Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

RAKVERE 2018 Cover photo: The Uuga cliff at the Pakri cape is one of the best black shale exposures (a distinctive dark brown unit near the cliff wall base) in Estonia. Photo: H. Bauert.

Recommended citation style: Vind, J., 2018. Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit. Geological Survey of Estonia, Rakvere. Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

KINNITATUD Eesti Geoloogiateenistuse Teadusnõukogu otsusega nr 19-3

Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Graptoliitargilliidi uurituse ülevaade maagiotsingute potentsiaali hindamise seisukohalt

Uurimistöö aruanne

Töögrupi juht: Johannes Vind Eesti Geoloogiateenistuse direktor: Alvar Soesoo

RAKVERE 2018 Geological Survey of Estonia / Research Report EGF-8995 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Contents

List of Tables...... 6 List of Figures...... 6 1. Summary...... 8 2. Introduction and Purpose ...... 9 2.1. Scope of Work...... 9 2.2. Principal Sources of Information ...... 9 2.3. Qualifications, Experience and Independence ...... 10 3. Description and Location of Study Area...... 11 4. Physiography, Accessibility, Infrastructure, Local Resources and Climate...... 12 4.1. Physiography and Accessibility ...... 12 4.2. Infrastructure and Land Use...... 12 4.3. Climate...... 12 5. Mining and Production History ...... 13 6. Geological Setting...... 14 6.1. Overview of the Estonian Black Shale (graptolitic argillite)...... 14 6.2. Organic Carbon and Metals Potential...... 17 7. Deposit Type and Exploration Model...... 19 8. Black Shale Exploration in Estonia ...... 20 9. Mineralisation of the Black Shale ...... 22 10. Results of Previous Drillings...... 24 10.1. Data Integrity and Quality ...... 25 10.2. Uranium ...... 27 10.3. Vanadium...... 32 10.4. Lead and Zinc ...... 35 10.5. Molybdenum ...... 36 10.6. Precious and Rare Metals ...... 36 10.7. Condition and Availability of Drill Cores for Sampling...... 38 10.8. Target Area Scenarios ...... 39 11. Mineral Processing Research...... 42 12. Environmental Considerations...... 45 12.1. Groundwater ...... 45 12.2. Regional Aspects...... 45 13. Marketing Considerations...... 46 14. Conclusions ...... 47 15. Recommendations...... 48 16. References ...... 49 Glossary of Terms...... 52

5 Geological Survey of Estonia / Research Report EGF-8995

List of Tables

Table 1. Basic facts of the Estonian black shale deposit...... 15

Table 2. Mineral and grain-size composition of the crystalline fraction of Dictyonema argillite (Petersell, 1997). . 17

Table 3. Comparison of the metal grades in different black shale (or schist) deposits...... 18

Table 4. “Order of magnitude” reserves of some metallic oxides in the black shale deposit...... 24

Table 5. Concentrations of Cu, Pb, Zn, Mo and U in samples of black shale and associated sandstones from Kärdla impact structure area (K- prefix cores) and NW mainland (F- prefix cores). “Avg” denotes the average concentration ...... 36

Table 6. Target area scenarios...... 41

Table 7. Recoveries of U, Mo, and V leaching in various media and conditions...... 43

List of Figures

Figure 1. Geological bedrock map of Estonia and a geological cross section (modified after: Institute of Geology, Tallinn University of Technology, 2011)...... 14

Figure 2. Probable distribution of black shales in Baltoscandia. E – Estonia, R – Russia, F – Fasta Åland, St – Stepeniokk, N – Nordaunevoll, O – Oslo, Ös – Östersund, Öl – Öland, Sk – Skåne, Bo – Bornholm (Hade, 2014)...... 15

Figure 3. Thickness (colour scale) and depth (isobath contours) of the Estonian black shale deposit. The northern border of the occurrence area can be considered as a 0-isobath...... 16

Figure 4. Lithostratigraphy of the black shale (denoted as “Türisalu formation”, black colour). After (Heinsalu et al., 2003; Hints et al., 2014a)...... 16

Figure 5. Uranium deposits defined in Eastern Estonia in the 1940-s (according to the data of the Baltic expedition).

1 — clays, siltstones, conglomerates (РR2); 2 — clays, siltstones, sandstones (Cm1); 3 — black shale (O2-3),

4 — limestones, dolomites, marls (O2-3), 5 — sandstones, clays, dolomites (D2), 6 — uranium deposits.. . 20

Figure 6. Cross section of the deposit defined in the 1940-s in Sillamäe (according to the data of the Baltic expedition). 1 — Quaternary deposits — sand, sandy loam; 2–5 — Ordovician strata: 2 — limestones with inter layers of sandy limestones, 3 — sandstones and clays with glauconite, 4 — black shale, 5 — shelly (Obolus) sandstones; 6 — exploratory wells; 7 — parameters of uranium mineralization: in the numerator — thickness of the ore layer (m), in the denominator — the uranium content (%)...... 21

Figure 7. Position of the black shale occurrence area in Estonia with geochemical (sub)zones and geochemical profiles shown in paragraph 10.2. Abbreviations in the Location Map in upper left are: SW — Swe- den, FI — FINLAND, RU — Russia and PL — Poland; green square indicates the location of Estonia (EE). Geochemical profiles are given in Figure 13 to Figure 16...... 23

Figure 8. Drill core and outcrop locations. “Modern” data are denoted with a star and the rest are categorised as “historical” data. DB stands for “database”, indicating the data that are currently digitally ...... 23

Figure 9. Distribution of V, U, Pb and Mo by geochemical zones, represented by box-and-whisker plots. Based on “Historical dataset”. Please refer to Glossary of Terms (Appendix 1) for the explanation of the plot types.. 24

Figure 10. Comparison of quantitative wet chemical analysis and semiquantitative spectral analysis of V. Practically all the historical dataset is based on the semiquantitative spectral analysis...... 25

6 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Figure 11. Comparison of the semiquantitative analyses of U, Mo, Pb and Zn with quantitative control analyses. For U, Pb and Zn, the control method is wet chemical analysis and for Mo it is XRF...... 26

Figure 12. Borehole average concentration models depicting the distribution of V, U, Zn and Mo (Soesoo and Hade, 2014). Note that the lateral distribution of Zn has some significant artefacts due to the small numbers of Zn values available for modelling, especially in the westernmost and easternmost areas...... 27

Figure 13. West-easterly geochemical profiles in Western Estonia, 1st geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7...... 28

Figure 14. North-southerly profiles in Western Estonia, 1st geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7...... 29

Figure 15. West-easterly geochemical profiles in Toolse area, 3rd geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7...... 30

Figure 16. North-southerly geochemical profiles in Toolse area,3rd geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7...... 31

Figure 17. The indicative “order of magnitude” reserves of U, Zn and Mo in the Estonian black shale deposit, values are given in tonnes per 400x400 m unit cell (Hade and Soesoo, 2014)...... 32

Figure 18. Distribution of “historical” V values plotted on histogram, Tukey boxplot, as Empirical Cumula- tive Distribution Function and Cumulative Percentage Probability Plot. Please refer to Glossary of Terms (Appendix 1) for the explanation of the plot types...... 33

Figure 19. Distribution of “modern” V values plotted on histogram, Tukey boxplot, as Empirical Cumulative Distribution Function and Cumulative Percentage Probability Plot...... 33

Figure 20. Geochemical profile of the black shale at Saka outcrop that possesses the highest average V concentration — 1190 mg/kg V or 0,212 wt% V2O5...... 34

Figure 21. The indicative “order of magnitude” reserves of V in the Estonian black shale deposit. Values are given in tonnes per 400x400 m unit cell. Calculated with the parameters and V average concentrations map (Figure 12) given in (Hade and Soesoo, 2014)...... 34

Figure 22. Distribution of “historical” Pb values plotted on histogram, Tukey boxplot, as Empirical Cumulative Distribution Function and Cumulative Percentage Probability Plot...... 35

Figure 23. Histograms of Au, Ag, Pt and Re distribution...... 37

Figure 24. An example of an existing half-core-sampled black shale sequence from the borehole F330...... 38

Figure 25. A target area scenario in the north-west Estonia where the thickness and potential reserves of the black shale are the highest. The two considered sub-scenarios are drawn with solid outline (3 Mt of black shale per year) and dashed outline (6 Mt per year). Discussed in and drawn after Kulli et al. 2016...... 39

Figure 26. Drill core average V concentrations (“historic” data) in the eastern field of phosphorite deposits (Toolse, Aseri and Rakvere)...... 40

Figure 27. Geological cross-section of the Toolse phosphorite deposit area (Adamson et al., 1997)...... 40

Figure 28. Recoveries (%) of some of the metals in the bioleaching technology (Sipp Kulli et al., 2016)...... 44

Figure 29. An approximate value distribution of the main metallic components within the Estonian black shale deposit...... 46

7 Geological Survey of Estonia / Research Report EGF-8995

1. Summary This report reviews the exploration potential of the Estonian black shale, known locally as “graptolitic argillite” or “dictyonema shale/argillite”. The assignment was initiated by Geological Survey of Estonia to fulfil the tasks outlined in the national strategic document “General principles of Earth’s crust policy until 2050” (Ministry of the Environment, Republic of Estonia, 2017).

The existing exploration data points out that the Estonian black shale deposit represents an important future resource for several commodity metals (vanadium — V, uranium — U, molybdenum — Mo, lead — Pb, zinc — Zn) with additional value from the organic component. From a geological and exploration perspective, the follow-up investigations should be relatively easy to perform. The black shale deposit has a simple geometry and it is buried under a shallow cover. Based on a review of existing information, the established metal occurrence patterns make it easy to target prospective areas for further exploration.

Standard-compliant resource estimates are not feasible to be calculated based on existing data. How- ever, the reserves based on preliminary calculations are significant, for example 19,2 megatonnes for

MoO3, 6,7 megatonnes for U3O8 and 88,0 megatonnes for V2O5.

Further research is required to develop methods of extracting valuable compounds with maximum recovery factor while causing minimal environmental impact. Currently, there is no defined up-to-date extraction technology available and the adaptation of existing methods has either not been trialled or been tested only in lab scale.

Due to the fact that the black shale directly overlies the Kallavere formation, which contains phosphorite deposits (Obolus sandstone), the minerals contained in the shale have potential as a valuable by-product for phosphorus producers.

Tags: geochemical research, graptolite argillite, Dictyonema Shale, black shale

1. Kokkuvõte

Käesolev aruanne on kokkuvõtlik graptoliitargilliidi (ingl harilikult black shale) uurituse ülevaade, mis pöörab tähelepanu eelkõige maagiotsingute potentsiaali hindamisele. Ülesandepüstitus lähtub Riigikogu otsusest Maapõuepoliitika põhialused aastani 2050 (Keskkonnaministeerium, Eesti Vabariik, 2017).

Olemasolev andmestik viitab, et graptoliitargilliit kujutab endast mitmete metallide (nt vanaadium, uraan, molübdeen, tsink) kõrgenenud sisalduste tõttu olulist väärtust potentsiaalse maavarana. Täien- dav väärtus seisneb kivimi orgaanikasisalduses.

Rahvusvahelistele standarditele vastavat varude hinnangut pole olemasoleva andmestiku põhjal võima- lik koostada, kuid varude ligikaudsed mahud on märkimisväärsed: 19,2 miljonit tonni MoO3-e, 6,7 miljonit tonni U3O8 ja 88,0 miljonit tonni V2O5. Üks olulisemaid piiranguid ressursi kasutuselevõtul on hetkel töötlemistehnoloogia puudumine. Asjaolu, et paljudes piirkondades lasub graptoliitargilliit fosforiidi lasundi peal, võib aga luua võimalusi nende materjalide ühtseks kasutamiseks.

