MASTER`S THESIS

MASTER'S THESIS
Bastutjärn Ni-Cu-Co mineralization
Anders Zettergren
2013
Master of Science in Engineering Technology
Natural Resources Engineering
Luleå University of Technology
Department of Civil, Environmental and Natural resources engineering
Bastutjärn Ni-Cu-Co
mineralization
Anders Zettergren
Master of Science
Natural Resources, Exploration
Luleå University of Technology
Department of Civil, Environmental and Natural Resources Engineering
2
Sammanfattning
Bastutjärn Ni-Cu-Co mineralisering är belägen i en gabbroid intrusion ca 10 km nord-öst om
Norsjö i de syd-centrala delarna av Skelleftefältet. Mineraliseringen uppträder i kontakten
mellan den gabbroida bergarten, klassificerad som gabbronoriter, samt en grafit- och
sulfidrik metasedimentär, delvis skiffrig, bergart. Det förekommer tre olika typer av
mineralisering; disseminerad låghaltig mineralisering som dock upptar stora volymer,
semimassiv sulfidmineralisering samt en semimassiv mineralisering rik på grafit.
Malmmineralen som förekommer är magnetkis, pentlandit samt kopparkis.
Bildningen av Bastutjärns Ni-Cu-Co mineralisering innefattar en inblandning av svavel från de
omgivande krustala bergarterna för att uppnå svavelmättnad i magman. De avblandade
svaveldropparna bildar sedan lager med massivare mineralisering. Kontaktzonen mellan
gabbroiden och metasedimentet består av en kraftig uppmixning av de två bergarterna. Dels
genom xenoliter av sedimentärt ursprung i gabbron samt genom en hybridisering av
gabbron. I mineraliseringen förekommer grafit rikligt vilket pekar på en kraftig inblandning
av sedimentbergarter i bildningsprocessen.
Abstract
Bastutjärn Ni-Cu-Co mineralization is located within a gabbroic intrusion approx. 10 km
north-east of Norsjö village in the south-central parts of the world class massive sulphide
Skellefte District. The mineralization is situated at the contact zone between a gabbroic unit,
classified as gabbronorite, and a graphite- and sulphide-rich metasedimentary unit. Three
different types of mineralization occurs, a disseminated low grade, extensive volume with
disseminated pyrrhotite, a semi-massive pyrrhotite mineralization and a semi-massive
pyrrhotite mineralization-rich in graphite and sedimentary fragments. Ore bearing minerals
are solely pyrrhotite, pentlandite and chalcopyrite.
Formation of the Bastutjärn Ni-Cu-Co deposit includes an involvement of sulphur from the
surrounding crustal rocks to achieve sulphide immiscibility. The separated droplets of
sulphides creates layers of more massive mineralization. The contact zone between the two
rock units is consisting of an area where a major mixing process has occurred, which can be
seen by xenoliths and hybridization of the gabbroic rock. Large amount of graphite is found
within the mineralization, suggesting that an intense mixing with the surrounding
sedimentary unit took place during formation.
3
Table of content
1.
Introduction ........................................................................................................................ 8
1.1 Studied area .................................................................................................................... 10
1.2 Origin of Ni-Cu ores ........................................................................................................ 11
2 Geological setting .................................................................................................................. 12
2.1 Regional geology ............................................................................................................. 12
2.2 Geology of the Bastutjärn intrusion ............................................................................... 14
3 Method .................................................................................................................................. 15
3.1 Mapping .......................................................................................................................... 15
3.2 Core logging .................................................................................................................... 15
3.3 Rock chip logging ............................................................................................................ 16
3.4 Thin sections ................................................................................................................... 16
3.5 Geochemistry.................................................................................................................. 16
3.5.1 Recalculation of whole rock geochemistry data ...................................................... 17
3.5.2 Recalculation of metal content in 100% sulphides .................................................. 17
4 Rock types ............................................................................................................................. 18
4.1 Gabbroic rocks ................................................................................................................ 18
4.1.1 Relations between the gabbroic rocks .................................................................... 20
4.1.2 Contact gabbro-country rock ................................................................................... 20
4.2 Metasedimentary rocks .................................................................................................. 21
4.3 Dikes................................................................................................................................ 21
4.4 Alteration ........................................................................................................................ 21
5 Rock geochemistry ................................................................................................................ 22
5.1 Major element ................................................................................................................ 22
5.1.1 Classification diagrams............................................................................................. 23
5.1.2 Chemical layering ..................................................................................................... 24
5.2 Trace element ................................................................................................................. 27
5.3 CIPW normalization of whole rock geochemistry .......................................................... 28
6 Mineralization ....................................................................................................................... 29
6.1 Profiles ............................................................................................................................ 33
7 Discussion .............................................................................................................................. 34
7.1 Parent magma ................................................................................................................ 34
4
7.2 Gabbro-sediment interaction ......................................................................................... 34
7.3 Ore forming processes .................................................................................................... 35
7.3.1 Sulphur source ......................................................................................................... 35
7.3.2 Pathway.................................................................................................................... 35
7.4 Comparison with other Cu-Ni mineralization ................................................................. 36
7.4.1 Älgliden .................................................................................................................... 36
7.4.2 Näsberg .................................................................................................................... 37
7.4.3 Lainijaur .................................................................................................................... 37
7.4.4 Deposits within the Nickel Belt, Västerbotten ......................................................... 37
7.4.5 Bastutjärn compared to similar deposits ................................................................. 38
7.5 Ore potential................................................................................................................... 39
8 Conclusion ............................................................................................................................. 40
9 Future work ........................................................................................................................... 41
10 Acknowledgements ............................................................................................................. 42
References ................................................................................................................................ 43
Appendices ............................................................................................................................... 46
5
Illustrations
Fig. 1. Simplified geological map over the Skellefte District and its deposits. Bastutjärn
mineralization outlined in the center. Modified after Skyttä et al. 2011. ................................. 9
Fig. 2. Simplified geological map over Bastutjärn project area. Modified from SGU Bedrock
map 23J Norsjö SV and SO (Bergström et al. 2003. © Sveriges geologiska undersökning...... 10
Fig. 3. Stages in the conception, delivery, and development of a theoretical magmatic Ni-Cu
sulphide deposit. A model where the formation of the mineralization at Bastutjärn could fit
in to, as discussed in later chapters. Naldrett (2010). ............................................................. 12
Fig. 4. Geological provinces of the Baltic Shield. (Weihed et al 1992). .................................... 14
Fig. 5. Location and number of channel samples taken from outcrops within the project area.
Note that outcrops are only found in north and east of the gabbroic intrusion. Profile 1 and
Profile 2 refers to Fig. 16-17. .................................................................................................... 15
Fig. 6. Plot with all gabbroic samples, with respect to their modal composition determined
from thin section estimation. (Streckeisen, 1976) ................................................................... 19
Fig. 7. Gabbroic samples from Bastutjärn. TAS Na2O + K2O vs SiO2 plutonic after Cox et al.,
1979. ......................................................................................................................................... 19
Fig. 8. Photomicrographs (plane light) of gabbronorite samples from Bastutjärn A: Secondary
biotite foliation within plagioclase and pyroxene grains, 10X plane polarized light sample
20121001. B: Chlorite alteration of pyroxene, 10X plane polarized light sample 20121005. C:
Biotite and phlogopite intergrowth within pyroxene grain, 20X plane polarized light sample
20111521. ................................................................................................................................. 22
Fig. 9. AFM-diagram (Irvine & Baragar 1971). Samples from gabbroic rocks (Black squares),
hybride rocks (Violet stars) and granodiorite (blue triangles) from Bastutjärn. ..................... 23
Fig. 10. K2O- versus SiO2-diagram (Middlemost 1974). Samples from rocks at Bastutjärn.
Legend see Fig. 9. ..................................................................................................................... 24
Fig. 11. A + B. Plots of downhole data of major oxides from drill hole 4 at Bastutjärn. .......... 25
Fig. 12. Plots of Mg/(Fe+Mg) ratio versus major element oxides for the Bastutjärn intrusion.
A: SiO2 B: Al2O3 C: CaO D: Na2O E: K2O F: Cr2O3 G: TiO2 H: P2O5. ............................................. 26
Fig. 13. Plots of Mg/(Fe+Mg) ratio versus trace elements of the Bastutjärn intrusion. .......... 27
Fig. 14. Photomicrographs (reflected light) of mineralized samples from Bastutjärn. CcP =
Chalcopyrite, Grp = Graphite, Mag = Magnetite, Pent = Pentlandite, Po = Pyrrhotite. A:
Pyrrhotite with pentlandite and chalcopyrite inclusions. Chalcopyrite as fracture filling and
pentlandite exsolution texture, 20X sample 20121006. B: Magnetite in center. Lower part of
the picture is rich in graphite. 20X sample 20121006. C: Pentlandite exsolution in pyrrhotite
grain, 50X sample 20121019. D: Chalcopyrite vein within semi-massive pyrrhotite, 5X sample
20121019. E: Large pentlandite grain within pyrrhotite, 20X sample 20121019. F: Part of the
mineralization rich in graphite, 10X 20121019. ....................................................................... 31
Fig. 15. Relationships between elements in the sulphide mineralization at Bastutjärn. Fig.
a,b,c n=108 from ore sample analyzes Fig. d,e n=148 from rock chip samples. ..................... 32
Fig. 16. Profile 1 Section 940 W. For location see Fig. 5. ......................................................... 33
6
Fig. 17. Profile 2 Section 1000 W. For location see Fig. 5. ....................................................... 33
Fig. 18. Plot of Ni grade (%) vs resource of Ni ore (Mton) in world class deposits divided into
different deposit types. After Jaireth et al. (2005). ................................................................. 40
Tables
Table 1. Elements analyzed in whole rock geochemistry package CCP-PKG01 at ALS Minerals
.................................................................................................................................................. 17
Table 2. Rock names and definitions by IUGS .......................................................................... 18
Table 3. Average composition of major elements in % for gabbronorite samples. ................ 20
Table 4. Average composition in % of 19 metasedimentary rock chip samples southwest of
the mineralization. Trace metals in ppm. ................................................................................ 21
Table 5. CIPW norm vs modal composition TS20121005. ....................................................... 28
Table 6. Data on selected Swedish nickel deposits. Note that all data except Blackstone data
are historical and not NI 43-101 compliant. NiS is the content of Nickel in 100 % sulphides. . 36
Table 7. Elements in 100 % sulphides, n = 108 ore samples. % MeS = percentage of metal in
100 % sulphide phase. .............................................................................................................. 38
Table 8. Historical estimation of the mineralization at Bastutjärn. “Ore” zone includes the
upper Lens 1 and lower Lens 2 plus marginal ore between these lenses. Internal Report
Boliden Mineral 1974. .............................................................................................................. 39
Appendix
Appendix 1 Graphic drill core logs
Appendix 2 Raw data whole rock geochemistry
Appendix 3 Recalculated whole rock geochemistry
Appendix 4 CIPW normalization
7
1. Introduction
The Bastutjärn gabbro intrusion is located in the Västerbotten county, 10 km NE of Norsjö
and 70 km W of Skellefteå. The intrusion, which hosts a Ni-Cu-Co mineralization, belongs to
the central Palaeoproterozoic Skellefte District (Årebäck et al. 2005). Within this district
several deposits, mostly of VMS-type, have been mined and five deposits are being exploited
today, all of them operated by Boliden Mineral AB. Gold deposits of quartz vein type are
also found in the area, one of them is currently mined by Björkdalsgruvan AB. Besides from
volcanogenic massive sulphides this mining district hosts economic important deposits of
mafic intrusion nickel and porphyry copper type (Weihed et al. 1992).
