Gold Mineralization at the Maletoyvayam Deposit (Koryak Highland, Russia) and Physicochemical Conditions of Its Formation

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Article Gold Mineralization at the Maletoyvayam Deposit (Koryak Highland, Russia) and Physicochemical Conditions of Its Formation

Evgeny G. Sidorov 1, Andrey A. Borovikov 2, Nadezhda D. Tolstykh 2,3,*, Daria S. Bukhanova 1 , Galina A. Palyanova 2,3 and Valery M. Chubarov 1 1 Institute of Volcanology and Seismology, Far East Branch of Russian Academy of Sciences, Piipa Blvd., 9, Petropavlovsk-Kamchatsky 683006, Russia; [email protected] (E.G.S.); [email protected] (D.S.B.); [email protected] (V.M.C.) 2 Sobolev Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences, Koptyuga Ave., 3, Novosibirsk 630090, Russia; [email protected] (A.A.B.); [email protected] (G.A.P.) 3 Department of Geology and Geophysics, Novosibirsk State University, Pirogova Ave., 2, Novosibirsk 630090, Russia * Correspondence: [email protected]

Received: 25 October 2020; Accepted: 3 December 2020; Published: 5 December 2020

Abstract: Microthermometry study of fluid inclusions in quartz veins of the Maletoyvayam deposit (Koryak Highland, Russia) was carried out. This epithermal gold deposit contains unique Au compounds including maletoyvayamite, which has not been reported anywhere else. Two paragenetic mineral associations (pyrite-quartz and maletoyvayamite-quartz) with quartz of different generations corresponding to different pulses were also described. Only early generations of quartz (Q1) include ore minerals: pyrite for the first mineral assemblage, and in Au-bearing minerals, sulfosalts, bismuthinite, and others—for the second assemblage. A study on fluid inclusions in quartz showed a salinity (mainly NaCl + KCl) range from 0.2 to 4.3 wt.% NaCl eq., increasing from the first mineral association to the second due to boiling fluids. The obtained temperature variations for quartz crystallization were 295–135 ◦C, the fluid pressure ranged from 79 to 4 bar. On the other hand, the range of conditions obtained for the gold productive ore association is more narrow: salinity of the fluid inclusions is 4.3 wt.% NaCl eq., the temperatures vary from 255 ◦C to 245 ◦C, and the pressure from 39 to 32 bar. These physicochemical characteristics of the Maletoyvayam ore deposit greatly coincide with other HS-type epithermal deposits; however, within the Central Kamchatka Volcanic Belt it is so far the only deposit of this type reported.

Keywords: Central Kamchatka Volcanic Belt; HS epithermal deposit; maletoyvayamite-quartz association; ﬂuid inclusions; gold

1. Introduction The term “epithermal” was defined by W. Lindgren [1] to include a broad range of tellurides, antimonides or selenides of Au, Ag and base metals deposits which he estimated to be formed from aqueous fluids at low temperatures (less than 200 ◦C) and moderate pressures. It is, however, now generally accepted that mainly magmatic fluids at slightly higher temperatures (200–300 ◦C) and pressures of less than a few hundred bars participate in the formation of these type of deposits. Nevertheless, the term “epithermal” is still widespread [2]. Taylor, Hedenquist and coauthors [3,4] consider that an epithermal Au deposit consists of three subtypes: high sulfidation (HS), intermediate sulfidation (IS), and low sulfidation (LS), each represented by characteristic alteration mineral assemblages, occurrences, textures, and characteristic suites of

Minerals 2020, 10, 1093; doi:10.3390/min10121093 www.mdpi.com/journal/minerals Minerals 2020, 10, 1093 2 of 19 associated geochemical elements. The term HS (high sulfidation) is now widely used [5], and combines many other previously described types: enargite–gold [6], Goldfield-type [7,8], high-sulfur [9,10], quartz-alunite [11] and alunite–kaolinite [12] which were assigned to a group of epithermal deposits based on their mineralogical and geochemical features. HS type deposits are characterized by the presence of diagnostic minerals of high sulfidation conditions (e.g., enargite), acidic hydrothermal conditions (e.g., alunite, kaolinite) and relatively oxidized conditions of sulfur (SO2-rich) in the hydrothermal system. HS deposits are associated with some types of hydrothermal systems due to influence of a deep magma chamber [13] and also with andesitic volcanoes in which surface manifestations include high-temperature fumaroles and acid sulfate-chloride hot springs. In contrast, LS deposits of reduced (H2S-rich) hydrothermal fluids with neutral pH are similar to those found in geothermal systems [13], that exhibit in the surface: sinter-terraces of silica, hot springs and steam-heated acid-sulfate alterations [14]. Within the Kamchatka Peninsula, Au-Ag epithermal deposits are localized in volcanic belts of different ages (Eocene-Oligocene Koryak-West Kamchatka, Oligocene-Quaternary Central Kamchatka, and Pliocene-Quaternary East Kamchatka), extending along the modern subduction trend [15–19]. All of the Au-Ag mines located there (Aginskoe, Asacha, Ametistovoe, Zolotoe, Baran’evskoe, Kungurtsevskoe, Oganchinskoe, Ozernovskoe), as well as most of the known Au-Ag deposits and prospects, fit into the LS epithermal type [19–23]. These deposits are characterized by the presence of quartz, adularia, illite and calcite in Au-Ag-bearing veins. The Maletoyvayam deposit located in the Central Kamchatka Volcanic Belt (CKVB) is restricted to volcano–tectonic structures within the Vetrovayam volcanic zone situated in the northeastern part of the CKVB (southwestern part of the Koryak Highland) [24,25]. On the contrary to the above mentioned deposits, Maletoyvayam deposit belongs to the HS type category of epithermal deposits [26], which are also known in the Eastern part of Russia (Belaya Gora and Svetloye) [27]. The predominance of andesite and basaltic andesite rocks in the CKVB is a reflection of the mafic composition of its basement. This factor determines the particularity of the metallogeny on this zone, characterized by a wide development of near-surface mineralization of tellurides as subtypes of the main gold-silver deposits [28]. The veins of massive quartz are included in the vuggy silica, and both are Au(Ag)-bearing. The central vuggy silica zones are rimmed along the periphery of the ore field by quartz-alunite-kaolinite association. The Maletoyvayam HS type deposit differs from others known on the Kamchatka Peninsula, which are of the LS type, by a great variety of mineral phases: native gold, chalcogenides of Au and Ag, Cu-sulfosalts with Sb and As, as well as complexes including Au-bearing oxides among which some are considered rare or unique. Contrary to the other deposits of the CKVB, native gold in these ores is not dominant. The study of other styles of gold occurrences in sulfide-telluride-selenide ores and the physicochemical conditions of their formation are of great interest from a mineralogical, genetic and technological point of view [29]. The first results on the mineral composition of Maletoyvayam deposit were obtained recently [26,30–35]. Typical and uncommon minerals of epithermal systems were reported in this deposit: senarmontite (Sb2O3), tripuhyite (FeSbO4), bismite (Bi2O3), rooseveltite (Bi(AsO4)), tiemannite (HgSe), antimonselite (Sb2Se3), Te-,Sb-bearing guanajuatite: (Bi2(Se,Te)3 and (Bi,Sb)2Se3), bismuthinite ((Bi2S3) and (Bi,Sb)2(S,Se)3), unnamed phase ((Sb,Bi,Te,As,Fe)2O5), tellurium (Te,Se). In addition, unique compounds, that had not been previously found in nature, were reported: maletoyvayamite and its S-rich analogue (Au3Se4Te6 and Au3S4Te6), AuSe and Au(Te,Se); their occurrence is due most likely to specific properties of the hydrothermal solutions. Microthermometric study of these ores had not previously been carried out. Thus, the purpose of this study is to present mineralogical and microthermometric measurement data of this particular type of ore and to show the physicochemical conditions that played an important role in the ore accumulation. Minerals 2020, 10, 1093 3 of 19

2. Regional Geology and Mineralization The Central Kamchatka Volcanic Belt (Russia) is about 1800 km long, controlled by the Main Kamchatka deep fault, displaying a significant number of gold-silver epithermal deposits [22,28]. Minerals 2020, 10, x FOR PEER REVIEW 3 of 19 The Maletoyvayam deposit is particularly confined to a volcano-tectonic structure (up to 30 km) within thethe Vetrovayam Vetrovayam volcanic zone located in the northeastern northeastern region region of of the the Central Central Kamchatka Kamchatka Volcanic Volcanic Belt and delimited by the Koryak Highland in the so southwesternuthwestern part [24,25]. [24,25]. This This whole whole structure structure is controlled byby thethe Vyvensky Vyvensky northeast-striking northeast-striking deep deep fault fault and theand northwest-striking the northwest-striking faults zonefaults [36 zone,37]. [36,37].Stratified Stratified subvolcanic subvolcanic and intrusive and intrusive formations, formations, as well as as Quaternary well as Quaternary sediments, sediments, are the constituent are the constituentelements of elements the ore field of the (Figure ore field1). (Figure 1).

Figure 1. Schematic geological geological map map (volcano-tectonic (volcano-tectonic stru structure)cture) of of the the Maletoyvayam Maletoyvayam gold gold deposit, deposit, modifiedmodiﬁed after StefanovStefanov andand SchirokySchiroky [ 37[37].]. 1—Quaternary 1—Quaternary deposits; deposits; 2,3—rocks 2,3—rocks of of the the upper upper member member (2) (2)and and the the lower lower member member (3) of (3) the of Vetrovayam the Vetrovayam Formation Formation (Middle-Late (Middle-Late Miocene); Miocene); 4—Vetrovayam 4—Vetrovayam volcanic volcaniccomplex (Latecomplex Miocene); (Late 5—mainMiocene); faults; 5—main 6—faults faults; covered 6—faults by Quaternary covered by deposits; Quaternary 7—hydrothermally deposits; 7— hydrothermallyaltered rocks; 8—ore altered occurrences rocks; 8—ore (numbers occurrenc in circles):es (numbers 1—Yubileyny, in circles): 2—Yugo-Zapadny, 1—Yubileyny, 3—Gaching, 2—Yugo- Zapadny,4—Tyulul; 3—Gaching, 9—Sampling 4—Tyulu location.l; 9—Sampling location.

