Evolution of mariupolite (nepheline syenite) in the alkaline Oktiabrski Massif (Ukraine) as the host of potential Nb–Zr–REE mineralization

    Evolution of mariupolite (nepheline syenite) in the alkaline Oktiabrski Massif (Ukraine) as the host of potential Nb–Zr–REE mineralization Magdalena Duma´nska-Słowik PII: DOI: Reference:

S0169-1368(15)30085-8 doi: 10.1016/j.oregeorev.2016.03.011 OREGEO 1760

To appear in:

Ore Geology Reviews

Received date: Revised date: Accepted date:

23 September 2015 14 March 2016 15 March 2016

Please cite this article as: Duma´ nska-Slowik, Magdalena, Evolution of mariupolite (nepheline syenite) in the alkaline Oktiabrski Massif (Ukraine) as the host of potential Nb–Zr–REE mineralization, Ore Geology Reviews (2016), doi: 10.1016/j.oregeorev.2016.03.011

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ACCEPTED MANUSCRIPT Evolution of mariupolite (nepheline syenite) in the alkaline Oktiabrski

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Magdalena Dumańska-Słowik

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Massif (Ukraine) as the host of potential Nb–Zr–REE mineralization

Department of Mineralogy, Petrography and Geochemistry, Faculty of Geology, Geophysics

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and Environmental Protection, AGH – University of Science and Technology, Kraków 30-059, 30 Mickiewicza Av., Poland, e-mail: [email protected]

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Abstract

Mariupolite, aegirine-albite nepheline syenite, outcropping only in the Oktiabrski massif in

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south-eastern Ukraine, is a potential resource of Nb, Zr and REE for future exploration and development. Some types of this rock can be also used in ceramics, glass and building industry and jewellery. Mariupolite is composed of (1) magmatic and (2) subsolidus and

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hydrothermal components. The magmatic assemblage includes zircon, aegirine, nepheline,

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albite, K-feldspar, pyrochlore, fluorapatite, fluorbritholite-(Ce) and magnetite. Alkalinecarbonate-chloride-rich fluids exsolved very early in the history of the rock, in a late stage of,

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or directly after, its consolidation, induced intensive high-temperature alteration of the primary mariupolite components resulted in formation of cancrinite, calcite, fluorite, REEbearing minerals such as monazite, parasite-(Ce), bastnäsite-(Ce), as well as sodalite, natrolite

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and hematite. The genesis of this peculiar mineralization seems to be associated with multistage magmatic and tectonic activity of the Ukrainian Shield and fluids mediated metasomatic processes. Keywords: nepheline syenite, matasomatism, sub-solidus alteration, REE minerals, rare metals

1. Introduction Alkaline rocks occur rarely in nature. They usually contain significant amounts of rare metals such as Li, Be, Nb, Ta, Zr, Th, REE and volatile components, mainly F and Cl. Hence, they are the source of various rare minerals (Sørensen, 1992), and show high potential for deposits of industry-important metals (Goodenough et al., 2016). The Ukrainian Shield is a unique province of Proterozoic (1.8–2.1 Ga) alkaline magmatism and includes ca. 50 known

ACCEPTED MANUSCRIPT massives and smaller occurrences of alkaline rocks, e.g. Chernigivka, Oktiabrski, Mala Tersa, Pokrovo–Kirievo, Kalchinski, Proskurovka, Antonivka and Yastrubetski, mostly of Proterozoic, rarely Palaeozoic (Devonian) in age (Krivdik, 2005; Krivdik et al., 2007;

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Ponomarenko et al., 2013). Only some of them are more than 1 km2 in area (Fig. 1). The

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alkaline rocks from the eastern province of the Ukrainian Shield exhibit different geochemical signatures (higher contents of incompatible rare elements such as Nb, Zr, REE) than the rocks

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from the western part, probably because of different geodynamic conditions. The rocks of the eastern part formed during the rifting, whereas the western ones are linked to compressional settings, i.e. subduction and collision (Krivdik, 2005; Ponomarenko et al., 2013).

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Mariupolite is a variety of nepheline-syenite, a silica-undersaturated rock, named by Morozewicz (1902; 1929) and taking its name from Mariupol, Sea of Azov, in Ukraine. It

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outcrops only in the Oktiabrski Massif, which is situated in the eastern province (Azov) of the Ukrainian Shield in south-eastern Ukraine. Mariupolite is a miaskitic nepheline syenite, though melanocratic varieties of mariupolites have an agpaitic index up to 1.5 owing to the

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presence of aegirine (Krivdik and Tkachuk, 1998; Sharygin et al., 2009). Albite, nepheline

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and aegirine are the main components, whereas zircon, pyrochlore, sodalite, natrolite, cancrinite, K-feldspar, annite, fluorbritholite-(Ce), fluorapatite, fluorite, calcite, parasite-(Ce),

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bastnäsite-(Ce), magnetite, hematite make up the accessory phases. Generally, the main mineral composition of mariupolite is constant; however, among these rocks many types can be distinguished, which differ in composition of accessory phases and show unique and variable texture features. Morozewicz (1929) identified such types of mariupolite as:

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leucocratic, melanocratic, fine-grained, porphyritic, zircon-bearing gneiss-like, sodalitecancrinite with britholite schlieren, coarse-grained, pegmatitic-like and many others. Mariupolite is a potential source of Nb, Ta, Zr and REE since it hosts sometimes abundant zircon, pyrochlore-group minerals, monazite-(Ce), fluorapatite, fluorbritholite-(Ce) and REE-bearing carbonates [parasite-(Ce), bastnäsite-(Ce)]. In the last century Nb and Zr were economically recovered from the alkaline rocks of the Oktiabrski massif (Volkova, 2001). Mariupolites are also rich in volatile components such as Cl and F, which were trapped by sodalite, fluorapatite, fluorbritholite-(Ce), fluorite and annite. Water-rich minerals of mariupolite are mainly represented by annite, cancrinite and natrolite. This study presents the evolution of the mariupolite along with hosted mineralization based on new data and author‟s previous works (Dumańska-Słowik et al., 2011-2015) to interpret the chemical processes involved in the magmatic and post-magmatic evolution of alkaline melt in the Oktiabrski Massif. Understanding the role of fluid assisted remobilization

ACCEPTED MANUSCRIPT processes in formation of these rocks is crucial since such fluids are capable of concentrating some rare elements like Zr, Nb, Ta, REE and Th to high abundances (vide Schönenberger et al. 2006). The compositions of the main mineral phases will be presented together with the

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distinction made between the primary rock components and a secondary assemblage resulting

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from subsolidus re-equilibration during mariupolite cooling. Based on the textural characteristics and mineral composition, the origin of the mariupolite is discussed. Finally, the

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possible paragentic sequence of main and accessory components of mariupolites is presented.

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2. Economic importance of alkaline rocks

The occurrences of alkaline rocks are mainly found in continental rift-related settings,

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rarely in oceanic islands in various parts of the world (Pirajno, 2015). Most of the intrusions have a quasi-circular shape with imperfect ring and block structure (e.g. Worley and Cooper,

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1995; Fall et al., 2007; Korobeinikov et al., 2000; Volkova 2000). They were formed during a

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period of intra-plate alkaline magmatism (e.g. Sorensen, 1997; Coulson, 2003; Fall et al., 2007) and are described as a succession of a few magma batches from one single mantle source, which intruded successively to 3-4 km depth (e. g. Schönenberger et al., 2006).

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Occasionally mantle derived magma can be contaminated by crustal material (e. g. Korobeinikov et al., 2000; Fall et al., 2007). The formation of peralkaline and alkaline complexes is also the result of late-magmatic processes involving aqueous fluids, which are

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capable of concentrating rare elements. To understand the role of fluid remobilization processes is of great importance for the geochemical evaluation of magma source, possible contamination processes and may lead to economically important enrichment of these rare elements in the alkaline host (Schönenberger et al., 2006). Hence, most of alkaline and peralkaline complexes of igneous rocks are known as a source of many rare elements such as Li, Be, Nb, Ta, REE, Zr, U and Th and of volatiles as F and Cl (Sørensen, 1992; 1997). They host a wealth of various exotic and rare mineral species, e.g. more than 500 in the Lovozero and Khibina complexes of the Kola Peninsula in Russia (Sørensen, 1997), about 400 in the Mont Saint-Hilaire, Quebec in Canada (Schilling et al., 2011), about 200 in the Ilimaussaq complex in South Greenland (Sørensen, 1997) and about 100 in the Oktiabrski massif in south-eastern Ukraine (Volkova, 2000) were recognized. Many of these rare-element containing minerals are frequently used in different branches of industry worldwide. Hence, alkaline and peralkaline rocks are of major and growing economic importance. The most

ACCEPTED MANUSCRIPT distinctive Khibina and Lovozero complexes are famous for apatite and loparite deposits, respectively. Alkaline massives in Ilimaussaq (Greenland), Saima (China) and Pilanesberg in South Africa host U deposits. REE and Zr mineralization abundantly occurs in the Kipawa

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and Red Wine complexes in Canada (Sørensen, 1997). Bayan Obo in China is the world‟s

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largest REE deposit (Kynicky et al. 2012) and almost 90% of REE entering the global market

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are derived from China (Goodenough et al 2016).

