Mineralogical, lithogeochemical and sulfide trace element characteristics of the Hirvilavanmaa Au-only and the base metal-rich Naakenavaara orogenic gold deposits in the Central Lapland belt, northern Finland

The Hirvilavanmaa (Au-only) and Naakenavaara (Cu-Co-Au-Ni) deposits, located only 5 km apart in the Pale-oproterozoic Central Lapland belt (CLB) in northern Finland, represent two types of orogenic gold mineralization that dominate the CLB: (1) Au-only and (2) Au with atypical metal association, respectively. In this study, we compare these deposits in order to pinpoint the origin of differences in their metal associations. The pyrite-rich Hirvilavanmaa and the pyrrhotite-and chalcopyrite-rich Naakenavaara deposits are hosted primarily by ultra-mafic metavolcanic and metasedimentary rocks respectively. Similarities in the deposits include pre-ore albiti-zation of host rocks and ore mineralization-related carbonate and chlorite alteration and quartz ‑ carbonate veins. Ore-related sericite and biotite alteration is prominent only at Naakenavaara. Pyrite and chalcopyrite from the two deposits have a distinct trace element geochemistry; pyrrhotite from Naakenavaara hosts significant Co and Ni concentrations. At Hirvilavanmaa, three pyrite generations with distinct Co/Ni ratios represent the gradual evolution of ore deposition. Hirvilavanmaa can be confidently classified as an orogenic Au deposit with evidence pointing to a mafic metavolcanic rock source for the ore-forming components. At Naakenavaara, our results reveal a complex evolution involving two distinct but spatially coincident mineralizing events. The earliest base metal-rich event started as Co-rich and gradually developed into the main Cu-rich stage; two pyrite types (mean Co/Ni ratios of 12.5 and 762 respectively) are associated with these stages. Subsequently ore zones were overprinted locally by an orogenic Au event that deposited pyrite with low Co/Ni ratios (mean of 0.3). The presence of late gold deposition overprinting earlier base metal-rich ore fits with observations from other base metal ‑ gold deposits from northern Finland.


Introduction
Orogenic Au deposits are among the most economically important ore deposit types in Precambrian greenstone belts (e.g., Groves et al., 2003;Goldfarb et al., 2005;Huston et al., 2012).Typically, orogenic Au deposits are considered as Au-only deposits formed by low-to moderatesalinity carbonic-aqueous ore-forming fluids (Groves et al., 1998;Goldfarb and Groves, 2015).A category of epigenetic-hydrothermal Aurich deposits enriched in base metals also occur in metamorphic provinces and have been termed as orogenic Au deposits with atypical metal association (e.g., Goldfarb et al., 2001).Different models proposed for the genesis of such atypical orogenic deposits include the mobilization of saline basinal fluids under moderate to high-grade metamorphic conditions prior to the orogeny (e.g.Yardley and Graham, 2002;Yardley and Cleverley, 2013;Qiu et al., 2021), and the overprinting of an earlier base metal-rich deposit by later orogenic gold mineralization through the reactivation of the same structures during subsequent events (Groves et al., 2003;Vasilopoulos et al., 2021;Ranta et al., 2021;Raič et al., 2022).The Paleoproterozoic Central Lapland belt (CLB; also known as Central Lapland Greenstone Belt) is the largest mafic-volcanic dominated greenstone province and one of the most important precious and base metal metallogenic belts in the Fennoscandian Shield (e.g., Niiranen et al., 2015).In addition to magmatic Ni-Cu(-PGE) ores, the main type of mineralization in the CLB is orogenic Au, in line with other Precambrian greenstone belts in Finland and globally (Eilu et al., 2007;Eilu et al., 2012;Eilu, 2015;Wyche et al., 2015) (Fig. 1a).However, approximately half of the orogenic Au deposits and occurrences in CLB are also significantly enriched in Cu ± Co ± Ni in addition to Au and have been classified as atypical orogenic Au deposits (e.g., Eilu et al., 2007Eilu et al., , 2012;;Holma and Keinänen, 2007;Holma et al., 2007;Eilu, 2015).The total known gold resources in the CLB exceed 10 Moz, mostly belonging to the Suurikuusikko gold-only deposit, currently the largest Au producer in Europe (Agnico Eagle, 2020).To date only the Saattopora and Pahtavaara deposits (Fig. 1a) have been mined in addition to Suurikuusikko, with two additional deposits (Sirkka, Kutuvuoma) test mined (GTK, 2021).The exploration history of the CLB is relatively short and there is significant potential for new discoveries (Niiranen et al., 2015).This is highlighted by the recent discovery of the Ikkari deposit with an inferred gold resource estimate of 3.95 Moz (Fig. 1a; Rupert Resources, 2021).
The aim of this study is to investigate and compare formation conditions of two Au-rich deposits occurring close to each other along the same structures in the CLB and classified as orogenic.The Hirvilavanmaa deposit represents an example of a Au-only orogenic Au deposit (EUREF Easting 423133.6,EUREF Northing 7515904.5)whereas Naakenavaara represents an orogenic Au deposit enriched in base metals (Cu-Co-Ni) (EUREF Easting 421007.4.EUREF Northing 7510252.7;Fig. 1a-b).In this paper, we present and compare sulfide trace element characteristics from these two deposits supported by petrographical and lithogeochemical observations in order to trace the ore-forming processes and understand whether fluids with different characteristics were responsible for the formation of these two deposits.In addition, we examine whether the deposits have been correctly classified as members of the clan of orogenic gold deposits.

General geology of the CLB
The CLB is part of the larger Karasjok-Kuusamo-Lake Onega greenstone belt that extends from northern Norway to Russian Karelia (Hanski and Huhma, 2005).The supracrustal evolution of the CLB spanned from the early Paleoproterozoic (~2.44 Ga) intracontinental rifting of the Archaean (Karelian) basement, through a prolonged basin evolution stage that was terminated by the Svecofennian orogeny at around 1.92 Ga (Korja et al., 2006;Lahtinen et al., 2005).The supracrustal sequences of the CLB include six main lithostratigraphic groups and several minor suites and lithodemes (Fig. 1c).The Salla and Kuusamo Groups, principally composed of felsic-to intermediate and tholeiitic to komatiitic metavolcanic rocks respectively, were deposited during the repeated intra-continental and continental margin rifting of the Archean basement (ca 2.5-2.1 Ga) linked to the break-up of the Kenorland supercontinent (Lehtonen et al., 1998;Köykkä et al., 2019).The following syn-rift to post-rift stages led to deposition of Sodankylä Group comprising metasedimentary and mafic metavolcanic rocks.The post-rift stage (ca.2.1-1.92Ga) includes the deposition of the Savukoski Group and Kittilä suite (Köykkä et al., 2019).The Savukoski Group comprises phyllites and graphite-and sulfide-bearing black schists overlain by komatiitic and picritic metavolcanic rocks.The 6-9 km thick allochthonous Kittilä suite overlies rocks of the Savukoski Group.Kittilä suite comprises mostly tholeiitic basalts with subordinate felsic intrusions, banded iron formations and various metasedimentary packages.The final foreland basin stage includes deposition of coarsegrained sediments and syngenetic felsic metavolcanic rocks of the Kumpu group (Köykkä et al., 2019); deposition likely occurred after 1.88 Ga (Hanski and Huhma, 2005).The Paleoproterozoic supracrustal rocks were intruded by 2.44-2.05Ga mafic-ultramafic intrusive rocks and 1.88-1.76Ga syn-to post-orogenic granitoids (Nironen, 2005;Patison, 2007;Köykkä et al., 2019).
The CLB has been affected by three main stages of ductile deformation (D1-D3) and metamorphism during the 1.92-1.77Ga Svecofennian orogeny, followed by a final stage of brittle deformation (D4) (Väisänen, 2002;Lahtinen et al., 2005Lahtinen et al., , 2015;;Hölttä et al., 2007;Patison, 2007;Sayab et al., 2019).A recent and more detailed account of the deformational history of the CLB can be found in Sayab et al. (2019).The central part of the CLB that hosts most of the known Au deposits forms a synform and is dominated by tholeiitic basalts of the Kittilä suite, surrounded by rocks of the Savukoski, Kumpu, and Sodankylä groups (Fig. 1a).This area is characterized by greenschist facies metamorphic grade, and it is bound on all directions by mid-amphibolite facies rocks (Hölttä and Heilimo, 2017).The age of metamorphism in the CLB is not well constrained but it is generally accepted that peak metamorphic conditions took place between 1.88 and 1.86 Ga (Lahtinen et al., 2015;Hölttä and Heilimo, 2017).Two peaks in formation of orogenic Au mineralization have been identified in the CLB: (1) at ca. 1.92 Ga during early collision and ductile deformation (Lahtinen et al., 2012;Wyche et al., 2015;Molnár et al., 2017Molnár et al., , 2018) ) and (2) during D4 between 1.83 and 1.76 Ga (Patison, 2007;Molnár et al., 2017Molnár et al., , 2018)).However, the early 1.92 Ga age is constrained only by a Re-Os isochron age for arsenopyrite from the Suurikuusikko deposit (Wyche et al., 2015), whereas Molnár et al. (2018) also inferred an early (older than 1.88 Ga) mineralization stage at the Iso-Kuotko deposit, based on modelling done on disturbed Re-Os systems in sulfides.Based on U-Pb dating of hydrothermal monazite and xenotime associated with ore minerals, the majority of orogenic Au mineralization took place during the late-to post orogenic hydrothermal events (Molnár et al., 2017(Molnár et al., , 2018)).
Most orogenic Au occurrences in the CLB are spatially associated with the complex east-west trending Sirkka Shear Zone (SiSZ) and its subsidiary shear and fault zones (Eilu et al., 2007;Fig. 1a).SiSZ is characterized by anomalous Au concentrations along its entire length (Eilu et al., 2007).A second significant structure in the CLB is the NNEtrending Kiistala Shear Zone (KiSZ), which has been interpreted as a reactivated transfer fault or reoriented early thrust (Ward et al., 1989;Sayab et al., 2019) and hosts the Suurikuusikko and other Au-only deposits (Fig. 1a).KiSZ is consistently anomalous in Au for at least 15 km along strike (Eilu et al., 2007).