StratifiedStratified deposits areare representedrepresented by by e ffeffusive,usive, pyroclastic, pyroclastic, and and tu fftuffaceous-sedimentaryaceous-sedimentary rocks rocks of the of theVetrovayam Vetrovayam Formation Formation (Figure (Figure1), which 1), which are divided are divided into two into lithostratigraphic two lithostratigraphic members. members. The lower The lowermember member (N1vt1 )(N is1vt composed1) is composed of tuff andof tuff tu ffandbreccia tuff ofbreccia intermediate of intermediate to basic composition,to basic composition, andesite, andesite,basaltic andesite, basaltic andesite, and, less and, often, less dacite often, and dacite felsic an tud fffelsic. At tuff. the baseAt the of base this member,of this member, there are there lenses are lenses and interlayers of tuffaceous sandstone, tuff conglomerate, tuff siltstone, and brown coal. The upper member (N1vt2) of the Vevetrovayam Formation is 10–30 m thick and composed mainly by effusive rocks: andesite and basaltic andesite. Interlayers of basalt, tuff, tuff breccia, and tuff conglomerates of intermediate and mafic composition are less common. The radiometric age for effusive rocks (K/Ar method) is 7–18 Ma [38]. Intrusive subvolcanic bodies and dikes form a single volcanic complex (Vetrovayam), which is represented by diorite, quartz diorite and granodiorite. The age of this complex was determined as Middle-Late Miocene [38]. Volcanic rocks in the area exhibit

Minerals 2020, 10, 1093 4 of 19 and interlayers of tuffaceous sandstone, tuff conglomerate, tuff siltstone, and brown coal. The upper member (N1vt2) of the Vevetrovayam Formation is 10–30 m thick and composed mainly by effusive rocks: andesite and basaltic andesite. Interlayers of basalt, tuff, tuff breccia, and tuff conglomerates of intermediate and mafic composition are less common. The radiometric age for effusive rocks (K/Ar method) is 7–18 Ma [38]. Intrusive subvolcanic bodies and dikes form a single volcanic complex

(Vetrovayam),Minerals 2020, 10 which, x FOR isPEER represented REVIEW by diorite, quartz diorite and granodiorite. The age of this complex4 of 19 was determined as Middle-Late Miocene [38]. Volcanic rocks in the area exhibit different degrees of hydrothermaldifferent degrees alteration, of hydrothermal which are alteration, associated which with areasare associated of gold mineralizationwith areas of gold and mineralization sulfur deposits exploredand sulfur in 1971 deposits [25,36 explored,38]. The in Maletoyvayam1971 [25,36,38]. depositThe Maletoyvayam includes four deposit areas includes (ore occurrences) four areas where(ore goldoccurrences) ore reserves where have gold been ore identified reserves have and estimated:been identified Yubileyny, and estimated: Yugo-Zapadny, Yubileyny, Gaching Yugo-Zapadny, and Tyulul. GachingBased and on theTyulul. types of mineral assemblages [26], these ore occurrences are associated to a HS epithermalBased type on the [4,39 types,40]. of However, mineral theyassemblages differ among [26], these themselves ore occurrences in the degree are associated of oxidation to a ofHS the primaryepithermal mineralization. type [4,39,40]. For However, instance, atthey the differ Gaching among occurrence, themselves the in ores the aredegree less of oxidized oxidation (about of the 10% sulfateprimary iron mineralization. and 90% sulfide For iron),instance, compared at the Gaching to the Yugo-Zapadnyoccurrence, the ores occurrence, are less oxidized where sulfide (about 10% iron is onlysulfate 8%. iron Hence, and the 90% primary sulfide mineralizationiron), compared atto thethe GachingYugo-Zapadny ore occurrence occurrence, is consideredwhere sulfide to iron be more is preservedonly 8%. and Hence, for thatthe primary reason itmineralization was selected andat the analyzed Gaching inore the occurrence present study. is considered to be more preserved and for that reason it was selected and analyzed in the present study. Maletoyvayam deposit is composed of rocks of the lower member of the Vetrovaym Formation. Maletoyvayam deposit is composed of rocks of the lower member of the Vetrovaym Formation. Vuggy silica was identified in the central part of the ore field, transitioning outwards into quartrz-alunite, Vuggy silica was identified in the central part of the ore field, transitioning outwards into quartrz- quartz-kaolinite, quartz-sericite-kaolinite and then to argillic- and propylitic-altered rocks. Gold was alunite, quartz-kaolinite, quartz-sericite-kaolinite and then to argillic- and propylitic-altered rocks. found both in vuggy silica remnants located on the watershed in the Gachingalhovayam river valley Gold was found both in vuggy silica remnants located on the watershed in the Gachingalhovayam (Figureriver 2valleya), and (Figure in quartz 2a), and veins. in quartz The veins. color Th ine rockcolor samples in rock samples showing showing vuggy vuggy and massiveand massive silica texturesilica texture is light is gray light to gray gray to gray (Figure (Figure2b). 2b). In theIn the samples samples with with texture texture the the mainmain mineral phase phase is is quartz—85–90quartz—85–90 vol.%; vol.%; kaolinite—5 kaolinite—5 vol.%, vol.%, andand alunite—4–5alunite—4–5 vol.%; vol.%; the the rest rest of of the the minerals minerals correspond correspond toto potassium potassium feldspar, feldspar, barite, barite, anglesite, anglesite, muscovite, muscovite, etc.etc.

FigureFigure 2. 2. ((aa)) Vuggy Vuggy silica silica in inthe the Gachingalhovayam Gachingalhovayam river rivervalley, valley, (b) Vuggy (b) Vuggysilica sample silica with sample quartz with quartzveins, veins, (c) fragment (c) fragment of quartz of quartz vein veincontaining containing the male thetoyvayamite-quartz maletoyvayamite-quartz association, association, Gaching Gaching ore oreoccurrence. occurrence.

TheThe dark dark zones zones in in samples samples exhibiting exhibiting vuggyvuggy silica texture texture are are due due to to the the presence presence of ofan an intense intense disseminationdissemination of of mainly mainly pyrite, pyrite, or or sulfosalts sulfosalts alongalong with gold mineralization. mineralization. Au Au content content in insamples samples withwith vuggy vuggy silica silica texture texture reaches reaches 8.8 8.8 ppm,ppm, whereaswhereas Ag—47.2Ag—47.2 ppm. The The white white quartz quartz veins veins also also containcontain a a ﬁne-grained fine-grained disseminationdissemination of of ore ore minerals, minerals, which which is irregularly is irregularly distributed distributed (Figure (Figure 2c). The2c). Theconcentration concentration of ofAu Au in inquartz quartz veins veins vary vary within within the the range range 1.40–144 1.40–144 ppm, ppm, and and for for Ag—147–724 Ag—147–724 ppm. ppm. Other ore elements show concentrations of: Cu—1.38–3.18; As—up to 2; S—up to 2.26; Sb, Se, Te— Other ore elements show concentrations of: Cu—1.38–3.18; As—up to 2; S—up to 2.26; Sb, Se, Te—more more than 0.2 (wt.%) [25]. than 0.2 (wt.%) [25].

3. Samples3. Samples and and Analytical Analytical Methods Methods Quartz veins samples selected for this study are shown in (Table 1). In the first stage, thin Quartz veins samples selected for this study are shown in (Table1). In the ﬁrst stage, thin polished polished sections were made from these samples. To determine the phases’ transition temperatures sections were made from these samples. To determine the phases’ transition temperatures in quartz ﬂuid in quartz fluid inclusions, cryo- and thermometry methods were used (Linkam THMSG-600 heating- inclusions, cryo- and thermometry methods were used (Linkam THMSG-600 heating-freezing chamber freezing chamber (Linkam Scientific Instruments, Tadworth Surrey, United Kingdom, https://www.linkam.co.uk/) with a measurement range of −196/+600 °C). The composition of the gas phase and corresponding identification of solid phases in the inclusions were carried out by Raman spectroscopy (JobinYvon “Ramanor U-1000” spectrometer, MillenniaProS2 laser (532 nm), HORIBA JOBIN YVON detector, Novosibirsk, Russia). The total salt concentrations in fluid inclusions and their corresponding water–salt system were determined using the cryometry method [41,42]. The assessment of the pressure of mineral formation

Minerals 2020, 10, 1093 5 of 19

(Linkam Scientiﬁc Instruments, Tadworth Surrey, United Kingdom, https://www.linkam.co.uk/) with a measurement range of 196/+600 C). The composition of the gas phase and corresponding − ◦ identiﬁcation of solid phases in the inclusions were carried out by Raman spectroscopy (JobinYvon “Ramanor U-1000” spectrometer, MillenniaProS2 laser (532 nm), HORIBA JOBIN YVON detector, Novosibirsk, Russia).

