalt fenitization.

Keywords: Lovozero Alkaline Massif; fractional crystallization; fenitization; nepheline; alkali feldspar; clinopyroxene; amphibole; eudialyte

1. Introduction Alkaline igneous rocks are among the rarest magmatic rocks. These rocks contain either (1) modal feldspathoids or alkali amphiboles or pyroxenes or (2) normative feldspathoids or aegirine [1]. Based on the molar ratios of Na2O, K2O, and CaO relative to Al2O3, these rocks can be subdivided into metaluminous {(Na2O + K2O) < Al2O3 < (Na2O + K2O + CaO)}, peraluminous {Al2O3 > (Na2O + K2O + CaO)} and peralkaline {(Na2O + K2O) > Al2O3} types [2].

Minerals 2019, 9, 581; doi:10.3390/min9100581 www.mdpi.com/journal/minerals Minerals 2019, 9, 581 2 of 31

Alkaline rocks are extraordinary rich in large ion lithophile elements (LILE), such as Na and K, and in high field strength elements (HFSE), such as Ti, Zr, Hf, Nb, Ta, rare-earth elements (REE), U and Th, forming economically important deposits of these elements [3,4]. Primary magmatic minerals of HFSE in alkaline rocks form two main mineral associations. Minerals with relatively simple crystal structures (in terms of topological complexity of crystal structures [5]), such as zircon/baddeleyite and titanite/perovskite, ilmenite and titanomagnetite (depending on the SiO2 activity), which belong to the miaskite association [3]. Complex Na-Ca-HFSE-REE silicates (e.g., minerals of the eudialyte group, rinkite, aenigmatite, lamprophyllite, astrophyllite, etc.) form agpaitic assemblages. Hyperagpaitic assemblages include ussingite, naujakasite, steenstrupine-(Ce), members of the lovozerite and lomonosovite groups, and partly water-soluble minerals (e.g., villiaumite, natrosilite, natrophosphate, and thermonatrite). Transitional agpaitic rocks contain HFSE minerals that are typical of all three types of alkaline rocks (for example, titanite and eudialyte or eudialyte and lovozerite). The field occurrence of agpaitic rocks is variable. The Lovozero Alkaline Massif, together with the nearby Khibiny Massif and the Ilímaussaq Complex of Greenland, is one of the sites with the world’s largest occurrences of agpaitic nepheline syenite intrusions. The causes of the enrichment of agpaitic rocks in HFSE and REE are studied in detail. Agpaitic nepheline syenites form by extensive differentiation of parental mafic magmas at low oxygen fugacity [6]. Such conditions determine the presence of CH4-rich fluids [7–9] instead of H2O–CO2 fluid mixtures typical of less reduced rock types. Since Na, Cl, and F are well soluble in water, these elements do not pass into the fluid, but remain in the melt [10,11]. In addition, the chlorine fluid/melt partition coefficient decreases with growth of fluorine content, and vice versa [10]. As HFSE and REE have high solubilities in Na-, Cl- and F-rich melts [12,13], they will eventually form agpaitic minerals such as the eudialyte-group minerals (EGM), rinkite, aenigmatite, (baryto)lamprophyllite and astrophyllite. Agpaitic rocks can be extremely rich in EGM; for example, the upper part of the Lovozero Massif is composed of alkaline rocks with rock-forming EGM (up to 90 mod. %), due to which it received the name of “the Eudialyte Complex” [14]. The EGM-rich rocks are represented here by foid syenite, foidolite, and alkaline metasomatite and pegmatite. In this article, based on the petrography of these rocks and data on the chemical composition of rock-forming minerals, we present estimations of conditions and mechanisms of the Lovozero “Eudialyte Complex” formation.

2. Geological Setting The laccolith-type Lovozero Alkaline Massif was emplaced 360–370 million years ago [15–17] into Archean granite gneisses covered by Devonian volcaniclastic rocks [18]. According to geophysical studies [19], alkaline rocks are traced to a depth of 7 km, the lower limit of their distribution is not detected. The laccolith has a size 20 30 km on the day surface, and about 12 16 km on a 5 km × × depth [14]. In the upper part, the intrusion contacts with host rocks are almost vertical. On the plane, the massif has the shape of a quadrilateral with rounded corners (Figure1a). The Lovozero Massif is a layered intrusion composed of two macro units: the Eudialyte Complex and the Layered Complex. The Eudialyte Complex is located at the top of the massif, accounts for 18% of its volume and is not layered. The Layered Complex, with the layering clearly manifested, occupies 77% of the volume of the massif. The elementary unit of layering here is a sequence (“rhythm” or “pack”) of alkaline rocks (from the bottom up): urtite–foyaite–lujavrite (Figure1b,c). In this series, there is a gradual transition from almost monomineral nepheline or nepheline-kalsilite foidolite (urtite) to leucocratic nepheline ( sodalite) syenite (foyaite), and then to lujavrite (meso- ± and melanocratic nepheline syenite of the malignite–shonkinite rock series). The textures of these rocks change from massive in urtite to semi-trachytoid in foyaitеand trachytoid in lujavrite due to the gradual ordering of the feldspar plates. The sequence urtite–foyaite–lujavrite is repeated regularly [14,20]. The contact between the underlying lujavrite and the overlying urtite is sharp and marked by rich loparite impregnation in both nepheline syenite and foidolite (50–80 cm thick loparite maligite–ijolite ore-horizons [21,22]). The thickness of the individual rhythm is 5 to 100 m-they lie Minerals 2019, 9, 581 3 of 31

sub-horizontallyMinerals 2017, 7, x FOR (the PEER dip REVIEW is 5–15 ◦ towards the center of the massif) and have nearly uniform3 of thickness.32 The rhythms of the Layered Complex are combined into seven series, denoted by Roman numerals, andthickness. the series, The inrhythms turn, of are the grouped Layered Complex into three are zones. combined The into upper seven zone series, (up denoted to 370 by m)Roman consists of packsnumerals, of urtite–foyaite–lujavrite. and the series, in turn, are The grouped middle into zone, three withzones. a The thickness upper zone of 640–670 (up to 370 m, m) is consists composed of monotonousof packs of urtite–foyaite–lujavrite. lujavrite with sparse The interlayers middle zone of foyaite., with a Thethickness lower of zone640–670 consists m, is composed predominantly of of foyaite-lujavritemonotonous lujavrite packs [with14]. sparse The boundaries interlayers ofof thefoyaite. zones The are lower the urtitezone consists horizons predominantly II (series) -5 of (rhythm) foyaite-lujavrite packs [14]. The boundaries of the zones are the urtite horizons II (series) -5 (rhythm) and III-1 (Figure1c). and III-1 (Figure 1c).

Figure 1. The geology of the Lovozero Alkaline Massif: schematic geological map, after [20] (a) and Figure 1. The geology of the Lovozero Alkaline Massif: schematic geological map, after [20](a) and stratigraphic column [14] (b), with principal scheme of layering [21] (c). stratigraphic column [14](b), with principal scheme of layering [21](c). Other rock types of the Lovozero Massif are subordinate to their layering and form sub- Other rock types of the Lovozero Massif are subordinate to their layering and form sub-horizontal horizontal layers or lenses in the Eudialyte Complex and the Layered Complex (Figure 1a). Xenoliths layersof volcaniclastic or lenses in the rocks Eudialyte are ubiquitous. Complex Unchanged and the Layered xenoliths Complex are composed (Figure1 a).of interbeddedXenoliths of olivine volcaniclastic rocksbasalts, are ubiquitous.basalt tuffs, tuffites, Unchanged sandstones, xenoliths and quartzites. are composed However, of interbedded usually these olivinelithologies basalts, are deeply basalt tuffs, tuffimetasomatizedtes, sandstones, [18]. and Numerous quartzites. lenses However, of poikilitic usually nepheline these and lithologies sodalite-nepheline are deeply (sometimes metasomatized with [18]. Numerousnosean) syenite, lenses ofas poikiliticwell as alkaline nepheline pegmatites and sodalite-nepheline and hydrothermal (sometimes veins, are located with nosean) within syenite,the as welleudialyte as alkaline and layered pegmatites complexes and [23–25]. hydrothermal veins, are located within the eudialyte and layered complexesThe thickness [23–25]. of the Eudialyte Complex in different parts of the massif ranges from 100 to 800 m.The According thickness to [14,20], of the EudialyteZr-rich melts Complex break th inrough different and partsoverlap of the the previously massif ranges formed from Layered 100 to 800 m. Complex. The cutting of the upper rhythms of the urtite–foyaite–lujavrite is visible; the plane of the According to [14,20], Zr-rich melts break through and overlap the previously formed Layered Complex. contact of the complexes falls to the center of the massif, with the angle of dip increasing in the same Thedirection cutting from of the 10 upper° to 40° rhythms. In fact, the of Eudialyte the urtite–foyaite–lujavrite Complex can be regarded is visible; as part the of plane the giant of the Lovozero contact of the complexesEudialyte falls Deposit to the that center includes of the several massif, rich with site thes, in angle particular, of dip the increasing Karnasurt, in theKedykvyrpakhk, same direction from 10 toAlluaiv, 40◦. In Angvundaschorr, fact, the Eudialyte Sengischorr Complex and can Parguaiv be regarded sites, asand part the of Alluaiv the giant site Lovozerois the best explored Eudialyte of Deposit thatthem includes [4]. several rich sites, in particular, the Karnasurt, Kedykvyrpakhk, Alluaiv, Angvundaschorr, Sengischorr and Parguaiv sites, and the Alluaiv site is the best explored of them [4]. 3. Materials and Methods 3. MaterialsAs the and Alluaiv Methods site (Figure 2) is the best explored, it was chosen for detailed study of the EudialyteAs the AlluaivComplex, site whose (Figure thickness2) is the varies best here explored, from 280 it to was 350 chosen m. There for is detailed a wide diversity study of of the EGM- Eudialyte Complex, whose thickness varies here from 280 to 350 m. There is a wide diversity of EGM-rich Minerals 2019, 9, 581 4 of 31 Minerals 2017, 7, x FOR PEER REVIEW 4 of 32 alkalinerich alkaline rocks–a rocks–a dense dense drillgrid drill and grid numerous and numero outcropsus outcrops display display the rock the relations rock relations and their and contacts their withcontacts the underlyingwith the underlying rocks of the rocks Layered of the Complex. Layered Complex. As a whole, As wea whole, used 275we thinused polished 275 thin sectionspolished of rockssections selected of rocks from selected cores offrom 27 explorationcores of 27 exploration boreholes and boreholes the day and surface the day (Figure surface2a). (Figure 2a).

Figure 2. The Alluaiv site of the Lovozero Eudialyte Deposit (see Figure1a): ( a)—scheme of drill Figure 2. The Alluaiv site of the Lovozero Eudialyte Deposit (see Figure 1a): (а)—scheme of drill holes; holes; (b)—the modal composition of alkaline rocks of the Alluaiv site. Rocks with fine-grained (blue (b)—the modal composition of alkaline rocks of the Alluaiv site. Rocks with fine-grained (blue diamonds), metasomatic (green triangles) and poikilitic (red triangles) textures are highlighted with diamonds), metasomatic (green triangles) and poikilitic (red triangles) textures are highlighted with special icons; (c)—section along the I–II line (see Figure2a). The rock legend corresponds to Figure2b. special icons; (с)—section along the I–II line (see Figure 2а). The rock legend corresponds to Figure Rock with fine-grained, metasomatic, and poikilitic textures are highlighted by hatching. 2b. Rock with fine-grained, metasomatic, and poikilitic textures are highlighted by hatching. The thin polished sections were analyzed using the scanning electron microscope LEO-1450 The thin polished sections were analyzed using the scanning electron microscope LEO-1450 (Carl Zeiss Microscopy, Oberkochen, Germany), with energy-dispersive microanalyzer Röntek to (Carl Zeiss Microscopy, Oberkochen, Germany), with energy-dispersive microanalyzer Röntek to obtain BSE (Back Scattered Electron) images and pre-analyze all detected minerals. The chemical obtain BSE (Back Scattered Electron) images and pre-analyze all detected minerals. The chemical composition of rock-forming minerals was analyzed with a Cameca MS-46 electron microprobe composition of rock-forming minerals was analyzed with a Cameca MS-46 electron microprobe (Cameca, Gennevilliers, France) operating in WDS-mode at 22 kV with beam diameter 10 µm, beam (Cameca, Gennevilliers, France) operating in WDS-mode at 22 kV with beam diameter 10 µm, beam current 20–40 nA and counting times 20 s (for a peak) and 2 10 s (for background before and after the current 20–40 nA and counting times 20 s (for a peak) and ×2 × 10 s (for background before and after peak), with 5–10 counts for every element in each point. The analytical precision (reproducibility) of the peak), with 5–10 counts for every element in each point. The analytical precision (reproducibility) mineral analyses is 0.2–0.05 wt. % (2 standard deviations) for the major element and about 0.01 wt. % of mineral analyses is 0.2–0.05 wt. % (2 standard deviations) for the major element and about 0.01 wt. for impurities. The standards used, the detection limits, and the analytical accuracy values are given in % for impurities. The standards used, the detection limits, and the analytical accuracy values are Table S1 in Supplementary Materials. The systematic errors were within the random errors. given in Table S1 in Supplementary Materials. The systematic errors were within the random errors. Major elements in rocks were determined by a wet chemical analysis in the Geological Institute Major elements in rocks were determined by a wet chemical analysis in the Geological Institute ofof KSCKSC RAS.RAS. TheThe accuracyaccuracy limits of the wet chemical analysis analysis are are given given in in Table Table S1 S1 (Supplementary (Supplementary Materials).Materials). CationCation contentscontents were were calculated calculated using using the the MINAL MINAL program program of D.of Dolivo-DobrovolskyD. Dolivo-Dobrovolsky [26 ]. The[26]. amphibole-group The amphibole-group mineral mineral formulae formulae were were calculated calculated based based on on O O+ +OH OH+ + FF = 2424 atoms atoms per per formulaformula unitunit andand OHOH == 2 –– 2Ti.2Ti. The formula calculation calculation was was performed performed following following the the IMA IMA 2012 2012 recommendationsrecommendations [[27]27] usingusing thethe ExcelExcel spreadsheet of Locock [28]. [28]. Statistical Statistical analyses analyses were were carried carried outout usingusing thethe STATISTICASTATISTICA 1313 [[29]29] andand TableCurveTableCurve 2.02.0 [[30]30] programs.programs. For For the the statistics, statistics, resulting resulting values of the analyses below the limit of accuracy (see Table S1 in Supplementary Materials) were Minerals 2019, 9, 581 5 of 31 values of the analyses below the limit of accuracy (see Table S1 in Supplementary Materials) were considered ten times lower than the limit. Geostatisical studies and 3D modeling were conducted with the MICROMINE 16.1 program (Micromine Pty Ltd., Perth, Australia). Interpolation was performed by ordinary kriging. The ImageJ program (US National Institutes of Health) was used to generate digital images from the thin polished sections images and determinate modal proportion of rock-forming minerals. The mineral abbreviation used include Aeg—aegirine-(augite), Ab—albite, All—alluaivite, Ap—fluorapatite, Aq—aqualite, Di—diopside, Eud—minerals of eudialyte group (EGM), Fo—forsterite, Ilm—ilmenite, Kap—kapustinite, Kent—kentbrooksite, Ks—kalsilite, Lmp—lamprophillite, Lom—lomonosovite, Lop—loparite, Mag—magnetite, Marf—magnesioarfvedsonite, Mc—microcline (-perthite), Nph—nepheline, Ntr—natrolite, On—oneillite, Or—orthoclase, Phl—phlogopite, Pkl—parakeldyshite, Prv—perovskite, Ras—raslakite, Rct—richterite, Sdl—sodalite, Sp—sphalerite, Tas—taseqite, Ttn—titanite, Umb—umbozerite, Zir—zirsilite.

4. Results

4.1. Petrography The basis of the petrographic classification of plutonic alkaline rocks of the Alluaiv site is the QAPF (Q—quartz, A—alkali feldspar, P—plagioclase, F—feldspathoid) classification of the International Union of Geological Sciences [1], which takes into account the ratio of K-Na feldspar (A), feldspathoids (F) and mafic minerals (color index M0) in the rock (Table S2 in Supplementary Materials). Within the AFM0 triangle, the rock points are located mainly in the center, do not form isolated groups and are divided into foid syenite (shonkinite, malignite and foyaite) and foidolite (melteigite, ijolite and urtite) (Figure2b). The most common rocks of the Alluaiv site are coarse- to medium-grained trachytoid malignites (Figure2b,c and Figure3a). In these rocks, euhedral plates of microcline-perthite are oriented subparallel one to another. The feldspar crystals have the most intensely developed faces of pinacoid (010), are elongated along [001] up to 3 cm, with the average side ratio a:b:c = 6:1:10 (data on 82 crystals). Microcline-perthite crystals are often slightly bent and fractured. Albites concentrate usually around the fractures (Figure3b), making them well visible under the microscope. In addition, small albite perthites are evenly distributed within microcline crystals. In sections perpendicular to the pinacoid (010), albite occupies 5% to 37% (median is 17%) of the microcline-perthite grain. As a rule, the albite is intensively replaced by natrolite (Figure3b,d). Feldspathoids fill interstices between the microcline-perthite plates. The most common of them, nepheline, forms grains of two morphological types. Nepheline-I occurs as euhedral crystals with numerous small inclusions of aegirine and microcline (Figure3a,c). Aegirine inclusions are presented by randomly oriented short-prismatic crystals (up to 200 µm long), long-prismatic crystals (up to 600 µm long) oriented parallel to nepheline grain faces, as well as irregular intergrowths of small needles (on average 3 8 µm). Nepheline-II forms lens-like anhedral grains with small inclusions of × aegirine-(augite) on the periphery (Figure3b). Sodalite and natrolite, except for pseudomorphs after nepheline (Figure3c) and albite (Figure3d), form primary grains, similar in morphology to nepheline-II and coexisting with it. Inside the grains of primary sodalite, natrolite or natrolite–sodalite aggregates occur (Figure3d). Primary natrolite often contains numerous small (up to 20 µm) boehmite inclusions. The feldspar and feldspathoid grains are surrounded by “streams” of subparallel-oriented crystals of mafic minerals (Figure3a–f), represented by alkaline clinopyroxenes (aegirine and aegirine-augite) and amphiboles (mainly magnesioarfvedsonite), as well as lamprophyllite. The marginal parts of the “streams” consist of small (50 200 µm in the average) long-prismatic clinopyroxene crystals, × and the axial zones is composed of larger anhedral amphibole grains (Figure3b–d). The edge parts of the amphibole crystals usually contain clinopyroxene inclusions oriented according to the general Minerals 2019, 9, 581 6 of 31 direction of the “stream”. Lamprophyllite forms either poikilitic crystals (Figure3c) or individual plates (Figure3d) located between grains of clinopyroxenes and amphiboles. Minerals 2017, 7, x FOR PEER REVIEW 6 of 32

Figure 3. Meso-melanocratic rocks of the Alluaiv site: (а)—EGM-rich trachytoid malignite (lujavrite) Figure 3. Meso-melanocratic rocks of the Alluaiv site: (a)—EGM-rich trachytoid malignite (lujavrite) 117117/76/76 (photo ofof polishedpolished thinthin sectionsection inin transmittedtransmitted light);light); (b–d)—BSE images of EGM-richEGM-rich malignites (lujavrites) 117117/121/121 (b), 154/85 154/85 ( c) and 29/37 29/37 ( d);); ( (ee)—BSE-image)—BSE-image of of EGM-rich EGM-rich ijolite ijolite 222/177; 222/177; (f)—BSE-image of shonkinite 3232/42.4./42.4.

