Figure
1.
Simplified geological scheme of Bodaybo ore region (after Ivanov, 2008).
| Citation: | Natalia N. Ankusheva, Ekaterina E. Palenova, Svetlana N. Shanina. Fluid Inclusion Evidences for the P-T Conditions of Quartz Veins Formation in the Black Shale-Hosted Gold Deposits, Bodaybo Ore Region, Russia. Journal of Earth Science, 2020, 31(3): 514-522. doi: 10.1007/s12583-019-1024-4
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The Bodaybo gold-bearing region is one of the largest gold provinces in Russia. Situated in the eastern part of Russia in the Lena River Basin, this region belongs to the Baikal orogenic belt. It hosts the well-known giant Sukhoi Log Deposit (2 956 t Au and 1 541 t Ag, Migachev et al., 2008) as well as several smaller deposits (Verninskoye, Golets Vysochayshiy, etc.). All gold deposits of the Bodaybo region are hosted by Upper Proterozoic black shales.
There are two major hypotheses for the formation of the deposits in the Bodaybo region: magmatic hydrothermal and metamorphic hydrothermal. According to the first hypothesis, the main stage of gold concentration in the ore is related to post- metamorphic intrusions, including granitoid and hypothetical deep-seated mafic complexes (Yudovskaya et al., 2011; Laverov et al., 2007; Distler et al., 2004). According to the metamorphic hydrothermal hypothesis, ore-forming fluids result from the regional metamorphism of initially metalliferous carbonaceous sequences (Large et al., 2007; Buryak and Bakulin, 1998).
Many papers have been focused on the Sukhoi Log Deposit, which is the typical of the aforementioned genetic models, whereas smaller gold occurrences in the Bodaybo region are studied poorly. But many features to understand the genesis of gold mineralization could be better defined by small deposits rather than the giant deposits, which are characterized by polygenic and polychronic ore-forming processes (Rundqvist, 1997). Therefore, the small-scaled deposits Kopylovsky, Kavkaz, and Krasnoye were studied in this work.
The study focuses on characterizing P-T conditions of the formation of the gold-bearing and barren quartz veins and fluid volatile composition of the Kopylovsky, Kavkaz, and Krasnoye deposits, on the basis of previous studies of our colleagues which aimed to describe mineralogical-geochemical features of these deposits and host rocks (Palenova et al., 2015a, b, 2013).
The Bodaybo region is the part of the Mamsko-Bodaybinsky District and composed of Upper Proterozoic carbonaceous- terrigenous sediments folded and intruded by Late Paleozoic granitoids (Fig. 1). Granitoid stocks and large batholiths of the Mamsko-Oronsky (about 420 Ma, Gerasimov et al., 2007) and Konkudera-Mamakan (2 phases, 325 and 270 Ma, Bukharov et al., 1992) complexes intrude terrigenous sequences in the southern part of the region. Also there are Late Paleozoic thin lamprophyre dykes. The sedimentary rocks are greenschist facies metamorphosed with increasing grade from chlorite-muscovite subfacies in the central part to biotite subfacies at the margins (Ivanov, 2008).
The gold deposits in the Bodaybo region consist of two large ore clusters: Kholmolkhyn, with the largest known deposits (Sukhoi Log, Verninskoe) located in the north and Artemovsky in the south (Ivanov, 2008); Kopylovsky and Kavkaz (Dogaldyn Formation (Vdg3) and Krasnoye (Vacha Formation) deposits (Palenova et al., 2015b).
The Kopylovsky Deposit is located 45 km NE from Bodaybo Town and confined to the homonymous near-latitudinal anticline—a tight asymmetric fold with gently dipping northern (42º-50º) and near-vertical southern limbs. The curved hinge of the fold dips gently to the southwest and east. Quartz veins, stockworks and NE-trending strike-slip-normal faults are developed at the hinge curvature (Palenova et al., 2015b). The host rocks are sandstones and siltstones, and carbonaceous shales of the Dogaldyn Formation metamorphosed to sericite-chlorite greenschist facies (Palenova et al., 2013). In addition, rare thin lamprophyre dykes are developed at Kopylovsky Deposit. The nearest granite pluton is located 40 km east (Aksenov, 2004). Gold ores are located in the core and north limb of the Kopylovsky anticline and predominantly hosted in carbonaceous shale intercalated with metamorphosed sandstones and siltstones.
