Till geochemical exploration of the Kedonojankulma Cu-Au deposit in Jokioinen, Southern Finland Markku Tiainen and Niilo Kärkkäinen

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1 GTK, Southern Finland Office Espoo Till geochemical exploration of the Kedonojankulma CuAu deposit in Jokioinen, Southern Finland Markku Tiainen and Niilo Kärkkäinen

2 GTK GEOLOGICAL SURVEY OF FINLAND DOCUMENTATION PAGE Date / Rec. no. Authors Markku Tiainen Niilo Kärkkäinen Type of report Exploration report Commissioned by Title of report Till geochemical exploration of the Kedonojankulma CuAu deposit in Jokioinen, Southern Finland Abstract The polymetallic Kedonojankulma CuAu(AgMoZnAsBiSb) target was found by till geochemical exploration. The highest copper content in the investigation of the regional Cu anomaly was 4.3% Cu in the fine fraction of till from the surface of the bedrock. In targetscale exploration, sampling was systematically carried out from the base of the till layer, comprising 380 samples taken in a 50metre grid and 416 samples taken in profiles. The < 2mm fraction was analysed from the grid samples to also find possible coarse gold. Later, only the fine fraction (<0.06 mm) from the profile samples was analysed, because Cu was observed to be the main metal of the target, and this metal was clearly recorded in the fine fraction. Chemical analysis of the selected fraction of till was conducted using the aqua regia leached part by multielement ICPAES, and gold was analysed by GFAAS. The till geochemical anomaly maps of Cu, Mo, Ag, Au, As, S and Zn are presented here as results of the till geochemical exploration of the Kedonojankulma target, covering both the submitted claim of Kedonojankulma (8304/1) and the areas of the claim applications (8775/1, 9008/1, 9238/1), where sampling permission was obtained from the landowners. The mineralized part of the Kedonojankulma intrusion was most clearly indicated by the Cu content in the fine fraction of till. Keywords Till geochemistry, exploration, copper Geographical area Map sheet Other information Report serial Archive report Archive code Total pages 19 Language English Price Confidentiality Confidential Unit and section Southern Finland Unit, Bedrock and Mineral Resources Signature/name Markku Tiainen Project code Signature/name Niilo Kärkkäinen

3 GTK Contents Documentation page 1 INTRODUCTION Location of the study area Methodologies applied in till geochemical exploration 3 2 TILL GEOCHEMICAL EXPLORATION OF THE KEDONOJANKULMA TARGET Regional survey Target survey Till fraction < 2 mm Till fraction < 0.06 mm 13 3 CONCLUSION AND SUMMARY 17 4 LITERARURE REFERENCES 18

4 GTK 1 1 INTRODUCTION 1.1 Location of the study area The Kedonojankulma prospect is located in the volcanicintrusive Häme Belt, part of the palaeoproterozoic Southern Finland supersuite. Locally, the target is in the municipality of Jokioinen, about 13 km to the north of the city of Forssa (Fig. 1). Figure1. Location of the Kedonojankulma prospect on a geological map. The till geochemistry is from the ALMR data of GTK (Salminen 1995). The geological map is from the digital map database of GTK (2010). The Ministry of Employment and the Economy admitted the claim Kedonojankulma (8304/1) on to carry out exploration for Au and Cu in the Kedonojankulma area (Fig. 2). Later, in 2009 and 2010, GTK submitted three more claim applications to extend the exploration area to the south and west of the admitted claim area. The applications are currently being processed by

