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GEOLOGICAL SURVEY OF FINLAND

Northern Finland Office

Rovaniemi

7.5.2014 58/2014

Till geochemical research in the Savukoski-

Pelkosenniemi region

Pertti Sarala

GEOLOGIAN TUTKIMUSKESKUS 58/2014

7.5.2014

GEOLOGICAL SURVEY OF FINLAND DESCRIPTION

Date/ Dnro

7.5.2014

Author

Pertti Sarala

Report type

Final report

Ordered by

GTK

Name

Till geochemical research in the Savukoski-Pelkosenniemi region

Abstract

The Geological Survey of Finland (GTK) in co-operation with the NATI Research Oy carried out Quaternary geological re-

search in the Savukoski-Pelkosenniemi region in eastern Finnish Lapland in 2012-2013. The aim of the project was to test

the CROCS technology of NATI in a regional mineral potential mapping when the glacial till samples were used. 102 till

samples with about 3-5 km sampling interval were collected as a part of GTK’s own sampling programme. Test pits and soil

drilling were used to collect the till samples from a basal part of the glaciogenic overburden, near the bedrock surface. In this

report, the results of conventional till geochemistry (<0.06 mm sieved size fraction analysed by ICP-OES after aqua regia

digestion) made by GTK is presented. The results prove the study area to be potential for several base metals like chromium

and nickel together with gold and PGE. Results of the CROCS technology application by NATI were presented in the sepa-

rate, appended report (http://www.natires.com/rrs2013-1.htm, referred 7th

May 2014).

Keywords

Geochemistry, till, heavy minerals, exploration, CROCS technology

Geography (country, province, municipality, village, occurrence etc.)

Finland, Lapland, Pelkosenniemi, Savukoski

Map sheet

Other information

Name of the report serie

Archive report

Archive code

58/2014

Page numbers

10 p.

Language

English

Price

-

Publicity

Public

Unit and department

Northern Office, Bedrock geology and Resources

Project code

7780031

Signature

Pertti Sarala

Signature

GEOLOGICAL SURVEY OF FINLAND 58/2014

7.5.2014

Content

DESCRIPTION

1 INTRODUCTION 1

2 BEDROCK 2

3 QUATERNARY GEOLOGY 2

4 METHODS 2

5 RESULTS 3

6 DISCUSSION AND CONCLUSIONS 9

7 REFERENCES 9

GEOLOGICAL SURVEY OF FINLAND 58/2014 1

1 INTRODUCTION

Geological Survey of Finland (GTK) and NATI Research Ltd. carried out a small methodological testing

of the CROCS technology in Häme region, southern Finland in 2011 (Knauf 2012). The test was related

to gold potential mapping of the area nearby Tammela. That project rose up an idea to continue method-

ology testing in a regional scale in some other study area of GTK. The area in Savukoski-Pelkosenniemi,

eastern Finnish Lapland was chosen for a new project area.

This project included both a conventional till geochemical research done by GTK and the methodological

testing of the CROCS technology done by NATI Research Oy. For the sample material of the research

GTK collected 102 basal till samples from the whole study area (Fig. 1) as a part of GTK’s own sampling

programme. The sampling was carried out in 2012-2013. The aim of the GTK’s own programme was to

collect till and bedrock samples from the area to study geochemical and lithological features of the area to

estimate mineral exploration potential of the area. GTK’s sampling point network was planned based on

earlier geological knowledge and Quaternary maps of the study area. Analyse and interpretation results

were not applied to verify during this project.

Fig. 1. Location of the Savukoski-Pelkosenniemi study area in eastern Finland. Till sampling points used

for collecting samples in this study are also presented on the bedrock map 1:200 000 after GTK.


2 BEDROCK

Bedrock in the study area consists of both Achaean and Proterotzoic rocks and the contact zone between

them (Fig. 1). Archaean rocks in the eastern part are mainly composed of granite gneiss and some mafic

volcanic rocks (Juopperi 1986). They are a part of 2.5-3.0 Ga old the Tuntsa Suite that are existing in

eastern Lapland. In the western part of the study area, quartzites, mica schicts, diabase veins and some

mafic rocks of the 2.0-2.4 Ga old Savukoski Group exist. The narrow chain of komatites and mafic vol-

canic rocks with some mica schists are following the contact of Archaean and Proterotzoic rocks almost

in north-south orientation through the area. In south-eastern corner of the study area situates the Akan-

vaara layered intrusion of 2.44 Ga in age. It includes chromium mineralization that was studied in many

phases over decades (Mutanen 1997). Rocks in the whole study area are strongly deformed and faulted,

and metamorphosed in the amphibolite facies. The bedrock is largely pre-glacially weathered having sev-

eral metres thick partly or totally softened saprolite of saprock surface. In places weathering has been ef-

fective and as a consequence of it kaolinite is found in the bedrock.