Table 1. List of samples with their main characteristics

Minerals Included in Quartz or Filling Sample Texture Morphology Cracks and Cavities Fe-hydroxide, Fe-antimonite/tellurite, 3053_a Filling of cavities Segregation sulfosalts, Au-Fe(Sb,As,Te) oxide 3053_b Filling of cavities Segregation Sulfosalts, maletoyvayamite, tellurium 3058_a Interspersed Inclusions Pyrite 3058_b Interspersed Inclusions Pyrite Bismuthinite, maletoyvayamite, 3058_c Interspersed Inclusions Sb(Bi,Te,As,Se) oxide, sulfosalts Note. All samples are a vein of white quartz.

The total salt concentrations in ﬂuid inclusions and their corresponding water–salt system were determined using the cryometry method [41,42]. The assessment of the pressure of mineral formation environment was carried out using the published pressure-temperature-composition data for NaCl-H2O systems. The AqSo_NaCl [43], ISOHOR [44] and FLINCOR [45] software packages were also used to estimate the pressure of mineral formation from microthermometric data obtain in the study of ﬂuid inclusions. The chemical compositions of the minerals (samples 3053-8_a,d,c) and texture of mineral aggregates were studied at the Analytical Center for multi-elemental and isotope research of the Sobolev Institute of Geology and mineralogy Russian Academy of Sciences (SB RAS) in Novosibirsk, using a LEO-413VP scanning electron microscope (SEM) with the INCA Energy 350 microanalysis system (Oxford Instruments Ltd.) equipped with an energy dispersive spectrometer (EDS) (analysts: Dr. N. Karmanov, M. Khlestov), operated at an accelerating voltage of 20 kV, current intensity 0.4 nA, 50 sec. measuring time, and beam diameter ~1 µm. The following standards were used: pure metals (Ag, Au, Bi, Se, Sb, Fe, Cu), pyrite (S), synthetic HgTe (Te), sperrylite (As). The detection limit was 0.02%. The following X-ray lines were selected: Lα for Ag, Te, As, Sb and Se; Kα for S, Fe, Cu and O; and Mα for Au and Bi. Analytical data for the samples 3053-3 a,b was obtained at the Institute of Volcanology and Seismology of Far Eastern Branch of RAS, using a TescanVega-3 scanning electron microscope equipped with an energy dispersive spectrometer, EMF X-MAX (analyst: V.M. Chubarov), operated at an accelerating voltage of 20 kV, current intensity 3–0.7 nA, 50 sec. measuring time, and beam diameter ~1 µm. The following standards were used: pure metals (Au, Ag, Se, Sb), synthetic FeS2 (Fe), InAs (As), CdTe (Te), CuSbS2 (Sb), Bi2S3 (Bi), CuFeS2 (S, Cu). The detection limit was 0.1 wt.%. The following X-ray lines were selected: Lα for Ag, Te, As, Sb and Se; Kα for S, Fe, Cu and O; and Mα for Au and Bi.

4. Results

4.1. Mineralogy of Studied Maletoyvayam Deposit Ores The studied samples are represented by quartz veins with abundant spotty dissemination of ﬁne grain ore minerals. In some of the ore samples only pyrite is present, whereas Au minerals are completely absent. These samples are considered to be related to early pyrite-quartz assemblage (Figure3a,b). Other samples contain ﬁne dissemination of Au compounds along with other ore minerals; however, pyrite is absent or only represented as subordinate inclusions within other minerals. These samples are genetically associated to the later gold-bearing assemblage [26], which in the context of our study was named as: the maletoyvayamite-quartz association. Minerals 2020, 10, 1093 6 of 19 MineralsMinerals 20202020,, 1010,, xx FORFOR PEERPEER REVIEWREVIEW 66 ofof 1919

Figure 3.FigureFigureImpregnation 3.3. ImpregnationImpregnation of pyrite inofof quartz:pyritepyrite in irregularin ququartz:artz: (sample irregularirregular 3058-8_a) (sample(sample ( a 3058-8_a))3058-8_a) and spotted ((aa)) (andandb) from the pyrite-quartzspottedspotted association ((bb)) fromfrom (samplethethe pyrite-quartzpyrite-quartz 3058-8_b). associationassociation (sample(sample 3058-8_b).3058-8_b).

TheThe studiedstudied ore-bearingore-bearing samples samples correspond correspond to to quartz quartz veins. veins. TheThe concentrationsconcentrations ofof noblenoble metalsmetals varyvary depending depending onon thethethe dissemination disseminationdissemination density densitydensity within withinwithin the thethe ore oreore samples: samples:samples: Au AuAu from fromfrom 0.8 0.80.8 to to 147to 147147 ppm ppmppm and andand Ag AgAgfrom fromfrom 0.5 to0.50.5 200 toto ppm.200200 ppm.ppm. In Au-Ag InIn Au-AgAu-Ag enriched enrichedenriched samples samplessamples (3053-3), (3053-3),(3053-3), quartz quartzquartz contains containscontains very small veryvery quartz smallsmall druses;quartzquartz druses;druses;these cavities thesethese arecavitiescavities partially areare orpartiallypartially completely oror completelycompletely ﬁlled with afilledfilled ﬁnely withwith dispersed aa finelyfinely reddish-gray disperseddispersed mass,reddish-grayreddish-gray represented mass,mass, by representedrepresenteda mixture of ironbyby aa hydroxides, mixturemixture ofof telluritesironiron hydroxides,hydroxides, and iron antimonates,telluritestellurites andand sulfosalts ironiron antimonates,antimonates, (Figure4a), sulfosaltssulfosalts native and (Figure(Figure secondary 4a),4a), native(mustard)native andand gold secondarysecondary and other (mustard)(mustard) rare minerals gogoldld andand including otherother rarerare unique mineralsminerals compounds includingincluding of Au-sulfoselenotellurides uniqueunique compoundscompounds ofof Au-Au- and sulfoselenotelluridessulfoselenotelluridescomplex Au-bearing and oxidesand complexcomplex (Figure Au-bearingAu-bearing4b). oxidesoxides (Figure(Figure 4b).4b).

Figure 4. SEM image of sample 3053-3_a. The cavities in quartz filled with a finely dispersed mass FigureFigure 4.4. SEMSEM imageimage ofof samplesample 3053-3_a.3053-3_a. TheThe cavitiescavities inin quartzquartz filledfilled withwith aa finelyfinely disperseddispersed massmass represented by a mixture of iron hydroxides, tellurites, iron antimonates, and sulfosalts (a); and the representedrepresented byby aa mixturemixture ofof ironiron hydroxides,hydroxides, tetellurites,llurites, ironiron antimonates,antimonates, andand sulfosaltssulfosalts ((aa);); andand thethe same masses, but impregnated with complex oxides of Au (Au-Fe-Sb-Te-O compounds) (b). samesame masses,masses, butbut impregnatedimpregnated withwith complexcomplex oxidesoxides ofof AuAu (Au-Fe-Sb-Te-O(Au-Fe-Sb-Te-O compounds)compounds) ((bb).). Sulfosalts are widespread in the ore associations of the Maletoyvayam deposit. Two main SulfosaltsSulfosalts areare widespreadwidespread inin thethe oreore associationsassociations ofof thethe MaletoyvayamMaletoyvayam deposit.deposit. TwoTwo mainmain groupsgroups groups of sulfosalts were identified in the Gaching area: the tetrahedrite-group Cu12(As,Sb,Te)4S13 and ofof sulfosaltssulfosalts werewere identifiedidentified inin thethe GachingGaching area:area: thethe tetrahedrite-grouptetrahedrite-group CuCu1212(As,Sb,Te)(As,Sb,Te)44SS1313 andand enargite-group Cu3(As,Sb)S4 [33]. In the samples with highest noble metals enrichment, maletoyvayamite enargite-groupenargite-group CuCu33(As,Sb)S(As,Sb)S44 [33].[33]. InIn thethe samplessamples withwith highesthighest noblenoble metalsmetals enrichment,enrichment, occurs as independent grains intergrown with tellurium and sulfosalts. It is often found along cracks or maletoyvayamitemaletoyvayamite occursoccurs asas independentindependent grainsgrains intergintergrownrown withwith telluriumtellurium andand sulfosalts.sulfosalts. ItIt isis oftenoften in the intergranular space of quartz (Figure5a), or confined to the margins of large grains of sulfosalts foundfound alongalong crackscracks oror inin thethe intergranularintergranular spacespace ofof quartzquartz (Figure(Figure 5a),5a), oror confinedconfined toto thethe marginsmargins ofof (Figure5b). largelarge grainsgrains ofof sulfosaltssulfosalts (Figure(Figure 5b).5b). Au-bearing minerals range in size from a few µm to 80 µm, while sulfosalt grains reach up to Au-bearingAu-bearing mineralsminerals rangerange inin sizesize fromfrom aa fewfew µmµm toto 8080 µm,µm, whilewhile sulfosaltsulfosalt grainsgrains reachreach upup toto 2.5 mm. The sulfosalts are enriched in Se within a range of 5.84–10.42 wt.%. The substitution of Se 2.52.5 mm.mm. TheThe sulfosaltssulfosalts areare enrichedenriched inin SeSe withinwithin aa rangerange ofof 5.84–10.425.84–10.42 wt.%.wt.%. TheThe substitutionsubstitution ofof SeSe forfor for S is ubiquitous (Table2). The presence of selenium in sulfosalts indicates specific conditions for SS isis ubiquitousubiquitous (Table(Table 2).2). TheThe presencepresence ofof seleniumselenium inin sulfosaltssulfosalts indicatesindicates specificspecific conditionsconditions forfor theirtheir their formation. formation.formation. AnotherAnother samplesample (3053-8_a,d,c)(3053-8_a,d,c) containingcontaining thethe maletoyvayamite-quartzmaletoyvayamite-quartz oreore associationassociation withwith concentrationsconcentrations ofof AuAu andand AgAg 1.41.4 andand 12.312.3 ppm,ppm, resprespectively,ectively, containscontains largelarge bismuthinitebismuthinite inclusions.inclusions.