Geology and exploration history of the Hirvilavanmaa Au deposit
Hirvilavanmaa is situated in the southern part of the CLB (Fig. 1a-b), approximately 15 km northeast from the town of Kittilä; it is the closest discovered deposit to the intersection between the SiSZ and the KiSZ (approximately 0.5 km; Fig. 1a).The area around Hirvilavanmaa was first studied by the Geological Survey of Finland (GTK) in 1983 and during the same year mineralized zones including Hirvilavanmaa were discovered (Johansson et al., 1986;Keinänen et al., 1988;Keinänen and Hulkki, 1992;Keinänen, 1994).A resource estimate of 0.11 Mt of ore grading at 2.9 ppm Au has been calculated for Hirvilavanmaa (Scan Mining Oy, 2002).The currently known NNE-trending mineralized domain is 270 m long and 90 m wide with narrow lens-like mineralized bodies dipping at 85 degrees (dip azimuth = 270 • ; Fig. 2a).Recent drilling has indicated that the mineralized zone extends both vertically and horizontally beyond previously set limits, remaining open at depth and along strike to the north (Rupert Resources, 2020).
Hirvilavanmaa is hosted mainly by magnetite-rich ultramafic metavolcanic rocks of komatiitic affinity that strike NW in the area near the deposit; the ultramafic rocks belong to the Sattasvaara formation of the Savukoski group (Lehtonen et al., 1998).The komatiitic rocks have been intensely altered and deformed and appear as various schists, albitecarbonate-chlorite-sericite rocks and carbonate rocks; the latter include a fuchsite-bearing variety that have been termed "chromian marbles" and were marketed commercially as a natural stone material (Pekkala and Puustinen, 1978;Hulkki and Keinänen, 2007).Other formations in the Hirvilavanmaa area include sulfide-and graphite-bearing schists, quartzites and mafic metavolcanic rocks, with minor amounts of the latter being present in the host sequence of the mineralization (Hulkki and Keinänen, 2007).Hulkki and Keinänen (2007) recognized the following sequence of alteration: (1) regional talc-chlorite alteration (accompanied by lowdegree carbonatization), (2) albitization, (3) silicification and pyritization and (4) late carbonatization.The two former alteration stages were interpreted by the cited authors as the result of hydrothermal fluid circulation along the SiSZ predating Au mineralization, whereas the two latter ones were associated with brittle deformation (D4), quartz veining and Au mineralization related to the fluid flow along the KiSZ.Distal, intermediate and proximal alteration zones comprise talc-chloriteamphibole schist, albite-carbonate-talc-chlorite schist, and albite-carbonate-chlorite rocks, respectively.Au enrichment is located in "quartz breccias" and several generations of quartz-carbonate-albite veins (Hulkki and Keinänen, 2007).Late-stage quartz veins with a strike of N10W-N15W host much of the gold resources (Hulkki and Keinänen, 2007;Rupert Resources, 2020).Pyrite is the most dominant sulfide and occurs in and around the quartz veins and breccias.Accessory minerals include hematite, magnetite, chalcopyrite, rutile and pyrrhotite.Hematite is particularly common in the distal alteration zone.Native gold is present mostly as inclusions and fracture fillings in pyrite and locally in vein quartz and carbonate (Hulkki and Keinänen, 2007;Rupert Resources, 2020).According to Hulkki and Keinänen (2007) Au mineralization took place late in the structural history of the CLB, and it postdates regional peak metamorphism.

Geology and exploration history of the Naakenavaara deposit
The Naakenavaara deposit is situated just over 5 km SSW from Hirvilavanmaa (Fig. 1b) and is enriched in Cu, Co, and Ni in addition to Au (Nenonen, 1975;Taranis Resources, 2010, 2011).The area was first studied by the GTK between 1972 and 1974 when an airborne geophysical survey detected an electrical anomaly caused by graphiteand sulfide-bearing phyllite; 19 drill holes were completed and Naakenavaara was deemed as a potentially economic Cu deposit (Nenonen, 1975).Exploration by the GTK continued in the 1990s, when elevated Au concentrations were discovered by reanalysing the old drill cores (Keinänen, 2002).The most recent exploration activity took place in the 2010s (Taranis Resources, 2014).Drillholes from the 1990s and the 2010s intersected several Cu-rich intervals that were variably also enriched in Co, Ni, and Au (Keinänen, 2002;Taranis Resources, 2010, 2011).The precise shape and extent of the ore zones have not been defined but results of drilling indicate several lodes situated in the northern and southwestern parts of the geophysical anomaly that are ~2 km apart (Nenonen, 1975;Keinänen, 2002).According to Taranis Resources (2014), the ore zones potentially extend beyond their currently known limits.
The rock units of CLB at the Naakenavaara deposit have a subhorizontal to horizontal setting in a very low-angle antiform (Fig. 2b) that is bordered by a significant N-trending shear zone on the west (Nenonen, 1975;Keinänen, 2002).The uppermost unit at Naakenavaara consists of quartzites, with underlying layers of ultramafic and mafic metavolcanic rocks, phyllite, graphite phyllite, and sericite schists (Nenonen, 1975;Keinänen, 2002); the polymetallic deposit is hosted by the latter three rock types with sericite schists being especially sulfiderich (Keinänen, 2002).The most extensively drilled northern part of Naakenavaara hosts the most promising Cu concentrations (Keinänen, 2002); phyllites and sericite-schists dominate this area (Fig. 2b).Mafic metavolcanic rocks are more prominent in the southwestern part of the area (Fig. 2b).Rock units at Naakenavaara have been folded and intensely fractured.Sulfide-bearing quartz-carbonate-albite veins are hosted in intensely fractured zones (Nenonen, 1975).The most typical sulfide assemblage at Naakenavaara includes pyrrhotite, chalcopyrite, and pyrite (Nenonen, 1975;Keinänen, 2002).Best Cu intercepts exceed 1.7 wt%, (best intercept is 2.3 m-long and has 1.77 wt% Cu; Keinänen, 2002), whereas Au concentrations are generally low but locally 1 m-long intercepts reach up to 10 ppm.Enrichment of Ni (up to 0.5 wt%) is typically connected to the presence of gersdorffite (Nenonen, 1975), whereas so far there is no information on the minerals related to the up to 0.3 wt% enrichment of Co.

Sampling and study methods
For this study, three drill cores from Hirvilavanmaa (R325B, R335, R395) and three drill cores from Naakenavaara (R611, R617, R618; from GTK's drilling program in the 1990s) were logged and sampled at the GTK drill core facility at Loppi.The drill core logging and sample selection were supported by whole-rock geochemical data that were provided to the principal author by the GTK for the purposes of this work.Whole-rock analyses were done at the geochemical laboratory of Fig. 2. Cross sections from the Hirvilavanmaa and Naakenavaara deposits.(a) Cross section from the Hirvilavanmaa deposit depicting alteration zones and mineralized "quartz breccia" zone.Modified after Hulkki and Keinänen (2007).Drillhole R335 used in this study is also projected.Drillholes R325B and R395 are not part of the same drilling profile represented by this cross section and are thus not depicted in the figure.(b) Cross sections from the northern (up) and southwestern (down) parts of Naakenavaara.Modified after Nenonen (1975).Drillholes from this study are from the northern, and more extensively drilled, part of Naakenavaara.Drillhole R611 used in this study is projected to the northern cross section.Drillholes R617 and R618 are part of different drilling profiles and as such are not depicted in the figure .Other depicted drillholes are from the 1970s drilling program and are depicted only for the purpose of illustrating zones with high Cu concentrations.
the GTK between 1988 and1996.Elements considered in this study are: Ag, As, Au, Ca, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, P, Pb, S, Ti, V and Zn as they were available for all drillholes.At Naakenavaara, Au was analyzed with laboratory method 521U and all other elements with method 511P.Both involve digestion of the sample with aqua regia; analysis in the former method is done by graphite furnace atomic absorption spectrometry (GFAAS) and in the latter by inductively coupled plasma atomic emission spectrometry (ICP-AES).At Hirvilavanmaa, Au was analyzed with laboratory methods 522U, 704A or 519A and all other elements with methods 511P or 511A.Method 511A involves analysis by flame atomic absorption spectrometry (FAAS) after digestion with aqua regia.Method 522U is similar to method 521U.Method 704A involves analysis by FAAS after Pb-Fire Assay separation.Method 519A involves digestion by aqua regia and analysis by GFAAS.
Sulfide trace elements were analyzed from pyrite, pyrrhotite and chalcopyrite by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) by means of an Analyte 193 ArF laser ablation system (Photon Machines, San Diego, USA) connected to a single collector Nu AttoM SC-ICP-MS instrument (Nu Instruments Ltd., Wrexham, UK).The analytical work took place at the Finnish Geosciences Research Laboratories at the GTK in Espoo.In this study, 151 pyrite grains, 24 pyrrhotite grains, and 21 chalcopyrite grains from a total of 34 samples were analyzed.Sulfide grains were checked for internal zoning via SEM and, where applicable, analytical spots were placed in both cores and rims of the analyzed grains.For the trace element analyses, the laser was run at a pulse frequency of 10 Hz and a fluence of 2.5 J/cm 3 on the sample surface with a 50 μm spot size.Analyses were initiated with a 20 s baseline measurement, then the laser was automatically switched on for 40 s of signal acquisition.Analyses were conducted using timeresolved analysis (TRA) with continuous acquisition of data for each set of points.Mass-1 (Wilson et al., 2002) and UQAC (Savard et al., 2018) were used as external standards for quality control of the analyses.The measurements were performed on 37 elements (Si, S, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Te, Ba, W, Pt, Au, Hg, Tl, Pb, Bi, Th, U) at low resolution using the fast-scanning mode.Stoichiometric Fe was used as the internal standard.Data reduction was carried out using the software GLITTER (van Achterbergh et al., 2001), which allows baseline subtraction, integration of the signal within a selected time window, and quantification using known concentrations of the external and internal standards.
Principal component analysis (PCA) was performed on lithogeochemical and pyrite trace element data using the XLSTAT software package (Addinsoft, 2020).Chalcopyrite and pyrrhotite trace element data were not included in the PCA due to the low number of overall analyses and the higher number of analyses below detection limit compared to pyrite.Prior to the statistical analysis, a centred log-ratio transformation (clr-transformation; Aitchison, 1986) was performed in order to address the closure effect of geochemical data (Reimann et al., 2008).Variables chosen for PCA on Naakenavaara whole-rock data are Ca, Cr, Mg, V, Ni, Au, Co, S, Cu, Pb, As, and Mn; For Hirvilavanmaa whole-rock data As and Mn were omitted due to number of analyses <d.l. and lack of variation respectively.Variables chosen for PCA on pyrite trace element data from both deposits are Co, Ni, Cu, As, Se, Au, Pb, Bi, Te, Sb, S, and W.