Interstices between grains of above-mentioned mafic minerals of the “streams” are filled with natrolite. If the proportion of natrolite is large, clinopyroxenes and amphiboles form euhedral short- prismatic crystals (Figure 3c). Similar to amphiboles, EGM grains are in the axial parts of the “streams”. They usually form rounded or lenticular grains (in the average, 2.3 mm in diameter), while their euhedral crystals (up to 7 mm long) with rhombic prismatic and rhombohedral faces occur much more rarely. The marginal parts (up to 200 µm) of EGM grains are saturated with inclusions of Minerals 2019, 9, 581 7 of 31

Interstices between grains of above-mentioned mafic minerals of the “streams” are filled with natrolite. If the proportion of natrolite is large, clinopyroxenes and amphiboles form euhedral short-prismatic crystals (Figure3c). Similar to amphiboles, EGM grains are in the axial parts of the “streams”. They usually form rounded or lenticular grains (in the average, 2.3 mm in diameter), while their euhedral crystals (up to 7 mm long) with rhombic prismatic and rhombohedral faces occur much more rarely. The marginal parts (up to 200 µm) of EGM grains are saturated with inclusions of aegirine-(augite) and, in smaller quantities, magnesioarfvedsonite. The inclusions are oriented according to the general direction of the “stream” (Figure3b–d). The length of common boundaries between EGM and clinopyroxene + amphibole grains significantly exceeds that between EGM and leucocratic minerals (9:1 ratio). The accessory minerals of malignite are in the interstices between clinopyroxene and amphibole crystals. The most common (found in more than 50% of samples) accessory minerals include the perovskite group minerals (loparite, lueshite), sulfides (sphalerite, pyrrhotite, chalcopyrite), stronadelphite, pyrochlore group minerals, baritolamprophillite, chlorbartonite, thorite, and thorianite. Arsenopyrite, löllingite, cobaltine, lorenzenite, and rinkite are less common. Secondary minerals are presented by lovozerite (after EGM), rhabdophane-(La/Ce), bastnaesite-(Ce), strontianite, barite, witherite, hanneshite, and cerussite. With an increase of feldspathoid content at the expense of microcline-perthite, the malignite transits to ijolite (Figure3e). The trachytoid texture is lost in this case, but the “streams” of mafic minerals remain, which are now oriented arbitrarily. In this rock, there are also two morphological types of nepheline, primary natrolite and primary sodalite with natrolite cores. Again, EGM form here rounded, oval, or irregularly shaped grains with aegirine-(augite) inclusions on the periphery. Less widespread are well-formed EGM crystals and their poikilitic grains within aegirine-(augite) segregations. An increase in the total content of mafic minerals in malignite, with its formal transition to shonkinite (Figures2b and3f), results from an increase in the EGM proportion. At the same time, the content of all mafic minerals excluding EGM (i.e., M’ minus EGM, modal %) never exceeds 34–38 modal %. The average EGM content in shonkinites is 22.4 modal %. In fact, there are no differences between malignite and shonkinite besides EGM contents. With a decrease in total content of mafic minerals (including EGM), mesocratic rocks (malignite and ijolite) turn into foyaite or, with an increase in the proportion of feldspathoids, into urtite (Figure4a). Both these transitions are gradual, occur in narrow (1–3 cm) intervals and result in rock texture isotropization. The next important change is the appearance of primary albite (Figure4a), which increases the total content of this mineral to 29 modal %. In foyaite and urtite, mafic minerals do not form a communicating system of “streams”: fine-grained aggregates of prismatic aegirine-(augite) and rounded EGM grains fill interstices between microcline-perthite, albite and nepheline grains (Figure4a), while amphiboles form poikilitic crystals. When the color index M’ of the rock decreases (apart from amphiboles) first clinopyroxenes and then EGM form poikilitic crystals. Nepheline forms euhedral crystals with or without inclusions of microcline and aegirine. Natrolite replaces nepheline also forms primary grains in association with unchanged nepheline. Primary sodalite is present too. The set of accessory minerals in foyaite and urtite is similar to that in malignite, but phosphorus-rich minerals are much more widely spread in the leucocratic rocks. Stronadelphite, fluorapatite, lomonosovite (Figure4b), vuonnemite, bornemanite, monazite-(Ce), xenotime-(Y), nastrophite and nabaphite are characteristic of these rocks as well as lovozerite-group minerals (lovozerite, kapustinite, litvinskite). The latter not only replace EGM, but also occur as primary minerals (Figure4d). Fine-grained nepheline syenite constitutes a significant part of the studied samples (Figure2b). The basis of their texture is formed by euhedral albite crystals (up to 32 modal %; in the average, 25 modal %). Between the albite crystals, anhedral grains of microcline (without perthites) and nepheline occur. Aegirine(-augite) forms prismatic crystals, which are either uniformly dispersed Minerals 2019, 9, 581 8 of 31 in the rock or form small lenses in aggregates of leucocratic minerals. Rounded grains of EGM are uniformly disseminated in the rock (Figure4c,d). Minerals 2017, 7, x FOR PEER REVIEW 8 of 32

Figure 4. Leucocratic rocks of the Alluaiv site: (a)—BSE-image of urtite 117/208; (b)—BSE-image of Figure 4. Leucocratic rocks of the Alluaiv site: (a)—BSE-image of urtite 117/208; (b)—BSE-image of foyaite 154/300; (c)—BSE-image of fine-grained foyaite 157/36; (d)—BSE-image of kapustinite-rich foyaite 154/300; (c)—BSE-image of fine-grained foyaite 157/36; (d)—BSE-image of kapustinite-rich fine-grained foyaite 32/243; (e,f)—images in transmitted light of polished thin sections of porphyry fine-grained foyaite 32/243; (e,f)—images in transmitted light of polished thin sections of porphyry foyaite 154/253 (e); contact of fine-grained foyaite (below) and urtite 154/216 (f); vein of fine-grained foyaite 154/253 (e); contact of fine-grained foyaite (below) and urtite 154/216 (f); vein of fine-grained foyaite in malignite 157/36 (g). foyaite in malignite 157/36 (g).

Minerals 2019, 9, 581 9 of 31

In terms of modal composition, most samples of fine-grained nepheline syenite correspond to foyaite (Figure2b); the transition to malignite and shonkinite occurs due to the appearance of poikilitic crystals of (magnesio)arfvedsonite (Figure4g), murmanite, lomonosovite, the lovozerite-group minerals, and lamprophyllite. Microcline-perthite and nepheline form large phenocrysts (content up to 40 modal %, size up to 1 cm) in fine-grained mass (Figure4c,e–g). In the narrow (up to 100 µm) marginal zone of the phenocrysts, there are small inclusions of aegirine(-augite) and EGM oriented usually subparallel to the phenocryst faces (Figure4c). With an increase in the content of microcline-perthite and /or nepheline phenocrysts, fine-grained nepheline syenite transforms into medium- to coarse-grained foyaite or urtite (Figure4f). It should be noted that the co-existence of primary lovozerite-group minerals and unchanged EGM is characteristic of fine-grained nepheline syenite. Lovozerite-group minerals form either small rounded grains (Figure4d) or large poikilitic crystals. Usually, the contact between fine-grained nepheline syenite and malignite is sharp and concordant with orientation of microcline plates in the malignite, i.e., trachytoid plane. In fine-grained rock, long-prismatic clinopyroxene crystals and albite plates are also co-oriented with the contact (Figure4g). Fine-grained nepheline syenite form various lens-like bodies (5 mm to 100 m thick, Figures2c and4g) among the coarse- and medium-grained rocks of the Eudialyte Complex. Comparatively fresh olivine basalt is a rare rock of the Alluaiv site (Figures2c and5a,b). In this rock, forsterite crystals (up to 1.3 mm wide), phlogopite (up to 0.6 mm in diameter) and diopside/augite (up to 0.8 mm wide) are disseminated into the main fine-grained diopside (augite)-phlogopite mass (the average size of individual grains is about 30 µm). Often, diopside (augite) grains are resorbed by phlogopite, and forsterite is serpentinized. Magnetite forms skeletal crystals and small (8 µm on the average) rounded grains, perovskite constitutes chains of cubic crystals, and fluorite, fluorapatite and pectolite are located within phlogopite-diopside (augite) aggregate and inside the skeletal magnetite crystals. Accessory minerals are barite, djerfisherite, and pyrrhotite. High-temperature fenitization of olivine basalt and its tuff produced numerous metasomatic rocks [18], up to formation of fine- to medium-grained nepheline syenites with relics of earlier minerals and metasomatic textures. Rocks that modally correspond to foyaite and urtite but have a metasomatic texture, are highlighted in Figure2b separately. They form inclined layers (Figure2c) and small individual lenses in the Eudialyte Complex and consist mainly of large orthoclase crystals, which can be both homogeneous and perthite-bearing. Orthoclase is intensively resorbed by nepheline that often includes small irregularly shaped orthoclase relics (Figure5c). Moreover, nepheline forms large (up to 1 cm) euhedral crystals that contain magnesioarfvedsonite inclusions and symplectic intergrowths (Figure5c,d) and are rimmed by aegirine. Also, in this rock, there is a large number of resorbed augite relics surrounded by zonal rims of richterite, ferri-katophorite and eckermannite), then aegirine-augite and marginal aegirine. In addition to these rims, aegirine occurs as fan-shaped aggregates among orthoclase-perthite and nepheline. Characteristic accessory minerals located mainly among aegirine include parakeldyshite, titanite, ilmenite, zircon, baddeleyite, fluorapatite, and EGM. These minerals usually form various zonal segregations (Figure5d): zircon + baddeleyite (inside)–parakeldyshite (outside), parakeldyshite (inside)–EGM (outside), titanite + fluorapatite (inside)–EGM (outside); ilmenite (inside)–titanite (outside). The rocks with poikilitic texture (Figure2b) correspond modally to feldspar-bearing urtite consisting of large (up to 8 cm in diameter) orthoclase crystals with numerous inclusions of sodalite, natrolite and nepheline (Figure5e,f). Aegirine(-augite) is the main mafic mineral, but its content does not exceed 18 modal %. EGM form rare poikilitic crystals with inclusions of surrounding minerals. Such rocks are rare (1% of the studied samples) and were found only in one drill hole (154, interval 999–931 m). Minerals 2019, 9, 581 10 of 31

Minerals 2017, 7, x FOR PEER REVIEW 10 of 32

Figure 5. Olivine basalt and products of its deep metasomatic alteration (a–d): photo in transmitted Figure 5. Olivine basalt and products of its deep metasomatic alteration (a–d): photo in transmitted light (a) and BSE-image (b) of polished thin section of olivine basalt 160/130; orthoclase-rich light (a) and BSE-image (b) of polished thin section of olivine basalt 160/130; orthoclase-rich metasomatic metasomatic rocks 156/66 (c) and 156/98 (d). Poikilitic urtite 154/153: photo in transmitted light (e) rocks 156/66 (c) and 156/98 (d). Poikilitic urtite 154/153: photo in transmitted light (e) and BSE-image (f). and BSE-image (f). 4.2. Whole-Rock Chemistry

Data on the concentrations of petrogenic elements in rocks of the Lovozero Eudialyte Complex are shown in Figure6 and in Table S3 (Supplementary Materials). The most important changes in Minerals 2017, 7, x FOR PEER REVIEW 11 of 32

4.2.Minerals Whole-Rock2019, 9, 581 Chemistry 11 of 31 Data on the concentrations of petrogenic elements in rocks of the Lovozero Eudialyte Complex arethe shown chemical in compositionFigure 6 and ofin rocksTable occurS3 (Supplementa with an increasery Materials). in the proportion The most ofimportant maﬁc minerals changes in in their the chemicalcomposition. composition During theof rocks transitions occur fromwith an foyaite increase to malignite in the proportion and from of urtite mafic to minerals ijolite, when in their the composition. During the transitions from foyaite to malignite and from urtite to ijolite, when the color color index M’ exceeds 30% (Figure2b), content of Al 2O3 in the rock composition gradually decreases, index M’ exceeds 30% (Figure 2b), content of Al2O3 in the rock composition gradually decreases, while while the contents of Na2O and K2O do not change. This leads to the predominance of the sum of the contents of Na2O and K2O do not change. This leads to the predominance of the sum of these these alkalis over aluminum. The proportion of samples with Ka = (Na2O + K2O)/Al2O3 > 1 (agpaitic alkalis over aluminum. The proportion of samples with Ka = (Na2O + K2O)/Al2O3 > 1 (agpaitic coeﬃcient) among the malignite, ijolite and shonkinite is 48%. As concentrations of ZrO2, TiO2, Fe2O3, coefficient) among the malignite, ijolite and shonkinite is 48%. As concentrations of ZrO2, TiO2, Fe2O3, MnO, MgO and SrO increase with Ka growth (Figure7) at the expense of P 2O5, the more melanocratic MnO, MgO and SrO increase with Ka growth (Figure 7) at the expense of P2O5, the more melanocratic rocks are EGM-richer and phosphate-poorer. rocks are EGM-richer and phosphate-poorer.

Figure 6. Variations inin thethe chemical chemical composition composition of of rocks rocks of of the the Alluaiv Alluaiv site. site. The The rocks rocks are dividedare divided into

intotwo two groups groups by the by value the valueKa = K(Naa = 2(NaO +2OK +2 O)K2/O)/AlAl2O32O. Red3. Red arrows arrows show show the the median median contents. contents. Minerals 2019, 9, 581 12 of 31

Minerals 2017, 7, x FOR PEER REVIEW 12 of 32

Figure 7. Content of ZrO2 in rocks as a function of their agpaitic coefficient, Ka. Figure 7. Content of ZrO2 in rocks as a function of their agpaitic coeﬃcient, Ka.

The composition ofof ﬁne-grainedfine-grained nepheline nepheline syenite syenite is is generally generally similar similar to to that that of foyaites,of foyaites, except except for forCaO CaO and and Fe2O Fe3,2O whose3, whose content content in ﬁne-grained in fine-grained rocks rocks is higher. is higher. Urtite Urtite is relatively is relatively rich in rich Al2O in3, Al Na2O2O,3, Naand2O, Cl, and but itCl, contains but it thecontains smallest the amounts smallest of amounts divalent of cations, divalent TiO 2cations,,K2O, and TiO SiO2, K2.2O, Metasomatic and SiO2. Metasomaticrocks have the rocks highest have concentrations the highest concentrations of P2O5; their CaOof P2 andO5; their MgO CaO contents and areMgO the contents highest are among the highestleucocratic among rocks leucocratic (Figure6). rocks (Figure 6).

