Mineralogy, Petrology and geochemistry of Cu (+Co+As+Au...

GEOLOGIAN TUTKIMUSKESKUS [Ylätunnisteen lisäteksti]

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Mineralogy, Petrology and geochemistry of

Cu (+Co+As+Au) deposits in Kotka Cu-

prospect, Häme Belt

Thair Al-Ani, Sari Grönholm and Janne Hokka


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GEOLOGIAN TUTKIMUSKESKUS KUVAILULEHTI

Päivämäärä / Dnro

Tekijät

Thair Al-Ani

Sari Grönholm

Janne Hokka

Raportin laji: arkistoraportti

Toimeksiantaja

GTK

Raportin nimi

Mineralogy, Petrology and geochemistry of Cu (±Co±As±Au) deposits in Kotka Cu-prospect, Häme Belt.

Tiivistelmä

The Kotka Cu-prospect forms part of Häme Belt, locating between the Pirkanmaa Belt in the north and Uusimaa Belt in the

south. The Häme Belt is a major Volcanic-Dominated Terrain in Southern Finland. This report studies the petrology and ge-

ochemistry of the vein-type Cu-Co-As mineralization hosted by this prospect, focusing on the determination of the quantita-

tive modal abundances of the sulphides and associated minerals.

Optical petrography, Qualitative and Quantitative by Electron Microprobe and feature analysis by using a high-resolution

scanning electron microscope, suggest that Cu-Co-As mineralization within studied prospect takes the form of disseminated,

fracture-fillings and veinlets, to locally volcanogenic massive sulphide, medium to coarse-grained, chalcopyrite> cobaltite>

Co- arsenopyrite> arsenopyrite> pyrite. Lesser quantities of pyrrhotite, sphalerite, goethite, galena, gold and Bi-Ag-telluride

have been observed. Cobaltite is subordinate in all investigated samples. It forms disseminated subhedral to euhedral crystals

that are predominantly intergrowth either in association with chalcopyrite and arsenopyrite, or dispersed in quartz veins,

commonly associated with dispersed sericite, chlorite and biotite assemblage. The associations of REE- and sulphide miner-

alization are closely associated with intense hydrothermal alterations within the sulphides veining, and/or dispersed in quartz

veins cutting through the host rocks at Cu-Kotka prospect.

Whole rock analyses of 670 samples of Cu-Kotka prospect revealed a high copper, arsenic, and cobalt values of Cu (4 –

71500 ppm), As (7 –23300 ppm), Co (4 –2960 ppm) respectively. The cobalt shows good correlation with the base metals

(As, Cu, Fe, Ni, Zn, and S), suggesting the progressive formation of relatively Co-enriched sulphide aggregate as cobalite-

arsenopyrite in contact mainly with chalcopyrite and pyrite.

Karttalehdet

M411

Asiasanat (kohde, menetelmät jne.)

Mineralogy, Volcanic Rx; Cobaltite, Chalcopyrite, Arsenopyrite, Häme Belt

Arkistosarjan nimi

arkistoraportti

Arkistotunnus

81/2018

Kokonaissivumäärä

48 S.

Kieli

English

Hinta

Julkisuus

julkinen

Yksikkö ja vastuualue

MTM

Hanketunnus

Allekirjoitus/nimen selvennys

Thair Al-Ani

Allekirjoitus/nimen selvennys

Sari Grönholm and Janne Hokka


10.12.2018

Sisällysluettelo

Kuvailulehti

1 INTRODUCTION 1

2 REGIONAL GEOLOGY 3

3 AEROGEOPHYSICAL SURVEY 4

4 COBALT CRITICAL TO LITHIUM-ION BATTERY 7

5 MATERIALS AND METHODS 9

6 RESULTS 10 6.1 Petrology and mineralogy of the sulphide-bearing rocks 10

6.2 Modal Mineralogy 19

6.3 Microchemistry of ore and associated minerals 19

7 GEOCHEMICAL CHARACTERISTICS 42

8 DISCUSSION AND CONCLUSIONS 47

9 REFERNCES 47

KIRJALLISUUSLUETTELO

GEOLOGIAN TUTKIMUSKESKUS [Ylätunnisteen lisäteksti] 1

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1 INTRODUCTION

The Kotkajärvi is the old Cu target of Outokumpu Oy and Rautaruukki Oy (Isomäki 1983, Kinnunen

1987, 1990). The target is located about 25 km west of the Hämeenlinna center (Fig. 1). The first dia-

mond drilling program by Outokumpu Oy and Rautaruukki Oy have been made in the period of 1986-

1987, four boreholes (R1-R4) with a total depth of 581 m were drilled with anomalous to high-grade cop-

per mineralization. The highest concentration of these metals has been noted in R1 20,9m@0,537% Cu

and R4 6,3m@0,358% Cu. In R3 0,7m La 0,228%, Ce 0,356%, Pr 0,039 % and Nd 0,104%. In R3 was

found Co 0,136%/0,55m (Kinnunen 1987, 1990).

GTK started exploration by mapping the bedrock, geochemical till sampling and geophysical measure-

ments (magnetic, electromagnetic, IP and VLF-R gravimetric measurements) from 2011 to 2014 in the

Hämeenlinna, Southern Finland. The Kotkajärvi research area was drilled by GTK in 2014 to 489.3 m,

2015 to 407.1 m and 2016 to 700m, totalling 1596.4 (Fig. 2). The highest concentration of Cu and Co has

been in R39 0,95m@7,15% Cu and in R38 0,65m@0,3% Co. In addition to the Cu in potential, Kotkajär-

vi area shows a high potential for REE mineralisation associated with sulphides. The work was done as a

part of Critical Minerals project in 2016. Al-Ani and Grönholm, 2016 reported that the main mineraliza-

tion in Kotkajärvi metavolcanics are grouped into two main ore enrichment zones namely sulphide min-

eralization and REE mineralization. The sulphide mineralization occurs either as low-grade dissemina-

tions or less commonly in small massive pockets, and comprise sphalerite, galena, chalcopyrite, pyrrhotite

and pyrite. REE mineralization and apatite, which usually consists of altered chlorite, sericite, epidote,

calcite and clay minerals; associated with allanite, bastnäsite and apatite. Apatite and allanite volumetri-

cally the most important sink of light rare earth elements (LREEs) in this deposit, occurs as disseminated

grains, pockets, veins, and stringers in chlorite- rich rocks as basaltic andesite and basaltic tuff. The alter-

ation zones in some selected cores M4112016R47/73.85-74.85 are rich in REE contents @0.5% ΣREE),

M4112016R48/83.70-84.70 @ 0.8% ΣREE, M4112016R49/52.20-53.20 @ 0.7% ΣREE and

M4112016R49/65.70-66.80@ 0.8% ΣREE.

The Finnish Government increases the funding framework of the Geological Survey of Finland (GTK) by

one million euros (held on 11 April 2018), to identify the battery mineral resources and potential in order

to strengthen Finland’s battery cluster. The previous work has confirmed the presence of considerable

high‐grade copper‐cobalt mineralisation at the Kotkajärvi, and recent exploration work and more core di-

amond drilling have given us even greater confidence the Cu-Co mineralisation extends considerably fur-

ther than previously outlined.


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Fig. 1 Location map of the studied area


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Fig. 2 Geologic map showing location of target area and the drill holes locations.

2 REGIONAL GEOLOGY

Regional geology of The Kotkajärvi area forms part of the Paleoproterozoic Svecofennian island arc

complex of southern Finland, and belongs to the Forssa Group in the western part of the Häme Belt, lo-

cating between the Pirkanmaa Belt in the north and Uusimaa Belt in the south (Fig. 3). The Forssa Group

is composed of volcanic and mainly politic sedimentary rocks. According to Saalmann et al. (2009), the


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age of the felsic volcanic rocks of the Forssa group is 1881 ± 3 Ma. The rocks were metamorphosed in

amphibolite facies conditions at ca. 1.88–1.86 Ga, and the peak of metamorphism took place at 1.83 Ga,

during the late Svecofennian metamorphic events. Main rock types of the Kotkajärvi area are mainly

composed of felsic and intermediate volcanic rocks (trachyte and trachyandesite) with common occur-

rences of basic volcanic rocks (basalt, trachybasalt and basaltic andesite). The plutonic rocks are granodi-

orites associated with porphyritic rocks (volcanic lava flows); and tuff and related rocks (volcanic pyro-

clastics). Kotkajärvi drillings revealed a sequence of volcanic rocks, which are indicated as an aeromag-

netic anomaly in the granodiorite area on the map sheet M4113 (Fig. 3).

3 AEROGEOPHYSICAL SURVEY

Airborne survey and geophysical work has identified potential for Co-Cu and associated mineralization

on the Hämeenlinna area by Geological Survey of Finland (GTK). Specifications of the survey are given

in Table 1. Geophysical parameters measured were the Earth’s magnetic field, the electromagnetic field

(four-frequency system with frequencies of 0.9, 3, 12, and 25 kHz), and natural gamma radiation. The

aeroelectromagnetic (AEM) data of higher frequencies (14 kHz) were used to delineate shallow subsur-

face conductors and lower frequencies to reveal deeper structures and magnetite-bearing conductors. The

measurement data were interpolated into grids with a pixel size of 50 m × 20 m.