The Kavkaz Deposit is located 35 km north from Bodaybo Town in the central part of the Vasilievsky ore field which contains a 200 to 800 m wide 'belt' of quartz veins. This belt is controlled by the Millionny and Korolkovsky oblique-slip faults which are complicated by the northern limb of the Kairo-Lenin anticline and conjugated with higher order folds, in one of which, the Vasilievsky anticline, Kavkaz Deposit is located.
The Krasnoye Deposit is situated in 75 km north from Bodaybo Town at the watershed of Krasny and Tjoply streams and confined to the complicated anticline upper bend (Kuzmenko, 2013). The deposit is hosted by carbonaceous quartz and quartzitic metamorphosed sandstones and siltstones, and less, interbedded carbonaceous shales. Gold mineralization is confined to the dispersed and lens-shaped pyrite dissemination zones, and fewer quartz veins with sulfide mineralization. Gold has formed inclusions and growths in pyrite (Ankusheva et al., 2019; Palenova et al., 2013).
All studied deposits are characterized by sulfide mineralization in the form of layers and disseminations in carbonaceous shales and metamorphosed sandstones and siltstones; quartz- pyrite veinlets in stockwork zones; nest-shaped and poor dissemination in quartz veins (Fig. 2) (Palenova et al., 2015a, b). Gold formed inclusions and growths with pyrite and native grains in quartz veins. At the deposits, ores are divided into gold- sulfide-quartz (quartz veins and stockwork zones in anticlinal fold core) and Au-sulfide (mineralized zones in host rocks) types.
Quartz veins are divided into 3 types: (1) thick (1-8 m) selliform in curves of folds and flexures; (2) concordant thin quartz- pyrite veinlets (from several millimeters to 5 cm thick); (3) the youngest veins of different thicknesses (from 1 cm to tens of cm).
Quartz (rare quartz-carbonate) veins at Kopylovsky Deposit include galena and chalcopyrite. At Kavkaz Deposit, quartz veins contain chalcopyrite, sphalerite, galena, chalcocite, secondary covellite, and visible gold. And at Krasnoye Deposit, quartz veins contain galena, chalcopyrite, and tennantite.
Microthermometric studies were performed using double- polished sections on TMS-600 (Linkam) stage at the Thermobarogeochemistry Laboratory of the South-Urals State University (Miass). The temperatures within -20 to +80 ℃ range are measured with a precision of ±0.1 ℃ and out of this range, ±1 ℃. The fluid composition was determined according to Davis et al. (1990) and Spencer et al. (1990). Salinities were calculated using the temperatures of final ice melting of fluid inclusions according to Bodnar and Vityk (1994). The pressures of trapped fluids were examined using CO2 inclusions. The fluid density was calculated using H2O-CO2-CH4 system, CO2 homogenization temperatures and molar volumes of fluid inclusions (Thiery et al., 1994; Brown, 1989). Microthermometric measurements were obtained about 300 individual fluid inclusions.
The bulk chemical composition of volatiles trapped in inclusions was determined by gas chromatography using Tsvet 800 (GS-Q station, 30 mm×0.53 mm×40 mm) with pyrolytic adapter and precolumn in Geonauka, Center of Collective Sharing (Syktyvkar). The carrier gas is helium, and quartz samples were heated in quartz reactor at 500 ℃ according to the technique of Mironova et al. (1992). Chromatographic signals were calculated by TWS-MaxiChrom software. The measuring inaccuracy is 16%.
In addition to the gas chromatography, we calculated the gaseous phase composition by Raman spectroscopy analysis of fluid inclusion composition from auriferous and barren quartz (on the sample of Krasnoye Deposit) using spectrometer LabRam HR800 Evolution equipped with Olympus BX-FM optical microscope. Raman spectra were excited using the Ar 514 nm emission line (10 mW); the lateral resolution was better than 2 μm; acquisition time was equal to 30 s; accumulation number was equal to 10 (Pankrushina et al., 2019). The nitrogen peak area from the inclusions was calculated by subtracting atmospheric N2 peak area from the measured one when focused in the gas phase.
