2007:249 CIV
M A S T E R ' S T H E S I S
The Geology of the Blylodtorpet Area West of Boliden, Skellefte district
A Structural and Petrological study
Anders Gren
Luleå University of Technology MSc Programmes in Engineering
Global resources
Department of Chemical Engineering and Geosciences Division of Ore Geology
2007:249 CIV - ISSN: 1402-1617 - ISRN: LTU-EX--07/249--SE
The geology of the Blylodtorpet area west of Boliden, Skellefte district A structural and petrological study
Anders Gren
Summary
The Skellefte district is one of the most important mining districts in Sweden and hosts over 80 massive sulfide deposits. The Blylodtorpet area is located in the eastern part of the district about 8 km west of Boliden.
This work was set up with the aim to classify the rock types in the area, map geological structures and from this see if the geological environment is favorable for ore forming processes or not. The work contains a field study of the about 4 km2 large Blylodtorpet area, structures visible in outcrops were been measured, two drill cores were logged and 18 samples taken from outcrops and drill core were analyzed and interpreted. Thin sections from all 18 samples analyzed were also investigated with a microscope
The most dominant rock type of the area is dacitic mass flow units, they have a clast size of mainly gravel-sand but also block-sand and sand-silt have been found. Andesitic dykes are also present in some outcrops they have a steep dip usually around 80o and often contains sulfides. Ultramafic rock where identified in two outcrops, there is a difference in the geochemical composition between this two ultramafic rocks,one of them have a more primitive pattern in the spider diagram and have higher content of Mg,Cr and Ni.
Andesitic rock and clastic sediments are also found in the area and in one outcrop of clastic sediments the bedding planes has a very flat dip and an electromagnetic anomaly is also present over this outcrop.
The geochemical data classifies the area as a part of an island arc of a continental margin, and the rocks follow a calc alkaline trend in discrimination plots.
The area was folded at least twice with axial planes striking NE–SW and ESE-WNW respectively. Parts of the area have very flat dipping bedding planes and on some of them a way up determination were made.
In one of the drill cores a quartz-feldspar porphyry was identified at two different levels.
The most interesting ore minerals found in thin sections are sphalerite and arsenopyrite, but the most common sulfide is pyrrhotite. The quartzfeldspar porphyry and the various sulfides are all signs that can indicate the existence of an interesting, hidden mineralization.
1
Table of content Introduction ... 2
2 Sampling and analytical methods... 3
3 Results ... 4
3.1 Petrology of rocks from the field and drill cores... 4
3.1.1 Mass flow units ... 4
3.1.2 Clastic sediments ... 4
3.1.3 Andesitic rocks ... 5
3.1.4 Ultramafic intrusions ... 6
3.1.5 Andesitic dykes ... 6
3.1.6 Quartz fledspar porphyry... 6
3.1.7 Mass flow deposits with pumice clasts ... 6
3.2 Petrography ... 6
3.2.1 Mafic Rocks ... 6
3.2.2 Mass flow units ... 7
3.2.3 Sulfide minerals... 8
3.3 Geochemistry... 8
3.4 Structural geology ... 14
4 Discussion and conclusions... 15
Acknowledgements ... 16
References ... 17
Appendix 1 ... 19
Appendix 2 ... 25
Appendix 3 ... 40
2 Introduction
The Blylodtorpet area is located in the eastern part of the Skellefte district, which is one of the most important mining districts in Sweden. The Skellefte district covers an area of 120 by 30 km and is an Early Proterozoic, 1.90 to 1.87 Ga felsic magmatic region in the Fennoscandian Shield (Allen et al 1997), Fig 1. The district hosts more than 85 pyritic Zn-Cu-Au-Ag massive sulfide deposits besides a number of gold deposits related to quartz veins.
Volcanic hosted massive sulfide deposits, VMS, are generated in mainly two geological settings, 1: Mid ocean ridge settings and 2: Volcanic arc settings. In these systems hot water solutions circulate in big convective cells driven by sub volcanic intrusions located below the VMS producing hydrothermal cells. When the hot sulfide bearing water reaches the cold and saline water at the ocean floor the sulfides precipitate and as time goes by the deposit grows.
There is a divergence in opinion as to whether the solutions responsible for the deposits are of magmatic origin or if the solutions are circulating sea water or a mix of both (Evans 1993).
Allen et al (1997) concluded that most of the VMS deposits in the Skellefte district are associated with subaqueous, rhyolite cryptodome and tuff volcanoes. These volcanoes are characterized by rhyolitic pumiceous pyroclastic debris intruded by porphyritic rhyolite cryptodomes, sills and dykes.
The objectives of this study was to identify the rock types in the Blylodtorpet area and especially look for rock types related to the volcanism commonly related to ore formation.
The mapping of structures combined with interpretation of geophysical maps is done with the aim to understand and trace the deposition of the supracrustal rocks and localize faults and hinges of folds, into which it is most likely that the more ductile sulfides has been squeezed when the district was folded.
The result of this study is a contribution to the exploration for deep seated deposits in the eastern part of the Skellefte district. The search for such deposits have been intensified the last decades since it was realized already in 1974 (Ando) that most of possible outcropping ores already had been found.
Fig 1.Geological map over the Fennoscandian Shield (Weihed et al 1992)
3 1 Regional geology
The Skellefte district was formed between a continental landmass to the north and a deep marine sedimentary basin to the south. It consists of Early Proterozoic marine meta-volcanic and sedimentary rocks and host many massive sulfide deposits Fig2.
The stratigraphy can be divided into the lower Skellefte group with volcanic and sedimentary units and the upper Vargfors group.