Alteration, sulfide mineralogy and lithogeochemistry in the Hirvilavanmaa deposit
The Au ore at Hirvilavanmaa is mostly hosted by altered metakomatiites and subordinately by mafic metavolcanic rocks.The host rocks have undergone metamorphism and multi-stage alteration and are now represented by carbonate rocks, albitites, and various talc-chlorite-carbonate-albite schists (Fig. 3).
Talc, albite, and early carbonates are the oldest alteration minerals and mark the alteration stages that predate Au mineralization.Relative timing of these minerals established in our study agrees with observations from Hulkki and Keinänen (2007): early talc alteration is followed by albitization; early low-degree carbonate alteration probably started during the waning stages of talc alteration and continued to some extent during albitization.Talc typically forms fan-shaped clusters (Fig. 4f-g); host rock albitization is locally pervasive.Early carbonate minerals can be typically found as fine disseminated grains together with albite and quartz or as coarse porphyroclasts (Fig. 4f).Hulkki and Keinänen (2007) suggested that chlorite alteration at Hirvilavanmaa is part of the early regional pre-ore alteration.In contrast, during our mineralogical study we found that at least in rocks proximal to the ore zones, chlorite alteration is a later event associated with Au mineralization; this could indicate the presence of two chlorite generations.Chlorite can be found as tabular sheets and comprises large parts of the host rocks in ore zones (Au >0.4 ppm); it typically overprints most other minerals (Fig. 4a-e).The close relationship of chlorite with the deposition of pyrite is prominent in the ore zones, with chlorite-rich areas forming alteration haloes adjacent to quartz-carbonate veins and hosting abundant pyrite that locally contains visible Au inclusions (Fig. 4a-e); locally, chlorite is also intergrown with tourmaline, forming chlorite-tourmaline-pyrite sheets (Fig. 4a-c).Chlorite intergrown with tourmaline and pyrite also locally form intensely altered host rock slivers inside sulfide-bearing quartz veins (Fig. 3d, i).Ore zones are characterized by abundant pyrite-hosting quartz-carbonate veins (Fig. 3) and by late carbonatization of the host rocks that is more intense compared to barren zones (Fig. 4h).Quartz-carbonate veins appear as individual thick veins or as a stockwork network of thinner veinlets.Several generations of veins can be distinguished: (1) thin early albiterich veinlets (Fig. 4i), (2) quartz veins with typically red-to browncolored carbonate selvages (Fig. 3a, c, f, i), (3) late quartz veins with cream-colored carbonate porphyroclasts (Fig. 3d, e, g, j) that locally cut through older generations of veins.The two latter vein types host pyrite within them and especially in their chlorite-rich alteration haloes (Fig. 3) and cut mostly albitized zones.
At Hirvilavanmaa, no other metals in addition to Au are significantly concentrated apart from very occasional Cu and weak Co enrichments (up to 0.44 wt% and 342 ppm, respectively; Supplementary Table S1).Ore zones are also characterized by elevated S, Fe, Mo and Pb contents, with the latter reaching maximum concentrations of 81 ppm; Ti contents typically decrease in ore zones.Notable is the As-poor character of the deposit, with median and maximum concentrations of 10 and 54 ppm respectively.
The sulfide mineralogy of the Hirvilavanmaa deposit is overwhelmingly dominated by pyrite.It occurs as disseminated subhedral-to euhedral grains of various sizes (20 μm to 7 mm), locally forming grain aggregates (Fig. 3; Fig. 4).Pyrite occurs both in quartz-rich veins and in the chlorite-rich alteration haloes around them.Pyrite cores typically contain abundant gangue mineral inclusions (mostly albite, quartz and carbonate; Fig. 4n).In parts of the deposit characterized by talc and albite alteration, pyrite is typically associated with hematite and locally with rare magnetite (Fig. 4k-l).In these parts, hematite appears as either euhedral blades, typically intergrown with pyrite, or as anhedral inclusions in pyrite.Magnetite is mostly euhedral and appears as fine dissemination and locally as inclusions in hematite and pyrite.Locally, small amounts of chalcopyrite are present, as inclusions in pyrite or forming composite sulfide patches with it (Fig. 4r); apart from rare exceptions, the amount of chalcopyrite is rather negligible resulting in the overall low Cu concentrations in the deposit (Supplementary Table S1).Pyrrhotite is almost exclusively present as inclusions in pyrite; chalcopyrite, galena, and rutile are also local accessories forming inclusions in pyrite.Fine disseminated rutile is present throughout the deposit.Native Au is present as fracture fillings and inclusions of various size (3 to 40 μm) in pyrite (Fig. 4m-q).Native Au inclusions in pyrite are relatively common in Au-rich parts of the deposit; native Au inclusions were observed in 15 out of the 40 thin sections studied under the petrographic microscope.In some samples, native Au inclusions in pyrite associate with galena (Fig. 4q).

