Hokka property drilling in 2016

Transcription

1 Hokka property drilling in 2016 Teemu Voipio, Palsatech Oy April 11, 2017 Introduction Kontiolahti Copper Oy carries out exploration work at the Hokka prospect in Kontiolahti municipality, North Karelia region in eastern Finland. Hokka property is located 30 kilometres north of Joensuu, the provincial capital. The project is centered around Hokka (also known as Hokankallio), one of several small historical copper mines within the project area. Since the early 1900s there has been no further mining or notable exploration work around these deposits. Apart from copper, the company is interested in gold potential. The purpose of this report is to introduce the project and review exploration activities, emphasizing results of drilling carried out in It will also provide recommendations for future exploration work. Figure 1. Location of Kontiolahti Municipality in Finland

2 Project area There is an exploration permit over the Hokka property (license number ), held by Krister Lundqvist/Kontiolahti Copper Oy. The permit was granted in 2013 and is set to expire on November 26, 2018, but can be renewed. In addition, Kontiolahti Copper has obtained exploration reservations around the deposit, covering a much larger area (Figure 2). Figure 2. Tenements held by Kontiolahti Copper. The claim area in the middle in grey color, surrounded by larger reservation areas in yellow.

3 Geology Geologically the project area consists of paleoproterozoic metasediments of the Karelian supergroup. By lithology, these are classified as quartzites, sericite quartzites and mica schists (e.g. Huhma 1975, Laajoki 2005). Figure 3. Geological map of North Karelia and eastern Savo. The project area is located east of Lake Höytiäinen. Modified after Laajoki (2005)

4 The main lithology around Hokka deposit is sericite-quartz schist, belonging to Sariola group ( Ga). These sediments formed of glaciogenic sands and gravels that deposited on Archaean basement. They have been interpreted as paleosols, having paleoweathering features. These are overlain by Jatuli group ( Ga) quartzites, the dominant supracrustal lithology within most of the project area. Local lithologies are bounded in the east and south by Archean granitoids and in the west by upper Karelian (1.9 Ga) metasedimentary rocks. Figure 4. Geology around Hokka deposit, modified after Huhma (1971). Diabase dykes are in green colour, cutting quartzites (yellow). Blue color denotes mica gneiss, while the cream-colored unit in the south is Archaean granodiorite.

5 Figure 5. Geology around Hokka, based on Marmo (1984) and modified by Bergström (2015). Diabase dykes are in purple colour. Other lithological units are various sediments, quartzite is in yellow, while blue is sericite quartzite (kyanite or andalusite bearing) Local sedimentary sequences generally trend in N-S direction, dipping towards the west. These have been subject to greenschist or lower amphibolite facies metamorphism during the Svecofennnian orogeny (1.90 Ga). Sedimentary rocks in this area have been intruded by diabase dykes, mostly trending in NW-SE direction. The copper mineralisation at Hokka and other local occurrences is hosted by quartz and quartz-carbonate veins cutting diabase dykes. Mineral deposits in the region Northern Karelia region is known for various types of mineral deposits. Outokumpu area forms a notable mining camp, subject to polymetallic (Cu, Co, Zn, Ni, Ag) mining between Related to the same ultramafic sequences is Kylylahti copper mine by Boliden AB and Horsmanaho talc mine by Mondo Minerals, both still active. The Outokumpu camp is located 30 to 50 kilometres SW from Hokka. Further away, 60km east of Hokka is the Karelian gold line, a series of Archaean greenstone-hosted gold deposits. There is one operating mine, Pampalo, owned by Endomines AB. Within 10 kilometres from Hokka there are number of small Uranium deposits, including Riutta and Paukkajavaara in the neighboring Eno municipality.

6 Historical mining and previous exploration work Small-scale copper mining has been historically carried out at several localities within the project area, including Hokka and Kyykkä. Hokka was mined in early 1800s and again between 1905 and Geologically these deposits are hosted by quartz (=/- carbonate) veins that cut diabase bodies. Chalcopyrite is the only significant ore mineral. Tigerstedt (1892) and Frosterius & Wilkman (1920) provide geological details of these deposits. Surrounding sericite-quartzite schists are rich in aluminum-silicates (kyanite and andalusite). These were studied by Geological Survey of Finland (GTK) in the 80s (Marmo 1984). GTK drilled 31 drill holes in the area, ranging in depth from 30 to 150 metres. Pilot phase kyanite quarrying took place just north of old Hokka mine in 2000 by Keramia Oy, but it was never further developed. Drilling in 2014 Krister Lundqvist/Kontiolahti Copper Oy obtained exploration permit over the Hokka deposits in The next year they drilled four drill holes (KP1-KP4) within the claim area in, 308 metres was drilled in total (Table 1). A detailed report of the drilling is written in Finnish (Bergström, 2014). Table 1. Collar information of holes drilled at Hokka in Coordinates are in EUREF- FINLAND system. HOLE_ID EASTING NORTHING DEPTH DIP AZIM KP KP KP KP First two holes (KP1 and KP2) intersected mainly country rock sericite quartzite, while the other two holes intersected diabase dyke. Quartz veins in diabase were locally mineralized with chalcopyrite. A set of 15 samples were assayed, all from KP-4, showing promising Copper and Gold grades. The best sample had 2.8% Cu and 2.99 ppm Au. Another sample returned 1.38% Cu for 1.80 metres.