As part of a research and ore evaluation mapping program, which have recently formed GTK’s most im-

portant gold potential mapping in the area of Kotkajärvi, Hämeenlinna area. The measurement systems

and data processing are described in Leväniemi and Grönholm (2016). Geophysical parameters measured

were the Earth’s magnetic field, the electromagnetic field (four-frequency system with frequencies of 222,

888, 3552, 14208 Hz), IP and gravimetric measurements The measurement parameters are shown in Table

1 and the small scale map of high resolution aeromagnetic data from the GTK is a guide for the regional

magnetic responses of the area (Fig. 4).

Table.1 Aero geophysical survey specifications

Parameters meas-

ured

Measurement sys-

tems

Flight altitude/

Line spacing

Electromagnetic

system

Total line length

(Km)

Magnetic GSM19W Over

Hauser 50 m / continuous

32

EM Apex Max/Min 50 m / 20 m

Frequencies: = 222,

888, 3552, 14208

Hz

32

IP Scintrex IPR-12 50 m / 20 m Dipoli-dipoli, n=3,

a=20 32

Gravimetric CG3-Autograv 50 m / 20 m

9


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Fig. 3 Geological map of southern Finland (modified after Korsman et al. 1997); PB = Pirkanmaa Belt,

HB = Häme Belt, UB = Uusimaa Belt.


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Fig. 4 Regional aeromagnetic image of Hämeenlinna Kotka area. (After Leväniemi and Grönholm,

2016).


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4 COBALT CRITICAL TO LITHIUM-ION BATTERY

Cobalt is a strategic metal used in high-temperature steels, magnets, lithium-ion batteries, and other in-

dustrial applications. Most lithium-ion batteries for portable applications are cobalt-based. Cobalt is an

essential part of the cathode within lithium ion batteries and is considered crucial in the switch to electric

mobility and greener generation and storage of energy (Fig. 5).

Cobalt has recently seen a spectacular price rise from 25,000 to 60,000 USD, because of its use in some

types of high performance lithium ion batteries, most importantly, those powering the rapidly growing

automobile applications. The change in usage has been spectacular. In 2015, 40% of cobalt production

was used to make rechargeable batteries. However, by 2019 it is expected that this will have risen to 55%.

Cobalt also has application in the high strength magnets used in modern fixed field electric motors, in su-

per alloys such as jet engine turbine blades, catalysts and pigments. Approximately 97% of the world’s

supply of cobalt comes as a by-product of nickel or copper production. Nearly half the cobalt production

as a by-product of copper mining is out of Africa and predominantly from the Katanga province of the

DRC, which has an estimated 50% of world cobalt Reserves. Most of the remainder is a by-product of

nickel laterite production distributed in various, mostly tropical areas.

Fig. 5 Cathode crystalline of lithium cobalt oxide has 'layered' structures.

Finland hosts many cobalt-bearing ore deposits, and in 2012 cobalt was produced from four mines:

Talvivaara, Kevitsa, Hitura, and Kylylahti (Shedd 2014). Moreover, Finland is a major refined cobalt

producer, with cobalt concentrate being imported from Russia, the Democratic Republic of Congo, Aus-

tria, South Africa, and Germany, in addition to the domestic mine production (Tulli 2013). The cobalt-

bearing deposits in Finland fall into four main categories (FODD 2013): (1) magmatic Ni-Cu-PGM de-

posits that contain cobalt (e.g, Kevitsa, Hitura, Kotalahti), (2) orogenic Au-Cu-Co deposits (e.g., Juoma-

suo, Haarakumpu), (3) VMS-type deposits (e.g., Pahtavuoma), (4) polygenetic deposits (e.g., Talvivaara,

Outokumpu, Kylylahti), and (5) Häme Belt were estimated volcanogenic massive sulphide (VMS) cop-

per-zinc, orogenic gold, porphyry copper and synorogenic intrusive nickel were carried out for the Häme

Belt area in 2015 (Rasilainen and Eilu, 2016).


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Cobalt mine production in 2016 was ca. 2 500 t or 3 % of global production (Kevitsa, Kylylahti and Ter-

rafame mines). In addition Kevitsa and Terrafame nickel production exceeded 20 000 t in 2016

These three mines contain 113 000 t cobalt reserves of which over 80 % at Terrafame mine. This far ex-

ceeds the current annual global cobalt production and provides raw material for decades to come

Cobalt resources in these mines are over 370 000 t (incl. Reserves). Total known resources in Finland ex-

ceed 400 000 t. Sakatti Ni-Co-Cu-PGE (AA Sakatti Mining Oy) deposit may significantly increase the

Ni and Co resources in future (Fig. 6). The mine could be in production by late 2020s

Fig. 6 Major Co resources in Finland. Number 1 refers to Terrafame, Nr 2 Kevitsa and Nr 3 Kylylahti.

Sakatti is shown with big green cross near Kevitsa.

Minerals containing cobalt as an essential element display systematic trends in their diversity and

distribution. The 66 cobalt-bearing minerals occur in crustal environments, 26 species of primary Co


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minerals which are hydrothermally deposited chalcogenides, while 44 secondary cobalt minerals are

resulted from alteration of other Co-bearing phases, principally by oxidative weathering, hydration,

and/or other forms of alteration.oxides and incorporate hydrogen (Hazen et al., 2017). We identify the

most common types of Co-bearing minerals in Table (2).

Table 2 The most common Co-bearing minerals and localities with the greatest diversity of cobalt

minerals.

Name Group Formula Composition Example deposits

Erythrite Arsenate Co3(AsO4)2.8H2O Co=41.55, As=38.39,

H=24%

Daniel Mine, Germany;

Bou Azzer, Morocco

Skutterudite Arsenide (Co,Ni)As3 Co=17.9, Ni=5.9,

As=76.1%

Skutterud Mines, Norway;

Bou Azzer, Morocco

Cobaltite Sulphosalt CoAsS Co=35.5, As=45.2,

S=19.3%

Sudbury, Canada; Broken

Hill, NSW, Australia

Carrollite Sulphide Cu(Co,Ni)2S4 Co=28.6, Cu=20.5,

Ni=9.5, S=41.4%

Chambishi, Copperbelt,

Zambia; Carroll County

MD, USA

Linnaeite Sulphide Co+2Co+32S4 Co=58, S=42% Bou Azzer, Morocco,

Norilsk, Russia

Asbolite Oxide (Co,Ni)(MnO)2•n(H2O) Ca=3.4, Mn=59.4,

Co=4.2, Ni=12.5,

H=16.4%

Koniambo Massif, New

Caledonia

5 MATERIALS AND METHODS

The petrographic studies were carried out from the 25 drill core samples (Fig. 7) to measure the micro-

structures, texture, and mineralogy of Co-Cu-As-mineralization phases, by using ore microscope with re-

flected and transmitted light at different magnifications such as 2.5X, 5X, 10X and 20X objectives. Eight

thin sections were examined by using a Petrographic Microscope (LEICA DMLP) equipped with a digital

camera (Leica).

For the purpose of the high resolution SEM studies the polished thin sections were carbon coated to a

thickness of 25 nm using an EMITECH 960L evaporation-coating unit. Investigation of samples by scan-

ning electron microscopy (SEM) allows detailed identification of individual minerals, such as grain size

and distribution of grain size, grain morphology and association and the relative abundance of minerals in

the investigated sample. X-ray feature analysis, particle-by-particle scanning electron microscopy and

point count of more than 4000 grains per slide were integrated to provide the percentage of the sulphide

minerals in the studied samples. These analyses were performed at the Research Laboratory (GTK) - Es-

poo with a JEOL JSM 5900 LV with a fully automated EDS and BSE detection system.


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Minerals chemistry of Cu-Co-As-Fe sulphides and other accessories were analysed using the Cameca SX

100 Electron Probe Micro Analyser (EPMA) at the research laboratory of the Geological Survey of Fin-

land (GTK). Different accelerating voltages used for the minerals analyses including: accelerating voltage

= 15 Kv, beam current & diameter = 20 nA & 5 µm respectively (for main minerals), accelerating voltage

= 20 Kv, beam current & diameter = 40 nA & 1 µm respectively (for sulphides), and accelerating voltage

= 20 kv, beam current & diameter = 40 nA & 5 µm respectively (for REE-minerals). Polished thin sec-

tions coated with carbon were used for the analysis. The mineral analysis are presented as oxide-weight

percent (wt %) and atomic %. X-ray intensity maps, obtained in the Electron Probe Micro Analyser (EP-

MA) electron microprobe, showing distributions of selected elements in cobaltite-arsenopyrite. X-ray

maps of As (As La), Fe (Fe Ka), Co (Co Ka) and S (S Ka) were was obtained using 20 kV accelerating

voltage, 60 nA beam current and a dwell time of 50 ms.

Whole rock chemistry was completed at the Labtium laboratory, Finland: aqua regia digestion of the

sample and multi-element analysis can be upgraded by ICP-OES- or ICP-MS- instrumental methods

analysis in specified mineralogical phase e.g. Cu and Co in sulphide- and oxide- minerals (Methods 510P,

M306P and 306PM or 307M). Although aqua regia is a powerful leaching agent, it still produces a partial

dissolution for many elements. The dissolution of silicates and refractory minerals (e.g. baryte, chromite

and other spineless, zircon, cassiterite, and tourmaline) varies depending on different factors. Most of the

sulphide, carbonate and oxide minerals (ore forming minerals) are, however, dissolved. The data will also

give information on alteration and weathering of rock samples. Inductively coupled plasma- - optical

emission spectrometry (ICP- OES) of the Labtium laboratory was used for determining the whole rock

Au, Pd and Pt contents (Method 705P).