Alteration, sulfide mineralogy and lithogeochemistry in the Naakenavaara deposit
At Naakenavaara, the host sequence comprises altered metasedimentary rocks and subordinately ultramafic and mafic metavolcanic rocks; metasedimentary rocks are now represented by various mica schists, phyllites, and albitites (Fig. 5).In the three studied drillholes, metavolcanic rocks make up roughly 10 % of the total lithology.Albitization can be observed in several parts of the host rocks and their pervasively albitized parts can be described as albitites (Fig. 5g, i).Albitized quartzites, ranging from 5 to 35 m in apparent thickness in drillholes, form the uppermost lithological unit in all three studied drillholes.Mica schists are the most widespread host rock type and comprise abundant fine sericite flakes with or without associated quartz (Fig. 6 b, d, h); locally they also contain biotite, chlorite, carbonate minerals and albite.Phyllites comprise several different interchanging layers (Fig. 5a, c); sericite-rich parts are interchanged with darker parts that host fine graphitic material, together with fine sericite, quartz and/ or chlorite (Fig. 6 e-g).Based on our mineralogical study, albitization was the oldest alteration event and it predates ore deposition.Alteration related to ore deposition started with sericitization and was followed by biotite, chlorite, and late carbonate alteration.Whether the presence of fine graphitic material in phyllites is a product of ore-related alteration is difficult to establish.
Ultramafic metavolcanic rocks contain only minor amounts of sericite; they now comprise biotite-chlorite-talc-carbonate schists with variable amounts of albite.Ultramafic rocks can be geochemically recognized by significantly higher Cr contents, typically >1000 ppm and reaching up to 1900 ppm; Cr concentrations in metasedimentary rocks are <300 ppm, and typically stay significantly <100 ppm.Ultramafic metavolcanic rocks are typically barren as they do not host significant Cu, Co or Au concentrations.
The metasedimentary host rocks at Naakenavaara are cut by abundant sulfide-bearing, quartz-carbonate veins (Fig. 5) that locally also contain various amounts of biotite, chlorite and albite (Fig. 6a, c, e, i); biotite forms disseminated flakes and it is also abundant in the selvages of veins (Fig. 6a, d).Locally, late generations of veins are dominated by carbonates with only minor amounts of quartz.
The Naakenavaara deposit is principally enriched in Cu, Co, and Ni in addition to Au (Supplementary Table S1).The main type of ore is characterized by Cu (± Au) enrichment, with Cu being by far the most evenly enriched metal in the deposit.Zones characterized by elevated Co (± Au) are less widespread and mark the second type of ore.Even though the two ore types are typically spatially distinct, they locally overlap.Median and maximum concentrations of Cu in the studied drillholes are 371 ppm and 2.3 wt% respectively; significant Cu enrichment (>1000 ppm) is widespread in ore zones and spans continuously between 2 and 50 m in apparent thickness in drillholes.Zones of notable Co enrichment (>300 ppm) occur more sparsely compared to Cu-rich zones, and span continuously up to 10 m in apparent thickness.Median and maximum Co concentrations are 55 ppm and 0.1 wt% respectively; in some drillholes not included in this study Co concentrations reach up to 0.27 wt%.Gold is enriched in small patches mainly within the Cu ore and occasionally within the Co ore zones.Concentrations of Au are generally low (median of 0.02 ppm); zones with notable Au enrichment (> 0.1 ppm) span continuously up to 5 m in apparent thickness.Maximum Au concentration is 10.3 ppm in the studied drill holes.Enrichment of Ni (up to 0.1 wt%) is locally present within the Cu and Co ore zones.Elevated Ni contents (up to 500 ppm) are also associated with the barren ultramafic metavolcanic rocks.Manganese is slightly enriched (>0.2 wt%) in several parts of the deposit compared to typical Mn concentrations in sedimentary and igneous rocks.In one studied drill core (R618), there is a 21 m long Mn-rich interval averaging 1.5 wt% and reaching up to 3.6 wt%.
The most abundant sulfide minerals at Naakenavaara are chalcopyrite, pyrrhotite and pyrite.They occur principally within the quartz-carbonate veins but are also present as fine dissemination in the wall rocks surrounding them.Locally, sulfide minerals form a massive texture; these parts are dominated by pyrrhotite and subordinately chalcopyrite.Chalcopyrite dominates the Cu-rich parts of the ore and is the only recognizable Cu mineral; it occurs as dissemination or elongated patches within the quartz-carbonate veins (Fig. 6j-k).In some of the Cu-rich parts of veins, pyrrhotite is intergrown with chalcopyrite forming composite sulfide grains (Fig. 6j-k).Pyrrhotite can be also locally found as inclusions in chalcopyrite.Disseminated to patchy (and locally massive) pyrrhotite is also widespread in some of the Co-rich zones that are typically also characterized by Ni enrichment.Pentlandite flame-like exsolutions are visible in pyrrhotite from the Ni-rich parts of the ore zones (Fig. 6o).Rare gersdorffite can be found as inclusions in pyrrhotite in some of the Ni-rich parts of the deposit.
Pyrite is present throughout the ore zones.In Cu-rich parts, pyrite is typically anhedral, and forms patches together with chalcopyrite and pyrrhotite or occurs as inclusions in the latter (Fig. 6m-n); this type of pyrite is relatively inclusion-free and locally has cracks filled by chalcopyrite.In Co-rich parts, pyrite typically occurs as euhedral to subhedral dissemination of variable size (20 μm -2 mm) and as grain aggregates (Fig. 6p-q) and is the dominant sulfide; this pyrite type typically contains abundant inclusions of silicates, pyrrhotite, and chalcopyrite.Cobaltite is the only Co mineral recognized and occurs in Co-rich parts as euhedral inclusions of variable size (up to 100 μm) in pyrrhotite (Fig. 6r).Host rocks typically contain very fine disseminated rutile and magnetite.Native Au is only scarcely observed as very fine (< 10 μm) inclusions in pyrite and chalcopyrite and embedded in silicate minerals in late carbonate veins (Fig. 6l).

Results of sulfide trace element LA-ICP-MS analyses
Results of trace element analyses are graphically depicted in Figs.7-9 and presented in greater detail in Supplementary Tables S2-S5.Pyrite from the polymetallic ore at Naakenavaara has higher concentrations of Co, As, Se, and Bi compared to pyrite from the Au-only ore at Hirvilavanmaa (Fig. 7a).Pyrite from Naakenavaara is also characterized by higher Co/Ni and Se/S ratios (mean values of 168 and 6.3 × 10 − 6 respectively) compared to pyrite from Hirvilavanmaa (mean values of 1.9 and 1.9 × 10 − 6 respectively).Pyrite from Hirvilavanmaa in turn, is  more enriched in Ni, Cu, Ag, Au, and Pb; pyrite from both deposits has similar concentrations of Mo, W, Mn, and Sb (Fig. 7a).
Chalcopyrite in both deposits hosts measurable concentrations for most analyzed trace elements(Fig.7b; Supplementary Table S4).Chalcopyrite from Hirvilavanmaa is generally trace element-poor, with only Se having mean values in the tens of ppm (30 ppm).Chalcopyrite from Naakenavaara, on the other hand, is significantly enriched in Ni, Zn, Ag, and In with maximum measured concentrations reaching 819 ppm, 760 ppm, 253 ppm, and 151 ppm respectively (Fig. 7b).Co, Sn, and Se are other trace elements that have maximum values at least in the tens of ppm in chalcopyrite from Naakenavaara (Fig. 7b).
Pyrrhotite from Naakenavaara hosts several trace elements in measurable concentrations, with Co and Ni being especially enriched, with maximum concentrations of 0.97 wt% and 0.48 wt% respectively and median values of 617 ppm and 0.32 wt% respectively (Fig. 7c; Supplementary Table S5).In general, pyrrhotite from Naakenavaara is more enriched in Ni and less enriched in Co compared to pyrite (Fig. 7).
A closer look on the trace element concentrations in pyrite from Hirvilavanmaa is presented graphically in Fig. 8.In a Au-As scatterplot (Fig. 8c) part of the pyrite data plot above the Au solubility lines for pyrite in gold deposits (Reich et al., 2005;Deditius et al., 2014).The Co-Ni diagram (Fig. 8a) shows a rather continuous distribution for most of the data.Pyrite can be divided into low, intermediate, and high Co/Ni ratio types (Fig. 8a).The low Co/Ni ratio pyrite (Py Hirvi -1; Hirvi stands for Hirvilavanmaa) has Co/Ni ratios up to 0.3, the intermediate (Py Hirvi -2) up to 2.7 and the high (Py Hirvi -3) up to 16 (median values of 0.05, 0.55 and 5.56 respectively).Py Hirvi -1 includes mainly cores of pyrite, whereas most rims are part of Py Hirvi -2, and especially Py Hirvi -3 (Fig. 8b).Concentrations of other elements show systematic variation in the three pyrite types (Fig. 8d).Both Co and Ni concentrations differ significantly in the three pyrite types.In addition, As and Se concentrations and Se/S ratios progressively grow relative to the Co/Ni ratios in each pyrite type; Ag, Sb, Te, W, Au, Pb, and Bi concentrations mostly follow an opposite trend with Py Hirvi -1 having the highest concentrations that progressively decrease in the other two pyrite types.
Selected scatterplots and statistical representation of trace element concentrations in pyrite from Naakenavaara are presented in Fig. 9.In the Au-As scatterplot, data points form two distinct areas that are characterized by distinct As concentrations; most pyrite data points plot below the Au solubility lines (Reich et al., 2005;Deditius et al., 2014) (Fig. 9c).Three pyrite types are distinguished based on their Co/Ni ratios and other trace element characteristics (Fig. 9a).The low, intermediate, and high Co/Ni ratio pyrite types have mean Co/Ni values of 0.3, 12.5, and 762 respectively.The low Co/Ni pyrite type (Py Naak -low; Naak stands for Naakenavaara) mostly includes pyrite from zones of Cu-Au and Co-Au enrichment.The intermediate Co/Ni type (Py Naakmid) is dominated by pyrite from zones of Co (± Cu) enrichment.The high Co/Ni type (Py Naak -high) is dominated by pyrite from zones of Cu-Au and Co-Cu enrichment.Within all three pyrite types, data for cores and rims are distributed rather evenly (Fig. 9b).The three pyrite types also show systematic variation in concentrations of other elements (Fig. 9d).The Co/Ni ratios are controlled by both Co and Ni concentrations, but variations in the latter are especially significant.Py Naak -low is distinctly different from the other two types, having significantly lower As and Co and moderately lower Te, and Au concentrations, and significantly higher Ni, W, Mo, Ag, and Pb concentrations.Differences in As and W concentrations reach several orders of magnitude; Sb, V, and Mn are also enriched relative to the other pyrite types (Fig. 9d).Py Naakmid and Py Naak -high have differences in the concentration of several trace elements when compared to each other, albeit to a more moderate degree.