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In addition,Table 2. Compositions sulfosalts of of various ore minerals compositions shown in Figure (tetrahedrite,5 from the maletoyvayamite-quartz.goldfieldite, enargite, associationetc.), which are described(sample in 3053-3), [33], are wt.%. also found in association with bismuthinite (Figure 6a,c,d). Bismuthinite has an unusualNo Scomposition, Cu As since SeSb and Sb Te in Teits struct Auure Totalare substituted for Bi, Formulawhereas Se and Te for S

(Figure1 21.49 6a,b; Table 42.37 3). Furthermore, 5.84 8.46 it was 20.75 found that 99.28 bismuthinite Cu11.82 has(Te 2.86anSb S/Se1.22)4.08 =(S 211.80 ratio.Se1.30 )Moreover,13.10 2 21.43 40.28 2.30 8.76 6.40 21.38 100.56 Cu11.05(Te2.92Sb0.92 As0.54)4.38(S11.65 Se1.93)13.58 we suggest the possibility of this mineral phase corresponding to a potentially new mineral Bi2S2Se. 3 6.34 6.24 50.5 37.80 100.88 Au2.89Te5.95(S2.97Se1.19)4.16 This4 phase 6.35 has also been reported 5.60 from 50.47the HS-IS 37.76 epithermal 100.19 Perama AuHill2.91 Tedeposits,6.00(S3.01Se1.08 in) 4.09Greece [46]. It 5 3.38 11.03 49.89 36.16 100.46 Au2.91Te6.20(Se2.22S1.67)3.89 is intergrown6 with the Se-bearing 6.97 tellurium 92.99 (Figure 6c). 99.95 Complex oxides of Te various0.89Se0.11 oxidation states in 7primary 25.81 minerals, 42.65 6.15 including 7.50 maletoyvayamite, 17.88 0.73 are100.72 common Cu in4.09 the(Sb0.89 MaletoyvayamAs0.50 Se0.48Te0.04)1.91 deposit(S4.90Se0.10 )[26,31].5.00 8 20.59 42.59 1.02 7.74 12.34 15.75 100.03 Cu11.79(Te2.17 Sb1.78As0.24)4.19(S11.30Se1.73)13.02 In 9the analyzed sample, bismuthinite 32.8 and 66.68 similar phases 99.49 are replaced by oxides Te0.56Se of0.44 Sb, Bi, As, Te and Se10 in variable 2.95 proportions; 12.15 Fe, Cu and occasional 48.75 36.40ly Ag 100.26 are minor elements. Au2.96Te6.11 The(Se2.46 oxidationS1.47)3.93 state also 11 19.71 40.94 9.99 8.85 20.00 99.49 Cu11.57(Te2.82Sb1.31)4.13(S11.04Se2.27)13.31 varies12 26.94in these 45.54 compound 16.52 10.42s from 2.34 (Sb,Bi,Te,As,Se) 101.760.31O0.69 to (Sb,Bi,Te,As,Se) Cu2.97(As0.91Sb0.08)0.990.24(S3.49OSe0.760.55 )(Figure4.04 7)

dependingNote. 1,2,8,11—goldﬁeldite mainly on the Cuoxygen12(Te,Sb) fugacity:4(S,Se)13; 3,4—S-richlog fO2 ranging analogue offrom maletoyvayamite −29.8 to −27.3; Au3Te values6(S,Se)4 ;previously 5,10— calculatedmaletoyvayamite for the ore-bearing Au3Te6(Se,S)4; 6,9—tellurium;mineral association 7—watanabeite [26]. Cu4(Sb,As)2(S,Se)5; 12—enargite Cu3(As,Sb)(S,Se)4.

FigureFigure 5. 5. SEMSEM image. image. The The maletoyvayam maletoyvayamite-quartzite-quartz association association in in the the sample 3053-3_b, highest enrichmentenrichment in in noble noble metals metals (A (Auu is is 144 144 ppm, ppm, Ag Ag is is 200 200 ppm); ppm); ( (aa)) ore ore minerals localized along cracks in thethe intergranular intergranular space space of of quartz; quartz; (b ()b maletoyvayamite) maletoyvayamite confined conﬁned to tothe the margins margins of ofsulfosalts sulfosalts grains; grains;

mlt—maletoyvayamite,mlt—maletoyvayamite, gdf—goldfieldite, gdf—goldﬁeldite, wtb—watanabeite, Te0.90.9SeSe0.10.1—Te-Se—Te-Se solid solid solution. Points withwith numbers numbers correspond correspond to to the the analysis analysis numbers numbers in in Table Table 22..

AnotherTable 2. sampleCompositions (3053-8_a,d,c) of ore minerals containing shown the in maletoyvayamite-quartz Figure 5 from the maletoyvayamite-quartz. ore association with concentrationsassociation of(sample Au and 3053-3), Ag 1.4 wt.%. and 12.3 ppm, respectively, contains large bismuthinite inclusions. In addition, sulfosalts of various compositions (tetrahedrite, goldﬁeldite, enargite, etc.), which are No S Cu As Se Sb Te Au Total Formula described in [33], are also found in association with bismuthinite (Figure6a,c,d). Bismuthinite has an 1 21.49 42.37 5.84 8.46 20.75 99.28 Cu11.82(Te2.86 Sb1.22)4.08(S11.80Se1.30)13.10 unusual2 21.43 composition, 40.28 2.30 since 8.76 Sb and 6.40 Te in its21.38 structure are100.56 substituted Cu11.05 for(Te2.92 Bi,Sb whereas0.92 As0.54)4.38 Se(S11.65 and Se Te1.93)13.58 for S (Figure3 66.34a,b; Table 3). Furthermore, 6.24 it was50.5 found 37.80 that bismuthinite100.88 has anAu S2.89/TeSe5.95=(S22.97 ratio.Se1.19)4.16 Moreover, we4 suggest 6.35 the possibility of5.60 this mineral 50.47 phase corresponding37.76 100.19 to a potentiallyAu2.91Te6.00 new(S3.01 mineralSe1.08)4.09 Bi2S2Se. This5 phase3.38 has also been reported11.03 from the49.89 HS-IS 36.16 epithermal 100.46 Perama HillAu2.91 deposits,Te6.20(Se2.22S in1.67) Greece3.89 [46]. 6 6.97 92.99 99.95 Te0.89Se0.11 It is intergrown with the Se-bearing tellurium (Figure6c). Complex oxides of various oxidation states 7 25.81 42.65 6.15 7.50 17.88 0.73 100.72 Cu4.09(Sb0.89As0.50 Se0.48Te0.04)1.91(S4.90Se0.10)5.00 in primary minerals, including maletoyvayamite, are common in the Maletoyvayam deposit [26,31]. 8 20.59 42.59 1.02 7.74 12.34 15.75 100.03 Cu11.79(Te2.17 Sb1.78As0.24)4.19(S11.30Se1.73)13.02 In the9 analyzed sample, bismuthinite32.8 and similar66.68 phases are99.49 replaced by oxidesTe of0.56 Sb,Se0.44 Bi, As, Te and Se in10 variable 2.95 proportions; Fe, Cu12.15 and occasionally 48.75 Ag36.40 are minor100.26 elements. TheAu2.96 oxidationTe6.11(Se2.46 stateS1.47)3.93 also varies in11 these 19.71 compounds 40.94 from (Sb,Bi,Te,As,Se)9.99 8.85 20.000.31O 0.69 to (Sb,Bi,Te,As,Se)99.49 Cu0.2411.57(TeO0.762.82Sb(Figure1.31)4.13(S11.047)Se depending2.27)13.31 mainly12 26.94 on the 45.54 oxygen 16.52 fugacity: 10.42 log 2.34f O ranging from 29.8101.76 to 27.3;Cu values2.97(As previously0.91Sb0.08)0.99(S3.49 calculatedSe0.55)4.04 for 2 − − the ore-bearingNote. 1,2,8,11—goldfieldite mineral association Cu [2612(Te,Sb)]. 4(S,Se)13; 3,4—S-rich analogue of maletoyvayamite Au3Te6(S,Se)4; 5,10—maletoyvayamite Au3Te6(Se,S)4; 6,9—tellurium; 7—watanabeite

Cu4(Sb,As)2(S,Se)5; 12—enargite Cu3(As,Sb)(S,Se)4

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FigureFigure 6. SEM 6. SEM image. image. The Themaletoyvayamite-qu maletoyvayamite-quartzartz association association in the in thesample sample 3053-8-c 3053-8-c (Au (Au is 1.37 is 1.37 ppm ppm and Ag is 12.3and Agppm): is 12.3 (a) ppm): Sb,Te,Se-bearing (a) Sb,Te,Se-bearing bismuthinite bismuthinite (bsm) (bsm)replaced replaced by (Sb,Bi,Te)-o by (Sb,Bi,Te)-oxidexide in inintergrowths intergrowths with with enargite (eng) hosted in quartz; (b) bismuthinite replaced by (Sb,Bi,Te)-oxide; (c) unnamed phase enargite (eng) hosted in quartz; (b) bismuthinite replaced by (Sb,Bi,Te)-oxide; (c) unnamed phase Bi2S2Se with Bi S Se with inclusions of Se-rich tellurium (Te Se ) replaced by (Sb,Bi,Te)-oxide, in intergrowth with inclusions2 2 of Se-rich tellurium (Te0.7Se0.3) replaced0.7 by0.3 (Sb,Bi,Te)-oxide, in intergrowth with tetrahedrite (ttr) andtetrahedrite goldfieldite (ttr) (gfd); and (d goldﬁeldite) inclusions (gfd);of maletoyvayamite (d) inclusions of (mlt) maletoyvayamite and enargite in (mlt) quartz; and ( enargitee) maletoyvayamite in quartz; in (e) maletoyvayamite in intergrowths with (Sb,Se,Te,As)-oxide; (f) grain of (Sb,Bi,As)-oxide containing intergrowths with (Sb,Se,Te,As)-oxide; (f) grain of (Sb,Bi,As)-oxide containing the naumannite (Ag2Se) the naumannite (Ag Se) inclusions in quartz. Points with numbers correspond to the analysis numbers inclusions in quartz. Points2 with numbers correspond to the analysis numbers in Table 3. in Table3.