Märksõnad: geokeemilised uuringud, graptoliitargilliit, diktüoneemakilt

8 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

2. Introduction and Purpose

2.1. Scope of Work

The purpose of this report is to review the mineral occurrence properties throughout the whole Estonian black shale deposit for the purposes of mineral exploration. Possible exploration target areas are analysed using different scenarios or strategies. The compilation of this report was initiated by Geological Survey of Estonia (GSE) and its purpose is to: 1) provide concentrated information about the deposit for internal use, 2) provide information on the exploration (and exploitation) potential of the resource to the Government of Estonia as well as to interested third parties. By compiling the report, GSE follows the path envisioned in “General principles of Earth’s crust policy until 2050” (Ministry of the Environment, Republic of Estonia, 2017).

2.2. Principal Sources of Information The primary sources of information are the reports compiled by the Geological Survey of Esto- nia and its predecessor institutions (see: https://www.egt.ee/et/ajaloost) throughout the history of black shale studies in Estonia. The reports are stored in the Geological Report Archive (https://www.egt.ee/et/struktuur-kontakt/geoloogiafond) located in Tallinn, Estonia. Most of the reports are in Russian and are stored as hard copies and to this date a small portion of the reports have been scanned. The reports cover a period between the years 1950 and 1991 when continu- ous research was taking place. Reports drafted prior to 1950 were not archived since that was a period when the information regarding the mineralisation of uranium was highly classified. A mineral occurrence map for the black shale deposit was published in 2008. The map was based on a digitalised dataset, which contained average concentrations of five metals from 468 boreholes (Niin et al., 2008). Other academic studies conducted in recent years have relied on the same dataset (Hade, 2014; Hade et al., 2017; Hade and Soesoo, 2014; Soesoo and Hade, 2014). There are at least 99 reports in the Geological Report Archive that concern various aspects of black shale deposit or its processing (geochemistry/exploration, environmental impact, processing). Some of these reports are referred to by their codes, which consist of the letters “EGF” fol- lowed by four digits. The list of reports also includes topics that are not directly relevant to black shale (e.g. geological mapping, groundwater, other mineral resources such as phosphorite or oil shale) but still contain geological and geochemical data of the black shale deposit. In fact, much of the black shale’s geochemical data has been sourced along with the exploration of phosphorite (Obolus sandstone), which underlies the black shale in Estonia. The literature review also included more recent academic papers and reports concerning geochemistry and, to a lesser extent, the environmental concerns around Estonian black shale (Hade and Soesoo, 2014; Hints et al., 2014b, 2014a; Jüriado et al., 2012; Kiipli et al., 2000; Lippmaa et al., 2011; Lippmaa and Maremae, 2000; Loog et al., 2001; Loog and Petersell, 1995, 1994; Soesoo and Hade, 2014; Tarros, 2013; Voolma et al., 2013). While the more recent studies use data from a very limited number of samples and sampling sites, the collected geochemical variables are much more diverse compared to the historical ones. Samples were collected from outcrops, new drill

9 Geological Survey of Estonia / Research Report EGF-8995

cores (two on Suur-Pakri island — SP2 & SP3), as well as from a few re-sampled old drill cores. The data from the samples was obtained by techniques recognized in modern day exploration (ICP-MS/OES, WD-XRF, AAS). The collected data from a total of 503 samples was compiled into a dataset which is referred to in this report as “modern dataset”. Much of the previously collected exploration data (from a total of 3576 samples) was digitalised in order to complete this report. That process included scanning data tables from reports to a pdf format, after which they were digitized by Optical Character Recognition (ABBYY Fine Reader 14), and then subsequently verified. This dataset is referred to as “historical dataset” in this report. Due to the different methods and technologies used to gather data for these datasets, they are reviewed separately. In the context of this report, “historical data” was collected prior to the year 1990 and “modern data” after that. Drill cores were inspected at the core storage centre (Arbavere, Lääne-Virumaa) of Geological Survey of Estonia. The digital drill core database (https://geoportaal.maaamet.ee/est/And- med-ja-kaardid/Geoloogilised-andmed/Puursudamikud/Puursudamike-andmebaas-p382. html) was compared to the actual availability and condition of the cores. No further field work or site visits were performed.

2.3. Qualifications, Experience and Independence Geological Survey of Estonia is the government institution responsible for “conducting geological research and exploration, preserving geological information in an accessible form, advising governmental agencies and informing the public on geological matters” (https://www.egt.ee/en/ news/geological-survey-estonia-started-work). Johannes Vind, leading author of present contribution, is a geologist experienced in sedimentary and igneous environments in Europe.

10 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

3. Description and Location of Study Area

Black shale is found under the sedimentary cover throughout northern Estonia, the western islands Hiiumaa and Vormsi and a few smaller islands. The total area covered by black shale is approximately 12210 km².

There is one active exploration licence issued for drilling three drill holes (Sõtke II puuraukude uuringuruum, no 331667) in north-eastern Estonia. The licence is held by the Geological Survey of Estonia. It is valid from 07.09.2018 until 06.09.2020. The purpose of the drilling is to collect drill cores, which provide information from the metal-rich eastern part of the deposit and to provide material for bioleaching experiments.

11 Geological Survey of Estonia / Research Report EGF-8995

4. Physiography, Accessibility, Infrastructure, Local Resources and Climate

4.1. Physiography and Accessibility Most of the landscape in northern Estonia is flat and low with elevation ranging between 5 to 60 meters. The landscape was shaped by continental glaciers that started retreating about 11 000 years ago, eroding much of the underlying rock. Most of the black shale occurrence area is well accessible, the exception being some of the wetlands located in the western part of the country.

4.2. Infrastructure and Land Use The north-eastern part of the country is where most oil shale mines are located, which means it has a well-developed infrastructure for the mining industry. The landscape in north-eastern is heavily affected by mining activities. Some of the old mines have been rehabilitated, but most of the landscape affected by the mining remains in a post-mining condition. There is a rare earth elements and rare metals (Ta, Nb) processing plant in Eastern Estonia, Silla mäe. The plant is currently owned by Neo Performance Materials (https://www.neomaterials. com/about-neo/our-locations/). The processing facility is the successor to the Sillamäe uranium processing plant that started operating in the late 1940-s. Due to the proximity of the sea, there are at least 4 ports that can support economic activities in Northern Estonia (Sillamäe, Tallinn, Muuga, Paldiski). The area around the capital city of Tallinn has high population density and is focused mainly on the servicing sector. Compared to the capital region, the north-western part of the country has a low population density and rather poorly developed infrastructure.

4.3. Climate The climate in Estonia is moderate. The annual average precipitation is 672 mm. The winters are cold (average temperature in February is -4.5°C), but still relatively warm given its latitude (~57° – 59° N) due to the warming effect of the Gulf Stream. July is the warmest month with an average temperature of 17,4 °C (https://www.ilmateenistus.ee/kliima/kliimanormid/sade- med/?lang=en).

12 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

5. Mining and Production History

The radioactivity of black shales (referred to as “dictyonema shale” at that time) deposited along the southern coast of the Gulf of Finland was first reported in early 20th century. The deposits were first uti- lised for industrial development in 1948. During late 1940s and early 1950s, approximately 22,5 tonnes of elemental uranium was produced for industrial use (Veski and Palu, 2003).

Due to the discovery of more uranium-rich ores in other nearby regions, the extraction of uranium from shale was discontinued in 1952.

Over the past half-century, uranium extraction from the Baltic basin has been deemed non-viable due to low metal concentrations, lack of efficient extraction technologies and risks concerning environmental impacts.

Between 1964 and 1991, approximately 73 million tonnes of black shale was extracted overlying unit of the phosphorite that was targeted for phosphate production at Maardu refinery. The black shale was considered a waste product and it was disposed of using irresponsible methods, such as being dumped in heaps mixed with overburden or buried between limestone residues (Puura et al., 1999; Puura and Neretnieks, 2000). The irresponsible disposal practice resulted in one of Estonia’s most severe environmental damage due to the leaching of heavy metals. Dumping in heaps also resulted in the self-combustion of the black shale mainly due to the oxidation of pyrite (Jüriado et al., 2012).

13 Geological Survey of Estonia / Research Report EGF-8995

6. Geological Setting

6.1. Overview of the Estonian Black Shale (graptolitic argillite) Estonian bedrock geology is relatively simple. The region is situated on the Southern bank of the Baltic Shield. The crystalline basement (Proterozoic) is overlain with unmetamorphosed Paleo- zoic sedimentary rocks that dip southward at a rate of about 2–4 m per kilometre (Figure 1).

Bedrock B EDIACARAN

map of Estonia CAMBRIAN PROTEROZOIC B -

A Narva Tallinn Jõhvi

ORDOVICIAN

Kärdla

Paide SILURIAN Lihula

Kallaste path of the geological cross-section RUSSIA Tartu SILURIAN Pärnu Kuressaare Viljandi

DEVONIAN

Võru DEVON Valga LATVIA

South A) North B) 100 100 0 m 0 m 100 DEVONIAN SILURIAN 100 200 ORDOVICIAN 200 A 400 400 CRYSTALLINE BASEMENT (PROTEROZOIC) Geological cross-section 800 800

Figure 1. Geological bedrock map of Estonia and a geological cross section (modified after: Institute of Geology, Tallinn University of Technology, 2011).

The Tremadocian black shale (locally termed as graptolitic argillite or dictyonema shale/argillite) in Estonia is an organic-rich fine-grained sedimentary rock with an abundance of carbon, sulphur and trace metals (particularly U, V, Pb, Zn and Mo). It is a continuation of the black shale (alum shale) occurring in Southern Sweden (Figure 2), while the Cambrian to Ordovician black shales extend from Oslo region in Norway all the way to north-western Russia. The black shale in Estonia is unmetamorphosed and thermally immature (Kosakowski et al., 2017).

14 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Figure 2. Probable distribution of black shales in Baltoscandia.

E – Estonia, R – Russia, F – Fasta Åland, St – Stepeniokk, N – Nordaunevoll, O – Oslo, Ös – Östersund, Öl – Öland, Sk – Skåne, Bo – Bornholm (Hade, 2014).

The basic information on the deposit is outlined in Table 1. The data relies mainly on recently conducted GIS-based reviews (Hade, 2014; Hade and Soesoo, 2014).

Table 1. Basic facts of the Estonian black shale deposit. Area 12210 km² Rock volume 31,92 billion m³ Mass, considering a specific gravity of 2100 kg/m³ 67 billion t

The deposit has a simple monolithic sub-horizontal bedding. The deposit is thickest in West- ern mainland Estonia (up to 7 m) and it thins considerably towards the east (1–2 m), as seen in Figure 3. The strata pinches out in the southern and eastern margins of the occurrence area. The western part is stratigraphically older compared to the eastern part (Figure 4). The deposit dips southward at a rate of about 3 m per kilometre. Black shale is mainly overlain by Paleozoic sedimentary carbonate rocks. The carbonates are covered with glacial tills with variable thickness.

