Relationship of F-Be mineralization to granites and syenites at the Ermakovka deposit (Western Transbaikalia)

DOI: 10.1344/GeologicaActa2020.18.2  G.S. Ripp, I.A. Izbrodin, M.O. Rampilov, A.A. Tomilenko, E.A. Lastochkin, V.F. Posokhov, 2020, CC BY-SA G . S . R i p p e t a l . G e o l o g i c a A c t a , 1 8 . 2 , 1 1 3 , I V I ( 2 0 2 0 ) D O I : 1 0 . 1 3 4 4 / G e o l o g i c a A c t a 2 0 2 0 . 1 8 . 2 Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt 2 endogenous deposits. Magmatic melts, in addition to the separation of the fluid phase in the fractional crystallization process, can also cause recycling of water from tanks of different origin. When this occurs, the mixing of fluids, the quantitative ratios of which vary greatly (Taylor and O’Neil, 1977), take place. This determines the complex mechanism of the deposit formation. One of the tasks in this problem involves the establishment of a magmatic source that could provides the ore-forming fluid. We concerned the problem of relation between igneous rocks and hydrothermal ores and of a possible source of F-Be mineralization at the Ermakovka F-Be deposit, which is the largest deposit in the Western Transbaikalia beryllium province. Some researches supposed the relation of F-Be ores with granites of the Shtok massif (Lykhin and Yarmolyuk, 2015; Reyf, 2008), although there are other alkaline igneous rocks within the ore field. The main argument to support this relation is similarity ages of the granite (226Ma, U-Pb, zircon) and F-Be ores (225Ma, Rb-Sr, fluorite) (Lykhin et al., 2001, 2010b). The data of termometry which established a high content of fluid in melt inclusions in quartz from granites enriched with alkalies and fluorine were also included in the evidence. Ore mineralization was mostly due to volatile release from a deep-seated pluton for which crystallization history and fluid exsolution can be tracked by three batches of magma intruded at the level of the ore deposition to form the Yermakovka stock (Reyf, 2008). However there is no explanation of the absence of Be-mineralization in the granite massif. In fact there are no any Be-bearing minerals in schlieren pegmatites located within the massif. It is known that pegmatites (with their high fluid saturation) are often contain ore mineralization, representing an intermediate link between magmatites and hydrothermalites (Frezzotti, 2001; Lowenstern and Thompson, 1995; Roedder, 1992). Detailed isotopic studies (Ripp et al., 2016b) established the participation of meteoric waters in formation of the deposit. GEOLOGICAL BACKGROUND The Ermakovka deposit is located in Western Transbaikalia, 160km east of Ulan-Ude. It is a part of the Western Transbaikalian Be-bearing province, and is localized in the remnant of metamorphosed terrigenouscarbonate rocks among Late Paleozoic granites. The important feature of the deposit is association with the intraplate, Early Mesozoic riftogenic basin, which is filled with volcanic-sedimentary rocks (Lykhin and Yarmolyuk, 2015). The remnant is composed of metamorphosed biotite-quartz-feldspar schists, sandstones, Precambrian crystalline limestones, and dolomites. In the Late Paleozoic Period under the heat influence of the Angara-Vitim granite batholith, it underwent metamorphic transformations at the level of the amphibolite facies, led to the formation of crystalline schists, and the marbleization of carbonate rocks. In the latter, phlogopite, forsterite and tremolite formed. Igneous rocks are represented by small massifs of gabbro-diorites, alkali syenites, leucogranites, and dikes of various compositions (Fig. 1). Leucogranites (the Shtok massif) and alkali syenites formed in the period 225-227Ma (U-Pb, zircon; Rb-Sr, K-feldspar respectively), while host granites beyond the remnant are dated at 316±2Ma (U-Pb, zircon) (Lykhin et al., 2001, 2010b; Lykhin and Yarmolyuk, 2015). Gabbro-diorites compose a tabularlike body 120-150m thick, consist mainly of amphibole and plagioclase. They are skarnified, scapolitized, and chloritized. It is suggested that gabbro-diorites served as a screen for ore-forming fluids (Kupriyanova et al., 2001). The massif of alkali syenites is 0.5km2, located on the northern flank of the deposit and is composed mainly of K-feldspar (60-90%), plagioclase (5-10%) and small amount of quartz. The main dark-colored mineral is aegirine, the amount of which reaches 10%. There are fluorite, apatite, zircon and titanite as accessory in syenites. The syenites are partly carbonatized (up to 5% of calcite) and contain alkali 10-13wt.