Principal component analysis on whole-rock geochemical data
Principal component analysis (PCA) was performed on Naakenavaara whole-rock geochemical data (Table 1).First principal component (PC1) is characterized by Mg-V-Cr-Mn (positive scores) and by As-S-Co and Cu-Au (negative scores).PC2 is dominated by the positive score of Cu whereas Ca-Mn and Co(-As) have negative scores.PC3 is characterized by Ca-Mn and Au (positive scores) and by Ni-Co-S (negative scores).PC4 is characterized by positive scores of S and Mg-Ca; Au-As-Pb have negative scores.In the PC1-PC2 biplot (Fig. 10a), V-Cr and Mg-Mn-Ca characterize the right part of the diagram.Lower and upper left parts of the diagram are characterized by Co-As-S and Cu respectively; vector of Cu is close to perpendicular to Co.The short vector of Au warrants a cautious interpretation; it is inferred, however, that Au is not closely related to either Cu or Co. Barren ultramafic metavolcanic rocks form a distinct cluster, close to vectors of Cr and V. Unmineralized metasedimentary rocks are scattered in the middle part of the diagram.Samples with Co and Cu enrichment cluster in distinct areas influenced by As-Co and Cu vectors respectively.Samples with polymetallic enrichment are scattered between the two end members.
PCA was also performed on whole-rock geochemical data from Hirvilavanmaa (Table 1).PC1 is characterized by Au-S and Ca-Cr-Mg-Ni-V with positive and negative scores respectively.PC2 is characterized by positive scores of Cu and negative scores of Co and Ni.PC3 is characterized by positive scores of Au and Pb.In the PC1-PC2 biplot (Fig. 10b) Au is closely related to S, on the right part of the diagram; left part of the diagram is characterized by Ca-Cr-V and Mg-Ni-Co and upper part by Cu.There is a gradual transition from barren to Au-rich samples with the latter plotting on the right part of the diagram influenced by vectors of Au and S.

Principal component analysis on pyrite trace element data
Results of principal component analysis (PCA) on pyrite trace element data from Naakenavaara can be found in Table 1.Associations of As-Co and Se-S have positive scores in the first principal component (PC1), whereas W-Pb and Sb have negative scores.PC2 is characterized by Co-Ni-Se-S-W and Pb-Bi-Sb(-Au-Te) with positive and negative scores respectively.PC3 is characterized by Co-Cu-Se-Te-S and Ni-Bi with positive and negative scores respectively.In the PC1-PC2 biplot (Fig. 10c) W is distinct from vectors of other elements and is close to perpendicular to Pb-Sb-Bi and S-Se-Co, indicating an independent behaviour relative to them.Tungsten is weakly related to Ni and has an antithetic relationship with As and Au-Te.The PC1-PC2 biplot separates  Results of PCA on pyrite trace element data from Hirvilavanmaa are depicted in Table 1.PC1 is characterized by Co-Ni-As-Se-S and Au-Pb-Bi-Te-Sb with positive and negative scores respectively.PC2 is characterized by W and Sb (positive scores) and by Te (negative score).PC3 is characterized by Co-As-Bi (positive score) and Cu-Ni (negative score).In the PC1-PC2 biplot (Fig. 10d) W is independent of other elements.The left side of the biplot is dominated by Au-Bi-Pb-Te(-Cu) that have an antithetic relationship with Co-As-Se-S-Ni that plot on the right side.Pyrite from all pyrite types is scattered rather evenly across the biplot, except for part of Py Hirvi -1 that mostly plots on the left side of the diagram.

Comparison of mineralogical characteristics
Lithological units in both deposits have been metamorphosed in greenschist facies conditions and have been subjected to multi-stage alteration.A common characteristic in the two deposits is albitization of host rocks that predates ore deposition as is typical for deposits hosted along the SiSZ (Eilu et al., 2007).At Hirvilavanmaa Au is hosted in veins that cut increasingly albitized and hence competent rocks.At Naakenavaara albitization is most prevalent in barren rocks, such as the uppermost quartzites.Minor albitization has also locally survived overprint by ore-related alteration and veining in the ore zones.Another common feature is the presence of late carbonate and chlorite alteration and association of metal enrichment with quartz-carbonate veins.Apart from these similarities, the two deposits show several differences.In addition to contrasting host rock types, differences also extend to alteration-and sulfide mineralogy.The sequence of alteration is relatively easy to establish at Hirvilavanmaa.Distal alteration zones are characterized by early pre-ore talc-carbonate and albite alteration.Orerelated alteration includes additional late carbonatization and chloritetourmaline alteration (Fig. 3).Characteristic is the absence of sericite and biotite alteration.At Naakenavaara, on the other hand, sericite is the most prominent alteration mineral in the ore zones, with most sulfidized rocks being sericite-dominated schists; biotite alteration is also present in ore zones, mainly in Cu-rich parts of the deposit.
Pyrite is by far the most dominant sulfide and the main host of Au at Hirvilavanmaa, with Au being typically present as inclusions and fracture fillings in pyrite (Fig. 4m-q).Additionally, there is abundant hematite intergrown with pyrite, fine magnetite, and rutile in more distal parts of ore zones, indicating variable redox conditions or temperature changes in the system (e.g., Evans, 2010).At Naakenavaara, sulfide mineralogy is dominated by chalcopyrite and pyrrhotite in the prevalent Cu ore, indicating more reduced conditions compared to Hirvilavanmaa.Parts of the Co-rich areas are, however, dominated by pyrite, indicating a possible change in oxidation conditions or changes in temperature as the mineralization evolved (e.g., Evans, 2010).