In the Oktiabrski massif the most important rare-element containing minerals are pyrochlore, zircon, fluorapatite, fluorbritholite-(Ce) and fluorite, monazite-(Ce), parasite-(Ce), bastnäsite-(Ce), all hosted in mariupolites, which together with microcline-nepheline

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pegmatites and metasomatites belong to potentially productive rocks of this massif. They could be the potential source of Nb, Zr and REE. The contents of these elements increase

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from pegmatites, mariupolites to metasomatites, together with the extent of metasomatic alteration in the rocks (Volkova, 2001). Unfortunately nowadays there is still very little

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information available on the exploration of this deposit or possible reserve estimate.

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Moreover the leucocratic types of mariupolites, enriched in plagioclase and nepheline and devoid of Fe-bearing dark minerals such as aegirine, are valuable silicate rocks, which can be

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used in ceramics and glass industry. Alternatively, the attractive decorative properties, i.e. bright colour, often blue due to the presence of sodalite, spotty texture together with good technical parameters and ability to creating a smooth and shiny surface by polishing make pegmatite types of mariupolite good for the stone and jewellery industries for production of

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functional artistic goods such as vases and clocks. Finally other varieties of these rocks could be valuable for the production of dimension stone used for indoor and outdoor design (Dumańska-Słowik et al., 2011a).

3. Geological setting The Oktiabrski alkaline massif (Priazov block of the Ukrainian Shield, SE Ukraine) has been known since Polish petrologist Joseph Morozewicz first described it in the late 19th century. The massif, which is 34 km2 in area, is part of a unique province of alkaline magmatism of Proterozoic age ca. 1.8 Ga (U-Pb zircon method; Volkova, 2000; 2001; Ponomarenko et al., 2013). It was formed at the platform stage of the Ukrainian Shield development and is associated with a systems of deep faults (Sviridov, 1973). Now it is

ACCEPTED MANUSCRIPT situated at the border line between the Volodarsk and the Oktiabrski deep faults. Such localization resulted in formation of block-style structure of the massif (Volkova, 2001). The Oktiabrski massif is oval-shaped with an N–S elongation. It has a somewhat

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irregular concentric structure: in the centre there are pulaskites, i.e., nepheline-bearing alkali

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feldspar syenites with variable proportions of dark minerals such as Na-bearing pyroxenes and amphiboles, fayalite and biotite, which are surrounded by foyaites. The latter are in turn

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enclosed by syenites. Mariupolites, the nepheline albite-aegirine syenites, forming veins of various thickness from a few centimetres to meters (Yanchenko et al., 2010), occur in the periphery of this alkaline complex (Fig. 2). They occur in the vicinity of peridotites,

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pyroxenites and gabbros (1), which are the oldest rocks in the massif (Volkova, 2001), or foyaites and pegmatites (2). Granitoid rocks are found only in the peripheral parts of the

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massif.

In the Oktiabrski massif, the agpaitic trend of melt differentiation was identified with the following rock succession: subalkaline gabbro and its derivatives (pyroxenite and

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peridotite) – alkaline syenites – taramite foyaites – mariupolites – aegirine foyaites –

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eudialite-bearing phonolites (Krividik et al., 2007). The development of the agpaitic trend was associated with an increase of trace elements: Zr, Nb, REE, Rb and a decrease of Sr, Ba, P

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and Ti (Krivdik and Tkachuk, 1998). Nevertheless, agpaitic rocks are generally scarce in this massif. The formation of such endogenic mineralization within this massif is associated mainly with multi stage tectonic-magmatic and metasomatic activity of Priazov block of the Ukrainian Shield (Volkova, 2000).

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The genesis of this massif has been under debate for a long time. Tichonienkova et al. (1967) believed that the rocks of the Oktiabrski Massif had formed as a result of postmagmatic and metasomatic alteration processes. The presence of sodic fenites, metasomatic rocks composed mainly of alkali feldspars, alkaline amphiboles (arfvedsonite, riebeckite), alkali-ferrohastingsite and subordinately of aegirine, nepheline, and carbonates, exposed within the alkaline massif in the Khlibodarivka quarry may support the thesis of intense metasomatic activity in this region (Dumańska-Słowik et al., 2015b). Donskoy (1982) and Solodov (1985) suggested that majority of the rocks had crystallized due to the differentiation of melt with the composition of nepheline syenite. However, they also agree that metasomatic activity, which affected the rocks, is responsible for the significant concentration of rare metals such as Nb, Zr and REE deposits hosted by the rocks of this massif (Volkova, 2001). Similarly, there is not a single point of view concerning the genesis of mariupolites. Donskoy (1982) summarized various opinions on the origin of these rocks:

ACCEPTED MANUSCRIPT (1) they could be formed at the late stage of melt differentiation when the medium was enriched in alkalis and volatile components; (2) fine-crystalline types of mariupolite crystallized from melt depleted in volatile components, whereas the other types of these rocks

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resulted from post-magmatic recrystallization; (3) the term „mariupolitization‟ was introduced

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for a type of alkaline metasomatism, characterized by aegirine followed by albitic alteration (fenitization). Nowadays, they are described as magmatic, metasomatic or dyke vein

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formations of the Oktiabrski Massif (Yanchenko et al., 2010).

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4. Analytical Methods

Samples of mariupolites were collected in 2008 both in the north and south part of the

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Oktiabrski Massif. In the north-east, at the Mazurovski field, mariupolites outcrop in association with mafic and ultramafic rocks, whereas in the south-east part (the Kalinino-

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Schevczenkovski field) they form veins found between foyaites and pegmatites (Fig.2). In

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both regions mariupolites seem to be heterogenous rocks, what is manifested mainly in variation in grain size, texture and modal proportions of subordinate components. The specimens of mariupolite were examined optically with an Olympus BX 51

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polarizing microscope.

Back-scattered electron (BSE) images of polished sections were obtained using a FEI Quanta 200 FEG scanning electron microscope equipped with an EDS detector. The system

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operated at 25 kV accelerating voltage in a high-vacuum mode. The cathodoluminescence observations were conducted at the Polish Geological Institute – National Research Institute in Warsaw on polished thin sections using a Cambridge Image Technology CCL 8200 MK3 device (cold cathode) linked to a Nikon Optiphot 2 polarising microscope. The scanning electron microscopy with cathodoluminescence (SEMCL) analyses utilised a LEO 1430 scanning electron microscope with the CL-image system (ASK-CL VIS Viev) and CL spectrometer (ASK SEM-CL). The XRD patterns for Na- and K-feldspars were recorded with a Philips PW 3020 X‟Pert-APD Diffractometer system (with a Cu anode and a graphite monochromator) at 35 kV voltage and 30 mA current, in the 2Θ range of 5–75o with a 0.01°(2Θ)/s step. The detailed investigations of feldspars structure were done using the method of three reflections proposed by Wright (1968). The degree of Al-Si ordering in K-feldspars was also calculated.

ACCEPTED MANUSCRIPT Electron-microprobe analyses of cancrinite were made at the Laboratory of Critical Elements of AGH University of Science and Technology – KGHM Polska Miedź S.A with a JEOL Super Probe JXA-8230 operating in a wavelength-dispersive (WDS) mode under the

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following conditions: accelerated voltage of 15 kV, beam current of 10 nA, peak count-time

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of 10 s and background time of 5 s. Standards, analytical lines, diffracting crystals and mean detection limits (wt%) were as follow: albite – Na (Kα, TAPH, 0.004), kyanite – Al (Kα,

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TAP, 0.004), albite – Si (Kα, TAP, 0.007), wollastonite – Ca (Kα, PETJ, 0.004), orthoclase – K (Kα, PETJ, 0.003), hematite – Fe (Kα, LIF, 0.015), MnO– Mn (Kα, LIFH, 0.005), sphalerite – Zn (Kα, LIFH, 0.013), forsterite – Mg (Kα, TAPH, 0.004), apatite – P (Kα, PETJ,

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0.009), rutile – Ti (Kα, LIFL, 0.007), barite – Ba (Lα, PETL, 0.005), SrSO4 – Sr (Lα, PETL, 0.007). The crystal-chemical formulae of feldspars and nepheline were calculated on the

oxygen atoms per formula unit (apfu).