4.3. Mineral Mineral Chemistry Chemistry

4.3.1. Alkali Alkali Feldspars Feldspars Representative analysesanalyses ofof alkalialkalifeldspars feldspars are are presented presented in in Table Table1, and1, and all all analyses analyses are are in Tablein Table S4 (SupplementaryS4 (Supplementary Materials). Materials). The compositions of alkali feldspar of coarse- and medium-grained rocks do not depend on Table 1. Representative microprobe analyses of alkali feldspar, wt. %. whether or not a primary (not perthitic) albite is present in the rock. In any case, alkali feldspar is exsolved into pure albite and microcline,Shonkinite, whose composition is Or94–99AbFine-Grained1–6 (lines 3–7 Metasomaticin Figure 8a) Rock Malignite Ijolite Foyaite Urtite with permanent impurities of Fe (up toMelteigite 0.01 apfu) and Ba (up to 0.01 apfu).Nph-Syenite Rock Drill hole 29 117 153 160 153 222 154 224 117 147 160 157 156 156 Deep, m 37.5Table 102 1. 143 Representative 120 36 microprobe 123 271 analys 102es of 208alkali feldspar, 85 172 wt. %. 36 77 * 77 **

SiO2 63.98 64.90 65.32 65.88Shonkinite, 65.28 65.08 64.24 65.14 63.92 65.74 65.53Fine-Grained 63.80 64.98 Metasomatic 64.40 Rock Malignite Ijolite Foyaite Urtite Al2O3 16.95 18.04 18.32 18.43 17.34Melteigite 18.03 18.38 18.33 17.88 18.18 17.61Nph-Syenite 17.54 19.62 19.15Rock Fe O 0.05 0.06 b.d. 0.03 b.d. 0.09 0.02 0.04 b.d. 0.08 0.51 0.65 0.38 0.45 Drill 2 3 BaO29 0.14 117 b.d. 153 b.d. 160 b.d. 153 b.d. 0.12222 b.d.154 0.08 224 0.13 117 b.d. 147 0.12 160b.d. 157 1.60156 1.32 156 hole Na2O 0.30 0.26 0.35 0.38 0.30 0.32 0.43 0.34 0.39 0.39 1.74 0.64 5.00 4.41 Deep, m 37.5 102 143 120 36 123 271 102 208 85 172 36 77 * 77 ** K2O 16.72 16.19 16.43 15.89 16.89 16.32 16.15 16.07 16.04 16.20 14.05 15.72 6.75 7.52 SiO2 Sum 63.98 98.1464.90 99.45 65.32 100.42 65.88 100.61 65.28 99.81 65.08 99.96 99.2264.24 100.00 65.14 98.36 63.92 100.59 65.7499.56 65.53 98.35 63.80 98.33 64.98 97.25 64.40 Al2O3 16.95 18.04 18.32 18.43 17.34 18.03 18.38 18.33 17.88 18.18 17.61 17.54 19.62 19.15 Formula based on 8 oxygen atoms, apfu Fe2O3 0.05 0.06 b.d. 0.03 b.d. 0.09 0.02 0.04 b.d. 0.08 0.51 0.65 0.38 0.45 BaO Si0.14 3.03b.d. 3.01b.d. 3.01 b.d. 3.01 b 3.03.d. 3.010.12 2.99b.d. 3.010.08 3.010.13 3.02b.d.3.02 0.12 3.00 b.d. 2.97 1.60 2.981.32 Na2O Al 0.30 0.950.26 0.99 0.35 0.99 0.38 0.99 0.30 0.95 0.980.32 1.010.43 1.00 0.34 0.99 0.39 0.98 0.39 0.96 1.74 0.97 0.64 1.06 5.00 1.044.41 3+ ------0.02 0.02 0.01 0.02 K2O Fe 16.72 16.19 16.43 15.89 16.89 16.32 16.15 16.07 16.04 16.20 14.05 15.72 6.75 7.52 Sum Ba 98.14 -99.45 -100.42 -100.61 - 99.81 - 99.96 - 99.22 - 100.00 - -98.36 -100.59 -99.56 -98.35 0.03 98.33 0.02 97.25 Na 0.03 0.02 0.03 0.03 0.03 0.03 0.04 0.03 0.04 0.03 0.16 0.06 0.44 0.39 Formula based on 8 oxygen atoms, apfu K 1.01 0.96 0.97 0.93 1.00 0.96 0.96 0.95 0.96 0.95 0.83 0.94 0.39 0.44 Si Sum 3.03 5.023.01 4.98 3.01 5.00 3.01 4.96 3.03 5.01 4.983.01 5.002.99 4.99 3.01 5.00 3.01 4.98 3.02 4.99 3.02 4.99 3.00 4.90 2.97 4.892.98 Al 0.95 0.99 0.99 0.99 0.95 0.98 1.01 1.00 0.99 0.98 0.96 0.97 1.06 1.04 Fe3+ - - - - - Mol.- % endmembers- - - - 0.02 0.02 0.01 0.02 Ba Or- 97- 98- 97- 96 97- 97- 96- 97- 96- 96- 82- 92- 440.03 50 0.02 Na Ab 0.03 30.02 2 0.03 3 0.03 4 0.03 3 0.03 3 0.04 4 3 0.03 4 0.04 4 0.03 16 0.16 60.06 510.44 45 0.39 K Csn 1.01 -0.96 - 0.97 - 0.93 - 1.00 - 0.96 - 0.96 - - 0.95 - 0.96 - 0.95 - 0.83 -0.94 30.39 3 0.44 Sum For 5.02 -4.98 - 5.00 - 4.96 - 5.01 - 4.98 - 5.00 - - 4.99 - 5.00 - 4.98 2 4.99 24.99 24.90 2 4.89 *—point A of Figure8; **—point B of Figure8Mol.; Or—orthoclase, % endmembers Ab—albite, Csn—celsian, For—ferriorthoclase 3+ Or (KFe 97Si 3O8). 98 97 96 97 97 96 97 96 96 82 92 44 50 Ab 3 2 3 4 3 3 4 3 4 4 16 6 51 45 Csn ------3 3 For ------2 2 2 2 Minerals 2017, 7, x FOR PEER REVIEW 13 of 32

*—point A of Figure 8; **—point B of Figure 8; Or—orthoclase, Ab—albite, Csn—celsian, For—

ferriorthoclase (KFe3+Si3O8).

In fine-grained nepheline syenite, phenocrysts of alkali feldspar are also exsolved into pure albite and microcline Or91–98Ab2–9 (line 2 in Figure 8a). In the fine-grained mass, the composition of perthite-free microcline is Or80–92Ab6–17, with the same Ba amount (up to 0.01 apfu) and a higher Fe content (up to 0.03 apfu). In metasomatic rocks, feldspar is exsolved into orthoclase and albite unevenly. There occur nearby grains of homogeneous feldspar Or44–58Ab55–41 and grains with small amounts of perthite (3– 15 vol. %). The composition of such grains is Or58–66Ab42–34 + Ab100. An increase in the perthite quantity Minerals 2019, 9, 581 13 of 31 (up to 38 vol. %) leads to a decrease in Na content in the matrix (up to Or98Ab2). Sometimes, within the same grain, there are separated areas of homogeneous and perthite-bearing potassium feldspar (FigureThe 8a,b). compositions of alkali feldspar of coarse- and medium-grained rocks do not depend on whetherAlbite or notlamellae a primary in alkali (not feldspar perthitic) from albite all types is present of rocks in have the rock. the same In any composition: case, alkali Ab feldspar100. The is composition of primary albite ranges as Ab94–99Or1–6 and does not depend on the type of rock. An exsolved into pure albite and microcline, whose composition is Or94–99Ab1–6 (lines 3–7 in Figure8a) impurity of Fe2O3, which reaches maximum values (up to 0.30 wt. %) in albite from fine-grained with permanent impurities of Fe (up to 0.01 apfu) and Ba (up to 0.01 apfu). nepheline syenite, is characteristic.

FigureFigure 8. (а)—The(a)—The composition composition of alkali of alkalifeldspar feldspar from the from rock theof the rock Alluaiv of the site Alluaivin the coordinates site in the coordinatesof albite (Ab)–orthoclase of albite (Ab)–orthoclase (Or). In fine-grain (Or).ed In nepheline ﬁne-grained syenite: nepheline FM—fine-grained syenite: FM—ﬁne-grained mass; РC— mass;phenocrysts.РC—phenocrysts. In metasomatic In metasomatic rock: A, B–composition rock: A, B–composition of alkali feldspar of alkali corresponding feldspar corresponding to points in to pointsFigure in 8b. Figure (b)—fragment8b. ( b)—fragment of alkali feldspar of alkali crystal feldspar in metasomatic crystal in metasomatic rock. BSE-image rock. BSE-image(156/98). (156/98).

4.3.2.In Nepheline fine-grained nepheline syenite, phenocrysts of alkali feldspar are also exsolved into pure albiteRepresentative and microcline analyses Or91–98 Abof nepheline2–9 (line 2 inare Figure shown8a). in Table In the 2, fine-grained while all available mass, thecompositions composition are of perthite-freeshown in Figure microcline 9 in isthe Or 80–92coordinatesAb6–17, with of theNph same (nepheline)–Ks Ba amount (up(calsilite)–Qtz to 0.01 apfu )(SiO and2) a higherand in Fe contentSupplementary (up to 0.03 Materialsapfu). (Table S5). Morphological types of nepheline are clearly separated by the contentIn metasomatic of Qtz endmember. rocks, feldspar The composition is exsolved of into nepheline-I orthoclase is Nph and67–78 albiteKs15–23 unevenly.Qtz1–12, Therewhile occurnepheline- nearby grainsII contains of homogeneous more Qtz-component: feldspar Or44–58 NphAb61–7455–41Ksand13–21Qtz grains9–23. withIn these small intervals, amounts ofthe perthite compositions (3–15 vol. of %). Thenepheline composition from most of such rocks grains of the is Eudialyte Or58–66Ab Complex42–34 + Ab are100 evenly. An increasedistributed, in the except perthite for poikilitic quantity rocks (up to 38and vol. fine-grained %) leads to nepheline a decrease syenite, in Na contentwhere nepheline in the matrix is enriched (up to Or with98Ab SiO2).2. Sometimes, In fine-grained within nepheline the same grain,syenite, there the arecompositions separated areasof nepheline of homogeneous from fine-grained and perthite-bearing mass and phenocrysts potassium do feldspar not differ. (Figure 8a,b). Albite lamellae in alkali feldspar from all types of rocks have the same composition: Ab100. The composition of primary albite ranges as Ab94–99Or1–6 and does not depend on the type of rock. An impurity of Fe2O3, which reaches maximum values (up to 0.30 wt. %) in albite from fine-grained nepheline syenite, is characteristic.

4.3.2. Nepheline Representative analyses of nepheline are shown in Table2, while all available compositions are shown in Figure9 in the coordinates of Nph (nepheline)–Ks (calsilite)–Qtz (SiO 2) and in Supplementary Materials (Table S5). Morphological types of nepheline are clearly separated by the content of Qtz endmember. The composition of nepheline-I is Nph67–78Ks15–23Qtz1–12, while nepheline-II contains more Qtz-component: Nph61–74Ks13–21Qtz9–23. In these intervals, the compositions of nepheline from most rocks of the Eudialyte Complex are evenly distributed, except for poikilitic rocks and fine-grained nepheline syenite, where nepheline is enriched with SiO2. In fine-grained nepheline syenite, the compositions of nepheline from fine-grained mass and phenocrysts do not differ. Minerals 2019, 9, 581 14 of 31

Table 2. Representative microprobe analyses of nepheline, wt. %.

Shonkinite, Fine-Grained Metasomatic Rock Malignite Ijolite Foyaite Urtite Melteigite Nph-syenite Rock Drill hole 117 154 153 44 117 153 117 157 230 117 147 160 156 156 Deep, m 121 85 178 108 111 36 217 164 239 208 1 148 137 157

SiO2 44.76 41.79 42.71 45.72 43.14 44.58 42.38 44.74 43.12 41.45 42.20 43.61 44.35 45.81 Al2O3 30.65 32.38 32.73 31.08 31.15 30.78 32.79 29.88 33.38 32.78 33.62 29.40 31.69 30.78 Fe2O3 1.44 0.16 0.18 1.63 1.53 1.25 0.16 1.87 0.26 0.15 0.12 1.91 1.77 1.09 CaO b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. 0.03 K2O 5.44 6.63 6.71 6.08 5.85 5.81 6.51 5.42 6.62 6.67 7.25 5.36 5.47 5.35 Na2O 16.23 16.23 16.36 15.95 16.54 16.16 15.23 16.13 15.56 15.27 15.14 15.69 15.91 15.17 Sum 98.52 97.19 98.68 100.45 98.21 98.58 97.08 98.04 98.93 96.31 98.32 95.97 99.20 98.24 Formula based on 8 oxygen atoms, apfu Si 4.35 4.15 4.18 4.37 4.24 4.34 4.19 4.38 4.18 4.14 4.14 4.36 4.28 4.43 Al 3.51 3.79 3.77 3.50 3.61 3.53 3.82 3.45 3.82 3.86 3.88 3.47 3.61 3.51 Fe3+ 0.11 0.01 0.01 0.12 0.11 0.09 0.01 0.14 0.02 0.01 0.01 0.14 0.13 0.08 K 0.67 0.84 0.84 0.74 0.73 0.72 0.82 0.68 0.82 0.85 0.91 0.68 0.67 0.66 Na 3.06 3.13 3.10 2.95 3.15 3.05 2.92 3.06 2.93 2.96 2.88 3.04 2.98 2.85 Sum 11.71 11.93 11.90 11.67 11.84 11.73 11.76 11.70 11.77 11.82 11.81 11.70 11.67 11.53 Mol. % endmembers Nph 70 75 74 68 74 70 70 70 70 71 69 70 69 64 Ks 16 20 20 17 17 17 19 15 20 21 22 16 16 15 Qtz 14 5 6 15 9 13 11 15 10 8 9 14 15 21 Nph—nepheline; Ks—kalsilite; Qtz—quartz. Minerals 2017, 7, x FOR PEER REVIEW 14 of 32

Figure 9. Nepheline compositions in the nepheline (Nph)–kalsilite (Ks)–quartz (SiO2) triangle (on a Figure 9. Nepheline compositions in the nepheline (Nph)–kalsilite (Ks)–quartz (SiO2) triangle (on amol. mol. % % basis) basis) for for the the rocks rocks of the of Alluaiv the Alluaiv site. The site. isotherms The isotherms are from are [31]. from [31].

Fe3+ (up to 0.16 apfuTable) is 2. a Representative permanent impuritymicroprobe inanalyses nepheline of nepheline, composition, wt. %. and rare impurities, found in only 1% of the samples, are Ca (up to 0.01 apfu) and Ba (up to 0.004Fine-apfu). According to the Shonkinite, Metasomatic Rock Malignite Ijolite Foyaite Urtite Grained results of factor analysis of data on theMelteigite nepheline composition (Figure 10), the main isomorphismRock Nph-syenite schemeDrill in hole this mineral117 154 can153 be written 44 as: 117 153 117 157 230 117 147 160 156 156 Deep, m 121 85 178 108 111 36 217 164 239 208 1 148 137 157 4+ 3+ + 3+ SiO2 44.76 41.79 42.71 45.72B + (Si 43.14 + 44.58Fe )T42.38 K44.74B + 2Al43.12 T,41.45 42.20 43.61 44.35 45.81 Al2O3 30.65 32.38 32.73 2 31.08 31.15 30.78 32.79 29.88 33.38 32.78 33.62 29.40 31.69 30.78 Fe2O3 1.44 0.16 0.18 1.63 1.53 1.25 0.16 1.87 0.26 0.15 0.12 1.91 1.77 1.09 (ifCaO the composition b.d. b.d. ofb.d. nepheline b.d. is b.d. expressed b.d. byb.d. the formulab.d. b.d.A 4Bb.d.4Т 8Оb.d.16). b.d. b.d. 0.03 TheK2O same 5.44substitution 6.63 6.71 is characteristic 6.08 5.85 of5.81 nepheline 6.51 of5.42 the Khibiny6.62 6.67 Massif 7.25 [325.36,33 ]. Factor5.47 5.35 analysis has showedNa2O also 16.23 that 16.23 compositions 16.36 15.95 corresponding 16.54 16.16 15.23 to diﬀ16.13erent 15.56 types 15.27 of rocks15.14 were15.69 divided15.91 15.17 into two Sum 98.52 97.19 98.68 100.45 98.21 98.58 97.08 98.04 98.93 96.31 98.32 95.97 99.20 98.24 almost isolated groups, in accordanceFormula with thebased main on 8 oxygen isomorphism atoms, apfu scheme (Figure 10). Nepheline from ﬁne-grainedSi nepheline 4.35 4.15 syenite4.18 and 4.37 metasomatic 4.24 4.34 rocks4.19 are4.38 enriched4.18 4.14 with 4.14 iron. 4.36 In malignite,4.28 4.43 ijolite, shonkinite,Al and 3.51 melteigite, 3.79 3.77 nepheline-I 3.50 3.61 is rich3.53 in K3.82 and Al,3.45 while3.82 nepheline-II3.86 3.88 is3.47 enriched 3.61 with3.51 iron. Fe3+ 0.11 0.01 0.01 0.12 0.11 0.09 0.01 0.14 0.02 0.01 0.01 0.14 0.13 0.08 Most nephelineK 0.67 samples 0.84 from0.84 foyaite 0.74 and 0.73 urtite0.72 are0.82 relatively 0.68 rich0.82 in0.85 K and 0.91 Al. 0.68 0.67 0.66 Na 3.06 3.13 3.10 2.95 3.15 3.05 2.92 3.06 2.93 2.96 2.88 3.04 2.98 2.85 Sum 11.71 11.93 11.90 11.67 11.84 11.73 11.76 11.70 11.77 11.82 11.81 11.70 11.67 11.53 Mol. % endmembers Nph 70 75 74 68 74 70 70 70 70 71 69 70 69 64 Ks 16 20 20 17 17 17 19 15 20 21 22 16 16 15 Qtz 14 5 6 15 9 13 11 15 10 8 9 14 15 21 Nph—nepheline; Ks—kalsilite; Qtz—quartz.

Fe3+ (up to 0.16 apfu) is a permanent impurity in nepheline composition, and rare impurities, found in only 1% of the samples, are Ca (up to 0.01 apfu) and Ba (up to 0.004 apfu). According to the results of factor analysis of data on the nepheline composition (Figure 10), the main isomorphism scheme in this mineral can be written as:

⬜B + (Si4+ + Fe3+)T ⇆ K+B + 2Al3+T,

(if the composition of nepheline is expressed by the formula А4В4Т8О16). The same substitution is characteristic of nepheline of the Khibiny Massif [32,33]. Factor analysis has showed also that compositions corresponding to different types of rocks were divided into two almost isolated groups, in accordance with the main isomorphism scheme (Figure 10). Nepheline from fine-grained nepheline syenite and metasomatic rocks are enriched with iron. In malignite, ijolite, shonkinite, and melteigite, nepheline-I is rich in K and Al, while nepheline-II is enriched with iron. Most nepheline samples from foyaite and urtite are relatively rich in K and Al. Minerals 2017, 7, x FOR PEER REVIEW 15 of 32

In meso- and melanocratic rocks (malignite, ijolite, shonkinite, and melteigite), contents of Si, Fe3+, Al, K in nepheline-I correlate with Fe3+ amount in coexisting microcline (Figure 11a). Interrelations between other components are weak because their ratio in the feldspar changed when perthites were formed. Also, there are no significant correlations between the compositions of nepheline-II and coexisting microcline. In foyaite and urtite, contents of Si, Fe3+, Al, K in nepheline correlate with Fe3+ amount in coexisting microcline. The compositions of coexisting nepheline and Mineralsmicrocline2019, 9 ,from 581 fine-grained nepheline syenite are interrelated, with positive correlations between15 of 31 the same elements (Figure 11b). Minerals 2017, 7, x FOR PEER REVIEW 15 of 32

FigureFigure 10. 10.Results Results ofof factorfactor analysesanalyses of data on on the the co compositionmposition of of nepheline nepheline from from the the Alliaiv Alliaiv site. site. PointsPoints on on a a gray gray background background correspondcorrespond to nephe nephelineline with with inclusions inclusions ofof microcline microcline and and aegirine. aegirine. Var.—variables;Var.—variables; Expl.var.—Explained Expl.var.—Explained variance; variance; Prp.totl—proportion Prp.totl—proportion of totalof variance.total variance. Factor Factor loadings > |loadings0.5| are shown > |0.5|in are bold. shown in bold.

