GPR survey and field work summary in Siilinjärvi Mine during July 2014 Samrit Luoma, Juha Majaniemi, Tiina Nurminen, and Antti Pasanen

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1 GEOLOGICAL SURVEY OF FINLAND Southern Finland Office Espoo 74/ GPR survey and field work summary in Siilinjärvi Mine during July 2014 Samrit Luoma, Juha Majaniemi, Tiina Nurminen, and Antti Pasanen

2 GEOLOGICAL SURVEY OF FINLAND GEOLOGICAL SURVEY OF FINLAND DOCUMENTATION PAGE Date / Rec. no. Authors Samrit Luoma, Juha Majaniemi,Tiina Nurminen and Annti Pasanen Type of report Archived Report Commissioned by WaterSmart Project Title of report GPR survey and field work summary in Siilinjärvi Mine during July 2014 Abstract Total 41 km of GPR survey lines were performed in the Yara Suomi Oy Siilinjärvi Mine in order to determine the bedrock surface, and the structure of Quaternary sediments in mining area by integrating GRP data with geological and field investigation data. Bedrock surface elevation varies between to m a.s.l. with mean value of m a.s.l, and forms a sharp contact to the overlying Quaternary sediment. An overall fracture directions of bedrock are 311, 0, and 18, follow a relatively broad deep fracture zone, which is located in the direction NW- SE. Thickness of Quaternary sediment is thin, varies between 1.05 m to 17.7 m with mean thickness of 2.30 m and mainly consists of fine-grained till covers approximately 60.0 % of total area, while 13.8% is surface water. Fine-grained sediments such as clay, silt and peat distribute sporadically along the watercourse area and in valleys close to lakes, cover approximately 8.3 % of total area. Fined-grained till and fine-grained sediments have generally low permeability, which may provide a low infiltration rate of water in to the ground. Keywords Ground Penetrating Radar, GPR survey, Siilinjärvi, Quaternary deposit, bedrock deposit Geographical area Siilinjärvi, East-Finland, Finland Map sheet , Other information Report serial - Archive code 74/2014 Total pages 40 Language English Price - Confidentiality Public Unit and section ESY, Land Use and Environment (VA212), Espoo Signature/name Project code Water Smart Project Signature/name Samrit Luoma

3 GEOLOGICAL SURVEY OF FINLAND Contents Documentation page 1 INTRODUCTION 1 2 STUDY AREA 2 3 GEOLOGY OF THE STUDY AREA 2 4 METHODS GPR survey and interpretation Interpolations 7 5 RESULTS AND DISCUSSIONS GPR Interpretation Bedrock surface Quaternary deposit 11 6 SUMMARY 12 7 REFERENCES 13 APPENDIX 1: INTERPRETED GPR PROFILES 16 APPENDIX 2: PHOTOGRAPHS FROM FIELD WORK IN SIILINJÄRVI MINE DURING

4 GEOLOGICAL SURVEY OF FINLAND 1 1 INTRODUCTION WaterSmart Project (Management of water balance and quality in mining areas), is a two-year project ( ) that is with the part funding from Tekes. The goal of the project is to improve the awareness of actual quantities of water, and water balances in mine areas to give possibility to forecast the amounts of water in future, with the main efforts are to exploit on-line water quantity and water quality measurements, to develop mathematical models used to calculate water balance, and to sort out how the monitoring and modelling tools can be integrated into the management system and process control. GTK's responsibility is on WP2 for the data collection and monitoring of the geological and hydrogeological parameters that have to be collected manually. This report is one of the results from the WP2 by providing a summary and interpretation of data from field investigation in the Siilinjärvi Mine area during The objective of this study is to determine the bedrock surface topography, the characteristics of the Quaternary sediment based on the Ground Penetrating Radar (GPR) survey and the available hydrogeological data. GPR was selected because of its non-intrusive acquisition that can be performed in the area that the use of intrusive methods is not allowed. GPR is one of the main geophysical methods that can be used to classify the sediment types by confirmation of data from a controlled well and also indicate the internal structure of sedimentary deposit in the study area. GPR is based on a pulse of electromagnetic energy is transmitted into the subsurface. The energy is reflected back from the electrical boundaries and the amplitudes and the two-way travel time in nanoseconds is recorded. The electrical boundaries are created at the interfaces of the geological materials with different dielectrical properties (Parsanen 2009; Hänninen 1991). The radar energy is reflected due the change in dielectrical properties and electrical conductivity. The differences in dielectrical properties are mainly caused by changes in water content, lithology and material density (Hänninen 1991). For the porous and dry material such as sand layers the depth of investigation of GPR could reach about 100 m deep and in most cases the average depth of investigation ranges between m. However, in material that has high conductivity such as clay or high conductive groundwater, the GPR does not work well. The information of bedrock surface, bedrock geology, Quaternary sediment, groundwater level, and hydrogeological parameters received from the field investigation will be used for the groundwater flow models and the study of interactions between surface water and groundwater