At Kopylovsky Deposit, quartz was sampled in gold- bearing vein from a trench (sample 358-2). According to the atomic adsorption analysis, Au content in this vein is 0.73 ppm (after acid dissociation) and 1.40 ppm (after alkali dissociation). Quartz formed non-zoned anhedral grains up to 3 mm size. Fluid inclusions are bi-phase (VL) isolated, and groups unrelated to healed fractures. According to the classifications of Roedder (1984) and Van den Kerkhof and Hein (2001), these inclusions are primary and pseudosecondary confined to the fractures cracked during the quartz formation. Inclusions have irregular, rounded and sometimes 'negative crystal' shapes with 15-20 μm in size (Figs. 3a-3c).
The barren quartz of Kopylovsky Deposit was sampled from the core (sample 504-80.2), and two types of fluid inclusions have been analyzed. Type 1 is bi-phase (VL) inclusions with 15-20 μm in size and large vapor bubbles up to 50%-60% bulk. Sometimes vapor bubbles are moving but there is no liquid CO2. These inclusions are often located according to the growth zone of quartz grains why they are classified as primary inclusions. Type 2 is presented by isolated dark bi-phase (VL) fluid inclusions with size about 40 μm and large vapor bubbles (Figs. 3b, 3c). They are confined to fractures formed during the quartz formation and classified as pseudosecondary inclusions.
As for Kavkaz Deposit, we studied the quartz vein with 2 mm visible Au located in goethite cavities (sample 284-5). The bi-phase (VL) fluid inclusions are rounded, elongated, and rarely angular shapes. They formed zones or groups of 3-4 inclusions of 10-20 μm in size (Fig. 3d).
The investigated fluid inclusions in quartz from auriferous and barren quartz from Krasnoye Deposit were collected from different depths in carbonaceous schists and aleurolites confined to the folded black shales of Vacha and Aunakit suites of Patomsky Complex. In quartz from the auriferous galena-quartz vein (sample 141425-135.6), we observed bi-phase (VL) fluid inclusions of 5-25 μm in size and tri-phase CO2-rich inclusions (VLLCO2) with about 20%-50% liquid CO2-phase of the inclusion bulk (Fig. 3e). They are elongated, rounded and isometric, and sometimes 'negative crystal' shapes.
In all veins, in both auriferous and barren quartz, secondary fluid inclusions are small (not exceed 5 μm) and marked fractures in quartz. Also we observed small monophase dark (gas) and light (liquid) inclusions (not exceed 3-5 μm) which are co-genetic to primary bi-phase inclusions.
Fluid inclusion data are shown in Table 1 and Figs. 4 and 5. Microthermometric measurements were obtained from about 400 individual inclusions.
| Deposit | Veins | n | Teut (℃) (salts) | Tfm (℃) | C (wt.% NaCleqv) | Thom (℃) |
| Kopylovsky | Auri* (P, VL) Barren (P, VL) (PS, VL) |
65 45 |
-23…-24 (NaCl-KCl) -21…-23 (NaCl±KCl) -36…-37 (NaCl-FeCl2±MgCl2) |
-3.7…-5.7 -3.3…-5.7 -4.5…-5.7 |
6.1-8.8 5.5-6.8 7.5-8.8 |
300-350 200-240 260-280 |
| Kavkaz | Auri (P, VL) | 45 | -21…-23 (NaCl±KCl) | -4…-5.8 | 6.5-8.8 | 212-280 |
| Krasnoye | Auri (P, VL) CO2rich (VLL) Barren (P, VL) |
100 15 105 |
-35…-36 (MgCl2-NaCl) -31…-33 (KCl-MgCl2) -21…-23 (NaCl±KCl) |
-3.6…-7.6 -4…-7 -4.6…-10 |
6-10 5.3-8.2 7.3-13.9 |
260-330 311-330 140-280 |
| Teut. first melting temperature; Tfm. final melting temperature; C. salinity; Thom. homogenization temperature; n. number of measurements. Auri*. auriferous quartz; fluid inclusion associations: P. primary; PS. pseudosecondary; CO2-rich. tri-phased inclusions; VL. bi-phase; VLL. tri-phase CO2 inclusions. | ||||||
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The eutectic temperatures measured in fluid inclusions from auriferous quartz vein of Kopylovsky Deposit range between -23.0 and -23.8 ℃ (n=11). These temperatures are marked by the NaCl-KCl-H2O fluid. For most inclusions, the final melting temperatures of ice range between -3.7 and -5.7 ℃ corresponding to salinities between 6.1 wt.% and 8.8 wt.% NaCleqv.