6 RESULTS

6.1 Petrology and mineralogy of the sulphide-bearing rocks

Major rock types in studied area include granodiorites and intermediate volcanic rocks with common oc-

currences of felsic tuffs (volcanic lava flows, pyroclastic flow) and metasomatic rocks. The rock samples

contain large, visible grains of plagioclase, quartz and biotite, the groundmass consists mainly of chlorite

and biotite microcrystals. The studied sample rich in the sulphide ore as irregular steam cavities filled by

sulphide ore as chalcopyrite and pyrite (Figs. 7, 8). Petrographic examination shows that the host rocks

are characterised by quartz, feldspar, biotite, chlorite-, carbonate- and sericite-dominated metamorphic

recrystallization and vein-related alteration. The massive, fine grained, originally volcanic basalt rocks

show a few centimetre wide very intense chlorite alteration along the early veins. Intense sericitisation is

also present in the alteration selvages of quartz-dominated veins in felsic rocks (Fig. 9a-c). Chalcopyrite,

cobaltite, arsenopyrite, pyrite, sphalerite, pyrrhotite and galena are the principal sulphide minerals present

(Figs. 9 and 10). The bastnäsite - allanite association and apatite are found as crack fillings and inclusions

in silicate mineral matrix of the host rocks. The occurrence of the gold and Bi-Ag-telluride are intimately

associated with chalcopyrite. On the basis of petrographic analysis by microscope observations and fea-

ture analysis by scanning electron microscopy investigations the principal sulphide minerals documented

at the studied core samples selected from volcanic rocks in the Kotkajärvi area are shown in Tables (2).


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Fig. 7 Diamond drill core tray from Cu-Ni deposits of Kotkajärvi Hämeenlinna. Samples for mineralogi-

cal study are marked in the core boxes.


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Kotkajärvi sulphide deposit is hosted in intermediate volcanic rocks with predominant of felsic tuffs and

metasomatic rocks. Cu-Co-As mineralization within samples takes the form of disseminated, fracture-

fillings and velnlets, to locally volcanogenic massive sulphide, medium to coarse-grained, chalcopyrite>

cobaltite> Co- arsenopyrite> arsenopyrite> pyrite. Lesser quantities of pyrrhotite, sphalerite, goethite, ga-

lena, gold and Bi-Ag-telluride have been observed in thin section (Figs. 9 and 10). The detailed ore mi-

croscopic study reveal that sulphide minerals form euhedral to subhedral crystals as well as fine dissemi-

nations incorporated within quartz, feldspar and biotite crystals. Chalcopyrite as the main copper mineral

in studied samples area, occurs as dispersed euhedral to subhedral coarse gained crystals (up to 1 mm),

inter-grown with cobaltite and arsenopyrite (Fig. 9b, c). Cobaltite is subordinate in all investigated sam-

ples. It forms disseminated euhedral crystals from 50 μm to 1 mm that are predominantly intergrowth ei-

ther in association with chalcopyrite and arsenopyrite, or dispersed in quartz veins, commonly associated

with dispersed sericite, chlorite and biotite assemblage. Arsenopyrite is either dispersed as fine dissemina-

tions or occurs as inclusions in some chalcopyrite and pyrite crystals, commonly associated with cobaltite

(Figs. 9a and 10a). Pyrite is ubiquitous in all investigated samples. It occurs as aggregates and idiomor-

phic crystals up to 0.5 mm across. As-bearing cores of large pyrite crystals are associated with inclusions

of arsenopyrite and chalcopyrite (Figs. 9a and 10a). Gold (Au): It is documented here as a native gold as

inclusions in the quartz gangue or associated with chalcopyrite (Fig. 10e, f).

The sulphide mineralisation at new drilled borehole M4112018R55 in the western part of Kotka Cu-

prospect (Fig. 2), occurs in a hydrothermal sequence (crosscut by scapolite veins), whose lithological

composition is dominated by chlorite + carbonate ± calcic amphibole ± phlogopite ± epidote (allanite)

with pyrite ± chalcopyrite veins (Fig. 11a-f). Petrographic analyses show that this previous assemblages

such as plagioclase, quartz and biotite have been partially replaced by albite ± epidote (allanite) ± phlog-

opite ± chlorite ± carbonate assemblages, which mainly exhibit interstitial textures.

Coarse to medium grained schistose amphibolite rock which contains green-blue hornblende, biotite,

quartz as major constituent and calcite, apatite, allanite, chlorite as accessories (Fig. 12a-d). Secondary

alteration products and accessory opaque minerals are also present as clusters, represented mainly by

magnetite chalcopyrite and minor pyrite (Fig. 12c-d). Chloritization suggests hydrothermal alteration dur-

ing the course of retrogression.

Pyrite, in samples M4112018R55_105.60 and M4112018R55_156.0, and in some parts of the other sam-

ples, occurs as early formed pyrite framboids and small euhedral to subhedral pyrite and locally very

abundant, either isolated in the matrix (Figs. 12a, 13a-f). Pyrite commonly contains inclusions of other

minerals, such as millerite and chalcopyrite. Millerite, the most abundant Ni sulfide, is a late-stage sulfide

that observed as part of the assemblages millerite-pyrite. Usually anhedral in shape, pale brass-yellow

colour, it typically is observed as vein fillings and closely intermixed with pyrite (Fig. 13d, f).


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Fig. 8 Photomicrographs of drill core section (hand specimens) indicating Cu-Fe sulphide mineralization

and associated minerals.


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Fig. 9 Crossed polarized light and reflected light photographs showing the main types of sulphide miner-

alization from Kotkajärvi volcanic rocks. (a) Vein filling of sulphide mineralization within silicate miner-

als, which only pyrite (Py), arsenopyrite (Apy) and chalcopyrite (Ccp) been observed; (b, c) Disseminated

chalcopyrite (Ccp) and cobaltite (Cbt) in quartz veins and all in contact with biotite and chlorite.


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Fig. 10 Reflected light photographs showing the main types of sulphide mineralization from Kotkajärvi

volcanic rocks. (a) Coarse intergrowths of chalcopyrite, cobaltite and arsenopyrite disseminated within

quartz veins; (b) Sulphide veinlet filled with pyrite and arsenopyrite, veinlet filled with very fine-grained

pyrite oriented parallel to foliation of the rock; (c, d) Euhedral and anhedral grains of cobaltite (Cbt) in

association with chalcopyrite (Ccp); (e, f) Cobaltite (Cbt) and arsenopyrite (Apy) associated with chalco-

pyrite (Ccp), sphalerite (Sp), bismuth (Bi), and Au-Ag alloy (Au).


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Fig. 11 Crossed polarized light and reflected light photographs taken from the thin sections of M4112018R55

samples; (a-b) showing assemblages of carbonate (Cal) with chlorite (Chl) ± allanite epidote (Aln+Ep) ± phlogo-

pite (Phl); (c-f) Coarse intergrowths of chalcopyrite and pyrite disseminated within carbonate (Cal) ± chlo-

rite (Chl) ± allanite epidote (Aln+Ep) matrix.


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samples; (a-b) coarse green hornblende associated with calcite (Cal), chlorite and contains inclusions of magnetite

(Mag); (b) Coarse apatite (Apt) in contact with calcite; (c-d) Chalcopyrite (Ccp) disseminated within carbonate

(Cal) ± chlorite (Chl) matrix; (e) Euhedral pyrite (Py) with inclusions of millerite (NiS);(f) Partial replacement of

plagioclase and quartz phenocrysts.


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samples; (a-b) Chalcopyrite and pyrite disseminated within carbonate (Cal) ± chlorite (Chl) matrix;(c-f) Pyrite

(Py) with millerite inclusions disseminated within carbonate (Cal) ± chlorite (Chl) ± allanite epidote (Aln+Ep) ma-

trix.


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6.2 Modal Mineralogy

The quantitative modal abundance data provided by x-ray feature analysis in scanning electron microsco-

py SEM on the heavy mineral proportions may be used to calculate sulphide mineral indices in selected

samples. Table 2 presents the MLA results for the modal mineralogy of Kotkajärvi sulphide deposit in

selected the thin section and the heavy mineral grain counts. The feature analysis data document enrich-

ment factors (% mineral, as given in Table 3 and histograms) and modal abundances of studied samples.

A total of 3730 heavy mineral grains were analysed in the thin section of sample M4112014 R33_57.65

chalcopyrite and oxidised chalcopyrite (CPY) were identified in 3730 heavy mineral particles by the SEM

analysis of sample M4112014 R33_57.65, the absolute abundances of the sulphide minerals are chalcopy-

rite 43%, oxidized chalcopyrite (CPY) 36%, cobaltite 9%, arsenopyrite 6%, Co-arsenopyrite 4% and py-

rite ~1%. Cobalt-rich variety of arsenopyrite (62%), arsenopyrite (31%) and cobaltite (7%) are the most

abundant sulphides in the sample M4112014 R34_105.5, while the cobaltite (~80%) is the most abundant

sulphides in the sample M4112014_R34_110.40 (Table. 3 and histograms).

6.3 Microchemistry of ore and associated minerals

The mineral chemistry was determined by EPMA point analysis (Table 4), though not all minerals detect-

ed by image analysis were detected and analysed by EPMA. The most abundant mineral is quartz, biotite,

feldspar (K-feldspar and albite), followed by chlorite, sericite and apatite (Table 4).

The opaque mineral content of the studied rocks is dominated by magnetite and ilmenite, with magnetite

as the most abundant. The sulphide present in the studied rocks of Kotka Cu-prospect is dominated by

Cu-Co-As mineralization and seemed to take form of disseminated, fracture-fillings and velnlets. These

venlets are composed of chalcopyrite> cobaltite> Co- arsenopyrite> arsenopyrite> pyrite, Bi-minerals.