Historically polymetalic VMS-type deposits have been of greatest interest for exploration
and mining companies within the district since the first discoveries of the famous gold-rich
Boliden deposit in the 1920´s, but other metals have also been mined. At the Lainijaur Ni-Cu
deposit, associated with a gabbroic intrusion, a total of 100.526 ton, averaging 2.20 % Ni,
0.93 % Cu and 0.1 % Co have been mined during the years 1941-1945 (Grip 1961 & Nilsson
1985). In the central part of Västerbotten, south of the Skellefte District, a nickel belt
containing several deposits with Ni-Cu occur within an area from Bureå at the coastline to
Örträsk in the west. Most exploration in this area was conducted in the 1970´s and today
more than 40 prospects are known, where Lappvattnet and Rörmyrberget are the largest
deposits (Fig 1). All deposits in this area are associated with ultramafic bodies, except for the
Rörmyrberget deposit where gabbroic rocks are found. Besides Lainijaur no other deposit
with Ni as primary metal has been mined within the Skellefte District or northern Sweden,
despite several promising occurrences. One of these is the Bastutjärn Ni-Cu-Co
mineralization, hosted within the Bastutjärn gabbro intrusion. The area has been known
since 1940s when several nickel mineralized boulders where found at Bastutjärn and
Kvavisträsk, which were located downstream in the ice direction (Grip 1961). In 1971,
promising boulders was found in the area and an exploration program lead by Boliden
Mineral resulted in the discovery of mineralized outcrops (Årsrapport 1973). A drilling
program with 11 holes was undertaken during 1974 and Ni-Cu mineralization where found in
core (Årsrapport 1974). The area has been a target for PGE-Au exploration by SGAB during a
8
field campaign 1987, but all analyzed samples showed PGE-values under detection limit and
no clear magmatic layering was found (Filén 1988).
Fig. 1. Simplified geological map over the Skellefte District and its deposits. Bastutjärn mineralization
outlined in the center. Modified after Skyttä et al. 2011.
The aim in this study is to get a better understanding of the geology in the project area. This
will be done by:
-Relogging and reinterpretation of the geological model.
-Description of rock types.
-Description of mineralization and ore minerals.
-Geochemical characteristics.
-Discussion of the link between gabbro and surrounding sedimentary units.
9
1.1 Studied area
The Bastutjärn project area is located 45 km west of Boliden and 10 km NE of Norsjö,
Västerbotten county (Fig.1 and 5). The intrusion is located south of the river Malån and
north of the village Bastutjärn. Dimensions of the gabbro complex is 5x3 km and the shape is
oval based on geophysical gravity maps. Earlier mapping was undertaken by SGU, that
resulted in a geological map of semi-local scale (1:50 000). More intense mapping and also
trenching have been done by Boliden Mineral, which has given a better detail of the surface
geology. The area is affected by glacial activities and a majority of the bedrock is covered by
glacial till, like the rest of northern Sweden. Compared to other sites in this part of Sweden
this area has a quite high percentage of outcrops, mainly in the northern and eastern parts.
In the south-west, where the mineralization is situated, the thickness of till reaches its
maximum 30 meters. This fact makes it difficult to map, from an economic point of view, the
most interesting areas in outcrop.
Fig. 2. Simplified geological map over Bastutjärn project area. Modified from SGU Bedrock map 23J Norsjö SV
and SO (Bergström et al. 2003. © Sveriges geologiska undersökning.
10
1.2 Origin of Ni-Cu ores
Magmatic Ni-Cu mineralizations are formed by a primitive or differentiated magma of maficultramafic nature. The sulphur saturation stage is an important key in the ore forming
process, which must be achieved during cooling in order to create a sulphide liquid.
Chalcophile elements like Cu and Ni elements accumulate into the sulphide melt which will
deposit, either in the top of the cumulate or in embayments within the magma conduit
(Naldrett 2010; Maier 2011). Ni-Cu ores are associated with different types of ultramaficmafic rocks, including komatiites, dunites, harzburgite, pyroxenite, olivine gabbro,
gabbronorite and troctolite (Naldrett 2004). The general host bodies for the mineralization
are intrusions, often small, as dykes, sills, magma channels or other irregularly shaped
intrusions. (Naldrett 2010).
Magma of mantle origin needs to have a high degree of melting to be able to host critical
amounts of nickel, at a ore forming point of view. This is due to the fact that nickel is
primarily situated in olivine. The content of olivine in the melted mantle is therefore
controlling the nickel content in the magma (Naldrett 2010). To produce a Cu-rich magma
partial melting is needed, as Cu is situated in the sulphides in the mantle. In basaltic magmas
sulphur has a relatively low solubility, so there a partial melting of approx. 20 % is required
(Naldret 2004). When magma is produced it needs pathways to rise upwards. Magma
convection at a regional scale generates extensional areas, which acts as pathways for the
magma (Naldrett 2010).
Due to pressure and solubility conditions for sulphur, primitive magmas are generally Sundersaturated. Saturation is critical in the ore forming process as it generates the sulphide
liquid. Through differentiation it is possible to enrich the magma in S to achieve saturation,
because S is not present in silicate minerals (Maier 2011). Other processes that could be
important to achieve S-saturation is magma mixing and pressure changes. For many of the
most important Ni-Cu deposits in the world isotopic studies show that external sulphur must
have been added into the system during magma emplacement. External sulphur is extracted
from crustal rocks such as black shales, banded iron formations, evaporites and other rocks
which host a high level of sulphur (Maier 2011). In some cases isotopic studies show little or
no influence of crustal addition of sulphur. This could prove that the magma in some cases
derives enough sulphur from the mantle source to generate a liquid phase. A good example
11
where isotopic studies show no external contribution of sulphur is the deposit Nebo-Babel,
western Australia (Seat et al. 2007).
Fig. 3. Stages in the conception, delivery, and development of a theoretical magmatic Ni-Cu sulphide deposit.
A model where the formation of the mineralization at Bastutjärn could fit in to, as discussed in later
chapters. Naldrett (2010).
2 Geological setting
2.1 Regional geology
The project area is located in the south central part of the Palaeoprotorezoic Skellefte
District, which is part of the larger Fennoscandian shield. The Fennoscandian shield (Fig. 4) is
a segment in the east European craton that also comprises areas more to the south which
consist mainly of Precambrian rocks covered by platform sediments (Lahtinen et al. 2005).
Formation of the Fennoscandian shield is divided into four different accretion phases
according to their age. Oldest is the basement formed at the Saamian orogeny (3.1 - 2.9 Ga),
which mainly comprises tonalites and trondhjemites. The period was followed by the Lopian
orogeny (2.9 - 2.6) that was a period with formation of high grade gneisses, granites as well
as greenstones. The Archean rocks was followed by a period of intracratonic sedimentation
and volcanism in early Proterozoic age. Activation of a passive margin started the
Svecofennian orogeny (2.0 - 1.75 Ga) (Gaal & Gorbatschev 1987), which formed the Skellefte
12
District from a destructive margin at 1.89 Ga. This island arc environment hosts volcanogenic
massive sulphides and also porphyry type deposits. According to the classification of massive
sulphide deposits, Skellefte District fits best into the Kuroko type of deposits (Weihed 1992).
Rifting south of the area generated an extensive greywacke sequence, called the Bothnian
basin (~1.95 Ga), which was intruded by mafic to ultramafic rocks that host Ni deposits in the
so called Nickel belt. These deposits are believed to be in same age or slightly younger than
the sedimentary unit (Weihed 1992). Geochemical data gives the mafic rock a MORB or
Island arc type of signature, reflecting an extensional environment (Weihed 1992).This does
not exclude a back arc setting which Gaal & Gorbatschev (1987) have considered the mafic
rocks to belong to an oceanic island arc at 1.93 – 1.90 Ga. Closing of the sedimentary basin,
that is spanning 500 km south to the Bergslagen area, halted at 1.87 Ga (Nironen 1997).
Subduction in the Skellefte District resulted in many granitoid intrusions, classified according
to age of emplacement by Gaal & Gorbatschev (1987). Early orogenic (1.89-1.85 Ga), late
orogenic which comprises the Skellefte-Härnö granites (1.84-1.81 Ga) and the post orogenic
Revsundgranite (1.80-1.77 Ga). The Revsundgranite is of same age as the extensive
Transscandinavian igneous belt, that covers a large area from southeastern Sweden to the
north (Gaal & Gorbatschev 1987).
13
Fig. 4. Geological provinces of the Baltic Shield. (Weihed et al 1992).
2.2 Geology of the Bastutjärn intrusion
The project area (Fig. 2) consists of an oval shaped gabbroic intrusion, approximately 3 x 5
km, surrounded by graphite- and pyrite-rich metasedimentary units (shales), granites of
Revsund type (according to SGU bedrock map sheet 23J) and volcanic rocks belonging to the
Skellefte group. Based on available drill holes, the thickness of the gabbroic intrusion seems
to be around 200 meters. Within the area a sulphide mineralization is present and hosts
significant amounts of nickel, copper and cobalt. This mineralization is hosted by the gabbro
unit near and at the contact to the sedimentary unit in the south of the area. The
sedimentary unit comprises mainly graphite-rich shales with decent amounts of pyrrhotite.
Shales rich in sulphides are a common feature in the Skellefte District (Martinsson 1996).
14
3 Method
3.1 Mapping
During the summer year 2011 fieldwork was undertaken at the Bastutjärn area.
Reconnaissance work was done to briefly map outcrops within the explored area, were
outcrops where chosen for whole rock geochemistry and thin section samples. Totally 9
channel samples were taken with a hand held rotation diamond saw. Localities for these
samples are indicated in Figure 5. Due to the glaciated till conditions, most of the outcrops
are located in the northern part of the intrusion.
Profile 2
Profile 1
Fig. 5. Location and number of channel samples taken from outcrops within the project area. Note that
outcrops are only found in north and east of the gabbroic intrusion. Profile 1 and Profile 2 refers to Fig. 1617.
3.2 Core logging
From earlier exploration work 11 drill holes have been done and the cores are since that
time stored at Boliden Minerals drill core facilities in Boliden. Six of these cores were
selected for further detailed studies, based on their spatial relationship to the
mineralization. These cores have earlier been logged, sampled and analyzed. Except for 3
drill cores, which were relogged in 2010, they are only analyzed for nickel, copper and
15
sulphur. For this thesis the cores have been reanalyzed, both for ore analyzes and for certain
sections lithogeochemical analyze. Ore analyzes where performed at Labtium Oy, Rovaniemi
, lithogeochemistry samples was sent to ALS Minerals, first prepared in Piteå and then
analyzed in Vancouver.
3.3 Rock chip logging
Together with drill cores and outcrop mapping, rock chip samples have been logged and
analyzed to achieve further detailed information of the geology. Rock chip sampling was
performed on a number of localities within the project area by percussion drilling. Sampling
was done from the bedrock surface and approximately 1 meter down in the rock. Coarsegrained material (>4 mm and >2 mm) was then separated from the fine fraction and the
resulting two products where used for further studies. To determine the rock type,
mineralogy and in some cases structures, optical microscope was used.
3.4 Thin sections
Thin sections were taken from both drill core and outcrop samples. A total of 12 samples
were sent to Vancover Petrographics for preparation, of which 7 were covered thin sections
(30 microns, 26x46 mm), 3 polished thin sections (30 microns, 26x46 mm) and 2 polished
thick sections (300 microns, 25 mm circular). A Nikon stereo microscope was used, both for
opaque and transparent mineralogy. Determination of plagioclase composition was done by
the Michel-Levy method. In this method a single grain of plagioclase is selected, where the
two extinction angles are measured for each grain. This was repeated several times on every
thin section which resulted in a mean value. Inserting this value in a diagram gives the
plagioclase composition of the sample.
3.5 Geochemistry
A total number of 36 (excluding the rock chips) samples were sent to ALS Minerals in
Vancouver for whole rock analysis, code CCP-PKG01. A complete list of analyzed elements is
shown in Table 1. Gold was analyzed in rock chip and outcrop samples.