15 Geological Survey of Estonia / Research Report EGF-8995

400000 450000 500000 550000 600000 650000 700000 750000 E

Finland Sweden 6600000 Estonia Russia -50 -50 0 10 Latvia - -1 -150 00

6550000 0 -10 -150 -200 -250 Coordinate system: L-EST97 -250 -300 Deposit thickness 2,1 - 3 6,1 - 7 (m) 3,1 - 4 7,1 - 8 6500000 N 0,05 - 1 4,1 - 5 Isobath of the deposit's upper surface (m) 1,1 - 2 5,1 - 6

Figure 3. Thickness (colour scale) and depth (isobath contours) of the Estonian black shale deposit. The northern border of the occurrence area can be considered as a 0-isobath.

Regional W Litostratigraphy North Estonia E System Stage Conodont zone stage PAKRI Tallinn Kunda SAKA Narva

Varangu Varangu Formation Paltodus deltifer pristinus Ordovician Toolse Member Tremadocian Türisalu FormationTabasalu Member Cordylodus angulatus Katela Member Orasoja Member Suurjõgi Member Cordylodus Pakerort lindstromi Kallavere Formation Rannu Member Maardu Member Cordylodus Cambrian Furongian proavus

Figure 4. Lithostratigraphy of the black shale (denoted as “Türisalu formation”, black colour). After (Heinsalu et al., 2003; Hints et al., 2014a).

The rock exhibits mainly fine laminate bedding with minor occurrences of cross-beds. Fine mm-scale quartzose silt interlayers are frequent and more abundant in the eastern part of the deposit. The layering is mainly described as a result of variations in C content. Thin cm-scale pyrite or pyritized sandstone/siltstone layers are also present, although they occur rather heter- ogeneously throughout the deposit. Most of the rock is composed of minerals (65–75%), while the organic matter is estimated in the range of 15–20% and amorphous content is about 15%. The organic C content as well as major oxide composition is rather homogeneous throughout the deposit. Clay minerals, micas, and feldspars are the principal mineral phases found in the shale (Table 2). The occurrence of pyrite is heterogeneous, generally ranging from 2–6 wt%. Based on previous work, the distribution of trace elements and commodity metals is extremely uneven throughout the deposit (Loog and Petersell, 1994; Pukkonen and Rammo, 1992; Voolma et al., 2013).

16 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Table 2. Mineral and grain-size composition of the crystalline fraction of Dictyonema argillite (Petersell, 1997).

Content Mineral composition, % Grain-size Fraction (%) (µm) Montmoril- Swelling Micas Chlorites Quartz Feldspars lonite-illite illite, illite < 0,2 15,54 100 0,2 – 0,35 0,83 93,57 1,43 2,14 2,86 0,35 – 0,5 1,09 92,14 5,00 2,86 0,5 – 0,75 1,59 93,57 2,14 4,29 Pelite 0,75 – 1,0 2,29 84,29 7,14 8,57 1,0 – 2,0 6,0 76,43 8,00 14,14 2,0 – 5,0 35,95 40,71 1,43 24,29 34,29 5,0 – 10 16,38 19,29 0,71 35,43 43,71 Silt 10 – 100 20,33 10,29 0,57 37,86 50,14 <0,2 – 100 100 15,54 24,56 5,42 0,51 22,96 30,54

6.2. Organic Carbon and Metals Potential Black shales are often thought of as a “two-fold” (future) energy source. One energy-provid- ing component is the organic content and the other is uranium. There is clear potential for multi-component extraction since the rock contains considerable concentrations of U, V, Mo, Pb, Zn, Co, Ni as well as traces of precious metals like Au and PGE. The Estonian black shale calorific value ranges from 4.2–6.7 MJ/kg (Pukkonen and Rammo, 1992) and the Fischer Assay oil yield is 3–5 %. The following is a comparison of metal concentrations in some of the most important black shale deposits that are being exploited or explored (Table 3). The summary is adapted and extended based on Sipp Kulli et al., (2016). The grades of the Estonian black shale are based on calculations of average concentrations from the “modern” dataset (504 samples), except for the organic C and Au concentrations that are reported as average values from the “historical” data.

17 Geological Survey of Estonia / Research Report EGF-8995

Table 3. Comparison of the metal grades in different black shale (or schist) deposits.

Major Estonia Alum Shale Alum Shale Kupferschiefer Talvivaara, component % Graptolite (Central Sweden, (Central Sweden, (Poland) (Gouin et al., Findland Kyrk Tåsjö) Häggan) (Revee, 2015; Włodarczyk et argillite (Bhatti, 2015) 2018, 2017) al., 2015) Black schist (Loukola-Ruskeeniemi, 1992; Loukola-Rus- keeniemi and Lahtinen, 2013) Organic C 11,83 10,77 7,98 Total S 2,77 5,25 1,9–3,9 8,4 Ore metal (mg/kg) U 117 160 161* 17 V 1055 920 2400* 943–1084,3 570 Mo 177 470 207** 168,9 45 Zn 336 790 431** 26–117,6 5300 Ni 154 210 316** 292,6–333,5 870–2600 Cu 117 140 34 958–77 300 910–1400 Pb 126 50 121,1 47 As 61 160 1598 86 Co 24 20 334,5–1287 93 Cd 2,5 10 10 Au 0,07 0,0095 Re 0,159

* at 2200 mg/kg V cut-off (Revee, 2018) ** at 85 mg/kg U cut-off (Revee, 2017)

18 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

7. Deposit Type and Exploration Model

Black shales are considered as low-grade metal ores rather than a hydrocarbon source. However, along with other approaches, considerable effort has been put into investigations of shale gas and oil potential of the black shales.

Important exploitable or historically exploited black shales are located in Germany/Poland (Kupfer- schiefer) (Vaughan et al., 1989; Włodarczyk et al., 2015), and Sweden (Alum Shale) (Andersson, 1985; Schovsbo, 2002). Metamorphosed black shales or black schists are exploited in Finland, Talvivaara (Sotkamo mine). The latter is a unique example, where the complex processing of Ni, Co, Cu, Zn, (Mn) and (U) is performed via the bio-heap leaching method (Pattinson et al., 2013; Riekkola-Vanhanen, 2013).

Fluctuations in metal market prices are currently restructuring the black shale exploration models. The development and demand for vanadium batteries, mainly required for storing energy in renewable source power plants, has seen a rapid increase in vanadium prices (Desjardins, 2017). In the Häggan deposit in Sweden, exploration focus has almost completely shifted from U to V in recent years, resulting in the project to now be known as the “Battery metals project”. In the Häggan deposit, a high-grade vanadium zone, starting at the upper stratum, has been defined with a 0,4 wt% V2O5 cut-off scenario at 0,42 wt% average V2O5 (2352 mg/kg V). The estimated resource is 90 million tonnes of shale at this cut-off value.

Different scenarios are outlined by cut-off values with the minimum being 0,1 % V2O5 (Revee, 2018).

19 Geological Survey of Estonia / Research Report EGF-8995

8. Black Shale Exploration in Estonia

As mentioned in chapter 2, the original information about the early exploration in the 1940s and 50s of the Estonian black shale is missing from the Geological Report Archive of EGS. During this period, information about U-containing mineral resources was classified and the reports were not archived in Estonia. Only some unofficial extracts from those early reports are available that provide schematic cross-sections and general deposit maps (e.g. Figure 5, Figure 6).

Figure 5. Uranium deposits defined in Eastern Estonia in the 1940-s (according to the data of the Baltic expedition). 1 — clays, siltstones, conglomerates (РR2); 2 — clays, siltstones, sandstones (Cm1); 3 — black shale (O2-3), 4 — limestones, dolomites, marls (O2-3), 5 — sandstones, clays, dolomites (D2), 6 — uranium deposits.

20 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Figure 6. Cross section of the deposit defined in the 1940-s in Sillamäe (according to the data of the Baltic expedition). 1 — Quaternary deposits — sand, sandy loam; 2–5 — Ordovician strata: 2 — limestones with interlayers of sandy limestones, 3 — sandstones and clays with glauconite, 4 — black shale, 5 — shelly (Obolus) sandstones; 6 — exploratory wells; 7 — parameters of uranium mineralization: in the numerator — thickness of the ore layer (m), in the denominator — the uranium content (%).

In 1944, the information concerning radioactivity was checked and confirmed by geologists of the USSR’s North-Western Geological Administration. The largest concentrations were recorded in the middle part of the deposit within the northeast of Estonia and the western part of St. Petersburg (Leningrad at the time) region. Uranium concentrations varied from thousandths to a few hundredths of a percent (0,008 wt%–0,075 wt%). In addition to uranium in the shale, elevated molybdenum and vanadium contents were also recorded.

Since 1945, the Baltic expedition identified 14 deposits of low-grade uranium ore — Sillamae, Toila, Aseri, Saka and others in the present-day Russian territory. The deposits were explored by boreholes along forming networks of 250x250 m and 125x125 m. Alongside uranium exploration, a black shale enrichment technology was developed to produce uranium concentrates from the rock.

Much of the information on the black shale deposit after the 1950s was gathered along with the exploration of oil shale (kukersite), phosphorite (Obolus sandstone) and during geological mapping projects. Since the exploration results were physically stored in Estonia after the 1950s, they have since been then passed over to the currently operating Geological Survey and are thus fully accessible (currently mainly as hard copies, digitalisation process is ongoing).

The exploration for phosphorite was especially intensive in the 1980s. One of the strategies for the exploitation of phosphorite was for it to be mined a nd used together with the black shale, which resulted in a detailed surveying of primarily U, Mo, Pb and V distribution in the black shale. The drill cores of one of the principal exploration campaign have prefixes “D” and the identifier of the report is EGF4359 (Rammo et al., 1989). Much of the data collected for the “historical” dataset is based on this report.

21 Geological Survey of Estonia / Research Report EGF-8995

9. Mineralisation of the Black Shale

The mineralisation of the economically important metals (U, Mo, V, Pb) is thought to be mainly syn geneic or early diagenetic. The distribution of these metals is thought to be heterogeneous both vertically and laterally, although certain regularities are also evident (e.g. higher concentrations of some metals at the base of the strata).

The general understanding is that Pb, Zn, Cu, As and Ni are associated with sulphide phases (mostly pyrite) in the deposit. At times, Ni reaches very high concentrations (4000 mg/kg) in pyrite mixed with thin (< 2mm) pelitic layers (Pukkonen and Rammo, 1992). In the occurrence of high Zn concentrations (0,5–1 wt%), sphalerite presence is documented. In certain 2–3 cm silty interlayers, sphalerite presence has been estimated to reach 8–10 % of the rock mass (Petersell et al., 1991).

The concentrations of V, Mo and U are thought to be mainly associated with the organic matter. This is not a clear trend as the distribution of the metals between the carriers can be bimodal. In other words, in the case of higher concentrations, there is a tendency to prefer sulphide (or phosphate) mineralisation and vice versa (except for V that does not accumulate to pyrite). The duality of the association with organic matter is referred from the statistical analysis that implies a clearer covariance with the organic material in the case of lower V, Mo and U concentrations. The covariance becomes less significant in the case of higher V, Mo and U, while it remains the strongest in the case of V.