Fluid inclusions of Type 1 from barren quartz vein of Kopylovsky Deposit show the eutectic temperatures range between -21.7 and -23.9 ℃, suggesting a simple NaCl-H2O system with KCl presence. In most inclusions, the final ice melting temperatures range between -3.3 and -4.3 ℃, corresponding to a salinity of 5.5 wt.%-6.8 wt.% NaCleqv.
The eutectic temperatures of the Type 2 inclusions from barren quartz vein of Kopylovsky Deposit range between -36.7 and -37.0 ℃, suggesting the presence of FeCl2 (and possible MgCl2) in fluid. The final ice melting temperatures range between -4.5 and -5.7 ℃. Salinity is 7.5 wt.%-8.8 wt.% NaCleqv.
For inclusions in quartz from the auriferous vein of Kavkaz Deposit, eutectic temperatures range between -21.8 and -23.9 ℃, indicating NaCl-KCl-H2O fluid. The final ice melting temperatures range between -4.0 and -5.8 ℃ and correspond to a salinity of 6.5 wt.%-8.8 wt.% NaCleqv.
The eutectic temperatures and salinities of bi-phase fluid inclusions in auriferous and barren veins of Krasnoye Deposit are different. For auriferous veins, they range from -35 up to -36 ℃, which identifies MgCl2-NaCl-H2O fluid; and for barren veins, they range from -22 to -23 ℃, which specifies NaCl-KCl-H2O fluid. In auriferous quartz the final melting temperatures vary from -3.6 to -7.6 ℃ and salinity is 6 wt.%-10 wt.% NaCleqv with the peak 6.5 wt.%-8 wt.%. In barren quartz the final melting temperatures are -4.6 to -10 ℃, salinity is 7.3 wt.%-13.9 wt.%, and NaCleqv with peak 10 wt.%-12 wt.%.
All studied fluid inclusions are homogenized to a liquid phase. Fluid inclusions in quartz from gold-bearing quartz vein of Kopylovsky Deposit are homogenized between 300 and 350 ℃ with multimode frequency. Fluid inclusions in auriferous quartz of Kavkaz Deposit are homogenized between 212 and 280 ℃, with the peak between 260 and 270 ℃ on the distribution plot (Fig. 4).
The homogenization temperatures of Type 1 fluid inclusions in quartz from barren quartz of Kopylovsky Deposit range between 200 and 240 ℃, with peak of homogenization between 210 and 230 ℃. Homogenization temperatures of the Type 2 inclusions in barren quartz of Kopylovsky Deposit range between 260 and 280 ℃, with the peak between 270 and 280 ℃ on the distribution plot (see Fig. 4).
The temperatures of fluid inclusion homogenization of auriferous quartz from Krasnoye Deposit are 260-330 ℃ with the peak 300-320 ℃ on the distribution plot (see Fig. 4). The temperatures of homogenization show weakly positive correlation with salinity of fluid. The temperatures of fluid inclusions homogenization of barren quartz from Krasnoye Deposit range between 140 and 280 ℃ showing bimodal distribution with small peak 160-180 ℃ and high peak 240-260 ℃. The temperatures of homogenization show weakly negative correlation with salinity of fluid (see Fig. 4).
The secondary fluid inclusions are too small in size therefore we have determined only temperatures of homogenization ranging between 130 and 180 ℃.