In meso- and melanocratic rocks (malignite, ijolite, shonkinite, and melteigite), contents of Si, Fe3+, Al, K in nepheline-I correlate with Fe3+ amount in coexisting microcline (Figure 11a). Interrelations between other components are weak because their ratio in the feldspar changed when perthites were formed. Also, there are no signiﬁcant correlations between the compositions of nepheline-II and coexisting microcline. In foyaite and urtite, contents of Si, Fe3+, Al, K in nepheline correlate with Fe3+ amountFigure in10. coexistingResults of factor microcline. analyses The of data compositions on the composition of coexisting of nepheline nepheline from the and Alliaiv microcline site. from ﬁne-grainedPoints nephelineon a gray background syenite are correspond interrelated, to nephe withline positive with inclusions correlations of microcline between and the aegirine. same elements Var.—variables; Expl.var.—Explained variance; Prp.totl—proportion of total variance. Factor (Figure 11b). loadings > |0.5| are shown in bold.

Figure 11. Correlation coefficients (r): (a)—between the content of Fe3+ in microcline and cations in coexisting nepheline-I and nepheline-II; (b)—between cations in microcline (color lines) and cations in coexisting nepheline from fine-grained nepheline syenite. Black and empty dots indicate significant (p ≤ 0.05) and insignificant correlation coefficients, respectively.

4.3.3. Clinopyroxenes Representative chemical analyses of clinopyroxenes from the rocks of the Eudialyte Complex are presented in Table 3, and all analyses are in Table S6 (Supplementary Materials) and generated in Figure 12. In all types of rock, except for metasomatic varieties, clinopyroxenes are presented by

aegirine and aegirine-augite with high contents of Ti (up to 0.16 apfu), Zr (up to 0.05 apfu) and Al (up 3+ to 0.05FigureFigure apfu 11. ).11. Correlation Correlation coe coefficientsfficients (r):(r): ((aa)—between)—between the the content content of of Fe Fe3 +inin microcline microcline and and cations cations in in coexistingcoexisting nepheline-I nepheline-I and and nepheline-II; nepheline-II; ( b(b)—between)—between cations cations inin microclinemicrocline (color(color lines)lines) and cations in in coexisting nepheline from fine-grained nepheline syenite. Black and empty dots indicate significant coexisting nepheline from fine-grained nepheline syenite. Black and empty dots indicate significant (p ≤ 0.05) and insignificant correlation coefficients, respectively. (p 0.05) and insignificant correlation coefficients, respectively. ≤ 4.3.3.4.3.3. Clinopyroxenes Clinopyroxenes RepresentativeRepresentative chemical chemical analysesanalyses ofof clinopyroxenesclinopyroxenes from from the the rocks rocks of of the the Eudialyte Eudialyte Complex Complex areare presented presented in in Table Table3, 3, and and all all analyses analyses are are in in TableTable S6S6 (Supplementary(Supplementary Materials) Materials) and and generated generated inin Figure Figure 12 12.. In In all all types types of of rock, rock, except except forfor metasomaticmetasomatic varieties, varieties, clinopyroxenes clinopyroxenes are are presented presented by by aegirine and aegirine-augite with high contents of Ti (up to 0.16 apfu), Zr (up to 0.05 apfu) and Al (up to 0.05 apfu). Minerals 2019, 9, 581 16 of 31 aegirine and aegirine-augite with high contents of Ti (up to 0.16 apfu), Zr (up to 0.05 apfu) and Al (up to 0.05 apfu).

Table 3. Representative microprobe analyses of clinopyroxenes, wt. %.

Shonkinite, Fine-Grained Rock Malignite Ijolite Foyaite Urtite Metasomatic Rock Melteigite Nph-Syenite Drill hole 117 228 33 160 153 222 154 157 117 156 154 157 156 156 156 156 Deep, m 121 84 211 120 8 177 35 155 235 56 226 36 89 A** 89 B 89 C 89 D

SiO2 52.12 52.66 50.68 52.54 49.96 53.23 51.75 52.36 51.97 51.49 51.34 52.12 51.91 50.61 51.46 51.78 ZrO2 0.74 0.75 0.71 0.61 0.53 0.41 0.78 0.70 0.76 0.61 0.98 0.64 b.d. 0.27 1.05 0.90 TiO2 3.06 2.97 3.06 2.54 2.74 3.84 2.70 2.35 2.77 4.26 2.97 2.74 0.97 1.32 3.17 4.01 Al2O3 0.79 0.89 0.71 0.80 0.87 0.80 0.77 0.97 0.86 0.89 0.76 0.78 1.33 1.12 0.90 0.87 V2O3 0.05 b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. CaO 2.67 2.69 2.74 3.04 1.68 1.59 2.57 3.78 1.90 2.49 3.17 2.71 17.58 19.96 5.71 3.46 MgO 1.54 1.90 1.79 2.11 1.12 1.22 1.64 2.17 1.46 1.47 1.72 1.70 12.59 10.77 3.03 2.12 FeO 23.60 23.37 23.61 23.13 24.91 24.87 24.13 24.13 23.70 24.43 23.49 24.76 8.32 10.08 20.85 22.53 MnO 0.40 0.57 0.45 0.53 0.40 0.48 0.48 0.44 0.33 0.46 0.45 0.41 0.66 0.65 0.47 0.62 ZnO b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. 0.08 b.d. b.d. b.d. b.d. b.d. b.d. b.d. Na2O 12.28 12.57 12.05 12.44 13.41 13.40 12.60 12.20 13.15 12.16 12.59 12.79 1.85 2.91 10.48 12.04 K2O b.d. b.d. b.d. b.d. b.d. b.d. 0.10 b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. Sum 97.25 98.37 95.81 97.72 95.61 99.83 97.50 99.08 96.97 98.27 97.47 98.62 95.21 97.69 97.12 98.32 Formula based on 4 cations and 6 oxygen atoms, apfu Si 1.99 1.98 1.96 1.98 1.92 1.97 1.96 1.96 1.97 1.96 1.95 1.95 2.02 1.93 1.98 1.96 Zr 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.02 0.01 – 0.01 0.02 0.02 Ti 0.09 0.08 0.09 0.07 0.08 0.11 0.08 0.07 0.08 0.12 0.09 0.08 0.03 0.04 0.09 0.11 Al 0.04 0.04 0.03 0.04 0.04 0.04 0.03 0.04 0.04 0.04 0.03 0.03 0.06 0.05 0.04 0.04 Ca 0.11 0.11 0.11 0.12 0.07 0.06 0.11 0.15 0.08 0.10 0.13 0.11 0.73 0.81 0.24 0.14 Mg 0.09 0.11 0.10 0.12 0.06 0.07 0.09 0.12 0.08 0.08 0.10 0.10 0.73 0.61 0.17 0.12 Fe2+ 0.06 0.01 0.02 - - 0.02 - - - 0.10 - - 0.27 0.09 0.10 0.04 Fe3+ 0.69 0.72 0.74 0.73 0.80 0.76 0.77 0.75 0.75 0.68 0.75 0.78 - 0.23 0.57 0.67 Mn 0.01 0.02 0.02 0.02 0.01 0.02 0.02 0.01 0.01 0.02 0.02 0.01 0.02 0.02 0.02 0.02 Na 0.91 0.92 0.91 0.91 1.00 0.96 0.93 0.88 0.97 0.90 0.93 0.93 0.14 0.22 0.78 0.88 K------0.01 ------Mol % endmembers Q 13 11 12 12 6 7 10 13 8 14 11 10 100 78 25 15 Aeg 83 84 84 84 89 89 86 82 88 81 85 86 - 18 70 81 Jd 4 5 4 4 5 4 4 5 4 5 4 4 - 4 5 4

*—pyroxene compositions at points A–D correspond to Figure 12b; **—endmember composition 89A: Wo42En41Fs17.

The factor analysis of the clinopyroxene compositions (Figure 12a) revealed two main schemes of isomorphism: Na++ Ti4+ + Al3+ Ca2+ + Mg2+ + Zr4+;

Fe3+ + (Al, Fe)3+ Fe2+ + Si4+.

The zirconium content goes up with an increase in Ca and Mg and reaches maximum values in aegirine-augite. High concentrations of titanium, on the contrary, are characteristic of aegirine. The chemical composition of clinopyroxenes in rocks of the Eudialyte Complex (except for metasomatic rocks) varies widely, but does not depend on the type of rock (Figure 12a,b). It is important to note the constant admixture of manganese (up to 0.04 apfu) in clinopyroxenes (see Table3). Potassium impurity (up to 0.01 apfu) was recorded in 7% of studied samples, while impurities of vanadium (up to 0.002 apfu) and zinc (up to 0.02 apfu) occur in 2% of the samples. In metasomatic rocks, resorbed augite relics (point A in Figure 13b) are surrounded at ﬁrst by aegirine-augite (points B and C), and then by aegirine (point D). Factor analysis of the data on the composition of clinopyroxenes from these rocks (Figure 13a) managed to separate relicts of (aegirine)-augite from later aegirine enriched with titanium and zirconium. Minerals 2017, 7, x FOR PEER REVIEW 17 of 32

The factor analysis of the clinopyroxene compositions (Figure 12a) revealed two main schemes of isomorphism:

Na++ Ti4+ + Al3+ ⇆ Ca2+ + Mg2+ + Zr4+;

Fe3+ + (Al, Fe)3+ ⇆ Fe2+ + Si4+. The zirconium content goes up with an increase in Ca and Mg and reaches maximum values in aegirine-augite. High concentrations of titanium, on the contrary, are characteristic of aegirine. The chemical composition of clinopyroxenes in rocks of the Eudialyte Complex (except for metasomatic rocks) varies widely, but does not depend on the type of rock (Figure 12a,b). It is important to note the constant admixture of manganese (up to 0.04 apfu) in clinopyroxenes Minerals 2019,(see9, 581 Table 3). Potassium impurity (up to 0.01 apfu) was recorded in 7% of studied samples, while 17 of 31 impurities of vanadium (up to 0.002 apfu) and zinc (up to 0.02 apfu) occur in 2% of the samples.

Figure 12. ChemicalFigure 12. Chemical composition composition of clinopyroxenes of clinopyroxenes from from magmatic magmatic rocks of of the the Alluaiv Alluaiv site: site: (а)— (a)—results results of factor analyses of data on the composition of clinopyroxenes from the Alluaiv site. Points of factor analyseson a gray of databackground on the correspond composition to aegirine of clinopyroxenes-augite, the other from points the are Alluaiv of aegirine; site. Points(b)— on a gray backgroundcompositional correspond variation to aegirine-augite, of clinopyroxene the in other triangular points system are Mg–(Fe of aegirine;2+ + Mn)–Na. (b)—compositional Var.—variables; variation of clinopyroxeneExpl.var.—Explained in triangular variance; system Prp. Mg–(Fetotl—proportion2+ + Mn)–Na. of total variance. Var.—variables; Factor loadings Expl.var.—Explained > |0.5| are shown in bold. variance;Minerals Prp.totl—proportion 2017, 7, x FOR PEER REVIEW of total variance. Factor loadings > |0.5| are shown in bold.18 of 32 In metasomatic rocks, resorbed augite relics (point A in Figure 13b) are surrounded at first by aegirine-augite (points B and C), and then by aegirine (point D). Factor analysis of the data on the composition of clinopyroxenes from these rocks (Figure 13a) managed to separate relicts of (aegirine)- augite from later aegirine enriched with titanium and zirconium. There are significant correlations between a sodium content in nepheline (morphological types I and II) and contents of sodium (r = 0.350), ferric iron (r = 0.354), ferrous iron (r = –0.460) and silicon (r = –0.456) in clinopyroxenes in meso- and melanocratic rocks. Similar correlations have been established for nepheline and clinopyroxenes from fine-grained nepheline syenite.

Figure 13.FigureChemical 13. Chemical composition composition of of clinopyroxenes fromfrom metasomatic metasomatic rocks of the rocks Alluaiv of site: the (а)— Alluaiv site: results of factor analyses. Points on a gray background correspond to augite (Au) and aegirine-augite (a)—results of factor analyses. Points on a gray background correspond to augite (Au) and (Aeg-Au), with other points corresponding to aegirine (Aeg). Points A–D correspond to Figure 13b,c. aegirine-augiteVar.—variables; (Aeg-Au), Expl.var.—Explained with other points variance; corresponding Prp.totl—proportion to aegirine of (Aeg). total variance. Points A–DFactor correspond to Figure 13loadingsb,c. Var.—variables; > |0.5| are shown Expl.var.—Explainedin bold. (b)—relicts of augite variance; surrounded Prp.totl—proportion by rims of aegirine-augite of totaland variance. Factor loadingsaegirine> in |0.5 a metasomatic| are shown rock in 156/89. bold. The (b)—relicts compositions of augitecorresponding surrounded to points by A–D rims are shown of aegirine-augite in Figure 13a,c; (c)—compositional variation of clinopyroxenes in Mg–(Fe2+ + Mn)–Na system. and aegirine in a metasomatic rock 156/89. The compositions corresponding to points A–D are shown 2+ in Figure4.3.4. 13 Amphibolesa,c; (c)—compositional variation of clinopyroxenes in Mg–(Fe + Mn)–Na system. Representative analyses of amphiboles are given in Table 4, and all analyses are in Table S7 (Supplementary Materials). Formula calculations for amphiboles were made on the base of 16 cations and 23 oxygens. This calculation resulted in systematically slightly under-occupied C-sites and over- occupied A-sites, which may be explained by significant Li contents [34] that cannot be measured by an electron microprobe. A method of lithium content calculation proposed in [34] cannot be used, since the discrepancy between measured and calculated Li2O is quite significant at relatively high lithium content typical for amphiboles of the Lovozero Massif (up to 0.6 wt. % Li2O [24]). The cation excess in C-site and deficit in A-site were not found only in 37% (80 samples) of investigated amphiboles. The most of these amphiboles (70 samples) are magnesioarfvedsonite, the rest belong to arfvedsonite. The lithium content determines the value of the ratio Fe3+/Fe2+ in amphiboles, because of following replacement: LiM3 + Fe3+ ⇆ Fe2+M3 + Fe2+ [35]. In this study, measurements of Li content in amphiboles were not carried out; therefore, we do not discuss the Fe3+/Fe2+ ratio in amphiboles. As an alternative, we considered concentrations of major and minor elements in binary diagrams (Figure 14). Amphiboles from meso- and melanocratic rocks are characterized by an increased content of Ca (up to 0.28 apfu), Al (up to 0.30 apfu) and Ti (up to 0.28 apfu), while amphiboles from leucocratic rocks and fine-grained nepheline syenite are enriched in К (up to 0.71 apfu), Si and Mn (up to 0.52 apfu). Minerals 2019, 9, 581 18 of 31

There are signiﬁcant correlations between a sodium content in nepheline (morphological types I and II) and contents of sodium (r = 0.350), ferric iron (r = 0.354), ferrous iron (r = –0.460) and silicon (r = –0.456) in clinopyroxenes in meso- and melanocratic rocks. Similar correlations have been established for nepheline and clinopyroxenes from ﬁne-grained nepheline syenite.

4.3.4. Amphiboles Representative analyses of amphiboles are given in Table4, and all analyses are in Table S7 (Supplementary Materials). Formula calculations for amphiboles were made on the base of 16 cations and 23 oxygens. This calculation resulted in systematically slightly under-occupied C-sites and over-occupied A-sites, which may be explained by significant Li contents [34] that cannot be measured by an electron microprobe. A method of lithium content calculation proposed in [34] cannot be used, since the discrepancy between measured and calculated Li2O is quite significant at relatively high lithium content typical for amphiboles of the Lovozero Massif (up to 0.6 wt. % Li2O[24]). The cation excess in C-site and deficit in A-site were not found only in 37% (80 samples) of investigated amphiboles. The most of these amphiboles (70 samples) are magnesioarfvedsonite, the rest belong to arfvedsonite.

Table 4. Representative microprobe analyses of amphiboles, wt. %.