The Skellefte group is dominated by juvenile volcaniclastic rocks, porphyritic intrusions and lavas. Intercalated sedimentary rocks are included in the group and comprise gray to black mudstone, volcaniclastic siltstone, sandstone and breccia-conglomerates. The Vargfors group consists of fine grained and coarse grained sedimentary successions with locally abundant intercalated volcanic rocks (Allen et al 1997). Fig 2 is a geological map of the Skellefte district.
At least two phases of deformations have folded the rocks in the Skellefte district. First folds are mainly isoclinal and with steep to moderately inclined axial planes that strike NW-SE.
This direction dominates the western and central parts of district but swings through east to northeast in the eastern part of the district. A second deformation is coaxial with the first folding and involves open folding with NNE-SSW striking axial planes (Weihed et al 1992).
Fig 2. Geological map of the Skellefte district (Årebäck et al 2005) with Blylodtorpet area marked.
2 Sampling and analytical methods
This work was carried out in the area surrounding the old farm Blylodtorpet that is located 8 km west of Boliden. The investigated area is situated between the lakes Bjurvattnet and Gillervattnet and is about 4 km2 large. The map sheet that covers the area is 23K Boliden SV.
The objectives of the investigation were to classify the rock types and map geological
4 structures visible in outcrops in the area. Samples were collected from representative rock types, totally 55 outcrops where found and mapped, samples from 16 of them where sent to Acme labs Canada for chemical analysis. For field mapping a common Silva compass with clinometer was used and planar structures were mapped with the dip direction method
described in (McClay 1987). For linear structures trend and plunge were measured. Magnetic susceptibility was measured with a Malå Geoscience Susceptibility Meter JH-8 on several points on each outcrop. The position of all investigated outcrops was determined with a Garmin GPS 12XL instrument.
Two drill cores, Bjurvattnet BH11 drilled 1955 and Bjurvattnet BH27 drilled 1986, from Boliden Mineral AB drill core archive where logged and one sample was taken out from each drill core for the same chemical analysis as the samples taken from outcrops. Thin sections of all 18 samples, 16 from outcrops and two from drill cores, were studied with a Nikon
microscope equipped with digital camera. For interpretation of structural data collected in field the software StereoStat was used and the geochemical data was analysed with the software GCDkit 2.1.1.
The geological maps of the area, see Appendix 1, is based on field and drill core mapping.
However, magnetic, electromagnetic and gravity field anomaly maps produced earlier by Boliden Mineral AB were essential for the delineation of the various rock types.
3 Results
3.1 Petrology of rocks from the field and drill cores
The rock names used in the following are based on field observation, major element analyses, further discussed in chapter 3.3 may modify this rock classification.
The investigated area has outcrops consisting mainly of dacitic mass flow units but one outcrop was classified as andesitic mass flow. Clastic sediments, andesitic dykes and ultramafic intrusions are other rock types that were found in outcrops during the field work.
For a complete list of all visited outcrops with coordinates and field notes (in swedish) see Appendix 2.
3.1.1 Mass flow units
A majority of the outcrops in the area are matrix supported mass flow units with felsic composition and have fragment size ranging from block down to sand and silt, Fig 3. The fragments are usually sharp edged, but some of the outcrops show rounded fragments with a more polymict composition containing both mafic and felsic clasts. On some of the mass flow units bedding planes were measured and on a few of them a way up determination was done.
On weathered surface the mass flow units have clasts more resistant to weathering than the matrix consisting of smaller fragments, which can be seen in Fig 3b.
3.1.2 Clastic sediments
The clastic sediments have a silty clayey grain size and cause an electromagnetic anomaly.
Some of these anomalies were previously checked by trenching but without any sulfide mineralizations found except for some insignificant pyrrhotite impregnation. This rock type is also present in the drill core BH27 at three different levels at 259-274m, 480.5-482m and 486- 493.5m, see drill core logs in Appendix 3.
5
a) b)
c) d)
Fig.3. a) mafic dyke with chilled margins, b) mass flow on a weathered outcrop surface with one block of fresh surface, c) block – sand polymict mass flow d) layered mass flow with finer fragments to the right.
3.1.3 Andesitic rocks
The andesitic rocks have a light green-gray color, Fig 4. They are heterogeneous with, in one outcrop, an ash layer in between two coherent units of andesitic rock. This suggests that this rock may be a lava flow.
Fig 4. Andesitic rock with a silty layer.
6 3.1.4 Ultramafic intrusions
Two outcrops consist of ultramafic rock with a green color. This rock type has a smooth weathered surface and looks coherent.
3.1.5 Andesitic dykes
Andesitic dykes occur in some outcrops, and they have a width ranging from about 10 to 70 cm. They have a green color and the majority of them have a steep dip around 80o to the SE, NW and SW. Fig 3 shows an andesitic dyke with nice chilled margins.
3.1.6 Quartz fledspar porphyry
Two sections in drill core BH27 at 404m-414m and 482m-486m down quartz-feldspar porphyry occur. This rock type was only found here, no quartz-feldspar porphyry was found in outcrops.The drill core was drilled in 1986 as a part of Boliden Mineral AB exploration program for deep seated deposits (Jonsson 2006). See Appendix 3 for graphical drill core logs.
3.1.7 Mass flow deposits with pumice clasts
In one outcrop(no 20061101) pumice occur, this rock type have a more rhyolitic composition, the same rock type was also found in drill core BH27 at about 260m down
3.2 Petrography
A table of identified minerals in each sample is presented in Appendix 2.
3.2.1 Mafic Rocks
The minerals in samples taken from mafic rock, see Fig 5, consists mainly of amphibole with plagioclase in ground mass, some pyrrhotite was identified in one sample taken from a basaltic dyke.