Pyrite geochemistry
It has been well-documented that pyrite acts as a sink for a plethora of trace elements (e.g., Huston et al., 1995;Barker et al., 2009;Large et al., 2009).Cobalt and Ni can be involved in isovalent substitutions  with Fe 2+ in pyrite, and Se and As can serve as anions and be involved in partial replacement of S in the crystal lattice of pyrite (e.g., George et al., 2018); these four elements are generally not released from the pyrite lattice even during later recrystallization events (Large et al., 2009).The Co/Ni ratio in pyrite together with concentrations of Co, Ni, As, Se and other trace elements have been used to distinguish different pyrite generations and mineralizing stages in ore deposits (e.g., Belousov et al., 2016;Vasilopoulos et al., 2021;Raič et al., 2022), to discriminate between different ore deposit types (e.g., Belousov et al., 2016;Gregory et al., 2019) and to infer key ore-forming processes (e.g., Reich et al., 2013;Keith et al., 2018).Analyzed pyrite from Hirvilavanmaa and Naakenavaara have notable differences in several trace elements concentrations indicating that fluids with different characteristics were involved in formation of the two deposits (Fig. 7a).A significant number of pyrites from Hirvilavanmaa plot above the solubility line for orogenic gold deposits (Deditius et al., 2014) in the Au-As scatterplot (Fig. 8c).This means that higher Au concentrations in analyzed pyrite represent evenly distributed Au nanoparticles rather than Au in solid solution, as was also shown to be the case in the Suurikuusikko deposit based on high resolution nano-scale 3D mapping of refractory gold in arsenopyrite and pyrite (Sayab et al., 2016).Thus, the nano-scale free character of some of the Au in pyrite at Hirvilavanmaa is supported by the results of LA-ICP-MS analyses and is in line with abundance of larger, micrometer-scale Au inclusions in pyrite (Fig. 4).Pyrite from all three types at Hirvilavanmaa have relatively low Co/Ni ratios, with Py Hirvi -1 and Py Hirvi -2 having median Co/Ni <1 and Py Hirvi -3 having a median Co/Ni ratio of 5.5 (Fig. 8d).These ratios fit with an orogenic Au deposit model, as pyrite from orogenic Au deposits have typically Co/Ni <10, with most having Co/Ni <1 (Belousov et al., 2016).Multistage evolution is common for orogenic Au deposits, and this is usually reflected in the presence of multiple pyrite generations (e. g., Large et al., 2009Large et al., , 2011)).In addition to locally forming grains with both cores and rims belonging to the same type, all three pyrite types make up grains with cores and rims belonging to different types.Py Hirvi -1 includes mostly cores of pyrite that have rims belonging to Py Hirvi -2 or Py Hirvi -3; thus, Py Hirvi -1 represents the earliest stage of mineralization.Py Hirvi -1 is generally more enriched in Ni, Cu, Ag, Sb, Te, Au, Pb and Bi (Fig. 8d), indicating that the mineralizing fluid was more enriched in these elements in early stages of ore deposition; indeed, Pb and Cu levels in early stages of mineralization resulted in Py Hirvi -1 being the main host of galena and chalcopyrite inclusions.Py Hirvi -2 forms rims in grains with Py Hirvi -1 cores and additionally forms cores in grains with Py Hirvi -3 rims, indicating that it represents a second stage of pyrite deposition.Py Hirvi -3 forms rims in pyrite grains that have cores belonging either to Py Hirvi -1 or Py Hirvi -2, thus representing the latest ore deposition stage at Hirvilavanmaa.Py Hirvi -2 and Py Hirvi -3 are progressively more enriched in Co and more depleted in Ni compared to Py Hirvi -1, with differences in concentration of these two elements being the most significant; differences in remaining trace elements are small or moderate and typically follow a progressive decrease or increase from Py Hirvi -1 towards Py Hirvi -3 (Fig. 8d) highlighting the relatively homogeneous (except for Co and Ni) nature of the pyrite-depositing fluid in all mineralizing stages.This is further supported by the pyrite trace element data plotting rather evenly in a PC1-PC2 biplot (Fig. 10d).Results of PCA on the pyrite trace element data from Hirvilavanmaa also distinguish elements usually incorporated in the pyrite crystal lattice (Co-As-Se-S-Ni) from those that can be present as micro-to nano-size mineral inclusions (Pb-Bi-Au-Te).
Pyrite from Naakenavaara plot almost entirely below the solubility lines (Reich et al., 2005;Deditius et al., 2014) in a Au-As scatterplot (Fig. 9c), indicating that Au is in solid solution in the lattice of pyrite.The Co/Ni ratios of the three pyrite types at Naakenavaara vary greatly (Fig. 9d).Py Naak -low has mean Co/Ni of 0.3 with a maximum value of 0.8, fitting with the expected low Co/Ni ratios of pyrite from orogenic Au deposits (Belousov et al., 2016).Py Naak -low is clearly distinct from the other pyrite types as it is significantly more enriched in Ni and W and significantly more depleted in As, with differences reaching up to several orders of magnitude (Fig. 9d); Py Naak -low is also more enriched in Pb, Mo, and Ag (Fig. 9d).Cobalt concentrations are smaller in Py Naak -low compared to the other pyrite types but still remain rather high (median of 842 ppm).High W concentrations are generally present in pyrite from orogenic Au deposits (Belousov et al., 2016) where the origin of W is usually connected to a granitic source (e.g., Groves et al., 2003), but can also be derived from the breakup of ilmenite in sedimentary rocks (Cave et al., 2015).Py Naak -mid has Co/Ni ratios with mean and maximum Co/ Ni ratios of 12.5 and 77 respectively, exceeding typical values from orogenic Au deposits (Belousov et al., 2016).Py Naak -high has particularly high Co/Ni ratios with median and maximum values of 293 and 3890 respectively; such exceptionally high Co/Ni ratios deviate greatly from those typical for orogenic Au deposits (Belousov et al., 2016).Py Naak -mid and Py Naak -high have generally similar concentrations in most trace elements, except for Co, Ni, and As, with Py Naak -high being significantly more enriched in Co and depleted in Ni; differences in As concentrations are moderate (Fig. 9d).
In addition to differences in trace element characteristics, the three pyrite types at Naakenavaara have differences in texture and characterize ore zones with differences in mineralogy and metal enrichment.Py Naak -mid is hosted by quartz-dominant veins in Co-only ore zones and locally in places where Cu and Co ores overlap; in both cases, sericitization is the dominant alteration, whereas in the Co-only ore zones albite is also present.Pyrite is typically the only sulfide in these Co-rich parts, except for minor pyrrhotite and chalcopyrite filling cracks in pyrite; locally, pyrrhotite and fine cobaltite are also abundant, and chalcopyrite is plentiful in samples where Co and Cu ore zones overlap.Py Naak -mid typically forms anhedral to subhedral disseminated grains or grain aggregates and contains abundant silicate inclusions, especially in the cores (Fig. 6p-q).Py Naak -high is hosted by quartz-carbonate veins in the Cu-ore and locally in the overlapping Cu-Co ore zones.These parts are characterized by abundant biotite and local chlorite alteration that overprint sericitization; biotite can also be found inside the veins or forming rims on them (Fig. 6a).Albitization has been almost completely overprinted in these parts of the deposit by the subsequent alteration events.Py Naak -high is typically subhedral to euhedral, relatively inclusion-free, and is closely associated with pyrrhotite and chalcopyrite; latter sulfides dominate these Cu-rich ore zones with pyrite being present as inclusions in them or in mixed sulfide patches.Based on these observations, we suggest that Py Naak -mid marks the earliest Co-rich mineralization event at Naakenavaara that evolved into the main Cu-  Py Naak -low include the highest Au grades in the deposit.Py Naak -low is typically anhedral, and forms mixed sulfide patches with pyrrhotite (Fig. 6n); the latter is the dominant sulfide with chalcopyrite only locally present in these late carbonate veins.In these parts that host Py Naak -low, alteration mineralogy is similar to other parts of the ore zones with the main difference being the presence of the late carbonate veins; carbonatization locally extends to the host rocks as well.Visible micrometer scale Au is rare at Naakenavaara but can be identified attached to a few Py Naak -low pyrite grains.Based on the above we conclude that Py Naaklow marks a late overprinting mineralizing event that was relatively limited in its extent but deposited most of the Au at Naakenavaara.The distinct trace element characteristics of Py Naak -low indicate that a fluid with different characteristics was responsible for this late overprinting stage.The late Au-rich stage is easily distinguished in the PC1-PC2 biplot based on the pyrite trace element data (Fig. 10c): Py Naak -low is distinct and plots close to the W vector, whereas the other pyrite populations plot close to As and the remaining variables.This further supports deposition of Py Naak -low from a fluid with different characteristics compared to pyrite related to the earlier base metal-rich mineralization.
Several studies have suggested that Se concentrations in pyrite are systematically controlled by changes in fluid temperature (Huston et al., 1995;Maslennikov et al., 2009;Keith et al., 2018), whereas fO 2 and fluid pH are not primary factors controlling Se in pyrite (Maslennikov et al., 2009;Keith et al., 2018).According to Keith et al. (2018) average temperature of ore deposition displays a negative correlation with the average Se in pyrite.Based on the average Se concentration in Py Hirvi -1, Py Hirvi -2, and Py Hirvi -3 from Hirvilavanmaa (4.5, 14.8 and 10.3 ppm respectively), we can infer that temperature of pyrite deposition was highest in early stages of ore-related hydrothermal activity and then stayed relatively high in later stages.Based on the average Se concentration in Py Naak -low, Py Naak -mid, and Py Naak -high from the polymetallic Naakenavaara deposit (26.9, 37.9 and 33.4 ppm respectively) inferred temperatures of ore deposition were considerably lower compared to Hirvilavanmaa.

Trace element geochemistry of chalcopyrite and pyrrhotite
Chalcopyrite is generally considered to be poorly enriched in trace elements compared to other common sulfides (Cook et al., 2009(Cook et al., , 2011;;George et al., 2018), yet it can host numerous trace elements in measurable concentrations that can reach significant levels in some cases (George et al., 2018).Chalcopyrite that crystallizes together with pyrite tends to have lower trace element concentrations as most of the substituting elements in the crystal lattice of chalcopyrite preferentially incorporate into the co-existing pyrite (George et al., 2018); this is reflected well in the trace element-poor character of chalcopyrite from the pyrite-dominated Hirvilavanmaa deposit (Fig. 7b; Supplementary Table S4).On the other hand, chalcopyrite dominates the Cu-ore at Naakenavaara, with pyrite being much less abundant; chalcopyrite from Naakenavaara is significantly more enriched in trace elements, with maximum concentrations of Zn, Ni, Ag and In being in the range of the hundreds of ppm (Fig. 7b; Supplementary Table S4).Indium is highly valued and although it is mostly extracted as a by-product from zinc ores, extraction from chalcopyrite is possible (Andersen et al., 2016), suggesting it could potentially be a by-product of the chalcopyritedominant ore at Naakenavaara.In general, Cd/Zn ratios in chalcopyrite increase with inferred temperature of crystallization (George et al., 2018).Chalcopyrite from Hirvilavanmaa has notably higher Cd/Zn ratios (mean 0.69) compared to chalcopyrite from Naakenavaara (mean 0.01) further supporting significantly different crystallization temperatures between them.
Several trace elements (e.g., Co, Zn, As, Se, Cd, Sb, Hg, Pb, Bi) can report to copper concentrates during froth flotation (Mular et al., 2002) and can require costly treatments to remove them from final Cu products.Ordinarily, concentrations of these penalty elements in a chalcopyrite-dominant ore are so low as to create no problems in the final Cu concentrate; Se and Hg, however, may create issues (George et al., 2018).Concentrations of Se and Hg in chalcopyrite from Naakenavaara are far below tolerable limits for Cu concentrates (500 and 10 ppm respectively; George et al., 2018), thus no issues with penalty elements in a potential Naakenavaara Cu concentrate are indicated.
Pyrrhotite can host several trace elements that can be either latticebound or part of nano-size mineral inclusions.Pyrrhotite from Naakenavaara hosts several trace elements in measurable concentrations but is particularly enriched in Co and Ni (Fig. 7c; Supplementary Table S5), which can be hosted in the crystal lattice of pyrrhotite (e.g., Kresse et al., 2018).Median Co and Ni concentrations are 617 and 3220 ppm respectively, with maximum values reaching 9741 ppm and 4753 ppm respectively.The maximum Co concentration coincides with an abnormally high As concentration of 2.1 wt% in one analysis, and since pyrrhotite cannot hold As in its structure (Large et al., 2011), this analysis probably reflects the presence of a cobaltite inclusion.Nevertheless, even discarding this spot, maximum Co concentrations remain high (2047 ppm).These significant Co and Ni concentrations indicate that pyrrhotite is a notable host of Co and Ni at Naakenavaara.Pyrrhotite associated with Py Naak -low in late-stage carbonate-dominated veins is significantly more enriched in Co and less enriched in Ni compared to pyrrhotite from Cu-rich parts of ore zones hosting Py Naak -high (Supplementary Table S5), indicating that they belong to different generations.