5 GEOLOGICAL SURVEY OF FINLAND 2 in the catchment area. These data are important for developing a better understanding of the occurrence and flow system of groundwater in the study area, groundwater discharge conditions and its interaction to the surface water, e.g. streams, rivers, lakes and wetlands, which are useful information for the water balance modelling and water management and planning in the mining area. 2 STUDY AREA The Siilinjärvi Mine, the largest open pit mine in Finland, is located in the eastern of Finland, approximately 400 km north of Helsinki and 28 km north-eastern of Kuopio (Figure 1). The Siilinjärvi Mine is a phosphate mine from the Siilinjärvi carbonatite complex (Puustinen, 1971). Open pit mine for phosphorus ore was commissioned in Present production at the Siilinjärvi mine is about 9.2 Mt of ore per annum from the operations of two open pits: Särkijärvi in the south and Saarinen in the north-eastern of the mining area. The mining area consists of two tailings Musti and Raasio locate in the northern of mine. The bulk of the tailings material is discharged and pumped into the tailings ponds of Musti, Raasio and Jaakonlampi. Water from these ponds and the drainage water from the open pit are recirculated to the concentration plant. The surplus water is treated with water purification chemicals and adjusted to ph 7 before release to the nearby lake. The rock/overburden and gypsum piles locate around the Särkijärvi open pit area, while the calcine pile locates nearby the factory, south of the open pit. Based on LiDAR data, the topographic elevation in the study area varies between 84.0 m a.s.l. and m a.s.l. with the mean value of m a.s.l. The topography decreases from north to south (Figure 2) in valleys close to the lakes. 3 GEOLOGY OF THE STUDY AREA Bedrock deposit in the study area consists of the Siilinjärvi carbonatite complex with age about million years and is one of the oldest carbonatite deposits in the world with in situ grade 4.2% phosphate (P 2 O 5). The deposit mainly consists of three rocks: phlogopite- and apatite-rich glimmerite, syenite and carbonate-rich carbonatite. The apatite bearing host rocks consist of a steeply dipping lenticular body roughly 16 km long, up to 650 m width, with a maximum depth of 1.5 km and a surface area of 14.7 km 2 (Figure 3). The Quaternary deposit overlying the Precambrian bedrock mostly consists of basal meltout till in the mining area and fine-grained sediments of silt and clay in the south around the lakes (Figure 4).

6 GEOLOGICAL SURVEY OF FINLAND 3 Figure 1. Location map of the study area in the Siilinjärvi Mine - Yara Suomi Oy. Basemaps: National Land Survey of Finland. 4 METHODS The study comprises of two parts: 1) field investigation with the GPR survey, GPR data processing and interpretation, and 2) interpretations of bedrock surface, Quaternary thickness and hydrogeological data. Data used for the survey and interpretations consist of bedrock map scale 1: , Quaternary geologic map scale 1:20 000, LiDAR topographic map data, well information data including groundwater level, sediment description and geochemical analysis data are received from Yara Suomi Oy.

7 GEOLOGICAL SURVEY OF FINLAND 4 Figure 2. Topographic elevation LiDAR map of the Siilinjärvi Mine area. Basemaps: National Land Survey of Finland.

8 GEOLOGICAL SURVEY OF FINLAND 5 Figure 3. Bedrock geological map of the Siilinjärvi Mine area. Bedrock deposit database Geological Survey of Finland.