5 GTK 2 the Ministry, and the exploration has been carried out with the permission of the landowners. Therefore, the sampling at this stage does not cover the whole exploration target, but is concentrated in the Kedonojankulma claim area and small parts of the claim application areas. The impetus to start the geochemical mapping project in Forssa Huittinen and was the detection of a CuTe anomaly in the regional till geochemical data of Finland (ALMR) in the Kuuma area, about km to the north of the city of Forssa (Fig. 1) (Kärkkäinen et al. 2008). The highest Cu content in the Kuuma anomaly recorded in the ALMR data is 208 ppm and the highest Te content is 0.55 ppm. The ALMR data, which cover the whole country, are based on a sampling density of about 1 sample per 4 km 2 and on analyses of the aqua regia leached part of the fine fraction of till (Salminen, 1995). Figure 2. Location of the Kedonojankulma claim (8304/1) and claim application areas. Basemap National This report first briefly reviews the geochemical exploration of the Forssa Humppila area, which led to the discovery of the Kedonojankulma exploration target (Kärkkäinen et al. 2008). The preliminary results of the till geochemical exploration of Kedonojankulma have been reported by Tiainen et al. (2008). The discovery hole in the Kedonojankulma deposit was drilled soon after the geochemical mapping of the Forssa area. The aim of subsequent systematic exploration was to map the extent of the mineralization in the Kedonojankulma target. Understanding of the deposit type developed during the exploration and logging of the drill cores. The deposit was explored as a granitoidhosted, porphyricstyle CuAu deposit. The discovery of the Kedonojankulma deposit was first published by Tiainen et al. (2011).

6 GTK 3 The main focus of this report is on the results of till geochemical exploration of the Kedonojankulma target, emphasizing the exploration perspective. The exploration process was in principle a rather simple and straightforward mapping of the Cu anomalies, because Cu is the main metal of the deposit and the geochemistry of Cu is well defined. 1.2 Methodologies applied in till geochemical exploration In the Forssa area, the bedrock is covered by Quaternary deposits, consisting of clay as the uppermost layer and till at the bottom. The thickness of the clay layer varies up to 20 m, while the thickness of the till deposits typically varies from 1 to 5 m. In Kedonojankulma target, the thick clay overburden hindered the effective use of electromagnetic geophysical methods in exploration. However, the clay overburden was easily penetrated by percussion drilling. Consequently, till geochemistry, based on sampling from the bottom of the base till, was the main exploration method before the diamond drilling stage. The size of the till samples taken by percussion drilling, was about one dm 3, or g. For chemical analysis, the samples were dried and sieved either to the fine fraction (<0.06 mm) or to the <2 mm fraction. In chemical analysis, the aqua regialeached part of the selected fraction of till was analysed by multielement ICPAES and gold was quantified by GFAAS. The till geochemical exploration process was conceptually divided into two main phases. The first phase was the regional target selection phase, covering the whole Forssa area (Kärkkäinen et al. 2008). This was carried out at a sampling density of about 4 samples per km 2, mainly along road sides and along paths in forest areas. The analysed fraction of till was <0.06 mm. The most interesting anomalies at the regional scale were confirmed by a few till geochemical profiles before detailed exploration. The second till geochemical exploration phase focused on the Kedonojankulma target involved systematic till geochemical mapping of the Cu anomaly and the Kedonojankulma intrusion. In practice, sampling did not evenly cover the whole intrusion, because it was based on the permission of the landowners. The local exploration phase of the Kedonojankulma target methodologically included two subphases. First, the base of till was sampled in a regular 50metre grid to cover the most anomalous firststage target (claim area). The sample sieved for chemical analysis was the <2 mm fraction of till to include possible gold nuggets in the analysis. During the exploration process, including both geochemistry and drilling, it was observed that Cu was the main metal of the deposit and the extent of the mineralization was clearly defined by the Cu anomaly in the fine fraction of till. Consequently, possible extensions of the known mineralization were investigated by applying geochemistry to the fine fraction (<0.06 mm) from the base of the till, which was sampled in profiles at a sample spacing of m. 2 TILL GEOCHEMICAL EXPLORATION OF THE KEDONOJANKULMA TARGET 2.1 Regional survey A till geochemical exploration project in the Forssa area, in the southern part of the Forssa Huittinen geochemical mapping project area, was carried out in (Kärkkäinen et al. 2008). The aim of the regional mapping phase was to check the Kuuma CuTe anomaly recorded in the nationwide ALMR data, and to find more accurately delineated targets for detailed exploration. The exploration method involved sampling of the base of till in a subregular net,

7 GTK 4 along roads and paths, with a sampling density of about four samples per km 2. The aqua regia leached part of the fine fraction of the sample was analysed by ICPOES and GFAAS. As a result of the regional survey, several local CuAuAsTe anomalies were detected, of which the Kedonojankulma target was one of the most interesting (Fig. 3). About half of the 15 samples taken in the regional phase from the Kedonojankulma area had an anomalously high (<150 ppm) Cu content (Fig. 4). The sample with highest copper content, 826 ppm Cu and 341 ppb Te, was taken from the northern part of the firststage target exploration area (Fig. 4). Figure 3. Till geochemical Cu, Au and Te anomalies in the regional survey of the Forssa area. The background is the geological map of GTK (2010). Basemap National Land Survey of Finland, licence no. 13/MML/11 and Logica Suomi Oy.