16
Table 1. Elements analyzed in whole rock geochemistry package CCP-PKG01 at ALS Minerals
Major Elements: Si, Al, Fe, Ca, Mg, Na, K, Ti, Mn, P, C, S, LOI
Base Metals: Ag, Cu, Cd, Mo, Ni, Pb, Sc, Zn
Trace elements and REE´s: Ba, Ce, Cr, Cs, Dy, Er, Eu, Ga, Gd, Hf, Ho, La, Lu, Nb, Nd, Pr, Rb, Sm, Sn, Sr,
Ta, Tb, Th, Tl, Tm, U, V, W, Y, Yb, Zr
Volatiles: As, Bi, Hg, Sb, Se, Te
3.5.1 Recalculation of whole rock geochemistry data
Whole rock analysis data reflects the average composition of the rock. When sulphides are
present they are included in the analysis so that the data is the composition of both host
rock and sulphides. In that case the data must be modified to get the correct composition of
the host rock without sulphides. Elements hosted in the sulphides are iron (pentlandite,
chalcopyrite and pyrrhotite), copper (chalcopyrite) and nickel (pentlandite). The method of
recalculation includes the following steps (modified after Li et al. 2000 & De Waal et al.
2004).
Remove all Cu by forming chalcopyrite (CuFeS2), as this is the only major mineral hosting Cu.
Next step is to remove Ni, which is hosted in pentlandite or olivine if present. Petrographic
studies and geochemical modeling show that these rocks contain no olivine. With this
background all Ni is calculated for creation of pentlandite. Since the mineralization is rich in
Co, which is considered to be situated within the pentlandite. The formula Fe4Ni4CoS8 were
used when calculating pentlandite.
Remaining sulphur is consumed by creation of pyrrhotite, the dominating iron sulphur
mineral. Pyrite is only present in some samples and mostly within the footwall, so the
amount of the total sulphur situated in the pyrite is negligible.
3.5.2 Recalculation of metal content in 100% sulphides
To compare the different mineralization types the metal content from whole rock
geochemistry have been recalculated into 100 % sulphides. The formula by Barnes and
Lightfoot (2005), was applied:
17
C(100% sul) = Cwr * 100/(2.527 * S + 0.3408 * Cu + 0.4715 * Ni)
Where C(100% sul) = concentration of an element in 100 % sulphides; Cwr = concentration of the
element in the whole rock geochemistry; S, Cu and Ni =concentration of the elements in
whole rock geochemistry.
4 Rock types
By macroscopic and microscopic studies several different rock types where distinguished.
4.1 Gabbroic rocks
The intrusion consists of a gabbronorite which varies in chemical composition and grain size.
In the Table 3 the average composition of this rock is shown. By definition a gabbronorite
consists of plagioclase and equal amounts of orthopyroxene and clinopyroxene (IUGS, Table
2). If orthopyroxene is dominating the rock name should be norite and a clinopyroxene
dominating rock should be gabbro (s.s.).
Table 2. Rock names and definitions by IUGS
Gabbro (s.s.)
Plagioclase + Clinopyroxene
Norite (s.s.)
Plagioclase + Orthopyroxene
Gabbronorite
Plagioclase
+
equal
amount
Ortho
and
Clinopyroxene
Orthopyroxene-Gabbro
Plagioclase + Clino > Orthopyroxene
Clinopyroxene-Norite
Plagioclase + Ortho > Clinopyroxene
Modal mineral composition were approximated in thin section samples. From the gabbroic
samples the main mineral composition consists of plagioclase, clino- and ortho- pyroxene
and also biotite. Based on the nomenclature set up by IUGS the rocks would range from
orthopyroxene-gabbro to clinopyroxene-norite, but the general rock name would be
gabbronorite. All samples plot within the main gabbronorite zone (Fig. 6). Two of the
samples plot on the line that shows equal amounts of the two pyroxenes. In a strict sense
the four samples on the left hand side of the line should be named clinopyroxene-norite and
the two on the right hand side should be named orthopyroxene-gabbro.
18
Fig. 6. Plot with all gabbroic samples, with respect to their modal composition determined from thin section
estimation. (Streckeisen, 1976)
The TAS alkali-silica diagram by Cox et al. (1979) in Figure 7, shows that all samples plot
within the gabbroic field.
Fig. 7. Gabbroic samples from Bastutjärn. TAS Na2O + K2O vs SiO2 plutonic after Cox et al., 1979.
19
Average composition in percent for eight gabbronorite samples are displayed in table 3.
Table 3. Average composition of major elements in % for gabbronorite samples.
SiO2
Al2O3 Fe2O3 CaO
52.29 16.70 9.60
8.85
MgO Na2O K2O
Cr2O3 TiO2
MnO P2O5
SrO
BaO
8.19
0.04
0.14
0.05
0.04
2.48
0.65
0.79
0.19
The gabbronorite rock is equigranular and holocristalline. The rock is in general weakly
altered. Some of the samples are rich in biotite, from 5 % (sample 20111526, 20111528) up
to 25 vol% (sample 20111522). The biotite occurs as primary anhedral flakes up to 7 mm,
often associated with magnetite and with inclusions of mainly plagioclase and minor apatite.
Biotite also occurs as a secondary recrystallised mineral. Figure 8 from sample 20121001
(Appendix 1) is showing orientated biotite, indicating a weak tectonic foliation.
4.1.1 Relations between the gabbroic rocks
From studies of drill core it is clear that the intrusion consists of different generations of
gabbroic rocks. Younger magma injections have intruded older rocks, based on sharp
contacts, with an overall similar composition. There are also gabbros that are crosscutting
mineralized gabbros showing that there must be later magmas that were sulphur
undersaturated. Even if there are clear contacts between the gabbroic rocks, both
geochemical and modal compositions seem to be similar.
4.1.2 Contact gabbro-country rock
Most studied drill cores show that the contact zone between the intrusion and the
metasedimentary country rock is complex. The zone consists of a mix of gabbroic mingled by
metasediments. The gabbroic rock exhibit more xenoliths closer to the contact zone, where
in some cases the contact zone consists of a gabbro-sediment hybrid-rock which are more
fine-grained than the typical gabbronorite. Due to the fact that most of the drilled cores
only are intruding the metasedimentary unit a few tens of meters, it is not possible to
exclude that the gabbro is continuing at depth. Isolated outcrops with metasediments inside
the gabbroic unit have been found at the north western part of the area and one drillhole
(BAB9) intersected metasediment at the start of the hole.
20
4.2 Metasedimentary rocks
Country rock below the intrusion in the southern contact is a metasedimentary unit that
exhibits a black to dark gray color. The rock is fine-grained and a weak foliation can be seen.
As listed in Table 4 these rocks are generally rich in sulphur, mainly as the mineral pyrrhotite,
and carbon hosted as graphite. The texture in rock chip samples and in drill core varies from
homogeneous samples without any structures to more foliated, shale like rock. These
varieties are best seen in drill core, where the sediments occur also as xenoliths within the
gabbroic intrusion.
Table 4. Average composition in % of 19 metasedimentary rock chip samples southwest of the
mineralization. Trace metals in ppm.
SiO2
Al2O3 Fe2O3 CaO
MgO
Na2O
K2O
Cr2O3 TiO2
MnO
P2O5
SrO
BaO
C
S
60.83
14.79
8.85
2.28
3.06
2.19
2.58
0.02
0.07
0.13
0.02
0.06
1.30
1.42
Co
Cu
Mo
Ni
Pb
Zn
61.10
14.71
8.80
2.27
3.09
2.18
0.75
4.3 Dikes
Several dikes cross-cut the intrusion. One type is mafic dikes, which are fine-grained and
black to grey in color. The dikes show a sharp contact to the gabbroic rocks, and are partly
infiltrated with carbonate minerals. The more felsic dikes are often granitic in composition,
fine-grained and with a slightly red tint. These felsic dykes are typically crushed and
brecciated. A few quartz-carbonate veins intrude the gabbroic rock as well, typically they are
pink and fine-grained.
4.4 Alteration
The gabbroic rocks at Bastutjärn show only a weak alteration of the primary minerals. The
main alteration mineral is chlorite, which is found as a product of alteration of the
ferromagnesian pyroxenes (Fig. 8B). Secondary biotite is as well a common alteration
product which commonly coexists with phlogopite (Fig. 8C).
21
Fig. 8. Photomicrographs (plane light) of gabbronorite samples from Bastutjärn A: Secondary biotite foliation
within plagioclase and pyroxene grains, 10X plane polarized light sample 20121001. B: Chlorite alteration of
pyroxene, 10X plane polarized light sample 20121005. C: Biotite and phlogopite intergrowth within pyroxene
grain, 20X plane polarized light sample 20111521.
5 Rock geochemistry
The rock types within the Bastutjärn intrusion show a small variation in the silica content
(mainly between 52 to 54 % SiO, Fig. 12). The plots of major and trace elements are against
the MgO/(MgO + FeO + Fe2O3) ratio (Mg-number), as plots against silica do not show the
differentiation trends within the different rock types in the intrusion.
5.1 Major element
Raw data from the geochemical analyses are presented in Appendix 1. The results have been
recalculated to a sulphur free and volatile free basis (Appendix 2). Recalculated samples with
large amount of sulphides should be taken with care. The effect of later alteration on the
rocks seems to have a minor effect on the chemical composition as discussed later.
22
Plots including the MgO/(FeO+MgO) ratio versus major element oxides shows in most cases
a clear systematical trend (Fig. 12). Systematics that can bli explained by fractionated
crystallization when the magma evolves.
The MgO/(FeO+MgO) ratio shows a positive
correlation with SiO2, Al2O3 and Cr2O3, for Na2, TiO2 and P2O5 the correlation is negative. K2O
and CaO show an unclear trend versus the ratio. Four samples have been classified to not
belong to the typical Gabbronorites at Bastutjärn, the hybridized gabbro/metasediments and
the fine-grained gabbro.
5.1.1 Classification diagrams
From the assay data plotting was done to classify the gabbroic rocks according to magma
character. Plotting in AFM (Fig. 9) diagram gives a tholeiitic trend for the magma.
Gabbroic samples plotted in the discrimination diagram SiO2 vs K2O (Fig. 10) results in a
subalkalic rock.
Fig. 9. AFM-diagram (Irvine & Baragar 1971). Samples from gabbroic rocks (Black squares), hybride rocks
(Violet stars) and granodiorite (blue triangles) from Bastutjärn.
23
Fig. 10. K2O- versus SiO2-diagram (Middlemost 1974). Samples from rocks at Bastutjärn. Legend see Fig. 9.
5.1.2 Chemical layering
Drill hole BAB 4 was sampled systematically in order to define an eventual cryptic layering
(Fig. 11 A + B). Samples below 100 m are gabbroic rocks surrounded by metasediments
(Appendix 1). A major peak in MgO and a weak depletion of CaO can be seen in the lower
part of the intrusion (Fig. 11 A). Also Cr2O3 increases down hole, showing a more mafic
character in the lower samples (Fig. 11 B).
24
A
B
Fig. 11. A + B. Plots of downhole data of major oxides from drill hole 4 at Bastutjärn.
25
Fig. 12. Plots of Mg/(Fe+Mg) ratio versus major element oxides for the Bastutjärn intrusion. A: SiO2 B: Al2O3
C: CaO D: Na2O E: K2O F: Cr2O3 G: TiO2 H: P2O5.
26
5.2 Trace element
Fig. 13. Plots of Mg/(Fe+Mg) ratio versus trace elements of the Bastutjärn intrusion.
Results from trace element analysis of gabbroic samples are listed in Appendix 2 and plotted
against the MgO/(FeO+MgO) ratio (Fig. 11). Europium, Niobium, Sulphur and Zirconium
show a clear correlation with the ratio. Vanadium also shows a correlation, but in this case it
is more unclear. This could be a product of the hybridization process in the area, where the
input of Vanadium is from the surrounding sediments.