% (Na2O+K2O), SiO2 (60-64wt.%), Al2O3 (16-18wt.%), CaO (0.5-2.7wt.%) and MgO (less than 1wt.%). The area of the Shtok massif formed by leucogranites is less than 0.5km2. The apical part of them is denudated and drilled up to 1km. There are no Be-containing minerals, and processes of pyrytization, fluoritization and carbonatization, which are widespread in the F-Be ores, are absent in the Shtok massif. The leucogranites contain 72-76wt.% of SiO2, 8-9wt.% of Na2O+K2O, 11-13wt.% of Al2O3; the agpaitic index is 0.96-1.19. An important feature of the leucogranites is their high oxygen fugacity which is caused by ferric iron (FeO= 0.12, Fe2O3= 2.36wt.%) and the presence of hematite. The other feature is the presence of sulfates and phosphates. The latest are also found in schlieren pegmatites and quartz veinlets which contain hematite, florencite, monazite, anglesite and xenotime. Most dikes classified as alkali syenites, syenite-diorite and dioritic porphyrites are pre-ore. Skarns located in southern part of the deposit have been formed during pre-ore stage. They are composed of vesuvianite, garnet (andradite) wollastonite and amphibole. Fluorite-beryllium ores form lenses, veins, veinlets, mineralized breccias grouped into series of subparallel bodies reaching a few hundred meters in lenght. Their thickness ranges from tens of centimeters to a few tens of meters. The largest bodies have massive structure, unrestrained thickness with pinches, swells, branches. They


INTRODUCTION
One of the problems of endogenous deposits is the sources of ore-forming fluids and the relation with the igneous rocks. The detail isotopic and geochemical studying allow to clarify the issue. The complexity of this problem was revealed after conducting modern studies (including isotopic studies) found that fluids and components of metamorphic (Beal and Lentz, 2001;Valley, 1986), juvenile (mantle) sources (Ripp et al., 2018) and meteoric (Broom-Fendely et al., 2016;Johnson and Ripley, 1998;Taylor and O'Neil, 1977) origin participated in the formation of endogenous deposits. Magmatic melts, in addition to the separation of the fluid phase in the fractional crystallization process, can also cause recycling of water from tanks of different origin. When this occurs, the mixing of fluids, the quantitative ratios of which vary greatly (Taylor and O'Neil, 1977), take place. This determines the complex mechanism of the deposit formation. One of the tasks in this problem involves the establishment of a magmatic source that could provides the ore-forming fluid. We concerned the problem of relation between igneous rocks and hydrothermal ores and of a possible source of F-Be mineralization at the Ermakovka F-Be deposit, which is the largest deposit in the Western Transbaikalia beryllium province.
Some researches supposed the relation of F-Be ores with granites of the Shtok massif (Lykhin and Yarmolyuk, 2015;Reyf, 2008), although there are other alkaline igneous rocks within the ore field. The main argument to support this relation is similarity ages of the granite (226Ma, U-Pb, zircon) and F-Be ores (225Ma, Rb-Sr, fluorite) (Lykhin et al., 2001(Lykhin et al., , 2010b. The data of termometry which established a high content of fluid in melt inclusions in quartz from granites enriched with alkalies and fluorine were also included in the evidence. Ore mineralization was mostly due to volatile release from a deep-seated pluton for which crystallization history and fluid exsolution can be tracked by three batches of magma intruded at the level of the ore deposition to form the Yermakovka stock (Reyf, 2008). However there is no explanation of the absence of Be-mineralization in the granite massif. In fact there are no any Be-bearing minerals in schlieren pegmatites located within the massif. It is known that pegmatites (with their high fluid saturation) are often contain ore mineralization, representing an intermediate link between magmatites and hydrothermalites (Frezzotti, 2001;Lowenstern and Thompson, 1995;Roedder, 1992). Detailed isotopic studies (Ripp et al., 2016b) established the participation of meteoric waters in formation of the deposit.