Fig 5. Mafic rock in thin section, photo taken under crossed polarized light
7 3.2.2 Mass flow units
In thin sections taken from dacitic mass flow samples, Fig 6, the most common mineral is quartz and plagioclase, which in some samples occur as phenocrysts. Biotite occurs in all of them often with chlorite. Calcite and sericite is present in some of the samples and microcline was found in one sample.
a) b)
c) d)
Fig 6. a) Plagioclase phenocryst, b) Calcite, c) Chlorite in center of picture Biotite to the left, d) Sericite. All pictures taken under crossed polarized light.
8 3.2.3 Sulfide minerals
The most common sulphide is pyrrhotite, Fig 7, pyrite is also present but in smaller amount.
In two samples, no 20061114 and no 20061138, sphalerite occur and no 20061138 also contains arsenopyrite.
a) b)
c) d)
Fig 7. a) Pyrrhotite with pyrite in cracks, b) Sphalerite, in bottom part of the picture, c) Arsenopyrite, d) Arsenopyrite crossed polarized light.
3.3 Geochemistry
Major element data plotted in variation diagrams in Fig 8 where the elements are plotted against SiO2, it is observed that even though some elements show a large spread the trend for the major elements is decreasing with increasing SiO2 content except for the alkalis that increases with higher SiO2 content. This trend for the major elements follows the calc alkaline trend that is typical for convergent plate margins (Blatt et al 1996). There is a gap in the interval from 58 – 67 w% SiO2 where none of the samples fall into. Only two samples fall into the andesitic interval from 52 to 58 w% SiO2.
9
45 50 55 60 65 70 75
1012141618
Al2O3
SiO2
45 50 55 60 65 70 75
5101520
MgO
SiO2
45 50 55 60 65 70 75
2468101214
CaO
SiO2
45 50 55 60 65 70 75
12345
Na2O
SiO2
45 50 55 60 65 70 75
0123
K2O
SiO2
45 50 55 60 65 70 75
0.30.50.70.9
TiO2
SiO2
45 50 55 60 65 70 75
0.050.100.150.200.25
P2O5
SiO2
45 50 55 60 65 70 75
46810
FeOt
SiO2
Fig 8. Variation diagrams for major elements versus SiO2 w% content, legend in Fig 9.
In the Nb/Y-Zr/TiO2 plot of Winchester and Floyd (1977) all except two of the mass flow samples fall into the field of Rhyodacite/Dacite but in the Zr/TiO2-SiO2 of Winchester and Floyd (1977) all of them fall into that field. According to Cox et al (1979) the most accurate way to classify altered rock is to use ratios of the most immobile elements because they are very resistant to alteration processes. One reason that two dacitic mass flow samples are classified as andesite in Fig 9a could be that they are polymict with mafic clasts so that the Zr/
TiO2 ratio becomes low.
10
Phonolite
Trachyte Rhyolite
Andesite/Basalt Rhyodacite/Dacite
SubAlkaline Basalt
Trachy- andesite
Alk-Bas Com/Pant
Bsn/Nph Andesite
0.01 0.05 0.10 0.50 1.00 5.00
0.0010.0050.0500.5005.000
Nb Y − Zr TiO2 plot (Winchester + Floyd 1977)
Nb/Y ZrTiO2
Phonolite Trachyte Rhyolite/Dacite
Rhyodacite/Dacite
Sub-AB
TrAn
AB
Com/Pant
Bas/Trach/Neph Andesite
0.001 0.010 0.100 1.000
4050607080
Zr TiO2 − SiO2 plot (Winchester + Floyd 1977)
Zr TiO2 SiO2
a) b)
Al Mg
FeT+ Ti
High-Fe tholeiite basalt Andes Da ite
cite
Rhyolite Rh
yolite Da
cite Andes
ite Ba
salt High-Mg tholeiite basalt
Kom atiitic ba
salt
Kom atiite TH
CA
KO MAT
IITE Jensen (1976)
c)
Fig 9. Rock classification plots, a) Nb/Y-Zr/TiO2 (Winchester and Floyd 1977) , b) Zr/TiO2- SiO2 (Winchester and Floyd 1977), c) Al- Fe+Ti-Mg (Jensen 1976).
In the Jensen (1976) plot in Fig 9 the samples plot in the calc alkaline field and here the mass flows fall into the dacite and andesite fields.
One ultramafic intrusion is classified as komatiit, this sample is high in Mg Cr and Ni compared to the other ultramafic rock sample.
The REE patterns for the basaltic rocks are weakly fractionated LaN/YbN = 2.5-4.5. For dacitic mass flows the LaN/YbN is higher 5.5-7.5. In Fig 10 REE patterns for each classified rock sample are plotted against normalized REE values in rock/chondrite (Nakamura 1974). The lower curve in the plot with Ultramafic intrusions is the sample high in Mg Cr and Ni.
The REE patterns for the samples analyzed in this work are similar to REE patterns from the Skellefte group volcanics in the Långdal-Boliden area presented in (Bergström 2001).
Andesitic dyke Andesitic mass flow Andesitic rock Dacitic mass flow Gabbro
Ultramafic intrusion
11
Andesitic dyke
Sample/ REE chondrite
La Pr Pm Eu T b Ho T m Lu
110100
Andesitic m ass flow
Sample/ REE chondrite
La Pr Pm Eu T b Ho T m Lu
110100
Andesitic rock
Sample/ REE chondrite
La Pr Pm Eu T b Ho T m Lu
110100
Dacitic m ass flow
Sample/ REE chondrite
La Pr Pm Eu T b Ho T m Lu
110100
Gabbro
Sample/ REE chondrite
La Pr Pm Eu T b Ho T m Lu
110100
Ultram afic intrusion
Sample/ REE chondrite
La Pr Pm Eu T b Ho T m Lu
110100
Fig 10. REE patterns for the different rock types. Normalized REE abundance in
Rock/Chondrite (Nakamura 1974), gray area is the area in which all samples falls into.