27
5.3 CIPW normalization of whole rock geochemistry
CIPW normalization was undertaken on a number of samples with whole rock geochemistry
(Appendix 4). Modal composition was estimated on most of the samples, apart from
TS20121003 which was fine-grained and individual grains where impossible to define. CIPW
normalization gives a rough overview about which mineral assemblage that could be
expected from the crystallized melt. In Table 5 samples with CIPW normative composition is
compared against the estimated mineral volumes from thin section, which gives a slightly
different result. The gabbronorites mineralogy is mainly consisting of plagioclase and
pyroxenes, but from CIPW there should be some quartz, orthoclase and diopside. Although
the CIPW gives a pure theoretical composition, it follows the main mineralogical variations
estimated from thin section.
Table 5. CIPW norm vs modal composition TS20121005.
Thin section
TS20121005 CIPW %
Quartz
3.23
Plagioclase
60.82
Orthoclase
6.93
Diopside
2.48
Hypersthene
25.22
50
10
30
Augite
Olivine
0.00
Ilmenite
0.50
Magnetite
0.59
Apatite
0.19
Chromite
0.04
10
Biotite
Total
%
100.00
100
28
6 Mineralization
The Bastutjärn mineralization occurs as disseminated sulphide droplets and as semi-massive
to massive lenses. The disseminated zone consists of dropletlike pyrrhotite grains with
pentlandite inclusions and minor chalcopyrite. This zone is rather subeconomic and the
amount of nickel and copper are low. On the other hand this zone is widespread and the
area between highgrade zones is mostly of disseminated style.
Zones with highest grades are solely found in semi-massive to massive zones of pyrrhotite
lenses, rarely wider than 40 cm. These lenses are concentrated and are therefore forming
wider zones with interesting grades. Chalcopyrite occurs frequently and is mainly forming
veins within the semi-massive pyrrhotite.
In general the PGE grades within the mineralization and the intrusion is very low or below
detection limit. Grades of Gold are in general very low, but follow the pattern for the main
mineralization and the grades are highest where the richest mineralization occur. One
element that is elevated and may be of further interest is molybdenum.
From this study three different types of sulphide mineralization are found. First, and most
widely spread, the disseminated pyrrhotite mineralization which is characterized by droplet
textured evenly distributed sulphides in the gabbroic matrix. Chalcopyrite and pentlandite
are common as inclusions within pyrrhotite grains. Optical observation shows that the ratio
between pentlandite and pyrrhotite is higher in the disseminated mineralization than in the
more massive type of mineralization. This observation is also done for chalcopyrite.
The second type is the semi-massive to massive sulphide (more than 15 % S), with pyrrhotite
as the dominating sulphide. Chalcopyrite is a common mineral and is together with
pentlandite found as inclusions in the pyrrhotite. Chalcopyrite is also found as later veins
that intrudes the mineralization.
The third and the least abundant type is the graphite-rich semi-massive sulphides, with
pyrrhotite as main sulphide, occurring in fine-grained matrix. This type of mineralization is
unevenly distributed and occurs only in drill hole 4 and 11. The width of this zone is rarely
more than 50 cm and in drill hole 11 it shows sharp contacts to the surrounding gabbro.
Sample LK20121006 (Fig. 14 A and B) is from a section with graphite-rich (5.67 % C) and
29
semi-massive pyrrhotite (11.9 % S). Based on a few sample points, the content of Ni and Cu
seems to be rather low (0.229 % vs. 0.027 %) while carbon content is high. Sulphides in this
type of mineralization are more anhedral and fine-grained compared to the second type of
mineralization. Graphite is very common in the sample 20121019 where it occurs frequently
as minor inclusions in the pyrrhotite (Fig. 14 C-F). Chalcopyrite is less abundant in the sample
20121006 and occurs mainly as inclusions in pyrrhotite, at the pyrrhotite grain rims and as
fracture fillings. Compared to the graphite-rich samples, no chalcopyrite have been seen to
create vein textures, and local areas with higher concentrations seem to be missing.
Pentlandite occurs as inclusions at pyrrhotite grain boundaries and as exsolution textures.
The former type of pentlandite exhibits the largest crystals. Magnetite is also abundant in
the thin sections.
Parts of the mineralization are richer in molybdenum (sample 20121006), a metal which
should not be present in any greater amount in a magmatic nickel sulphide deposit. Higher
values of the other economical important metals are not always followed by molybdenum. A
relationship can be seen between Mo and C (Fig. 15 D). A relationship to the S values can be
seen as well but highest Mo values seem to coincide with higher carbon grades (Fig. 15 E).
30
Po
Ccp
Mag
Grp
Pent
Po
Pent
Po
Ccp
Pent
50 µm
Po
Grp
Pent
Po
Grp
Fig. 14. Photomicrographs (reflected light) of mineralized samples from Bastutjärn. CcP = Chalcopyrite, Grp =
Graphite, Mag = Magnetite, Pent = Pentlandite, Po = Pyrrhotite. A: Pyrrhotite with pentlandite and
chalcopyrite inclusions. Chalcopyrite as fracture filling and pentlandite exsolution texture, 20X sample
20121006. B: Magnetite in center. Lower part of the picture is rich in graphite. 20X sample 20121006. C:
Pentlandite exsolution in pyrrhotite grain, 50X sample 20121019. D: Chalcopyrite vein within semi-massive
pyrrhotite, 5X sample 20121019. E: Large pentlandite grain within pyrrhotite, 20X sample 20121019. F: Part
of the mineralization rich in graphite, 10X 20121019.
31
Fig. 15. Relationships between elements in the sulphide mineralization at Bastutjärn. Fig. a,b,c n=108 from
ore sample analyzes Fig. d,e n=148 from rock chip samples.
32
6.1 Profiles
Fig. 16. Profile 1 Section 940 W. For location see Fig. 5.
Fig. 17. Profile 2 Section 1000 W. For location see Fig. 5.
33
7 Discussion
7.1 Parent magma
Tools to determine the origin and character of a magmatic rock is to plot geochemical data
in discrimination diagrams. The problem in this case is that the rocks are differentiated from
the magma, chilled margins should then be used as a key to the parental magma. However,
in the investigated drill cores in this study, chilled margins were lacking so no good data was
achieved for this kind of plotting. Despite this fact, the gabbroic rocks at Bastutjärn were
plotted in this type of diagrams in order to give a rough estimation of the geotectonic
environment.
The Skellefte District have by many authors (e.g. Gaal & Gorbatschev 1987) been interpreted
as an island arc environment. From the AFM diagram (Fig. 9, Irvine & Baragar 1971) the
samples plot in the tholeiitic trend. The K2O vs SiO2 - diagram (Fig. 10, Middlemost 1985)
gives a sub-alkalic character for the rocks.
From the sampling no clear cryptic or modal layering of the gabbroic intrusion can be
distinguished, although a weak tendency was noticed (Fig. 9). More sampling would be
needed to give a complete image of the instrusion.
7.2 Gabbro-sediment interaction
Most of the major Ni-Cu deposits worldwide are believed to be formed from a process
where the magma has interacted with sulphur-rich country rock (Maier, 2011). The reason
why this is the case in many formation processes is found in the initial magma composition,
which generally contains to little sulphur in order to create a sulphide immiscibility. The
possible source of the sulphur at Bastutjärn is deeper discussed in the next chapter. At
Bastutjärn the interaction between the gabbroic intrusion and the underlying sulphidebearing sediments has not only affected the initial magma composition. There has also been
a huge effect on the rocks in the contact zone, more than 100 meters from the sediments.
This can be seen by large xenoliths of sediments inside the gabbroic body and also as
hybridized rocks where the sediment assimilation changes the texture and composition of
the gabbro.
34
7.3 Ore forming processes
7.3.1 Sulphur source
In magmatic sulphur ores there are two possible sources for the sulphur, which is required
to achieve saturation. A first source is internal sulphur from the magma and the second is
external crustal sulphur, extracted from country rocks. A way to distinguish between these
sources is to commence an isotopic analysis for sulphur. Crustal sulphur would then give
negative δ34S values compared to the internal source which would result in mantle like near
zero values for δ34S. This study does not include isotopic analyses of sulphur, so it is not
possible to suggest a source from isotopic evidence. However, it is possible to suggest that
the sulphur source in this scenario is external and crustal. This is based on features seen in
drill core, outcrops and thin sections. In drill core and also outcrop there is a large amount of
sulphur-rich fragments of sedimentary origin, most likely from the unit that is in contact with
the gabbroic intrusion. The intruding gabbro shows a variety of compositions which may be a
hybridization of the rock due to assimilation of the surrounding sediment. From thin sections
of ore zones large amounts of graphite are noted which may be a result of contamination
from the graphite-rich sediments. Whole rock geochemistry of the surrounding sedimentary
unit shows that these rocks are rich in sulphur and also partly very rich in carbon, in form of
graphite. All these features show that the country rock is a possible source for the sulphur.
To further evaluate and maybe confirm this theory an isotopic study is needed. Sulphur
isotopic studies done on black schists at Mörttjärn, close to the Lainijaur deposit, shows near
zero values which also is reported from pyrrhotite from Ni-Cu mineralization (Martinsson
1996). Near zero sulphur isotopic values are also reported from a majority of the massive
sulphide ores within the Skellefte District (Rickard et al. 1979). This means that if sulphur is
extracted from the surrounding schists to achieve sulphur saturation, this could not always
be shown by isotopic studies if this results in near zero values.
7.3.2 Pathway
One important key to generate a magmatic sulphide deposit is the pathway of magma (Fig.4
Naldrett 2010). This pathway is found where the crust is weak, in crustal lineaments or
faults. Bastutjärn is situated on a regional structural lineament that is suggested to crosscut
the Skellefte District and continue to the Älgliden mafic dyke. From an ore forming point of
view this structure is possibly the pathway for the magma that created the Bastutjärn
35
mineralization. From this structure the magma intruded the metasedimentary unit, creating
an irregularly shaped intrusion.
7.4 Comparison with other Cu-Ni mineralization
Within the Skellefte District a number of mafic to ultramafic intrusions occur, some of them
hosting Ni-Cu mineralization. Most notable are Älgliden, Storbodsund, Näsberg and Lainijaur.
These mineralizations have through the history been studied in a much greater extent than
the Bastutjärn occurrence and can be a tool to give an explanation of the processes included
in the formation. For this thesis a number of deposits have been studied (Table 6), but only a
few were selected for deeper comparison. A brief description for the most comparable
deposits follows.
Table 6. Data on selected Swedish nickel deposits. Note that all data except Blackstone data are historical
and not NI 43-101 compliant. NiS is the content of Nickel in 100 % sulphides.