GEOLOGICAL BACKGROUND
The Ermakovka deposit is located in Western Transbaikalia, 160km east of Ulan-Ude. It is a part of the Western Transbaikalian Be-bearing province, and is localized in the remnant of metamorphosed terrigenouscarbonate rocks among Late Paleozoic granites. The important feature of the deposit is association with the intraplate, Early Mesozoic riftogenic basin, which is filled with volcanic-sedimentary rocks (Lykhin and Yarmolyuk, 2015). The remnant is composed of metamorphosed biotite-quartz-feldspar schists, sandstones, Precambrian crystalline limestones, and dolomites. In the Late Paleozoic Period under the heat influence of the Angara-Vitim granite batholith, it underwent metamorphic transformations at the level of the amphibolite facies, led to the formation of crystalline schists, and the marbleization of carbonate rocks. In the latter, phlogopite, forsterite and tremolite formed.
The area of the Shtok massif formed by leucogranites is less than 0.5km 2 . The apical part of them is denudated and drilled up to 1km. There are no Be-containing minerals, and processes of pyrytization, fluoritization and carbonatization, which are widespread in the F-Be ores, are absent in the Shtok massif. The leucogranites contain 72-76wt.% of SiO 2 , 8-9wt.% of Na 2 O+K 2 O, 11-13wt.% of Al 2 O 3 ; the agpaitic index is 0.96-1.19. An important feature of the leucogranites is their high oxygen fugacity which is caused by ferric iron (FeO= 0.12, Fe 2 O 3 = 2.36wt.%) and the presence of hematite. The other feature is the presence of sulfates and phosphates. The latest are also found in schlieren pegmatites and quartz veinlets which contain hematite, florencite, monazite, anglesite and xenotime.
Most dikes classified as alkali syenites, syenite-diorite and dioritic porphyrites are pre-ore. Skarns located in southern part of the deposit have been formed during pre-ore stage. They are composed of vesuvianite, garnet (andradite) wollastonite and amphibole.
Fluorite-beryllium ores form lenses, veins, veinlets, mineralized breccias grouped into series of subparallel bodies reaching a few hundred meters in lenght. Their thickness ranges from tens of centimeters to a few tens of meters. The largest bodies have massive structure, unrestrained thickness with pinches, swells, branches. They are accompanied by veinlet mineralization. The massive ores formed as a result of metasomatic replacement of carbonate rocks (Kupriyanova et al., 2011;Novikova et al., 1994). Most of the contacts of ores and carbonate rocks have sharp boundaries.
The orebodies composed by 20-70% fluorite. The typomorphic minerals are K-feldspar, dolomite, calcite, apatite, quartz, pyrite; the subordinate minerals are albite, rutile, amphibole, galena, sphalerite. According to the predominant Be-bearing mineral (Novikova et al., 1994) orebodies are grouped into two types. In one of them, the main Be-bearing minerals are phenakite and bertrandite, while in the other the main Be-bearing minerals are eudidymite, leucophanite.