In the different geotectonic discrimination plots the basaltic rocks with SiO2 content from 45- 54 w% (Mullen 1983) falls into the calc alkaline basalt field, one of them falls into the field of island arc tholeiite basalt (Fig 11).
In the Zr-Ti/100-3*Y discrimination plot (Pearce and Cann 1973), most of the mafic rock samples fall into the B-field (Fig 12a). In the Zr-Ti/100-Sr/2 (Pearce and Cann 1973) most of the samples fall into the A and C field (Fig 12b), and in the Zr/Ti discrimination plot of Fig 13 the samples falls into the fields A, B and C.
The result from the geochemical analysis is presented in Appendix 2.
12
10xMnO 10xP2O5
TiO2
CAB OIT
MORB
IAT
OIA Bon
45<SiO2<54
Fig 11. Tectonic discrimination diagram (Mullen 1983) for basaltic rocks, SiO2 = 45-54 w% . Fields are: CAB = Calc Alkaline Basalt, IAT = Island Arc Tholeiite basalt, MORB = Mid Ocean Ridge Basalt, OIA = Ocean Island Alkali basalt, OIT = Ocean Island Tholeiite basalt.
Zr 3xY
Ti 100
A
B
C D
A = IAT B = MORB, CAB, IAT C = CAB D = WPB
Zr Sr 2
Ti 100
A B C
A = IAT B = CAB C = MORB
a) b)
Fig 12. Tectonic discrimination plots, a) Zr-Ti/100-3*Y (Pearce and Cann 1973), b) Zr- Ti/100-Sr/2 (Pearce and Cann 1973). Fields are WIP = Within Plate Basalt, for IAT, MORB,
CAB see Fig 10 for explanation
13
0 50 100 150 200 250
050001000015000
Zr (ppm)
Ti (ppm)
A = IAT B = MORB, CAB, IAT C = CAB D = MORB
A B
C D
Fig 13. Tectonic discrimination plot, Zr-Ti (Pearce and Cann 1973) for basaltic rock samples.
For field explanation see Fig 10.
14 3.4 Structural geology
In the area three linear anomalies been interpreted as faults. One strikes relatively straight to NW-SE and the two others strike NE-SW and ENE-WSW. In field it was possible to measure foliation planes on almost every outcrop visited. The most common foliation planes in the area strike mainly in the NE – SW direction and dip ranging between 75o - 90o in most cases.
This strike of the foliation planes is thus parallel to one of the lineations.
a) b)
c)
Fig 15. Stereographic plots, a) Poles to fold axis, b) contours of Poles to foliation planes, c) Poles to bedding planes.
Fig 15 contains stereographic projection plots of fold axis, poles to foliation planes and poles to bedding planes. In Fig 15a the poles to the fold axis are plotted, a majority of the fold axis that are defining the deformation of the area have axial planes that strikes straight NE – SW, this axial plane strikes in the same direction as the majority of the foliation planes. There are two fold axis that are defining folds with a different strike of the axial plane, this axial plane strikes ESE-WNW. This, and the fact that the plot of the poles to bedding planes in Fig 15c show a distribution of bedding attitudes away from simple great circle or conical patterns on the stereographic projection, suggests that the area have been deformed in two phases. Fig 16 is an attempt to illustrate a folded surface with the axial planes from the two folding events perpendicular to each other.
15 Fig 16. Surface folded twice.
4 Discussion and conclusions
The investigated area consists mainly of dacitic mass flow units with angular clast. They have a clast size of mainly sand-gravel but sand-silt and block-sand composition have also been found. The depositional environment for the mass flows in the area was subaqueous and below wave base since no evidences of reworking. The mass flow units have been sliding down the slopes of the volcanoes by gravity driven processes and then deposited on
topographic lows. A few polymict mass flows consist of rounded clasts that can indicate that the they have been mechanically eroded due to long transportation.
The magnetic susceptibility varies with the different rock types and are generally higher for the ultramafic and andesitic rocks, with values ranging between 40-50*10-5 SI, than for the dacitic mass flow units with values ranging between 5-10*10-5 SI.
The geochemical data for all samples follows the calc alkaline trend and in the different tectonic discrimination plots the samples falls into the calc alkaline and island arc tholeiite fields. The conclusion that the area was a part of an island arc of a continental margin can be assumed because of the fact that most of the outcrops consist of dacitic mass flows. This would not be the case if the island arc was more isolated where a more andesitic composition can be expected (Baker 1982).
The two mafic intrusions are almost identical in outcrops with a smooth green surface but the geochemistry differs. The one with high Mg, Cr, and Ni have a more primitive composition in the spider plot in Fig 10. The other one is more fractionated and have a small negative Eu anomaly. The high Mg, Cr and Ni ultramafic sample has very similar geochemistry when comparing with the Mg basalts from the Vargfors group presented in (Bergström 2001) and is thus younger than the majority of the rocks in the area.
The andesitic dyke is more similar with the ultramafic than the andesitic rocks, both
geochemically mineralogically. The amphibole crystals in the dyke have the same size as the amphibole in the ultramafic samples in the andesitic rock the crystals are smaller. Olivine and serpentine where found in the thin section from the Mg rich ultramafic rock, some serpentine where found in the other ultramafic sample as well but none of these minerals where found in the andesitic dyke.