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basis of 8 oxygens, whereas structural formula of aegirine was calculated on the basis of 6

The whole rock analyses were performed in the Actlabs Activation Laboratories Ltd.,

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Ancaster, Ontario, Canada. The abundances of major oxides and trace elements were

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determined using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) following a lithium

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metaborate/tetraborate fusion and dilute nitric digestion. Major oxides and trace elements were analyzed using Thermo Jarrell-Ash ENVIRO II ICP or a Spectro Cirros ICP and Perkin Elmer SCIEX ELAN 6000 ICP-MS, respectively. Calibration was performed using multiple United States Geological Survey (USGS) and Canada Centre for Mineral and Energy

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Technology (CANMET) certified reference materials such as NIST 694, DNC-1, GBW 07113 LKSD-3, TDB-1, W-2a, SY-4, CTA-AC-1, BIR-1a, NCS DC86312, ZW-C, NCS DC70009, (GBW07241), OREAS 100a (Fusion), OREAS 101a (Fusion), OREAS 101b (Fusion), JR-1. The results of the representative whole rock analyses are presented in Table 1.

5. Results 5.1 Textural variations Mariupolites are holocrystalline, from fine, medium- to coarse-grained rocks with the predominance of inequigranular over equigranular texture. The inequigranular (porphyritic) texture is characterized by the presence of large euhedral megacrysts of eagirine, zircon and annite and a finer-grained groundmass composed mostly of albite (Fig. 3A-B,G), which exhibits variable sizes, sometimes forming large tabular crystals, in other cases crystallized as

ACCEPTED MANUSCRIPT small needles. The constant mineral composition of megacrysts and groundmass along with variable morphology of albite in groundmass indicate turbulent, temperature and pressure conditions during crystallization of these rocks.

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Mariupolites show different types of textures: (1) oriented, trachytoid, and locally (2)

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spherulitic, (3) poikilitic, (4) corona texture (Fig. 3). The trachytoid texture, characterized by subparallel arrangement of tabular crystals of plagioclases, seems to be the most dominant

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texture within mariupolite. Albite, the main rock component, occurs in the same elongation direction and exhibits the same optical orientation within the rock. The rocks exhibit melt flow banding. The spherulitic texture is observed only in mariupolite types enriched in

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zeolite-group minerals, where natrolite forms crystals aligned radially from the centre of their crystallization (Fig.3F). Locally poikilitic and corona textures could be also observed. The

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corona texture is found where single pyrochlore crystals have been overgrown by a rim composed of a chlorite (Fig.3D), most probably as a result of the alteration of pyrochlore in subsolidus conditions (Dumańska-Słowik et al., 2014). The poikilitic textures are observed

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quite frequently, since the main components of mariupolite (oikocrysts) contain the vast

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oriented (Fig.3G).

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majority of inclusions of main and secondary phases (chadacrysts), which are randomly

5.2 General and Accessory Mineralogy Mariupolite hosts both barren minerals and components which are potentially a source

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of rare metals such as Zr, Nb and REE (Tab.2). Plagioclase (Ab100-96), which occurs as fine, prismatic crystals up to 0.5 mm in length with a few twin individuals, is the predominant mineral of mariupolite. It represents a lowtemperature albite, which is rather fresh without any mineral inclusions. Under CL albite show pink-red CL colours (Fig.4) characteristic of rocks fenitized by Fe-rich fluids (Dumańska-Słowik et al., 2015b). Nepheline forms large, dynamically deformed crystals with non-uniform light extinction. Some crystals of nepheline are relatively fresh, whereas others are strongly altered. Nepheline nearly always occurs at the contact with natrolite and sodalite. It hosts primary and secondary inclusions of albite, a pyrochlore-group mineral, annite, K-feldspar, cancrinite, natrolite, fluorite and sphalerite. Representative microprobe analyses of relatively fresh nepheline are presented in Table 3. The modal composition, plotted in the triangular diagram NaAlSiO4–KAlSiO4–SiO2 ranges from 71 to 73% Ne, 20–22% Ks and 5– 9 % Qz. Silica is

ACCEPTED MANUSCRIPT present in slight excess of stoichiometry as illustrated in Fig.5, which shows that nehpheline composition lies outside the Morozewicz–Buerger convergence field of plutonic nephelines (Tilley, 1954). Isotherms for the limits of solid solutions defined by Hamilton (1961) indicate

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that nepheline has equilibrated from 900–700°C.

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Clinopyroxene forms euhedral and prismatic crystals of varying size (Fig.3C,G) and shows strong pleochroism: α = green, β = pale green, γ = pale yellow-green characteristic of

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aegirine. It is relatively fresh, though some crystals are fractured and fuzzy at rims. It hosts mineral inclusions such as albite, K-feldspar, annite, zircon, britholite-(Ce) and Ti–Mn–Fe oxides/hydroxides.

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Zircon is abundant in the form of euhedral crystals with a characteristic oscillatory zoning along the grain margins, and irregular patchy zoning in the centre (Fig.6A). The

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oscillatory zoning is characteristic of magmatic stage of zircon formation, whereas the patchy zoning is attributed to the reaction of zircon with fluid during dissolution and recrystallization process. Zircon is strongly fractured; the numerous micropores are filled with inclusions such

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as albite, aegirine, a pyrochlore, annite, K-feldspar and bastnäsite-(Ce). Under CL, it is

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generally yellow in the centre with navy blue colours at its margins (Fig.4A-B). The CL spectra recorded for both yellow and navy blue domains as well as detailed chemistry of

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zircon are presented by Dumańska-Słowik et al. (2011b). Zircon is completely devoid of uranium and with a relatively monotonous composition with only some variations in REE2O3 and Th2O content between dark and light patches: i.e. 0.00–1.55 and 0.00–0.34 wt.%, respectively.

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Dark mica, i.e. annite, is of two generations in mariupolite: large fresh crystals and small altered flakes. It occurs as euhedral to subhedral flakes from 0.5 to 40 mm in size. Some crystals show pleochroic halos as a result of the presence of zircon inclusions. The large flakes of mica are relatively fresh (Fig.3A) and contain a wealth of inclusions, namely feldspars, aegirine, zircon, nepheline, a pyrochlore-group mineral, magnetite, hematite, natrolite, Ti–Mn oxides. The latter variety of dark mica exhibits some traces of an alteration to smectite and vermiculite. The detailed chemistry of dark micas are presented in DumańskaSłowik et al. (2015a), who noticed the fresh mica is enriched in fluorine (1.35–1.76 wt% F) and FeO (~27.40 wt.%) and depleted in Fe2O3 (2.42–3.38 wt.%), whereas the altered one is completely devoid of F and contains 23.32–30.73 wt.% Fe2O3 and only some amounts of FeO (5.78–13.87 wt%). A strongly altered and radioactively damaged pyrochlore-group mineral occurs as euhedral to subhedral crystals found in the interstices between albite. It is square- and

ACCEPTED MANUSCRIPT rhombus-shaped, 20–150 µm in size (Fig.3D, 6B). Only few of them show a poor oscillatory zoning, very often with irregular lighter and darker patches and numerous microfractures. Some of them possess a characteristic reaction rim (corona) built of needle-shaped crystals of

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Fe-bearing chlorite. The compositions of pyrochlore is provided by Dumańska-Słowik et al.

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(2014), who noted the significant amounts of SiO2 (up to ~13 wt.%) in areas of damaged structure.

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K-feldspar is represented by two generations: (1) euhedral large tabular crystals with a crosshatched pattern, typical of low microcline (Fig.4B), and (2) anhedral and smaller forms characteristic of orthoclase. In microcline (Or97-95) the calculated degree of Al–Si order is ∆ ˃

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0.96. The vast majority of its crystals show characteristic banded, infiltration perthitic intergrowths from crystallization of albite (Fig.4I-J). Orthoclase is relatively fresh without any

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traces of perthitization. Generally, K-feldspars show blue CL colours (Fig.4A,E,I), whereas the altered crystals luminescence in brown.

Sodalite usually forms subhedral to anhedral crystals coexisting with nepheline and

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albite (Fig.4G-H). The reaction zones between sodalite and nepheline are observed locally.