Beryllium minerals form a dissemination of irregularly shaped grains, spherulites, and fine nests (Fig. 2). Most of the phenakite is confined to the interstices of fluorite grains. Phenakite forms rounded bundles up to 1-3cm in size in massive ores, and spherical crystals -in the veins enriched with carbonates. Bertrandite formed later than phenakiteand is more characteristic of the upper-deposit horizons. It is confined to the interstices of fluorite grains, makes nests, and veinlet-like aggregates often with interstices made of tabular crystals. Dolomite and calcite comprise up to 3-10% of the ore parageneses volume. Dolomite formed at an early stage. K-feldspar in massive ores is represented by dissemination and coarse-grained anchimonomineral aggregates. It is confined to the vein wall, along with phenakite in carbonate-enriched veins.    Apatite is one of the earliest minerals; it forms prismatic crystals and their clustered aggregates. There is quartz up to 3-4 %, as well as dissemination and nest-like bodies of pyrite, sphalerite, and galena in the majority of ore bodies.
According to thermometry the deposit has been formed at 400-120ºC Reyf, 2004, 2008). There are three mineral assemblages: i) the earliest stage is pre-ore. Albitization and microclinization of hosted rocks have taken place during this stage at 300-400ºC; ii) the second stage is the main ore-forming. The majority of F-Be-ores have been formed at 200-310ºC which is presented by phenakite, bertrandite, eudidimite, leucophanite, meliphanite and fluorite as the main mineral. Also microcline, apatite, dolomite, calcite, pyrite and alkali amphibole have been formed during this stage; iii) the majority of calcite has been formed during the latest stage 120-220ºC. Also some Be-minerals (phenakite, bertrandite) have been replaced by milarite and bavenite. The calcite veins formed during this stage contain pyrite, sphalerite, galena, molybdenite and microcline.
A chart of mineral formation sequence is presented in Figure 3. According to thermometry there is high amount of CO 2 in fluid inclusions from ore minerals.

ANALYTICAL METHODS
The microtextural features, relations, and homogeneity of the minerals were studied by electron microscopy coupled with energy-dispersive spectrometry (SEM EDS). Most of the SEM EDS analyses were conducted on a Carl Zeiss LEO-1430VP (LEO Electron Microscope) electron microscope equipped with an INCA Energy 350 (Oxford Instruments Nanoanalysis) analytical system. Minerals were analyzed at 20kV accelerating voltage, 0.5nA beam current, and 50s counting time. The detection limits of the elements were 0.2-0.3wt.%, and the random analytical errors were for major (>10wt.%), for minor (1-10wt.%), and for trace (0.3-1wt.%) elements 0.9, 3.0, and 13 relative %, respectively. Minerals were analyzed by scanning over >10μm 2 rectangular spots (if the analyzed phases were larger than this area).
The oxygen isotopic composition in the silicates was analyzed using laser fluorination. All the measurements were carried out on a Finnigan MAT 253 mass spectrometer (ThermoFinnigan, Bremen, Germany) using a double inlet system for oxygen in silicates. The measurements were calibrated using international standards NBS-28 (quartz), NBS-30 (biotite) (Coplen, 1988) for silicates. The error of the values obtained did not exceed 0.2-0.3‰.
The isotopic composition of Nd and Sr was measured using a Triton multichannel mass spectrometer in a static regime. The reproducibility of the determinations of the Rb, Sr, Sm, and Nd isotopic compositions was estimated to be ±0.5% from the replicate analyses of the BCR (Basalt Columbia River) standard. The total blanks were 0.05ng for Rb, 0.2ng for Sr, 0.3ng for Sm, and 0.8ng for Nd. The results of the analysis of a standard BCR-1 sample (6 measurements) were as follows: Sr= 336.7μg/g, Rb= 47.46μg/g, Sm= 6.47μg/g, Nd= 28.13μg/g, 87 Rb/ 86 Sr= 0.4062, 87 Sr/ 86 Sr= 0.705036±22, 147 Sm/ 144 Nd= 0.1380, 143 Nd/ 144 Nd= 0.512642±14. The reproducibility of the isotope analyses was evaluated using the measurements of the La Jolla and SRM-987 standards. Concurrently with the Sr measurements, the 87 Sr/ 86 Sr ratio in the SRM-987 standard was found to be 0.710241±15 (2σ, 10 measurements), whereas the value of 143 Nd/ 144 Nd in the La Jolla standard was 0.511847±8 (2σ, 12 measurements). The Sr isotope composition was normalized to 88 Sr/ 86 Sr= 8.37521, whereas the Nd composition was normalized to 146 Nd/ 144 Nd= 0.7219. The Nd isotope composition was corrected to 143 Nd/ 144 Nd= 0.511860 in the La Jolla standard.