16 The identification of quartz porphyry in drill core BH27 is interesting because this type of intrusive rock have a close relation to VMS ore forming processes in the district (Allen et al 1997)
This supports the idea that Blylodtorpet area at least has the potential of hosting a VMS mineralization. Other interesting evidences of mineralizations are the occurrences of sphalerite and arsenopyrite, and in some cases sericite alteration.
The area is folded and from field data it seems to be at least two different folding events. This folding is positive because it can collect the sulfide minerals in the fold hinges. A good
example of this is the Kristineberg deposit. Malmberget iron ore is another example.
The most interesting spot for exploration in the investigated area is near one outcrop of the clastic sediments, here there is a syncline and an electromagnetic anomaly is present (see Appendix 1 for location). It is probably the sediment layer itself that causes the anomaly because no gravity anomaly is present which can be expected if a massive sulfide body is present under the sediments, but it would be interesting to drill and see what can be found further down in the syncline and get a better view and understanding of the structural geology.
Acknowledgements
I thank Annika Wasström for her help during the field work, drill core logging, reading the manuscript and making valuable suggestions to improve the text.
Lennart Widenfalk for the review of the content, result and conclusions presented in this work.
The author is also grateful to Boliden Mineral AB for the grant and support of this work.
Division of ore geology and applied geophysics, Luleå University of Technology, has financed the thin sections.
17 References
Allen, R.L., Weihed, P. and Svensson, S-Å., 1997. Settings of Zn-Cu-Ag-Au massive sulfides deposits in the architecture of a 1.9 Ga marine volcanic arc, Skellefte district Sweden:
Economic Geology, 91: 1022-1053.
Ando, S., 1974. Synpunkter på svensk gruvindustris framtid: Svenska gruvföreningen meddelande 140, vol 9
Baker, P.E., 1982. Evolution and classification of orogenic volcanic rocks; a review in Thorpe, R S (ed), Andesites: John Wiley & Sons
ISBN 0-471-28034-8
Bergsröm, U., 2001. Geochemistry and tectonic setting of volcanic units in the northern Västerbotten county, northern Sweden: In Weihed, P.(ed): Economic geology research. Vol 1, 1999-2000. Uppsala 2001. Sveriges geologiska undersökning C833: 69-92.
ISBN 91-7158-665-2
Blatt, H., and Tracy, R, J., 1996. Petrology: W.H. Freeman and company ISBN 0-7167-2438-3
Cox, K., G, Bell, J D. and Pankhurst, R.J., 1979. The interpretation of igneous rocks: George Allen & Unwin., ISBN 0-04-552015-1
Evans, A.M., 1993. Ore Geology and Industrial Minerals: Blackwell Science Ltd., ISBN 0-632-02953-6
Jensen, L.S., 1976. A new cation plot for classifying subalcalic volcanic rocks, Ontario Div.
Mines. Misc. Pap. 66
Jonsson, Rolf., 2006. Boliden Mineral AB: Personal conversation
McClay, K., 1987. The mapping of geological structures: John Wiley & Sons ISBN 0 471 932424
Mullen, E.D., 1983, MnO/TiO2/P2O5. A minor element discriminant for basaltic rocks of oceanic environments and its implications for petrogenesis: Eart Planet. Sci. Lett, 62: 53-62 Nakamura, N., 1974. Determination of REE, Ba, Mg, Na and K in carbonaceous and ordinary chondrites: Geochim. Cosmichim. Acta, 38: 757-775
Pearce, J.A and Cann, J.R., 1973. Tectonic setting of basic volcanic rocks determined using trace element analyses: Eart Planet. Sci. Lett, 19: 290-300
Pearce, J A, Harris, N B W and Tindle, A G, 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks: J. Petrol. 25: 956-300
18 Weihed, P., Bergman, J., and Bergström, U., 1992. Metallogeny and tectonic evolution of the Early Proterosoic Skellefte district, northern Sweden: Precambrian Research, 58 :143-167 Winchester, J.A and Floyd, P.A., 1977. Geochemical discrimination of different magma series and there differentiation products using immobile elements: Chem. Geol 20: 325-201
Årebäck, H, Barret, J and Abrahamsson, S, 2005: The Paleoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden, part 1: Geology: Mineralum deposita 40: 351-367