Table 3.3.Compositions Compositions of oreof mineralsore minerals shown shown in Figure in 6 Figurefrom the 6 maletoyvayamite-quartz.from the maletoyvayamite-quartz. association (sampleassociation 3053-8_c), (sample wt.%. 3053-8_c), wt.%. No Tota No.Au Au CuCu AgAg Bi Bi SbSb Te Te As As Se Se S Total S FormulaFormula . l 1 62.41 8.46 2.89 10.89 14.16 98.81 (Bi1.54Sb0.36Te0.12)2.01(S2.28Se0.71)2.99 2 65.0762.45.198.4 3.20 11.36 13.4510.8 98.2714.1 98.8 (Bi1.65Sb(Bi0.231.54TeSb0.130.36)2.01Te(S0.122.23)Se2.010.76(S)2.282.99Se0.71)2. 1 3 72.54 2.89 14.13 11.34 98.01 Bi S Se 1 6 9 6 1 1.97 2.01 1.0299 4 47.11 2.86 15.93 1.07 31.32 98.29 Cu3.01(As0.86Sb0.10)0.96(S3.97Se0.06)4.03 65.0 5.1 11.3 13.4 98.2 (Bi1.65Sb0.23Te0.13)2.01(S2.23Se0.76)2. 2 5 35.10 47.38 3.20 14.80 2.03 99.31 Au2.89Te6.03(Se3.04S1.03)4.07 6 55.877 9 47.07 14.67 2.146 99.755 7 Au2.95Te5.97(Se3.01S1.0899 )4.09 7 71.84 72.5 26.4914.1 98.3311.3 98.0 Ag2.00Se1.00 3 Bi1.97S2.01Se1.02 Note. 1,2—Sb,Te,Se-bearing bismuthinite4 (Bi,Sb,Te)2(S,Se)3, 3—unnamed3 4 phase,1 4 enargite, 5,6—maletoyvayamite, 7—naumannite. Minerals 2020, 10,47.1 x FOR PEER REVIEW 2.8 15.9 31.3 98.2 Cu3.01(As0.86Sb0.10)0.96(S3.979Se of0.06 19 4 1.07 1 6 3 2 9 )4.03 35.1 47.3 14.8 99.3 5 2.03 Au2.89Te6.03(Se3.04S1.03)4.07 0 8 0 1 55.8 47.0 14.6 99.7 6 2.14 Au2.95Te5.97(Se3.01S1.08)4.09 7 7 7 5 71.8 26.4 98.3 7 Ag2.00Se1.00 4 9 3

Note. 1,2 – Sb,Te,Se-bearing bismuthinite (Bi,Sb,Te)2(S,Se)3, 3 – unnamed phase, 4 enargite, 5,6 – maletoyvayamite, 7 – naumannite.

FigureFigure 7.7. OxygenOxygen versus versus the the sum sum of of the rest atoms in complex oxides (iron tellurites and ironiron antimonates)antimonates) showing the variations in their compositioncomposition due to the degree of oxidationoxidation ofof thethe primaryprimary phases.phases.

4.2. Quartz Generations and Corresponding Types of Fluid Inclusions The ore-bearing samples selected to study of fluid inclusions are represented by two main associations: pyrite-quartz and maletoyvayamite-quartz.

4.2.1. Pyrite-Quartz Association In the studied samples showing this mineral association, there are at least three successively crystallized generations of quartz (Figure 8a). The earliest generation is represented by a grayish to dark gray fine-grained quartz aggregate with abundant dissemination of fine pyrite grains. Subsequent generations of quartz are represented by veins that cut the early pyrite-bearing quartz. In late veinlets, crustified, microdruse, cockade and, less often, collomorphic textures can be observed (Figure 8a). These textures are also representative of mineral associations in other gold-bearing low sulfidation epithermal deposits in the Kamchatka Peninsula [19]. Late quartz veins also contain sporadic pyrite, but very rarely. Separate large grains of quartz in late veinlets are characterized by a zonal structure. The central parts of quartz grains contain single two-phase inclusions with isometric shape (Figure 9b). Growth zones on the periphery of quartz crystals are traced by abundant fluid inclusions with oval vacuoles, elongated perpendicular to the faces of quartz crystals (Figure 9c).

Figure 8. Quartz generations. (a) pyrite-quartz mineral association: Early quartz (Q1) is presented in association with abundant pyrite grains (black spots) and intersected by veins of quartz (Q2−4), containing rare pyrite inclusions; (b) maletoyvayamite-quartz mineral association: In this sample, early quartz (Q1) contains inclusions of bismuthinite and maletoyvayamite. This quartz generation is intersected by late quartz veins (Q2−4).

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Minerals 2020, 10, 1093 9 of 19 Figure 7. Oxygen versus the sum of the rest atoms in complex oxides (iron tellurites and iron antimonates) showing the variations in their composition due to the degree of oxidation of the 4.2. Quartzprimary Generations phases. and Corresponding Types of Fluid Inclusions

The4.2. Quartz ore-bearing Generations samples and Correspon selectedding to Types study of Fluid of ﬂuid Inclusions inclusions are represented by two main associations: pyrite-quartz and maletoyvayamite-quartz. The ore-bearing samples selected to study of fluid inclusions are represented by two main 4.2.1.associations: Pyrite-Quartz pyrite-quartz Association and maletoyvayamite-quartz.

In4.2.1. the Pyrite-Quartz studied samples Association showing this mineral association, there are at least three successively crystallized generations of quartz (Figure8a). The earliest generation is represented by a grayish to In the studied samples showing this mineral association, there are at least three successively darkcrystallized gray fine-grained generations quartz of aggregatequartz (Figure with 8a). abundant The earliest dissemination generation is of represented fine pyrite grains.by a grayish Subsequent to generationsdark gray of quartzfine-grained are represented quartz aggregate by veins with that cutabundant the early dissemination pyrite-bearing of fine quartz. pyrite In lategrains. veinlets, crustified,Subsequent microdruse, generations cockade of quartz and, are less represented often, collomorphic by veins that texturescut the early can pyrite-bearing be observed quartz. (Figure 8a). TheseIn textures late veinlets, are crustified, also representative microdruse, of cockade mineral and, associations less often, collomorphic in other gold-bearing textures can be low observed sulfidation epithermal(Figure deposits8a). These in textures the Kamchatka are also representative Peninsula [19 of]. mineral Late quartz associations veins in also other contain gold-bearing sporadic low pyrite, but verysulfidation rarely. epithermal Separate largedeposits grains in the of quartzKamchatka in late Peninsula veinlets [19]. are characterizedLate quartz veins by aalso zonal contain structure. The centralsporadic parts pyrite, of quartzbut very grains rarely. contain Separate single large grains two-phase of quartz inclusions in late veinlets with isometric are characterized shape (Figure by a 9b). zonal structure. The central parts of quartz grains contain single two-phase inclusions with isometric Growth zones on the periphery of quartz crystals are traced by abundant fluid inclusions with oval shape (Figure 9b). Growth zones on the periphery of quartz crystals are traced by abundant fluid vacuoles,inclusions elongated with oval perpendicular vacuoles, elongated to thefaces perpendicu of quartzlar to crystals the faces (Figure of quartz9c). crystals (Figure 9c).

Figure 8. 8. QuartzQuartz generations. generations. (a) pyrite-quartz (a) pyrite-quartz mineral mineral association: association: Early quartz Early (Q1) quartzis presented (Q1) in is association presented with abundant pyrite grains (black spots) and intersected by veins of quartz (Q2−4), containing rare pyrite2 4 in association with abundant pyrite grains (black spots) and intersected by veins of quartz (Q − ), 1 containinginclusions; (b rare) maletoyvayamite-quartz pyrite inclusions; ( bmineral) maletoyvayamite-quartz association: In this sample, mineral early quartz association: (Q ) contains In this inclusions sample, of bismuthinite and maletoyvayamite. This quartz generation is intersected by late quartz veins (Q2−4). early quartz (Q1) contains inclusions of bismuthinite and maletoyvayamite. This quartz generation is 2 4 intersectedMinerals 2020, by10, latex FOR quartz PEER REVIEW veins (Q − ). 10 of 19

Figure 9. (Figurea) quartz 9. (a exhibiting) quartz exhibiting zoning patternzoning pattern with crustiﬁed with crustified texture texture from afrom pyrite-quartz a pyrite- association; quartz association; (b) a group of isolated two-phase inclusions in the center part of (b) a group of isolated two-phase inclusions in the center part of the quartz crystal, (c) two-phase the quartz crystal, (c) two-phase inclusions with elongated shape trace the growth zone inclusions with elongated shape trace the growth zone at the periphery of the quartz crystal. at the periphery of the quartz crystal.