9 GEOLOGICAL SURVEY OF FINLAND 6 Figure 4. Quaternary geological deposit in the Siilinjärvi Mine area. Quaternary deposit database Geological Survey of Finland and Basemaps: National Land Survey of Finland.

10 GEOLOGICAL SURVEY OF FINLAND GPR survey and interpretation The GPR survey was conducted during 8-18 July 2014 by using the Malå - Ramac ProEx Tough Terrain with 25 and 100 MHz frequency antennae. The global positioning system (GPS) device was used for the horizontal positioning. A total of 41 km long from 47 GPR survey lines was carried out throughout the main geological deposits and mining activities areas in the Yara Oy Siilinjärvi Mine including tailings, gypsum pile, calcine pile areas, and rock/overburden dumping areas (Figure 5). The GPR data processing and interpretation were done in the GeoDoctor (version 2.546) software. The data processing consists of the filtering to reduce noises; topographic correction to compensate for changes in surface elevation, and depth conversion. Data from drilled wells such as top bedrock, descriptions of sediments, groundwater level and chemical analysis of groundwater were used for the calibration and interpretation of the GPR data. The 100 MHz antenna provides a better balance between the penetration depth and vertical resolution. Thus, the data set from 100 MHz antenna was interpreted and presented in this report. The interpretation results consist of top bedrock, and if the radar profile quality look compromised, the internal structure of the Quaternary sediment that overlain the top bedrock surface. 4.2 Interpolations Top bedrock surface elevation map Top bedrock surface elevation map was produced from the interpolation of the top bedrock data points from various data including top bedrock from GPR data, drilled well, outcrop, and bedrock polygon data from the Quaternary geological map scale 1: The data points were first interpolated using kriging with 5 m grid size for the whole study area using the ArcMap (version 10.1). The interpolated surface was calibrated with those top bed rock data points (the control points). For the interpolated surface areas that are shallower than the control points, the interpolated data was replaced by the control points and the top bed rock surface was reinterpolated using inverse distance weighting (IDW) method in the ArcMap program. Quaternary thickness map The Quaternary thickness map was calculated from the subtraction of the topographic map by the bedrock surface elevation map. The topographic map used was LiDAR 2mx2m grid, which

11 GEOLOGICAL SURVEY OF FINLAND 8 was re-gridded into 5 m grid size in order to preserve the same grid size with the top bedrock surface. The distributions of the Quaternary sediments were interpolated based on the data from drilled well, soil samples, outcrop and the Quaternary geologic map scale 1: from map sheet number , (Huttunen, 2002; 2000). The sediments data provide important information on the hydrogeological characteristics, e.g. number layers of an existing aquifers (sand, gravel), aquitards (fine-grain sediments, e.g. clay, silt, till), estimate percolation time and infiltration rate of water from surface in to groundwater table based on the hydraulic properties of those sediments. 5 RESULTS AND DISCUSSIONS 5.1 GPR Interpretation GPR survey lines throughout the study area are shown in Figure 5. The interpretations of ground surface and top bedrock surface in each survey line as shown in Figures A1-1 to A1-3. The GPR survey was conducted successfully in most areas and with the calibration from the top bedrock from well data, the bedrock surface can be identified (e.g. Figures 6&7). However, in some particular areas such as in the calcine pile and the gypsum pile areas, GPR survey lines show no reflection of radar profiles (Figure 8). Wells data in gypsum pile area indicate the Quaternary sediment is mainly clay. Both in the calcine pile and the gypsum pile areas contain high EC values groundwater up to 1040 ms/m and 428 ms/m, respectively. Data acquisition and quality of GPR is limited by high conductive media, e.g. clay layer and high conductivity water content. High EC values in groundwater and sediment can cause no reflection in the radar profiles. Top bedrock elevation from wells and outcrop data were used for the bedrock surface interpolation. 5.2 Bedrock surface Bedrock surface elevation in the Siinlinjärvi Mine area (excluded tailings, rock piles and quarry areas) varies between to m a.s.l. with mean value of m a.s.l (Figure 9). Bedrock topography decreases from north to south, follows the topographic elevation. The topographic gradient of the bedrock surface between the north around the Syrjänlampi and the south around the Sulkavanjärvi is approximately to Bedrock surface has a sharp contact with the overlying Quaternary sediment and in most places the bedrock expose contains high fractures (Appendix 2). No fault zones were observed from the GPR profiles, however, based on the rock exposed in the open pits, interpretation of geophysical data, and bedrock geo

12 GEOLOGICAL SURVEY OF FINLAND 9 Figure 5. Map presenting the GPR survey lines in Siilinjärvi Mine area during July Detailed maps of the GPR survey lines in the different areas are presented in Appendix 1.