Lippmaa, 2011 states that V occurs as V porphyrine in the deposit, however the source of this information is unclear. On the other hand, in the case of Häggån “Battery metals project” that is geologically analogous, V “is present mainly in the form of V(III) hosted with the mica mineral roscoelite” (Revee, 2018). A study of the V occurrence forms at the The Mecca Quarry Shale Member from Velpen, Indiana, names authigenic illite and orgnic matter as the main carriers of V (Peacor et al., 2000). Even free oxide is reported to be an occurrence form of V in one Chinese black shale unit (Min-ting LI 2010). The “Grap- tomet 1 and 2” technology (see section 11) authors claim the decomposition of most of the organic compounds. At the same time there isn’t any indication of V release to the leachate (Figure 28) (Menert et al., 2017; Sipp Kulli et al., 2016). The latter example also emphasises the uncertainty in the knowledge of V speciation. This paper questions whether the assumption of V existing mainly in metalloporphyrines is supported by evidence in the case of Estonian black shale?

Generally, many metals occur as metalloporphyrines in black shales (Szubert et al., 2006). In Southern Sweden, the thermally immature black shales were shown to host U in biogenic matter as well as within phosphate nodules (Lecomte et al., 2017). The association of U with P has also been implied in the case of Estonian deposit, but not as a primary one (Petersell et al., 1991; Pukkonen and Rammo, 1992). It is noted that a small fraction of U could be also associated with silicate minerals as well as a discrete uraninite phase. Currently, there is no literature on detailed mineral occurrence speciation by modern methods with regards to any commodity metal contained in black shale.

22 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

10. Results of Previous Drillings

The black shale deposit can be divided into four geochemical zones, numbered 1 to 4 from west to east (Figure 7). Zones 3 and 4 are sometimes grouped together as a single zone, which would result in the definition of Western, Middle and Eastern zones. However, since there are distinct differences in the lateral distribution of U and Mo, but also V (see Figure 12), the 4-part zonation model is considered to be more appropriate for a general description of the deposit (Figure 7). Subzone 1a refers to a region where the middle part of the strata contains elevated amount of sandy/silty intervals with concurrent elevated U and Mo concentrations, compared to the homogeneous black shale in the surrounding strata. Subzone 1b denotes the region, where the profiles are enriched in U and Mo throughout the deposit in contrast to the typical trend of downwards-enrichment. This is discussed further in sections 10.2 and 10.5 (Figure 14).

400000 450000 500000 550000 600000 650000 700000 E

! 6600000 ! FI ! ! MAARDU ! NARVA SW TALLINN !!! !!!! ! EE % % ! JÕHVI % % RU ! % SILLAMÄE RA! KVERE PALDISKI % % ! PL ! (3) ! ! (2) ! ! (4) ! (1) ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! !! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !! ! ! ! ! !! ! ! !

! (1a) ! ! ! ! 6550000 ! KÄRDLA ! RAPLA % ! ! % ! HAAPSALU ! ! % ! !! Legend !

! (1b) ! Geochemical profiles with borehole locations Geochemical zones (1-4) Black shale occurrence area 6500000N Geochemical subzones Coordinate system: L-EST97

Figure 7. Position of the black shale occurrence area in Estonia with geochemical (sub)zones and geochemical profiles shown in paragraph 10.2. Abbreviations in the Location Map in upper left are: SW — Sweden, FI — FINLAND, RU — Russia and PL — Poland; green square indicates the location of Estonia (EE). Geochemical profiles are given in Figure 13 to Figure 16.

400000 450000 500000 550000 600000 650000 700000 750000

Finland

" Sweden " " " " " " " " " " " " " " " " ( " 6600000 " " " " " " " " " ((("(" " " " " " " " ((((( "" " "_ " "(((" " "" "" " " " " " " "("("("("" " " Estonia " " " " " " (((_(( " " " " " " " " " " " " ( " " " "" " " " " " " "" " " " " " (" ((("(((" " ( " "" " " " " "" " " " " "((((((" " " ""( " ("("" ""( " " ( " " " " " " ( " " ( " "( (" " " ((_" " " " " ( " " " (((" " " " " " " " " " " " " " " " " "" " _ " " " " ( " " " " " _( ( " _ " "" " " " " " ( " ( ( " Russia " " " (" (("" "" " " " ( " " " " " " ( " " " " " ( ("( " " " " " " " " " " " " ( " ( " " " " " ( " " " ( " ( " " " "("" (" (" " " " ( " ( " "" " " " (" " " " " " " " " " " " " ( ((""((((("" "( ""( ( " " ( " " " " ( ( " " " " " " " " " " " """ "" " " " ( ( " " " " ( " ( " " " " " ( " " " " _ " " " " " " " (" ("" " ( ( " "" " " " ( " ( ( ( " " " "" ( ( " " " ( ( " " " (" " ( " ( ( " " " " " ( " ( " " " "" (( " " " " ( ( " " " " " " " " " ( ( " _ ( ( " " " " ( " " " _ ( " " " " ( " " " " ( ( " " " " " " " ( " " ( " " "" " " " " " " " "" (" " ( Latvia "" " " ( " " ( " (( " " ( ( " ( " " " " " ( ( " " " ( " ( " " " ( " " " " " " " " "" ( " " ( " " ( ( " ( ( (( " ( ( " (" " " " " " " " ( " " ( " " " ( ( " " " " " " " " " " ("" " " (" " " " " " " " "" " " " " " " " " " ""(( " " " " " (" " "" " "( " ("""""""(" ((((((((( " (("(( ( " ((((((((( ((((( (("(((" (((("" " "( " " " " ( " " " ( " " " " (" ( " ( ( " ( ( ( " " " " ( " " " (" ( ( ( " " ( ( " ( " " " " " " ( " ( " " ( " " ( " " ( " ( " " " ( " ( " ( " ( " " ( ( " " " " " " " " " " _( " " "(_ " (( " " " " "( ( " ( " " ( ( ( (" " " " ( " ( " (" ( _" ( " " " " 6550000 " "_" ( ( ( " " ( ( ( ( ( ( " " " " " ( " ( " " " " " ( " " ( " ( ( " ( ( (" ( " ( " ( "( " " " " _ " " "( " " ( ( " (" ( " " " " ( " " ( " " ( (" ( " " ( " (" (" ( " ( ( " " " " " " " " ( " " (" _" ( ( ( " ( " " ( " "" ( " " (( ( " " (" " " " ( ( " ( " "" ( ( " ( ( (( " (" " " " " " " " (" ( ( ( _ ( " " ( " ( " " ( " " Legend (" (" " " " " " " ( (" " " ( ( ( (" ( ( ( ( " " " " _ Locations of cores and outcrops with "modern data" " " " ("" " Drill cores with average composition collected to DB 6500000 ( Drill cores with data by intervals colleted to DB Coordinate system: L-EST97

23 Geological Survey of Estonia / Research Report EGF-8995 V (mg/kg) V U (mg/kg) U 2 5 10 50 200 1000 20 50 100 500 2000

1234 1234

Zone Zone Pb (mg/kg) Pb Mo (mg/kg)Mo 20 50 100 500 2000 10 20 50 200 500 2000

1234 1234

Zone Zone

Regardless of the lateral metal grade distribution, the western part of the deposit contains the most reserves due to the greatest thickness of the deposit (5–7 m). While preliminary calculations of resources can be performed, proper standard-compliant resource estimates cannot be done with the current level of available information and knowledge. To have an overview of the possible magnitude of the ton- nages, the “order of magnitude” reserves for the black shale deposit are given in Table 4:

Table 4. “Order of magnitude” reserves of some metallic oxides in the black shale deposit.

Resource “Order of magnitude” reserve (Mt) Reference

MoO3 19,2 (Hade and Soesoo, 2014)

U3O8 6,7 (Hade and Soesoo, 2014) ZnO 20,6 (Hade and Soesoo, 2014)

V2O5 88,0 Current

24 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

10.1. Data Integrity and Quality Sampling methods have varied throughout different exploration campaigns. It is possible to identify spot sampling (thin slices extracted from the core), chip sampling or full core sampling. At the time of the conditionally termed “historical” exploration, split core sampling was not prac- ticed. Some of the samples were acquired by trenching in the frame of phosphorite exploration. Samples for “modern” dataset have been either collected as split core samples from old drill cores and two new drill cores (Suur-Pakri 2 and 3), or from outcrops. In some instances (Loog et al., 2001), only certain sections of the core have been sampled instead of the full core. Thus, samples in both the “historical” and “modern” dataset have a different magnitude of representativeness. Comparison of the V analysis by two methods indicates an underestimation of the semiquanti tative spectral V by an average of 42 % (EGF 4085). The underestimation is systematic, as seen on the plotted values in Figure 10. The likeliness of V underestimation in the “historical” dataset is also supported by the “modern” dataset. While the “modern” dataset has a significantly smaller sample size as well as geographical coverage, it also has a significantly higher average concentration value (1055 mg/kg V) than the historical dataset obtained by semiquantitative spectral analysis (average 649 mg/kg V).

1000

900

800

700

600

500

400

300

200 Semiquantitative analysismg/kg) Semiquantitative spectral (V 100 0 500 1000 1500 2000 Atom absorption analysis (V mg/kg)

Figure 10. Comparison of quantitative wet chemical analysis and semiquantitative spectral analysis of V. Practically all the historical dataset is based on the semiquantitative spectral analysis.

25 Geological Survey of Estonia / Research Report EGF-8995

Similarly, the semiquantitative analyses of U (EGF 3200) Mo and Zn (EGF 4085) that comprise majority of the “historical dataset” are systematically underestimated (Figure 11). On average, U is underestimated by 19 %, Pb by 46 %, and Zn by 75 %. The pattern is slightly different for Mo, for which the differences typically range from -24 % to +11 %, with a few samples, where the concentration is underestimate by more than 200 %. Since U has historically been the main focus in the exploration of black shale, its analyses have been conducted with a greater attention to detail, which is supported by the smallest differences (19 %) in the comparison. In most of the exploration reports, quality assessment of U measurements is included.

1000

900

(mg/kg) 800

700

600 U 500 Zn 400 Mo 300 Pb 200

100 Semiquantitative analysisSemiquantitative spectral 0 0 200 400 600 800 1000 1200 1400 1600 1800 Quantitative control analysis (mg/kg)

Figure 11. Comparison of the semiquantitative analyses of U, Mo, Pb and Zn with quantitative control analyses. For U, Pb and Zn, the control method is wet chemical analysis and for Mo it is XRF.

The results above lead to the following conclusions: (1) The “historical dataset” is too unreliable for making resource estimates other than “order of magnitude” type; (2) The effect of systematic underestimation shows where true anomalies lie, i.e. the geo chemical data can be used as relative information of mineralised rock sequences.

26 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

10.2. Uranium The highest average uranium concentrations are found in the eastern part of the deposit, in the 4th geochemical zone. This is also the area where black shale has historically been exploited. It is well established throughout the deposit that U is concentrated vertically towards the lower parts of the profiles (Figure 13, Figure 14).

V concentration (ppm) Tallinn 0 12,5 25 50 Kilometers

Estonia

Russia

V, ppm High : 1083

Low : 482

U concentration (ppm) Tallinn 0 12,5 25 50 Kilometers

U, ppm Russia High : 329

Low : 38

Tallinn Zn concentration (ppm) 0 12,5 25 50 Kilometers

Russia Zn, ppm High : 593

Low : 39

Tallinn Mo concentration (ppm) 0 12,5 25 50 Kilometers

Russia

Mo, ppm For gridding used method: High : 751 Kriging Ordinary Gaussian semivariogram model Low : 71 Search radius: Variable Used number of nearest input sample points 12.

27 Geological Survey of Estonia / Research Report EGF-8995

Figure 13. West-easterly geochemical profiles in Western Estonia, 1st geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7.