The age of fluorite-phenakite-bertrandite ores was determined by apatite from two sites with the help of LA-ICP MS method. Apatite grains were placed on doublesided sticky tape and epoxy glue, then poured into a 2.5cm diameter mould on top of the zircon grains and polished. The analyses were carried out using an Agilent 7900 ICP-MS quadrupole spectrometer connected to a 193mm coherent ArF gas laser and Resonetics S155 ablation cell.  (Kosals et al., 1973) of pre-ore, syn-ore and post-ore stages are given. Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt 6 The downhole fractionation, instrument drift and mass bias correction factors for Pb/U ratios were calculated using two analyses on the primary zircon standards (Barfod et al., 2005;Chew et al., 2011) and two analyses on each of the secondary zircon standards (Amelin and Zaitsev, 2002;Chew et al., 2011;Schoene and Bowring, 2006), analyzed at the beginning of the session and every 12 unknown apatites, using the same spot size as used on the samples. The correction factor for the 207 Pb/ 206 Pb ratio was calculated using 2 analyses of the NIST610 standard analyzed throughout analytical session and corrected using the values (Baker et al., 2004). Each analysis began with a 30 second analysis of the blank gas measurement followed by a further 30 seconds of analysis time when the laser was switched on. Apatite was sampled on 29μm spots using the laser at 5Hz and a density of approximately 2J/cm 2 . A flow of He gas at a rate of 0.35litres/minute carried particles ablated by the laser out of the ablation cell to be mixed with Ar gas and carried to the plasma torch.  (Meffre et al., 2008) with additional changes to correct low values of total lead in the primary standard, using the 207 Pb correction according to (Chew et al., 2011).
A study of the fluid phase composition in fluorites from ores and granites of the Shtok massif was carried out by chromatography-mass spectrometry. The gas mixture released from fluid inclusions was analyzed on a Thermo Scientific (USA) DSQ II MS/Focus GC chromatography-mass spectrometer at the Institute of Geology and Mineralogy SB RAS. The preparations were placed in a special device included in the gas scheme of the chromatograph before the analytical column, heated at 140ºC for 130 minutes in a He stream and destroyed by means of a punch. The gas mixture extracted from the sample during its impact destruction was entered online in a He flow without concentration, including cryofocusing. The separation of the sample into components was carried out in a gas chromatograph on a Restek Rt-Q-BOND capillary column. Ionization mass spectra by electron impact on the total ion current were obtained on a quadrupole mass-selective detector in the Full Scan mode. Mass spectral conditions: the electron energy is 70eV, the emission current is 80μA, the temperature in the ion source is 200ºC, the amplifier voltage is 1350V, the polarity of the detected ions is positive. The analysis start was synchronized with the sample destruction moment. Before and after the "working" analysis, blank online analyzes were carried out, which allowed to control the release of gases sorbed by the sample surface, including atmospheric components, and at the end of this process -to record the systock form. If necessary, the analytical column was thermally conditioned until the required blank was achieved.
Chromatography-mass spectrometry data with peak identification and extraction of individual components from overlapping peaks were interpreted using the software package AMDIS (Automated Mass Spectral Deconvolution and Identification Systock) version 2.66, and in manual mode with background correction using the NIST 2011 mass spectral libraries and Wiley 9 using the program NIST MS Search version 2.0. The relative concentrations of volatile components in the separated mixture were established by the normalization method: the sum of the areas of all chromatographic peaks of the analyzed mixture was equal to 100%, and the individual component percentage in the analyzed mixture was determined by its area in the analyzed mixture (Sokol et al., 2017;Tomilenko et al., 2015).