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Sodalite hosts a majority of solid inclusions with K-feldspar and natrolite as the dominant phases, whereas annite, zircon, aegirine and fluorbrytholite-(Ce) belong to subordinate phases. Under a luminoscope, sodalite shows patchy dark blue CL colours (Fig.4G). It shows

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rather simple composition with Na+ as a dominant cation (6.92–8.49 pfu) and Cl– as dominant extra-framework anion ranging from 1.91 to 2.05 pfu (Dumańska-Słowik et al., 2015c). Natrolite locally forms prismatic crystals, but it sometimes forms radiating fibrous

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aggregates (Fig.3F). In mariupolite, it occurs in reaction zone between sodalite and nepheline or in veins filling the seams (Dumańska-Słowik et al., 2015c). Cancrinite forms irregular aggregates and thin veins, locally accompanied by calcite and sodalite occurring in near vicinity of nepheline and feldspars. More commonly it fills cracks within large crystals of nepheline. Cancrinite hosts a wealth of various mineral inclusions: K-feldspars, sodalite, albite, annite, a pyrochlore-group mineral, monazite-(Ce), parasite-(Ce) and sphalerite. Under a luminoscope, it shows dark red-brown CL colour with patchy zoning (Fig.4E-F). The detailed composition of cancrinite is presented by DumańskaSłowik et al. (2016), who noted that though CO32- is a prevailing anion, it reaches from 0.45 to 0.92 pfu, whereas S, F and Cl appear in traces. Fluorapatite forms anhedral crystals from 0.1 up to 3 mm in size (Fig.4A-B). It shows patchy zoning (Fig.6C) in light pink-brown CL colours with no signs of magmatic, oscillatory zoning (Dumańska-Słowik et al., 2012). The pink brown CL colours are attributed

ACCEPTED MANUSCRIPT to REE (Ce3+, Dy3+ Sm3+ and Nd3+) in its structure (Dumańska-Słowik et al., 2015b). Fluorapatite is nearly devoid of any solid inclusions, apart from single crystals of parasite(Ce), Th–U–Fe oxides as well as monazite-(Ce) and fluorite. The detailed chemical

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composition of fluorapatite is given in Dumańska-Słowik et al. (2012), who noticed the

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significantly enrichment in REE (10.5–19.5 wt.% REE2O3) in this phosphate. Fluorbritholite-(Ce) occurs as anhedral crystal up to 0.7 mm in size and also exhibits

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patchy zoning under BSE (Fig.6D). It contains rare solid inclusions, mainly fluorapatite and natrolite. Locally fluorbritholite-Ce occurs in close spatial association with fluorapatite, monazite-(Ce) and fluorite. The detailed chemistry of this phase was presented by Dumańska-

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Słowik et al. (2012), who noted in it really high amounts of REE2O3 (53.60–60.19 wt.%), mainly Ce, La and Nd.

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Monazite-(Ce) forms anhedral crystals from 50 µm to 200 µm in size. Together with fluorite it forms fine-grained symplectitic aggregates found between the boundaries of coexisting fluorapatite and fluorbritholite-(Ce) (Fig.4D). In monazite-(Ce), based on the plot

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of (REE +P) vs (Th+Si), the huttonite substitution distinctly dominates over the cheralitic

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component (Dumańska-Słowik et al., 2012). Fluorite forms anhedral crystal up to 150 µm in size. It fills the interstices between

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albite crystals or occurs in close paragenesis with the phosphates i.e. monacite-(Ce), fluorapatite, fluorbritholite-(Ce) and carbonates (Dumańska-Słowik et al., 2012). Under CL, it shows REE-activated light blue colour (Fig.4C). In its CL spectrum, there are two distinct bands at 343 nm and 680 nm (Fig.7), which correspond to Ce3+ and Dy3+, respectively (Götze,

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2000; Sikorska, 2005).

Calcite forms anhedral crystals forming irregular aggregates between albite crystals (Fig.4K-L) or thin veinlets filling fractures within cancrinite. It shows orange-yellow CL (Dumańska-Słowik et al., 2015b). Other components such as magnetite, hematite, sphalerite and REE-bearing carbonates [parasite-(Ce) and bastnäsite-(Ce)] occur only in traces or as single inclusions within the major or minor components of mariupolites.

5.3 Bulk composition of the rock The bulk-rock composition of mariupolite suggests that the melt from which magmatic components of the rock crystallized was a silica-undersaturated (56–60 wt.% SiO2 with 17–19 wt.% of nepheline following CIPW norm), enriched in Na (8.50–12 wt.% Na2O) and depleted in Ca (3.96–0.37 wt.% CaO). On the basis of the chemical composition (Tab. 1), mariupolite

ACCEPTED MANUSCRIPT of the Oktiabrski Massif can be characterized as miaskitic rock because of the agpaicity index of the rock, i.e (Na+K)/Al is 0.95–1.14, and Na+K > 1/6 Si (Streckeisen and Hunziker, 1974; Sørensen, 1974; 1997). The contents of incompatible elements of mariupolite normalized to

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mid-ocean basalts (MORB: Gale et al., 2013) are presented in Fig.8. Mariupolite is

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fractionated as indicated by depletion in Ba, Eu, P, REE and Ti, and enrichment in K, Rb, Th, Nb and Zr. The average Nb and Zr contents in mariupolites are 0.062 and 0.181 wt.%.,

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respectively (Tab.1). However some types of mariupolites enriched in pyrochlore-group minerals and zircon show higher abundances of these elements, up to 0.379 wt.% of Zr and 0.134 wt.% of Nb (Krivdik et al. 2010). The overall pattern of this rock is generally similar to

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the pattern of nepheline syenites from the McGerringle complex of Quebeck (Wallace et al., 1990), except for REE which are slightly lower in mariupolite. However, among rare earth

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elements the group of LREE (231–358 ppm) predominates over HREE +Y (25–105 ppm) (Table 1). Chondrite normalized REE pattern of mariupolite is very similar to other metasomatic rocks (Al Ani and Sarapää, 2013; Dumańska-Słowik et al., 2015b). It is

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characterized by a negative slope for the LREE and plateaus for the HREE with a negative Eu

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anomaly (Fig.9), which resulted probably from the removal of Eu together with Ca from the host rocks during fluid mediated metasomatic activity. The REE distribution for the whole-

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rock sample is controlled mainly by monazite-(Ce), fluorapatite, fluorbritholite-(Ce) and REE-bearing carbonates. Therefore, it seems that REE mobilization occurred during both

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magmatic and post-magmatic, hydrothermal processes.

6. Discussion Mariupolites of the Oktiabrski Massif form intrusive bodies of ultramafic and mafic rocks (pyroxenite, peridotite, gabbro) or smaller veins within foyaites. They fill cracks and dislocation zones between crystallized earlier intrusive rocks, occurring with varying texture types, especially oriented, trachytoid and porphyritic. All the texture varieties suggest the intrusive, hypabyssal origin of these rocks, originated at medium to shallow depths within the crust at moderate pressure and temperature conditions. Occasionally, equigranular, coarsegrained and porphyritic texture, without any transitional zone between them, are observed not only in the same deposit, but even in the same sample. Then, it is assumed, that physicochemical conditions of melt crystallization were being changed along with the temperature and pressure decrease. As a consequence, the contents of silica, alumina and alkalis in the

ACCEPTED MANUSCRIPT parental, alkaline melt differentiated to some extent. It is well reflected in the local crystallization of nearly albite only in one place, or albite with nepheline and aegirine in others (Fig.3E,H).

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Textural features show significant subsolidus re-equilibration of mariupolite from the

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Oktiabrski Massif. Thus, the whole mineral composition can be divided into two groups : (1) magmatic, and (2) postmagmatic (subsolidus and hydrothermal). The mineralogy of magmatic

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assemblage is dominated by euhedral aegirine, zircon, annite, euhedral to subhedral nepheline and euhedral albite. K-feldspar, a pyrochlore-group mineral, fluorapatite, fluorbritholite-(Ce) and magnetite appear as subordinate or accessory phases. Whereas, the

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subsolidus and hydrothermal assemblage includes monazite-(Ce), fluorite, calcite, sodalite, natrolite, cancrinite, sphalerite and hematite. Such mineral paragenesis is characteristic of

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classic alkaline massifs (Sørensen, 1974).

Within magmatic phases two generations of minerals can be distinguished: (1) early, and (2) of a late stage of melt differentiation (Fig.10). At a relatively high range of

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temperature, crystallization of the megacrysts of euhedral zircon, aegirine, annite and

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magnetite occurred. Zircon exhibits very complicated texture, i.e. yellow CL center attributed to Yb2+, with patchy zoning and numerous pores as well as navy blue CL rim connected with

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Dy3+ activation, with oscillatory zoning, which resulted in significant differences in CL spectra recorded for both regions. Such characteristics indicate that domains with yellow CL definitively differ in origin from the areas with navy blue CL. Hence, it seems that the core of zircon is distinctly older than its rim and the mineral crystallized for a long time under

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variable temperature and pressure conditions and the compositions of melt surely had changed during that time (Dumańska-Słowik et al., 2011b). Two main mariupolite components, albite and nepheline, crystallized at a later stage, with the temperature decreasing to 732 °C, i.e. an eutectic point in the system Na2O–Al2O3–SiO2 (Schairer and Bowen, 1956). The nepheline composition plotted on the nepheline–kalsilite–silica diagram (Fig.5) used as a geothermometer (Platt, 1996; Fall, 2005) indicates that the nepheline formed from 900 °C to ca. 600 °C. A similar temperature range was obtained by Blancher et al. (2010) for nepheline syenites from Namibia. However, this temperature range does not represent magmatic crystallization of nepheline, but rather a prolonged re-equilibration of mariupolite at relatively high temperatures (Worley and Cooper, 1995), consistent with textural observations of the host rock, e.g. coronas and infiltration perthite textures. K-feldspar, a pyrochlore-group mineral, fluorapatite and fluorbritholite-(Ce) crystallized in the last stage of the magma

ACCEPTED MANUSCRIPT differentiation. During the crystallization of magmatic phases, melt was oversaturated in Zr, Fe, Nb, Na and K. Among magmatic phases, aegirine is almost the only component of mariupolite, which

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is relatively fresh and does not show any traces of alteration. Most probably it crystallized

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after formation of zircon from residual alkali melt. The composition of the pyroxene, significantly enriched in Fe3+ and depleted in Fe2+, additionally associated with disseminated

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magnetite, could suggest a relatively high oxygen fugacity, ƒO2, during the alkaline melt crystallization (Worley and Cooper, 1995). On the other hand, the presence of relatively well ordered feldspars (low albite and low microcline) could suggest a slow cooling rate.