Chemical composition of main sulphides minerals are summarized in Table 5.

Magnetite shows different types of intergrowths and aggregates. The grain size varies from <0.1 mm up

to several mm. Magnetite shows anhedral grain shapes, but subhedral grains are also observed magnetite

is often intergrown with ilmenite (Fig. 14a). Intergrown of magnetite with sulphides (pyrite and chalcopy-

rite) and allanite is also common in the some studied samples (Fig. 14b, c).

Chalcopyrite is abundant in nearly all of the studied samples. It occurs as anhedral and coarse grains in-

tergrown with pyrite, cobaltite and arsenopyrite (Fig. 15a-f). Chalcopyrite is observed coexisting with py-

rite, cobaltite and arsenopyrite as well as gold and Bi-minerals (Figs. 15 and 16). EPMA analyses of chal-

copyrite are Cu: 34.40 wt%; Fe: 30.70 wt% and S: 34.30 wt% (Table 6). In some samples chalcopyrite

has inclusions of sphalerite (Fig. 15a), silver telluride (Ag2Te) (Fig. 15d) and gold (15f). The microprobe

analyses of chalcopyrite show elevated Ni = 0.01 wt%, Co = 0.03 wt%, Zn = 0.03 wt%, As = 0.12 wt%.

Au = 0.1 wt% and Ag = 0.02 wt.% (Table 6).

Pyrite is the main iron sulphide and occurs in large masses but has been altered in some parts of the de-

posit to pyrrhotite. Cubic and euhedral pyrites vary widely in morphology across the sample suite (Figs.

15c, 16a). Fine-grained cubic pyrites often appear as inclusions within chalcopyrite (Figs. 15, 16). In

some instances, porous euhedral grains display evidence of multi-stage pyrite growth zones (Fig. 16a-f).

Some euhedral grains also appear associated with lamellar framboidal growth of pyrrhotite (Fig. 16b, c).


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These are identifiable by the appearance of porous microcrystals within the centre of grains (Fig. 16d).

Anhedral pyrite grains are common in samples where massive pyrites are observed but also coexist with

idiomorphic cubic pyrite or as single grains within chalcopyrite (Fig. 16e).

Similar to other pyrite morphologies, anhedral pyrite grains were observed intergrown with cemented py-

rite, chalcopyrite and REE-minerals as bastnäsite (Fig. 16f). Pyrrhotite shows lamellar texture (Fig. 16),

in which the chemical composition of the lamellae is little variable (Table 6). The microprobe analyses of

pyrite (Table 5) gave the following composition (based on 50 analyses): 46.6 - 48.5 wt.% Fe, 51.1 - 52.8

wt.% S, 0-0.70 wt.% Ni and no concentration of any other element above 0.70 wt.%. The average con-

centrations of these minor constituents (0.01 wt. % Zn, 0.06 wt. % Cu, 0.04 at. % As).

Arsenopyrite was found as inclusions, several µm in size, in pyrite (Fig. 17a), or as grains with similar

sizes (usually up to 1 mm) attached to the chalcopyrite surface (Fig. 17b, c), or as isolated grains up to

500 mm in size (Fig. 17 d, e). Two generations of arsenopyrite were identified. The older one (arsenopy-

rite-1) forms euhedral crystals (up to 100 mm in size) that are homogeneous on BSE. They are usually

disseminated within the altered host rock and associated with pyrite and chalcopyrite (Fig. 17a-c). Arse-

nopyrite-2 forms crystals up to 1mm in size (typically several tens to several hundreds of µm). It forms

isolated crystals, aggregates of arsenopyrite crystals and show cobalt-rich variety of arsenopyrite over-

growths always forms the core of the aggregate (Fig. 17a, b, c). On BSE images, the arsenopyrite grains

with sector-zoned cores and growth-zoned rims were frequently observed, with a Co-rich core and As-

rich rim, over which they locally predominate (Fig. 17c-f). Cobalt-rich variety of arsenopyrite in studied

samples, in which the cobalt may replace as much as 12 percent of the iron.

The composition of the studied arsenopyrite-1 (15 EPMA data, samples M4112014 R38_78.0 and

M4112014 R38_78.50, Table 7) grains varies slightly in terms of its arsenic and sulphur contents. The As

content ranges from 29.8 to 32.9 at. % (Fig. 16 a, b) and S content varies from 32.8 to 36.0 at. %. The

measured data indicate a negative correlation of S and As, in good agreement with the theoretical substi-

tution mechanism of As and S in arsenopyrite solid solutions. The Fe content is constant and with lim-

ited range value from 33.8 to 34.1 at. %. A relatively low Co content was found in all the analysed arse-

nopyrite-1 grains; Co contents varies from 0.1 to 0.4 at. % (Table 7).

The composition of the arsenopyrite-2 (30 EPMA data, sample M4112014 R38_78.0, R38_78.50 and

Kotkajärvi R1_59.75, Table 8) grains is more variable and more As-deficient than has been previously

found for arsenopyrite-1 (Fig. 8). The data are, however, still in good agreement with the theoretical sub-

stitution mechanism for As and S in arsenopyrite. The As contents range from 31.8 to 37.4 at. %, S from

28 to 33.8 at. % and Fe content is also variable, ranged from 21.0 to 30.8 at. %. Cobalt-rich variety of

arsenopyrite in studied samples, in which the cobalt may replace as much as 12 percent of the iron. A

high Co content was found in all the analysed arsenopyrite-2 grains; none of the analysed grains has a Co

content < 9 at. %. The Co contents in the majority of the studied arsenopyrites ranges from 3.5 to 12.9 at.

%, the highest content occurs in the core of arsenopyrite crystals (Fig. 17e, f). Many grains of arsenopy-

rite in which cobalt partially replaces iron is called cobaltian arsenopyrite; those in which the Co: Fe ratio

lies between 2:7 and 3:5. In the application of experimental results of Kretschmar and Scott (1976) for

temperature estimation, the intergrowth type of arsenopyrite is of vital importance. The As content ana-

lysed of arsenopyrite-1(low Co arsenopyrite) grains is on average 31.3 at. % (15 analyses) corresponding


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to a temperature of 380° ± 25°C, whereas the As average in the arsenopyrite-2 (Co-rich arsenopyrite) is

34.4 at.%, indicating a temperature of 490° ± 45°C. High contents of Co appear to result in too high tem-

perature determinations.

Table 3 Modal mineralogy of sulphides determined by X-ray feature analysis, particle-by-particle and

point count in scanning electron microscopy of polished thin sections (CPY oxide = oxidized chalcopy-

rite) .


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Continued Table 3


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Table 4 Chemical compositions of the main and accessory minerals from studied rocks.

Mineral Biotite Chlorite K-feldspar Apatite

Sample M4112014 R34

_110.40

M4112014

R38_78.50

Kotkajärvi

R1_59.75

M4112014

R33_57.65

Kotkajärvi

R1_64.40

M4112014

R38_78.50

SiO2 31.9 35.5 30.8 28.6 25.8 30.0 30.5 64.1 63.1 65.3 62.9 0.3 0.2 0.1

TiO2 0.5 0.4 1.2 1.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0

Al2O3 18.0 13.9 17.8 16.2 18.3 17.0 16.2 17.5 17.9 18.2 18.0 0.0 0.0 0.0

Cr2O3 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

V2O3 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

FeO 32.4 24.7 29.6 33.8 27.9 33.7 33.5 0.1 0.3 0.0 0.2 0.2 0.1 0.2

MnO 0.2 0.1 0.2 0.2 0.1 0.3 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0

MgO 3.2 9.4 4.1 3.6 13.6 4.5 4.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CaO 0.0 0.0 0.0 0.1 0.0 0.2 0.3 0.0 0.0 0.0 0.0 53.8 54.3 54.1

Na2O 0.0 0.0 0.1 0.0 0.0 0.1 0.1 0.0 0.2 0.0 0.2 0.0 0.0 0.0

K2O 8.1 9.2 7.6 5.7 0.0 0.2 0.2 16.3 16.3 15.7 15.7 0.0 0.0 0.0

SrO 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0

BaO 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.2 0.1 0.3 1.0 0.0 0.0 0.0

NiO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

CoO 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

ZnO 0.0 0.0 0.0 0.1 0.0 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0

P2O5 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 41.7 42.1 42.8

SO2 0.0 0.0 0.0 0.0 0.1 0.3 0.3 0.0 0.0 0.0 0.0 0.0 0.0 0.0

F 0.1 0.6 0.0 0.0 0.0 0.2 0.3 0.0 0.0 0.0 0.0 3.8 5.4 5.5

F = O 0.0 -0.2 0.0 0.0 0.0 -0.1 -0.1 0.0 0.0 0.0 0.0 -1.6 -2.3 -2.3

Cl 0.1 0.3 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Cl = O 0.0 -0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

Total 94.8 93.9 91.5 89.8 86.0 86.7 86.6 98.3 98.0 99.5 98.1 98.3 99.9 100

Cobaltite from the Kotka Cu-prospect replaces and overgrows the earlier phases. The cobaltite is found

as idiomorphic to subhedral crystals (100–300 µm in diameter), which display asymmetric zoning r

growth zonation with arsenopyrite and intimately associated with chalcopyrite than other ore minerals

(Fig. 18). Many cobaltite grains also contain inclusions of Bi, Ag and Pb telluride inclusions (Figs. 18a, c,

e). These types of cobaltite can also be replace arseonpyrite-pyrite and overgrow composite grains of co-

baltite and Co-rich arsenopyrite, which they characteristic a sector zoning. This replacement is pseudo-

morphic, and hence does not change the euhedral shape of the grains.