RESULTS
This study was carried to assess the sources of fluids which formed the F-Be-mineralization. It includes the age determination of ores, and the geochemical characterization of igneous rocks and hydrothermalites. Special attention was paid to the hydrothermal mineralization within the Shtok massif. In this study, the geochemical data presented by Lykhin and Yarmolyuk (2015) is also included.

Granites and pegmatites of the Shtok massif
The Shtok massif, considered as a source of oreforming fluids, attracts the most attention of researchers among igneous rocks (Lykhin et al., 2010a;Reyf, 2008). It is formed by leucocratic subalkaline granites, which contain schlieren pegmatites. Hematitization and quartz veinlets are founded in some areas of the massif, and they are accompanied by leaching of K-feldspar and its replacement by kaolinite and muscovite. The processes of carbonatization and pyritization, which are widespread within the ore field are not found in the granites.
Zircon, apatite, titanite, monazite, xenotime, allanite, rutile and fluorite are accessory minerals in granites. Granites are characterized by low (2-5ppm) Be-concentration. There are neither elevated levels of beryllium in the dome-shaped juts of this stock nor beryllium minerals in pegmatites.
The most important feature of granites is its high oxygen fugacity, which caused the occurrence of almost exclusively ferric iron (in granite, FeO= 0.12, Fe 2 O 3 = 2.36, in pegmatite FeO= 0.08, Fe 2 O 3 = 2.06). Alkali sulfates were found in melt inclusions of granites and pegmatites (Reyf and Ishkov, 1999).
The REE-normalized patterns for granites and pegmatites have a deep Eu-minimum and are identical to patterns for quartz veins which cut granites and contain sulphates and phosphates (Fig. 4). The Eu/Eu* values in them vary within 0.12-0.29. The (La/Yb) n ratios are 2.40-2.98, Th/U ratios are from 1 to 3 and Sr/Rb ratios are from 0.1 to 10.
The initial strontium ratios of granites and pegmatites are in the range of 0.7056-0.7065 (Table I, see appendix). The oxygen isotope composition in quartz from these rocks is in the range of 6.9-7.9‰ δ18О (V-SMOW) (Table II; Fig.  5).
Alkali feldspars from syenites have high concentration of BeO (Lykhin and Yarmolyk, 2015). The REE-normalized patterns for syenites differ from granites and are similar to F-Be ores (see Fig. 4). There is no Eu-minimum and the (La/Yb) n ratios are in the range from 7 to 16.

Hydrothermalites
There are two types of hydrothermalites at the deposit area, which are contrastingly different in mineral composition. The first type includes F-Be associations and is located outside the Shtok massif. Hydrothermalites of this type are described in detail in (Kupriyanova et al., 2011;Lykhin and Yarmolyuk, 2015). The obtained age (U-Pb, LA-ICP MS, apatite) of F-Be ores is 225.1±6.2 Ma and 219±1.2Ma ( Fig. 6; Table III). The ores are enriched in light lanthanoids; they are distinguished by a slight slope of the content normalized patterns, and the absence of a Euminimum (Table IV). Their (La/Yb) n ratio averages 10.5. The ores are also characterized by high Sr/Rb (over 50) and Th/U (50-100) ratios. The REE-normalized patterns differ from granites of the Shtok massif (see Fig. 4).