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At the last stage of mariupolite consolidation and in post-magmatic processes, the rocks have been strongly affected by the released of a high-temperature magmatic fluid.

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Based on the diagram of cancrinite stability in the T–XCO2 space of Sirbescu and Jenkins (1999), it was deduced that primary nepheline has been altered into cancrinite under action of these fluids at temperatures below 930 oC (Dumańska-Słowik et al., 2016). As a result some

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minerals, such as sodalite, monazite-(Ce), calcite, fluorite, and hematite are products of

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metasomatic alteration under action of these fluids. Two main types of metasomatic alteration induced by the fluids can be distinguished: (1) Ca-rich phases (calcite, cancrinite, fluorite),

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and (2) Na-rich phases (sodalite, natrolite). Other mariupolite components like fluorapatite, fluorbritholite-(Ce), zircon and the pyrochlore-group mineral were also under intense action of the fluid.

The release of a high-temperature magmatic fluid enriched in H2O, CO32–,PO43-, Cl–,

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and F- around 930 oC gave rise to metasomatic alteration of the primary, magmatic components of mariupolite, mainly nepheline and albite, into cancrinite with subordinate calcite, followed by crystallization of fluorite and monazite-(Ce) and the formation of small inclusions of secondary parisite-(Ce) and bastnäsite-(Ce) within the phosphates i.e fluorapatite and fluorbritholite-(Ce), as well as alteration of the pyrochlore-group mineral into a “silicified” variety (up to 13.0 wt.% SiO2). Cancrinite in this paragenesis is the dominant phase. Its common textures, i.e. (1) the occurrence within the cracks and at the rim of fractured crystals of nepheline, (2) rounded contacts of cancrinite with nepheline, (3) irregular patchy CL zoning without any regular growth zones and (4) distinct paragenesis with sodalite, natrolite, K-feldspars and calcite; all suggest that cancrinite was formed by alteration of nepheline via the fluid in the sub-solidus conditions. The possible mechanism is probably the same as described by Fall (2005) that a complex carbonate-rich fluid (a mixture

ACCEPTED MANUSCRIPT of chloride, carbonate and sulphate complexes of calcium) reacted with nepheline to produce cancrinite:

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6(NaK)AlSiO4 + 2Ca(Cl2, CO3, SO4) + nH2O = Na6Ca2Al6Si6O24(Cl2, CO3, SO4)2·nH2O

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(in the case of cancrinite from mariupolite SO42– is almost absent), or as a reaction of

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nepheline with calcite crystallized directly from the fluids (Sirbescu and Jenkins, 1999): 6(NaK)AlSiO4 + 2CaCO3 + nH2O = Na6Ca2Al6Si6O24(CO3)2·nH2O.

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However, in the case of the second possible reaction, calcite should have crystallized before cancrinite and should have been consumed almost completely during formation of the mineral. In fact, the present form of mariupolite really contains very small amounts of calcite,

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forming thin veinlets within cancrinite or aggregates filling interstices between albite crystals. The first form of calcite could be relicts of nepheline‟s cancrinitization, but where the latter

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crystallized directly from the fluids, but only in places where there was no nepheline nearby. It is also very probable that during that stage of the mariupolite evolution the primary

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fluorapatite and fluorbritholite-(Ce) were partially dissolved and patchy-replaced by the same phases with new compositions and by secondary phosphate-, REE-bearing host, monazite-

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(Ce) and fluorite as results of fluid-aided dissolution-reprecipitation processes. Generally fluorapatite with extremely high REE2O3 contents (up to ~ 19.wt.%) and slightly enriched in Na2O (up to 2.52 wt.% Na2O), is interpreted as a primary igneous phase, was altered via

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coupled substitutions:

REE3+ + Si4+ = Ca2+ + P5+ and Na+ + REE3+ = 2Ca2+ to REE- and Na-depleted (12.46 wt.% REE2O3, 1.79 wt.% Na2O), but Ca-enriched species (Dumańska-Słowik et., 2012). The final form of fluorapatite is considered of secondary origin, since there was no line at 560–570 nm attributed to Mn2+ in its CL spectrum, which is characteristic of magmatic apatites (vide Dumańska-Słowik et al., 2015b). Similarly at this stage, REE- and Si- enriched fluorbritholite-(Ce) was altered to REE- and Si-depleted, but Caenriched species. The REE3+ and PO43- ions mobilized from the contacting of fluorbritholite(Ce) with fluorapatite in the presence of a F-rich fluid in an alkali-rich system promoted the formation of monazite-(Ce) as the new phosphate, REE-host in mariupolite. The presence of monazite-(Ce) with relatively low Th content (on average 0.91 wt.% Th2O) suggests low temperature conditions, typical of hydrothermal processes (Kempe et al., 2008). At similar

ACCEPTED MANUSCRIPT temperature conditions fluorite as well as REE-bearing carbonates i.e. parisite-(Ce) and bastnäsite-(Ce) crystallized (Dumańska-Słowik et al., 2012). This stage of metasomatic alteration affected also the older generation of zircon (the

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crystal cores), in which primary (Th,REE)-rich species was replaced by a variety almost

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devoid of Th and REE (Dumańska-Słowik et al., 2011b). The patchy-zoning texture in defect-

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rich, central domains of zircon was attributed to disequilibrium, dissolution-recrystallization process that could occur in a high-temperature environment i.e. > 700 °C (Gagnevin et al., 2009 vide Dumańska-Słowik et al., 2011b). Moreover, a primary F-bearing pyrochlore of the

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late-magmatic to early-hydrothermal origin, underwent an intensive primary to transitional alteration (Lumpkin and Ewing 1995) in outer zones of its crystals, induced by a hightemperature, Ca2+- and Si4+-rich fluid with increasing pH. The process formed irregular, Si-

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enriched patches and secondary zoning (cores devoid of Si / rims enriched in Si), with the Asite cation totals in the rims elevated in relation to the crystal cores. Si-bearing pyrochlore of the rim is additionally enriched in Ca2+, REE3+, and also Mn2+, Sr2+, K+, U4+ and Th4+,

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provided by the fluid enriched in these elements by interaction with mineral components of

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the host mariupolite (Dumańska-Słowik et al., 2014). The local crystallization of cancrinite at the expense of calcite components dissolved

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by the fluids and precipitation of other Ca-bearing phases have led finally to metasomatism of mariupolite under action of Ca- and CO32–-poor fluids, enriched mainly in dissolved NaCl. During this type of metasomatism, sodalite occurs as a replacement phase after nepheline and

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albite, whereas natrolite forms as a by-product of this transformation in subsolidus or crystallizes directly from the fluids (Dumańska-Słowik et al., 2015). Close spatial paragenesis of sodalite with albite, nepheline, natrolite and K-feldspar, the embayed contacts of sodalite with nepheline and albite, the patchy appearance of sodalite under CL as well as the presence of a 680–690 nm band in CL spectrum of sodalite, assigned to Fe3+, which could originally be from fenitized albite, all suggesting the formation of sodalite as a result of conversion of nepheline or at the expense of albite (Dumańska-Słowik et al., 2015c) by the reactions: 6NaAlSiO4+ 2 NaCl = Na8Al6Si6O24Cl2 or 6Na[AlSi3O8] + 2 NaCl = Na8[Al6Si6O24]Cl2 +12 SiO2 (aq) immobilized in natrolite

ACCEPTED MANUSCRIPT The transformation of nepheline into sodalite, according to the first reaction is associated with the release of K+, which could be distributed between weakly triclinized K-feldspar and altered annite of the second generation. In the second possible process, i.e. sodalitization of

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albite, some amounts of SiO2 are released into the fluids. This silica could be consumed by

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the formation of secondary Na-aluminosilicates, e.g. natrolite as a by-product, however, a critical role in the crystallization of such a phase should explain the relationship of Al3+ vs

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Si4+ activity in the fluids (Dumańska-Słowik et al., 2015c). Undoubtedly, SiO2 released in the reaction could also be incorporated into damaged parts of the pyrochlore structure (Dumańska-Słowik et al., 2014). Sodalite could also form directly by alteration of albite by a

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hydrothermal fluid enriched in Na+ and Al3+, but undersaturated with SiO2, according to the reaction:

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2 NaAlSi3O8 + 6 Na+ + 2 Cl– + 4 Al3+ + 16 OH– = Na8Al6Si6O24Cl2 + 8 H2O In mariupolite the metasomatism resulted also in developing the perthite textures

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(infiltration perthites) and albitization of K-feldspars. Alterations of this stage affected surely

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not only mariupolites but also other rocks of the Oktiabrski massif and are closely associated with fenitization processes (Dumańska-Słowik et al., 2015b). As a result the metasomatized

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(i.e. fenitized) albite shows typical bright red cathodoluminescence properties. Similarly, the local replacement of magnetite by hematite at increasing ƒO2 should have occurred also that time.