Shonkinite, Fine-Grained Metasomatic Rock Malignite Ijolite Foyaite Urtite Melteigite Nph-Syenite Rock Drill hole 117 147 231 117 153 222 147 154 147 156 154 154 156 231 Deep, m 4 194 176 93 36 231 275 172 85 56 245 * 245 ** 89 *** 146

SiO2 51.81 53.78 53.10 53.32 52.33 52.50 52.30 53.82 52.90 52.44 53.12 51.10 52.56 54.65 TiO2 1.76 1.50 1.36 1.54 1.63 1.77 1.56 1.02 1.47 1.31 1.64 0.86 0.56 2.01 Al2O3 1.49 0.77 0.78 1.25 1.33 1.29 1.14 1.09 1.22 1.00 0.62 0.58 1.99 1.61 FeO 17.54 17.19 17.56 17.00 18.16 16.79 17.75 12.62 16.78 18.00 17.42 26.17 10.95 14.24 MnO 1.39 1.50 1.49 1.20 1.52 1.51 1.49 1.68 1.37 1.38 1.66 3.13 1.29 1.61 MgO 9.36 10.45 10.03 10.37 9.75 10.29 10.52 13.08 11.62 9.61 9.32 2.64 14.00 12.98 CaO 0.94 0.83 0.59 1.15 1.02 1.13 1.20 0.91 1.35 0.71 0.48 0.29 5.66 1.65 ZnO 0.07 0.05 0.06 b.d. 0.08 0.05 b.d. 0.05 b.d. b.d. 0.08 0.07 0.07 b.d. Na2O 9.30 9.50 9.17 9.26 8.90 9.37 9.26 9.41 8.92 8.78 10.10 8.46 6.87 9.12 K2O 1.65 1.55 1.56 1.68 1.76 1.67 1.61 1.53 1.64 1.67 1.68 3.11 1.40 1.57 F b.d. b.d. 2.10 b.d. b.d. 1.50 b.d. b.d. b.d. b.d. b.d. b.d. b.d. 1.70 О=F 0.00 0.00 0.88 0.00 0.00 0.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.72 − − − Sum 95.31 97.12 96.92 96.77 96.48 97.24 96.83 95.21 97.27 94.90 96.11 96.41 95.35 100.42 Formula based on O + OH + F = 24 apfu and OH = 2 – 2Ti Si (T) 7.83 7.94 7.99 7.90 7.84 7.81 7.76 7.93 7.78 7.99 7.93 8.04 7.84 7.80 Al (T) 0.17 0.05 0.01 0.10 0.16 0.19 0.20 0.07 0.21 0.01 0.07 - 0.16 0.20 Ti (T) ------0.04 - 0.01 - - - - - Sum T 8.00 7.99 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.04 8.00 8.00 Ti (C) 0.20 0.17 0.15 0.17 0.18 0.20 0.13 0.11 0.15 0.15 0.18 0.10 0.06 0.22 Al (C) 0.09 0.08 0.12 0.12 0.08 0.04 - 0.12 - 0.16 0.03 0.11 0.19 0.07 Fe3+ (C) 0.72 0.66 0.56 0.62 0.64 0.78 0.91 0.70 0.75 0.47 0.92 0.81 - 0.51 Mn (C) 0.18 0.19 0.19 0.15 0.19 0.19 0.19 0.21 0.17 0.18 0.21 0.42 0.16 0.19 Fe2+ (C) 1.49 1.46 1.65 1.49 1.64 1.31 1.29 0.86 1.31 1.83 1.26 2.64 1.36 1.19 Mg (C) 2.11 2.30 2.25 2.29 2.18 2.28 2.33 2.87 2.55 2.18 2.07 0.62 3.11 2.76 Zn (C) 0.01 - 0.01 - 0.01 - - 0.01 - - 0.01 0.01 0.01 - Sum C 4.80 4.86 4.93 4.84 4.92 4.80 4.85 4.88 4.93 4.97 4.68 4.71 4.89 4.94 Ca (B) 0.15 0.13 0.09 0.18 0.16 0.18 0.19 0.14 0.21 0.12 0.08 0.05 0.90 0.25 Na (B) 1.85 1.87 1.91 1.82 1.84 1.82 1.81 1.86 1.79 1.88 1.92 1.95 1.10 1.75 Sum B 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 Na (A) 0.88 0.85 0.77 0.84 0.74 0.88 0.85 0.83 0.76 0.71 1.00 0.63 0.89 0.77 K(A) 0.32 0.30 0.30 0.32 0.34 0.32 0.30 0.29 0.31 0.32 0.32 0.62 0.27 0.29 Sum A 1.20 1.15 1.07 1.16 1.08 1.20 1.15 1.12 1.07 1.03 1.30 1.25 1.16 1.06 OH (W) 2.00 2.00 1.00 2.00 2.00 1.29 2.00 2.00 2.00 2.00 2.00 2.00 2.00 1.23 F(W) - - 1.00 - - 0.71 ------0.77 Sum W 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 2.00 *—core of zonal grain; **—edge of zonal grain; ***—rim around augite relict (see Figure 13b). T,C,B,A,W—sites in general formula AB2C5T8O22W2 [27]. Minerals 2019, 9, 581 19 of 31

Minerals 2017, 7, x FOR PEER REVIEW 19 of 32 3+ 2+ TheIn lithium the metasomatic content determines rocks, sodium-calcium the value of the(ferri-katophorite, ratio Fe /Fe richterite)in amphiboles, and sodium because of 3+ 2+ 2+ following(eckermannite) replacement: amphiboles LiM3 + alongFe withFe aegirine-augM3 + Fe ite[35 surround]. In this the study, augite measurements relics. These amphiboles of Li content in 3+ 2+ amphibolesstand out were clearly not in carried binary out;diagrams therefore, (Figure we 14) do with not high discuss Ca (up the to Fe 0.46/ Feapfu) ratioand Al in (up amphiboles. to 0.41 apfu) As an alternative,contents. we Magnesioarfvedsonite considered concentrations is also of characteristic major and minor of these elements rocks, in but binary it forms diagrams symplectic (Figure 14). Amphibolesintergrowths from with meso- nepheline and melanocratic (see Figure 5c,d). rocks are characterized by an increased content of Ca (up to 0.28 apfu),In Al meso- (up toand 0.30 melanocraticapfu) and Tirocks, (up tocations 0.28 apfuin the), whilecomposition amphiboles of amphiboles from leucocratic (only samples rocks and ﬁne-grainedwithout under-occupied nepheline syenite C-sites are and enriched over-occupied in К(up A- tosites) 0.71 apfuand ),coexisting Si and Mn clinopyroxenes (up to 0.52 apfucorrelate). closely with each other, with positive correlations between the same elements (Figure 15).

FigureFigure 14. Binary14. Binary diagrams diagrams showing showing majormajor and minor el elementement concentrations concentrations in amphiboles in amphiboles as a as a function of Al content. function of Al content.

In the metasomatic rocks, sodium-calcium (ferri-katophorite, richterite) and sodium (eckermannite) amphiboles along with aegirine-augite surround the augite relics. These amphiboles stand out clearly in binary diagrams (Figure 14) with high Ca (up to 0.46 apfu) and Al (up to 0.41 apfu) contents. Magnesioarfvedsonite is also characteristic of these rocks, but it forms symplectic intergrowths with nepheline (see Figure5c,d). Minerals 2019, 9, 581 20 of 31

In meso- and melanocratic rocks, cations in the composition of amphiboles (only samples without under-occupied C-sites and over-occupied A-sites) and coexisting clinopyroxenes correlate closely Mineralswith each 2017 other,, 7, x FOR with PEER positive REVIEW correlations between the same elements (Figure 15). 21 of 32

Figure 15. CorrelationCorrelation coefficients coefficients between between the the cations cations of of coexisting coexisting amphiboles amphiboles and and clinopyroxenes. clinopyroxenes. Black andand empty empty dots dots indicate indicate significant significant (p 0.05) (p and≤ 0.05) insignificant and insignificant correlation correlation coefficients, respectively.coefficients, ≤ respectively. 4.3.5. Eudialyte-Group Minerals (EGM) 4.3.5.Representative Eudialyte-Group analyses Minerals of EGM (EGM) and site occupancies calculated using the method of Johnsen and GriceRepresentative [36] are given in analyses Table5, Table of EGM6 and and TableS8 site occu (Suplementarypancies calculated Materials) using according the method the IMA-accepted of Johnsen andgeneral Grice formula [36] are given for the in Tables eudialyte-group 5, 6 and S8 (Suplementary minerals [37,38 Materials)]: N15[M according(1)]6[M(2)] the3[ MIMA-accepted(3)][M(4)]Z3 + general(Si24O72 )O’4X2,formula with N = Na,for Ca, K, Sr,the REE, Ba,eudial Mn, Hyte-group3O ; M(1) = Ca,minerals Mn, REE, Na,[37,38]: Sr, Fe; + – NM15(2)[M=(1)]Fe,6[M Mn,(2)] Na,3[M(3)][ Zr, Ta,M(4)] Ti,Z K,3(Si Ba,24O H723)O’4X; M2, (3,with 4) N= =Si, Na, Nb, Ca, Ti, K, W, Sr, Na; REE,Z = Ba,Zr, Mn, Ti, Nb;H3OO+;’ M=(1)O, = OH Ca,, – – – 2– 2– 4– Mn,H2O; REE,X = Na,H2O, Sr, Cl Fe;,F M,(2) OH = Fe,, CO Mn,3 ,Na, SO 4Zr,, SiOTa, 4Ti, .K, Ba, H3O+; M(3, 4) = Si, Nb, Ti, W, Na; Z = Zr, Ti, Nb; OThe’ = O, high OH zirconium–, H2O; X content= H2O, (aboveCl–, F–, 3OHapfu–, )CO is the32–, mainSO42–, feature SiO44–. of the most EGM samples. As a result, thereThe is an high excess zirconium of zirconium content remains (above after 3 apfuZ position) is the filling.main feature Thereremains of the most a possibility EGM samples. of zirconium As a result,to enter there the Mis(2)-site, an excess which of zirconium is not completely remains filledafter Z in position the majority filling. of theThere samples remains (Figure a possibility 16) and of in zirconiumthe M(3)-site, to enter where the there M(2)-site, is also awhich constant is not deficit completely of cations. filled The in resultsthe majority of the factorof the analysissamples of(Figure EGM 16)compositions and in the (FigureM(3)-site, 17) where indicate there that is Si also is replaced a constant by Zr; deficit therefore, of cations. we assigned The results excess of zirconiumthe factor analysisto the M of(3)-site. EGM compositions Zirconium dominates (Figure 17) in theindicateM(3)-site that Si in is 22% replaced of EGM by samples, Zr; therefore, Si prevails we assigned in 75% excesssamples, zirconium and niobium to the predominates M(3)-site. Zirconium in 3% samples. dominates However, in the M the(3)-site EGM in classification 22% of EGM [37 samples,] does not Si prevailsincludes in EGM 75% varietiessamples, with and aniobium predominant predominates Zr in any in position 3% samples. other However, than Z, and the such EGM EGM classification from the [37]Lovozero does not Eudialyte includes Complex, EGM va ofrieties course, with require a predominant an additional Zr study.in any Theposition remaining other samplesthan Z, and belong such to EGMthe eudialyte from the solid Lovozero solution Eudialyte (eudialyte Complex,ss)–kentbrooksite of course, series. require an additional study. The remaining samplesAccording belong to the factoreudialyte analysis solid results solution (Figure (eudialyte 17), thess)–kentbrooksite main scheme of series. isomorphic substitutions in eudialyteAccording is as to follows: the factor analysis results (Figure 17), the main scheme of isomorphic substitutions in eudialyte is as follows: Zr4+ + Al3+ + Ti4+ + Fe2+ + 3Na+ Si4+ + Nb5+ + Mn2+ + REE3+ + (Ca, Sr)2+. Zr4+ + Al3+ + Ti4+ + Fe2+ + 3Na+ ⇆ Si4+ + Nb5+ + Mn2+ + REE3+ + (Ca, Sr)2+. With an increase in the kentbrooksite endmemberendmember content, the concentrations of rare-earth elements increase, and with an increase in eudialytess endmember fraction, the contents of Zr and Al elements increase, and with an increase in eudialytess endmember fraction, the contents of Zr and Al increase. The anomalous Zr-rich EGM (Zr-rich eudialytess) are likely to have resulted from a sharp increase. The anomalous Zr-rich EGM (Zr-rich eudialytess) are likely to have resulted from a sharp shift of the main main equilibrium equilibrium to the left. In In zonal zonal EGM EGM grains grains (see (see Figure Figure 33e),e), transitiontransition fromfrom thethe graingrain cores to their marginal zones occurs on the following schemes: eudialytess kentbrooksite or Zr-rich cores to their marginal zones occurs on the following schemes: eudialytess→→ kentbrooksite or Zr-rich eudialytess eudialytess. Zonal EGM crystals were found only in meso-and melanocratic rocks; in eudialytess →→ eudialytess. Zonal EGM crystals were found only in meso-and melanocratic rocks; in other rocks, EGM form homogeneous grains. There are no significant differences in the composition of EGM from meso-, melano-, and leucocratic rocks. On average, EGM from meso- and melanocratic rocks contain more Fe2+ (median 1.18 apfu) and less Mn (median 1.04 apfu) than EGM from leucocratic rocks (median 0.65 Fe pfu and 1.16 Mn pfu). EGM from metasomatic rocks are enriched with Ca, Sr, Nb, and Fe. In the meso- and melanocratic rocks, the compositions of coexisting clinopyroxenes and EGM correlate with each other. With an increase in magnesium and calcium in clinopyroxene (diopside endmember), the calcium content in EGM growths linearly (r = 0.444 and 0.441, respectively). Minerals 2019, 9, 581 21 of 31

There are no signiﬁcant diﬀerences in the composition of EGM from meso-, melano-, and leucocratic rocks. On average, EGM from meso- and melanocratic rocks contain more Fe2+ (median 1.18 apfu) and less Mn (median 1.04 apfu) than EGM from leucocratic rocks (median 0.65 Fe pfu and 1.16 Mn pfu). EGM from metasomatic rocks are enriched with Ca, Sr, Nb, and Fe. In the meso- and melanocratic rocks, the compositions of coexisting clinopyroxenes and EGM correlate with each other. With an increase in magnesium and calcium in clinopyroxene (diopside endmember), the calcium content in EGM growths linearly (r = 0.444 and 0.441, respectively).

Table 5. Representative microprobe analyses of EGM, wt. %.

Fine-grained Metasomatic Rock. Malignite Ijolite Shonkinite Foyaite Urtite Nph- Syenite Rock Drill hole 28 28 117 117 44 44 117 156 147 154 154 160 154 156 Deep, m 153 * 153 ** 47 * 47 ** 50 * 50 ** 215 216 85 144 226 148 197 118

Nb2O5 0.49 0.39 0.67 0.73 0.72 0.71 0.35 1.22 0.81 0.71 0.36 1.11 0.64 1.62 SiO2 49.99 51.75 49.45 50.97 53.07 50.44 51.81 49.92 49.34 51.24 53.51 49.48 51.02 49.33 ZrO2 12.54 11.69 13.95 12.79 12.04 13.90 13.03 11.78 12.90 11.20 14.71 11.65 12.93 12.80 TiO2 0.66 0.46 0.61 0.36 0.38 0.66 0.65 0.52 0.70 0.75 1.01 0.56 0.65 0.29 Al2O3 0.22 0.15 0.16 0.10 0.07 0.22 0.17 0.23 0.22 0.10 0.14 0.21 0.24 0.16 Y2O3 b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. b.d. 0.84 La2O3 0.19 0.40 0.29 0.27 0.30 0.25 0.46 0.42 0.25 0.61 0.37 0.33 b.d. 0.25 Ce2O3 0.53 0.85 0.57 0.69 0.58 0.74 0.98 0.94 0.62 1.73 1.24 0.94 0.51 0.56 Nd2O3 0.32 0.33 0.37 0.39 0.17 0.19 0.33 0.39 0.19 0.68 0.39 0.32 b.d. 0.25 CaO 7.48 8.71 6.27 7.19 9.04 6.20 6.92 7.96 6.34 7.33 6.49 8.09 10.31 8.54 MgO 0.16 b.d. 0.08 0.03 0.09 0.12 b.d. b.d. 0.07 b.d. b.d. b.d. b.d. 0.20 FeO 3.42 1.87 2.90 3.00 3.11 3.73 1.07 5.00 3.03 0.32 2.66 4.54 1.64 4.73 MnO 2.29 2.89 1.95 2.10 2.31 1.93 2.96 1.95 2.75 4.06 2.64 2.18 1.58 2.44 SrO 1.30 1.28 2.05 1.97 1.84 1.55 3.13 2.17 1.48 2.20 2.28 2.32 1.28 3.70 BaO 0.18 0.22 b.d. b.d. 0.15 b.d. 0.76 b.d. 0.26 0.62 0.20 0.17 0.19 0.14 Na2O 16.02 15.97 15.32 13.19 12.46 16.14 13.39 15.51 14.68 15.47 9.49 14.69 12.50 11.35 K2O 0.24 0.18 0.29 0.22 0.19 0.29 0.23 0.27 0.25 0.47 0.19 0.22 0.28 0.32 Cl 1.51 1.17 1.30 1.08 1.04 1.27 1.46 1.56 1.27 0.98 1.67 1.44 1.27 1.58 О=Cl –0.34 –0.26 –0.29 –0.24 –0.23 –0.29 –0.33 –0.35 –0.29 –0.22 –0.38 –0.33 –0.29 –0.36 Total 95.71 96.86 94.63 93.75 96.27 96.76 95.91 97.93 93.58 97.26 95.28 96.47 93.48 97.15 Formula based on Si + Zr + Ti + Nb + Al + Hf = 29 apfu Nb 0.11 0.09 0.15 0.16 0.16 0.16 0.08 0.28 0.19 0.16 0.08 0.26 0.14 0.37 Si 25.40 25.81 25.07 25.52 25.81 25.10 25.46 25.45 25.20 25.75 25.13 25.48 25.34 25.23 Zr 3.11 2.84 3.45 3.12 2.85 3.37 3.12 2.93 3.21 2.75 3.37 2.92 3.13 3.19 Ti 0.25 0.17 0.23 0.13 0.14 0.25 0.24 0.20 0.27 0.28 0.36 0.22 0.24 0.11 Al 0.13 0.09 0.09 0.06 0.04 0.13 0.10 0.14 0.13 0.06 0.08 0.13 0.14 0.10 Y ------0.23 La 0.04 0.07 0.05 0.05 0.05 0.05 0.08 0.08 0.05 0.11 0.06 0.06 0.00 0.05 Ce 0.10 0.16 0.11 0.13 0.10 0.14 0.18 0.18 0.12 0.32 0.21 0.18 0.09 0.11 Nd 0.06 0.06 0.07 0.07 0.03 0.03 0.06 0.07 0.04 0.12 0.07 0.06 0.00 0.05 Ca 4.07 4.65 3.41 3.86 4.71 3.30 3.64 4.35 3.47 3.95 3.27 4.46 5.49 4.68 Mg 0.12 0.00 0.06 0.02 0.06 0.09 - - 0.05 - - - - 0.15 Fe2+ 1.45 0.78 1.23 1.25 1.26 1.55 0.44 2.13 1.29 0.13 1.04 1.95 0.68 2.02 Mn 0.99 1.22 0.84 0.89 0.95 0.81 1.23 0.84 1.19 1.73 1.05 0.95 0.67 1.05 Sr 0.38 0.37 0.60 0.57 0.52 0.45 0.89 0.64 0.44 0.64 0.62 0.69 0.37 1.10 Ba 0.04 0.04 - - 0.03 - 0.15 - 0.05 0.12 0.04 0.03 0.04 0.03 Na 15.77 15.44 15.06 12.81 11.75 15.57 12.76 15.33 14.54 15.08 8.64 14.67 12.03 11.25 K 0.16 0.12 0.19 0.14 0.12 0.18 0.14 0.18 0.16 0.30 0.12 0.15 0.18 0.21 Cl 1.30 0.99 1.12 0.91 0.86 1.07 1.22 1.35 1.10 0.83 1.33 1.25 1.07 1.37 Sum 52.18 51.91 50.61 48.78 48.58 51.17 48.58 52.79 50.40 51.50 44.11 52.21 48.55 49.92 *—core of zonal grain; **—edge of zonal grain. Minerals 2019, 9, 581 22 of 31

Table 6. Site occupancies of EGM from Table5, apfu.