Trapping pressures of fluid inclusions have been determined using CO2-rich inclusions in quartz from the galena-quartz vein of Krasnoye Deposit. The temperatures of CO2 melting range between -56.7 and -57.1 ℃. The temperatures of CO2 homogenization to liquid phase range between 16.1 and 21.3 ℃. The total homogenization temperatures of these inclusions range between 311 and 330 ℃. The CO2 densities range between 0.78 and 0.85 g/cm3; molar volumes are 57-58 cm3/mol (Thiery et al., 1994). The pressures at temperature of 300 ℃ are calculated in the range of 1.2-1.6 kbar (Brown, 1989).
According to gas chromatography analysis of 4 samples, fluids are dominated by H2O and CO2 (Table 2). The total contents of volatiles in auriferous quartz from Kopylovsky and Kavkaz deposits reach 400 ppm-500 ppm, and in barren quartz from Kopylovsky and Krasnoye deposits, they do not exceed 280 ppm. The CO2 contents in inclusions from auriferous quartz range between 196 ppm and 240 ppm. The N2 contents are between 0.56 ppm and 4.4 ppm; CH4 amount does not exceed 0.37 ppm and H2O content range between 45 ppm and 300 ppm. Inclusions in auriferous quartz of Kavkaz Deposit contain 0.28 ppm H2. The ratios of СО2/(СО2+Н2О) range between 0.39 and 0.61 and СО2/СН4 is from 643 to 2 051. The correlations of volatiles are CO2 > H2O > N2 > CН4 for Kopylovsky Deposit, and H2O > CO2 > N2 > CН4 for Kavkaz and Krasnoye quartz.
| Point No. | Sample No. | H2O | CO2 | N2 | CH4 | H2 | H2O | CO2 | N2 | CH4 | H2 | ||
| (ppm) | (mol%) | ||||||||||||
| 1 | 358/2 | 151 | 240.58 | 4.44 | 0.374 | - | 59.76 | 38.95 | 1.13 | 0.167 | - | ||
| 2 | 504a/80.2 | 45 | 69.42 | 0.56 | 0.062 | - | 60.95 | 38.47 | 0.49 | 0.094 | - | ||
| 3 | 284/5 | 308 | 196.95 | 1.54 | 0.096 | 0.28 | 78.53 | 20.54 | 0.25 | 0.028 | 0.643 | ||
| 4 | 141425/135.6 | 201 | 85.04 | 0.94 | 0.045 | - | 85.01 | 14.71 | 0.26 | 0.021 | - | ||
| 1, 2. Kopylovsky Deposit: 1. auriferous quartz; 2. barren quartz; 3. auriferous quartz from Kavkaz Deposit; 4. auriferous galena-quartz vein from Krasnoye Deposit. | |||||||||||||
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The primary fluid inclusions of different shapes reaching the size of 40 μm have been found in each of the quartz samples. Their Raman spectra are presented by the superposition of several narrow bands corresponding to CO2 and N2 molecule spectra. Using the expression from Burke (2001) it was determined that the variations of CO2 mole fraction in fluid inclusion in auriferous quartz are equal to 96.9%-98.6% mol and in barren quartz, 88.3%-98.0% mol. Thus, both Raman spectroscopy and gas chromatography are consistent excluding СН4 which has not been detectable upon Raman spectroscopy because the level is below the detection limit of Raman spectrometer.
The composition and origin of ore-bearing fluids during the formation of gold deposits in black shales have been discussed in many publications (Yudovskaya et al., 2011; Laverov et al., 2007; Goldfarb et al., 2005; Distler et al., 2004; Groves et al., 2003; Rundqvist, 1997; etc.). In this study, we first studied P-T conditions of productive auriferous and barren quartz veins for small deposits of Bodaybo ore region—Kopylovsky, Kavkaz, and Krasnoye. They are similar in structural and geological and mineralogical peculiarities. As shown by Budyak et al. (2018) and Chugaev et al. (2014) and references therein, these deposits are confined to the same suits as giant Verninsky and Sukhoi Log deposits, which implies the prospects of large reserves therefore it is important to study the condition of ore formation of these deposits.