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Summarizing, during the alteration in subsolidus and along with temperature decreasing, CO32–-activity decreased, whereas alkalinity and O2 fugacity of the fluids that finally attained values of the magnetite/hematite reaction, increased (Dumańska-Słowik et al., 2016). In this process, among the magmatic assemblages only aegirine, was stable. Some amounts of nepheline was replaced by cancrinite and sodalite, albite was fenitized and replaced by sodalite, magnetite was altered to hematite, fluorapatite and fluorbritholite-(Ce) were partially dissolved and re-precipitated or partially replaced by secondary monazite-(Ce) and fluorite. The fluid-mediated coupled dissolution-reprecipitation process affected also the primary zircon and pyrochlore, which underwent alteration and metamictization entering silica in the form of Q2 structure of bridging silicon tetrahedra in the severely damaged portions of its structure (Dumańska-Słowik et al., 2014). The proposed model of nepheline alteration into cancrinite and sodalite suggests the mariupolite melt achieved volatile saturation very soon after its crystallization was initiated.

ACCEPTED MANUSCRIPT Hence, a magmatic fluid-activated system could exist during the crystallization history of nepheline syenite of the Oktiabrski Massif, similarly to nepheline syenites of the Ditrău Alkaline Massif studied by Fall et al. (2007). Such interpretation is also consistent with

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fractionation residua origin for the nepheline syenite melt (Morogan et al., 2000; Pál-Molnár,

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2000).

Mariupolites from the south-eastern Ukraine at the Azov sea, characterized by the

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presence of zircon, pyrochlore, fluorapatite, fluorbritholite-(Ce), fluorite, monazite-(Ce), parisite-(Ce), bastnäsite-(Ce) are recognized as a potential source of incompatible and volatile elements such as Zr, Nb and REE (Tab.2). These elements have been classified by the

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European Union as critical resources of strategic importance for the development of modern advanced technologies such as electronics, medicine, ceramics and nuclear power industry

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(e.g. Sørensen, 1992; Linnen et al., 2012, Goodenough et al., 2016 ). They are essential for all kinds of useful things in our everyday lives (Chakhmouradian and Wall, 2012). Since their global supply is restricted to several mining provinces in China (REE), Brazil (Nb), Rwanda

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(Ta), Australia (Nb, Zr), the search for the new resources of these materials are still on-going

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to provide the security for the development of high technologies (e.g. Encinas-Ferrer et al., 2014). Mariupolite with Nb–Zr–REE–F mineralization may have good potential to become a

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product of economic importance. In the 20th century, just after the world war II, Zr was recovered from the alkaline rocks of this massif for zircon concentrate used by metallurgical and chemical factory of Mariupol city. However, in the present time this region is difficult to access due to political conflict. Anyway, it seems that mariupolites from the Oktiabrski

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Massif may have good economic potential for Nb, Zr and REE deposit(s), but further research and exploration is needed. The review and documentation of numerous peralkaline and alkaline complexes, hosting metalogenetic deposits, found within Ukrainian Shield, seems to be important since Ukraine is a candidate country to enter the European Union. .

7. Conclusions 1.

The nepheline syenites (mariupolites) in the alkaline Oktiabrski Massif, may host

economic Zr, Nb, REE mineralization, proceeded at extremely complicated physicochemical conditions and with intensive tectonic activity. Some portion of a melt of the nepheline syenite‟s composition was dynamically displaced to upper part of the earth crust in the dislocation zones. Two generations of mineral components were distinguish in the primary composition of the host rock: (1) early, composed of zircon, aegirine and annite,

ACCEPTED MANUSCRIPT and (2) late stage of melt differentiation made of albite, nepheline and subordinate Kfeldspar, pyrochlore, fluorapatite, fluorbritholite-(Ce). 2.

Mariupolite, probably still during or directly after consolidation at temperature below

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of 930 oC, became very quickly saturated in juvenile alkali-carbonate-chloride fluids and

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intensive matasomatic activity took place in this region. As a result the majority of magmatic components of the rock were strongly altered into a diversified assemblage of

3.

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secondary phases.

The high temperature alkaline-carbonate fluids most probably originated in the deep

parts of the alkaline Oktiabrski massif. The intense tectonic activity may have been

4.

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responsible for the delivery of juvenile fluids to the intruding mariupolite-like melt. The alteration of the primary mariupolite components and crystallization new phases

in subsolidus conditions proceeded at least in two stages: (1) earlier, due to the action of

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fluids being primarily enriched in Ca2+, Na+, CO32–, Si4+, Cl– with some amounts of F– and REE, and (2) pervasive Na+- and Cl–-rich hydrous event. As a result cancrinite was formed

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after the primary nepheline, calcite, monazite-(Ce), fluorite, REE- bearing carbonates

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[parasite-(Ce), bastnäsite-(Ce)]. The primary fluorapatite and fluorbritholite-(Ce) were partially replaced by the same phases with new compositions and by secondary monazite-

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(Ce) and fluorite. The fluorpyrochlore was altered into a Ca-, REE- and Si-enriched pyrochlore. (Th, REE)-rich zircon was partly-replaced by a variety almost devoid of Th and REE. Furthermore, CO32–-depleted, but still Na+- and Cl–-rich fluids induced sodalitization of some parts of nepheline and albite with the formation of secondary natrolite, second

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generation of K-feldspar and annite as by-products of the sodalitization process. At last, but not least, K-feldspars have been undergone widespread albitization. 5.

Mariupolite types with abundant Nb–Zr–REE mineralization has the potential to be of

economic interest in the future. Leucocratic varieties of these rocks can be also used in the glass industry and special ceramics, whereas pegmatite types with sodalite could be applied in building industry and jewellery.

Acknowledgements My Masters, Professors Wiesław Heflik and Adam Pieczka are gratefully acknowledged for the long-time discussions and comments on the manuscript. I am also very grateful to Magdalena Sikorska, who made CL analyses. Lucyna Natkaniec-Nowak and Sergey Shevchenko are gratefully acknowledged for their assistance in looking through Ukrainian and Russian papers on geology of the Oktiabrski Massif. The manuscript benefitted much

ACCEPTED MANUSCRIPT from constructive comments and suggestions of Franco Pirajno and an anonymous reviewer. This work was financially supported by the AGH University of Science and Technology

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(Krakow, Poland), research project No 11.11.140.319.

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References

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Al Ani, T., Sarapää, O., 2013. Geochemistry and mineral phases of REE in Jammi carbonatite veins and fenites, southern end of the Sokli complex, NE Finland. Geochem.: Explor., Environ., Anal. 13, 217–224.

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Anders, E., Grevesse, N., 1989. Abundances of the elements: Meteoritic and solar. Geochim. Cosmochim. Acta, 53, 197–214.

Blancher, S.B., Arco, P.D., Fonteilles, M., Pascal, M.L., 2010. Evolution of nepheline from

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mafic to highly differentiated members of the alkaline series: the Messum complex, Namibia. Mineral. Mag. 74(3), 415-432.

Coulson, I.M., 2003. Evolution of the North Qôroq centre nepheline syenites, South

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Greenland: alkali-mafic silicates and the role of metasomatism. Mineral. Mag. 67(5),

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873-892.

Chakhmouradian, A.R., Wall, F., 2012. Rare earth elements: minerals, mines, magnets (and

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more). Elements, 8(5), 333-340. Donskoy, A.N., 1982. The nepheline complex of alkaline Oktyabrski massif. The

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Ukrainian Academy of Science, Kiev (in Ukrainian). 1. Dumańska-Słowik, M., Baranov,. P., Heflik, W., Natkaniec-Nowak, L., Schevkenko, S., Tsotsko, L.I. 2011a: Mariupolite from the Oktiabrski Massif (SE Ukraine) a less known rock in the gemstone trade. Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 60(1-2) 37-48. Dumańska-Słowik, M., Sikorska, M., Heflik, W., 2011b. Dissolved-recrystallized zircon from mariupolite in the Mariupol Massif, Priazovje (SE Ukraine). Acta Geol. Polon. 61(3), 277-288. Dumańska-Słowik, M., Budzyń, B., Heflik, W., Sikorska, M., 2012. Stability relationships of REE-bearing phosphates in an alkali-rich system (nepheline syenite from the Mariupol Massif, SE Ukraine). Acta Geol. Polon. 62(2), 247-265.