28 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

138 46 47 141 142 143 145 146 147 148 150 157 152 12K 153 0 V (mg/kg)

1 51 1400 2 1200 1000 3 156 800 600 4 161 151 139 140 400 117 5 48 49 149 F323 144 50 200

138 46 47 141 142 143 145 146 147 148 150 157 152 12K 153 51 0 U (mg/kg) 1 230 T 210 2 190 170 150 h 3 130 156 110 4 161 90 151 139 70 i 140 50 5 117 149 F323 144 48 49 50 30

138 46 47 141 142 143 145 146 147 148 150 157 152 12K 153 51 c 0 Mo (mg/kg) 1 1150 1050 k 950 2 850 750 n 3 650 156 550 450 4 161 350 151 e 139 250 140 150 5 117 149 F323 144 48 49 50 50

138 46 47 141 142 143 145 146 147 148 150 157 152 12K 153 51 s 0 Pb (mg/kg) 1 400 s 360 2 320 280 3 240 156 200 160 4 161 m 151 120 139 140 80 5 117 149 F323 144 48 49 50 40

138 46 47 141 142 143 145 146 147 148 150 157 152 12K 153 51 0 Q (kcal/kg) 1 1800 1700 1600 2 1500 1400 1300 3 1200 156 1100 1000 4 161 151 900 139 800 140 5 117 149 700 F323 144 48 49 50 600 6570000 6560000 6550000 6540000 6530000 N (L-EST 97)

Figure 14. North-southerly profiles in Western Estonia, 1st geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7.

29 Geological Survey of Estonia / Research Report EGF-8995

Geochemical distribution profiles of the available analytes in the eastern part of the deposit are shown in Figure 15 and Figure 16.

828 465 515 475 477 938 946 487 0 V mg/kg

1800 0,5 1600 1400 1200 T 1,0 1000 800 h 600 1,5 400 200 i 0 828 465 515 475 477 938 946 487 U 0 mg/kg c 480 0,5 k 400 320 1,0 240 n 160 1,5 80 e 0

828 465 515 475 477 938 946 487 0 Mo s mg/kg 1200 1100 0,5 1000 s 900 800 700 1,0 600 500 400 300 m 1,5 200 100 0 635000 636000 637000 638000 639000 640000 641000 642000 643000 E (L-EST 97)

Figure 15. West-easterly geochemical profiles in Toolse area, 3rd geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7.

30 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

439 804 437 442 941 940 T55 PRIV-7 R1539 0 V mg/kg 1800 T 0,5 T58 1500 1200 h 1,0 900 797 600 i 938 1,5 300 0

c 439 804 437 442 941 940 T55 PRIV-7 R1539 0 U k mg/kg 0,5 T58 500 n 420 340 1,0 260 e 797 180 1,5 938 s 100 20

439 804 437 442 941 940 T55 PRIV-7 R1539 s 0 Mo mg/kg

T58 0,5 1200 1000 800 m 1,0 797 600

938 400 1,5 200 0 6596000 6594000 6592000 6590000 6588000 6586000 6584000 6582000 6580000 N (L-EST 97)

Figure 16. North-southerly geochemical profiles in Toolse area,3rd geochemical zone. The interpolation method used is Kriging. Location of the profiles is shown in Figure 7.

The reserves of uranium and accompanying elements - nickel, molybdenum, vanadium, sulphur - have been calculated for the deposits explored in the 1940-s. A total of 72,0 thousand tonnes of uranium have been explored in the Baltic area in poor ores. In the Sillamäe field, the Reserves Commission approved uranium reserves for category “B” in the amount of 5464 tonnes with an average grade of 0,026 % uranium in the ore. In addition to uranium, the ore contained other elements in following concentrations: Ni — 0,026%, Mo — 0,045%, V — 0,084%, S — 5,25%. In the Toila deposit, 7,0 thousand tonnes of uranium with an average content of 0,025% U in the ore was explored. The indicative distribution of reserves of U over the extent of the total deposit is given in Figure 17 (Hade and Soesoo, 2014). The distribution of potentially available reserves per area is mainly controlled by the thickness (Figure 3) rather that the commodity metal grade of the rock (Figure 12) in the case of all presented metals.

31 Geological Survey of Estonia / Research Report EGF-8995

Figure 17. The indicative “order of magnitude” reserves of U, Zn and Mo in the Estonian black shale deposit, values are given in tonnes per 400x400 m unit cell (Hade and Soesoo, 2014).

10.3. Vanadium Laterally, the distribution of V is perhaps the most complex, yet the concentrations are somewhat less spread than those of the U, Mo and Zn. The highest V concentration zone is in the Toolse and Sillamäe area, coinciding partly with the Toolse and Aseri phosphorite deposits. V concentrations are populated above 1000 mg/kg in the modern dataset compared to the “historical” dataset, for which the main population is under 1000 mg/kg. This once again emphasizes the underestimation of V and the possibility of actual V concentrations being much higher than described in the past.

32 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Histogram Tukey Boxplot

1200 N = 2829 1000 800

600 400

200 N = 2829 0

5 10 20 50 100 200 500 1000 2000 5 10 20 50 100 200 500 1000 2000

V (mg/kg) V (mg/kg)

Empirical Cumulative Distribution % Cumulative Percentage Function (ECDF) (Normal) Probability (CPP) Plot

1.0 0.8 99 90 0.6 50 0.4 10 0.2 1 N = 2829 N = 2829 0.0

5 10 20 50 100 200 500 1000 2000 5 10 20 50 100 200 500 1000 2000

V (mg/kg) V (mg/kg)

Figure 18. Distribution of “historical” V values plotted on histogram, Tukey boxplot, as Empirical Cumulative Distribution Function and Cumulative Percentage Probability Plot. Please refer to Glossary of Terms (Appendix 1) for the explanation of the plot types.

Histogram Tukey Boxplot

N = 503 120 Bins for 4 100 points omitted 80

60 40 20 N = 503 0 4 points omitted

200 500 1000 2000 200 500 1000 2000

V(mg/kg) V(mg/kg)

Empirical Cumulative Distribution % Cumulative Percentage Function (ECDF) (Normal) Probability (CPP) Plot

1.0 99 0.8 90 0.6

0.4 50 0.2 10 N = 503 N = 503 0.0 4 points omitted 1 4 points omitted

200 500 1000 2000 200 500 1000 2000

V(mg/kg) V(mg/kg)

Figure 19. Distribution of “modern” V values plotted on histogram, Tukey boxplot, as Empirical Cumulative Distribution Function and Cumulative Percentage Probability Plot.

33 Geological Survey of Estonia / Research Report EGF-8995

The distribution patterns in vertical sections are uneven, sometimes indicating an increase towards lower part of the section, but there appears to be no clear trend. The W-E profile in Figure 13 depicts the cross-over from the higher V in the western 1st geochemical zone to the middle low-enrichment level of the 2nd zone. The vertical distribution is therefore different to the one documented in Sweden’s Häggan deposit, where the highest V contents are identified in the upper part of the stratum (Revee, 2018). The highest “modern” V core/outcrop weighted average concentrations are recorded in Saka

outcrop (0,212 wt% V2O5, Figure 20), Toolse core 811 (0,206 wt% V2O5), WE mainland cores F348

and F346 (both 0,201 wt% V2O5). The highest V2O5 values reach 0,375 wt% in “historic” and 0,378 wt% in the “modern” dataset.

2,00 1,80 Saka outcrop 1,60 1,40 1,20 1,00 V

Depth (m) 0,80 U 0,60 Mo 0,40 Pb Figure 20. Geochemical profile of 0,20 the black shale at Saka outcrop that 0,00 possesses the highest average V 0,00 500,00 1000,00 1500,00 2000,00 concentration — 1190 mg/kg V or Concentration (mg/kg) 0,212 wt% V2O5.

The “order of magnitude” V reserves distribution over the extent of black shale occurrence area is given in Figure 21.

400000 450000 500000 550000 600000 650000 700000 750000 E

FI SW EE RU 6600000 TALLINN MAARDU SILLAMÄE NARVA % % % %

6550000 KÄRDLA %

V mass in tonnes 1850 863 11 6500000 N Coordinate system: L-EST97

34 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

10.4. Lead and Zinc Pb occurs in uniformly elevated concentrations (average 127 mg/kg Pb in the “historical” data) throughout the deposit and anomalous concentrations are relatively rare, yet some samples exhibit concentrations of > 500 mg/kg. The distribution of Pb in vertical sections is indifferent when comparing upper and lower parts. The Zn levels in Estonian black shale are relatively low compared to the average values seen in black shales elsewhere in the world. The lateral distribution of Zn depicted in Figure 12 has some significant artefacts due to the small numbers of Zn values available for modelling. The most intense Pb-Zn mineralization is located on the NE of the external slope of the Kärdla impact structure in Hiiumaa island. In boreholes K-11, K-14 and K-15, intensive pyrite-galena- sphalerite mineralization is observed in the upper stratum of black shale (Table 5). The interbed of sapropelite-containing sandstone lying in the lower strata of the bed is cemented by pyrite, galena and sphalerite. In the lower stratum of black shale within the Obolus sandstones, mineralization is represented only by pyrite and sphalerite, and with lower intensity compared to the one seen in upper layers (Petersell et al., 1991). Below the black shale near Dirhami in north-western Estonia, intensively pyritized sandstones are present with an abnormally high Pb content (up to 0.14 wt% in F334), Mo (up to 0.16 wt% in the well FЗЗ1), and Ag (up to 2.3 mg/kg in F334) (Petersell et al., 1991).

Histogram Tukey Boxplot

N = 2670 Bins for 2 200 points omitted 150

100 50 N = 2670 0 2 points omitted

10 20 50 100 200 500 1000 2000 10 20 50 100 200 500 1000 2000

Pb (mg/kg) Pb (mg/kg)

Empirical Cumulative Distribution % Cumulative Percentage Function (ECDF) (Normal) Probability (CPP) Plot

1.0 0.8 99 90 0.6 50 0.4 10 0.2 N = 2670 1 N = 2670 0.0 2 points omitted 2 points omitted

10 20 50 100 200 500 1000 2000 10 20 50 100 200 500 1000 2000

Pb (mg/kg) Pb (mg/kg)

Figure 22. Distribution of “historical” Pb values plotted on histogram, Tukey boxplot, as Empirical Cumulative Distribu- tion Function and Cumulative Percentage Probability Plot.

35 Geological Survey of Estonia / Research Report EGF-8995

Sampling Cu (mg/kg) Pb (mg/kg) Zn (mg/kg) interval (m) Thickness Core min avg max min avg max min avg max Black shale and (m) sandstone* K-14 96.3-97.2 0.9 52 92 104 420 2150 26500 1230 3480 12860 102.3-103.1 0.8 21 71 73 57 163 230 363 1120 3800 K-15 97.6-98.8 0.8 83 94 104 180 6166 15360 1410 5234 10120 103.3-103.8 0.5 52 54 65 113 132 150 300 2442 15400 F330 90.4-90.5* 0.1 110 300 40 F331 52.0-53.0* 1.0 50 65 80 50 140 200 30 50 F334 46.8-47.0* 0.2 300 1300 120 F335 69.7-70.1 0.4 50 90 11 50 F337 90.2-90.4 0.2 75 140 250

Sampling Mo (mg/kg) U (mg/kg) Ni As interval (m) Thickness Core min avg max min avg max Black shale and (m) sandstone* K-14 96.3-97.2 0.9 24 208 294 20 61 67 102.3-103.1 0.8 2 11 12 5 9 13 K-15 97.6-98.8 0.8 80 150 239 39 51 65 103.3-103.8 0.5 4 11 15 11 13 16 F330 90.4-90.5* 0.1 22 420 F331 52.0-53.0* 1.0 490 870 1600 150 F334 46.8-47.0* 0.2 100 1100 1100 F335 69.7-70.1 0.4 250 380 F337 90.2-90.4 0.2 230 150

10.5. Molybdenum Molybdenum’s lateral distribution is similar to V as the highest concentration levels are present in the 3rd geochemical zone (392 mg/kg Mo on average). Further towards the east, concentrations drop. Mo is vertically very distinctly partitioned. The top of the unit has Mo values around 50–100 mg/kg while the lowest part immediately close to footwall (lowest ~0,5 m) is has concentrations of 500 mg/kg and above.