Deposit name
Kukasjärvi
Type
Ultramafic sill
Gabbroid
Fiskelträsk
Metric tonnes
border
zone
Notträsk
intrusion
Storbodsund
Gabbroid
funnel
Reference
Ni
Cu
Kton
% Ni
% Co
% Cu
%S
% NiS
10 400
9 800
1 900
0.4
0.02
0.4
8.0
2
Boliden mineral
11 000
11 000
3 000
0.2
0.02
0.2
3.2
2.4
Hansson 1985
0.2-
0.02-
3.2-
2.9-
0.5/1.0
0.08/0.11
0.13/0.4
3.8/30
5.1/1.2
Arvantidis 1982
2.3
0.09
0.6
21.0
4.2
Grip 1961
of
granodiorite pluton
Layered,
Grade
shaped,
1 400
1 000
Blackstone report, may
Lainijaur
Mafic dyke
8 600
4 200
Älgliden
Differentiated mafic dyke
26 000
Bastutjärn
Gabbroic intrusion
Ultramafic
Lappvattnet
lenses
lenses
3.6
2009/Grip 1961
6.15
1.2
Boliden Mineral
0.12
7.2
0.8
Boliden Mineral
1.33
0.09
0.66
90 000
0.20
0.03
0.69
4 800
3 600
0.16
10 400
2 200
and
fragmental ore in paragneiss
Ultramafic
645
Blackstone report, may
1139
0.91
0.02
0.19
4.4
8.9
2009/Grip 1961
1.4
0.015
0.21
5.1
10.2
Nilsson 1985
0.35
0.01
0.04
0.7-4.8
and
Mjövattnet
fragmental ore in paragneiss
3 000
450
Rörmyrberget
Differentiated multiple sill
22 100
2 500
Blackstone report, may
6370
2009/Grip 1961
7.4.1 Älgliden
Älgliden is a mafic dyke crosscutting the G1-phase of the Jörn granitoid complex, SW of Jörn
in the eastern part of the Skellefte District. The length of this dike is 2.7 km and the width is
20-100 m and it is oriented subvertical in a NE trending direction. Rock composition in the
dike is mainly diorite, gabbro and ultramafic rocks. Mineralization occurs as disseminated
and massive including pyrrhotite, chalcopyrite, minor pentlandite and sporadically pyrite
(Wilson et al., 1987).
36
7.4.2 Näsberg
The Näsberg mafic instrusion is located within the GI phase of the Jörn granitoid complex,
comprising two different generations of gabbroic rocks (Filen, 2001). Later studies have
resulted in discoveries of three zones in the intrusion divided into a lower, a main and an
upper zone. The lower and upper zone is poorly exposed and hard to define, but is generally
consisting of gabbronorite, hornblende gabbro and quartz-bearing gabbro. The main zone is
consisting of cumulates and well developed layering in a olivine gabbronorite. Pyrrhotite and
magnetite dikes are found within the younger fault controlled gabbro. Iron was earlier
mined here in a very small scale (Årebäck, 2006).
7.4.3 Lainijaur
Lainijaur is situated in the NW area of the Skellefte District and 50 km NW of the Bastutjärn
project. The deposit is the only one mined in this area, with an accumulated production of
100 526 tonnes of ore averaging 2.20% Ni, 0.93% Cu and 0.01% Co during the years 1941-45
(Grip, 1961). Host rock is consisting of gabbroic and diorite rocks, emplaced by several
injection pulses of magma. The mineralization consists of two sulphide layers of mainly
pyrrhotite, occurring at the base of the gabbro and close to the contact to the
metasedimentary country rock. At the deposit also a nickel-arsenic mineralization occurs as
veins and fissure fillings (Martinsson, 1996).
7.4.4 Deposits within the Nickel Belt, Västerbotten
The Nickel belt is a larger area with several known occurrences located south of the Skellefte
District in the central of Västerbotten. All of them are associated with ultramafic rocks.
Major rock types are metamorphosed dunites, peridotites and pyroxenites. Ultramafic
intrusions located within the Nickel belt are in general small and the largest known deposit is
at the Rörmyrberget intrusion with a size of 1.7 km x 320 m. Host to that intrusions are
gneisses and migmatites, often rich in graphite and pyrrhotite. Origin of the graphite is
interpreted to be sapropelic, because if its high values of vanadium and molybdenum. Values
at the graphite-rich gneisses at Lappvattnet range from 300-550 ppm V and 10-20 ppm Mo,
which can be considered as elevated. Graphite is also found within the ultramafic rocks as
isolated inclusions and aggregates, giving indication of possible contamination of the
gneisses to the magma (Nilsson, 1985).
37
Table 7. Elements in 100 % sulphides, n = 108 ore samples. % MeS = percentage of metal in 100 % sulphide
phase.
Bastutjärn
% NiS
% CuS
% CoS
1.08
1.02
0.25
7.4.5 Bastutjärn compared to similar deposits
Most obvious similarities are found to the Lainijaur deposit not only because its spatial
presence, where multiple gabbroic injections intrude a metasedimentary unit. The behavior
of the mineralization shows similarities, it consists of two layers with a larger area of
disseminated type of mineralization and it is emplaced in vicinity to the contry rock. Also
here fragments and xenoliths of sedimentary origin are found in the host rock. A feature at
Lainijaur that is not shared with Bastutjärn is the nickel-arsenic mineralization. Genetic
model for the magmatic Lainijaur deposit is mantle-derived sulphur, based on isotopic data
by Martinsson (1996). However there is a possibility that pyrrhotite-bearing schists have
contaminated the magma, schist with close to zero sulphur isotopic composition. In this case
the two deposits would be similar even in the forming aspect. Grades at Lainijaur is much
higher compared to Bastutjärn, both in total Ni content and Ni in 100 % sulphides (Table 6
and 7). Bastutjärn on the other hand shows a much higher Ni:Co ratio (approx. 0.3 compared
to approx 0.07), in fact highest among all the major occurrences in this area.
Other deposits that are possible to compare to Bastutjärn are the deposits along the
Västerbotten Nickel belt, e.g. Lappvattnet and Rörmyrberget deposits. Those deposits are of
ultramafic intrusive type compared to the gabbroic associated mineralization at Bastutjärn,
but there may be similarities in the formation process. Deposits along this belt are situated
within intrusions intruding gneisses and migmatites, often rich in graphite and pyrrhotite,
similar to Bastutjärn. At Bastutjärn these sedimentary units have given an enrichment of
molybdenum, which is found in elevated grades as well in the country rocks for these
deposits. Since the gneisses and migmatites are rich in pyrrhotite, this is a possible sulphur
source for the formation of an economic interesting deposit.
The Älgliden deposit shows only a few similarities, mainly in rock and ore mineral
composition. Although the grades for nickel is at the same magnitude, even if the copper
grades are higher at Älgliden. Mineral assemblage is similar in the mineralized zones.
38
The mineralization at Bastutjärn is not easy to completely fit into any other deposit of same
type. Many differences are found when comparison is undertaken. A deposit that shows
most similarities is the Lainijaur deposit, which in a way can be used as a tool to better
understand the Bastutjärn mineralization. It must be noted that the extent of data from
Bastutjärn is much lesser in many of the other deposits, so more information may be needed
to do a complete comparison.
7.5 Ore potential
Since the number of drill holes intersecting the mineralization is only six, it has not been
possible to calculate an accurate volume of ore. Historically it has been done a rough
estimation of the potential in the area (Table 8). In this case a two layered mineralization
dipping slightly to the north was used as the model. In a global scale the grades and tonnage
are far away from a major deposit (Fig. 18) and would be plotted in the lower left corner in
the Figure 18. Noted from the figure is that stratabound Ni-Cu deposits often are of low
grade character. Favorable conditions for the Bastutjärn mineralization is the high grades of
cobalt and from a mining point of view the near surface localization.
Table 8. Historical estimation of the mineralization at Bastutjärn. “Ore” zone includes the upper Lens 1 and
lower Lens 2 plus marginal ore between these lenses. Internal Report Boliden Mineral 1974.
Mton
Ni %
Cu %
S%
Lens 1
0.51
0.21
0.15
9.9
Lens 2
0.41
0.29
0.22
13.5
”Ore” zone 2.16
0.16
0.12
7.2
It must be noted that there is a big potential to discover more mineralization at Bastutjärn.
The mineralization is not limited in any direction and further drilling is needed to define the
borders. On a more regional scale there is potential to find more Ni-Cu mineralization hosted
in other parts of the Bastutjärn gabbroic intrusion. The targeted area must be to investigate
the near contact zone of gabbro and metasediments, since they are interpreted to be a
crucial key in the ore formation and also the area where mineralization is deposited at
Bastutjärn.
39
Fig. 18. Plot of Ni grade (%) vs resource of Ni ore (Mton) in world class deposits divided into different deposit
types. After Jaireth et al. (2005).
8 Conclusion
The Bastutjärn gabbroic intrusion consists of rocks ranging from gabbroic to dioritic
composition, with only minor amounts of ultramafic rocks. Based on nomenclature set up by
IUGS a majority of the gabbroic rocks are gabbronorites, containing almost equal amounts of
clino- and orthopyroxene. Optical and geochemical studies suggest that the rocks here are
more or less affected by assimilation of the country rock, consisting of graphitic- and
pyrrhotitic schist. A process that have resulted in abundant xenoliths and fragment of
sedimentary units within the gabbroic body.
The mineralization at Bastutjärn is consisting of multiple layers of semi-massive sulphides,
mainly pyrrhotite with minor chalcopyrite and pentlandite. Layers are interpreted to form
two zones where the mineralization is concentrated. Between the high grade zones the
mineralization is disseminated with droplets of pyrrhotite with pentlandite and chalcopyrite
40
inclusions. Molybdenum are found in the mineralization and grades up to 52 ppm are found
in one section (1.8 meters in BAB7)
Formation of the sulphide mineralization is suggested to be from assimilation and extraction
of sulphur from country rock. This is based on the abundance of xenoliths and fragments of
sediment in the mineralized zone but also presence of graphite in the mineralization. The
semi-massive parts consist of two different types of mineralization, one of more pure
magmatic sulphides, where pyrrhotite is less fractured and contaminated with graphite, and
the second type where the sulphides are fine-grained and mixed with graphite that gives the
mineralization a polluted appearance.
9 Future work
One of the aims for this study was to get an better understanding of the geology of the
Bastutjärn intrusion. A major question discussed in the thesis is the source of the sulphur. At
this moment the sulphur is believed to be assimilated from crustal rocks. The only way to
confirm this is to do a sulphur isotopic study.
Since the mineralization is very rich in cobalt, it would be interesting to do microprobe
analyzes on mineralized samples and especially on pentlandite grains to confirm that these
are cobalt bearing.
41
10 Acknowledgements
First I would like to thank the staff at Boliden Mineral exploration department for given me
the chance to work with this project. A special thank to my supervisor at Boliden Holger
Paulick. Anders Gren is thanked for the help with drill core logging, sharing geochemistry
data and help with digital data. At Luleå University of Technology I would like to thank my
supervisor Olof Martinsson. Last but not least I am very grateful to Lisa Andersson, who has
supported and motivated me in the everyday work and revised the material through the
work.
42
References
Årsrapport 1973 Boliden Mineral AB, Internal report.
Årsrapport 1974 Boliden Mineral AB, Internal report.
Arvanitidis, N., 1982 The geochemistry and pentrogenesis of the Notträsk mafic intrusion,
northern Sweden. Doctoral thesis. Meddelande från Stockholm Universitets Geologiska
Institution N:r 253
Barnes, S.J., Lightfoot, P.C., 2005 Formation of magmatich nickel-sulfide ore deposits and
processes affecting their copper and platinum-group element contents. In Hedenquist JW,
Thompson JFH, Goldfarb RJ and Ricards JP (eds.) Economic Geology 100 th Anniversary
Volume, p. 179-213.
Bergström, U., Antal Lundin, I., Winnes, K., Weihed, P., 2003 Berggrundskartan 23J Norsjö SV
skala 1:50 000. Sveriges Geologiska Undersökningar Ai 175.
Bergström, U., Antal Lundin, I., Winnes, K., Weihed, P., 2003 Berggrundskartan 23J Norsjö SO
skala 1:50 000. Sveriges Geologiska Undersökningar Ai 177.
Blackstone Investors report Swedish Projects 2009.
Cox, K.G., Bell, J.D., Pankhurst, R.J., 1979 The interpretation of igneous rocks. London:
George Allen & Unwin. 450 pp
DeWaal, S.A., Xu, Z., Li, C., Mouri, H., 2004 Emplacement of viscous mushes in the Jinchuan
utramafic intrusion, western China. The Canadian Mineralogist 42:371-392
Filén, B., Gerdin, P., Lundmark, L-G., Renberg, A., 1988 PGE – 1987 etapp II. Sveriges
Geologiska AB, PRAP 88005, 143 pp.