Our data highlighted that auriferous and barren quartz of Kopylovsky, Kavkaz and Krasnoye deposits have been formed due to fluids with different compositions, temperatures and salinities. The mineral-forming fluids responsible for auriferous and barren quartz veins are both water-chloride but differ in chloride composition. The fluid of auriferous quartz predominantly contains Mg and Na+K chlorides, and barren quartz comprises K and Na followed by Mg+Fe chlorides. Mg and Fe in fluids are borrowed from the host rocks containing iron- magnesia carbonates. Probably, Mg (±Fe) may be crystallized during the temperature decreasing in the form of carbonates which occurred in thick saddle-shaped quartz veins. In spite of low MgO contents in the rocks of Krasnoye Deposit (0.17 wt.%-1.14 wt.%), it reaches 2 wt.% in the sample units. In Kavkaz and Kopylovsky deposits, MgO contents are significantly higher (3.06 wt.%-6.27 wt.% and 3.53 wt.%-4.85 wt.%, respectively) (Palenova, 2015).
The auriferous quartz of Kopylovsky and Krasnoye deposits was formed when temperatures decreased from 350 to 260 ℃ and pressures 1.2-1.6 kbars. These pressures correspond to the latest productive assemblage with Ag selenides and tellurides and electrum (Palenova, 2015). But this association is not typical for the Kopylovsky and Kavkaz deposits. The salinity of the fluid is 6 wt.%-10 wt.% NaCleqv.
The fluid was water-rich (up to 300 ppm) and contained significant amount of СО2 (up to 240 ppm), and N2 (up to 4.4 ppm) and a few CH4 that might be released due to fluid/rock interaction when host black shales destruction included organic matter (Xu et al., 2011; Bottrell and Miller, 1990). This is confirmed by a carbon matter of host rocks of Krasnoye Deposit including chloroform and alcohol benzene bitumoids (Budyak et al., 2018). The assemblage of N+S+O indicates their organic genesis. The presence of nitrogen in fluid can have a catalytic effect on the leaching rate of heavy metals (Au, Ag, and PGE) from the host rocks during metamorphic and metasomatic alteration and the following deposition on the reduced geochemical barriers (Budyak et al., 2018). The coexisting monophase gas and liquid fluid inclusions and more concentrated bi- and tri-phase inclusions indicate the heterogeneous fluid (Prokofiev et al., 1994 and references therein) that may result in the gold deposition (Bowers, 1991). The CO2/CH4 ratios indicated oxidized fluid type. The H2 determined in fluid inclusions in auriferous quartz of Kavkaz Deposit may be a result of pyrolysis of organic material from host metamorphosed sedimentary rocks during OH- groups dissociation (Kulchitskaya and Chernish, 2012).
During the ore formation, carbon compounds can form metal-organic substances including with Au or be a sorption barrier (Yudovich and Ketris, 1988). Moreover, the carbon material is sensitive to the processes of temperature and pressure increasing and can indicate metamorphic transformations.
The barren quartz veins were formed at lower temperatures varying between 280 and 140 ℃. The fluid salinity is higher up to 13 wt.% NaCleqv. In fluid inclusions H2O and CO2 are also prevalent. But barren fluid is reduced in volatiles compared with auriferous fluid (bulk contents 115 ppm and 507 ppm, respectively). The higher salinity and decreased volatile amounts in barren hydrothermal fluid may be caused by the mixing with metamorphic fluids often accompanied by dehydration of the fluid (Prokofiev et al., 1994; Shepherd et al., 1991).
Our results were compared with similar data of the unique Sukhoi Log Deposit (see Fig. 1). The Р-Т conditions of barren quartz and quartz-sulfide veinlets of Sukhoi Log Deposit are 185-385 ℃, 130-2 450 bars and 130-385 ℃, 190-2 290 bars, respectively (Distler et al., 2004). According to Gavrilov and Kryazhev (2008), the auriferous and barren quartz was formed at 300-350 ℃ (primary fluid inclusion data) and at 190-290 ℃ (secondary fluid inclusion data) and pressures of 0.8-1 kbars. Similar temperatures and pressures were obtained by Rusinov et al. (2008) for deposits of Lena gold-bearing area as follows: 200-355 ℃ and 0.8-1 kbars. The salt composition of fluids contains Na+, Ca2+, Mg2+, HCO3-, and Cl- (Gavrilov and Kryazhev, 2008; Rusinov et al., 2008). The gas phase is composed of CO2, N2, and CH4 (Gavrilov and Kryazhev, 2008; Rusinov et al., 2008; Distler et al., 2004) with a dramatic prevalence of CO2 and equal amounts of N2 and CH4.