10.6. Precious and Rare Metals In the end of the 1980’s, a study on the content of Au and Pt in black shales was conducted by the atomic absorption method. Anomalously high contents of these elements were found in the shale samples (Au up to 0,94 mg/kg, Pt up to 1,80 mg/kg). Although the number of reliable analyses is still low (Au n = 59, Pt n = 57; earlier reports name higher number), the results indicate a high percentage of anomalous concentrations. The “modern dataset” does not include dedicated Au measurements, but along with other trace element analyses, there are 14 measurements of Au and none of them exceed 0,1 mg/kg. Preliminary correlation analysis of the elements considered

36 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit with the other analysed trace elements and organic content does not indicate specific regularities. Studied core samples were extracted from the bottom half of the cut cores of black shale, and 4 samples were taken from Maardu quarry. A simple statistical analysis of the estimates indicates that the distribution of the contents of Au and Pt in black shales does not obey even a lognormal distribution law. It is worth to note that technological studies of black shale from Maardu quarry indicate an easy physical beneficiation of Au (Petersell et al., 1991). During the black shale exploration, considerable attention was also given to the rare element rhenium (Re). The bulk crustal average concentration of Re in the rock is estimated at 0,19 µg/kg (Rudnick & Gao, 2003 while the maximum recorded values in existing data reach 1,33 mg/kg, indicating significant concentrations of this rare element.

Figure 23. Histograms of Au, Ag, Pt and Re distribution.

37 Geological Survey of Estonia / Research Report EGF-8995

10.7. Condition and Availability of Drill Cores for Sampling A review from the Estonian Land Board database (https://geoportaal.maaamet.ee/est/And- med-ja-kaardid/Geoloogilised-andmed/Puursudamikud/Puursudamike-andmebaas-p382. html) and other resources revealed the possibility of 110 existing cores so there is a lack of drill cores for sampling. The ones that are stored, are mainly associated with the crystalline basement mapping and bear the prefix “F” (Figure 24). Visual inspection revealed that the condition of the cores is variable. However, there are several cores that show minimum signs of weathering/deg- radation/oxidation and therefore have potential for sampling. The currently available cores have been drilled mainly in north-western Estonia. For the purposes of a following study, 11 cores were chosen for geochemical sampling. Defining the actual state and availability of the drill cores must wait until the thorough re-organising process of the drill core facilities is complete (estimated around mid-2019).

Figure 24. An example of an existing half-core-sampled black shale sequence from the borehole F330.

38 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

10.8. Target Area Scenarios The possible scenarios can be divided mainly into two categories or approaches: (1) choosing whether to envisage the exploitation as “independent”, i.e. only black shale would be extracted, or as complex exploitation together with phosphorite or any other potential mineral resource (e.g. limestone, glauconite sandstone); (2) choosing an area following the highest concentration/reserve potential of a valuable component (e.g. vanadium). An example of independent exploitation scenario is discussed in Kulli et al. 2016 in the north-western part of the country, where the black shale deposit is at its thickest (Figure 25). The discussion in the report mainly addresses mining engineering related issues.

480000 490000 500000 510000 520000 E ! AD1 FI _ Pakri poolsaar ! 125

F327 ! 6580000 EE ! SP-4 KL19! D-65 PALDISKI ! ! RU " ! F310 D-53! SP-1 SP-2 SP-3 KL10 !!__! ! KL18 D-138 ! F317 f4 LV ! ! ! KL17! D-66 D-54 117 ! D-46 ! ! ! KEILA " 123 ! D-139 ! 133 D-55 ! f2 ! D-21 ! 130! F331! ! D-47 F312 ! F332 D-33 ! ! 6570000 F331B ! ! ! 358

! D-140 D-22 F321 F318 ! ! ! !D-67 F333 D-34 D-141 ! ! ! Rummu " F316 F325 ! ! F322 D-9 ! L9 ! F335 ! ! ! 7 Padise L11 F334 L10 ! ! 3353 D-109 ! ! ! D-120 F313 D-68 D-115 ! ! ! D-1 D-105 D-107 D-23 ! D-116 D-118 ! ! ! ! ! ! D-108 ! F336 D-114 ! ! D-119 D-121 ! ! ! D-104 D-10 D-106 ! ! D-113 ! D-117 ! ! L3 L2! ! L13 L8 ! ! ! !D-111 ! D-35 ! ! ! ! ! D-160 D-110 L4! ! D-192 L6 F320 F320 L5! F314 321 ! !! ! ! D-36 ! F323 ! F323! ! F337 6560000 ! L12 D-24 ! D-2 D-11 ! ! ! D-179-I F319 ! F330 !

Suursoo ! D-143 D-12 F328 ! F338 ! ! _ D-69 D-144 ! _ D-25 305 ! ! ! A target area scenario in the North-West Estonia 11 Riisipere! ! " F340 3 Mt/y ! ! D-145 F315 ! 5 F339 D-37 f26 ! ! F326! 6 Mt/y ! F324 365 D-26 _ D-48 ! ! f25 D-13 ! ! _ F306 ! ! F341 Black shale occurrence area ! ! Turba 6550000 D-146 " ! ! D-3 F342 Drill cores with average composition collected to DB ! ! D-57 D-38 ! ! N D-49 4 D-14 _ !Locations of cores !and outcrops with "modern data" ! ! Coordinate system: L-EST97 Background topographic map: Estonian Land Board 2019

Since in many areas the black shale directly overlies the phosphorite deposits in Estonia, co-extraction of the two resources has been widely discussed, albeit never put to practice. The most prospective phosphorite deposits coincide with the relatively high concentrations of some metals (particularly V and Mo, Figure 26), making this a strategy worth considering.

39 Geological Survey of Estonia / Research Report EGF-8995

620000 630000 640000 650000 660000 670000 680000 690000 E

Drill core average concentration V (mg/kg) 190 - 480

EE RU 481 - 648 6610000 649 - 821

LV 822 - 1064 1065 - 1600 Phosphorite deposits KUNDA % 6600000 Black shale occurrence area Estonian shoreline

Toolse Aseri 6590000

JÕHVI %

RAKVERE % 6580000

Rakvere Rakvere

6570000 N

Coordinate system: L-EST97

Figure 26. Drill core average V concentrations (“historic” data) in the eastern field of phosphorite deposits (Toolse, Aseri and Rakvere).

The geological cross section of the Toolse phosphorite deposit area is shown in Figure 27 (Adamson et al., 1997). The cover of phosphate rock also includes glauconite sandstone as a potential resource. The limestone in the area is part of the resource (Aru-Lõuna deposit) exploited by Kunda cement factory. One potential exploration scenario is in the Sillamäe region of north-eastern Estonia, where there’s experience in industrial exploitation of black shale along with high concentrations of mineralised rocks (mainly U). The overview of different scenarios and related properties is provided in Table 6.

Figure 27. Geological cross-section of the Toolse phosphorite deposit area (Adamson et al., 1997).

40 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Table 6. Target area scenarios.

Strategy/approach Area Strengths Weaknesses Independent NW Estonia Thick deposit (5-7m) Lower concentrations exploitation of metals Large reserves per land Less developed infra- area structure Dense network of protected areas Low altitude area with large wetlands NE Estonia (3rd or 4th High concentrations of Thin deposit (1-2 m) geochemical zone), e.g. targeted metals Sillamäe Available infrastructure Smaller reserves per and historical experi- land area ence Complex exploitation Toolse Available infrastructure Smaller reserves per together with land area phosphorite High V (+ U, Mo) zone Higher sustainability — Technologically more black shale should complex be excavated anyway (in case of open-pit mining) Aseri High V (+ U, Mo) zone Thinner deposit than Toolse Higher sustainability – black shale should be excavated anyway (in case of open-pit mining) Rakvere Not applicable Black shale pinches out

41 Geological Survey of Estonia / Research Report EGF-8995

11. Mineral Processing Research

Based and modified after a manuscript text by V. Petersell

The origins of black shale processing were solely related to the extraction of U. The first trials were made hurriedly in 1944-45 concurrently with early prospecting of U resources. Several types of selec- tive leaching and extraction methods were trialled with raw as well as roasted shale. Early research was conducted only on Estonian ore, later the studies moved to other ores as well. Many institutes across the Soviet Union were participating in the development of extraction technologies. While the U extraction was generally acknowledged to be feasible, the recoveries rarely exceeded 50% and improvements were found to be arduous. Eventually this led to a conclusion of the process being uneconomic, much like in the case of Sweden’s alum shale.

In the second half of the 20th century, the processing of black shale was investigated at the Institute of Chemistry of the Academy of Sciences and at the Geological Survey of Estonia in the 1970s.

The Institute of Chemistry had started black shale’s complex processing studies already in the 60’s. As a result of various chemical experiments, researchers concluded that the elements U, V, Mo and others could be dissolved out from a slurry of ash in a concentrated sulfuric acid environment (Maremäe, 1989). It was assumed that the firing of shale for energetic purposes is realistic under the fluidized bed conditions (~800 °C), which would also reduce the associated atmosphere contamination. The applicability of burning in the fluidized bed was already established in 1965 (Leene and Ülesoo, 1966). The results of the technological studies at the Institute of Chemistry are described in various publications (Maremäe, 1989, 1988; Maremäe and Kirret, 1989, 1990). The published works do not address the environmental problems associated with converting the material into ash in the fluidised bed. Studies conducted in the chosen direction for nearly 30 years did not yield the expected positive results. The principal investiga- tor, E. Maremäe, notes (Maremäe et al., 1991) that the main drawbacks of the technological scheme are the high concentrations of H2SO4 (400 kg per tonne of ash) and high amounts (81-84% of ash mass) of acidic, radioactive and other types of heavy metals containing waste.

It turned out that there are no prospects for mechanical beneficiation methods. A comparison of the elements of ash and shale, obtained from the fluidized bed conditions for the purposes of clarifying the possibilities of black shale combustion, showed that the majority of Hg, approximately 10% of U and various amounts of other metals are volatile in the fluidized bed (Pihlak et al., 1977). Since at that time, there was no technology available for the entrapping of trace elements from combustion gases and very fine fly ash dust, the approach was discontinued due to the assumed significant environmental impact and the fact that it would likely be uneconomical. Based on the information gathered, the Tallinn Depart- ment of Geological Survey investigated the possibilities of separating metals by chemical methods. The work was done from scratch to clarify the properties of metal leaching and organic matter behaviour in acidic and alkaline environments (Table 7). Coke recoveries in the same experiment series ranged from 83 – 87,5 %, while the oil recovery is highest at 7,5 % in 10 % NaOH solution (T = 370 °C; P = 250 - 300 atm; t = 4 h). Under the same conditions, U, Mo and V leaching into solution is stopped.