ACCEPTED MANUSCRIPT Dumańska-Słowik, M., Pieczka, A., Tempesta, G, Olejniczak, Z., Heflik, W., 2014. „Silicified‟ pyrochlore from nepheline syenite (mariupolite) of the Mariupol Massif, SE Ukraine: A new insight into the role of silicon in the pyrochlore structure. Am.

T

Mineral., 99, 2008-2018.

IP

Dumańska-Słowik, M., Wesełucha-Birczynska, A., Pieczka, A., 2015a. Micas from mariupolite of the Oktiabrski massif (SE Ukraine): An insight into the host rock

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evolution - Geochemical data supported by Raman microspectroscopy. Spectrochim. Acta, Part A, 137, 817-826.

Dumańska-Słowik, M., Heflik, W., Kromska, A., Sikorska, M., 2015b Sodic fenites of the

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Oktiabrski complex exposed in the Khlibodarivka quarry (East Azov, SE Ukraine): reconstruction of their growth history. N. Jb. Geol. Paläont. Abh. 275/3, 269-283.

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Dumańska-Słowik, M., Heflik, W., Pieczka, A., Sikorska, M., Dąbrowa, Ł., 2015c. The transformation of nepheline and albite into sodalite in pegmatitic mariupolite of the Oktiabrski Massif (SE Ukraine). Spectrochim. Acta, Part A, 150, 837- 845.

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Dumańska-Słowik, M., Pieczka, A., Heflik, W., Sikorska, M., 2016. Cancrinite from

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mariupolite of the Oktiabrski Massif, SE Ukraine, and its growth history. Spectrochim. Acta, Part A, 157, 211-219.

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Encinas-Ferrer, C., Valderrey-Villar, F.J., Hernandez-Rodriguez, C., Uson-Sardaña, A., 2014. The World Production and Trade of Rare Earth Elements: The Position of the Pacific Area. Chin. Bus. Rev., 13(4), 209-220 Fall, A., 2005. Fluid evolution in the nepheline syenites of the Ditrău Alkaline Massif.

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www.researchgate.net/publication/242286685_Fluid_evolution_in_the_nepheline_ synites_of_the_Ditru_Alkaline_Massif_Transylvania_Romania. Fall, A., Bodnar, R.J., Szabó, C., Pál-Molnár, E., 2007. Fluid evolution in the nepheline syenites of the Ditrău Alkaline Massif, Transylvania, Romania. Lithos 95, 331-345. Gale, A., Dalton, C.A., Langmuir, C.H., Su, Y, Schiling, J.-G., 2013. The mean composition of ocean ridge basalts. Geochem., Geophys. and Geosyst., 14(3), 489-518. Goodenough, K.M., Schilling, J., Jonsson, E., Kalvig, P., Charles, N., Tuduri, J., Deady, E.A., Sadeghi, M., Schiellerup, H., Müller, A., Bertrand, G., Arvanitidis, N., Eliopoulos, D.G., Shaw, R.A., Thrane, K., Keulen, N., 2016. Europe's rare earth element resource potential: An overview of

REE metallogenetic provinces and their geodynamic setting. Ore Geol.

Rev., http://dx.doi.org/10.1016/j.oregeorev.2015.09.019 Götze, J., 2000. Cathodoluminescence microscopy and spectroscopy in applied mineralogy. Technische Universität Bergakademie, Freiberg.

ACCEPTED MANUSCRIPT Hamilton, D.L., 1961. Nephelines as crystallization temperature indicators. J. Geol., 69, 321329. Kempe, U., Lehmann, B., Wolf, D., Rodionov, N., Bombach, K., Schwengfelder, U.,

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Dietrich, A., 2008. U-Pb SHRIMP geochronology of Th-poor, hydrothermal monazite:

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An example from the Llallagua tin-porphyry deposit, Bolivia. Geochim. Cosmochim. Acta, 72, 4352–4366.

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Krivdik, S.G., Tkachuk, V.I., 1998. Geochemical and petrological characterization of the rocks from the alkaline Oktyabr‟skii Massif (Ukraina). Geochimija, 4, 362-371 (in Russian).

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Krivdik, S.G., 2005. Alkaline magmatism in the Ukrainian Shield. Mineral. J. 27(3), 41-49 (in Ukrainian)

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Krivdik, S.G., Nivin, V.A., Kul‟chitskaya, A.A., Voznak, D.K., Kalinichenko, A.M., Zagnitko, V.N., Dubyna, A.V., 2007. Hydrocarbons and other volatile components in alkaline rocks from the Ukrainian Shield and Kola Penisula. Geochem. Int., 45(3),

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270-294.

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Krivdik, S.G., Shumlyanskyy L., Strekozov, S., 2010. Field trip guide. Oktyabrski Massif. Proceedings. Alkaline Rocks: petrology, mineralogy and geochemistry. Conference

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dedicated to the memory of J. A. Morozewicz, 19-21 September 2010, Kiev, 80-93. http://www.ptmin.pl/alkalinerocks/field.html Korobeinikov, A.N., Laajoki K., Gehör S., 2000. Nepheline-bearing alkali feldspar syenite (pulaskite) in the Khibina pluton, Kola Penisula, NW Russia: petrological

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investigation. J. Asian Earth Sci. 18, 205-212. Kynicky, J., Smith, M.P., Xu Ch., 2012. Diversity of rare earth deposits: the key example of China. Elements, 8, 361-367. Linnen, R.L., Van Lichtervelde, M., Černy, P., 2012. Granitic pegmatites as source of strategic metals. Elements, 8(4), 275-280. Lumpkin, G.R., Ewing, R.C., 1995. Geochemical alteration of pyrochlore group minerals: Pyrochlore subgroup. Am. Mineral., 80, 732–743. Morogan, V., Upton, B.G.J., Fitton, J.G., 2000. The petrology of the Ditrău alkaline complex, Eastern Carpathians. Mineral. Petrol. 69, 227-265. Morozewicz, J., 1902. Über Mariupolit, ein extremes Glied der Elaeolithsyenite. Tschermaks Mineral. Petrogr. Mitt. 21, 238-246 (in German). Morozewicz, J., 1929. Mariupolite and its relatives. Polish Geological Institute 2(3), (in Polish).

ACCEPTED MANUSCRIPT Pál-Molnár, E., 2000. Hornblendites and diorites of the Ditró szenite massif. The Dep. of Mineral., Geochem. And Petrol., Univ. of Szeged, Hungary.

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Pirajno, F., 2015. Intracontinental anorogenic alkaline magmatism and carbonatites associated mineral systems and the mantle plume connection. Gondwana Research 27, 11811216. Platt, R.G., 1996. Nepheline syenite complexes – an overview. In: Mitchell, R.H. (ed),

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Undersaturated Alkaline Rocks: Mineralogy, Petrogenesis, and Economic Potential. Mineral. Assoc.. Can. Short Course, 24, 63-99.

Ponomarenko, A.N., Krivdik, S.G., Grinchenko, A.V. 2013. Alkaline rocks of the Ukrainian

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Shield: some mineralogical, petrological and geochemical features. Mineralogia, 44, 34: 115-124.

Schairer, J.F., Bowen, N.L., 1956. The system Na2O-Al2O3-SiO2. Am. J. Sci. 254, 129-195.

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Sharygin, V., Krivdik, S., Pospelova, L., Dubina, A., 2009. Zn-kupletskite and hendricksite in agpaitic phonolites of Oktriabski Massif, Azov region, Ukraine. Dokl. Earth Sci.,

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425(3), 499-504.

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Schilling, J., Marks, M., Wenzel, T., Vennemann, T.,Horvatht, L., Tarassoff, P., Jacob D.E., Markl G.2011. The Magmatic to Hydrothermal Evolution of theIntrusiveMontSaint-

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HilaireComplex: Insights into the Late-stage Evolution of Peralkaline Rocks. Journal of Petrology, 52(11), 2147-2185. Schönenberger, J., Marks M., Wagner, T., Markl G., 2006. Fluid-rock interaction in autholits

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of agpaitic nepheline syenites in the Ilimaussaq untrusion, South Greenland. Lithos, 91, 331-351.

Sikorska, M. Cathodoluminescence analyses of minerals. Instr. Met. Bad.Geol., 59. Polish Geological Institute (in Polish). Sirbescu, M., Jenkins, D.M., 1999. Experiments on the stability of cancrinite in the system Na2O-CaO-Al2O3-SiO2-CO2-H2O. Am. Mineral. 84, 1850-1860. Solodov, N.A., 1985. The mineralo-genesis of rare metal formations. Niedra (in Ukrainian). Sørensen, H., (Ed), 1974. The alkaline rocks. J.Wiley & Sona, London. Sørensen, H., 1992. Agpaitic neheline syenites: a potential source of rare elements. Appl. Geochem., 7, 417-427. Sørensen, H., 1997. The agpaitic rocks – an overview. Mineral. Mag., 61, 485-498. Streckeisen, A., Hunziker, J.C., 1974. On the origin and age of the nepheline –syenite complex of Ditró (Transsylvania, Rumunia). Schweiz Min. Petr. Mitt. 54, 1, 59-77.