Insights from lithogeochemistry
At Hirvilavanmaa, Au is the only metal enriched in economically significant amounts as is typical in orogenic Au deposits (e.g., Groves et al., 2020).Other elements typically enriched in orogenic Au deposits, such as Ag, S, and Mo have also elevated concentrations at Hirvilavanmaa; the average Au/Ag ratio is 5.4, falling within range for orogenic Au deposits (Goldfarb et al., 2005).Results of PCA on whole-rock geochemical data are rather straightforward for Hirvilavanmaa (Table 1) due to the pyrite-dominated, Au-only style of mineralization and lack of host rock variability.As a result, PC1 represents a high degree (68.12 %) of the variability in the dataset; PC1 describes the (altered) ultramafic metavolcanic host rocks (Ca-Cr-Mg-Ni-V), and the ore zones (Au-S).PC2 and PC3 show that Cu enrichment is unrelated to Au and that locally elevated Co concentrations probably reflect natural Co variations in the host rocks (Co-Ni-Mg association).On the PC1-PC2 biplot Au-enriched samples form a distinct population (Fig. 10b).
At Naakenavaara, there are differences in enrichment of other elements between the Cu-and Co-ore zones: Cu-ore is more enriched in Au, whereas Co-ore is more enriched in As, Ni, Fe, Mo, and S; zones where Cu-and Co-ore overlap are generally more enriched in As, Ni, and Au compared to either individual ore type.PCA on the Naakenavaara whole-rock geochemical data (Table 1) reveals complex element associations that result in PC1 representing just 39.85 % of the variability in the dataset; PC1 distinguishes barren (Mg-Mn-V-Cr) and mineralized rocks (As-Co-S and Au-Cu).PC2 describes the prevailing Cu-ore; Cu is also antithetically related to Co. PC3 highlights that Ni and S are more enriched in the Co-ore.PC4 reflects the presence of sulfide-bearing quartz-carbonate veins (Mg-Ca-S).In the PC1-PC2 biplot (Fig. 10a) barren ultramafic metavolcanic rocks can be distinguished from metasedimentary rocks.Samples from the Co-ore are distinct from samples belonging to the Cu-ore, with overlapping zones plotting in areas between the Co and Cu end-members.This distribution together with the placement of vectors for Cu and Co and previously discussed observations regarding element enrichment and alteration mineralogy in the Cu and Co ores, reflect the early and prevailing base metal-rich mineralization that started with Co deposition and developed into the main Curich stage.With Au enrichment being relatively weak compared to Cu and Co, the late Au-rich mineralizing stage is not clearly distinct in the results of PCA on the whole-rock dataset.

Implications for ore deposit models
The strong structural control (Hulkki and Keinänen, 2007), combined with lithogeochemical, mineralogical and pyrite trace element characteristics discussed above all strongly support an orogenic Au deposit model for Hirvilavanmaa.The progressive and mostly moderate changes in trace element composition from oldest to youngest pyrite generation indicate the multi-stage evolution of a rather homogeneous system with no inputs from additional fluid sources.These conclusions are also supported by the rather straightforward results of PCA.Compared to many orogenic Au deposits, Hirvilavanmaa is rather Aspoor with some analyses falling below the detection limit of the applied analytical method, and a maximum concentration of just 54 ppm.In addition, ore-related pyrite at Hirvilavanmaa is relatively depleted in As and considerably more enriched in Co and Ni (Fig. 8d; Supplementary Table S2) compared to their typical concentrations in orogenic gold deposits (medians just over 100 ppm; Gregory et al., 2019).Arsenic is significantly enriched in diagenetic pyrite (Large et al., 2012;Pitcairn et al., 2006) and one of the prevailing models for formation of orogenic Au deposits invokes hydrothermal fluids derived from metamorphic devolatilization of pyritic metasediments (Pitcairn et al., 2006;Large et al., 2012;Phillips and Powell, 2010).If this was the case for Hirvilavanmaa, As concentrations should be significantly higher in ore-related pyrite and in the deposit as a whole.Goldfarb and Groves (2015) suggested that some Paleoproterozoic orogenic Au deposits are likely to have metavolcanic-rock source regions and Pitcairn et al. (2015) showed that basalts are a viable source of Au for orogenic gold deposits and that As is not necessarily liberated from them during metamorphism.Importantly, Niiranen et al. (2015) and Patten et al. (2020) demonstrated that large masses of Au were mobilized from metavolcanic rocks of the Kittilä suite in the CLB during prograde metamorphism leading to formation of orogenic Au mineralization.Finally, high Ni concentrations in pyrite from orogenic gold deposits can indicate mafic to ultramafic rock sources (Zhao et al., 2011).Based on the above listed observations and considering the spatial connection of Hirvilavanmaa to rocks of the Kittilä suite via the N-S trending KiSZ (Fig. 1a), it is more likely that Au was sourced from mafic metavolcanic rocks of the Kittilä suite instead of metasedimentary rocks of the Savukoski group or Kittilä suite.
The spatial association with major shear zones, the occurrence of mineralization within a ductile structure (anticline) and the metamorphic history of the CLB, make it tempting to accept an orogenic Au model for Naakenavaara in line with most gold-bearing deposits in the CLB and explain the base metal enrichment with the atypical subtype of the classification (e.g, Goldfarb et al., 2001).However, evidence from sulfide geochemistry further backed by mineralogical and lithogeochemical observations suggest that the Naakenavaara deposit has formed by multi-stage hydrothermal processes that need to be discussed in more detail.The Au-grade at Naakenavaara can reach up to 10.3 ppm (Supplementary Table S1); high Au concentrations (>1 ppm) are nevertheless the exception.With a median Au concentration of just 0.02 ppm and with Au-enriched intervals being scarce and typically having Au <0.5 ppm, Naakenavaara can be characterized as relatively Au-poor.On the other hand, base metal enrichment is much more pronounced in the deposit.Results from this study reveal the presence of two different mineralizing events with distinct fluid characteristics.Most of the metal enrichment at Naakenavaara can be attributed to the first and main mineralizing event that deposited Cu, Co and Ni.Mineralization started with a Co-rich stage that deposited pyrite (Py Naak -mid) and locally pyrrhotite and cobaltite; in pyrrhotite-rich parts Ni is also enriched.Mineralization evolved progressively into the main Cu-rich stage of ore deposition with precipitation of abundant chalcopyrite, pyrrhotite and pyrite (Py Naak -high).The second, and much more restricted mineralizing event locally overprinted earlier ore zones by depositing Au in late carbonate-dominant veins together with pyrite (Py Naak -low), pyrrhotite and less amounts of chalcopyrite.Based on the trace element characteristics of Py Naak -low, we propose that this mineralizing event can be attributed to a late orogenic Au event.The genetic type of the main Cu-Co-Ni mineralization remains open for now, and more research is needed before it can be confidently classified.
The Juomasuo (Vasilopoulos et al., 2021) and Rajapalot (Ranta et al., 2021;Raič et al., 2022) Au-Co deposits from the Kuusamo and Peräpohja belts, respectively, share similar temporal evolution of ore deposition as in Naakenavaara with evidence pointing to an early base metal-rich mineralization and a later orogenic Au overprint.Groves et al. (2003) proposed that many deposits classified as orogenic Au with an atypical metal association could represent the overprint of earlier base metal mineralization by late orogenic Au.Observations from Naakenavaara, as well as from Juomasuo and Rajapalot, seem to conform to this model.

Summary and conclusions
This contribution highlights the importance of sulfide trace element geochemistry in deciphering the genetic evolution of ore deposits by presenting and discussing sulfide trace element characteristics from the Hirvilavanmaa (Au-only) and Naakenavaara (Cu-Co-Au-Ni) deposits in the CLB.Principal component analysis also proves to be a valuable tool in distinguishing different processes and metal associations in the deposits.
There are distinct differences in trace element concentrations of pyrite from the two deposits.The Hirvilavanmaa deposit is characterized by free gold at both micrometer and nanometer scale.Based on pyrite and chalcopyrite trace element geochemistry, ore deposition at Hirvilavanmaa took place at higher temperatures compared to Naakenavaara.Chalcopyrite from Hirvilavanmaa is trace element-poor, whereas chalcopyrite from Naakenavaara is much richer in trace elements.At Naakenavaara, pyrite and pyrrhotite are considerably enriched in Co and Ni and are thus notable carriers of these elements in the deposit.
At Hirvilavanmaa, results of our research support an orogenic gold model for the mineralization that progressively developed during multiple pulses, but with the sources of hydrothermal fluid remaining relatively homogeneous.Whole-rock and pyrite trace element geochemistry indicate a mafic metavolcanic-rock source for the Au at Hirvilavanmaa.
At Naakenavaara, sulfide trace element geochemistry combined with mineralogical and lithogeochemical observations reveal two spatially coincident mineralizing events: an earlier base metal-rich mineralization being locally overprinted by a late and more restricted orogenic Au event.
With several polymetallic deposits in the greenstone belts of northern Finland being classified as atypical orogenic Au deposits, it will be beneficial to revisit some of these classifications; detailed studies including sulfide trace element geochemistry could help answer if the overprinting of orogenic Au mineralization on earlier base metal-rich mineralization is a widespread peculiarity in Au-rich polymetallic deposits in northern Finland.

Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Fig. 1 .
Fig. 1.(a) Simplified geological map of Central Lapland belt (CLB) showing location of discovered Au-only (yellow circles) and atypical base metal-rich (blue circles) orogenic Au deposits and occurrences.Insert map shows position of CLB in Finland.Base map modified from the Mineral Deposits and Exploration database of the Geological Survey of Finland (GTK, 2021); information about the depicted deposits and occurrences taken from the same source.(b) Detailed view of marked area from Fig. 1a, showing location of Hirvilavanmaa and Naakenavaara deposits.(c) Stratigraphic column of CLB, modified after Köykkä et al. (2019).(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3 .
Fig. 3. Representative photographs of host rocks at Hirvilavanmaa.(a) Quartz vein with a carbonate selvage cutting a chlorite-carbonate schist.An older, thinner carbonate-rich veinlet is also visible.(b) Stockwork network of quartz-carbonate veins on a rock with albite-carbonate-chlorite alteration.(c) Quartz vein with carbonate selvage being cut by later quartz veins of different orientation.(d) Quartz vein with patchy carbonate containing slivers of altered host rock rich in chlorite, tourmaline and pyrite.(e) A thick quartz vein with patchy cream-colored carbonate and fine pyrite near the rim.Visible is also an older thin carbonate-rich vein.(f) Quartz-carbonate stockwork veins cutting a rock with chlorite-albite-carbonate-talc alteration.(g) Quartz vein with patchy carbonate and coarse euhedral pyrite (h) Talc-rich part of host rock being cut by quartz-carbonate vein with pyrite and hematite in the alteration halo.(i) Quartz-carbonate vein containing tourmaline-and sulfide-rich slivers of host rock.(j) Albite-talc-chlorite alteration on host rock and different generations of quartz-carbonate veins.Disseminated pyrite is present both in the veins and in the alteration haloes around them.