EPMA analyses of cobaltite are S: 33.02-36.84 at.%, Co: 29.88-32.68, As: 29.27-33.16 at.%, Fe: 0.91-

3.34 at.%, Ni 0.04-0.1 at.%, Cu <0.14 at.%, Zn <0.02 at.%, Sb < 0.03, Ag:< 0.02 at.% (Table 9). Cobal-

tite is characterized by extended substitution by Fe in the range 0.91-3.34 at. %. Large cobaltite grains

typically consist of subhedral to euhedral, relatively dark grey to pale grey, weak growth zoning with

asymmetric profiles (Figs. 19a, b, c). In Sample M4112014 R38, three zoning profiles are determined in


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cobaltite grains1, 2 and 5. The profile in micro domain grains show that the Co and Fe content varies

from one lamella to another by up to 1 at.%, but the As and S content remains relatively constant low var-

iables from one lamella to another by less than 1 at.% (Fig. 19).

The cobaltite and Co-rich arsenopyrite grains show a considerable As–S variability from 29.3 to 33.2 at-

om % As in cobaltite grains, but most fall between 31.5 and 33 mole % As, and Co-rich arsenopyrite

would also produce the same negative correlation of arsenic with sulphur identifying a significant substi-

tution of As by S has been detected (Fig. 20a). The plots in the Figure (20b) shows the arsenic content as

a function of Co content in arsenopyrite and cobaltite intergrowth grains. Mineral association of these two

minerals- cobaltite and arsenopyrite- in studied rocks, which grew during the metasomatism of the ore,

replacing and overgrowing the previously deposited phases. Most of the analysed arsenopyrites are S-

rich, based on their compositional trends in Co-S-As space, whereas cobaltite occurs in centre of the sys-

tem (Fig. 20c). The Co-Fe-As space shows that Fe substitute for Co in different proportions, depending

on the paragenetic situation (Fig. 20d).

Arsenic, cobalt, iron and sulphur contents can be mapped using EMPA to interpret the crystallization pro-

cesses of cobaltite. Figure 21 shows X-ray element maps, obtained by electron microprobe, of a selected

cobaltite grains. Cobaltite shows irregular zonation in terms of the distribution of arsenic and cobalt, but

iron and sulphur show a visible negative correlation (Fig. 20, M4112014 R34 _110.40 grains 1 and 2).

Cobaltian arsenopyrite intergrowth displays a noticeable zonation that includes a Co-rich core followed

by a band-like enrichment of As in the mid-section, whereas Fe and S are enriched towards the rim (Fig.

20, M4112014 R38 _78.50 grain 2).

Nickel sulphides such pentlandite (Fe, Ni)9S8 and millerite (NiS) have observed in some samples. Miller-

ite (NiS) occurs as granular aggregates, up to 50 µm in diameter associated mainly with pyrite and chal-

copyrite (Fig. 14d). Pentlandite is most often as inclusions within chalcopyrite and pyrite, together with

cobaltite (Fig. 15d).

Gold It is documented here as a native gold as inclusions in the quartz gangue or associated with chalco-

pyrite (Fig. 10e, f). Gold is found also associated with arsenopyrite. The gold grains are irregular to sub

rounded with extensively pitted surfaces (Fig. 22a-f). The electron microprobe data show that all the

grains carry high Au content with a range of 65.8 to 75.3 atomic% and Ag content varies from 23.3 to

30.1 atomic%. Cu was detectable in most of the grains, ranges from 0.1 to 2 atomic %, while Hg is pre-

sent in low concentrations less than 0.2 atomic %. Te and Fe were also found as trace element in some

grains (Table 10). The EMPA data do not show any marked core to rim Au/Ag content variation in the

grains from the studied sample Kotkajärvi R1_59.75 (Table 10).

REE-bearing Mineral occurrence of discrete REE-minerals at Cu-Kotka prospect is extremely varied

but they can be generally typified as fine-grained (<50 μm), and occurring as disseminations with sul-

phide and gangue minerals throughout all ore zones in the deposit. They can, however, also be locally

concentrated to macroscopic REE-mineral rich pockets which were identified by Al-Ani and Grönholm

(2016). REE mineralization is associated with sulphide mineralization in the studied Cu-Kotka prospect.

This is evidenced by the occurrence of sulphide minerals (as chalcopyrite, pyrite, arsenopyrite and cobal-

tite) and REE-bearing minerals (monazite, bastnäsite and allanite) within the same deposit (Figs. 23, 24).


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In studied samples bastnäsite occurs in three main forms: within the matrix, as irregular grains, and as

acicular or needle-shaped crystals forming either radial accumulations or intricate cross- cutting grids as-

sociated with sulphides (Figs. 23, 24 a-f). Monazite and allanite were detected in only a few crystals per

thin section, in which they occur in close association with bastnäsite and sulphides (Figs. 23b, d and Fig.

24f, respectively).

The occurrence of REE_bearing minerals and sulfides suggests that fluids in hydrothermal systems, re-

sponsible for sulphide mineralization may have also contained significant REE (Anthony et al., 2003).

The later oxidation/weathering caused dissolution of REE and sulphide minerals and the later precipita-

tion of REE-bearing minerals. This study suggests that the association between bastnäsite (REE) and sul-

phide mineralization is complex, but likely to occur in alkali igneous districts that have seen drastic

changes in fluid physio-chemistry during the lifetime of the hydrothermal system. The model suggests

that this type of hydrothermal REE- sulphide mineralization may be intimately associated hydrothermal

alterations include petrographically identified chloritization, silicification, sericitic and argillic alterations,

with no distinct zonation in the field.

Table 5 Summary of the chemical composition of the main sulphide minerals in Kotkan Cu-prospect. Element (wt %)

Mineral (Points No.) S Cu Fe Ni Co Zn As Total

Min - Max Min - Max Min - Max Min - Max Min - Max Min - Max Min - Max

Average Average Average Average Average Average Average

Cobaltite (73) 19.0 - 21.8 0 - 0.16 0.93 - 3.43 0.04 - 1.1 31.9 - 35. 0 0 - 0.03 40.5 - 44.9 98.7

19.75 0.02 2.36 0.33 32.31 0.00 43.85 99.6

Chalcopyrite (28) 34.1 - 34.7 33.9 - 34. 8 30.0 - 31.0 0 - 0.01 0 - 0.03 0 - 0.03 0 - 0.12 98.7

34.28 34.43 30.69 0.00 0.01 0.01 0.03 99.5

Pyrite (50) 51.1 - 52.8 0 - 0.70 46.6 - 48.5 0 - 0.02 0 - 0.03 0 - 0.02 0 - 0.33 98.6

52.10 0.06 47.30 0.01 0.00 0.01 0.04 99.6

sphalerite (15) 33.0 - 33.3 0.24 - 1.50 6.93 - 9.30 0 - 0.01 0 - 0.02 55.4 - 57.5 0 - 0.04 98.3

33.14 0.69 7.90 0.00 0.01 56.61 0.01 99.1

Arsenopyrite (27) 18.3 - 21.9 0 - 0.60 29.2 - 35.9 0 - 0.04 0.09 - 5.80 0 - 0.02 40.9 - 46.4 98.6

20.34 0.09 33.96 0.01 1.55 0.00 43.73 99.8

Co-Arsenopyrite (35) 15.7 - 19.7 0 - 0.53 20.9 - 28. 8 0 - 0.05 6.43 - 13. 56 0 - 0.03 43.4 - 49.1 98.6

18.00 0.06 25.52 0.02 9.26 0.00 46.75 99.7


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Fig. 14 Back-scattered electron images of magnetite with associated minerals in selected samples of Cu-

Kotka prospect; (a-b) Magnetite (Mag) coarse grains in contact with ilmenite (ilm), pyrite (Py) and co-

baltite (Cbt): (c) Magnetite aggregates associated with allanite (Aln); (d) Millerite aggregates associated

with pyrite and chalcopyrite.


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Fig. 15 Back-scattered electron images of sulphides with associated minerals in selected samples of Cu-

Kotka prospect; (a, b) Chalcopyrite (Ccp) associated with pyrite (Py) and sphalerite (Sp); (c) Prismatic

pyrite (Py) crystal within chalcopyrite (Ccp); (d) Cobaltite (Cbt) and Ag2Te associated with chalcopyrite

(Ccp); € Arsenopyrite (Apy) crystals within chalcopyrite (Ccp); (f) Coarse gold grains (Au) in contact

with chalcopyrite (Ccp) and arsenopyrite (Apy).


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Kotka prospect; (a- c) Overgrowths on pyrite (Py) and pyyrohotite (Po), also in contact with molybdenite

(Mlb); (d) Growth zoning in pyrite (Py) and in contact with molybdenite (Mlb); (e) Pyrite (Py) over-

growths with chalcopyrite (Ccp); (f) Pyrite (Py) in contact with chalcopyrite (Ccp) and bastnäsite (Bsn).