8 GTK 5 Figure 4. Cu and Te contents recorded in the regional till geochemical survey of part of the Forssa area, in the Kedonojankulma target. Basemap National Land Survey of Finland, licence no. 13/MML/11 and Logica Suomi Oy. Figure 5. The CuAuTe anomaly confirmed after checking the regional phase anomaly in Fig. 4. Basemap National. The Kedonojankulma CuAuTe anomaly of the regional survey was confirmed by 42 samples taken along profiles (Fig. 5). Almost all of the samples from the claim area were anomalous for Cu, containing a maximum of 4.3% Cu and 566 ppb Au in the fine fraction of till.

9 GTK 6 The source of the CuAuTe anomaly of Kedonojankulma was checked by drilling in the Cu anomaly and also by observing the mineralized outcrop of Rusakkokallio. The first drill hole in the Kedonojankulma target intersected a CuAu mineralization at 20 m with the highest metal contents of 1.83% Cu and 3.75 ppm Au (Fig. 6). Figure 6. The first drill hole (R325) in the Rusakkokallio Cu anomaly in Kedonojankulma. Highest metal contents: Cu 1.83% (green) and Au 3.75 ppm (red). 2.2 Target survey The till geochemical data from the Kedonojankulma area consist of two data sets: one for the <2 mm till fraction (380 samples) and the other for the fine fraction of till (416 samples). The data for the fraction below 2 mm are the results of samples taken from the firststage target area in Kedonojankulma (claim 8304/1). The target area was later widened to the south and southwest based on the results of the geochemical and geological mapping surveys. The data on the fine fraction of till are partly from the claim area (claim 8304/1) and partly from the claim application areas (8775/1, 9008/1). In statistical analysis, the element contents below the detection limit have been calculated as 0.5 * detection limit. The glacial transport of the till material was to the east southeast (about 300 o ). The till samples were taken from the bottom of the base till to reduce the effect of transportation, but this must nevertheless be kept in mind when interpreting the anomaly patterns.

10 GTK 7 The two data sets were compared using histograms (Figs 7 & 8) and based on the key descriptive statistics (Tables 1 and 2). In general, the means and maximum values of metal contents are higher in the fine fraction of till than in the fraction below 2 mm. The results of this simple comparison of the metal contents parallel those reported by Kärkkäinen et al. (2008). Figure 7. Histograms of Au contents in the till geochemistry data of Kedonojankulma. The distribution is on a logarithmic scale.

11 GTK 8 Figure 8. Histograms of Cu contents in the till geochemistry data of Kedonojankulma. The distribution is on a logarithmic scale. 2.3 Till fraction < 2 mm The fraction of till below 2 mm was investigated in the mapping of the firststage exploration target area of Kedonojankulma (claim 8304/1). The coarser fraction was used to include possible gold nuggets in the analysis. The data set comprises 380 samples (Table 1). The maximum values of the metals Cu, Au, As, S, Ag and Mo are anomalously high in the granitoid environment. The mean values of Cu, Au, S and Zn are also anomalously high. The spatial distribution of the metal anomalies is presented in Figures Table 1. Descriptive statistics for the most interesting metals in the <2 mm fraction of till. Descriptive Statistics N Minimum Maximum Mean Std. Deviation Ag, ppm As, ppm ,0 37, Au, ppb Cu, ppm Mo, ppm S, ppm Zn, ppm