42 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

Table 7. Recoveries of U, Mo, and V leaching in various media and conditions.

Sample Media U Mo V

mg/kg mg/kg mg/kg Recovery Recovery Recovery Dry Dry Dry Residue % Residue % Residue % residue residue residue

Concentration in ini- 135 253 970 tial material (mg/kg)

To = 20°C, P – ambient; time 4 h

D-1.1 H2O 126** 7 200 3 21 900 20 7 D-1.2 NaOH 5% 101 25 43 2140 83 831 1070 14

D-1.3 H2SO4 5% 89 34 268 90 ? 834 730 14 D-1.4 HCl 5% 94 33 210 60 17 1110 200 -

D-1.5 HNO3 5% 106 22 240 6 5 929 200 4

To = 100°C, P – ambient; time 4 h

D-1.1 H2O 111 29 18 200 15 21 1000 6 ? D-1.2 NaOH 5% 116 29 14 23 2340 91 741 1200 24

D-1.3 H2SO4 5% 83 39 290 15 ? 834 460 14 D-1.4 HCl 5% 99 27 234 15 8 834 460 14

D-1.5 HNO3 5% 96 34 29 253 10 ? 834 400 14

T = 370°C; P = 250 - 300 atm; time = 4 h

D-1.1 H2O 131 8 3 232 0,6 7 1088 <3 ? D-1.2 NaOH 5% 137 ? 241 3 4 750 6 23

D-1-3 H2SO4 5% 133 ? 238 0,6 5 1062 <3

Most of the elements listed in the table are determined by the semi-quantitative spectral analysis. It is notable that Mo went almost completely to solution with 5% NaOH leaching at a temperature of 100 °C (Petersell et al., 1979) and that V recovery factors remain very low under all tested conditions.

An unconventional bioleaching method is currently being developed that attempts to create both methane gas as well as leach metals from the shale by disintegrating the metal porphyrins. The process takes place by utilising a selected bacterial community from the black shale itself (Menert et al., 2017; Sipp Kulli et al., 2016, 2014). The technological flowsheet is divided in two principal steps: (1) Biogenic methane production in anaerobic atmosphere with simultaneous release of certain organic-bound metals (called the Graptomet 1); (2) Aerobic bioleaching of sulphide-bound metals (called the Graptomet 2).

The process takes place at a temperature of 37 °C and at atmospheric pressure conditions.

43 Geological Survey of Estonia / Research Report EGF-8995

The efficiency of the production of methane can be regarded being high, with a maximum production of 14,5 l of methane per 1 kg of shale. The bioleaching of metals is still in development, progress so far has yielded relatively low recoveries (Figure 28).

Figure 28. Recoveries (%) of some of the metals in the bioleaching technology (Sipp Kulli et al., 2016).

There was a patent (WO2017140324A1) filed for this technology in 2016 (Menert et al., 2017). To the authors’ knowledge, no technological upscaling tests have been completed but the work is ongoing.

44 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

12. Environmental Considerations

Black shale is a natural source of radiation and an emitter of radon (Rn) since it contains uranium and potassium. In areas near black shale outcrops and shallow occurrences, Rn emission is being moni- tored from a public health point of view (Petersell et al., 2017; Petersell and Åkerblom, 2005). Because of naturally occurring processes, heavy and other potentially harmful elements can be released to soil, ground water etc. (Hade et al., 2017).

Black shale, due to its sulphide content (mainly pyrite) is susceptible to oxidation in aerated conditions. Oxidation of the shale can release heavy elements to the environment as potential pollutants. The possible environmental impact is caused due to the complex effects of the presence of oxygen, sulphide minerals, water and microbial communities.

12.1. Groundwater Black shale (graptolite argillite, Türisalu formation) belongs to the Ordovician-Cambrian aquifer system, which represents an important water supply. As a fine-grained argillaceous rock, black shale behaves as a local aquitard and therefore protects the underlying aquifer system. Due to the reasons of groundwater protection, the in situ processing of the Estonian black shale is considered unfavourable (Sipp Kulli et al., 2016, 2014).

12.2. Regional Aspects For various reasons, the eastern part of the country is likely to be more flexible with regards to environmental restrictions compared to western Estonia. The eastern part (especially northeast) of the country has the most technogenic landscape in Estonia as a result of over 100 years of oil shale mining (http://www.ene.ttu.ee/maeinstituut/mgis/mapofhistory.htm). In comparison, the north-western part of the country is quite densely populated with various protected areas, although a report by (Sipp Kulli et al., 2016) discusses a possible mining area near Paldiski (see section 10.8 and Figure 25).

45 Geological Survey of Estonia / Research Report EGF-8995

13. Marketing Considerations

At this stage of exploration, it would be very hypothetical to speak about the value and profitability of the deposit. Mainly because 1) we are reviewing the complete deposit in Estonia and in case of exploitation, only a minor fraction would be used, and most importantly 2) the processing technology is not developed. The latter is also one of the main conclusions of the coherent BiotaTec (formerly BiotaP) preliminary economic assessment (recommended literature on this topic, albeit in Estonian) for understanding the marketing considerations in depth (Sipp Kulli et al., 2016).

However, in the recent years the proportions of different black shale valuable components have changed significantly, and the main mineral of interest from all the metallic compounds is likely vanadium (Figure 29).

Value distribution Figure 29. An approximate value distribution of the main metallic components within the Estonian black shale deposit. 8% 7% 1% Molybdenum Uranium Zinc Vanadium

84%

The preliminary economic assessment of the black shale exploitation by the means of bioleaching considered the vanadium pentoxide price at 19 640 USD/t (31.08.2016), while the current pentoxide price is at 61 619 USD/t (21.11.2018), thus showing a three-fold increase in the given period.

46 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

14. Conclusions

The existing exploration data points out that the Estonian black shale deposit represents an important resource for several commodity metals (V, U, Mo, Pb, and potentially others) with additional value in the organic matter. Choosing a specific exploration target or a set of targets requires outlying requirements from the developer and combining them with existing data. From a geological and exploration perspective, the follow-up investigations should be relatively easy to perform. The black shale deposit has a simple geometry and it is buried under a shallow cover. Based on a review of existing information, the established metal occurrence patterns make it easy to target prospective areas for further exploration. The existing information can be used to isolate parts of the deposit with high metal concentrations, de- fine anomalies and increase the drilling grid in areas of interest.

MoO3, 6,7 megatonnes for U3O8 and 88,0 megatonnes for V2O5.

Further research is required to develop methods of extracting valuable compounds with maximum recovery factor while causing minimal environmental impact. Currently, there is no defined up-to-date extraction technology available and the adaptation of existing methods (e.g. the Ranstdad technology, the Talvivaara type bio-heapleaching, etc) has either not been trialled or been tested only in lab scale.

47 Geological Survey of Estonia / Research Report EGF-8995

15. Recommendations

A few important steps that should be prioritised for the purposes of successful exploration of the Estonian black shale deposit: (1) Even if retrieved with outdated technical capabilities, all possible black shale exploration data should be collected into a digital database to facilitate a flexible and efficient search for exploration targets; (2) Drilling campaigns, if initiated, should attempt to verify the existing information with up-to- date techniques; (3) It is necessary to speciate the occurrence forms of the economically important metals (V, U, Mo, …) prior to metallurgical tests. (4) Metallurgical tests are unavoidable to better understand the exploitability of the deposit; this does not necessarily require drilling as representative material can be collected from outcrops.

48 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

16. References

Adamson, A., Reinsalu, E., Juuse, L., Valgma, I., 1997. Sustainable phosphate rock mining, in: Proceedings of the Estonian Academy of Sciences, Engineering. Estonian Academy Publishers, pp. 13–22.

Andersson, A., 1985. The Scandinavian alum shales. Sveriges geologiska undersökning.

Bhatti, T.M., 2015. Bioleaching of organic carbon rich polymetallic black shale. Hydrometallurgy 157, 246–255. https://doi. org/10.1016/j.hydromet.2015.08.012

Desjardins, J., 2017. Vanadium: The Energy Storage Metal [WWW Document]. Vis. Capital. URL https://www.visualcapitalist. com/vanadium-energy-storage-metal/ (accessed 12.15.18).

Gouin, J., Augé, T., Bailly, L., D’Hugues, P., Disnar, J.R., Keravis, D., 2015. Characteristics of Kupferschiefer ore from Lubin mine (Poland): mplications for bioleaching of the ore. Presented at the 9th SGA biennial.

Hade, S., 2014. GIS Applications in the Studies of the Palaeozoic Graptolite Argillite and Landscape Change (PhD Thesis). Tallinn University of Technology, Tallinn.

Hade, S., Soesoo, A., 2014. Estonian graptolite argillites revisited: a future resource? Oil Shale 31, 4–18.

Hade, S., Voolma, M., Soesoo, A., 2017. The model of the environmental impact of the heavy and other elements contained in the Estonian graptolite argillite and their leaching dynamics (No. 10224). Institute of Geology, Tallinn University of Technology; Environmental Investment Centre, Tallinn.

Heinsalu, H., Kaljo, D., Kurvits, T., Viira, V., 2003. The stratotype of the Orasoja Member (Tremadocian, Northeast Estonia): lithology, mineralogy, and biostratigraphy/Orasoja kihistiku (Tremadocian, Kirde-Eesti) stratotuup: litoloogia, minera loogia ja biostratigraafia, in: Proceedings of the Estonian Academy of Sciences: Geology. Estonian Academy Publish- ers, pp. 135–155.

Hints, R., Hade, S., Soesoo, A., Voolma, M., 2014a. Depositional framework of the East Baltic Tremadocian black shale revisited. GFF 136, 464–482. https://doi.org/10.1080/11035897.2013.866978

Hints, R., Soesoo, A., Voolma, M., Tarros, S., Kallaste, T., Hade, S., 2014b. Centimetre-scale variability of redox-sensitive elements in Tremadocian black shales from the eastern Baltic Palaeobasin. Est. J. Earth Sci. 63, 233–239. https://doi.org/10.3176/earth.2014.24

Institute of Geology, Tallinn University of Technology, 2011. The Geology, Rocks and Mineral Resources of Estonia [WWW Doc- ument]. URL https://www.ttu.ee/public/g/Geoloogia_instituut/Oppematerjal/kollektsiooni_lisamaterjal.pdf (accessed 2.18.19).

Jüriado, K., Raukas, A., Petersell, V., 2012. Alum shales causing radon risks on the example of Maardu area, North-Estonia. Oil Shale 29, 76–84.

Kiipli, T., Batchelor, R.A., Bernal, J.P., Cowing, C., Hagel-Brunnstrom, M., Ingham, M.N., Johnson, D., Kivisilla, J., Knaack, C., Kump, P., 2000. Seven sedimentary rock reference samples from Estonia. Oil Shale 17, 215–224.

Kosakowski, P., Kotarba, M.J., Piestrzyński, A., Shogenova, A., Więcław, D., 2017. Petroleum source rock evaluation of the Alum and Dictyonema Shales (Upper Cambrian–Lower Ordovician) in the Baltic Basin and Podlasie Depression (eastern Poland). Int. J. Earth Sci. 106, 743–761. https://doi.org/10.1007/s00531-016-1328-x

Lecomte, A., Cathelineau, M., Michels, R., Peiffert, C., Brouand, M., 2017. Uranium mineralization in the Alum Shale Formation (Sweden): Evolution of a U-rich marine black shale from sedimentation to metamorphism. Ore Geol. Rev. 88, 71–98. https://doi.org/10.1016/j.oregeorev.2017.04.021

Leene, R., Ülesoo, R., 1966. Experimental studies of the combustion process of dictyonema shale in a fluidized bed (in Rus- sian). Shale Chem. Ind. 19,23.