19
Appendix 1
Maps
20 Fig 1. Geological map over Blylodtorpet area.
21 Fig 2. Outcrop and drill core sample point with sample number.
22 Fig 3. Mapped fold axis in the area.
23 Fig 4. Bedding planes and way up determinations.
24 Fig 5. Location of interesting syncline, coordinates 7204779N 1711246E
25
Appendix 2
Tables
26 Table 1 Major element
ELEMENT SiO2 Al2O3 Fe2O3 MgO CaO Na2O K2O TiO2 P2O5 MnO Cr2O3 Ni Sc LOI TOT/C TOT/S SUM
SAMPLES % % % % % % % % % % % ppm ppm % % % %
20061101 73.19 13.25 3.97 0.78 2.46 1.39 3.19 0.284 0.051 0.08 0.001 8 12 1.3 0.14 0.02 99.95 20061102 54.41 17.7 10.36 7.21 1.82 2.14 0.87 0.967 0.182 0.15 0.003 8 30 4 0.07 0.01 99.82 20061104 46.16 12.61 11.11 9.51 14.76 0.41 0.56 0.468 0.12 0.35 0.084 131 38 3.7 0.86 0.01 99.86 20061111 72.75 14.29 2.9 1.35 2.21 1.21 2.64 0.359 0.073 0.07 0.001 6 12 2 0.05 0.01 99.85 20061114 67.14 13.79 6.99 3.01 4.26 0.7 2.56 0.476 0.115 0.13 0.001 5 18 0.8 0.07 0.33 99.97 20061128 58.09 16.41 9.98 2.92 6.93 0.78 2.61 0.79 0.153 0.14 0.002 32 26 1 0.36 0.71 99.81 RE 20061128 57.86 16.39 10.14 2.94 6.96 0.79 2.66 0.803 0.151 0.14 0.002 14 26 1.1 0.37 0.69 99.94 .STD BCR-2 54.27 13.37 13.58 3.53 6.89 3.01 1.74 2.402 0.358 0.19 0.002 12 31 0.4 0.03 0.03 99.75 20061132 49.64 13.98 9.49 10.98 11.1 1.85 0.13 0.597 0.197 0.19 0.126 95 37 1.7 0.06 0.01 100 20061138 69.58 15.41 4.21 1.04 2.81 1.47 3.81 0.395 0.072 0.08 0.001 5 15 0.9 0.08 0.02 99.78 20061140 55.99 15.74 9.25 5.12 9.07 1.99 1.02 0.515 0.106 0.14 0.01 12 37 1 0.15 0.01 99.96 20061141 51.7 19.11 11.01 4.68 6.12 3.8 0.88 0.772 0.129 0.18 0.001 5 33 1.4 0.03 0.08 99.79 20061143 43.95 10.26 10.78 20.27 7.91 0.24 0.17 0.425 0.122 0.18 0.279 660 27 5.2 0.09 0.01 99.87
.STD BCR-2 53.29 13.56 13.97 3.63 7.05 3.06 1.77 2.415 0.353 0.19 0.002 9 32 0.6 0.02 0.02 99.9
20061144 49.16 12.21 11.69 10.8 11.67 1.29 0.17 0.534 0.125 0.22 0.173 333 31 1.8 0.18 0.01 99.89 20061151 69.52 14.09 5.55 2.06 2.78 2.08 2.39 0.317 0.055 0.11 0.001 5 20 1 0.04 0.01 99.96 20061152 68.57 15.32 4.95 1.18 1.55 5.22 1.76 0.403 0.099 0.08 0.001 5 14 0.8 0.08 0.01 99.93 20061153 68.98 13.21 6.83 2.11 2.92 1.13 2.8 0.699 0.245 0.11 0.001 5 17 0.9 0.05 0.01 99.94 20061154 71.14 13.55 4.28 1.29 2.65 3.51 1.98 0.334 0.063 0.1 0.001 5 12 0.9 0.16 0.01 99.8 20061001 71.51 13.2 4.67 2.63 3.33 1 1.75 0.326 0.075 0.09 0.001 5 12 1.4 0.04 0.03 99.98 20061002 69.35 12.1 4.68 2.76 5.87 0.68 1.97 0.256 0.052 0.15 0.001 12 10 2.1 0.56 0.04 99.97 STANDARD SO-
18/CSC 58.21 14.12 7.63 3.34 6.4 3.69 2.14 0.689 0.829 0.39 0.55 44 24 1.9 3.15 4.27 99.9
27 Table 2. Metals
ELEMENT Mo Cu Pb Zn Ni As Cd Sb Bi Ag Au Hg Tl Se
SAMPLES ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppb ppm ppm ppm
20061101 1.1 24.9 3.3 65 0.4 0.7 0.1 0.2 0.1 0.1 2.4 0.01 0.2 <.5 20061102 0.8 1.5 0.7 88 2 0.9 <.1 0.2 0.6 <.1 0.8 0.01 <.1 <.5 20061104 0.1 1.1 3.5 35 27.6 7.6 0.1 0.4 0.1 <.1 16.9 <.01 0.2 <.5 20061111 0.3 3.4 4.2 66 0.6 3 0.1 0.4 <.1 <.1 1.5 <.01 0.3 <.5 20061114 0.7 20.5 4.9 83 1.4 35.6 0.1 0.5 0.1 <.1 1.2 <.01 0.8 <.5 20061128 0.4 38.2 7.3 134 9 29.5 0.2 0.3 0.1 <.1 1.9 <.01 0.9 1.2 RE 20061128 0.4 39.3 7.5 135 8.9 30.5 0.1 0.3 0.1 <.1 1.9 <.01 1 1.1
.STD BCR-2 - - - - - - - - - - - - - -
20061132 0.4 0.7 3 20 22.7 1.1 <.1 0.2 <.1 <.1 <.5 <.01 <.1 <.5 20061138 0.4 7.7 6 78 0.6 0.7 0.1 0.2 <.1 <.1 2 <.01 0.3 <.5 20061140 0.1 77.3 5.1 35 6 3.9 0.1 0.2 <.1 0.2 5.2 <.01 0.3 <.5 20061141 0.2 63.4 0.7 65 3 1.2 0.1 0.7 <.1 <.1 1.4 0.01 0.3 <.5 20061143 0.1 1.2 0.7 68 325.1 15.2 <.1 0.1 0.1 <.1 8.6 <.01 <.1 <.5
.STD W-2 - - - - - - - - - - - - - -