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Table 6 Representative analyses of chalcopyrite (Ccp), pyrite (Py) and sphalerite (Sp), EPMA data in

wt.% and at.% Sample M4112014

R34

M4112014

R34

Kotkajärvi

R1

Kotkajärvi

R1

M4112014

R34

M4112014

R34

M4112014

R34

M4112014

R34

M4112014

R34

R34/110.4 R34/78.50 R1_59.75 R1_59.75 R34/78.50 R34 / 110.4 R34/110.4 R34/110.4 R34/110.4

Mineral Ccp_gr1 Ccp_gr2 Ccp_gr3 Py_gr1 Py_gr2 Py_gr3 Sp_gr1 Sp_gr2 Sp_gr3

S (wt%) 34.3 34.2 34.5 52.5 52.3 51.8 33.2 33.2 33.0

Cu 35.0 34.7 34.8 0.01 0.00 0.01 0.76 0.61 0.53

Fe 30.6 31.0 31.0 47.2 47.4 47.2 7.5 7.3 7.2

Mn 0.00 0.01 0.01 0.00 0.01 0.00 0.02 0.02 0.04

Ni 0.00 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00

Co 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01

Zn 0.00 0.00 0.01 0.01 0.02 0.01 57.00 56.6 56.7

Sb 0.00 0.00 0.00 0.01 0.02 0.04 0.00 0.00 0.00

Bi 0.00 0.02 0.03 0.00 0.00 0.00 0.00 0.01 0.07

Te 0.00 0.02 0.00 0.00 0.00 0.00 0.02 0.00 0.00

Cd 0.00 0.00 0.00 0.00 0.00 0.00 0.69 0.67 0.71

Se 0.01 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00

As 0.00 0.00 0.01 0.15 0.12 0.33 0.00 0.00 0.01

Ag 0.00 0.01 0.00 0.00 0.01 0.02 0.00 0.00 0.00

Sn 0.00 0.02 0.00 0.00 0.01 0.02 0.00 0.00 0.00

Total 99.7 99.9 100 99.9 99.9 99.5 99.2 98.4 98.3

S (at%) 49.4 49.23 49.35 65.86 65.70 65.55 50.24 50.61 50.46

Cu 25.3 25.2 25.1 0.01 0.00 0.01 0.58 0.46 0.41

Fe 25.3 25.6 25.5 34.0 34.2 34.2 6.5 6.4 6.3

Mn 0.00 0.01 0.01 0.00 0.01 0.00 0.02 0.02 0.03

Ni 0.00 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00

Co 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Zn 0.00 0.00 0.01 0.01 0.01 0.01 42.3 42.2 42.4

Sb 0.00 0.00 0.00 0.00 0.01 0.01 0.00 0.00 0.00

Bi 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.02

Te 0.00 0.01 0.00 0.00 0.00 0.00 0.01 0.00 0.00

Cd 0.00 0.00 0.00 0.00 0.00 0.00 0.30 0.29 0.31

Se 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00

As 0.00 0.00 0.01 0.08 0.07 0.18 0.00 0.00 0.01

Ag 0.00 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00

Sn 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.00

Total 100 100 100 100 100 100 100 100 100


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Kotka prospect; (a- c) Subhedral arsnopyrite (Apy) grains associated with chalcopyrite (Ccp) and pyrite

(Py); (d-f) Growth zoning characterize arsenopyrite (Apy) grains, with a Co-rich core and As-rich rim.


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Table 7 Representative analyses of arsenopyrite-1, EPMA data in wt.% and at.%

Sample M4112014 R38_78.00 M4112014 R38_78.50

Mineral Apy_1 Apy_2 Apy_3 Apy_4 Apy_5 Apy_1 Apy_2 Apy_3 Apy_4 Apy_5

S wt.% 20.70 20.39 20.26 20.88 20.68 20.92 21.71 19.34 19.15 21.92

Cu 0.00 0.02 0.00 0.00 0.02 0.00 0.02 0.02 0.03 0.01

Fe 35.18 35.09 35.25 35.50 35.33 35.57 35.58 34.89 34.42 35.87

Ni 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.01 0.00 0.00

Co 0.16 0.14 0.09 0.17 0.38 0.25 0.35 0.26 0.39 0.29

Zn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01

Sb 0.04 0.00 0.01 0.11 0.09 0.08 0.06 0.00 0.00 0.07

Te 0.02 0.01 0.01 0.02 0.00 0.02 0.00 0.01 0.00 0.00

As 43.43 43.52 44.14 43.03 43.41 43.27 42.37 45.24 44.79 42.35

Ag 0.02 0.00 0.00 0.01 0.00 0.00 0.01 0.00 0.03 0.01

Sn 0.03 0.03 0.02 0.03 0.00 0.00 0.00 0.01 0.00 0.01

Total 99.6 99.2 99.8 99.8 99.9 100.1 100.1 99.8 98.8 100.5

S at.% 34.73 34.41 34.08 34.91 34.60 34.85 35.89 32.84 32.83 36.03

Cu 0.00 0.01 0.00 0.00 0.01 0.00 0.02 0.02 0.03 0.01

Fe 33.88 34.00 34.05 34.07 33.93 34.02 33.77 34.01 33.88 33.86

Ni 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.01 0.00 0.00

Co 0.15 0.13 0.08 0.15 0.35 0.23 0.31 0.24 0.37 0.26

Zn 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01

Sb 0.02 0.00 0.00 0.05 0.04 0.04 0.03 0.00 0.00 0.03

Te 0.01 0.00 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00

As 31.18 31.43 31.77 30.79 31.07 30.85 29.97 32.87 32.87 29.79

Ag 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02 0.00

Sn 0.01 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.01

Total 100 100 100 100 100 100 100 100 100 100


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Table 8 Representative analyses of arsenopyrite-2, EPMA data in wt.% and at.%

Sample M4112014 R38_78.50- grain1 M4112014 R38_78.50- grain 2 Kotkajärvi R1_59.75- grain 4

Apy_1 Apy_2 Apy_3 Apy_4 Apy_1 Apy_2 Apy_3 Apy_4 Apy_1 Apy_2 Apy_3

S wt. % 17.32 17.20 18.36 18.26 16.90 16.96 18.60 15.95 15.72 15.95 18.12

Cu 0.01 0.04 0.01 0.01 0.01 0.00 0.02 0.53 0.52 0.53 0.17

Fe 22.98 20.90 25.21 25.62 23.22 22.94 25.89 23.78 24.42 23.78 26.58

Ni 0.02 0.03 0.01 0.00 0.02 0.01 0.02 0.02 0.02 0.02 0.01

Co 11.79 13.57 9.57 9.36 11.13 11.51 9.07 10.28 9.50 10.28 8.35

Zn 0.01 0.01 0.02 0.00 0.00 0.00 0.00 0.00 0.03 0.00 0.00

Sb 0.02 0.03 0.04 0.08 0.03 0.03 0.01 0.12 0.13 0.12 0.36

Te 0.01 0.02 0.04 0.03 0.01 0.00 0.00 0.00 0.00 0.00 0.00

As 47.66 47.87 46.51 46.48 49.05 48.20 46.29 48.98 49.12 48.98 46.51

Ag 0.02 0.04 0.03 0.02 0.00 0.00 0.01 0.00 0.00 0.00 0.00

Total 99.86 99.74 99.80 99.88 100.41 99.69 99.92 99.69 99.47 99.69 100.12

S at. % 30.20 30.11 31.66 31.48 29.48 29.73 31.94 28.24 27.95 28.24 31.23

Cu 0.01 0.03 0.01 0.01 0.01 0.00 0.02 0.47 0.47 0.47 0.15

Fe 22.99 21.00 24.96 25.36 23.26 23.09 25.52 24.17 24.92 24.17 26.30

Ni 0.02 0.03 0.01 0.00 0.02 0.01 0.01 0.02 0.02 0.02 0.01

Co 11.18 12.92 8.98 8.78 10.57 10.97 8.47 9.90 9.18 9.9 7.83

Zn 0.01 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0.02 0 0.00

Sb 0.01 0.01 0.02 0.04 0.02 0.02 0.00 0.06 0.06 0.06 0.17

Te 0.01 0.01 0.02 0.02 0.00 0.00 0.00 0.00 0.00 0 0.00

As 35.55 35.85 34.32 34.29 36.62 36.16 34.02 37.11 37.37 37.11 34.31

Ag 0.01 0.02 0.01 0.01 0.00 0.00 0.00 0.00 0.00 0 0.00

Total 100 100 100 100 100 100 100 100 100 100 100

Co/Fe 0.51 0.65 0.38 0.37 0.48 0.50 0.35 0.43 0.39 0.43 0.31


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Kotka prospect; (a- b) The cobaltite (Cbt) assemblage distributed with chalcopyrite (Ccp); (c) Subhedral

coarse cobaltite (Cbt) grain with inclusions of chalcopyrite (Ccp) and Ag-tellurides grains; (d, e) Co-

batite (Cbt) was found enclosed in chalcopyrite in the form of small euhedral or subhedral crystals; (f)

Growth zoning characterize arsenopyrite (Apy) grains with cobaltite (Cbt).