3 QUATERNARY GEOLOGY

The study area locates on southern side of the last ice-divide zone of the Late Weichselian glaciation (Jo-

hansson et al. 2011). Ice flow direction has been mainly from north-west to south-east. After strong gla-

cial events, glaciogenic overburden composed mainly on sandy till covers the bedrock dominantly in the

area. Only the tops of the highest hills are covered by the block fields of frost-weathered bedrock. In low

land areas peat deposits are common and cover till layers. There is one glaciofluvial esker system that

crosses the area in northwest-southeast direction in the central part of the study area. Post-glacial river

sands and silts are common in the Kemijoki River valley. Based on test pit, soil and percussion drilling

data the thickness of overburden varies generally 2-5 m, but in topographic depressions and in the river

valleys it can reached up to 50 m.

4 METHODS

Till samples were collected using the test pits and soil drillings (Table 1). Totally 102 sampling points

were used to collect basal till samples. The samples were stratigraphy controlled and the sampling depth

has been about one meter above bedrock surface from the bottommost till bed. This sampling strategy

was supposed to produce most homogeneous sampling material where the till samples represents most

uniform glacial transport and deposition processes.

In this project two types of till samples were used: a) c. 250-350 g for conventional till geochemistry

(used in GTK) and b) c. 5 litres, i.e. 7-10 kg that were sent to NATI for the CROCS technology applica-

tion. Conventional till samples were dried (70°C) and sieved (<0.063 mm) before digesting subsample (5

g) using aqua regia. After that they were analysed by ICP-OES and ICP-MS for 41 elements (method

515PM) and GFAAS for gold and palladium (method 521U) in the Labtium laboratory (Labtium order

47506). The 5 litres samples were sent to NATI’s laboratory and they were processed as described in the

appended report (http://www.natires.com/rrs2013-1.htm, referred 7th

May 2014). Analysis includes both

geochemical and mineralogical component of the concentrated till samples. Furthermore, two concentrate


fractions processed by NATI (so called heavy fraction, HF, and fine fraction, FF)) were analysed in the

Labtium laboratory (ordered by GTK) using the same methods as were used for the conventional geo-

chemistry (Labtium orders 47526, 47527, 47559, 47560).

Table 1. List of the test pits (POS$) and soil drilling points (JOV$, HAH1) in the study area.