Gaal, G., and Gorbatchev, R., 1987. An outline of the Precambrian Evolution of the Baltic
Shield.
Precambrian Research, 35, pp 15-52.
Grip, E., 1961 Geology of the Nickel deposit at Lainijaur in Northern Sweden. Sveriges
geologiska undersökningar. Årsbok 55 (1961) n:o 1
Hansson, K.E., 1985, Korpilomboloområet – Gabbroinventering. LKAB Prospektering
Slutrapport Ki_85-23.
Irvine, T.N., and Baragar, W.R.A., 1971, A guide to the chemical classification of the common
volcanic rocks: Canadian Journal of Earth Sciences, v. 8, p. 523-548.
43
Jaireth, S., Hoatson, D., Jaques, L., Huleatt, M., Ratajkoski, M., 2005 Nickel sulphide
metallogenic provinces of Australia: resources and potential. AusGeo News September
2005 Issue No. 79.
Lahtinen, R., Korja, A., Nironen, M., 2005 Palaeoproterozoic tectonic evolution of the
fennoscandian shield. In: Lehtinen, M., Nurmi, P. and Rämö, O.T. (Eds.): Precambrian
Geology of Finland – Key to the Evolution of the Fennoscandian Shield. Elsevier B.V.,
Amsterdam, pp. 481-532.
Li, C., Lightfoot, P.C., Amelin, Y., Naldrett, A.J., 2000 Contrasting petrological and
geochemical relationship in the Voisey´s Bay and Mushuau intrusions, Labrador, Canada:
implication for ore genesis. Economic Geology 88:771-799.
Maier, W.D., Grooves, D.I., 2011 Temporal and spatial control on the formation of magmatic
PGE and Ni-Cu deposits. Miner Deposita 46:841-857.
Martinsson, E,. 1996 Geochemistry and petrogenesis of the Palaeoproterozoic Lainijaur
intrusion. Geologiska Föreningens i Stockholm Förhandlingar 118:97-109.
Middlemost, E.A.K., 1985 Magmas and magmatic rocks: An introduction to igneous
petrology. London, UK, Longman pp. 266.
Naldrett, A.J., 2004 Magmatic sulfide deposits. Springer, Heidelberg, pp. 728.
Naldrett, A.J., 2010 Secular variation of magmatic sulfide deposits and their source magmas.
Econ Geol 105:669-688.
Nilsson, G., 1985 Nickel-Copper Deposits in Sweden. Geological Survey of Finland Bulletin
333:313-362.
Nironen, M., 1997 The Svecofennian Orogen: a tectonic model. Precambrian Research 86:
21-44.
Rickard, D., Zweifel, H., Donnelly, T.H., 1979 Sulfur Isotope Systematics in the Åsen PyriteBarite Deposits, Skellefte District, Sweden. Economic Geology 74, 1060-1068.
Seat, Z., Beresford, S., Gruguric, B., Waugh, R., Hronsky, J., 2007 Architecture and
emplacement of the Nebo-Babel gabbronorite-hosted magmatic Ni-Cu-PGE sulphide deposit,
West Musgrave, Western Autralia. Miner Deposita 42:551-581.
Skyttä, P., Hermansson, T., Andersson, J., Whitehouse, M., Weihed, P., 2011 New zircon data
supporting models of short-lived igneous activity at 1.89 Ga in the western Skellefte District, central
Fennoscandian Shield. Solid earth 2011:2 pp 205-217.
Streckeisen, A., 1976 To each plutonic rock its proper name. Earth science reviews 12, 1-33.
44
Årebäck, H., Barrett, T.J., Abrahamsson, S., Fagerström, P., 2005 The Paleoproterozoic
Kristineberg VMS deposit, Skellefte District, northern Sweden, Part 1: geology. Miner
Deposita 40:351-367.
Årebäck, H., Wasström, A., Mattson, B., 2006 Petrology and Geochemistry of the Näsberget
layered intrusion. Skellefte District, Northern Sweden. Geological Nordic winter meeting,
Oulu Finland.
Weihed, P., Bergman, J., Bergström, U., 1992 Metallogeny and tectonic evolution of the early
Proterozoic Skellefte District, Northern Sweden. Precambrian Res., 58:143-167.
Wilson, M.R., Sehlstedt, S., Claesson, L-Å, Smellie, J.A.T., Aftalion, M., Hamilton, P.J. & Fallick,
A.E., 1987: Jörn, an Early Proterozoic intrusive complex in a volcanic-arc environment, north
Sweden. Precambrian Research 36, 201-225.
Sweden. In: G. Gaul and K. Schulz (Editors), Precambrian Meta
45
Appendices
Appendix 1
Graphic Drill core logs
Legend:
46
47
48
49
50
51
52
Appendix 2
Raw data whole rock geochemistry
ME-ICP06 ME-ICP06 ME-ICP06 ME-ICP06
SAMPLE
Typ DESCRIPTION
SiO2
Al2O3
Fe2O3
CaO
Code
From\N
To\E
%
%
%
%
BAB9
60.20
62.25
Dh
1100001
40.2
12.8
24.8
4.33
BAB9
62.25
64.95
Dh
1100002
45.1
13.65
21.8
5.85
BAB9
64.95
67.40
Dh
1100003
38.2
11.55
27.4
5.08
BAB9
90.00
92.85
Dh
1100004
49.9
16.05
14.6
6.1
BAB9
99.15
102.25
Dh
1100005
40.4
12.5
25.1
5.66
BAB9
102.25
103.65
Dh
1100006
52.6
16.1
12.9
7.09
BAB9
103.65
108.62
Dh
1100007
51.5
14.95
12.5
6.94
BAB10
64.80
67.60
Dh
1100013
53.3
17.85
10.3
7.8
86.80
BAB10
83.85
Dh
1100017
51.7
16.8
10.8
8.63
20111520
7212933
1676947 Outcrop
20111520
52.9
16.05
10.9
8.12
20111521
7210705
1678207 Outcrop
20111521
52
16.25
8.56
8.44
20111522
7211521
1678469 Outcrop
20111522
52.6
17.4
6.26
10.85
20111523
7212215
1675574 Outcrop
20111523
49.9
13.2
12.3
12.55
20111524
7212257
1676219 Outcrop
20111524
50.1
14.9
11.9
8.65
20111525
7212750
1676681 Outcrop
20111525
45.3
10.3
18.4
7.12
20111526
7212768
1677234 Outcrop
20111526
51.2
15.95
13.3
8.49
20111527
7212764
1677236 Outcrop
20111527
52.1
15.35
14.05
8.97
20111528
7212929
1676942 Outcrop
20111528
52.5
17.05
9.48
8.64
7
37.55
38.00
Dh
LK20121001
46.1
15.45
16.45
8
7
51.15
51.55
Dh
LK20121002
47.4
14.95
14.75
8.17
7
113.15
113.5
Dh
LK29121003
48.1
8.82
11.4
6.28
8
103.95
104.30
Dh
LK20121004
61.2
18.6
5.27
4.38
8
69.60
70.05
Dh
LK20121005
50.9
16.6
12.5
7.04
4
53.35
53.60
Dh
LK20121006
33.4
9.24
32.8
5.65
4
22.20
22.65
Dh
LK20121007
48.9
13.45
18.7
4.94
4
25.60
25.90
Dh
LK20121008
52.2
15.9
9.12
8.81
4
35.10
36.45
Dh
LK20121009
42.3
12.2
25.3
6.2
4
44.60
46.45
Dh
LK20121010
54.4
17.3
10.55
7.29
4
58.50
59.05
Dh
LK20121011
49.7
15.3
10.95
8.66
4
68.20
68.60
Dh
LK20121012
50.6
15.65
11.7
7.57
4
73.20
73.60
Dh
LK20121013
44.8
16.1
13.7
7.3
4
81.30
81.65
Dh
LK20121014
49.2
13.5
10.3
12.45
4
90.75
91.15
Dh
LK20121015
40.9
13.75
20.9
6.81
4
100.70
101.05
Dh
LK20121016
48.9
15.6
11.6
7.72
4
126.65
127.15
Dh
LK20121017
46.1
14.4
13.7
6.87
4
137.60
138.00
Dh
LK20121018
48.6
9.79
9.61
6.05
53
MEMEMEMEMEMEMEMEMEICP06
ICP06
ICP06
ICP06
ICP06
ICP06
ICP06
ICP06
ICP06
C-IR07
MgO
Na2O
K2O
Cr2O3
TiO2
MnO
P2O5
SrO
BaO
C
%
%
%
%
%
%
%
%
%
%
5.25
2.66
1.05
0.06
0.79
0.11
0.1
0.03
0.04
4.4
7.65
1.81
0.51
0.03
0.57
0.12
0.12
0.04
0.02
0.59
6.17
1.58
0.43
0.03
0.49
0.11
0.12
0.03
0.02
0.58
7.87
2.4
0.94
0.05
0.31
0.09
0.05
0.05
0.03
0.58
7.2
3.98
4.15
7.36
7.36
7.87
9.28
8.22
6.73
9.57
9
6.16
5.34
7.43
7.28
7.55
19.25
1.83
7.57
4.98
6.72
5.91
5.7
6.48
6.31
6.11
6.97
7
7.23
6.26
8.55
16.35
1.73
3.35
2.92
2.77
2.81
2.49
2.37
2.5
2.58
2.2
1.48
2.7
2.95
2.65
2.02
2.18
0.23
3.82
2.49
1.45
2.74
2.48
2.04
2.64
2.34
2.62
2.08
1.8
1.94
2.59
2
0.32
0.75
1.43
1.47
0.63
0.81
0.73
0.39
0.44
0.26
0.41
0.31
0.5
0.57
0.66
0.71
0.91
2.36
3.72
0.91
0.44
0.52
0.73
0.43
0.94
0.58
1.02
0.69
0.4
0.61
0.82
0.92
1.9
0.04
0.03
0.02
0.04
0.03
0.03
0.08
0.07
0.03
0.03
0.04
0.01
0.02
0.04
0.03
0.03
0.32
0.04
0.05
0.07
0.05
0.04
0.04
0.03
0.03
0.03
0.02
0.08
0.03
0.04
0.03
0.29
0.51
2.07
1.75
0.53
0.93
0.75
0.45
0.45
0.97
0.94
5.66
1.42
1.91
0.66
0.71
1.08
0.77
1.08
0.4
0.27
1.15
1.38
0.8
0.71
0.98
1.42
0.96