Crystallization of some quartz generations with different textures occurred close in time or almost simultaneously, since smooth transitions are often observed among them. It is likely that several hydrothermal pulses at very short time intervals were consistently segregated during the formation of ores. Thus, different quartz generations represent the observed textural varieties as a result of these rhythmic pulses. On this subject, when presenting the results on fluid inclusions, showed by textural features, we will divide the quartz in the pyrite-quartz association into only two generations—the early fine-grained generation with abundant dissemination of pyrite and the late one, represented by veinlets cutting the first one.

4.2.2. Maletoyvayamite–Quartz Association Quartz associated with this mineral assemblage is similar to those of the pyrite-quartz association in respect to the textural and structural features, as well as in the distribution of fluid inclusions. Quartz displaying crustified texture also contain inclusions of ore minerals. Pyrite in the studied sample is represented by single small crystals whereas Au minerals (maletoyvayamite) are the most abundant (Figure 6 d,e); among Ag minerals, naumannite Ag2Se and hessite Ag2Te occur in association (Figure 6f). The quartz of the maletoyvayamite-quartz association, as in the pyrite-quartz association, also contains two types of fluid inclusions (Figure 10a,b) with the characteristic that they belong to the primary phase, and less often to the pseudo-secondary phase according to [47,48]. The first type is represented by two-phase inclusions close to isometric, containing a gas bubble and liquid in vol. ratios 1/10–1/12, which does not exceed 10 µm in size (Figure 10c). The second type is represented by two-phases, which are close to the faces of the quartz crystal and delimitate its growth zones. They have an elongated or tubular shape of up to 30 µm in length and 5–10 µm in cross-section (Figure 10d), and as a rule, they are associated with single-phase vapor inclusions, also elongated with channel-shaped, of up to 50 µm in length.

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Crystallization of some quartz generations with different textures occurred close in time or almost simultaneously, since smooth transitions are often observed among them. It is likely that several hydrothermal pulses at very short time intervals were consistently segregated during the formation of ores. Thus, different quartz generations represent the observed textural varieties as a result of these rhythmic pulses. On this subject, when presenting the results on fluid inclusions, showed by textural features, we will divide the quartz in the pyrite-quartz association into only two generations—the early fine-grained generation with abundant dissemination of pyrite and the late one, represented by veinlets cutting the first one.

4.2.2. Maletoyvayamite–Quartz Association Quartz associated with this mineral assemblage is similar to those of the pyrite-quartz association in respect to the textural and structural features, as well as in the distribution of fluid inclusions. Quartz displaying crustified texture also contain inclusions of ore minerals. Pyrite in the studied sample is represented by single small crystals whereas Au minerals (maletoyvayamite) are the most abundant (Figure6 d,e); among Ag minerals, naumannite Ag 2Se and hessite Ag2Te occur in association (Figure6f). The quartz of the maletoyvayamite-quartz association, as in the pyrite-quartz association, also contains two types of fluid inclusions (Figure 10a,b) with the characteristic that they belong to the primary phase, and less often to the pseudo-secondary phase according to [47,48]. The first type is represented by two-phase inclusions close to isometric, containing a gas bubble and liquid in vol. ratios 1/10–1/12, which does not exceed 10 µm in size (Figure 10c). The second type is represented by two-phases, which are close to the faces of the quartz crystal and delimitate its growth zones. They have an elongated or tubular shape of up to 30 µm in length and 5–10 µm in cross-section (Figure 10d), and as a rule, they are associated with single-phase vapor inclusions, also elongated with channel-shaped, of up to 50 µm in length. Minerals 2020, 10, x FOR PEER REVIEW 11 of 19

FigureFigure 10. ( a10.) quartz (a) quartz exhibiting exhibiting zonation zonation texture texture from from a maletoyvayamite-quartz a maletoyvayamite-quartz association; association; (b ()b group) group of isolated fluid inclusions in the central part of the quartz crystal and elongated shape of of isolated ﬂuid inclusions in the central part of the quartz crystal and elongated shape of inclusions at inclusions at the periphery of the crystal; close-up showing the representative shape and details of the periphery of the crystal; close-up showing the representative shape and details of the inclusions in the inclusions in the center of quartz crystals (c) and in the growth zones (d). the center of quartz crystals (c) and in the growth zones (d). The origin of elongated fluid inclusions is related with the repulsion of mineral particles by the growing face of the crystal, or with the processes of dissolution of quartz and subsequent healing of the formed tunnel-like hollows [47]. The presence of single-phase vapor inclusions seems to be due to boiling processes of the mineral-forming fluid. Judging by the significant elongation of the vacuoles of fluid inclusions located perpendicular to the faces of the quartz crystal, the boiling process is suggested to be quite long [47].

4.3. Results of the Fluid Inclusions Microthermometry The results of fluid inclusions study from different types of quartz veins associations make it possible to characterize the main physicochemical parameters related to their formation. Table 4 summarizes these main parameters for two types of quartz from the different associations discussed before.

4.3.1. Pyrite-Quartz Association Two-phase water–salt inclusions from early quartz are homogenized at temperatures ranging from 290 to 260 °C. Ice is formed in these inclusion solutions when they are cooled, and melts again when heated at a temperature range from −2 to −0.4 °C. The first melting of ice is observed in a temperature range from −38 to −35 °C, although intense, ice melting and the appearance of liquid in is recorded in the range from −26 to −23 °C. In small inclusions, the first melting is distinguished in the same temperature interval (from −26 to −23 °C), which is close to the melting temperature of the eutectic NaCl + KCl + H2O water–salt system (−23.5 °C). This may indicate that the main salt components in the inclusions are probably NaCl and KCl with a diminutive admixture of other soluble salts, which somewhat lower the eutectic of the solutions. One of such impurities may correspond to K2CO3, since the melting temperatures of eutectics in the water–salt systems Na2CO3 +

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The origin of elongated fluid inclusions is related with the repulsion of mineral particles by the growing face of the crystal, or with the processes of dissolution of quartz and subsequent healing of the formed tunnel-like hollows [47]. The presence of single-phase vapor inclusions seems to be due to boiling processes of the mineral-forming fluid. Judging by the significant elongation of the vacuoles of fluid inclusions located perpendicular to the faces of the quartz crystal, the boiling process is suggested to be quite long [47].

4.3. Results of the Fluid Inclusions Microthermometry The results of fluid inclusions study from different types of quartz veins associations make it possible to characterize the main physicochemical parameters related to their formation. Table4 summarizes these main parameters for two types of quartz from the different associations discussed before.

Table 4. Results of ﬂuid inclusions microthermometry in quartz from early and late generations.

T C Total Quartz ◦ T C NaCl, KCl, Pressure **, Homogenization, T C Eutectic ◦ Salinity, Generation ◦ Ice Melting wt.% wt.% Bar (n *) wt.% Pyrite-Quartz Association 290–288 (5) 25 ( 38– 35) 0.5– 0.4 0.6 0.3 0.9 70–68 − − − − − 270–260 (6) 24– 23 0.6– 0.4 0.6 0.3 0.9 50–43 − − − − Early (Q1) 295 (2) 25 ( 38– 35) 0.5– 0.4 0.6 0.3 0.9 76 − − − − 245 (4) 24.5 0.5 0.6 0.3 0.9 32 − − 264–268 (3) 26– 25 2 2.5 0.8 3.3 49 − − − Late 260–240 (4) 38 0.1 0.1 0.1 0.2 43 − − (Q2–4) 200 (2) 38– 35 0.1 0.1 0.1 0.2 13 − − − Maletoyvayamite-Quartz Association 255–245 (4) 38– 35 2.5– 2 3.3 1.0 4.3 39–32 Early (Q1) − − − − 250–245 (2) 38– 35 2.4– 2.2 3.3 1.0 4.3 36–32 − − − − Late 228–210 (6) 38 0.7– 0.5 1.0 0.5 1.5 23–16 − − − (Q2–4) 220–135 (3) 38 0.6– 0.3 0.9 0.3 1.2 20–4 − − − Note. * Number of inclusions; ** pressure value calculated for the concentration of solutions (wt.%) to NaCl eq.

4.3.1. Pyrite-Quartz Association Two-phase water–salt inclusions from early quartz are homogenized at temperatures ranging from 290 to 260 ◦C. Ice is formed in these inclusion solutions when they are cooled, and melts again when heated at a temperature range from 2 to 0.4 C. The first melting of ice is observed in a − − ◦ temperature range from 38 to 35 C, although intense, ice melting and the appearance of liquid − − ◦ in is recorded in the range from 26 to 23 C. In small inclusions, the first melting is distinguished − − ◦ in the same temperature interval (from 26 to 23 C), which is close to the melting temperature of − − ◦ the eutectic NaCl + KCl + H O water–salt system ( 23.5 C). This may indicate that the main salt 2 − ◦ components in the inclusions are probably NaCl and KCl with a diminutive admixture of other soluble salts, which somewhat lower the eutectic of the solutions. One of such impurities may correspond to K2CO3, since the melting temperatures of eutectics in the water–salt systems Na2CO3 + K2CO3 + H O and K CO + H O correspond to 37 and 36.4 C[48], that also coincides with a temperature 2 2 3 2 − − ◦ interval of the ice first melting in large inclusions 38–35 C. − ◦ According to the method used by Borisenko [41] it was revealed that the concentrations of Na and K chlorides prevailing in the composition of solutions in the inclusions are estimated as 2.5–0.1 wt.% NaCl and 0.8–0.1 wt.% KCl, however, the presence of Fe and Mg chlorides in the composition of the inclusions is unlikely. Mg compounds are not typical for the studied mineral associations. FeCl2 and FeCl3 in water–salt systems would cause a metastable state, which also would involve incomplete crystallization of the cooled solution and, as a consequence, a decrease in the melting point of the eutectic [49,50], which was not observed in our studies. Minerals 2020, 10, 1093 12 of 19

Cryometric study of individual vapor inclusions and the gas component of water–salt inclusions did not reveal the presence of a dense gas phase. The cooling down to 190 C did not result in any − ◦ gases’ liquefaction or crystallization. The absence of a dense gas phase is also conﬁrmed by the study of ﬂuid inclusions with Raman spectroscopy. Raman spectra of the gas phase of inclusions do not contain bands characteristic of CO2,N2, and CH4 [51]. The pressure values were calculated for the concentration of solutions (wt.%) equivalent to NaCl. These values decrease from early generations of quartz to later ones and are in the range of 70–13 bar for the pyrite-quartz association.