ID X Y ID X Y ID X Y

POS$-2012-32 7482752 3543117 POS$-2012-69 7467269 3537423 POS$-2012-101 7457560 3530477

POS$-2012-33 7480340 3540302 POS$-2012-70 7465661 3537083 POS$-2012-102 7457315 3528891

POS$-2012-34 7479798 3542003 POS$-2012-71 7467479 3535087 JOV$-2012-6 7472347 3546733

POS$-2012-35 7476389 3541291 POS$-2012-72 7464888 3535453 JOV$-2012-11 7465610 3558102

POS$-2012-36 7473123 3544537 POS$-2012-73 7463151 3536255 JOV$-2012-12 7466073 3559059

POS$-2012-37 7470752 3546907 POS$-2012-74 7459880 3545694 JOV$-2012-13 7465452 3546656

POS$-2012-38 7484402 3543362 POS$-2012-75 7463166 3543380 JOV$-2012-15 7463763 3549852

POS$-2012-39 7483518 3557411 POS$-2012-76 7461597 3539822 JOV$-2012-20 7460850 3547449

POS$-2012-41 7479072 3555644 POS$-2012-77 7455512 3556675 JOV$-2013-1 7451950 3524536

POS$-2012-42 7478984 3558074 POS$-2012-77 7455512 3556675 JOV$-2013-2 7452523 3526181

POS$-2012-43 7476607 3554298 POS$-2012-78 7457812 3557228 JOV$-2013-9 7456037 3528345

POS$-2012-44 7476817 3556085 POS$-2012-79 7458614 3556922 JOV$-2013-10 7455004 3529072

POS$-2012-45 7476980 3559272 POS$-2012-80 7455262 3558193 JOV$-2013-11 7455062 3531218

POS$-2012-46 7472567 3558748 POS$-2012-81 7451960 3557399 JOV$-2013-12 7456647 3531851

POS$-2012-47 7470007 3557788 POS$-2012-82 7451133 3558767 JOV$-2013-13 7458829 3532873

POS$-2012-48 7471499 3553502 POS$-2012-83 7451331 3549586 JOV$-2013-14 7458762 3536063

POS$-2012-49 7473784 3552914 POS$-2012-84 7452163 3548697 JOV$-2013-15 7459714 3537561

POS$-2012-50 7476593 3552171 POS$-2012-85 7457505 3550868 JOV$-2013-16 7456389 3541663

POS$-2012-51 7480740 3552881 POS$-2012-86 7458087 3546217 JOV$-2013-17 7455285 3541079

POS$-2012-52 7469263 3545549 POS$-2012-87 7455518 3544999 JOV$-2013-19 7451074 3533182

POS$-2012-53 7486541 3552752 POS$-2012-88 7455115 3543679 JOV$-2012-25 7458680 3547760

POS$-2012-54 7482638 3550369 POS$-2012-89 7453487 3541931 JOV$-2012-27 7458118 3553907

POS$-2012-55 7481187 3550502 POS$-2012-89 7453487 3541931 JOV$-2012-28 7459784 3554270

POS$-2012-56 7486329 3544600 POS$-2012-90 7452456 3540935 JOV$-2012-34 7466725 3542437

POS$-2012-57 7485124 3548940 POS$-2012-91 7455549 3533589 JOV$-2012-40 7461715 3544238

POS$-2012-59 7483028 3547611 POS$-2012-92 7458098 3537908 JOV$-2012-41 7462077 3541618

POS$-2012-61 7475805 3547698 POS$-2012-93 7457721 3534194 JOV$-2012-41 7462077 3541618

POS$-2012-62 7475813 3545370 POS$-2012-94 7460579 3534219 JOV$-2012-43 7458269 3541480

POS$-2012-63 7477668 3544459 POS$-2012-95 7460588 3534226 JOV$-2012-45 7461376 3558826

POS$-2012-64 7478977 3547643 POS$-2012-96 7466690 3531867 HAH1-2012-500 7486177 3541657

POS$-2012-65 7470145 3550016 POS$-2012-97 7467722 3531168 HAH1-2012-502 7482216 3547193

POS$-2012-66 7467694 3543863 POS$-2012-98 7469777 3530700 HAH1-2012-504 7482444 3552532

POS$-2012-67 7469693 3534779 POS$-2012-99 7464828 3531172 HAH1-2012-505 7484176 3553971

POS$-2012-68 7469293 3536440 POS$-2012-100 7461237 3529190 HAH1-2013-2 7468012 3554668


5 RESULTS

Conventional till geochemistry based on <0.06 mm till size fraction has strong relation to lithological

units in the bedrock. Narrow komatite-volcanic rock zone is clearly coming out both in chromium and

nickel geochemistry (Figs. 2 and 3). Some elevated contents are also seen in eastern and soutwestern parts

of the area in relation to diabase, gabbro and mafic volcanic rocks. Although the contents are high, they

are typical for the tills the sources of which are the komatites. Several other base metals like Cu, V, Zn

follow the distribution of mafic volcanic rocks and also black schists found in the central parts close to

komatites. Highest sulphur contents are also occurring in the same areas (Fig. 4). These results together

indicate the same source areas and possible multimetal enrichment in the bedrock. These results are in

line with the earlier regional scale till geochemical data of the area (GTK’s database).

Fig. 2. Chromium contents of the till fines (<0.06 mm) in the Savukoski-Pelkosenniemi area. Bedrock map © GTK, Basemaps:

© National Land Survey of Finland, licence no 13/MML/14.


Fig. 3. Nickel contents of the till fines (<0.06 mm) in the Savukoski-Pelkosenniemi area. Bedrock map © GTK, Basemaps: ©

National Land Survey of Finland, licence no 13/MML/14.

REE contents are low as seen in yttrium contents (Fig. 5; proved to be a good indicator of REEs in gen-

eral in till geochemistry; cf. Sarapää and Sarala 2013) or under detection limit and do not show any indi-

cation of possible potential in the area.

Precious metals instead show unique distribution in till geochemistry. High gold contents occur only oc-

casionally and do not form uniform anomaly areas (Fig. 6). Some higher contents seem to relate on the

mafic volcanic rocks with diabse veins in the eastern part of the area where arsenic is also elevated (Fig.

7). Furthermore, in the central and western parts gold seems to have relation with diabase veins in be-

tween quartzite rocks. Indicator elements for gold are arsenic, sulphur and tellurium, and in places radio-

active elements. Platinum contents are the highest in the central and southwestern parts of the study area

(Fig. 8). The highest contents exist in a close connection to the komatites in the centre and the western

side of the komatite zone but not in the areas surrounding the Akanvaara layered intrusion as was sup-

posed. Palladium is distributed as the same way but the anomalous areas are a little bit larger (Fig. 9).

Possible source rocks for platinum as well as palladium would be the black schists and diabase/gabbro

dykes with close connection to mafic volcanic rocks in the Proterotzoic areas.

Main element distribution follows the composition of main lithological units in the bedrock. Other ele-

ments do not show particular interest in the study area.