0.79
0.63
1.11
0.87
0.44
54
0.12
0.15
0.12
0.13
0.14
0.16
0.13
0.1
0.2
0.15
0.2
0.18
0.19
0.15
0.13
0.15
0.18
0.06
0.09
0.09
0.15
0.11
0.12
0.12
0.11
0.14
0.08
0.14
0.11
0.12
0.12
0.15
0.16
0.68
0.55
0.12
0.22
0.13
0.07
0.1
0.11
0.25
0.14
0.26
0.41
0.13
0.23
0.35
0.2
0.28
0.08
0.19
0.08
0.36
0.13
0.13
0.25
0.5
0.33
0.2
0.22
0.43
0.25
0.16
0.03
0.06
0.05
0.05
0.05
0.04
0.05
0.05
0.06
0.05
0.02
0.04
0.04
0.04
0.05
0.05
0.01
0.06
0.06
0.03
0.04
0.05
0.04
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.02
0.04
0.12
0.11
0.03
0.04
0.03
0.02
0.02
0.01
0.03
0.02
0.04
0.06
0.03
0.04
0.05
0.05
0.32
0.04
0.01
0.01
0.02
0.02
0.04
0.03
0.09
0.04
0.02
0.03
0.05
0.04
0.05
0.25
0.51
0.54
0.6
0.17
0.15
0.13
0.22
0.27
0.11
0.49
0.05
0.05
0.13
0.16
0.17
0.08
0.15
0.34
5.67
1.07
0.07
0.63
0.17
0.56
0.26
0.15
0.34
0.09
0.11
0.12
0.11
S-IR08 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81
S
Ba
Ce
Cr
Cs
Dy
Er
Eu
Ga
Gd
Hf
%
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
7.32
353
45.2
410
1.11
2.8
1.88
1.54
17.8
3.28
3.5
4.81
156
21.9
240
0.94
1.97
1.17
1.01
12.7
2.17
1.5
9.16
169
19.6
230
1.19
1.65
1
0.85
10.9
1.7
1.1
3.04
265
28.5
350
1.46
1.66
1.2
1.18
15.8
2.03
1.9
7.6
300
22.4
270
1.24
1.84
1.14
1.04
11
1.96
2.3
0.66
1015
110.5
200
0.51
6.4
3.61
2.53
22.9
10.1
8.6
0.76
910
90.8
150
1.08
5.79
3.24
2.13
21.2
8.27
7.1
0.83
236
23.1
290
0.6
1.94
1.19
1.33
18.5
2.13
1.2
0.23
327
38.3
230
0.56
3.32
1.97
1.5
17.3
4.22
2.4
0.3
249
24.9
220
0.78
2.64
1.62
1.5
17.6
2.92
2
<0.01
198
15.4
490
0.58
1.28
0.81
1.33
14.9
1.5
1.2
<0.01
198
18
460
0.33
1.5
0.84
1.35
15.5
1.78
1
2.31
65.8
13.2
220
0.31
3.2
2.07
0.95
15.8
3.35
1.3
0.18
242
29.4
210
0.38
2.64
1.49
1.71
16
3.42
1.3
0.16
161.5
19.4
300
0.37
2.16
1.31
1.29
15.5
2.43
1.7
0.02
333
40.8
70
0.4
5.05
3.14
1.92
20.2
5.72
3
0.13
457
62.9
120
0.12
6.45
3.96
2.25
22.4
7.54
4.4
0.08
232
21.2
250
0.71
2.33
1.48
1.54
18.1
2.61
1.5
2.99
316
38.8
240
0.53
2.55
1.41
1.38
17.9
3.21
2.2
2.21
395
48.6
240
0.51
3.41
1.82
1.5
18.4
4.23
4.7
0.18
366
12.6
2420
7.36
2.38
1.41
0.73
13.9
2.62
1.1
0.08
3020
96.3
270
3.45
3.96
2.28
2.26
26.4
5.28
21.2
2.4
410
22.6
340
1.28
1.43
0.77
1.26
17.5
1.71
1
11.9
118
21.5
470
0.45
1.81
1.09
1.22
11.7
2.07
0.5
2.63
104
18.6
380
0.29
2.44
1.7
1.29
19.8
2.32
1.8
0.15
204
32.2
290
1.56
3.83
1.99
1.37
18
4.53
1.2
7.2
218
22.9
300
0.5
1.98
1.1
1.11
14.5
2.23
2
0.39
314
29.5
210
1.35
2.29
1.38
1.34
18.8
2.62
2.9
1.14
266
35.5
260
0.78
3.25
1.8
1.6
17.2
3.67
1.5
0.69
883
66
240
0.78
4.54
2.53
2.17
20.1
5.69
6.1
1.85
369
45.9
150
1.44
2.75
1.6
1.51
16.9
3.58
3.3
0.79
225
28.8
610
0.66
3.4
2.09
1.23
16.3
3.58
1.9
5.46
299
34.2
240
0.8
2.18
1.26
1.24
14.5
2.57
1.9
1.08
500
58.4
270
0.76
3.61
2.06
1.85
18.9
4.47
3.3
2
453
47.7
270
1.64
3.02
1.73
1.49
16.7
3.66
2.9
0.21
472
16.9
1990
4.97
2.06
1.25
0.54
11.2
2.34
1.2
55
ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81
Ho
La
Lu
Nb
Nd
Pr
Rb
Sm
Sn
Sr
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
0.62
27.4
0.32
6
20.5
5.54
29.7
3.34
1
322
0.41
11.9
0.18
3.8
10.9
2.86
14.6
2
1
307
0.34
12
0.14
2.8
9.2
2.51
13.2
1.71
1
297
0.38
17.3
0.2
2.1
11.9
3.41
32.4
1.89
1
371
0.4
13.5
0.14
3.1
11.2
2.95
21.8
1.96
1
306
1.27
56
0.48
17.8
56.4
14.9
21.2
9.72
<1
471
1.15
44.8
0.42
13.9
46
11.95
28.6
8.26
<1
388
0.4
13.3
0.19
2.5
11.1
2.94
14.2
2.09
<1
366
0.67
19.4
0.27
5.1
20
5.01
19.2
3.79
1
365
0.61
12.5
0.3
4.3
13.2
3.26
18.3
2.86
<1
294
0.3
8.1
0.16
2
7.6
1.92
7.5
1.57
<1
381
0.34
9.2
0.15
2.2
9.1
2.27
8.8
1.98
<1
399
0.77
5.5
0.38
2.9
9.2
2
4.4
2.69
<1
414
0.58
14.6
0.26
4.2
16.2
3.94
9.6
3.43
<1
362
0.52
9.5
0.25
11.3
10.4
2.57
7
2.32
<1
250
1.16
19.6
0.54
7.7
23.1
5.52
8.7
5.32
<1
303
1.48
30.1
0.65
12.2
34.3
8.36
4.7
7.5
<1
318
0.56
10.5
0.28
3.5
11.1
2.74
16.2
2.48
<1
311
0.49
18.6
0.22
6.2
19.5
4.75
23.2
3.93
2
426
0.64
23.1
0.26
7.7
24.9
5.98
27.5
4.6
1
423
0.46
4.5
0.2
3.8
9.8
2
125
2.48
<1
84.9
0.76
51.5
0.41
20.7
43.4
10.8
105
6.94
2
474
0.26
12.5
0.1
3.2
10.8
2.59
21.9
2.03
1
512
0.37
11.5
0.17
1.4
11.7
2.64
13.3
2.26
<1
231
0.55
9.9
0.31
4.7
10
2.24
10
2.2
<1
258
0.73
14.8
0.23
5.9
19.8
4.21
24.1
4.45
1
387
0.39
11.5
0.17
5.3
12.2
2.83
9.9
2.56
<1
304
0.45
16.2
0.21
5.6
14.7
3.49
26.6
2.79
1
372
0.66
16.9
0.25
6
19.2
4.69
14
4.14
1
439
0.91
31.9
0.35
14.9
33.8
8.4
26.6
6.59
<1
451
0.55
22.6
0.22
5.7
21.9
5.54
23.7
4.12
<1
457
0.7
13.8
0.29
4.4
15.3
3.7
12.2
3.43
<1
446
0.43
17.6
0.17
4.5
16.2
4.2
19
3.25
<1
427
0.73
29.3
0.29
8.8
27.7
7.18
25.7
5.26
1
456
0.6
23.9
0.25
7.1
22.8
5.92
37.4
4.31
1
411
0.44
7.7
0.18
2
9.8
2.28
120.5
2.28
<1
135.5
56
ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81 ME-MS81
Ta
Tb
Th
Tl
Tm
U
V
W
Y
Yb
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
ppm
Ppm
0.5
0.49
3.24
<0.5
0.28
0.97
356
1
15.5
1.95
0.3
0.32
1.26
<0.5
0.18
1
95
<1
10.2
1.17
0.2
0.3
0.35
<0.5
0.14
0.58
93
1
8.9
0.92
0.2
0.3
2.05
<0.5
0.18
1.08
118
<1
9.7
1.24
0.3
0.33
1.09
<0.5
0.15
0.85
83
1
9.7
1.02
1
1.26
1.66
<0.5
0.47
0.96
141
<1
31.8
3.13
0.8
1.11
1.18
<0.5
0.42
0.7
122
<1
28.6
2.73
0.2
0.33
1.08
<0.5
0.17
0.64
171
<1
10.2
1.16
0.3
0.59
1.66
<0.5
0.26
0.56
128
<1
17
1.69
0.3
0.5
1.36
<0.5
0.28
0.56
207
1
16.1
1.59
0.1
0.25
0.64
<0.5
0.13
0.22
156
1
7.8
0.79
0.1
0.28
0.69
<0.5
0.14
0.22
218
1
8.7
0.79
0.3
0.59
0.24
<0.5
0.35
0.23
327
1
20.1
2
0.3
0.52
1.18
<0.5
0.24
0.59
131
1
14.9
1.36
0.9
0.42
0.83
<0.5
0.22
0.39
556
1
13.1
1.31
0.5
0.97
1.58
<0.5
0.52
0.7
124
1
31.1
2.9
0.7
1.29
0.96
<0.5
0.66
0.48
163
1
38.6
3.62
0.2
0.44
1.06
<0.5
0.25
0.41
206
1
14.6
1.46
0.1
0.45
1.47
<0.5
0.21
0.9
113
1
14.4
1.38
0.2
0.56
1.69
<0.5
0.27
0.92
146
1
18.4
1.71
0.2
0.39
0.21
1.5
0.2
0.29
209
<1
12.7
1.39
1.2
0.67
9.47
0.6
0.35
5.96
65
1
20.8
2.49
0.2
0.24
2.14
<0.5
0.11
1.22
61
1
7.3
0.77
0.1
0.29
0.6
<0.5
0.16
0.47
314
<1
10.5
1.14
0.3
0.38
1.14
<0.5
0.25
0.36
420
1
14.3
2.02
0.4
0.65
2.08
<0.5
0.26
1.42
147
1
19.4
1.75
0.3
0.32
0.94
<0.5
0.17
0.69
113
<1
10.8
1.13
0.4
0.35
2.12
<0.5
0.19
1.56
141
1
11.9
1.42
0.4
0.59
1.1
<0.5
0.26
0.78
186
<1
18.1
1.7
0.8
0.83
1.9
<0.5
0.36
1.21
151
1
25.3
2.36
0.3
0.54
1.65
<0.5
0.21
0.92
119
<1
16.1
1.49
0.3
0.58
1.03
<0.5
0.3
0.66
436
<1
19.8
1.93
0.3
0.41
1.38
<0.5
0.17
0.74
119
1
13
1.23
0.5
0.67
1.8
<0.5
0.3
0.83
166
1
20.7
1.93
0.4
0.55
2.28
<0.5
0.24
1.09
136
1
17.7
1.65
0.1
0.37
1.73
1.3
0.18
1.19
149
<1
12.3
1.23
57
ME-MS81 ME-MS42 ME-MS42 ME-MS42 ME-MS42 ME-MS42 ME-MS42 OA-GRA05 TOT-ICP06 MEZr
As
Bi
Hg
Sb
Se
Te
LOI
Total 4ACD81 Ag
ppm
ppm
ppm
ppm
ppm
ppm
ppm
%
%
ppm
128
64.2
0.94
0.014
0.13
15.8
0.41
6.97
99.2
2.6
59
45.9
0.7
0.014
0.09
9.6
0.33
2.2
99.5
2.2
28
60.8
1.72
0.016
0.1
16.5
0.5
3.9
95.1
2
64
22.2
0.63
0.011
0.12
5.2
0.2
1.8
100
1.9
79
42.6
0.71
0.013
0.11
12
0.22
3.2
97.4
1.6
399
1.9
0.04
0.008
<0.05
1.9
0.03
0.5
101
0.7
332
1.9
0.09
0.012
0.05
1.8
0.01
2.49
99.5
1.9
46
4.4
0.05
0.009
<0.05
1.9
0.04
0.8
101.5
0.6
95
1.6
0.04
0.009
<0.05
0.7
0.01
0.4
100.5
0.8
78
7.7
0.03