Fine-grained Metasomatic MineralsRock 2017, 7, x FOR Malignite PEER REVIEW Ijolite Shonkinite Foyaite Urtite 23 of 32 Nph-Syenite Rock

Drill hole 28 28Table 117 6. 117Site occupancies 44 44 of 117EGM from 156 Table 147 5, 154apfu. 154 160 154 156 Interval, m 153 * 153 ** 47 * 47 ** 50 * 50 ** 215 216 85 144 226 148 197 118 Fine-grained Rock Malignite Ijolite Shonkinite Foyaite Urtite Metasomatic Rock Al(M4) 0.13 0.09 0.09 0.06 0.04 0.13 0.10 0.14 0.13 0.06Nph-Syenite 0.08 0.13 0.14 0.10 DrillSi hole (M4) 28 0.87 28 0.91 117 0.91 117 0.94 44 0.96 44 0.87117 0.90156 0.86147 0.87154 0.94154 0.92 160 0.87154 0.86 0.90156 Interval,Sum mМ 4153*1.00 153** 1.0047* 1.0047** 1.0050* 1.0050** 1.00215 1.00216 1.00 85 1.00 144 1.00 226 1.00 148 1.00 197 1.00 1.00118 Al(ZrM4) (Z ) 0.13 3.000.09 2.840.09 3.000.06 3.000.04 2.850.13 3.000.10 3.000.14 2.930.13 3.000.06 2.75 0.08 3.00 0.13 2.92 0.14 3.00 0.10 3.00 Si (TiM4) (Z ) 0.87 -0.91 0.160.91 -0.94 -0.96 0.140.87 -0.90 -0.86 0.070.87 -0.94 0.25 0.92 - 0.87 0.08 0.86 - 0.90 - SumNb М (4Z ) 1.00 -1.00 -1.00 -1.00 -1.00 0.011.00 -1.00 -1.00 -1.00 -1.00 - 1.00 - 1.00 - 1.00 - 1.00 - ZrSum (Z) Z 3.003.00 2.84 3.003.00 3.003.00 3.002.85 3.003.00 3.003.00 3.002.93 3.003.00 3.002.75 3.00 3.00 3.00 2.92 3.00 3.00 3.00 3.00 3.00 TiNb (Z ()M 3) - 0.110.16 0.09- 0.15 - 0.160.14 0.15- 0.16 - 0.080.07 0.28- 0.190.25 0.16 - 0.08 0.08 0.26 - 0.14 0.37 - NbSi (Z (M) 3)- 0.53- 0.90- 0.17- 0.580.01 0.85- 0.22- 0.56- 0.59- 0.33- 0.81 - 0.20 - 0.60 - 0.48 0.32 - SumTi( MZ 3) 3.00 0.253.00 0.013.00 0.233.00 0.133.00 -3.00 0.253.00 0.243.00 0.133.00 0.273.00 0.03 3.00 0.36 3.00 0.14 3.00 0.24 3.00 0.11 NbZr (M (3)M 3) 0.11 0.110.09 -0.15 0.450.16 0.120.15 -0.16 0.370.08 0.120.28 -0.19 0.210.16 - 0.08 0.37 0.26 - 0.14 0.13 0.37 0.19 SiSum (M3) M3 0.53 1.000.90 1.000.17 1.000.58 1.000.85 1.000.22 1.000.56 1.000.59 1.000.33 1.000.81 1.00 0.20 1.00 0.60 1.00 0.48 1.00 0.32 1.00 Ti(FeM (3)M 2) 0.25 1.450.01 0.780.23 1.230.13 1.25 - 1.26 0.25 1.550.24 0.440.13 2.130.27 1.290.03 0.13 0.36 1.04 0.14 1.95 0.24 0.68 0.11 2.02 ZrMn (M3) (M 2)0.11 0.99- 1.220.45 0.840.12 0.89- 0.950.37 0.810.12 1.23- 0.840.21 1.19- 1.73 0.37 1.05 - 0.95 0.13 0.67 0.19 0.82 SumMg M (М3 2) 1.00 0.121.00 -1.00 0.061.00 0.021.00 0.061.00 0.091.00 -1.00 -1.00 0.051.00 - 1.00 - 1.00 - 1.00 - 1.00 0.15 FeSum (M2)М 2 1.45 2.560.78 2.001.23 2.131.25 2.161.26 2.281.55 2.450.44 1.672.13 2.971.29 2.540.13 1.86 1.04 2.10 1.95 2.90 0.68 1.35 2.02 3.00 Mn (M2) 0.99 1.22 0.84 0.89 0.95 0.81 1.23 0.84 1.19 1.73 1.05 0.95 0.67 0.82 Mn (M1) ------0.23 Mg (М2) 0.12 - 0.06 0.02 0.06 0.09 - - 0.05 - - - - 0.15 Ca (M1) 4.07 4.65 3.41 3.86 4.71 3.30 3.64 4.35 3.47 3.95 3.27 4.46 5.49 4.68 Sum М2 2.56 2.00 2.13 2.16 2.28 2.45 1.67 2.97 2.54 1.86 2.10 2.90 1.35 3.00 MnREE (M1)(M 1)- 0.19- 0.29- 0.23- 0.25- 0.19- 0.22- 0.32- 0.33- 0.20- 0.55 - 0.34 - 0.30 - 0.09 0.23 0.20 CaNa (M (1)M 1) 4.07 1.744.65 1.063.41 2.363.86 1.904.71 1.113.30 2.483.64 2.044.35 1.333.47 2.333.95 1.50 3.27 2.39 4.46 1.24 5.49 0.42 4.68 0.67 REEY( (MM1)1) 0.19 -0.29 -0.23 -0.25 -0.19 -0.22 -0.32 -0.33 -0.20 -0.55 - 0.34 - 0.30 - 0.09 - 0.20 0.23 NaSum (M1)М 1 1.74 6.001.06 6.002.36 6.001.90 6.001.11 6.002.48 6.002.04 6.001.33 6.002.33 6.001.50 6.00 2.39 6.00 1.24 6.00 0.42 6.00 0.67 6.00 Y Na(M1) ( N)- 14.04- 14.38- 12.69- 10.91- 10.64- 13.09- 10.72- 14.00- 12.21- 13.58 - 6.24 - 13.43 - 11.62 0.2310.59 SumK( МN1 ) 6.00 0.166.00 0.126.00 0.196.00 0.146.00 0.126.00 0.186.00 0.146.00 0.186.00 0.166.00 0.30 6.00 0.12 6.00 0.15 6.00 0.18 6.00 0.21 NaBa( (N)N ) 14.04 0.04 14.38 0.0412.69 -10.91 -10.64 0.0313.09 -10.72 0.1514.00 -12.21 0.0513.58 0.12 6.24 0.04 13.43 0.03 11.62 0.04 10.59 0.03 K(SrN) ( N) 0.16 0.380.12 0.370.19 0.600.14 0.570.12 0.520.18 0.450.14 0.890.18 0.640.16 0.440.30 0.64 0.12 0.62 0.15 0.69 0.18 0.37 0.21 1.10 Ba(SumN) N 0.0414.61 0.04 14.91- 13.48 - 11.620.03 11.30- 13.720.15 11.90- 14.820.05 12.860.12 14.640.04 7.020.03 14.30 0.04 12.20 0.0311.92 Sr (N) 0.38 0.37 0.60 0.57 0.52 0.45 0.89 0.64 0.44 0.64 0.62 0.69 0.37 1.10 *—core of zonal grain; **—edge of zonal grain. Sum N 14.61 14.91 13.48 11.62 11.30 13.72 11.90 14.82 12.86 14.64 7.02 14.30 12.20 11.92

Figure 16. 16. ManganeseManganese versus versus Fe on Fe the on M(2) the M(2)site in site EG inM. EGM.For orientation, For orientation, endmembers endmembers are shown. are All—Alluaivite;shown. All—Alluaivite; Aq—Aqualite; Aq—Aqualite; Ce-Zir—Ce-Zirsil Ce-Zir—Ce-Zirsilite;ite; Eud—eudialyte; Eud—eudialyte; Kent—Kentbrooksite; Kent—Kentbrooksite; On— Oneillite;On—Oneillite; Ras—Raslakite; Ras—Raslakite; Tas—Taseqite; Tas—Taseqite; (Mn,Ca)-ord. (Mn,Ca)-ord. Eud— Eud— (Mn,Ca)-ordered (Mn,Ca)-ordered eudialyte. eudialyte. Minerals 2019, 9, 581 23 of 31

Minerals 2017, 7, x FOR PEER REVIEW 24 of 32

Figure 17. ResultsResults of factor analyses of EGM compositions.compositions. Var.—variables; Var.—variables; Expl.var.—Explained variance; Prp.totl—proportion of total variance. Factor loadings > |0.5| |0.5| are are shown shown in in bold. bold.

5. Discussion Discussion IfIf apo-basalt metasomatic metasomatic rocks rocks are are not taken in intoto consideration, the the Eudialyte Complex Complex of of the Lovozero MassifMassif isis composed composed of of igneous igneous rocks rocks that that can becan formally be formally subdivided subdivided into nepheline into nepheline syenites syenites(shonkinite, (shonkinite, malignite malignite and foyaite) and andfoyaite) foidolites and foidolites {melteigite, {melteigite, ijolite and ijolite urtite and (Figure urtite2b)}. (Figure Based 2b)}. on Basedthe petrochemical on the petrochemical (Figure6), (Figure petrographic, 6), petrographic, and mineralogical and mineralogical data, these data, rocks these should rocks be should divided be dividedinto other into groups. other Thegroups. first groupThe first includes group hypersolvus includes hypersolvus meso- and melanocraticmeso- and melanocratic rocks (shonkinite, rocks (shonkinite,malignite, melteigite malignite, and melteigite ijolite) containing and ijolite) 30 cont or moreaining modal 30 or %more of mafic modal minerals. % of mafic These minerals. rocks contain These “streams”rocks contain of dark-colored“streams” of mineralsdark-colored (Figure minerals3a,b), have(Figure a trachytoid3a,b), have structurea trachytoid (Figure structure3a), and (Figure are 3a),enriched and are with enriched EGM. The with (Na EGM.2O + TheK2O) (Na/Al2OO3 + ratioK2O)/Al for these2O3 ratio rocks for ranges these fromrocks 0.83 ranges to 1.88 from (Figure 0.83 7to). 1.88 (FigureThe second 7). group includes subsolvus leucocratic rocks (foyaite, fine-grained nepheline syenite, urtite),The where second albite group appears includes as primary subsolvus magmatic leucocratic mineral rocks that (foyaite, present fine-grained along with microcline-perthitenepheline syenite, urtite),(Figure 4wherea,c,e). Thisalbite group appears is characterized as primary bymagmat an elevatedic mineral phosphorus that present content along (Figure with6) responsiblemicrocline- perthitefor the formation (Figure 4a,c,e). of various This phosphates group is characterized and silico-phosphates by an elevated (Figure phosphorus4b). Also, the content leucocratic (Figure rocks 6) responsiblecontain primary for the minerals formation of the of lovozerite various groupphosphates (Figure and4d). silico-phosphates Ratio (Na 2O + K2 O)(Figure/Al2O 34b).in these Also, rocks the leucocraticranges from rocks 0.71 tocontain 0.95 (Figure primary7). minerals of the lovozerite group (Figure 4d). Ratio (Na2O + K2O)/Al2O3 in these rocks ranges from 0.71 to 0.95 (Figure 7). The relationships of rock-forming minerals of meso- and melanocratic rocks suggest that felsic minerals, namely alkali feldspar and nepheline, crystallized first. The earliest mineral was alkali feldspar (microcline) because the morphology and mutual orientation of its crystals (Figure 3a,b) Minerals 2019, 9, 581 24 of 31

The relationships of rock-forming minerals of meso- and melanocratic rocks suggest that felsic minerals, namely alkali feldspar and nepheline, crystallized first. The earliest mineral wasMinerals alkali 2017 feldspar, 7, x FOR PEER (microcline) REVIEW because the morphology and mutual orientation of25 of its 32 crystals (Figure3a,b) indicate crystallization under conditions of free flow of magma [ 39,40]. In addition, thereindicate are inclusionscrystallization of alkaliunder feldsparconditions in of nepheline free flow (Figuresof magma3c and[39,40]. 18 b),In butaddition, not vicethere versa. are It is convenientinclusions toof alkali consider feldspar the crystallizationin nepheline (Figures of felsic 3c and minerals 18b), but using not vice the versa. “petrogeny’s It is convenient residua to system” consider the crystallization of felsic minerals using the “petrogeny’s residua system” NaAlSiO4- NaAlSiO4-KAlSiO4-SiO2-H2O[41,42]. Phase equilibria in this system (Figure 18a) for “dry” conditions KAlSiO4-SiO2-H2O [41,42]. Phase equilibria in this system (Figure 18a) for “dry” conditions are are defined in [43], and for PH2O = 1 kbar, phase equilibria can be found in [44]. defined in [43], and for PH2O = 1 kbar, phase equilibria can be found in [44].

Figure 18. (a)—phase equilibrium diagram of the system NaAlSiO4-KAlSiO4-SiO2-H2O for PH2O = 0 Figure 18. (a)—phase equilibrium diagram of the system NaAlSiO4-KAlSiO4-SiO2-H2O for kbar and PH2O = 1 kbar (univariant lines after [43,44]); m, n—points of thermal minima for PH2O = 0 kbar PH2O = 0 kbar and PH2O = 1 kbar (univariant lines after [43,44]); m, n—points of thermal minima for (m) and PH2O = 1 kbar (n). Plot of the felsic normative compositions of the melanocratic (dark gray area) P = 0 kbar (m) and P = 1 kbar (n). Plot of the felsic normative compositions of the melanocratic H2Oand leucocratic (gray area)H2O rocks in comparison with the average composition of Eudialyte Complex (dark gray area) and leucocratic (gray area) rocks in comparison with the average composition of (red point) and Layered Complex (black point), points are calculated after [14]. (b)—co-crystallization Eudialyteof nepheline, Complex microcline (red and point) aegiri andne in Layered malignite Complex 147/221, BSE-image. (black point), points are calculated after [14]. (b)—co-crystallization of nepheline, microcline and aegirine in malignite 147/221, BSE-image. Figurative points corresponding to the rocks of the (meso-)melanocratic group form an area extendingFigurative from points the field corresponding of feldspar solid to the soluti rockson ofto thenepheline–feldspar (meso-)melanocratic cotectic group(Figure form 18a). an area extendingCompared from with the the field average of feldspar composition solid solution of the Eu todialyte nepheline–feldspar Complex (red cotecticpoint in (Figure Figure 1818a),a). the Compared withnormative the average composition composition of melanocratic of the Eudialyterocks is enriched Complex in feldspar. (red point Alkaline in Figure feldspar 18 crystallizeda), the normative compositionfirst from the of magmatic melanocratic melt that rocks spread is enriched laterally. inIts feldspar.fractionation Alkaline quickly feldsparchanged the crystallized composition first from theof magmaticthe melt towards melt cotectic that spread and joint laterally. crystallization Its fractionation of nepheline-I quickly and microcline changed began. the compositionThe position of the meltof this towards cotectic cotectic was closer and to joint the “dry” crystallization condition (P of = nepheline-I1 atm) due to and the microclineinitially reducing began. nature The of position alkaline magma [7–9]. As a result, euhedral crystals of nepheline-I with small inclusions of microcline of this cotectic was closer to the “dry” condition (P = 1 atm) due to the initially reducing nature were formed (see Figures 3c and 18b). The formation of similar nepheline–feldspar (pseudoleucite- oflike) alkaline intergrowths magma in [7 the–9]. process As a of result, cotectic euhedral crystallization crystals is considered, of nepheline-I for example, with small in work inclusions of of microclineDavidson were[45]. Co-crystallization formed (see Figures of nepheline-I3c and 18andb). microcline The formation is supported of similar by the nepheline–feldsparcorrelation of (pseudoleucite-like)nepheline-I composition intergrowths with Fe content in the in process microcline of cotectic (see Figure crystallization 11a). The constant is considered, admixture for of example, inferric work iron of in Davidson microcline [45 and]. nepheline Co-crystallization indicates a ofhigh nepheline-I Fe3+/Fe2+ ratio and already microcline in the early is supported stages of by the correlationthe rock crystallization. of nepheline-I The composition oxidized state with of iron Fe is content probably in due microcline to the “alkali-ferric-iron (see Figure 11 effect”a). The [46] constant admixtureand this effect of ferric increases iron in with microcline decreasing and temperature. nepheline indicates a high Fe3+/Fe2+ ratio already in the early ° stagesThe of the crystallization rock crystallization. temperature The of oxidized nepheline-I state is of500–775 iron is probablyC ([31], Figure due to 9). the The “alkali-ferric-iron highest efftemperaturesect” [46] and probably this effect indicate increases liquidus with state, decreasing whereas temperature. the lowest temperatures mark the transition to subsolidus hydrothermal conditions. The crystallization temperature of alkali feldspar from The crystallization temperature of nepheline-I is 500–775 C ([31], Figure9). The highest (meso-)melanocratic rocks is estimated below 700 °C (Figure 19a). However,◦ since the rocks are temperatureshypersolvus, probablythe temperature indicate of feldspar liquidus crystallization state, whereas cannot the be lowest lower temperatures than 650 ± 10°C mark [47]. the transition to subsolidusAfter the hydrothermalcrystallization of conditions.microcline (and The nepheline-I), crystallization the magmatic temperature melt lost of its alkaliability feldsparto flow from (meso-)melanocraticfreely. Microcline-perthite rocks is is the estimated only mineral below with 700 deformed◦C (Figure crystals 19a). (see However, Figure 3a), since and the this rocks are hypersolvus,deformation theoccurred temperature before ofits feldsparexsolution crystallization into microcline cannot and albite. be lower Long-prismatic than 650 10aegirine-C[47]. ± ◦ (augite) crystals are subparallel-oriented only in sections perpendicular to trachytoid plane. In sections that are parallel to the trachytoid plane, aegirine-(augite) crystals are irregularly oriented. Thus, after the crystallization of microcline (and nepheline-I), there was a transition from magmatic flow (suspension-like behavior) to “submagmatic flow” (flow with less than the critical amount of melt for suspension-like behavior) [40]. Minerals 2019, 9, 581 25 of 31 Minerals 2017, 7, x FOR PEER REVIEW 26 of 32