4.3.2. Maletoyvayamite-Quartz Association Two-phase inclusions in the early quartz of the maletoyvayamite-quartz association were homogenized in a temperature range from 255 to 245 ◦C. Ice is formed in cooled solutions of two-phase inclusions, which then is melted at temperatures ranging from 2.5 to 2 C. The beginning − − ◦ of ice melting in cooled solutions occur in the range from 38 to 35 C. Fluid inclusions in late quartz − − ◦ from veinlets were homogenized in a temperature range from 225 to 135 ◦C (Table4). The rate of ice melting in cooled inclusions increases sharply at temperatures above 23 C, − ◦ and lastly ice melts in a temperature range from 0.7 to 0.3 C. The temperature ranges for the initial − − ◦ melting point of cooled solutions in the inclusions are close to the melting temperature of the eutectic of the water–salt systems Na CO + K CO + H O and K CO + H O: 37 C and 36.4 C, respectively. 2 3 2 3 2 2 3 2 − ◦ − ◦ A quick acceleration of ice melting in cooled solutions at a temperature of 23 C suggests the presence − ◦ of NaCl and KCl solutions along with Na2CO3 and K2CO3 as part of the composition. The water–salt inclusions of the ore-bearing minerals from the maletoyvayamite-quartz association are more saturated in salts in comparison with the inclusions from the pyrite-quartz association (Table4). Salt concentrations were calculated by the method of Borisenko [41], reaching NaCl = 3.3 and 1.0, and KCl = 1.0 and 0.5 (wt.%) in early quartz and late quartz, respectively. These values decrease from earlyMinerals generations 2020, 10, x FOR of quartzPEER REVIEW to later ones and are in the range of 39–4 bar for the maletoyvayamite-quartz13 of 19 association (Table4, Figure 10). 5. Discussion 5. Discussion The results obtained from fluid inclusions microthermometry in vein quartz of the MaletoyvayamThe results obtaineddeposit (Gaching from ﬂuid area) inclusions indicate microthermometry that the quartz in was vein formed quartz ofin the a wide Maletoyvayam range of deposittemperatures (Gaching from area) nearly indicate 300 thatto 180 the °C quartz and even was formed below. inIn a the wide same range way, of temperatures the pressure fromalso nearlyvaries 300from to 80 180 to ◦10C andbar (average). even below. At Inhigh the temperatures same way, the (295–255 pressure °C) also and varies pressures from 80(50–75 to 10 bar),bar (average). pyrite is Atthe high main temperatures ore mineral (295–255 (pyrite-quartz◦C) and association) pressures (50–75 (Figure bar), 11a), pyrite while is the maletoyvayamite, main ore mineral bismuthinite, (pyrite-quartz association)Cu-sulfosalts, (Figure etc. occurred 11a), while in a maletoyvayamite, rather narrow rang bismuthinite,e of temperatures Cu-sulfosalts, and pressures etc. occurred (245–255 in a°C rather and narrow32–39 bar) range (Figure of temperatures 12). and pressures (245–255 ◦C and 32–39 bar) (Figure 12).

Figure 11.11.( a()a Diagrams) Diagrams of pressureof pressure versus versus temperature temperature and (b )and salinity (b) ofsalinity NaCl eq. of versus NaCl temperatureeq. versus ontemperature the basis ofon the the microthermometry basis of the microthermometry study of the distudyﬀerent of quartzthe different generations. quartz generations.

Both of the diagrams in (Figure 11) display a gradual change between the mineral associations, moving from pyrite-quartz to maletoyvayamite-quartz; the late quartz generation of the first association coincides with the early quartz generation of the second association in P-T parameters (Figure 11a); however, they do differ in salt content (Figure 11b). For instance, the salinity percentage in fluid inclusions of the productive gold-bearing association (maletoyvayamite-quartz) is considerably bigger (3.3 versus 0.6). Sulfosalts are an important indicator of mineral formation conditions in hydrothermal deposits of various types [52–54]. Enargite in particular is a formation conditions indicator of HS type epithermal deposits [2]. This mineral has been found in ores of well-known HS epithermal deposits: Goldfield (Nevada, USA), Red Mountain, Lake City II and Summitville (Colorado, USA), Julcani (Peru) [2,55,56] and others. It is also common among the sulfosalts described at Maletoyvayam [33], and, in particular, in the studied samples (Figure 5). Enargite-bearing epithermal deposits develop when fluid rapidly rises to higher levels of the earth’s crust without interacting with groundwater. Then, its gradual cooling and partial neutralization due to its reaction with the host rocks leads to the formation of a pyrite–enargite association, including alunite and barite [57]. Earlier, we made the assumption that pyrite formation and maletoyvayamite are divergent in time based on the fact that they have never been encountered in equilibrium intergrowths [26]. Indeed, the microthermometry study on fluid inclusions in quartz confirmed this hypothesis: the most abundant dissemination of pyrite grains occur in the earliest generations of the fine-grained quartz aggregate (Figure 8a), with temperatures that correspond to a range of 295–245 °C, whereas the Au minerals, sulfosalts and other associated minerals of the main ore stage crystallized at 255– 245 °C (Table 3, Figures 10, 12). Moreover, pyrite crystallization precedes enargite in many HS-type epithermal deposits [58].

Minerals 2020, 10, 1093 13 of 19 Minerals 2020, 10, x FOR PEER REVIEW 14 of 19

FigureFigure 12. 12.Paragenetic Paragenetic diagram diagram showing showing the the stages stages of mineral of mineral formation. formation. The thick The linethick – mainline – mineral, main linemineral, - less commonline - less mineral,common dottedminera linel, dotted – rare line mineral. – rare mineral.

BothThe offluid the inclusions diagrams indata (Figure for HS 11) epithermal display a gradual deposits change (Table between 5) indicate the mineralthat ore associations,deposition movingoccurred from mainly pyrite-quartz at temperatures to maletoyvayamite-quartz; similar to the LS and the IS late types. quartz For generation example, ofthe the homogenization first association coincidestemperatures with of the primary early quartz inclusions generation in quartz of from the second the Aginskoye association deposit in P-T (LS parameters type) were (Figure230–280 11 °C,a); however,with the theyore phase do di ffbeinger in in salt the content range (Figureof 250–260 11b). °C For[59]. instance, Similar thetemperat salinityure percentageranges have in been fluid inclusionsestablished of theboth productive for the LS gold-bearing type deposits association (Rodnikovoye (maletoyvayamite-quartz) and Asachinskoye in is considerablySouth Kamchatka, bigger (3.3Russia) versus [19,21,60,] 0.6). and in regard to the IS type deposit (Cheshmeh Hafez, Iran) [61], the homogenizationSulfosalts are temperatures an important of indicator the primary of mineral inclusions formation are in conditionsthe range of in 140–280 hydrothermal °C with deposits peaks at of variousaround types 180–250 [52 –°C.54 ].This Enargite is also incompatible particular with is a al formationl HS type conditions deposits, and indicator with the of obtained HS type epithermalformation depositsparameters [2]. of This the mineral Maletoyvayam has been deposit found (Table in ores 5). of well-known HS epithermal deposits: Goldfield (Nevada,The USA),salinity Red of Mountain,ore-forming Lake solutions City II differs and Summitville both between (Colorado, the deposit USA), types Julcani (LS (Peru) and HS) [2,55 and,56 ] andeven others. within It the is also same common type (Table among 5). the The sulfosalts salinity describedrange can atbe Maletoyvayamstrongly influenced [33], and,on one in particular,hand by the mixing with meteoric water (dilution), or, on the other hand, by boil-off (concentrating) [57,62]. in the studied samples (Figure5). Enargite-bearing epithermal deposits develop when fluid rapidly Fluid inclusions with high salinity reflect the fluid history after crystallization of underlying magmas rises to higher levels of the earth’s crust without interacting with groundwater. Then, its gradual [63,64]. The strongly acidic hot fluids interaction with host rocks typically dissolve the surrounding cooling and partial neutralization due to its reaction with the host rocks leads to the formation of a rock, leaving only silica. Then, brines containing gold ascend from the magma and precipitate metals pyrite–enargite association, including alunite and barite [57]. in the vuggy quartz forming the HS deposits. In general, the salinity of HS type deposits show a wide Earlier, we made the assumption that pyrite formation and maletoyvayamite are divergent range of values. For example, the highest salinity values of HS type ore deposits range from 5 to 24 in time based on the fact that they have never been encountered in equilibrium intergrowths [26]. wt.% NaCl eq. for Julcani, Summitville and Goldfield [65,66] (Table 5). The ranges of 3–12 wt.% NaCl Indeed, the microthermometry study on fluid inclusions in quartz confirmed this hypothesis: the most eq. are typical of the Kairagach and Shelekhovskoe [67,68]. However, data from fluid inclusions in abundant dissemination of pyrite grains occur in the earliest generations of the fine-grained quartz quartz associated with the main gold stage from Red Mountain, Mt Carlton, Lepanto, Agan, aggregate (Figure8a), with temperatures that correspond to a range of 295–245 C, whereas the Au Danchenkovskoe and Belaya Gora [27,69–72], including Maletoyvayam, indicate◦ salinities of up to minerals, sulfosalts and other associated minerals of the main ore stage crystallized at 255–245 C 4.5 wt.% NaCl eq. (Table 5). ◦ (Table3, Figures 10 and 12). Moreover, pyrite crystallization precedes enargite in many HS-type epithermalTable deposits5. Crystallization [58]. conditions parameters for HS type epithermal deposits. Selected Ore The fluid inclusions data for HS epithermalMeasured deposits (Table5) indicate that ore deposition occurred District Representative References mainly at temperatures similar to the LST and°C IS types. Salinity For example, T the °C homogenization Salinity temperatures of primaryRed Mountain, inclusions BC, inCanada quartz from 215–265 the Aginskoye (?) deposit 1.6 (LS type) 240 were 230–280 1.6 ◦C, with [69] the ore phase beingSummitville, in the range CO of 250–260 231–276◦C[59 ].(?) Similar temperature 7–21 ranges have been established[65] both for the LS typeGoldfield, deposits NV (Rodnikovoye 150–325 and (?) Asachinskoye 5–18 in South Kamchatka, Russia) [19 [65,66],21,60 ] and Julcani, Peru 161–275 (?) 5–24 [65] in regardMt toCarlton, the IS NE type Australia deposit (Cheshmeh 163–264 (57) Hafez, Iran) 0–1.6 [61], the homogenization 222 temperatures[70] of the primaryLepanto, inclusions Philippines are in the range 166–285 of 140–280 ◦C 0.2–4.5 with peaks at around 180–250 ◦C. This[71] is also compatibleKairagach, with all Uzbekistan HS type deposits, and 120–300 with the obtained <12 formationparameters of the Maletoyvayam[67] deposit (TableAgan,5). Russia 88–184 (6) 0.2–2.6 136 [27] Danchenkovskoe, Russia 297–336 1–4 [72] The salinityBelaya Gora, of ore-formingRussia solutions≈100 differs both<1 between the deposit types (LS and HS) and [68] even withinShelekhovskoe, the same Russia type (Table5). The 180–250 salinity range 3-8can be strongly influenced on one hand by the Maletoyvayam* Russia 295–245 (23) 0.9–3.3 270 2 This study Maletoyvayam** 255–245(6) 4.3 250 4.3 This study