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Table 9 Representative analyses of cobaltite, EPMA data in wt.% and at.%

Sample M4112014 R34_110.40 M4112014 R38_78.50 Kotkajärvi R1_59.75

grains Cbt1 Cbt2 Cbt3 Cbt4 Cbt1 Cbt2 Cbt3 Cbt1 Cbt2 Cbt3 Cbt4

S wt% 19.41 19.44 19.45 19.49 19.80 19.76 19.62 19.56 19.59 19.55 19.63

Cu 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.02 0.02

Fe 2.28 2.62 2.83 2.82 1.53 1.67 1.72 2.83 2.89 2.81 2.08

Mn 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Ni 0.24 0.17 0.24 0.15 0.09 0.06 0.06 0.18 0.19 0.18 0.13

Co 33.13 33.03 32.72 32.89 34.41 34.30 34.19 33.07 32.99 32.99 33.80

Zn 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.01 0.00

Sb 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Bi 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.03

Te 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.01 0.01 0.00 0.00

Cd 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00

Se 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

As 43.92 43.99 43.61 43.75 43.78 43.75 43.89 44.43 44.27 44.28 44.44

Ag 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.01 0.02 0.02

Sn 0.00 0.02 0.00 0.04 0.02 0.02 0.03 0.06 0.00 0.00 0.00

Total 98.99 99.31 98.89 99.16 99.66 99.60 99.52 100.14 99.97 99.86 100.15

S at% 33.65 33.61 33.73 33.71 34.03 33.98 33.81 33.55 33.63 33.61 33.66

Cu 0.00 0.01 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.01 0.02

Fe 2.27 2.60 2.81 2.80 1.51 1.65 1.70 2.79 2.85 2.78 2.04

Mn 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Ni 0.23 0.16 0.23 0.14 0.08 0.06 0.06 0.17 0.17 0.17 0.12

Co 31.25 31.06 30.86 30.94 32.17 32.09 32.05 30.85 30.81 30.85 31.53

Zn 0.00 0.00 0.00 0.00 0.00 0.02 0.00 0.00 0.00 0.01 0.00

Sb 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Bi 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01

Te 0.00 0.00 0.00 0.00 0.01 0.00 0.00 0.00 0.01 0.00 0.00

Cd 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Se 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

As 32.59 32.54 32.35 32.38 32.19 32.19 32.36 32.61 32.52 32.57 32.61

Ag 0.00 0.00 0.01 0.00 0.00 0.00 0.00 0.00 0.01 0.01 0.01

Sn 0.00 0.01 0.00 0.02 0.01 0.01 0.01 0.03 0.00 0.00 0.00

Total 100 100 100 100 100 100 100 100 100 100 100


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Fig. 19 Analytical traverse of chemical profiles for a single cobaltite and Co-rich arsenopyrite grain; (a,

b) BSE images of simple zoning cobaltite grain M4112014 R34_110.40 grain 1; (b, c) M4112014

R34_110 grains 2 and 5 showing oscillatory zoning cobaltite grains. The plots also show elemental con-

centrations vs. distance plot, displaying the variation along the traverse for each measured element.


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Fig. 20 Compilation of cobaltite-arsenopyrite compositions from the studied samples, in terms of atomic

proportions in the Co–As–S and Co–As–Fe triangles and as orthogonal plots of cobalt content as a func-

tion of As and S contents.


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Fig. 21 X-ray element maps, obtained by electron microprobe, of a selected cobaltite grains M4112014

R34 _110.40 grans 1, 2 and M4112014 R38_78.50 grain 2 respectively. The maps show zonation patterns

r specific elements As, Co, Fe and S in zoned cobaltite crystals.


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Fig. 22 Back-scattered electron images of gold with associated sulphides in selected samples of Cu-Kotka

prospect.


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Table 10 Representative analyses of gold grains, EPMA data in wt.% and at.%

Sample Kotkajärvi R1_59.75

Au,

gr1_p1

Au,

gr1_p2 Au, gr1_p3

Au,

gr1_p4

Au,

gr1_p5

Au,

gr2_p2 Au, gr2_p3

Ag,

Au_gr3

Ag,

Au_gr3

Ag,

Au_gr3

Cu wt% 0.71 0.14 0.08 0.08 0.08 0.07 0.07 0.19 0.23 0.22

Ag 19.69 18.60 15.50 14.63 15.13 15.53 15.15 60.72 57.77 54.29

Au 78.73 81.31 84.13 83.36 84.21 83.89 85.36 37.04 41.65 44.65

Hg 0.00 0.00 0.00 0.08 0.00 0.27 0.21 0.17 0.00 0.00

Fe 0.38 0.08 0.02 0.05 0.05 0.07 0.04 0.23 0.05 0.25

As 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00

Sb 0.00 0.00 0.01 0.04 0.02 0.00 0.00 0.23 0.19 0.12

S 0.09 0.07 0.04 0.06 0.09 0.06 0.07 0.06 0.02 0.05

Se 0.00 0.00 0.00 0.00 0.00 0.03 0.00 0.00 0.00 0.00

Si 0.10 0.10 0.11 0.11 0.19 0.13 0.11 0.22 0.09 0.15

Ni 0.00 0.00 0.00 0.01 0.01 0.01 0.00 0.00 0.00 0.01

Bi 0.00 0.00 0.00 0.04 0.00 0.00 0.01 0.13 0.00 0.00

Total 99.7 100 99.9 98.5 99.8 100 100 98.9 100 99.7

Cu at% 1.84 0.36 0.22 0.23 0.22 0.20 0.20 0.39 0.47 0.47

Ag 30.10 29.00 24.86 23.87 24.18 24.80 24.09 73.00 70.76 67.47

Au 65.93 69.45 73.91 74.50 73.72 73.35 74.35 24.38 27.94 30.39

Hg 0.00 0.00 0.00 0.07 0.00 0.23 0.18 0.11 0.00 0.00

Fe 1.12 0.23 0.07 0.16 0.16 0.20 0.13 0.53 0.13 0.60

As 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.01 0.00

Sb 0.00 0.00 0.01 0.06 0.03 0.00 0.00 0.24 0.20 0.13

S 0.44 0.37 0.23 0.33 0.50 0.31 0.35 0.24 0.07 0.21

Se 0.00 0.00 0.00 0.00 0.00 0.07 0.00 0.00 0.00 0.00

Si 0.57 0.58 0.70 0.71 1.17 0.81 0.68 1.03 0.41 0.73

Ni 0.00 0.00 0.00 0.03 0.02 0.02 0.00 0.00 0.00 0.01

Bi 0.00 0.00 0.00 0.03 0.00 0.00 0.01 0.08 0.00 0.00

Total 100 100 100 100 100 100 100 100 100 100


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Fig. 23 Back-scattered electron images of REE-bearing minerals with associated sulphides minerals in

selected samples of Cu-Kotka prospect; (a- b) Monazite (Mnz) and acicular bastnäsite (Bsn) crystals as-

sociated with chalcopyrite (Ccp) and cobaltite (Cbt); ( c-f) Bastnäsite (Bsn) occurs as acicular and spher-

ical aggregates in contact with sulphides as pyrite (Py) and chalcopyrite (Ccp).


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Fig. 24 Back-scattered electron images of REE-bearing minerals with associated sulphides minerals in

selected samples of Cu-Kotka prospect; (a- e) Bastnäsite (Bsn) occurs as acicular or needle-shapes and

spherical aggregates in contact with sulphides as pyrite (Py) and chalcopyrite (Ccp); (f) Allanite (Aln) as

irregular and coarse grains formed due to epidotization process and contains inclusions of molybdenite

(Mlb) and in contact with quartz (Qz).


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7 GEOCHEMICAL CHARACTERISTICS

The major rock types in studied area include granodiorites and basic-intermediate volcanic rocks. The

volcanic rocks with common occurrences of felsic tuffs and metasomatic rocks have spatially associated

with Cu-Co-As mineralization developed along NW-SE intrusions in southern part of Kotkajäirvi. Whole

rock analyses are carried out for 670 samples using high precision Labtium Lab methods (306M, 306P, +

510P, + 705P) applying state-of–the-art instrumentation i.e. XRF, ICP-OES, ICP-MS. A few representa-

tive samples (17) were selected from Cu-Co-As mineralization intrusions. Each was analyzed for major

and trace elements (Tables 11 and 12). Whole rock analyses of 670 samples of Cu-Kotka prospect re-

vealed the presence of trace amounts of As (7 –23300 ppm), Co (4 –2960 ppm), Cu (4 –71500 ppm), Fe

(17000-24400 ppm), Ni (2 – 254), Zn (20 –1480 ppm) and S (20 –133000 ppm); these contents generally

increase as the Co content of the studied samples from Cu-Kotka prospect. Chalcopyrite as the main sul-

phide minerals in studied area are enriched in Co and As, and positive correlations of Co vs. As and Co

vs. Cu were demonstrated (Fig. 25a, b). The cobalt also shows good correlation with Fe and Ni, although

Co vs. Ni plot shows positive correlations at higher Ni values and no relationship was found between Co

vs. Ni with lower Ni contents (Fig. 25 c, d). Zinc shows low level flat trend with increasing Co-contents

with a small population of both Zn- minerals such as sphalerite in studied samples. Cobalt contents corre-

late well with sulphur, suggesting the progressive formation of relatively Co-enriched sulphide aggregate

as cobalite-arsenopyrite

Strip logs were plotted to compare the analytical results from the lab with the XRF and ICP-MS results

using assay data from the Labtium Lab (Figs. 26 and 27). These strip logs demonstrate good correlation

between cobalt, copper and arsenic. However, cobalt appears to be more widespread in and around copper

intervals and cobalt-rich zones also form peripheral to the copper, arsenopyrite-bearing zones (Figs. 26

and 27).


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Table 11. Major and trace elements contents (ppm) of some selected samples from boreholes

M4112014_R33, R34, R37, R38, and R39 in Cu-Kotka prospect.