Fig. 4. Sulphur contents of the till fines (<0.06

mm) in the Savukoski-Pelkosenniemi area.

Bedrock map © GTK, Basemaps: © National

Land Survey of Finland, licence no

13/MML/14.

Fig. 5. Yttrium contents of the till fines (<0.06




13/MML/14.


Fig. 6. Gold contents of the till fines (<0.06




13/MML/14.

Fig. 7. Arsenic contents of the till fines (<0.06




13/MML/14.


Fig. 8. Platinium contents of the till fines

(<0.06 mm) in the Savukoski-Pelkosenniemi

area. Bedrock map © GTK, Basemaps: © Na-

tional Land Survey of Finland, licence no

13/MML/14.

Fig. 9. Palladium contents of the till fines

(<0.06 mm) in the Savukoski-Pelkosenniemi

area. Bedrock map © GTK, Basemaps: © Na-

tional Land Survey of Finland, licence no

13/MML/14.


6 DISCUSSION AND CONCLUSIONS

In this study two till geochemical exploration methods were used in the Savukoski-Pelkosenniemi area. In

both methodological applications the same sampling points and same basal till sampling material were

used. The first method was a conventional till geochemical method that is based on the 250-300 g sample

size of which 5 g subsample of the fine fraction (< 0.063 mm) of till analysed by ICP-OES and GFAAS

after aqua regia digestion. Another method was followed by the NATI’s CROCS technology described in

detailed in appended report (http://www.natires.com/rrs2013-1.htm, referred 7th

May 2014). For that

method till samples of 5 litres were collected from the same points that in the conventional method.

Based on the conventional till geochemical method several areas or chain-like features indicative for dif-

ferent metal mineralisation are possible to recognise in the study area. Elevated contents were particularly

found for Cr, Ni, S, Au, As and PGE (Figs. 2-4, 6-9). Anomaly patterns seemed to follow the main

lithological units in the bedrock, i.e. 1) Cr and Ni; komatite rocks in the north-south oriented contact zone

of Acrhaean and Proterozoic blocks, 2) several base metals, Au, As; both in the Archaean and Proterot-

zoic mafic volcanic rocks, 3) Au, PGE; diabase veins, gabbros and mafic volcanic rocks in the western

parts and 4) Cr, Ni, PGE; mafic volcanic rocks and schists in surrounding areas of the layered intrusion of

Akanvaara in the south-east part of the study area. In places, some structural control relating to faults is

also possible seen like for Au and PGE. Some elevated uranium contents were found mainly in relation to

the Archaean granitoid rocks in the eastern part of the area. Signs of the REE potential in the study area

are low based on this data.

As an overall view, the results show quite short glacial transport of the till material in the basal part of

glaciogenic overburden and prove that this till layer fits perfectly to the till geochemical research in bed-

rock mapping and mineral exploration. Instead, based on these results it is not possible to be sure of the

existence of economic mineralisation in the area because the results were not validated by any way. Only

area where the results are possible to evaluate is the komatite rocks and the layered intrusion of Akan-

vaara in the south-eastern part of the area. In that particular area, the Cr and Ni deposits have been ob-

served during earlier exploration work (Mutanen 1997). It is clearly seen that based on the methods used

in this study it is possible to find that area potential for Cr and Ni exploration.

7 REFERENCES

Johansson, P., Lunkka, J.P. & Sarala, P. 2011. The Glaciation of Finland, in: Ehlers, J., Gibbard, P.L. &

Hughes, P.D. (Eds.), Quaternary Glaciations - Extent and Chronology – A closer look. Elsevier B.V., De-

velopments in Quaternary Sciences, vol 15, chapter 9, pp. 105-116.

Juopperi, H. 1986. Savukoski. Map of Finland; in Finnish: "Savukoski. Suomen geologinen kartta"; 1 :

100 000, bedrock map, sheets 3723 + 4711. Geological Survey of Finland.

Knauf, O. 2012. Susikas gold anomaly confirmation. Geological Survey of Finland, report

C/MT/2012/15.


Mutanen, T. 1997. Geology and ore petrology of the Akanvaara and Koitelainen mafic layered intrusions

and the Keivitsa-Satovaara layered complex, northern Finland. Bulletin of the Geological Survey of

Finland 395, 233 p., 5 app. maps.

Sarapää, O. & Sarala, P. 2013. Rare earth element and gold exploration in glaciated terrain – example

from the Mäkärä area, Northern Finland. Geochemistry: Exploration, Environment, Analysis 13, 131-143.

Documents

Till geochemical research in the Savukoski- Pelkosenniemi ...tupa.gtk.fi/raportti/arkisto/58_2014.pdf · search in the Savukoski-Pelkosenniemi region in eastern Finnish Lapland in