<0.005
0.1
1.1
0.02
1.09
101.5
<0.5
49
2.5
0.05
0.005
<0.05
0.3
0.01
1.98
100
<0.5
37
1.4
0.01
<0.005
0.16
0.3
<0.01
2.1
101
<0.5
38
119
0.06
0.008
0.19
1.8
0.11
2.28
101
<0.5
48
2.9
0.03
0.006
0.06
0.7
0.01
0.8
100
<0.5
65
8.4
0.09
0.005
0.08
1.8
0.04
2.29
100.5
<0.5
115
2.9
0.01
<0.005
0.08
0.5
<0.01
0.4
100.5
<0.5
185
0.6
0.01
0.005
<0.05
0.7
<0.01
-0.4
101.5
<0.5
56
2.8
0.02
0.007
0.06
0.7
<0.01
0.6
100
<0.5
94
53.2
0.71
0.041
1.35
4.5
0.21
1.27
98.47
0.6
191
22.4
0.32
0.012
0.34
2.8
0.09
0.92
98.54
0.8
35
26.7
0.04
<0.005
0.09
0.6
0.01
1.95
99.92
<0.5
1010
6.7
0.03
0.007
0.31
0.9
0.01
1.04
101.7
0.5
37
9
0.24
0.005
0.13
4.6
0.19
1.82
100.55
0.6
17
25.1
2.15
0.106
0.57
26.8
1.31
10.4
99.02
2.1
66
54.7
0.26
0.01
0.08
5.6
0.21
1.76
99.21
0.8
39
4.3
0.07
0.018
0.12
0.7
0.01
1.24
98.35
<0.5
75
25.7
0.85
0.016
0.15
9.8
0.24
3.14
98.46
1.6
111
6.2
0.11
0.011
0.17
1.2
0.07
0.68
101.36
<0.5
54
18.4
0.23
<0.005
0.09
2
0.06
1.43
96.72
0.5
275
7.5
0.12
0.005
0.07
1.7
0.04
1.22
98.72
<0.5
149
11.5
0.27
0.008
0.08
3
0.08
4.84
97.96
0.6
74
85.8
0.15
0.005
0.08
1.5
0.06
1.17
97.1
<0.5
76
38.1
1.05
0.011
0.2
9.5
0.43
2.26
95.47
2.1
140
6.3
0.21
<0.005
0.05
2.1
0.05
0.77
96.06
<0.5
121
18.5
0.31
0.006
0.12
3.6
0.12
1.61
95.51
0.6
40
120
0.08
0.011
0.28
0.4
0.01
4.85
98.58
<0.5
58
Cd
Co
Cu
Mo
Ni
Pb
Zn
Au
ppm
ppm
Ppm
ppm
ppm
ppm
ppm
ppm
2.6
446
1330
27
1470
27
317
3.8
306
829
6
968
25
288
1.7
530
1375
13
1705
30
236
1.4
203
699
6
689
38
201
1.4
468
857
17
1520
36
234
<0.5
40
90
3
79
12
228
3.8
66
575
4
172
12
707
<0.5
40
85
4
68
9
175
<0.5
40
91
1
79
11
127
<0.5
31
25
<1
24
8
127
<0.005
<0.5
35
22
<1
44
6
94
<0.005
<0.5
24
7
<1
8
6
64
<0.005
<0.5
40
146
<1
97
3
111
0.01
<0.5
47
42
<1
77
6
136
<0.005
<0.5
18
79
6
16
3
154
<0.005
<0.5
32
17
<1
11
8
161
<0.005
<0.5
26
12
<1
1
10
175
<0.005
<0.5
25
17
<1
17
6
112
<0.005
2.3
197
572
4
618
48
208
1.2
156
419
3
403
39
164
<0.5
66
85
2
631
7
125
<0.5
11
18
6
10
29
97
0.6
171
495
5
611
34
104
1
648
269
45
2290
30
147
1
152
560
6
597
17
199
<0.5
42
18
3
50
14
139
2.8
420
988
19
1350
16
212
0.7
52
100
3
85
32
213
1.1
97
211
4
255
27
141
<0.5
72
137
4
149
18
157
0.6
148
320
5
362
16
129
0.8
77
166
3
223
15
115
2.8
354
1000
9
1070
67
162
0.6
97
167
4
227
22
138
0.9
153
350
4
551
34
143
<0.5
60
65
<1
539
5
111
59
Appendix 3
Recalculated whole rock geochemistry. Steps discribed under Method, chapter 3.5.1.
SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O Cr2O3 TiO2 MnO P2O5 SrO BaO
20111523
LK20121001
LK20121002
LK20121005
LK20121006
LK20121007
LK20121009
LK20121011
LK20121012
LK20121013
LK20121014
LK20121015
LK20121016
LK20121017
1100001
1100002
1100003
1100004
1100005
1100006
1100007
1100013
53.55 14.17
2.77 0.28
0.03 1.04 0.21
0.12 0.06 0.01
51.27 17.18
10.19
7.06 13.47 7.22
8.90 8.10
2.25 0.79
0.03 0.79 0.14
0.26 0.06 0.04
51.40 16.21
10.14
8.86 8.19
2.36 0.99
0.03 1.17 0.16
0.38 0.05 0.05
54.79 17.87
7.18
7.58 8.15
2.68 0.98
0.05 0.43 0.10
0.09 0.06 0.04
56.29 15.57
5.92
9.52 8.39
2.44 0.74
0.12 0.46 0.15
0.32 0.05 0.02
53.71 14.77
13.51
5.43 7.38
3.01 0.57
0.05 1.26 0.16
0.09 0.04 0.01
54.44 15.70
9.88
7.98 7.34
2.63 0.55
0.05 1.03 0.15
0.17 0.05 0.03
53.72 16.54
8.83
9.36 6.82
2.53 0.63
0.03 1.06 0.12
0.27 0.05 0.03
52.81 16.33
10.46
7.90 6.38
2.73 1.06
0.03 1.48 0.15
0.52 0.05 0.09
50.56 18.17
10.36
8.24 7.87
2.35 0.78
0.02 1.08 0.09
0.37 0.06 0.05
52.33 14.36
8.92 13.24 7.45
1.91 0.43
0.09 0.84 0.15
0.21 0.05 0.02
51.20 17.21
9.48
8.52 9.05
2.43 0.76
0.04 0.79 0.14
0.28 0.06 0.04
52.78 16.84
9.67
8.33 6.76
2.80 0.89
0.04 1.20 0.13
0.46 0.05 0.05
51.78 16.17
9.93
7.72 9.60
2.25 1.03
0.03 0.98 0.13
0.28 0.06 0.04
54.06 17.21
9.33
5.82 7.06
3.58 1.41
0.08 1.06 0.15
0.13 0.04 0.05
52.73 15.96
11.76
6.84 8.94
2.12 0.60
0.04 0.67 0.14
0.14 0.05 0.02
55.52 16.79
7.26
7.38 8.97
2.30 0.62
0.04 0.71 0.16
0.17 0.04 0.03
54.80 17.63
7.92
6.70 8.64
2.64 1.03
0.05 0.34 0.10
0.05 0.05 0.03
53.42 16.53
8.58
7.48 9.52
2.29 0.99
0.05 0.67 0.16
0.21 0.04 0.05
53.16 16.27
11.40
7.17 4.02
3.39 1.45
0.03 2.09 0.15
0.69 0.06 0.12
54.08 15.70
11.24
7.29 4.36
3.07 1.54
0.02 1.84 0.13
0.58 0.05 0.12
53.91 18.06
8.35
7.89 7.44
2.80 0.64
0.04 0.54 0.13
0.12 0.05 0.03
60
Appendix 4
CIPW normalization of recalculated samples. Calculation steps after Johannsen. 1931
Normative
Minerals
Quartz
Plagioclase
Orthoclase
Diopside
Hypersthene
Olivine
Ilmenite
Magnetite
Apatite
Chromite
Total
20111520
2.12
57.19
5.29
6.73
26.63
0.00
0.90
0.85
0.28
0.03
100.02
20111521
1.06
59.06
2.92
6.76
28.70
0.00
0.55
0.72
0.15
0.07
99.99
20111522
0.91
61.56
3.16
13.35
19.69
0.00
0.53
0.52
0.21
0.06
99.99
20111524
0.00
54.84
3.21
9.06
26.46
3.70
1.16
0.99
0.55
0.03
100.00
20111525
1.68
40.58
2.58
11.44
34.14
0.00
7.53
1.67
0.33
0.04
99.99
20111526
0.56
59.04
3.85
7.98
25.16
0.00
1.72
1.12
0.57
0.01
100.01
20111527
1.30
57.41
4.44
11.22
21.30
0.00
2.28
1.14
0.88
0.02
99.99
20111528
1.10
60.88
4.77
6.97
24.39
0.00
0.78
0.78
0.28
0.03
99.98
Normative
Minerals
Quartz
Plagioclase
Orthoclase
Diopside
Hypersthene
Olivine
Ilmenite
Magnetite
Apatite
Chromite
Total
LK20121004 LK20121005 LK20121006 LK20121007 LK20121008 LK20121010 LK20121011 LK20121012
9.35
3.23
7.29
3.44
6.19
5.01
4.61
2.77
53.80
60.82
54.12
56.84
57.67
59.79
58.30
57.24
26.06
6.93
5.17
4.06
5.28
6.71
4.56
8.03
0.00
2.48
11.43
1.03
8.59
2.18
9.43
5.17
8.26
25.22
20.20
31.73
19.00
24.38
20.51
23.02
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
1.19
0.50
0.54
1.52
1.69
0.83
1.25
1.76
0.39
0.59
0.48
1.14
0.75
0.79
0.73
0.87
0.56
0.19
0.68
0.20
0.79
0.28
0.58
1.12
0.03
0.04
0.10
0.04
0.03
0.03
0.03
0.03
99.99
100.00
100.01
100.00
99.99
100.00
100.00
100.01
Normative
Minerals
Quartz
Plagioclase
Orthoclase
Diopside
Hypersthene
Olivine
Ilmenite
Magnetite
Apatite
Chromite
Total
LK20121013 LK20121014 LK20121015 LK20121016 LK20121017 LK20121018
0.00
2.62
0.00
1.96
0.00
0.00
62.06
50.74
59.74
59.60
55.25
26.88
5.79
3.17
5.57
6.51
7.46
15.05
1.52
26.07
5.06
5.73
4.25
7.75
25.52
15.10
23.17
22.96
28.67
43.69
2.14
0.00
4.10
0.00
1.73
4.54
1.29
1.02
0.94
1.42
1.17
0.58
0.86
0.75
0.79
0.80
0.83
0.85
0.80
0.46
0.60
0.99
0.61
0.38
0.02
0.08
0.03
0.03
0.03
0.28
100.00
100.01
100.00
100.00
100.00
100.00
Normative
Minerals
Quartz
Plagioclase
Orthoclase
Diopside
Hypersthene
Olivine
Ilmenite
Magnetite
Apatite
Chromite
Total
1100003
7.25
57.44
4.45
1.48
27.56
0.00
0.83
0.60
0.36
0.03
100.00
1100004
3.02
59.99
7.21
0.00
28.58
0.00
0.40
0.64
0.11
0.04
100.01
1100005
1.73
56.03
7.20
2.99
30.05
0.00
0.79
0.71
0.45
0.04
99.99
1100006
2.91
58.47
10.88
4.92
17.90
0.00
2.47
0.94
1.47
0.03
99.99
61
1100007
4.77
55.02
11.50
6.14
18.22
0.00
2.17
0.92
1.24
0.02
100.00
1100013
2.74
63.42
4.58
2.72
24.94
0.00
0.63
0.68
0.25
0.03
99.99
1100001
0.00
61.97
9.94
1.14
23.07
1.53
1.24
0.76
0.28
0.07
100.00
1100017
0.00
60.33
5.91
7.93
20.57
2.80
1.11
0.86
0.47
0.03
100.01
1100002
2.92
55.81
4.35
0.71
34.07
0.00
0.81
0.99
0.31
0.03
100.00