20061144 0.3 0.5 4.2 21 101.9 108.9 0.1 0.4 <.1 <.1 1.5 <.01 0.1 <.5 20061151 0.1 3.9 3 121 0.8 1.6 0.1 0.1 <.1 <.1 1.8 <.01 0.2 <.5 20061152 0.2 5.4 2.6 83 0.7 0.9 0.1 0.2 <.1 <.1 1.4 <.01 0.4 <.5 20061153 0.2 25.3 3.3 95 0.7 2.8 0.1 0.4 0.1 <.1 1.5 <.01 0.4 <.5 20061154 0.2 10 2.3 71 1.2 1.2 0.1 0.4 <.1 <.1 2.8 <.01 0.3 <.5 20061001 0.4 19.8 5.4 69 0.7 0.5 0.2 0.5 0.2 <.1 0.8 <.01 0.3 <.5 20061002 0.9 12.2 6.4 58 0.8 1 0.3 0.3 <.1 <.1 2.1 <.01 0.6 <.5 STANDARD
DS7 20.8 108 68.1 415 56.2 50.1 6.6 5.7 4.5 0.9 72.9 0.2 4.2 4
28 Table 3. REE analysis
ELEMENT Ba Be Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y La
SAMPLES ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm
20061101 422 1 2 0.9 17.6 4.1 7.2 47 2 124 0.4 4.1 3.3 6 0.5 141 23 20
20061102 369 1 15 0.3 20.5 1.7 3.7 8.9 1 139 0.2 0.7 0.6 239 0.7 58 15.6 5.3
20061104 79.2 1 42.4 0.4 12.5 0.7 1.9 14 1 158 0.1 0.9 0.6 215 3.2 28 9.6 5
20061111 290 1 3 1 17 2.8 5.9 39 1 219 0.4 2.9 1.6 8 1.3 107 17.7 19
20061114 254 1 7.7 1.1 17.2 2.7 5 43 1 179 0.4 3.1 1.8 66 0.2 97 21.1 18
20061128 488 1 20.9 0.8 16.2 1.8 3.3 35 1 238 0.2 0.6 0.6 210 0.3 61 12.5 7.5
RE 20061128 488 1 25.8 0.8 17.7 1.8 3.7 37 1 253 0.2 0.6 0.7 217 0.1 65 13 7
.STD BCR-2 675 2 33.5 1.1 19.4 4.5 11 43 2 333 0.7 5.7 1.5 395 0.3 161 33.9 22
20061132 22.1 1 37.2 0.2 14.7 2 3.7 2 1 369 0.3 4.1 1.8 214 <.1 72 18.8 11
20061138 731 2 2.8 1.3 18.1 3.8 7.3 55 2 144 0.5 4.4 2.2 5 0.5 144 25.5 21
20061140 375 1 23.9 0.5 15.2 1.2 2.3 16 1 243 0.1 0.7 0.4 204 0.3 41 9.9 6.6
20061141 317 1 22.8 0.3 17.7 1 1.8 14 <1 349 0.1 0.5 0.4 253 0.2 35 10.4 7.8
20061143 25.9 1 59.2 0.2 10.4 1.1 1.9 2.8 1 60 0.1 2.5 0.8 148 0.3 37 10.5 6.5
.STD BCR-2 685 2 36.7 1 21.1 4.8 12 45 2 340 0.7 5.7 1.7 414 0.4 173 35.9 23
20061144 26.2 <1 50.5 0.1 13.3 1.4 2.1 1.9 1 142 0.2 2.2 0.7 181 0.1 44 14.3 7.9
20061151 310 1 1.4 0.8 19.9 4.2 7.8 40 1 103 0.5 3.8 1.5 5 0.3 141 29.3 16
20061152 686 2 3.4 0.8 21.3 4.3 7.7 51 1 175 0.5 4.1 2.2 9 0.4 150 22.8 8.4
20061153 499 1 8.5 0.8 16.9 4 7.2 48 1 122 0.4 2.5 1.4 39 0.3 135 25.7 18
20061154 641 1 3.2 0.8 15.5 3.4 5.7 38 1 243 0.4 3.3 1.8 14 0.9 117 18.4 16
20061001 211 2 4.4 0.8 16.1 3.6 6 32 1 148 0.4 3.2 1.7 9 0.4 117 19.6 18
20061002 291 1 1.7 0.8 14.9 4.2 6.4 39 1 181 0.4 3.6 2.6 <5 0.2 136 26.2 21
STANDARD
SO-18 507 1 26.7 6.9 17.4 9.7 21 28 15 406 7.2 9.9 16 195 15 287 33.3 12
29 Table 4 REE analysis
ELEMENT Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
SAMPLES ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm
20061101 43.6 5.1 20.8 4.3 0.95 3.88 0.6 4 0.8 2.29 0.4 2.4 0.4 20061102 13.6 1.8 8.5 2.5 0.74 2.83 0.5 2.8 0.5 1.54 0.2 1.4 0.2 20061104 11.1 1.6 6.6 1.7 0.73 2.11 0.3 1.8 0.3 0.88 0.1 0.8 0.1 20061111 38.2 5 19.8 3.6 1.09 3.6 0.6 3.1 0.5 1.75 0.3 1.8 0.3 20061114 39.3 5 20.4 4 1.01 3.83 0.6 3.6 0.6 1.94 0.3 1.9 0.3 20061128 17.3 2.3 10.4 2.5 0.72 2.7 0.4 2.5 0.4 1.27 0.2 1.2 0.2 RE 20061128 17.6 2.4 11.3 2.7 0.76 2.65 0.4 2.4 0.4 1.29 0.2 1.3 0.2 .STD BCR-2 47.7 6.2 26.4 6 1.68 6.29 1 6.3 1.1 3.21 0.5 2.8 0.4 20061132 25.9 3.4 14.6 3.3 0.84 3.3 0.5 3.3 0.6 1.82 0.3 1.7 0.3 20061138 43.9 5.7 23.2 4.4 1.15 4.29 0.7 4.1 0.8 2.37 0.4 2.5 0.4
20061140 14.6 2 8.6 1.9 0.65 1.8 0.3 1.7 0.3 0.92 0.1 1 0.1
20061141 13.3 1.9 8.7 2.1 0.75 2.1 0.3 1.9 0.4 1.04 0.2 1 0.1
20061143 11.5 1.7 7.6 2.1 0.7 1.93 0.3 1.8 0.4 1.06 0.2 1 0.1
.STD BCR-2 50.5 6.6 28.2 6.5 1.87 6.89 1.1 6.5 1.2 3.5 0.5 3.2 0.5 20061144 16.1 2.2 9.9 2.2 0.68 2.5 0.4 2.5 0.4 1.38 0.2 1.3 0.2 20061151 40 5.1 21.5 4.6 1.32 4.89 0.8 5 1 2.91 0.5 3.1 0.5
20061152 23 2.6 10.9 2.7 0.9 3.35 0.6 4 0.7 2.43 0.4 2.3 0.4
20061153 42.4 5.6 23.9 5 1.36 5.09 0.8 4.5 0.9 2.53 0.4 2.2 0.4 20061154 34.8 4.1 17.8 3.3 0.87 3.07 0.5 3.1 0.6 1.84 0.3 1.9 0.3 20061001 40.4 4.9 18.9 3.7 0.84 3.65 0.6 3.2 0.6 2.06 0.3 2 0.3 20061002 47.9 5.7 23.4 4.2 1.11 4.25 0.7 4.3 0.8 2.5 0.4 2.4 0.4 STANDARD