Fig. 4 .
Fig. 4. Photomicrographs from selected Hirvilavanmaa thin sections.Abbreviations: Ab = albite, Au = native Au, Car = carbonate mineral, Ccp = chalcopyrite, Chl = chlorite, Gn = galena, Hem = hematite, Mag = magnetite, Po = pyrrhotite, Py = pyrite, Qtz = quartz, Rt = rutile, Tlc = talc, Tur = tourmaline.(a) Chloritetourmaline-sulfide-rich sliver of host rock in a quartz-carbonate vein.(b) Tourmaline associated with pyrite in a chlorite-rich area.(c) Sulfides and tourmaline constrained within a chlorite sheet overprinting earlier alteration.(d) Sulfides strictly following the orientation of a chlorite-altered area in the alteration halo of a quartz-carbonate vein (e) Chlorite-rich part of host rock containing sulfides and carbonate minerals adjacent to quartz vein.(f) Carbonate mineral porphyroclasts in a talc-rich groundmass.(g) Talc-rich area in an albitite.Crossed polars.(h) Coarse carbonate forming the selvage of a quartz vein, bordering fine-grained part of host rock comprising chlorite, albite and fine carbonate.Crossed polars.(i) Albitized vein cutting a carbonate-rich part of host rock.Crossed polars.(j) Disseminated pyrite forming individual grains and grain aggregates.(k) Pyrite closely associated with hematite and magnetite.(l) Disseminated pyrite together with hematite.(m) Pyrite with native Au inclusions.(n) Disseminated pyrite.The largest pyrite contains abundant silicate mineral inclusions in the core together with a relatively large native Au inclusion.(o) Part of pyrite containing native Au inclusions.(p) Pyrite grain aggregate with native Au inclusions.(q) Part of a pyrite grain containing pyrrhotite and galena inclusions and a mixed galena-Au inclusion.(r) Pyrite and chalcopyrite in a mixed sulfide patch.

Fig. 5 .
Fig. 5. Representative photographs of host rocks at Naakenavaara.Samples are depicted wet unless stated otherwise.(a) Part of a folded graphite phyllite comprising different laminations; lighter zones are sericite-rich and darker zones comprise mainly chlorite, sericite and graphite.Sample is dry (b) Carbonate-rich sulfide-bearing veins cutting a host rock characterized by chlorite and biotite alteration.(c) Phyllite comprising different sericite-and graphite-rich layers being cut by quartz-carbonate veins that contain chalcopyrite and pyrrhotite.(d) Part of Cu-Au ore zone: quartz-carbonate vein with abundant chalcopyrite and pyrrhotite.(e) Sulfide-bearing quartz-carbonate veins cutting a chlorite-and biotite-rich part of host rock; Cu-Au ore zone.(f) Sericite-biotite schist being cut by sulfide-bearing carbonatequartz veins.Sample is dry.(g) Albitite cut by thin sulfide-bearing carbonate-rich veins.(h) Thick carbonate-quartz vein brecciating albitized host rock; vein containing abundant pyrite.Part of a Co ore zone.(i) Albitized sericite schist cut by various quartz-carbonate veins that contain abundant pyrite.Part of a Co ore zone.(j) Part of a thick carbonate-rich vein containing disseminated sulfides.From a drill core interval enriched both in Cu and Co. (k) Part of a thick carbonate-rich vein with small patches of mica schists forming breccias.Vein contains patchy sulfides.Part of a Co ore zone.(l) Mica schist cut by several sulfide-bearing carbonate-quartz veins.Part of a Cu-Au ore zone.

Fig. 6 .
Fig. 6.Photomicrographs from selected Naakenavaara thin sections.Abbreviations: Ab = albite, Au = native Au, Bt = biotite, Car = carbonate mineral, Cob = cobaltite, Ccp = chalcopyrite, Chl = chlorite, Gr = graphite-rich zone, Pn = pentlandite, Po = pyrrhotite, Py = pyrite, Qtz = quartz, Ser = sericite.(a) Quartz vein with biotite inside the vein and as a rim, cutting a sericite-rich part of host rock.(b) Sericite-rich host rock cut by pyrite-bearing quartz veins with different orientations.(c) Chlorite and biotite closely associated with sulfides.(d) Carbonate-quartz vein with coarse carbonate grains and sulfides cutting through sericite-rich host rock.Biotite creates a thin rim to the vein.(e) Interchanging sericite-and graphite-rich zones in a phyllite.(f) Graphite-rich zone cut by a sulfide-and biotitebearing quartz-carbonate vein.(g) Sericite-and graphite-rich part of host rock cut by a quartz-carbonate vein.(h) Sericite-rich host rock cut by various sulfidebearing quartz veins.(i) Sericite-rich host rock cut by a quartz-carbonate-albite vein.(j) Chalcopyrite-pyrrhotite patch from a Cu-rich zone.(k) Patchy chalcopyrite and pyrrhotite from a Cu-rich sample.(l) Native Au inclusions in carbonate from a late carbonate vein (m) Anhedral pyrite (Py Naak -low) together with pyrrhotite; part of a Cu-and Au-rich sample.(n) Anhedral pyrite (Py Naak -high) intergrown with pyrrhotite; part of a Cu-rich sample.(o) Pentlandite flames in pyrrhotite from a sample with elevated Ni content.(p) Disseminated subhedral pyrite (Py Naak -mid) in a Co-rich sample.(q) Euhedral pyrite (Py Naak -mid) together with minor chalcopyrite in a Co-rich sample.(r) Cobaltite inclusions in pyrrhotite; part of a Co-rich sample.

Fig. 7 .
Fig. 7. (a) Selected trace element boxplots with logarithmic scale for all measured pyrite from Hirvilavanmaa (orange boxes; n = 261) and Naakenavaara (blue boxes; n = 133).(b) Selected trace element boxplots with logarithmic scale for all measured chalcopyrite from Hirvilavanmaa (yellow boxes; n = 10) and Naakenavaara (light blue boxes; n = 36).(c) Selected trace element boxplots with logarithmic scale for all measured pyrrhotite from Naakenavaara (n = 44).(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 8 .
Fig. 8. (A) Co-Ni plot for Hirvilavanmaa pyrite with data points classified according to degree of Au enrichment in the samples.Marked parts in the diagram separate three pyrite types according to their Co/Ni ratios.(B) Co-Ni plot for Hirvilavanmaa pyrite with data points classified based on a core-rim distinction.(c) As-Au plot for Hirvilavanmaa pyrite with Au solubility lines from Reich et al. (2005) and Deditius et al. (2014).(D) Trace element boxplots with logarithmic scale for the different pyrite types from Hirvilavanmaa: Py Hirvi -1 (n = 85), Py Hirvi -2 (n = 110), and Py Hirvi -3 (n = 66).

Fig. 9 .
Fig. 9. (A) Co-Ni plot for Naakenavaara pyrite; data are discriminated according to the relationship of the analyzed pyrite to the different types of ore zones.Marked parts in the diagram separate three pyrite types according to their Co/Ni ratios.(B) Co-Ni plot for Naakenavaara pyrite with data classified based on a core-rim distinction.(c) As-Au plot for Naakenavaara pyrite with Au solubility lines from Reich et al. (2005) and Deditius et al. (2014).(D) Trace element boxplots with logarithmic scale for the different pyrite types from Naakenavaara: Py Naak -low (n = 26), Py Naak -mid (n = 64), and Py Naak -high (n = 28).
rich phase that deposited chalcopyrite, pyrrhotite and pyrite belonging to the Py Naak -high type; zones of Co-Cu enrichment could represent a transitional stage in the evolution of this base metal-rich mineralizing stage.This model is further supported by the recognition of several pyrite grains with cores belonging to Py Naak -mid and rims belonging to Py Naak -high in samples with both Cu and Co enrichment.Py Naak -low is present primarily in parts of Cu and Co ore zones that are also enriched in Au, and it is hosted by late carbonate veins that typically cut through older generations of quartz-dominant veins; samples hosting

Fig. 10 .
Fig. 10.Graphical outputs of PCA on whole-rock and pyrite trace element data from the Naakenavaara and Hirvilavanmaa deposits.(A) PC1-PC2 biplot for the Naakenavaara whole-rock data (n = 648).Samples are categorized according to type of metal enrichment.In addition, barren ultramafic metavolcanic rocks are distinguished from the predominantly metasedimentary rocks.(B) PC1-PC2 biplot for the Hirvilavanmaa whole-rock data (n = 370).Samples are categorized according to Au grades.(C) PC1-PC2 biplot for the pyrite trace element data from Naakenavaara (n = 133).Plotted data are categorized according to the three recognized pyrite types.(D) PC1-PC2 biplot for the pyrite trace element data from Hirvilavanmaa (n = 261).Plotted data are categorized according to the three recognized pyrite types.

Table 1
Numerical results of PCA on whole-rock and pyrite trace element data from the Naakenavaara and Hirvilavanmaa deposits.