The primary Sr ratios in whole-rock samples and non-Rb minerals exceed 0.707, reaching in some cases 0.708 (see Table I). The ore-forming minerals, including quartz, have low δ 18 O values (see Table II). The δ 18 O values in carbonate minerals (Fig. 7) are also low. This indicates the involvement of the meteor source in the formation of the ores (Ripp et al., 2016b) together with deuterium depletion of water from hydroxyl-bearing minerals (from -130 to -177‰δD), as well as calculations of the oxygen content of equilibrium water with ore paragenesis minerals (-2 ... The second type of hydrothermalites occurs inside the Shtok massif. It is represented by quartz veinlets with sulfates and phosphates. Some of the veinlets have a finegrained structure and a small thickness (less than 1cm, cements crushing zones in granites). They contain a large amount of corroded K-feldspar xenoliths, dissemination of monazite, xenotime and florencite (Fig. 8). The other part is represented by veinlets, up to several centimeters in thickness, up to 10 meters in length and is composed of quartz with caverns and interstices. The presence of caverns is probably a result of leaching of sulfates or halides. These veinlets are found on the northern flank of the massif, and confined to hematitization zones. Hematite is found in K-feldspar in the form of dispersed dissemination, veinlets and sometimes large isolations. Ferric iron (FeO= 0.16, Fe 2 O 3 = 6.5wt.%) prevails in quartz veinlets. The quartz veinlets contain fine-scale muscovite, kaolinite, sulfate and phosphate minerals (see Fig. 8). They also contain fluorite and xenoliths of hematitized K-feldspar. The latter are   (Sun and McDonough, 1989) of granites, alkaline syenites, schlieren pegmatites, quartz veins and F-Be ores of the Shtok massif. o l o g i c a A c t a , 1 8 . 2 , 1 -1 3 , I -V I ( 2 0 2 0  Florencite is mainly confined to muscovite, monazite and xenotime to quartz (see Fig. 8). There is 0.9-1.5wt.% of SrO in florencite, and there is phengite component (0.8-2.6apfu of Fe and 0.2-0.3apfu of Mg) in muscovite.
The hydrothermally-altered granites (with hematitization) and quartz veinlets, have higher concentrations of REE, Y, Th, Ba, and chalcophile elements than unaltered granites (Table V; Fig. 9). The REE-normalized patterns for them are identical to the patterns for granites and schlieren pegmatites (see Fig. 4), they have a low Eu-minimum (Eu/Eu*= 0.23-0.28) and similar ratios (La/Yb)n, which are 2.5. They also differ in low Sr/Rb (0.1) and Th/U (0.1-3) ratios. The oxygen isotope composition in quartz is characterized by its proximity to the composition of quartz from granites and pegmatites (see Table II).  l o g i c a A c t a , 1 8 . 2 , 1 -1  Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt 9 According to chromatography-mass spectrometry analysis of fluid inclusions in fluorites from granites and F-Be ores (Table VI) the main volatiles are H 2 O and CO 2 . The fluorites from granites contain less H 2 O than one from the ores. The higher concentration of CO 2 is in fluorites from granites. Apart from this there are hydrogen sulfide (H 2 S), sulfur hexafluoride (SF 6 ), carbonyl sulfide (COS) and thiophenes. The main feature is the presence of molecular oxygen in fluid inclusions in fluorite from granites. A higher concentration of unsaturated hydrocarbons (alkenesalkynes) in fluid inclusions in fluorite from F-Be ores than in fluorite from granites indicates the oxidizing conditions for the formation of the latter.

DISCUSSION
One of important problems of the Ermakovka deposit is the source of the ore-forming fluids and a relationship between F-Be ores and igneous rocks. Lykhin and Yarmolyuk (2015) supposed that the source of F-Be ores were granites of the Shtok massif because they have similar ages but the age of F-Be ores (225Ma) is also close to the age of alkaline syenites (227Ma) which could also be a source of the ore-forming fluids. However these granites and schlieren pegmatites do not contain any Be-bearing minerals. The content of Be is in the range 2-5ppm and is similar to other granites of Transbaikalia. Reyf and Ishkov (1999) suggested the existence of a specific fluid with high beryllium recovery efficiency.
The Shtok massif granites with sulfate and phosphate mineralization are less about this role. According to the known data on the solubility of beryllium compounds with different ligands (Wood, 1992), sulfate and chloride complexes are characterized by a minimum relative to other (fluoride and fluorine-carbonate) melt beryllium extraction. The latter is confirmed by the absence of beryllium in hydrothermalites that are widespread within the stock. The composition of the veinlets indicates that mainly chalcophile and rare-earth elements were removed from granites, and beryllium, lithium, cesium, titanium, and tin were not removed. Consequently, the Shtok massif granites should have formed not F-Be, but sulfate and phosphate mineralization.