Lippmaa, E., Maremae, E., 2000. Uranium production from the local Dictyonema shale in North-East Estonia. Oil Shale 17, 387–394.

Lippmaa, E., Maremäe, E., Pihlak, A.-T., 2011. Resources, production and processing of Baltoscandian multimetal black shales. Oil Shale 28, 68–77.

Loog, A., Kurvits, T., Aruvali, J., Petersell, V., 2001. Grain size analysis and mineralogy of the Tremadocian Dictyonema shale in Estonia. Oil Shale 18, 281–297.

Loog, A., Petersell, V., 1995. Authigenic siliceous minerals in the Tremadoc graptolitic argillite of Estonia, in: Proc. Est. Acad. Sci. Geol. pp. 26–32.

Loog, A., Petersell, V., 1994. The distribution of microelements in Tremadoc graptolitic argillite of Estonia. Acta Comment. Univ. Tartu. 57–75.

49 Geological Survey of Estonia / Research Report EGF-8995

Loukola-Ruskeeniemi, K., 1992. Geochemistry of Proterozoic metamorphosed black shales in eastern Finland: with implica- tions for exploration and environmental studies (PhD Thesis). Geologian tutkimuskeskus, Espoo.

Loukola-Ruskeeniemi, K., Lahtinen, H., 2013. Multiphase evolution in the black-shale-hosted Ni–Cu–Zn–Co deposit at Talvi vaara, Finland. Ore Geol. Rev., Hydrothermal nickel deposits: Secular variation and diversity 52, 85–99. https://doi. org/10.1016/j.oregeorev.2012.10.006

Maremäe, E., 1989. The problem of the integrated use of Estonian dictyonema shale as a raw material for metallurgy. Oil Shale 6, 28–36.

Maremäe, E., 1988. The question of the possibilities of using Estonian dictyonema shales in the national economy (in Russian). Oil Shale 5, 407–418.

Maremäe, E., Kirret, O., 1989. The decomposition of dictyonema shale ash by sulfuric acid with a large amount of liquid phase. Oil Shale 6, 354–361.

Maremäe, E., Kirret, O.G., 1990. Decomposition of alum shale ashes with sulphuric acid at a low liquid phase content. Oil Shale 7, 59–65.

Maremäe, E., Ründal, L., Ahelik, V., 1991. Study of the process of multistage leaching of alum shale’s sulphated ashes. Oil Shale 8, 27–38.

Menert, A., Kivisaar, M., Sipp Kulli, S., Heinaru, A., Maidre, T., 2017. Method for decomposition of the metallorganic matter of graptolite-argillite by microbial consortium. WO2017140324A1.

Ministry of the Environment, Republic of Estonia, 2017. General principles of Earth’s crust policy until 2050 [WWW Document]. URL https://www.envir.ee/sites/default/files/mpp_2050_kujundatud_eng.pdf (accessed 12.12.18).

Niin, M., Rammo, M., Saadre, T., 2008. Estonian Mineral Resources Map. Dictyonema Shale (Graptolite Argillite). Scale 1:400000 (printed), 1:200000 (digital), + Explanatory Note.

Pattinson, D., Dendle, J., Campodonic, M., Armitage, M., Skelton, R., Cessford, F., Joslin, K., 2013. A summary technical report on the Talvivaara mine, Finland. SRK Consulting (UK) Limited.

Peacor, D.R., Coveney, R.M., Zhao, G., 2000. Authigenic Illite and Organic Matter: The Principal Hosts of Vanadium In The Mecca Quarry Shale at Velpen, Indiana. Clays Clay Miner. 48, 311–316.

Petersell, V., 1997. Dictyonema argillite, in: Raukas, A., Teedumäe, A. (Eds.), Geology and Mineral Resources of Estonia. Estonian Academy Publishers, Tallinn, pp. 313–326.

Petersell, V., Åkerblom, G., 2005. Radon risk Map of Estonia: explanatory text to the radon risk map set of Estonia at scale of 1: 500 000. Eesti Geoloogiakeskus (Geological Survey of Estonia).

Petersell, V., Güsson, J., Larionov, A., Reiman, I., 1979. Geological and economic assessment and technological studies of phosphate rock as a complex mineral raw material (No. EGF3584). Tallinn.

Petersell, V., Kivisilla, J., Pukkonen, E., Põldvere, A., Täht, K., 1991. Evaluation of Ore Events and Mineralization Points in Estonian Bedrock and Crystalline Basement (EGF identifier 4523). Geological Survey of Estonia, Tallinn (in Russian).

Petersell, V., Täht-Kok, K., Karimov, M., Milvek, H., Nirgi, S., Raha, M., Saarik, K., 2017. Radon in the soil air of Estonia. J. Environ. Radioact., Special Issue on Geogenic Radiation and its Potential Use for Developing the Geogenic Radon Map 166, 235–241. https://doi.org/10.1016/j.jenvrad.2016.08.004

Pihlak, A.A., Petersell, V., Liivrand, H.I., 1977. Preparation of the materials for the design of a pilot plant for the processing of argillite from phosphorite deposits in the Estonian SSR (in Russian) (No. EGF3479). Geological Survey of Estonia, Keila.

Pukkonen, E., Rammo, M., 1992. Distribution of molybdenum and uranium in the Tremadoc Graptolite Argillite (Dictyonema Shale) of north-western Estonia. Bull. Geol. Surv. Est. 2, 3–15.

Puura, E., Neretnieks, I., 2000. Atmospheric oxidation of the pyritic waste rock in Maardu, Estonia, 2: an assessment of aluminosilicate buffering potential. Environ. Geol. 39, 560–566.

Puura, E., Neretnieks, I., Kirsimäe, K., 1999. Atmospheric oxidation of the pyritic waste rock in Maardu, Estonia. 1 field study and modelling. Environ. Geol. 39, 1–19.

Rammo, M., Vaher, R., Morozov, O., Uusmaa, A., Dantshenko, V., Radik, E., Morozova, L., Beljajev, B., Popova, S., 1989. Phos- phorite exploration south-west from Maardu (O-34-XII, O-35-I, VII) y. 1986.-1989 (No. EGF4359). Geological Survey of Estonia (in Russian), Tallinn.

Revee, P., 2018. New resource estimate – Häggån battery metals project. Aura Energy Limited.

Revee, P., 2017. Developing high margin uranium.

Riekkola-Vanhanen, M., 2013. Talvivaara mining company – From a project to a mine. Miner. Eng., Biohydrometallurgy 48, 2–9.

50 Review of the Exploration Potential of the Estonian Black Shale (Graptolitic Argillite) Deposit

https://doi.org/10.1016/j.mineng.2013.04.018

Schovsbo, N.H., 2002. Uranium enrichment shorewards in black shales: A case study from the Scandinavian Alum Shale. GFF 124, 107–115. https://doi.org/10.1080/11035890201242107

Sipp Kulli, S., Menert, A., Kamenev, I., Reinsalu, E., Maidre, T., BiotaP OÜ, 2016. Preliminary economic assessment of the extraction of methane gas from the Estonian argillite. BiotaP OÜ, Tallinn.

Sipp Kulli, S., Menert, A., Kivisaar, M., Maidre, T., Rander, A., Lillo, J., 2014. A study of the possibility of the production of biogenic methane gas from Estonian argillite within a well (in situ). BiotaP OÜ, Tallinn.

Soesoo, A., Hade, S., 2014. Black shale of Estonia: moving towards a Fennoscandian-Baltoscandian database. Труды Карельского Научного Центра Российской Академии Наук 103–114.

Szubert, A., Sadowski, Z., Gros, C.P., Barbe, J.M., Guilard, R., 2006. Identification of metalloporphyrins extracted from the copper bearing black shale of Fore Sudetic Monocline (Poland). Miner. Eng., Featuring selected papers presented at Process Systems for the Metallurgical Industries ’05 symposium, Cape Town, South Africa 19, 1212–1215. https://doi. org/10.1016/j.mineng.2005.11.007

Tarros, S., 2013. Multidimensional statistical analysis of trace element distribution patterns in graptolite argillite from Suur-Pakri cross-sections (PhD Thesis). University of Tartu, Tartu.

Vaughan, D.J., Sweeney, M.A., Friedrich, G., Diedel, R., Haranczyk, C., 1989. The Kupferschiefer; an overview with an appraisal of the different types of mineralization. Econ. Geol. 84, 1003–1027. https://doi.org/10.2113/gsecongeo.84.5.1003

Veski, R., Palu, V., 2003. Investigation of Dictyonema Oil Shale and Its Natural and Artificial Transformation Products by a Vankrevelenogram. Oil Shale 20, 265–281.

Voolma, M., Soesoo, A., Hade, S., Hints, R., Kallaste, T., 2013. Geochemical heterogeneity of Estonian graptolite argillite. Oil Shale 30, 377–401. https://doi.org/10.3176/oil.2013.3.02

Włodarczyk, A., Stasiuk, R., Skłodowska, A., Matlakowska, R., 2015. Extracellular compounds produced by bacterial consortium promoting elements mobilization from polymetallic Kupferschiefer black shale (Fore-Sudetic Monocline, Poland). Chemosphere 122, 273–279. https://doi.org/10.1016/j.chemosphere.2014.11.073

51 Geological Survey of Estonia / Research Report EGF-8995

APPENDIX 1

Glossary of Terms

AAS chemical analyses technique sensitive to trace amounts of chemical elements — Atomic Absorption Spectroscopy black shale a fine-grained shale type of sedimentary rock that is rich in organic content as well as sulphides e.g. pyrite box and whisker plot a statistical distribution diagram, where the middle horizontal line denotes median of the sample population, edges of the boxes denote the 25th and the 75th quartile and tips of the whiskers mark 5th and 95th quartiles; in the diagrams shown in current report the crosses mark minimum and maximum values calorific value the energy contained in a material continental glacier large ice glacier that covered vast regions in the Northern Hemisphere during the ice ages dictyonema shale out-dated local term for the Estonian black shale that refers to the mistakenly identified “dictyonema” fossils glacial till glacial sediment that contains unsorted sediment particles in all sizes glauconite sandstone sandstone rich in the mineral glauconite that gives the rock a greenish colour; a potential K-rich mineral resource graptolite argillite a local (Estonian) term denoting black shale; refers to the relative (although debatable) abundance of “graptolite” fossils and the fine-grained aluminosilicate-abundant (argillaceous) nature of the rock

ICP-MS/OES chemical analyses techniques sensitive to (ultra)trace amounts of chemical elements — Inductively Coupled Plasma Mass Spectrometry / Optical Emission Spectroscopy

Obolus sandstone sandstone rich in the fossil brachiopod “Obolus” shells that in terms of mineral resources is a phosphate resource oil shale organic-rich sedimentary rock that is exploited for energetic purposes

Optical Character Recognition electronic conversion technique that converts scanned text/numbers into a digital format for further processing

Tukey boxplot a similar statistical distribution map like box and whisker plot, but the upper and lower whiskers are calculated as 1,5 times the interquartile range (difference between 25th and 75th percentile) and minus 1,5 times the interquartile range; the remaining plotted values are the near outliers (crosses) and far outliers (circles)

WD-XRF chemical analyses technique — Wavelength Dispersive X-Ray Fluorescence Spectroscopy