7 Table 2. Selected assay results from drill hole KP-4 HOLE_ID FROM TO LENGTH Au (ppm) Cu (ppm) KP KP KP KP KP KP KP Drilling in 2016 Five drill holes totalling metres of drilling were drilled in the fall of The drilling operator was Northdrill Oy. Figure 6. Drilling around Hokka drill holes have green symbols, 2014 drill holes are in red colour, while blue dots denote old GTK drill holes.

8 Table 3. Collar information of holes drilled at Hokka in Coordinates are in EUREF- FINLAND system. HOLE_ID EASTING NORTHING DEPTH DIP AZIM KP-5a KP KP-6a KP KP These drill holes were logged at Palsatech Oy facilities in Kemi in January The logging included geological and geotechnical (RQD) logging, structural measurements and magnetic susceptibility. Core photos were taken of both dry and wet core. All five drill holes had broadly similar lithology. Diabase was the dominating lithology in every hole. The grain size of diabase is generally fine to medium but does vary. All holes except KP-5a had diabase as the uppermost lithology, with sericite quartzite on the footwall side. The northernmost drill hole, KP-5a had sericite quartzite as surface lithology, underlain by diabase. The hole did not reach the lower contact of diabase, despite being deeper than other holes (90.90 m). The hole was drilled towards the east, possibly along the dip of the dyke. Diabase parts are frequently intersected by quartz veins typically metres wide (core length). These veins commonly contain small amounts of carbonate (less than 5%), or sometimes a higher amount. Carbonate-dominated veins are rare. Diabase shows only little alteration features. Sometimes there is chlorite alteration adjacent to quartz veins. KP-5a had epidote alteration around m, with up to 0.5% sulphides (chalcopyrite and pyrrhotite). About half of the veins contain sulphides, the amount of sulphides being usually less than 0.5%. Chalcopyrite is the most common sulphide mineral, sometimes accompanied by pyrrhotite. Pyrite is present in minor amounts, usually without other sulphides. Sulphides, mostly chalcopyrite, also occur also in fresh (unaltered and non-veined) diabase, but rarely in more than trace amounts. All drill holes expect KP-5 were oriented, using Reflex-act method. In most cases, the orientation was applied on every run. As the core was generally solid, it was often possible to draw long orientation lines and join them together. With few exceptions, the reliability of orientation marks proved to be good.

9 Vein directions were the most measurements structures. While there is considerable variability in vein directions, there are certain trends. Veins dipping steeply to the west and northwest are common. A smaller but distinct group are veins dipping moderately (35-55 ) towards the east. Both groups have sulphide-bearing and barren veins. Several measurements were made of foliation in sericite quartzite, but only few of diabase since it is mostly non-foliated. No measurements could be made of diabase contacts, but in hole KP-7 the lower contact of diabase seemed to be parallel to foliation in sericite quartzite (40 towards the west). Magnetic susceptibility measurements were made on three holes: KP-6A, KP-6 and KP-7, using the KT-6 device. Susceptibility measured from sericite quartzite was very low (below 0.1). Diabase too has low susceptibility (below 1.0), but is magnitude order higher than in surrounding sericite quartzite, thus these diabase bodies should create high anomalies on a detailed magnetic map. Geotechnical properties were measured by RQD method. Diabase is solid (RQD generally above 90), while quartz veins show much more fracturing. Most notable fracture zones coincide with metre-scale intersections of quartz veins. Near-surface weathering was only minimal. Assays 84 half-core samples were selected for analysis. These samples were mainly taken from quartz (or quartz-carbonate) veins within the diabase. A few samples were taken from chlorite altered diabase, as well as unaltered diabase when containing sulphides. One sample represents quartzite containing trace amounts of chalcopyrite. These samples were sent to CRS Minlab in Kempele, Finland. Two sample methods were used for each sample: Fire Assay-ICP/MS for assaying gold (and PGM), and Aqua Regia-ICP for other elements, primarily copper. The results were delivered in February Table 4. Selected assay results from drill holes drilled at Hokka property in HOLE_ID FROM TO LENGTH (m) Au (ppb) Cu (ppm) KP-6a KP KP KP KP KP KP KP KP