The initial Sr 87 /Sr 86 ratios and geochemical features of F-Be ores and granites of the Shtok (respectively, 0.7056 and more than 0.707) indicate different sources of them.
There are no carbonate minerals in granites but the F-Be ores contain up to 3-10wt.% CO 2 . The suggestion about the occurrence of carbonates in ores as a result of the assimilation of limestones during their decarbonization is not supported by isotope studies (Ripp et al., 2016a). This is indicated by the sharp enrichment of carbonates of F-Be ores with low δ 18 O values up to -2.5... +2.0 ‰ δ 18 О with 15-22 ‰ in limestones (dolomites). The low δ 18 O values (mostly less than 3-5‰) are also recorded in other (including beryllium) minerals of the ore phase (Ripp et al., 2016b).
The compositions of the fluid inclusions in fluorites from granites and F-Be ores are different. Hydrogen and methane are found in fluid inclusions in minerals of the latter (Kosals et al., 1973); it indicates the reducing nature of the ore-forming solutions. Granites (and schlieren pegmatites) have a sulfate and phosphate mineralization, which, together with the predominance of ferric iron and the presence of free oxygen in fluid inclusions, indicates a high fugacity of oxygen and their oxidative specificity.
The difference in the configuration of normalized rare-earth elements and, in particular, the presence of the europium anomaly in granites and the lack of it in F-Be ores (see Fig. 4), also testifies not in favor of their connection. At the same time, the inheritance of the configuration of the diagrams is fixed in hydrothermalites that are widespread within the granite stock.
Finally, the participation of meteor source water (Ripp et al., 2016b) in the fluids that formed the F-Be ores shows the need to explain its occurrence in the magmatic chamber and the mechanism for the release of such fluid. At least one model of its exudation, as a result of fractional crystallization, is no longer enough.  (Bowman, 1998). Numerals on the parabolas of theoretic mixing trends mark CO 2 concentration in the solution (Taylor et al., 1967). At the upper corner, curves for calc-silicate decarbonatization at 300-500ºC (Baumgartner and Valley, 2001) o l o g i c a A c t a , 1 8 . 2 , 1 -1  Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt 11 A possible source of F-Be ores could be alkaline syenites. The F-Be ores contain eudidymite, leucophanite, meliphanite, milarite and bavenite, such minerals usually common to alkaline rocks. The alkaline synenies of the Ermakovka contain high concentration of Be (22ppm). The alkaline syenites normalized REE patterns are close to F-Be ones (see Fig. 4). Both alkaline syenites and F-Be ores have low δ 18 O values while the granites have higher δ 18 O values (7-7.93‰). New U-Pb dating of apatite from F-Be ores has shown an age of 225Ma, which is closed to the age of alkaline syenites (227Ma).

CONCLUSION
There are two types of hydrothermalites with contrasting compositions at the Ermakovka deposit. One of them, is represented by quartz veinlets with sulfate and phosphate minerals. They are specialized in REE and contain monazite, xenotime and florencite. These veinlets are located within the granites of the Shtok massif. The second type, is represented by F-Be ores. It occurs outside the granite massif.
Mineralogical and geochemical features of quartz veinlets with sulfate and phosphate minerals evidence a  l o g i c a A c t a , 1 8 . 2 , 1 -1  Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt genetic relation with granites. The F-Be ores have similar δ 18 O values, ages and REE-normalized patterns to alkaline syenites.
Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt I   Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt II Note. Samples 1-2, after (Lykhin and Yarmolyuk, 2015) o l o g i c a A c t a , 1 8 . 2 , 1 -1  Phanerozoic magmatism and ore-forming systems of the Syan-Baikal fold belt VI Table 6. Composition (%) and amount (in brackets) of volatile components released during the opening of fluid inclusions in fluorites from granites (E-13) and ores (E-37-13) of the Ermakovskoe deposit (according to GC-MS analysis).