20.3.2017

Science Blog: Assessing the unknown: Finland’s undiscovered mineral resources

Teksti:
Kalevi Rasilainen, Geologist
Pasi Eilu, Senior Scientist

GTK’s Geologist Kalevi Rasilainen and Senior Scientist Pasi Eilu tell in this blog text about assessing Finland’s undiscovered mineral resources.

Figure caption: Median estimates of undiscovered gold resources in types of mineral deposits that contain significant gold. Each symbol shows the median estimate for the whole permissive area it represents.

Assessments carried out by the Geological Survey of Finland (GTK) since 2008 indicate that Finland has notable undiscovered resources of several important metals. As of the end of 2016, assessment results have been published for platinum (Pt), palladium (Pd), gold (Au), silver (Ag), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), lead (Pb), molybdenum (Mo) and chromium (Cr). The undiscovered resources of these metals have been estimated for orogenic Au, volcanogenic massive sulphide (VMS), porphyry Cu, Outokumpu-type Cu-Zn-Co, synorogenic intrusion-related Ni-Cu, komatiite-related Ni, layered intrusion-hosted contact-type and reef-type PGE, and stratiform and podiform Cr deposits in Finland. The assessments were carried out down to the depth of one kilometre using the three-part quantitative assessment method developed by the U.S. Geological Survey.

As one part of the process, grade-tonnage models were constructed using data from well-known deposits within the Fennoscandian shield for most of the assessed deposit types. The orogenic Au model was constructed using Fennoscandian and north Australian deposits and the porphyry Cu model using global data on Precambrian deposits. Areas within which mineral deposits of the assessed types could exist based on their geological properties were then separately delineated for each deposit type. The total number of these permissive areas was 206, and excluding overlap, they cover approximately 191,000 km2. This means that 57 % of the area of Finland has potential for the discovery of new mineral deposits of the types included in the assessments. In a series of workshops, the number of undiscovered deposits was estimated at several levels of confidence for each deposit type and permissive area. The sum of mean estimates of the number of undiscovered deposits for all the deposit types and permissive areas is 341 deposits. In the three-part assessment method, deposits and occurrences that are poorly known and not entirely delineated are also considered undiscovered.

The metal contents of the undiscovered deposits were estimated by combining grade and tonnage data from the deposit models with the estimates of the numbers of undiscovered deposits using Monte Carlo simulation. The sum of median estimates of undiscovered resources across all the assessed deposit types is 350 Mt Cr, 9.7 Mt Cu, 5.0 Mt Ni, 1.8 Mt Zn, 0.15 Mt Pb, 0.10 Mt Mo, 86,000 t Co, 12,000 t Pd, 5600 t Pt, 2100 t Ag and 1400 t Au. Layered intrusion-hosted PGE and Cr deposits are estimated to host the largest undiscovered resources, containing the majority of the undiscovered Cu, Ni, Pt, Pd and Cr. Most of the undiscovered Zn is in VMS deposits and more than half of the undiscovered Au is in orogenic Au deposits.

Comparison between discovered and estimated undiscovered resources indicates that over 90 % of the Pt, Pd and Cr resources and more than half of the Au and Cu resources in Finland exist in undiscovered or poorly known deposits. On the other hand, the undiscovered resources of Ni, Pb and Ag are estimated to be smaller than the discovered resources, and most of the Zn and Co resources in Finland appear to have already been discovered.

When considering the results presented here, it is very important to note that a few potentially significant deposit types (e.g., Kevitsa, Talvivaara and Sakatti types, Precambrian epithermal Au) were excluded from the assessments due to the lack of statistically reliable grade and tonnage data. However, it is possible that undiscovered deposits of these types contain significant mineral resources in Finland.

The results of these assessments can be used in the planning of land use and the sustainable development of mineral resources, in evaluation of the long-term productivity of investments in exploration, and in related research and education. In the coming years, GTK plans to assess undiscovered resources of phosphorus (P), rare earth elements (REE), lithium (Li) and selected by-product elements in common mineral deposit types (e.g., Bi, Sb, Te).

See full articles:

Rasilainen K., Eilu P., Halkoaho T., Karinen, T., Konnunaho, J., Kontinen, A., Törmänen, T. 2016. Quantitative assessment of undiscovered resources in stratiform and podiform chromite deposits in Finland. Geological Survey of Finland, Report of Investigation 226. 186 p. http://tupa.gtk.fi/julkaisu/tutkimusraportti/tr_226.pdf

Rasilainen, K., Eilu, P., Halkoaho, T., Heino, T., Huovinen, I., Iljina, M., Juopperi, H., Karinen, T., Kärkkäinen, N., Karvinen, A., Kontinen, A., Kontoniemi, O., Kousa, J., Lauri, L.S., Lepistö, K., Luukas, J., Makkonen, H., Manninen, T., Niiranen, T., Nikander, J., Pietikäinen, K., Räsänen, J., Sipilä, P., Sorjonen-Ward, P., Tiainen, M., Tontti, M., Törmänen, T., Västi, K. 2016. Assessment of undiscovered metal resources in Finland. Ore Geology Reviews, in press. http://dx.doi.org/10.1016/j.oregeorev.2016.09.031

Kalevi Rasilainen

Teksti: Kalevi Rasilainen

Dr. Kalevi Rasilainen is an economic geologist with long experience on the study of mineral deposits, metallogeny and geochemistry. For the past nine years, he has concentrated on the assessment of undiscovered mineral resources in Finland.

Pasi Eilu

Teksti: Pasi Eilu

Dr. Pasi Eilu specialises in formation and regional to global distribution of mineral deposits, especially on gold, and in using alteration and geochemistry in gold deposit exploration. He has been with the assessment of undiscovered mineral resources in Finland since 2008.