12 GTK 9 The Cu, Mo and Ag anomaly patterns of the < 2 mm till fraction appear rather similar. The clearest anomaly is in the vicinity of the Rusakkokallio mineralization. Weaker anomalies extend to the south to the Passi area and to southwest towards the Korpi area (Figs 9 11). The northern boundary of the Cu and Mo anomalies is sharp, clearly delineating the northern boundary of the mineralized rock. The Ag anomaly follows the Cu anomaly, but also extends outside the strongest Cu anomaly, for example to the north of it. The Au anomaly pattern is mainly restricted to the claim area (Fig. 11). The highest value, 1490 ppb Au, probably includes an Au nugget. The focus of the Au anomaly is in the vicinity of the Rusakkokallio mineralization. The As contents are in this case either high or low, often below the detection limit, indicating the existence of an arsenopyritebearing mineralization as a source of the anomalous sample. The Rusakkokallio mineralization is most clearly the source of the northern As anomaly. S and Zn anomaly patterns are rather similar. Both Zn and S contents are rather high in the vicinity of the Rusakkokallio mineralization and are clearly included in the mineralization. High S and Zn contents also exist outside of the known mineralization, but within the mineralized intrusion, and also outside the porphyritic tonalite, in the connection with the volcanic schists, which typically include weak pyrrhotite dissemination. The main result of the till geochemical survey, applying the <2 mm till fraction, is the delineation of the Cu potential area. The drilled polymetal Rusakkokallio mineralization is shown by all elements that are presented here, but most clearly by Cu and Mo. S, Zn and partly Ag form wider anomalies, also indicating other sources in addition to the known mineralization. For S and Zn, the surrounding volcanic schists are an obvious source outside the mineralization. Figure 9. Cu content of the <2 mm till fraction in the Kedonojankulma target. Basemap National

13 GTK 10 Figure 10. Mo content of the <2 mm till fraction in the Kedonojankulma target. Basemap National Figure 11. Ag content of the <2 mm till fraction in the Kedonojankulma target. Basemap National

14 GTK 11 Figure 12. Au content of the <2 mm till fraction in the Kedonojankulma target. Basemap National Land Survey of Finland, licence no. 13/MML/11 and Logica Suomi Oy. Figure 13. As content of the <2 mm till fraction in the Kedonojankulma target. Basemap National

15 GTK 12 Figure 14. S content of the <2 mm till fraction in the Kedonojankulma target. Basemap National Figure 15. Zn content of the <2 mm till fraction in the Kedonojankulma target. Basemap National

16 GTK Till fraction < 0.06 mm The last phase of the localscale geochemical exploration of the target focused on the fine fraction of till. The aim was to map the possible extension of the geochemical anomaly to the southwest, in the Korpi area, and partly to the south, in the Passi area. The fine fraction data set includes both the new profile samples and the samples taken earlier in the checking of the regional CuTe anomaly (Fig. 5). Sampling outside of the claim area was carried out with the permission of the landowners and therefore did not cover whole target area. The data set comprises 416 samples (Table 2). Table 2. Descriptive statistics on the most interesting metals of the fine till fraction in the Kedonojankulma area. Descriptive Statistics N Minimum Maximum Mean Std. Deviation Ag, ppm As, ppm Au, ppb Cu, ppm Mo, ppm S, ppm Zn, ppm The descriptive statistics on the element contents of the fine fraction of till are similar to the statistics for the coarser fraction (< 2mm). However, the sampling of the coarser fraction was more clearly focused on the mineralized area, while the fine fraction data also include samples taken outside of the main exploration target area. The Au and Ag contents are higher in the coarse fraction, while As, Cu, Mo, S and Zn have higher values in the fine fraction data. The maximum values of all of the studied elements, Cu, Ag, As, Au, Mo, S and Zn, are anomalously high, indicating the existence of a mineralized source for the till material. The highest Cu content, 4.3%, indicates that the sample was probably taken from the surface of an ore outcrop. The maximum Au content, 588 ppb, is also very high. The sample with the highest Zn content, 3940 ppm, was probably taken from mineralized material. The mean values are also high, indicating that the sampling area was mainly in a granitoid environment. In addition to the elements presented here, for example the Bi, Sb and Te contents are anomalously high. The highest Cu contents are located near to the Rusakkokallio mineralization, but there are also high Cu contents in the Passi and Korpi areas, indicating the existence of other mineralizations in addition to the known one at Rusakkokallio, or an extension of the known mineralization (Fig. 16). The concentrations of Mo and Ag follow Cu in the Kedonojankulma target, although the anomalies are not so extensive. In the fine fraction, the anomaly patterns of Au and As (Figs 19 and 20) are more similar than in the coarse fraction (Figs 12 and 13). The Au anomaly of the fine fraction is also more extensive than the anomaly of the coarser fraction.