SO-18 26.3 3.3 14 2.9 0.87 2.95 0.5 3 0.6 1.8 0.3 1.6 0.3
30 Table 5. All visited outcrops with coordinates and field notes.
Locality N-coord E-coord TyOfObs Rocktype Structure Mineral Grain Color Object Val.-I
Val.-
II Type Outcrop no --- --- --- --- --- --- --- --- --- DipDir Dip ---
20061101 7204992 1711691 HÄLL <
1 PUMICE BLOCK-SAND PYRIT FINKORNI GR SEKUNDÄR 170 85 SVAG FÖRSKIF - FIAMME - - - PRIMÄR 140 80 ÖVRIGT SE KO - PORFYRISK PLAGIOKLAS - - ÖVRIGA O 50 75 SPRICKA - SUR - - - - -
- - - - - STUFF
KEMISK ANALY - - - - - - SLIPPROV
20061102 7203889 1712072 HÄLL <
1 MASSFLÖDE INTERMEDITÄR KLORIT FINKORNI
MÖRKT
GR SEKUNDÄR 125 80
SVAG FÖRSKIF
- GRUS-SAND - - - STÄNGLIG 215 70 SVAG STÄNGLI - PORFYRISK PLAGIOKLAS - - - -
- - - - - STUFF
KEMISK ANALY - - - - - - SLIPPROV
20061103 7204612 1711438 HÄLL <
1 VULKANIT SUR AKTINOLIT FINKORNI GR SEKUNDÄR 70 90 FOLIERAD
- SILICIFIERAD BIOTIT -
MÖRKT
GR - 90 70 - - RÄNDER KVARTS - - ÖVRIGA O 240 75 FYLLD SPRICK - - - - - - 70 80 - - - - - - VECKAXLA 250 80 SYMMETRISK C, Susceptibilitet (10-20)*10^-5 SI (10)
20061104 7204642 1711404 HÄLL <
1 MASSFLÖDE BLOCK-SAND SERICIT - LJUSGR PRIMÄR 130 80
HETEROGEN LA
- POLYMIKT BIOTIT - - SEKUNDÄR 155 80 STARKT FOLIR
- - - - - PRIMÄR 150 80
HETEROGEN LA
- - - - - SEKUNDÄR 145 80 FOLIERAD - - - - - - 330 80 -
ANDESIT GÅNGAR - FINKORNI
MÖRKT
GR ÖVRIGA O 225 80 GÅNG
31
- OMVANDLAD AKTINOLIT - - - 280 85 SPRICKA - - - - - VECKAXLA 50 50 ASYMMETRISK - - - - - SEKUNDÄR 150 75 AXIALPLAN - - - - - ÖVRIGA O 230 80 GÅNG - - - - - - 200 80 - - - - - - - 210 80 - - - - - - - 120 80 -
- - - - - STUFF
KEMISK ANALY - - - - - - SLIPPROV
20061105 7204637 1711389 HÄLL <
1 MASSFLÖDE GRUS-SAND AKTINOLIT - LJUSGR SEKUNDÄR 150 80 STARKT FOLIR - POLYMIKT - - - ÖVRIGA O 280 90 SPRICKA ANDESIT GÅNGAR AKTINOLIT - - - 240 75 GÅNG - - PYRIT - - - 125 85 - - - MAGNETKIS - - - 280 80 SPRICKA - - KOPPARKIS - - - - C, fragment från sidobergart i gång
20061106 7204609 1711389 HÄLL <
1 MASSFLÖDE GRUS-SAND - - - ÖVRIGA O 355 85 SPRICKA - - - - - - 150 70 - - - - - - SEKUNDÄR 325 80 FOLIERAD
20061107 7204594 1711376 HÄLL <
1 MASSFLÖDE GRUS-SAND - - LJUSGR SEKUNDÄR 140 85 FOLIERAD - SUR - - - - - - GRUS-SAND AKTINOLIT - GR ÖVRIGA O 325 80 SKJUVZON - - KLORIT - - - - - - BIOTIT - - - -
ANDESIT GÅNGAR AKTINOLIT - - ÖVRIGA O 320 80
HETEROGEN LA
20061108 7204600 1711368 HÄLL <
1 MASSFLÖDE BLOCK-SAND KV-FSP-POR - - SEKUNDÄR 150 80 FOLIERAD
- - ANDESIT - - PRIMÄR 160 80
HETEROGEN LA
- - DACIT - - - - - - AKTINOLIT - - - -