ACCEPTED MANUSCRIPT Sviridov, V.V., 1973. Statistical investigations of chemistry within alkaline Oktiabrski Massif. Iz. Vuz., Geologiia i Razvedka 5, 60-66. Tichonienkova, R.J, Osokin, J.D., Gonzjejev, A.A., 1967. Rare-metals metasomatites of

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alkaline massives. Nauka, (in Ukrainian).

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Tilley, C.E., 1954. Nepheline-alkali feldspar paragenesis. Am. J. Sci. 252, 65-75. Volkova, T.P., 2000. The genesis and ore mineralization of alkaline rocks from the

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Oktyabr‟skii Massif. Sb. Nauchn. Tr., 4, 9-10 (in Ukrainian).

Volkova, T.P. 2001. The productivity criterion of REE and ore mineralization within rocks of the Oktyabr‟skii Massif Naukovi praci DonDTU. 36, 63-69 (in Ukrainian).

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Wallace, G.M., Whalen, J.B., Martin, R.F., 1990 Agpaitic and miaskitic nepheline syenites of the McGerringle Plutonic Complex, Gaspé, Quebec:an unusal petrological association.

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Can. Mineral., 28, 251-266.

Worley, B.A., Cooper, A.F., 1995. Mineralogy of the Dismal nepheline syenite, southern Victoria Land, Antarctica. Lithos, 35, 109-128.

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Wright, T.L., Stewart, D.B., 1968. X-ray and optical study of alkali feldspar I. Determination

Mineral., 54, 38-87.

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of composition and structural state from refined unit-cell parameters and 2V. Am.

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Yanchenko, V., Os‟machko, L.S., Skobin, V.T., 2010. Mariupolits are synsheared phenomenon. Alkaline Rocks: petrology, mineralogy and geochemistry. Proceedings of conference dedicated to the memory of J.A. Morozewicz, 19-21 September 2010,

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Kiev, 75-76.

Figure captions

Fig.1. Sketch map of the Ukrainian Shield with alkaline rocks occurrences (Ponomarenko et al., 2013). Fig.2. Geological map of the Oktiabrski Massif inUkraine (modified after Dumańska-Słowik et al., 2011). Fig.3. Minerals and textural relations in mariupolites: A-B porphyritix texture; C equigranular texture; D corona texture; E trachytoid texture, F spherulitic texture; G poikilitic texture; H disoriented texture. Symbols: Ab – albite, Aeg – aegirine, Ann – annite, Nph – nepheline, Ntr – natrolite, Plc – pyrochlore, Zr – zircon. Fig.4. Microphotographs of main and accessory components from mariupolite: A,C, E, G, I, K, M – cathodoluminescence; B,D,F, H, J,L, N– polarized light. Symbols: Ab –

ACCEPTED MANUSCRIPT albite, Aeg – aegirine, Ann – annite, Ap – fluorapatite, Brt – fluorbritholite – (Ce), Cal – calcite, Ccn – cancrinite, Fl – fluorite, K-fs – K-feldspar, Mnz – monazite, Nph – nepheline, Ntr – natrolite, Plc – pyrochlore, Sdl – sodalite, Zr – zircon.

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Fig. 5. Nepheline composition of mariupolite plotted in the nepheline-kalsilite-silica diagram.

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Isotherms show the limits of nepheline solid solutions at various temperatures (Hamilton, 1961). M and B are Morozewicz and Buerger ideal nepheline composition

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by Tilley (1954) and Platt (1996).

Fig.6. BSE images of zircon, pyrochlore fluorapatite and fluorbritholite-(Ce). Symbols: Ap – fluorapatite, Brt – fluorbritholite – (Ce), Plc – pyrochlore, Zr – zircon.

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Fig.7. CL spectrum of fluorite.

Fig.8. Incompatible-element-abundance plot normalized to normal mid-ocean-ridge basalt

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(Gale et al., 2013) for mariupolites.

Fig.9. Chondrite-normalized REE patterns for mariupolite. Normalization values from Anders and Grevesse (1989).

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Fig.10. Paragenetic relationships of major and minor rock forming minerals in mariupolites.

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Potential rare metals -bearing minerals are in bold. Table 1. Bulk rock composition of mariupolite..

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Table 2. Mineral composition of mariupolite

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Table 3 Representative EMPA analyses of nepheline from mariupolite.

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Detection Limit

% % % % % % % % % 0.0 0.0 0.0 0.0 0.0 0. 0.0 0. 0.0 1 1 1 01 1 01 1 01 01

Unit Symbol Detection Limit M19*

U pp m

Y pp m

0.1 0.1 20. 1 9.2 12. 1 8.7

2 13 78

La Ce Pr pp pp pp m m m 0. 0.1 0.1 05 41. 11 13 8 7 .5 74. 16 19 3 5 .4

S Nd m pp pp m m 0. 0.1 1 46. 7. 9 2 72. 13 6 .6

C L To Sc r OI tal pp pp m m % % 1. 0.0 0.0 0 20 1 1 2. < 0.4 99. 6 20 6 07 < 98. 4 20 2.2 89

D Eu Gd Tb y pp pp pp pp m m m m 0.0 0. 5 0.1 0.1 1 0.7 3. 2 4 0.6 6 11. 10 1.7 5 1.8 .5

H o pp m 0. 1 0. 7 2

Unit Symbol Detection Limit

Sc pp m 1

M19*

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In pp m

Sn pp m

Sb pp m

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Be pp m 1

V pp m 5

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Th pp m

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M19*

P2 O5 As pp % m 0.0 1 0.5 < 0.0 1 2.5 0.0 < 5 5

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Unit Symbol

Na K2 Ti O O2 2O

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Analyte Symbol

C Si Al2 Fe2 M M a O2 O3 O3 nO gO O

Analyte Symbol Unit Symbol Detection Limit M19*

M50 * data from DumańskaSłowik et al. (2012)

0.2 1 < 0.2 30 0.3 47

Z R Cr Co Ni Cu n Ga Ge As b Sr pp pp pp pp pp pp pp pp pp pp m m m m m m m m m m 20 1 20 10 30 1 1 5 2 2 < < < < 11 20 5 20 10 40 80 3 5 1 35 < < < < 33 14 20 < 1 20 10 90 62 4 5 0 7

Cs Ba Hf pp pp pp m m m 0. 0.5 0.5 3 2 < < 44 0.5 0.5 8 .4 < 17 36 0.5 2 2 .1

Ta W Tl pp pp pp m m m 0.1 1 0.1 34. 1 25 0.4 21. < 9 1 0.3

Pb pp m

Z Bi Ni n pp pp pp m m m

T m pp m 0.0 0.1 5 0.4 2.3 3 0.7 5.4 9 Er pp m

Y b pp m 0. 1 3. 6 5. 9

M Zr Nb o pp pp pp m m m 4 1 2 18 62 < 12 0 2 77 30 < 9 4 2

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L u pp m 0. 04 0. 81 1. 1

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Tab.2. Mineral composition of mariupolite.

idealized formula

aegirine

NaFe[Si2O6]

albite

Na[AlSi3O8]

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name of mineral

nepheline

(Na,K)[AlSiO4] KFe3[AlSi3O10](OH,F)2

K-feldspar barren minerals calcite sodalite

CaF2

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fluorite

CaCO3 Na8Al6Si6O24Cl2 Na2Al2Si3O10 * 2H2O

cancrinite

Na6Ca2Al6Si6O24(CO3)2

zircon

Zr[SiO4]

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natrolite

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K[AlSi3O8]

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annite

pyrochlore

(Ca,Na,REE)(Nb,Ti,Ta)2O6(OH,F)

fluorapatite

(Ca,Ce,Nd,La)5(PO4)3F

fluorbritholite-(Ce)

(Ce,Ca,La,Nd)5(SiO4,PO4)3(F, OH)

monazite-(Ce)

(Ce,La,Nd, Th)PO4

parasite-(Ce), bastnäsite-(Ce)

Ca(Ce, La)2(CO3)3F2 Ce(CO3)F

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1.048 0.946 0.009 0.756 0.190

Ne Ks Qtz

73.21 20.28 6.51

73.45 20.52 6.03

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Si Al Fe Na K

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Nepheline 43.08 32.98 0.44 16.02 6.11 98.63

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Nepheline 43.32 32.75 0.48 15.97 6.04 98.56

SiO2 Al2O3 FeO Na2O K 2O Total

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Table 3. Representative EMPA analyses of nepheline from mariupolite.

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Graphical abstract

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Mariupolite crystallized under hypabyssal conditions. Magmatic and subsolidus components make up the composition of mariupolite. Juvenile alkaline-carbonate-chloride fluids affected the melt very early in its history. Mariupolite is a potential resource of Nb, Zr and REE.

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1. 2. 3. 4.