13 GEOLOGICAL SURVEY OF FINLAND 10 Figure 6. GPR profile from survey line 632 along the west boundary of rock pile, south of the Raisio tailing. Red dots represent interpreted bedrock surface. Figure 7. GPR profile along the survey line 73, south-east of Siko-artificial lake. Red dots represent interpreted bedrock surface.

14 GEOLOGICAL SURVEY OF FINLAND 11 Figure 8. GPR profile along the survey line 56, north of the gypsum pile. 325, and 12-22, with an overall fracture directions: 311, 0, and 18, follow a relatively broad deep fracture zone is located in the direction NW- SE. The fracture direction (311 ) is approximately the same as the most common direction of the Quaternary continental ice movements. This fact obviously increases the apparent frequency of this direction since fractures in this direction would have been more easily hollowed out by the moving ice (Puustinen, 1971). Based on those data the fault zones can be observed following the directions of streams, creeks and lakes trends (Figure 9). 5.3 Quaternary deposit Thickness of Quaternary sediment varies between 1.05 m to 17.7 m with mean thickness of 2.30 m (Figure 10). The Quaternary deposit mainly consists of fine-grained till from basal melt out till occupies approximately 60.0 % of total area, while 13.8% is surface water (stream, rivers and lakes) and 11.1 % is bedrock exposed (Figure 4). Fine-grained sediments such as clay, silt and peat distribute sporadically along the watercourse area and in valleys close to lakes, cover approximately 8.3 % of total area. Based on wells data, many places fine-grained layers overly the fined-grained till. The thickness of fine-grained layers varies between less than one meter to 17.8 m, with mean thickness of 1.70 m. The thickest clay layer deposits in south of the Sul-

15 GEOLOGICAL SURVEY OF FINLAND 12 kavanjärvi lake. Fined-grained till and fine-grained sediments have generally low permeability ( m/d), which may provide a low infiltration rate of water in to the ground. This is probably can be observed also from the existing of rainwater on ground surface for few days after raining (Appendix 2) 6 SUMMARY This report summarizes the results of the GPR survey and field work during July 2014 in the Yara Suomi Oy - Siilinjärvi Mine, where the 41 km of GPR survey lines were performed throughout the mine area. Top bedrock information from GPR survey was integrated with geological data and well data to identify the bedrock surface elevation, which later on these data will be used for the geological and groundwater flow modelling of this area. Bedrock surface elevation varies between to m a.s.l. with mean value of m a.s.l. Bedrock topography decreases from north to south, follows the topographic elevation. Bedrock surface has a sharp contact with the overlying Quaternary sediment. The bedrock expose covers approximately 11.1% of total area and contains high fractures. No fault zones were observed from the GPR profiles, however, based on the rock exposed in the open pits, interpretation of geophysical data, and bedrock geological data, an overall fracture directions in the study area are 311, 0, and 18, follow a relatively broad deep fracture zone is located in the direction NW- SE. Thickness of Quaternary sediment is quite thin, varies between 1.05 m to 17.7 m with mean thickness of 2.30 m. It mainly consists of fine-grained till covers approximately 60.0 % of total area, while 13.8% is surface water. Fne-grained sediments such as clay, silt and peat distribute sporadically along the watercourse area and in valleys close to lakes, cover approximately 8.3 % of total area. Fined-grained till and fine-grained sediments have generally low permeability, which provide low infiltration rate of water in to the ground. GPR is a useful tool for investigating the shallow sub-surface when used in the appropriate environment. In the Siilinjärvi mine area, GPR survey can be used to determine the bedrock surface and characterising the Quaternary deposit. However, in the areas that contain fine-grained sediments, e.g. clay, or high electrical conductivity, the GPR profile shows no reflections of the GPR signals and cannot provide the information of the internal structure of the Quaternary deposit or top bedrock surface.