10 Figure 7. A core photo of KP-6. The quartz vein in the middle returned with the highest copper grade (7660 ppm), and had elevated gold (149 ppm) The copper content was promising in many samples, but only over short lengths. Gold grades were most promising in the drill hole KP-7, the highest value was 385 ppb Au. The sample length was only 0.20 metres, it was taken from an amphibolecarbonate-quartz vein. Conclusion Results of the latest round of drilling did not meet the expectations. Still, the occurrence of both copper and gold in anomalous amounts is encouraging. After the latest round of drilling, it is increasingly unlikely to find a larger copper mineralization within the existing claim area. Instead, the focus should be shifted to larger area, where Kontiolahti copper already holds exploration reservations. Since there are several known copper occurrences, there may be a bigger system around. The amount of copper was low, but chalcopyrite is the dominating sulphide in this system. If sulphides are found in larger amounts, chalcopyrite would likely still be a major component.

11 The currently known copper and gold mineralisation is limited to quartz (+/- carbonate) veins in diabase bodies. Finding a significant ore body in such geological setting may be unlikely, but even a small deposit could be mined here economically, if it is close to surface. The existence of processing facilities in the region is a major advantage. Recommendations for further work Bedrock mapping The objectives of mapping would be to determine the extents and structural orientation of diabase bodies and veins within them, and recognise sulphides and interesting alteration features. Outcrops with known mineralization should be mapped in detail. Elsewhere lithologies and structures would be mapped in more general way. It is also worth prospecting for mineralised rocks, either outcrop or boulder, and send interesting samples for analysis. There is good exposure of outcrops in this area, but this also means comprehensive bedrock mapping within the project area would require much work to complete. Re-logging old drill core Old GTK drill holes can be reviewed at the Loppi core storage. These holes were drilled to quartz-sericite schists rich in Al-silicates. A few of these holes did briefly intersect diabase according to drill hole sections (Marmo 1984). Any signs of mineralization, or interesting alteration patterns should be noted. There are 31 drill holes in total, but selecting only most relevant ones for re-logging will be adequate. Geochemical surveys Geochemical surveys will detect anomalies of copper, gold and other elements of interest. The cheapest option would be taking soil surface samples with shovel (e.g. MMI sampling). Till sampling may yield better results, but is more expensive. Despite good bedrock exposure geochemical surveys would be useful, as sulphiderich parts will be more weathered, thus more likely to be under cover. Geophysical surveys Detailed magnetic surveys will help in mapping local geological units and determine prospective structures. Ground magnetic surveys will be highly detailed, but are only feasible at target scale as covering large areas would take too much time.

12 Aeromagnetic surveys can cover larger areas, but are expensive. A newly developed technique is drone magnetics. This is much cheaper than aeromagnetic surveys, yet fast way to produce magnetic maps detailed enough for most cases. For finding sulphidic ore bodies, electromagnetic or IP surveys will be essential. An aerial EM survey is recommended if there are no budget constraints. Drilling Additional core drilling should be considered if interesting enough targets come up. References Bergström, J Hokan mineralisaatio, Kontiolahti. Unpublished report, GeoDon Ky. Frosterus, B. & Wilkman, W. W Suomen geologinen yleiskartta, Lehti D3 Joensuu, Vuorilajikartan selitys. Geologinen toimisto. Huhma, A Kallioperäkartta, Lehti 4224 Kontiolahti. Geologinen tutkimuslaitos Huhma, A. 1975: Outokummun, Polvijärven ja Sivakkavaaran kartta-alueiden kallioperä. Kallioperäkartan selitykset. Suomen geologinen kartta 1: Lehdet 4222, 4224, Geologinen tutkimuslaitos. Espoo. Laajoki, K Karelian supracrustal rocks. In: Lehtinen, M., Nurmi, P. and Rämö, O.T. (eds.). Precambrian Geology of Finland Key to the Evolution of the Fennoscandian Shield. Developments in Precambrian Geology 14, Elsevier, Amsterdam, Marmo, J. & Pekkala, Y Tutkimustyöselostus Kontiolahden kunnassa sijaitsevista Hokkalammen alueen kyaniitti- ja andalusiittiesiintymistä. Geologian tutkimuskeskuksen malmiosaston raportti. M06/4224/-84/1/82. Tigerstedt, A. F De kopparkisförande qvartzgångarne i Kontiolax och Eno socknar undersökta sommaren s., 6 l.(5 geol.k.)