According to geological location and fluid inclusion data, quartz veins on the examined deposits were formed consistently. We suppose that auriferous and barren quartz veins have been formed due to the basic metamorphogenic fluid as evidenced by the close slat and gas fluid composition. Auriferous quartz has been formed earlier at higher temperatures, whereas barren quartz has been formed later when the temperatures decreased in the environment of plastic and breakable deformations as testified by cutting location of barren veins in fold hinges. The similar temperature decreasing from 380-447 ℃ to barren veins 154-87 ℃ is identified at Chertovo Koryto Deposit confined to Tonodsky uplift of Lena ore region in the Early Proterozoic carbon terrigenous rocks of the Mikhailovsky suit (Tarasova and Budyak, 2017). This suit is subdivided into two metamorphic stages as follows: high temperature stage up to epidote-amphibolite facies and retrograde green shale stage (Yudovskaya et al., 2016). Probably, in Chertovo Koryto Deposit, the higher temperatures of auriferous quartz formation were cause of that. In addition, Chertovo Koryto Deposit is characterized by the CO2 percentage reduction from auriferous to barren veins (from approximately 100% up to ½). As mentioned earlier (Laverov et al., 2007), at Sukhoi Log Deposit, two stages of gold formation were distinguished. The first stage is about 450 Ma and close to the age of the regional metamorphism corresponding to streaky-disseminated gold-sulfide ores and metasomatites. The second stage is about 320 Ma that close to the Konkudera-Mamakan granitoid complex formation and corresponds to barren quartz deposition. By analogy with Sukhoi Log Deposit, these stages are supposed for other deposits of Bodaybo region including Kopylovsky, Kavkaz, and Krasnoye deposits that resulted from a long geological history of the region and polychronic ore formation.
This study was partially supported by the State Contract of the Institute of Mineralogy, South-Urals Federal Research Center of Mineralogy and Geoecology, Urals Branch, Russian Academy of Sciences (Project for 2019-2021) and the Basic Research Foundation of Russia (No. 16-05-00580). Sincere thanks go to the reviewers and the editors for their suggestions. The final publication is available at Springer via https://doi.org/10.1007/s12583-019-1024-4.
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Figures(5) / Tables(2)
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Natalia N. Ankusheva, Ekaterina E. Palenova, Svetlana N. Shanina. Fluid Inclusion Evidences for the P-T Conditions of Quartz Veins Formation in the Black Shale-Hosted Gold Deposits, Bodaybo Ore Region, Russia. Journal of Earth Science, 2020, 31(3): 514-522. doi: 10.1007/s12583-019-1024-4
| Deposit | Veins | n | Teut (℃) (salts) | Tfm (℃) | C (wt.% NaCleqv) | Thom (℃) |
| Kopylovsky | Auri* (P, VL) Barren (P, VL) (PS, VL) |
65 45 |
-23…-24 (NaCl-KCl) -21…-23 (NaCl±KCl) -36…-37 (NaCl-FeCl2±MgCl2) |
-3.7…-5.7 -3.3…-5.7 -4.5…-5.7 |