FigureFigure 19. 19.Compositions Compositions of of felfspars felfspars and and clinopyrox clinopyroxensens from from rocks rocks of the of Alluaiv the Alluaiv site: (a)—total site: (a range)—total rangeof reintegrated of reintegrated feldspar feldspar compositions compositions (red (red line) line) plotted plotted on onthe the temperature-dependent temperature-dependent feldspar feldspar solvus,solvus, modiﬁed modified after after [ 48[48]] (from (from meso-meso- andand melanocraticmelanocratic rocks). (b (b)—total)—total range range of ofmagmatic magmatic clinopyroxeneclinopyroxene compositions compositions (gray(gray ﬁeld,field, generalizedgeneralized from Figure 11a).11a). 1–5—clinopyroxene 1–5—clinopyroxene trends trends fromfrom other other alkaline alkaline suites suites are are shown shown forfor comparison:comparison: (1) (1) Murun, Murun, Siberia Siberia [49], [49 ],(2) (2) Lovozero, Lovozero, Kola Kola PeninsulaPeninsula [50 [50],], (3) (3) Uganda Uganda [ 51[51],], (4) (4) SouthSouth QoroqQoroq [[52],52], (5) Ilímaussaq Ilímaussaq [53]. [53].

AfterIn the the rocks crystallization of the Lovozero of microcline Eudialyte (and Complex, nepheline-I), the calcium the magmatic content meltis low; lost for its ability(meso) to flowmelanocratic freely. Microcline-perthite rocks, the average isvalue the onlyis 1.81 mineral wt. % CaO with [14]. deformed When alkali crystals feldspar (see Figurewas fractionated,3a), and this deformationcalcium accumulated occurred before in the its exsolutionmelt. It is intoknown microcline that pure and albite.aegirine Long-prismatic is not stable aegirine-(augite)at magmatic crystalstemperatures, are subparallel-oriented but even an insignificant only in increase sections inperpendicular the calcium content to trachytoid served asplane. a trigger In for sections the aegirine crystallization [53,54]. The essence of this phenomenon is described in the work of Nolan that are parallel to the trachytoid plane, aegirine-(augite) crystals are irregularly oriented. Thus, [55] devoted to the albite-nepheline-aegirine-diopside system. This system includes two main after the crystallization of microcline (and nepheline-I), there was a transition from magmatic flow components of clinopyroxene solid solutions (аegirinе and diopside) and complements the region of (suspension-like behavior) to “submagmatic flow” (flow with less than the critical amount of melt for residual petrogenetic system, which is poor in potassium and not saturated with silica. The addition suspension-like behavior) [40]. of the diopside component to the clinopyroxene solution substantially changes the volume of the phaseIn the fields, rocks and of thethe Lovozero field of clinopyroxene Eudialyte Complex, increase thes significantly. calcium content This is effect low; for can (meso) be traced melanocratic to the rocks, the average value is 1.81 wt. % CaO [14]. When alkali feldspar was fractionated, calcium composition of Aeg50Di50, after which the volume of the clinopyroxene solid solution remains almost accumulatedunchanged. in the melt. It is known that pure aegirine is not stable at magmatic temperatures, but evenAs ana result, insignificant after the increaseformation in of the alkali calcium feldspar content crystals served and asalmost a trigger simultaneously for the aegirine with crystallizationnepheline-I, [clinopyroxene53,54]. The essencebegan ofto thiscrystallize. phenomenon Initially, is described aegirine-(augite) in the work crystallized of Nolan by [55 ] devotedheterogeneous to the albite-nepheline-aegirine-diopside nucleation on the faces of growing system. nepheline This crystals system (but includes not feldspar two main ones). components It can ofbe clinopyroxene assumed that solid the crystallizat solutionsion (aegirin of nephelineеand diopside) "consumes and less complements oxygen" (the the ratio region of the of sum residual of petrogeneticcations to oxygen system, in whichnepheline is poor is 3/4, in and potassium in the mi andcrocline not is saturated 2.5/4), and with for the silica. formation The addition of aegirine- of the diopside(augite) component under reducing to the conditions clinopyroxene, an oxygen solution donor substantially is needed changes[6]. the volume of the phase fields, and theThe field next of stage clinopyroxene of the formation increases of (meso-)melanocratic significantly. This erocksffect canwas bea large-scale traced to thecrystallization composition of of Aegaegirine-(augite)50Di50, after which together the volumewith nepheline-II. of the clinopyroxene Nepheline-II solid is enriched solution in remainsQtz endmember almost unchanged.not because of Asthe higher a result, temperature after the of formation its crystall ofization, alkali but feldspar due to crystalsthe occurrence and almost of Fe3+ impurity simultaneously during the with nepheline-I,substitution clinopyroxene ⬜B + (Si4+ + Fe began3+)T ⇆ to K crystallize.+B + 2Al3+T. Therefore, Initially, aegirine-(augite) nepheline-II cannot crystallized be used byto heterogeneousestimate the nucleationtemperature. on the Aegirine-(augite) faces of growing from nepheline meso-melanoc crystalsratic (but and not leucocratic feldspar ones). rocks Itare can identical be assumed in Mg- that 2+ 2+ the(Fe crystallization+Mn)-Na ratio of (see nepheline Figure 12 “consumesа,b). The sum less Fe oxygen”+ Mn increases (the ratio mainly of the due sum to ofmanganese cations to (Table oxygen 3), i.e., all iron during the clinopyroxene crystallization was in trivalent state. Magnesium (diopside in nepheline is 3/4, and in the microcline is 2.5/4), and for the formation of aegirine-(augite) under endmember) enters clinopyroxene in the minimal amounts necessary only to stabilize it in magmatic reducing conditions, an oxygen donor is needed [6]. conditions. The reason is the low calcium content in the melt. All clinopyroxenes are enriched with The next stage of the formation of (meso-)melanocratic rocks was a large-scale crystallization of Na and Fe3+, and located at the top of the fractionation trend (Figure 19b). Obviously, the rocks of the aegirine-(augite) together with nepheline-II. Nepheline-II is enriched in Qtz endmember not because Eudialyte Complex are the most evolved (fractionated) among the alkaline rocks of the Lovozero 3+ ofMassif. the higher temperature of its crystallization, but due to the occurrence of Fe impurity during the 4+ 3+ + 3+ substitutionCompositionB + (Si of clinopyroxenes+ Fe )T K thatB + form2Al “streams”T. Therefore, in meso-melanocratic nepheline-II cannot rocks be cannot used to be estimate used theto temperature. assess the2 oxygen Aegirine-(augite) fugacity due to fromthe “alkali-ferric-iron meso-melanocratic effect” and [46]; leucocratic increased contents rocks are of identicalTi, Zr, Al in Minerals 2019, 9, 581 26 of 31

Mg-(Fe2++Mn)-Na ratio (see Figure 12a,b). The sum Fe2+ + Mn increases mainly due to manganese (Table3), i.e., all iron during the clinopyroxene crystallization was in trivalent state. Magnesium (diopside endmember) enters clinopyroxene in the minimal amounts necessary only to stabilize it in magmatic conditions. The reason is the low calcium content in the melt. All clinopyroxenes are enriched with Na and Fe3+, and located at the top of the fractionation trend (Figure 19b). Obviously, the rocks of the Eudialyte Complex are the most evolved (fractionated) among the alkaline rocks of the Lovozero Massif. Composition of clinopyroxenes that form “streams” in meso-melanocratic rocks cannot be used to assess the oxygen fugacity due to the “alkali-ferric-iron effect” [46]; increased contents of Ti, Zr, Al and Mn in the clinopyroxenes indicate their rapid crystallization [56,57] and absence of the zirconium and titanium minerals at that time [58]. The antipathy of titanium and zirconium in clinopyroxenes (Figure 12a) has been established in other alkaline complexes, for example, Mont Saint-Hilare [59], Ilímaussaq [60]. Larsen [60] suggests that “ ... these elements competed with varying success for a limited number of lattice sites”. The composition of amphiboles is completely correlated with the composition of coexisting clinopyroxenes (see Figure 15), i.e., crystallization switched from clinopyroxene to amphibole, probably because of rising PH2O. The amphiboles do not contain zirconium but include titanium (due to crystal-chemical reasons), and the Na/Ca ratio in amphiboles is on average 24, which is twice as much as in clinopyroxenes. The early formation of EGM is incredible, as can be seen, for example, by comparing the compositions of the coexisting minerals: clinopyroxenes contain elevated concentrations of manganese, while the M2 position (Fe2+, Mn, Mg) in the EGM constantly suffers from cation deficiency (see Figure 16). This means that the zirconium and calcium minerals, including EGM, crystallized together with amphiboles, but after clinopyroxenes. It disproves the hypothesis about early-magmatic formation of EGM [14,61]. In meso- and melanocratic rocks, the primary natrolite and sodalite crystallized simultaneously with amphiboles and EGM (see Figure3c,d). Considering that sodic amphiboles are stable only at low temperatures (below 650 ◦C) and pressures [62,63] and dehydration temperature of natrolite is 350 ◦C[64], we can conclude that the primary natrolite crystallized almost simultaneously with alkaline amphiboles and EGM as a result of an increase in PH2O. The binding of water in the composition of natrolite causes a decrease in the chlorine solubility and, consequently, the formation of sodalite. In this case, zonal natrolite–sodalite segregations appear, whose core consists of natrolite, the intermediate zone is composed of natrolite and sodalite, and the marginal zone consists of sodalite (Figure3d). Thus, meso-melanocratic rocks were formed at temperatures ranging from 650–700 ◦C to about 350 ◦C. As the rocks crystallize in this temperature interval, a gradual transition from an almost anhydrous HSFE-, Fe3+-, halogen-rich alkaline melt to the NaCl-rich water solution occurred. Figurative points of leucocratic rocks (foyaite, urtite, fine-grained nepheline syenite) on the diagram of the “petrogeny’s residua system”, continue the field belonging to the points of meso-melanocratic rocks towards nepheline (see Figure 18a). The field of leucocratic rocks is located near the thermal minimum, but unlike meso-melanocratic rocks, this minimum is not “dry” (point m), but corresponds to PH2O = 1 bar (point n). Indeed, signs of simultaneous crystallization of microcline and nepheline are observed in foyaites and urtites, namely the inclusion of microcline in nepheline (see Figure4a) and interrelation between microcline and nepheline compositions. The presence of primary albite in these rocks together with microcline-perthite indicates a high PH O and low temperature ( 550 C) of 2 ≈ ◦ mineral crystallization [65,66]. Amphiboles from meso-melanocratic rocks (enriched with Ca and Al) and leucocratic rocks (enriched with Si and Na) constitute the primary magmatic trend ([63], Figure 14). The Mn/Fe ratio in EGM is a fractionation indicator [38,67], and early-magmatic EGM are invariably dominated by Fe, whereas hydrothermal EGM can be virtually Fe-free and form pure Mn endmembers. EGM from leucocratic rocks are relatively rich in manganese. The melt, which the leucocratic rocks crystallized from, was formed in the process of fractional crystallization of the melanocratic melt enriched in Fe and HFSE. Fractionation of the melanocratic Minerals 2019, 9, 581 27 of 31 melt proceeded in the direction of enrichment with nepheline and a decrease in the aegirine content. A similar fractionation path occurs in the Na2O-Al2O3-Fe2O3-SiO2 system [68], where melt of the “ijolite” type (approximately 50% of aegirine) evolves towards “phonolitic eutectic” (approximately 10% of aegirine). Phonolite is similar in composition to a melt that is not saturated with silica at the minimum point of the “petrogeny’s residua system” NaAlSiO4-KAlSiO4-SiO2-H2O[41]. The residual nature of leucocratic rocks is also indicated by the association of accessory minerals [69]. Due to an excess of sodium silicate in these rocks, there are primary minerals of the lovozerite, lomonosovite, and murmanite groups. All these minerals have the highest possible percentage of sodium in the total cation number of the chemical formula. The texture of leucocratic rocks (coarse-grained, fine-grained or porphyritic) depends on the proximity of the melt composition to nepheline–feldspar cotectic and the crystallization rate. The crystallization of subsolvus fine-grained nepheline syenite began with albite (see Figure4a,b), followed by the almost simultaneous formation of microcline, nepheline, aegirine, and EGM. The simultaneous crystallization is indicated by correlations between compositions of coexisting minerals (Figure 11b). The leucocratic melt crystallized in situ, forming lenses (Figure4g), layers, interlayers in the mass of melanocratic rocks. At slower cooling, the possibility of the formation of relatively large microcline and nepheline appeared (Figure4a,c,e,f), and then a rapid and simultaneous crystallization of the main mass of the rock occurred. Among the alkaline rocks of the Lovozero Massif, xenoliths of basic volcaniclastic rocks are widely distributed [18]. These rocks underwent metasomatic treatment of varying intensity and survived in the Eudialyte Complex both unchanged (see Figure5a,b) and actually turned into nepheline syenites (see Figure5c,d). In these rocks, there are all signs of a gradual increase in the intensity of alkaline metasomatism, including gradual transitions from unchanged basalt to fenite with relicts of augite surrounded by the rims of aegirine-(augite) (see Figure 13), and characteristic intergrowth of nepheline and magnesioarfvedsonite due to their simultaneous crystallization (see Figure5d). This indicates the active supply of alkalis and the redistribution of calcium that localizes in fluorapatite and titanite. The duration of the thermal effect of alkaline melt on volcaniclastic rocks was small and, because of rapid cooling, feldspar remains homogeneous, but not completely exsolved into albite and ortoclase (Figure8). The wide variety of zirconium phases is due to the gradual increase in alkali concentration during fenitization. Early (relative to aegirine) crystallization of magnesioarfvedsonite indicates an elevated Si concentration and relatively low alkalinity, which also leads to the formation of zircon [59]. The relatively high fugacity of fluorine at the initial stage of fenitization [70] is also likely to favor the early formation of zircon, as demonstrated by the simultaneous formation of fluorapatite. The crystallization of aegirine leads to an increase in alkali content relative to silicon [71], which stabilizes parakeldyshite. EGM is formed later than parakeldyshite, at the final stage of fenitization.

6. Conclusions 1. The Eudialyte Complex of the Lovozero Massif is indistinctly layered. Among the hypersolvus (meso)-melanocratic alkaline rocks (shonkinite, malignite, melteigite, ijolite) enriched with EGM, there are layers and lenses of subsolvus leucocratic rocks (foyaite, ﬁne-grained foyaite and urtite) with phosphorus mineralization and primary lovozerite-group minerals. 2. Leucocratic rocks were formed in the process of fractional crystallization of melanocratic melt enriched in Fe, HFSE, and halogens. The fractionation of the melanocratic melt proceeded in the direction of enrichment in nepheline and a decrease in the aegirine content. In a similar way, individual “rhythms” of the Layered Complex were probably diﬀerentiated.

3. Hypersolvus meso-melanocratic rocks were formed in the temperature range from 650–700 ◦C to about 350 ◦C. As the rocks crystallized in this temperature range, a gradual transition from an almost anhydrous HSFE-, Fe3+-, halogen-rich alkaline melt to the Na(Cl, F)-rich water solution occurred. The temperature of crystallization of subsolvus leucocratic rocks was about 550 ◦C; Minerals 2019, 9, 581 28 of 31

4. If nepheline in alkaline rocks crystallizes simultaneously with aegirine, then it is enriched with Fe 4+ 3+ + 3+ and Si according to the scheme B + (Si + Fe )T K B + 2Al T. The composition of such nepheline cannot be used for thermometry2 purposes; 5. Devonian volcaniclastic rocks played an important role in the giant eudialyte deposit formation. The relatively high fugacity of fluorine at first stage of the basalt fenitization causes formation of zircon in apo-basalt metasomatites. Following aegirine crystallization and the corresponding increase in Na/Si ratio led to parakeldyshite formation. At the final stage, EGM replaced parakeldyshite under the influence of Ca-rich solutions produced by the basalt fenitization.