Minerals 2020, 10, 1093 14 of 19 mixing with meteoric water (dilution), or, on the other hand, by boil-off (concentrating) [57,62]. Fluid inclusions with high salinity reflect the fluid history after crystallization of underlying magmas [63,64]. The strongly acidic hot fluids interaction with host rocks typically dissolve the surrounding rock, leaving only silica. Then, brines containing gold ascend from the magma and precipitate metals in the vuggy quartz forming the HS deposits. In general, the salinity of HS type deposits show a wide range of values. For example, the highest salinity values of HS type ore deposits range from 5 to 24 wt.% NaCl eq. for Julcani, Summitville and Goldfield [65,66] (Table5). The ranges of 3–12 wt.% NaCl eq. are typical of the Kairagach and Shelekhovskoe [67,68]. However, data from fluid inclusions in quartz associated with the main gold stage from Red Mountain, Mt Carlton, Lepanto, Agan, Danchenkovskoe and Belaya Gora [27,69–72], including Maletoyvayam, indicate salinities of up to 4.5 wt.% NaCl eq. (Table5).

Table 5. Crystallization conditions parameters for HS type epithermal deposits.

Measured Selected Ore Representative District References T ◦C Salinity T ◦C Salinity Red Mountain, BC, Canada 215–265 (?) 1.6 240 1.6 [69] Summitville, CO 231–276 (?) 7–21 [65] Goldﬁeld, NV 150–325 (?) 5–18 [65,66] Julcani, Peru 161–275 (?) 5–24 [65] Mt Carlton, NE Australia 163–264 (57) 0–1.6 222 [70] Lepanto, Philippines 166–285 0.2–4.5 [71] Kairagach, Uzbekistan 120–300 <12 [67] Agan, Russia 88–184 (6) 0.2–2.6 136 [27] Danchenkovskoe, Russia 297–336 1–4 [72] Belaya Gora, Russia 100 <1 ≈ [68] Shelekhovskoe, Russia 180–250 3–8 Maletoyvayam * Russia 295–245 (23) 0.9–3.3 270 2 This study Maletoyvayam ** 255–245(6) 4.3 250 4.3 This study Maletoyvayam *** 228–135(9) 1.3 180 1.3 This study Note. *—pyrite-quartz association (early Q1); **—maletoyvayamite-quartz association (early Q1); ***—maletoyvayamite- 2 4 quartz association (later Q − ). Salinity in wt. % NaCl eq. Selected Temperature and Salinity related to the productive stage.

The HS mineralization associated with the dilute to moderately saline solutions (<5 to ~10 wt.% NaCl eq.) occur at temperatures between 180 and 320 ◦C[71]. The hotter and more saline fluid inclusions occur in rocks of deep horizons closer to the magma fluid source [14,73]. The reduction in the sulfidation state of fluids due to interaction with wallrocks can change HS fluids to IS ones, as confirmed by paragenetic transitions from HS to IS mineralization [74]. In the IS-type epithermal deposits, salinity ranges vary widely and reaches high values, for example, 4.7–18 wt.% NaCl eq. at the Cheshmeh Hafez field [61]. While the salinity in inclusions from LS-type deposits of the Aginskoye deposit of the Central Kamchatka volcanic belt is no more than 2 wt.% NaCl equiv. [59], as in the Juliet field (LS-type), at the Okhotsk-Chukotka volcanic belt, the salinity of the inclusions is about 1.2–5.6 wt.% NaCl eq. [75]. In this respect, it is clear that the salinity of fluid inclusions is not intimately related to the type of deposit, but more dependent on the conditions of ore deposition. Based on the formation model for HS epithermal deposits [4,39,64,76,77], it can be assumed that gold–copper–porphyry mineralization may be found at deeper horizons in the Maletoyvayam area since the models for epithermal deposits form in a relatively near-surface magmatic-hydrothermal environment associated with volcanic rocks that overlie cogenetic intrusive rocks.

6. Conclusions Two mineral associations were indentiﬁed during the study of quartz mineralization at the Maletoyvayam Au-deposit: the earlier pyrite-quartz and the Au-bearing maletoyvayamite-quartz associations. Each of them contains diﬀerent generations of quartz, but only the early quartz generations Minerals 2020, 10, 1093 15 of 19

in each of the mentioned associations include either pyrite (pyrite-quartz association) or sulfosalts with gold compounds and other rare associating minerals (maletoyvayamite-quartz association). Maletoyvayamite is the main Au mineral of the maletoyvayamite-quartz association, which has never been reported in any other epithermal gold deposit in the world. It was particularly identified in samples having high Au concentrations, and occurs in the marginal parts of sulfosalts, intergrown with complex oxides of chalcogenides and native tellurium, and also as individual inclusions in quartz. The following features and physicochemical conditions on the formation of a productive ore association were identified based on the fluid inclusions study (Figures 11 and 12): The composition of primary fluid inclusions in the quartz is represented by the dominant NaCl and KCl, as well as Na2CO3 and K2CO3. The total percentage of salinity varies from 4.3 wt.%. in the early quartz from the maletoyvayamite-quartz association to 0.2 in late quartz from the pyrite-quartz association. The temperature of fluids varied from 290 to 135 ◦C, decreasing during the crystallization of the later generations of quartz (Figure 11). The calculated pressure of the fluid varies from 79 to 4 bar, and most likely corresponds to hydrostatic fluid. The fluids that formed the maletoyvayamite-quartz association differ from those forming the pyrite-quartz association with lower temperatures (255–135 ◦C), and increased salt concentration (4.3 wt.%). The increase in the total concentration of salts in the hydrothermal solutions that formed the maletoyvayamite-quartz association is due to the boiling of fluids. All parameters before presented and discussed agree in all respects with other HS-type epithermal deposits around the world; however, they do not provide further evidence of the particularities in ore mineral composition of the Maletoyvayam deposit, which is as yet the only known occurrence of the HS type on the Central Kamchatka Volcanic Belt.

Author Contributions: E.G.S. and V.M.C. provided the samples from the Maletoyvayam deposit. Conceptualization and methodology: E.G.S., N.D.T., G.A.P. and D.S.B. Investigation: A.A.B., N.D.T. and V.M.C. Writing—original draft preparation, N.D.T. and D.S.B. Editing, E.G.S. and G.A.P. Visualization, N.D.T. Supervision, E.G.S. and N.D.T. All authors have read and agreed to the published version of the manuscript. Funding: The studies were carried out within the framework of the state assignment of the Sobolev Institute of Geology and Mineralogy of the Siberian Branch of the Russian Academy of Sciences, and the Institute of Volcanology and Seismology of the Far East Branch of the Russian Academy of Sciences. Financial support was provided by the Russian Foundation of Basic Research, project No. 19-05-00316 and the grant No. 13.1902.21.0018 “Fundamental Problems of the Development of the Mineral Resource Base of the High-Tech Industry and Energy in Russia” from Ministry of Science and Higher Education of the Russian Federation. Acknowledgments: The authors thank N. Karmanov and M. Khlestov for helping with the utilization of the scanning electron microscope and an X-ray spectral microanalyzer (Analytical Center for multi-elemental and isotope research in Sobolev Institute of Geology and Mineralogy, SBRAS). We are grateful to editors and reviewers for their constructive and helpful comments, which significantly improved the manuscript. Conflicts of Interest: The authors declare no conflict of interest.

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