6.1-8.8 5.5-6.8 7.5-8.8 |
300-350 200-240 260-280 |
| Kavkaz | Auri (P, VL) | 45 | -21…-23 (NaCl±KCl) | -4…-5.8 | 6.5-8.8 | 212-280 |
| Krasnoye | Auri (P, VL) CO2rich (VLL) Barren (P, VL) |
100 15 105 |
-35…-36 (MgCl2-NaCl) -31…-33 (KCl-MgCl2) -21…-23 (NaCl±KCl) |
-3.6…-7.6 -4…-7 -4.6…-10 |
6-10 5.3-8.2 7.3-13.9 |
260-330 311-330 140-280 |
| Teut. first melting temperature; Tfm. final melting temperature; C. salinity; Thom. homogenization temperature; n. number of measurements. Auri*. auriferous quartz; fluid inclusion associations: P. primary; PS. pseudosecondary; CO2-rich. tri-phased inclusions; VL. bi-phase; VLL. tri-phase CO2 inclusions. | ||||||
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| Point No. | Sample No. | H2O | CO2 | N2 | CH4 | H2 | H2O | CO2 | N2 | CH4 | H2 | ||
| (ppm) | (mol%) | ||||||||||||
| 1 | 358/2 | 151 | 240.58 | 4.44 | 0.374 | - | 59.76 | 38.95 | 1.13 | 0.167 | - | ||
| 2 | 504a/80.2 | 45 | 69.42 | 0.56 | 0.062 | - | 60.95 | 38.47 | 0.49 | 0.094 | - | ||
| 3 | 284/5 | 308 | 196.95 | 1.54 | 0.096 | 0.28 | 78.53 | 20.54 | 0.25 | 0.028 | 0.643 | ||
| 4 | 141425/135.6 | 201 | 85.04 | 0.94 | 0.045 | - | 85.01 | 14.71 | 0.26 | 0.021 | - | ||
| 1, 2. Kopylovsky Deposit: 1. auriferous quartz; 2. barren quartz; 3. auriferous quartz from Kavkaz Deposit; 4. auriferous galena-quartz vein from Krasnoye Deposit. | |||||||||||||
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CSV
| Deposit | Veins | n | Teut (℃) (salts) | Tfm (℃) | C (wt.% NaCleqv) | Thom (℃) |
| Kopylovsky | Auri* (P, VL) Barren (P, VL) (PS, VL) |
65 45 |
-23…-24 (NaCl-KCl) -21…-23 (NaCl±KCl) -36…-37 (NaCl-FeCl2±MgCl2) |
-3.7…-5.7 -3.3…-5.7 -4.5…-5.7 |
6.1-8.8 5.5-6.8 7.5-8.8 |
300-350 200-240 260-280 |
| Kavkaz | Auri (P, VL) | 45 | -21…-23 (NaCl±KCl) | -4…-5.8 | 6.5-8.8 | 212-280 |
| Krasnoye | Auri (P, VL) CO2rich (VLL) Barren (P, VL) |
100 15 105 |
-35…-36 (MgCl2-NaCl) -31…-33 (KCl-MgCl2) -21…-23 (NaCl±KCl) |
-3.6…-7.6 -4…-7 -4.6…-10 |
6-10 5.3-8.2 7.3-13.9 |
260-330 311-330 140-280 |
| Teut. first melting temperature; Tfm. final melting temperature; C. salinity; Thom. homogenization temperature; n. number of measurements. Auri*. auriferous quartz; fluid inclusion associations: P. primary; PS. pseudosecondary; CO2-rich. tri-phased inclusions; VL. bi-phase; VLL. tri-phase CO2 inclusions. | ||||||
| Point No. | Sample No. | H2O | CO2 | N2 | CH4 | H2 | H2O | CO2 | N2 | CH4 | H2 | ||
| (ppm) | (mol%) | ||||||||||||
| 1 | 358/2 | 151 | 240.58 | 4.44 | 0.374 | - | 59.76 | 38.95 | 1.13 | 0.167 | - | ||
| 2 | 504a/80.2 | 45 | 69.42 | 0.56 | 0.062 | - | 60.95 | 38.47 | 0.49 | 0.094 | - | ||
| 3 | 284/5 | 308 | 196.95 | 1.54 | 0.096 | 0.28 | 78.53 | 20.54 | 0.25 | 0.028 | 0.643 | ||
| 4 | 141425/135.6 | 201 | 85.04 | 0.94 | 0.045 | - | 85.01 | 14.71 | 0.26 | 0.021 | - | ||
| 1, 2. Kopylovsky Deposit: 1. auriferous quartz; 2. barren quartz; 3. auriferous quartz from Kavkaz Deposit; 4. auriferous galena-quartz vein from Krasnoye Deposit. | |||||||||||||
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