17 GTK 14 The CuAuMoAgAs anomaly is clearly delineated to the north in the contact of the porphyritic Kedonojankulma tonalite, but is not so sharply delineated to the south, partly because of glacial dispersion. Figure 16. Cu content of the <2 mm till fraction in the Kedonojankulma target. Basemap National

18 GTK 15 Figure 17. Mo content of the fine fraction of till in the Kedonojankulma target. Basemap National Figure 18. Ag content of the fine fraction of till in the Kedonojankulma target. Basemap National Figure 19. Au content of the fine fraction of till in the Kedonojankulma target. Basemap National

19 GTK 16 Figure 20. As content of the fine fraction of till in the Kedonojankulma target. Basemap National Figure 21. S content of the fine fraction of till in the Kedonojankulma target. Basemap National

20 GTK 17 Figure 22. Zn content of the fine fraction of till in the Kedonojankulma target. Basemap National 3 CONCLUSION AND SUMMARY Till geochemical mapping of the Kedonojankulma target was conducted in two main phases. First, the target was identified in regional till geochemical exploration of the Forssa area. Next, the target area was surveyed on a local scale by till geochemical mapping of the bottom of the basal till. The first drill holes in the Kedonojankulma CuAu deposit were drilled in association with the regional till geochemical anomaly and in relation to the mineralized outcrop of Rusakkokallio. Although there are gaps in the coverage of the till geochemical sampling points, the till geochemistry data indicate that the mineralized zone extends more or less continuously from Rusakkokallio to Korpi (Fig. 11). According to the till geochemistry data, the mineralization is a polymetallic CuAu(AgMoZnAsBiSb), with copper clearly as the main element. The mineralization is hosted by a porphyritic granitoid intrusion.

21 GTK 18 Figure 23. Till geochemistry of the Kedonohjankulma Cu anomaly, including data on the <0.06 mm and <2 mm till fractions. In the background, a geological map of Kedonojankulma based on geological mapping and drilling data. The scale of the symbols indicating the Cu content is wider than usually applied in anomaly mapping. The location of the mineralizations is based on drilling and geological mapping. 4 LITERARURE REFERENCES Geological Survey of Finland (GTK) Bedrock of Finland, Bedrock map (database) of Finland in 1: scale combined with description and electronic references of the lithostratigraphic and lithodemic units. Available at: Kärkkäinen, N., Tiainen, M., Vuori, S., Huhta, P Moreenigeokemiallinen kartoitus v ForssaHuittinen alueen kultamalmipotentiaalin arvioimiseksi. 32 s. + 3 liites. Geologian tutkimuskeskus, arkistoraportti, M19/2113/2008/81.

22 GTK 19 Salminen R. (ed.), Alueellinen geokemiallinen kartoitus Suomessa Summary: Regional geochemical mapping in Finland in Geologian tutkimuskeskus. Tutkimusraportti 130. Espoo: Geologian tutkimuskeskus. 47 p app. maps. Tiainen, M., Kärkkäinen, N., Jokinen, T., Lahtinen, E., Alanen, J., Karttunen, K., and Karimerto, P., Jokioisten Kedonojankulman AuCuesiintymän tutkimukset , moreenigeokemia ja malmimineralogia. 18 p., 3 appendices. Geologian tutkimuskeskus, arkistoraportti M19/2113/2008/9/84. Tiainen, M., Kärkkäinen, N., Koistinen, E., Pakkanen, L. and Sipilä, P Kedonojankulma, a recently discovered Palaeoproterozoic porphyrytype CuAu deposit in Southern Finland. In Barra, F., Reich, M., Campos, E. and Tornos, F. (eds) Let s Talk Ore Deposits. Proceedings of the Eleventh Biennal SGA Meeting, 2629 September 2011, Antofagasta, Chile. Ediciones Universidad Catolica del Norte, Antofagasta, Chile,