Supplementary Materials: The following are available online at http://www.mdpi.com/2075-163X/9/10/581/s1, Table S1: parameters of chemical analyses; Table S2: modal composition of rock; Table S3: wet chemistry analyses of rock; Table S4: microprobe analyses of feldspar; Table S5: microprobe analyses of nepheline; Table S6: microprobe analyses of clinopyroxene; Table S7: microprobe analyses of amphibole; Table S8: microprobe analyses of eudialyte-group minerals. Author Contributions: J.A.M. designed the experiments, participated in field works, performed statistical investigations and wrote the manuscript. A.O.K. participated in field works, performed geostatistical investigation, drew maps and reviewed the manuscript. Y.A.P. and A.V.B. took BSE images and performed electron microscope investigations. G.Y.I. and V.N.Y. conceived of the work, participated in field works, and reviewed the manuscript. All authors discussed the manuscript. Funding: The Kola Science Center of Russian Academy of Sciences (0226-2019-0051), the Russian Science Foundation (16-17-10173), and the Presidium of the Russian Academy of Sciences (Program No I-48) funded this research. Acknowledgments: We are grateful to anonymous reviewers from MDPI who helped us improve the presentation of our results. Conflicts of Interest: The authors declare no conflict of interest.

References

1. Le Maitre, R.W. (Ed.) Igneous Rocks. A Classification and Glossary of Terms; Cambridge University Press: Cambridge, UK, 2002; ISBN 9780521662154. 2. Frost, B.R.; Frost, C.D. A Geochemical Classification for Feldspathic Igneous Rocks. J. Petrol. 2008, 49, 1955–1969. [CrossRef] 3. Marks, M.A.W.; Markl, G. A global review on agpaitic rocks. Earth-Sci. Rev. 2017, 173, 229–258. [CrossRef] 4. Kalashnikov, A.O.; Konopleva, N.G.; Pakhomovsky, Y.A.; Ivanyuk, G.Y. Rare earth deposits of the Murmansk Region, Russia—A review. Econ. Geol. 2016, 111, 1529–1559. [CrossRef] 5. Krivovichev, S. Topological complexity of crystal structures: Quantitative approach. Acta Crystallogr. Sect. A Found. Crystallogr. 2012, 68, 393–398. [CrossRef][PubMed] 6. Markl, G.; Marks, M.A.W.; Frost, B.R. On the Controls of Oxygen Fugacity in the Generation and Crystallization of Peralkaline Melts. J. Petrol. 2010, 51, 1831–1847. [CrossRef] 7. Nivin, V.A.; Treloar, P.J.; Konopleva, N.G.; Ikorsky, S.V. A review of the occurrence, form and origin of C-bearing species in the Khibiny Alkaline Igneous Complex, Kola Peninsula, NW Russia. Lithos 2005, 85, 93–112. [CrossRef] 8. Beeskow, B.; Treloar, P.; Rankin, A.; Vennemann, T.; Spangenberg, J. A reassessment of models for hydrocarbon generation in the Khibiny nepheline syenite complex, Kola Peninsula, Russia. Lithos 2006, 91, 1–18. [CrossRef] 9. Schönenberger, J.; Markl, G. The Magmatic and Fluid Evolution of the Motzfeldt Intrusion in South Greenland: Insights into the Formation of Agpaitic and Miaskitic Rocks. J. Petrol. 2008, 49, 1549–1577. [CrossRef] 10. Chevychelov, V.Y.; Botcharnikov, R.E.; Holtz, F. Partitioning of Cl and F between fluid and hydrous phonolitic

melt of Mt. Vesuvius at ~850–1000 ◦C and 200 MPa. Chem. Geol. 2008, 256, 172–184. [CrossRef] 11. Dolejš, D.; Zajacz, Z. Halogens in Silicic Magmas and Their Hydrothermal Systems. In The Role of Halogens in Terrestrial and Extraterrestrial Geochemical Processes; Harlov, D.E., Aranovich, L., Eds.; Springer International Publishing: Cham, Switzerland, 2018; pp. 431–543. ISBN 978-3-319-61665-0. 12. Watson, E.B. Zircon saturation in felsic liquids: Experimental results and applications to trace element geochemistry. Contrib. Mineral. Petrol. 1979, 70, 407–419. [CrossRef] Minerals 2019, 9, 581 29 of 31

13. Keppler, H. Influence of fluorine on the enrichment of high field strength trace elements in granitic rocks. Contrib. Mineral. Petrol. 1993, 114, 479–488. [CrossRef] 14. Gerasimovsky, V.I.; Volkov, V.P.; Kogarko, L.N.; Polyakov, A.I.; Saprykina, T.V.; Balashov, Y.A. Geochemistry of the Lovozero Alkaline Massif ; Nauka: Moscow, Russia, 1966. (In Russian) 15. Kramm, U.; Kogarko, L.N. Nd and Sr isotope signatures of the Khibina and Lovozero agpaitic centres, Kola Alkaline province, Russia. Lithos 1994, 32, 225–242. [CrossRef] 16. Wu, F.-Y.; Yang, Y.-H.; Marks, M.A.W.; Liu, Z.-C.; Zhou, Q.; Ge, W.-C.; Yang, J.-S.; Zhao, Z.-F.; Mitchell, R.H.; Markl, G. In situ U–Pb, Sr, Nd and Hf isotopic analysis of eudialyte by LA-(MC)-ICP-MS. Chem. Geol. 2010, 273, 8–34. [CrossRef] 17. Mitchell, R.H.; Wu, F.-Y.; Yang, Y.-H. In situ U–Pb, Sr and Nd isotopic analysis of loparite by LA-(MC)-ICP-MS. Chem. Geol. 2011, 280, 191–199. [CrossRef] 18. Korchak, Y.A.; Men’shikov, Y.P.; Pakhomovskii, Y.A.; Yakovenchuk, V.N.; Ivanyuk, G.Y. Trap formation of the Kola peninsula. Petrology 2011, 19, 87–101. [CrossRef] 19. Shablinsky, G.N. On problem of deep structure of the Khibiny and Lovozero plutons. Trudy Leningradskogo Obshchestva Estestvoispytateley 1963, 74, 41–43. (In Russian) 20. Bussen, I.V.; Sakharov, A.S. Petrology of the Lovozero Alkaline Massif ; Nauka: Leningrad, Russia, 1972. (In Russian) 21. Arzamastsev, A.A. Unique Paleozoic Intrusions of the Kola Peninsula; Geological Institute of the Kola Science Centre: Apatity, Russia, 1994. 22. Pakhomovsky, Y.A.; Ivanyuk, G.Y.; Yakovenchuk, V.N. Loparite-(Ce) in rocks of the Lovozero layered complex at Mt. Karnasurt and Mt. Kedykvyrpakhk. Geol. Ore Depos. 2014, 56, 685–698. [CrossRef] 23. Vlasov, K.A.; Kuzmenko, M.Z.; Eskova, E.M. The Lovozero Alkaline Massif ; Izdatel’stvo Akademii Nauk: Moscow, Russia, 1959. (In Russian) 24. Pekov, I.V. Lovozero Massif: History of Investigations, Pegmatites, Minerals; Ocean Pictures Ltd.: Moscow, Russia, 2001. 25. Semenov, E.I. Mineralogy of the Lovozero alkaline massif ; Nauka: Moscow, Russia, 1972. (In Russian) 26. Dolivo-Dobrovolsky, D.D. MINAL, Free Software. Available online: http://www.dimadd.ru (accessed on 8 July 2013). 27. Hawthorne, F.C.; Oberti, R.; Harlow, G.E.; Maresch, W.V.; Martin, R.F.; Schumacher, J.C.; Welch, M.D. Nomenclature of the amphibole supergroup. Am. Mineral. 2012, 97, 2031–2048. [CrossRef] 28. Locock, A.J. An Excel spreadsheet to classify chemical analyses of amphiboles following the IMA 2012 recommendations. Comput. Geosci. 2014, 62, 1–11. [CrossRef] 29. StatSoft Inc, Statistica 13. Available online: www.statsoft.ru (accessed on 19 June 2018). 30. Systat Software Inc. TableCurve 2D. Available online: www.sigmaplot.co.uk/products/tablecurve2d/ tablecurve2d.php (accessed on 19 June 2018). 31. Hamilton, D.L. Nephelines as Crystallization Temperature Indicators. J. Geol. 1961, 69, 321–329. [CrossRef] 32. Yakovenchuk, V.N.; Ivanyuk, G.Y.; Konoplyova, N.G.; Korchak, Y.A.; Pakhomovsky, Y.A. Nepheline of the Khibiny alkaline massif (Kola Peninsula). Proc. Rus. Mineral. Soc. 2010, 2, 80–91. (In Russian) 33. Ivanyuk, G.; Yakovenchuk,V.;Pakhomovsky,Y.; Konoplyova, N.; Kalashnikov,A.; Mikhailova, J.; Goryainov,P. Self-Organization of the Khibiny Alkaline Massif (Kola Peninsula, Russia). In Earth Sciences; Dar, I.A., Ed.; InTech: Rijeka, Croatia, 2012; ISBN 978-953-307-861-8. 34. Pfaff, K.; Krumrei, T.; Marks, M.; Wenzel, T.; Rudolf, T.; Markl, G. Chemical and physical evolution of the ‘lower layered sequence’ from the nepheline syenitic Ilímaussaq intrusion, South Greenland: Implications for the origin of magmatic layering in peralkaline felsic liquids. Lithos 2008, 106, 280–296. [CrossRef] 35. Hawthorne, F.C.; Ungaretti, L.; Oberti, R.; Bottazzi, P.; Czamanske, G.K. Li: An important component in igneous alkali amphiboles. Am. Mineral. 1993, 78, 733–745. 36. Johnsen, O.; Grice, J.D. The crystal chemistry of the eudialyte group. Can. Mineral. 1999, 37, 865–891. 37. Johnsen, O.; Ferraris, G.; Gault, R.A.; Grice, J.D.; Kampf, A.R.; Pekov, I.V.The nomenclature of eudialyte-group minerals. Can. Mineral. 2003, 41, 785–794. [CrossRef] 38. Schilling, J.; Wu, F.-Y.; McCammon, C.; Wenzel, T.; Marks, M.A.W.; Pfaff, K.; Jacob, D.E.; Markl, G. The compositional variability of eudialyte-group minerals. Mineral. Mag. 2011, 75, 87–115. [CrossRef] 39. Higgins, M.D. The origin of laminated and massive anorthosite, Sept Iles layered intrusion, Quebec, Canada. Contrib. Mineral. Petrol. 1991, 106, 340–354. [CrossRef] Minerals 2019, 9, 581 30 of 31

40. Paterson, S.R.; Vernon, R.H.; Tobisch, O.T. A review of criteria for the identiﬁcation of magmatic and tectonic foliations in granitoids. J. Struct. Geol. 1989, 11, 349–363. [CrossRef] 41. Bowen, N.L. Recent high-temperature research on silicates and its signiﬁcance in igneous geology. Am. J. Sci. 1937, 193, 1–21. [CrossRef]

42. Schairer, J.F. The alkali-feldspar join in the system NaAlSiO4-KAlSiO4-SiO2. J. Geol. 1950, 58, 512–517. [CrossRef] 43. Schairer, J.F.; Bowen, N.L. Preliminary report on equilibrium-relations between feldspathoids, alkali-feldspars, and silica. Trans. Am. Geophys. Union 1935, 16, 325. [CrossRef]

44. Hamilton, D.L.; MacKenzie, W.S. Phase-equilibrium studies in the system NaAlSiO4 (nepheline)–KAlSiO4 (kalsilite)–SiO2-H2O. Mineral. Mag. 1965, 34, 214–231. [CrossRef] 45. Davidson, A. Nepheline-feldspar intergrowth from Kaminak lake, Northwest Territories. Can. Mineral. 1970, 10, 191–206. 46. Carmichael, I.S.E.; Nicholls, J. Iron-titanium oxides and oxygen fugacities in volcanic rocks. J. Geophys. Res. 1967, 72, 4665–4687. [CrossRef]

47. Bowen, N.L.; Tuttle, O.F. The System NaAlSi3O8-KAlSi3O8-H2O. J. Geol. 1950, 58, 489–511. [CrossRef] 48. Elkins, L.T.; Grove, T.L. Ternary feldspar experiments and thermodynamic models. Am. Mineral. 1990, 75, 544–559. 49. Mitchell, R.H.; Vladykin, N.V. Compositional Variation of pyroxene and mica from the Little Murun ultrapotassic complex, Aldan Shield, Russia. Mineral. Mag. 1996, 60, 907–925. [CrossRef] 50. Korobeynikov, A.N.; Laaioki, K. Petrological Aspects of the Evolution of clinopyroxene Composition in the Intrusive Rocks of the Lovozero Alkali Massif. Geochem. Int. 1994, 31, 69–76. 51. Tyler, R.C.; King, B.C. The pyroxenes of the alkaline igneous complexes of eastern Uganda. Mineral. Mag. 1967, 36, 5–21. [CrossRef] 52. Stephenson, D. Alkali clinopyroxenes from nepheline syenites of the South Qôroq Centre, South Greenland. Lithos 1972, 5, 187–201. [CrossRef] 53. Larsen, L.M. Clinopyroxenes and coexisting maﬁc minerals from the alkaline Ilimaussaq intrusion, South Greenland. J. Petrol. 1976, 17, 258–290. [CrossRef]

54. Bailey, D.K. The stability of acmite in the presence of H2O. Am. J. Sci. 1969, 267, 1–16. 55. Nolan, J. Melting-relations in the system NaA1Si3O8–NaA1SiO4–NaFeSi2O6–CaMgSi2O6–H2O, and their bearing on the genesis of alkaline undersaturated rocks. Q. J. Geol. Soc. 1966, 122, 119–155. [CrossRef] 56. Coish, R.A.; Taylor, L.A. The eﬀects of cooling rate on texture and pyroxene chemistry in DSDP Leg 34 basalt: A microprobe study. Earth. Planet. Sci. Lett. 1979, 42, 389–398. [CrossRef] 57. Mollo, S.; Blundy, J.D.; Iezzi, G.; Scarlato, P.; Langone, A. The partitioning of trace elements between clinopyroxene and trachybasaltic melt during rapid cooling and crystal growth. Contrib. Mineral. Petrol. 2013, 166, 1633–1654. [CrossRef] 58. Jones, A.P.; Peckett, A. Zirconium-bearing aegirines from Motzfeldt, South Greenland. Contrib. Mineral. Petrol. 1981, 75, 251–255. [CrossRef] 59. Piilonen, P.C.; McDonald, A.M.; Lalonde, A.E. The crystal chemistry of aegirine from Mont Saint-Hilaire, Quebec. Can. Mineral. 1998, 36, 779–791. 60. Larsen, L.M. Sector zoned aegirine from the Ilímaussaq alkaline intrusion, South Greenland. Contrib. Mineral. Petrol. 1981, 76, 285–291. [CrossRef] 61. Kogarko, L.N.; Lazutkina, L.N.; Krigman, L.D. Conditions of Zirconium Concentraton in Magmatic Processes; Nauka: Moscow, Russia, 1988. (In Russian) 62. Ernst, W.G. Synthesis, Stability Relations, and Occurrence of Riebeckite and Riebeckite-Arfvedsonite Solid Solutions. J. Geol. 1962, 70, 689–736. [CrossRef] 63. Mitchell, R.H. A review of the compositional variation of amphiboles in alkaline plutonic complexes. Lithos 1990, 26, 135–156. [CrossRef] 64. Cruciani, G. Zeolites upon heating: Factors governing their thermal stability and structural changes. J. Phys. Chem. Solids 2006, 67, 1973–1994. [CrossRef] 65. Martin, R.F.; Bonin, B. Water and magma genesis; the association hypersolvus granite-subsolvus granite. Can. Mineral. 1976, 14, 228–237. 66. Brown, W.L.; Parsons, I. Towards a more practical two-feldspar geothermometer. Contrib. Mineral. Petrol. 1981, 76, 369–377. [CrossRef] Minerals 2019, 9, 581 31 of 31

67. Guarino, V.; Gennaro, R.D.; Melluso, L.; Ruberti, E.; Azzone, R.G. The Transition from Miaskitic to Agpaitic Rocks, as Highlighted by the Accessory Phase Assemblages in the Passa Quatro Alkaline Complex (SouthEastern Brazil). Can. Mineral. 2019, 57, 339–361. [CrossRef] 68. Bailey, D.K.; Schairer, J.F. The System Na O Al O Fe O SiO at 1 atmosphere, and the petrogenesis of 2 − 2 3− 2 3− 2 alkaline rocks. J. Petrol. 1966, 7, 114–170. [CrossRef] 69. Melluso, L.; Guarino, V.; Lustrino, M.; Morra, V.; De’Gennaro, R. The REE-and HFSE-bearing phases in the Itatiaia alkaline complex (Brazil) and geochemical evolution of feldspar-rich felsic melts. Mineral. Mag. 2017, 81, 217–250. [CrossRef] 70. Farges, F.; Ponader, C.W.; Brown, G.E. Structural environments of incompatible elements in silicate glass/melt systems: I. Zirconium at trace levels. Geochim. Cosmochim. Acta 1991, 55, 1563–1574. [CrossRef] 71. Mikhailova, J.A.; Pakhomovsky, Y.A.; Ivanyuk, G.Y.; Bazai, A.V.; Yakovenchuk, V.N.; Elizarova, I.R.; Kalashnikov, A.O. REE mineralogy and geochemistry of the Western Keivy peralkaline granite massif, Kola Peninsula, Russia. Ore Geol. Rev. 2017, 82, 181–197. [CrossRef]

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).