Borehole M4112014_R33, R34, R37, R38, R39

Sample

R33

57.30-

58.30

R33

75.80-

76.80

R33

82.00-

83.00

R34

109.50-

110.50

R37

92.20-

93.20

R38

77.90-

78.55

R38

77.90-

78.55

R39

65.30-

66.30

R39

95.40-

96.35

R39

96.35-

97.35

Ag 7 2 3 2 1 16 15 1 32 2

Al 60200 65700 81600

77200 49800

68000

68200

As 2390 1160 1500 1690 999 12200 11900 1900 8450 2030

Au - - - 27 - - 438 - 517 -

Ba 271 877 1470 - 2500 247 - 1500 596 1680

Bi 12 3 2 - 1 15 - 1 - 2

Ca 3730 2700 3460 - 7720 33100 - 3040 13400 7600

Co 1070 473 675 1030 635 3040 2960 539 1790 562

Cu 35300 7720 8560 3220 1300 6530 6010 518 71500 4230

Fe 222000 176000 152000 140000 92600 235000 212000 150000 216000 134000

K 17300 35000 55500 - 75000 25800 - 58400 18300 61000

Mg 7670 13300 13700 - 11100 11800 - 13400 7560 13900

Mn 668 745 504 1070 961 612 591 494 335 400

Mo 31 78 2 31 8 1150 1170 217 521 357

Na 141 110 661

1390 916 - 968 327 5170

Ni 18 19 4 14 16 42 44 13 181 37

P 1940 1150 1010 - 1040 1230 - 639 2660 1500

Pb 10 10 10 16 11 84 107 11 190 691

S 42900 15300 11800 7150 8370 128000 130000 11500 133000 25600

Ti 2780 2920 3360 - 2880 2070 - 1630 1550 3830

Zn 60 60 34 719 81 87 - 65 623 946


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Table 12. Major and trace elements contents (ppm) of some selected samples from boreholes

M4112016_R47 and Kotkajärvi_R1 in Cu-Kotka prospect.

Borehole M4112016_R47 Kotkajärvi_R1

Sample R47

77.85-78.05

R47

77.85-78.05

R47

106.70-107.70

R1

56.00-57.00

R1

58.00-60.00

R1

62.00-64.00

R1

64.00-66.00

Ag 1 1 5 2 2 <1 1

Al

56300 53800 44800 41200

As 1580 1550 4270 1370 1770 891 2020

Au 24 22 140 82 85 27 60

Ba 3570 3680 1620 789 669 780 498

Bi 5 5 5 - - - -

Ca 6390 6650 3300 2890 2410 2860 6200

Co 518 530 800 720 1210 590 1340

Cu 456 477 6930 10400 10700 1190 1000

Fe 65200 67700 110000 151000 147000 107000 104000

K 91500 94600 65100 34800 25100 32100 26700

Mg 7610 8020 6180 9160 11900 10000 10400

Mn 618 625 347 915 806 640 572

Mo - - - 147 11 16 17

Na 2440 2490 1880 322 365 292 270

Ni 6 6 34 32 17 14 23

P - - - 1230 893 984 978

Pb 11 12 22 7 7 5 5

S 2210 2300 16600 14200 13900 2290 2560

Ti 1950 2000 1230 2690 2550 2670 2380

Zn 69 71 51 55 58 40 26


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Fig. 25 Representative binary plots showing the variable correlation between Co with some base metals

(As, Cu, Fe, Ni, Zn, and S) in logarithmic scales).


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Fig. 26 Strip log for drillholes M4112014R33, R38 and R39 at the Cu-Kotka prospect, Finland. Note

cobalt assays mirror and extend sulphide mineralized zones.

Fig. 27 Strip log for drillholes M4112016R47 and Kotkjärvi-R1 at the Cu-Kotka prospect, Finland. Note

cobalt assays mirror and extend sulphide mineralized zones.


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8 DISCUSSION AND CONCLUSIONS

The present study has focused on various aspect of cobalt mineralization at Cu-Kotka prospect. The study

was aimed at determination the distribution of Co with the main ore minerals, chalcopyrite, arsenopyrite

and pyrite, as well as identifying information of genetic importance in the host lithologies.

Understanding relationships and variation among trace element distribution, macroscopic and microscop-

ic textures, as well as microchemistry of ore and associated minerals are valuable new evidence for the

cobalt distributions and mineralization at Cu-Kotka prospect, it is also necessary to understand how ore

deposits in Cu-Kotka prospect form.

The Cu-Co-As Kotka prospect is hosted in volcanic suite consists mainly of basic and intermediate vol-

canic rocks with common occurrences of acidic felsic tuffs and the plutonic rocks are granodiorites. Sul-

phides mineralization were represented mainly by chalcopyrite, cobaltite, arsenopyrite and pyrite, form-

ing small pockets (1 mm to 5 cm) and as crack fillings, cutting through the volcanic rocks. Some accesso-

ry minerals such as pyrrhotine, sphalerite, galena, molybdenite, gold and Bi-Ag-telluride also found.

Within a given deposit, cobaltite might coexist with chalcopyrite only, others with arsenopyrite only, and

still others with both chalcopyrite and arsenopyrite. As in most systems, partial melting occurs first where

all three sulphide minerals coexist at a triple point, whereas there is no melting where only two coexist.

The sulphide mineralization Cu-Kotka prospect is epigenetic and was formed by hydrothermal solutions

and metasomatic alteration. Hydrothermal fluids during volcanic activities breaks down feldspar and vol-

canic glass in the primary volcanic host rocks. Evidence of hydrothermal alteration at the Cu- Kotka pro-

spect exhibit by the presence of alteration materials associated with fractures and veins such as chloritiza-

tion sericitization and epidotization with chlorite and sulphides-filled fractures.

Mineral associations, especially bastnaesite (Ce) and sulphides, indicate a genetic link between REE and

sulphide mineralization in in the studied volcanic rocks of Cu-Kotka prospect. These relations suggest

this type of hydrothermal REE-sulphide mineralization may be intimately associated with silicification,

sericitization, chloritization and selective sulfidation as vein-type Cu-Co-As mineralization.

9 REFERNCES

Anthony, J., Bideaux, R., Bladh K., and Nichols, M., 2003, Handbook of Mineralogy. 1st ed, v. 1, Tuc-

son: Mineral Data Publishing, 597 p.

Al-Ani, T. & Grönholm, S. 2016. REE and phosphate minerals in volcanic rocks associated with Cu-Fe

sulphide mineralization in the Kotkajärvi-Kalvola, Southern Finland. Geological Survey of Finland, re-

port 59/2016. 39 p.

FODD Fennoscandian Ore Deposit Database 2013. Geological Survey of Finland (GTK), Geological

Survey of Norway (NGU), Geological Survey of Russia (VSEGEI), Geological Survey of Sweden

(SGU), SC Mineral. Database. [Electronic resource]. Available at: http://en.gtk.fi/ mineral resources/ ex-

ploration.html#. Last accessed 17 August 2015.


MTM yksikkö

Espoo 10.12.2018 81/2018

Grönholm, S. & Leväniemi, H. 2015. Pirttikoski1, lupatunnus ML2012:0040, Hämeenlinna, vuosiraportti

2014. 9 s.

Grönholm, S. & Leväniemi, H. 2016. Pirttikoski1, lupatunnus ML2012:0040, Hämeenlinna, vuosiraportti

2015. 10 s.

Hazen et al., 2017. Cobalt mineral ecology. American Mineralogist, Volume 102, pages 108–116.

Isomäki, O.-P. 1983. Yhdistelmäraportti: Kalvola, Kotkajärvi 2131 03A. Outokumpu Oy, raportti

011/213103A/OPI/1983. 25 s.

Kinnunen, A. 1987. Kaivoslain 19§:n mukainen tutkimustyöselostus Kalvola, Kotka, kaivosrekisterinu-

mero 3252/1. Outokumpu Malminetsintä, raportti 080/213103A/AAK/1987. 3 s. + 5 liitettä.

Kinnunen, A. 1990. Outokumpu Oy:n malminetsinnän raportit (sis. Rautaruukki Oy:n raportteja) , Ra-

portti 030/2121 04 A/AAK/1990.

Kretschmar, U. & Scorr, S.D. (1976): Phase relations involving arsenopyrite in the system Fe-As-S and

their application. Can. Mineral. 14, 364-386.

Rasilainen, K. & Eilu, P. 2016. Assessment of undiscovered mineral resources of copper, zinc, nickel and

gold for the Häme Belt. Geologian tutkimuskeskus, arkistoraportti 94/2015. 62 s.

Saalmann, K., Mänttäri, I., Ruffet, G. &Whitehouse, M. J. 2009. Age and tectonic framework of structur-

ally controlled Palaeproteroic gold mineralization in the Häme belt of southern Finland. Precambrian Re-

search 174, 53−77.

Shedd, K. B. 2014. Cobalt. U. S. Geological Survey, 2012 Minerals Yearbook, (advance release), 19.1–

19.21. [Electronic resource]. Available at: http://minerals.usgs.gov/minerals/pubs/commodity

/cobalt/myb1-2012-cobal.pdf. Last accessed 19 May 2015.

Shedd, K. B. 2015. Tungsten. U. S. Geological Survey, 2012 Minerals Yearbook, (advance release) 79.1–

79.20. [Electronic resource]. Available at: http://minerals.usgs.gov/minerals/pubs/commodity

/cobalt/myb1-2012-cobal.pdf.

Tulli 2013. Uljas ‒ Ulkomaan kauppatietojen jakelu järjestelmä. [Electronic resource]. Available at:

http://uljas.tulli.fi. Last accessed 19 May 2015.

http://minerals.usgs.gov/minerals/pubs/commodity%20/cobalt/myb1-2012-cobal.pdf

http://minerals.usgs.gov/minerals/pubs/commodity%20/cobalt/myb1-2012-cobal.pdf

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