16 GEOLOGICAL SURVEY OF FINLAND 13 7 REFERENCES Hänninen, Pekka, Maatutkaluotaus maaperägeologisissa tutkimuksissa. Summary: Ground penetrating radar in Quaternary geological studies. Report of investigation 103. Geological Survey of Finland. Espoo. 33 p. Huttunen, Timo., Siilinjärvi. Suomen geologinen kartta 1:20 000, maaperäkartta, lehti Geologian tutkimuskeskus. Huttunen, Timo., Kolmisoppi. Suomen geologinen kartta 1:20 000, maaperäkartta, lehti Geologian tutkimuskeskus. Kauko, Puustinen, Geology of the Siilinjärvi carbonatite complex, Eastern Finland, Bulletin de la Commission Geologique de Finlande N: 249, 43p. Parsanen, Antti, The application of ground penetrating radar to the study of Quaternary depositional environments.res Terrae, Ser.A No. 29. Oulu.

17 GEOLOGICAL SURVEY OF FINLAND 14 Figure 9. Bedrock surface elevation map (m a.s.l.) in the Siilinjärvi Mine area.

18 GEOLOGICAL SURVEY OF FINLAND 15 Figure 10. Thickness map of the Quaternary deposit in the Siilinjärvi Mine area.

19 GEOLOGICAL SURVEY OF FINLAND 16 APPENDIX 1: INTERPRETED GPR PROFILES Ground surface and top bedrock surface in each survey line as shown in Figures A1-1 to A1-3.

20 GEOLOGICAL SURVEY OF FINLAND 17

30 GEOLOGICAL SURVEY OF FINLAND 27 Figure A1-1. GPR survey lines in the Musti-tailings area.

31 GEOLOGICAL SURVEY OF FINLAND 28 Figure A1-2. GPR survey lines around the Raisio tailings area.

32 GEOLOGICAL SURVEY OF FINLAND 29 Figure A1-3. GPR survey lines around the calcinate pile and gypsum pile areas.

33 GEOLOGICAL SURVEY OF FINLAND 30 APPENDIX 2: PHOTOGRAPHS FROM FIELD WORK IN SIILINJÄRVI MINE DURING Figure A2-1. Malå GPR Equipment assembly with 2 antenna slots: A (long line, 25 MHz) and B (short line, 100 MHz).

34 GEOLOGICAL SURVEY OF FINLAND 31 Figure A2-2. West-East Cross section of a small sand rich till in front of the artificial Sikopuro artificial lake. GPR line 72 was taken in this section. The total length of the cross section as seen in photo is 100 m and the thickness of the till deposit is 5 m. Scale: Tiina Nurminen height is 175 cm.

35 GEOLOGICAL SURVEY OF FINLAND 32 Figure A2-3. V- Gauging in the creek in east of Saarinen Quarry. Saarinen Quarry is behind the trees. Upper photo was taken in summer ( ) and bottom in spring ( ).

36 GEOLOGICAL SURVEY OF FINLAND 33 Figure A2-4. Creek ( ) next to the V- Gauging in Figure A2-3, east of Saarinen Quarry. Figure A2-5. The fracture bedrock with double ditches collecting runoff and seepage waters around of the gypsum pile.

37 GEOLOGICAL SURVEY OF FINLAND 34 Figure A2-6. Basal till in north of Musti-tailing area. Yellow dashed line represents a contact between fracture bedrock and thin till layer.

38 GEOLOGICAL SURVEY OF FINLAND 35 Figure A2-7. Typical bedrock exposed in the mining area with high fracture and thin cover of fine-grained till. Figure A2-8. Boulder rich till in the area northern of Musti-tailing area. The northern tailing boundary is shown in the upper part of the photo.

39 GEOLOGICAL SURVEY OF FINLAND 36 Figure A2-9. Typical stratigraphy of Quaternary deposit in Siilinjärvi Mine: boulder rich till mixed with fine-grained sediments of glacial fine sand or silt. Photo was taken in the area between south of Saarinen quarry and Raisio areas. Water in the lower photo was received from rainfall from the previous day.