MASTER'S THESIS
Geochemical and kinematic study of shear zones within the "gold line", Lycksele- Storuman province, northern Sweden
Per Samskog
Master of Science Exploration and Environmental Geosciences
Luleå University of Technology Department of Civil, Environmental and Natural Resources Engineering
Geochemical and kinematic study of shear zones within the “gold line”, Lycksele-Storuman province, northern Sweden.
Per Samskog Division of applied geochemistry and geoscience, Luleå University of Technology 2011
Abstract A kinematic and geochemical study was carried out in shear zones within the “gold line” in the Lycksele Storuman province, northern Sweden, with the aid of, field mapping, thin sections and whole rock geochemical data. The shear zones were hosted by metabasalt, metasediments, felsic metavolcanics and metagranodiorite. The area has undergone major deformation during the Svecofennian orogeny and the shear zones in this study are interpreted as being formed during this event. The geochemical study was carried out in three localities, the Grundfors road cut, Sjöliden and the Svartliden gold mine. The data from Grundfors and Sjöliden indicates two different magmatic arc sources, volcanic arc affinity for Sjöliden and MORB or Island arc affinity for Grundfors. The bedrock at Grundfors displayed silicified zones but the protolith for these was not possible to determine. Sjöliden showed no major elemental exchange between the samples. Svartliden showed two different sources for the metasediments present, acid arc source and an oceanic island arc source. The metasediments formed from an acid arc source displayed a clear relationship based on immobile elements to the highly silicified rocks at Svartliden. This study used one of the acid arc source metasediments as a precursor with a resulting mass gain of 1800%. The validity of the protolith can be argued. The tectonic study was carried out in 5 localities, Grundfors, Sjöliden, Svartliden gold mine, “the mylonite” and “the granodiorite”. Both Grundfors and Sjöliden indicate two kinematic events, one with steep reverse movements and a later one with both extensional and strike slip components of deformation, of which the latter had a dextral sense in “the mylonite” and sinistral in the Grundfors outcrops. The kinematic data from Svartliden showed only reverse movements whereas “the mylonite” showed two movements, one dextral strike slip movement and one south side up reverse movement. Svartliden with its ENE striking shear zone and “the mylonite” with its NW trending shear zone are interpreted to have formed during N S compression. The movements in Grundfors, Sjöliden and “the granodiorite” are interpreted to have formed during an E W compression, with either a transpressive regime or a later orogenic collapse alternatively. The shear zones in this study displayed both ductile and brittle movements indicating a temperature gradient through the zone.
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Introduction ...... 5 Geological setting...... 8 Regional geology...... 8 Tectonic setting and structural evolution ...... 9 Regional alterations...... 10 Studied localities ...... 12 Methods...... 12 Mapping ...... 12 Thin Section studies ...... 13 Kinematics...... 13 Alterations ...... 14 Whole rock geochemistry ...... 14 Svartliden gold mine ...... 15 Introduction ...... 15 Kinematic study...... 16 Discussion ...... 19 Geochemistry ...... 20 Classification...... 20 Mass balance calculations ...... 24 Raw data...... 30 Discussion ...... 37 Sjöliden...... 39 Introduction ...... 39 Structures...... 40 Thin sections ...... 41 PS049 ...... 41 Discussion ...... 43 Geochemistry ...... 43 Classification...... 43 Mass balance ...... 46 Discussion ...... 51 Grundfors ...... 52 Introduction ...... 52 Veins...... 54 Population 1 veins...... 54 Population 2 veins...... 54 Population 3 veins...... 55
3 Structures...... 55 Thin sections ...... 57 PS013A...... 57 PS014A...... 58 PS018B...... 59 PS019A...... 60 Discussion ...... 61 Geochemistry ...... 63 Classification...... 63 Mass Balance...... 66 Discussion ...... 68 The mylonite ...... 70 Introduction ...... 70 Structures...... 71 Discussion ...... 73 The granodiorite ...... 74 Introduction ...... 74 Structures...... 74 Discussion ...... 75 Discussion structures...... 76 Discussion geochemistry...... 79 Conclusions ...... 80 Acknowledgements ...... 82 References ...... 82 Software ...... 85 Appendices...... 86
4 Introduction
The main objectives of this study were to see what types of alterations and elemental changes accompany the deformation zones in the central part of Västerbotten, and to determine the kinematics involved. Västerbotten is best known for the Skellefte district with a number of operational mines. The Skellefte district is located approximately 140km east of the examined area. The study area lies within the gold line, which is a positive gold anomaly in glacial till striking NW SE, and hosts several orogenic gold deposits (Figure 1). Therefore the area is highly interesting from an exploration point of view. Bothnian basin metasediments and granitic intrusions dominate the area but metavolcanics and mafic intrusions are also present (figure 2). Five locations for the kinematic study and three for the geochemical study were chosen within the area formed by the triangle of Storuman, Vilhelmina and Lycksele. These include a road cut by the hydro power dam in Grundfors, the Svartliden gold mine, Sjöliden ~19km north of Svartliden, a mylonite ~4.5km ENE of Grundfors, and a granodiorite ~7.5 km northwest of Grundfors, whereas two of them, the road cuts in Grundfors and Svartliden were studied more thoroughly. Three of the localities lie along a geophysical magnetic anomaly connected to a number of known mineralizations. The anomaly follows the margins or goes through a series of granitic intrusions (Figure 2). The anomaly goes through Fäboliden in the south, a known gold mineralization, continues NNW through Svartliden, a mine in operation, and continues through Sjöliden and then through Grundfors where it joins a greater geophysical anomaly. The fourth locality is a mylonitizised metasedimentary succession, referred to as “the mylonite” in this paper, comprising homogenous metasandstones and layered metaargillites. The outcrops are located approximately 6 km northeast of Grundfors. The fifth locality, a granodioritic intrusion, is located about 2 kilometers west of the northern part of the anomaly. All five localities are within shear zones and few studies have been undertaken in the area previously. The locations were mapped, both structurally and for alterations. Structural measurements were taken as well as oriented samples for thin sections. Microstructures and mineralogy was determined from thin sections. Whole rock analysis was performed and used for the alteration study.
5 This study indicates that several deformational events, strike slip, reverse and normal shearing, have affected the area. Silicification is the most prominent alteration and is present in three localities. One locality indicates an extreme mass gain due to silicification.
Figure 1. The gold line as defined by the gold anomaly in glacial till, cutting through the central part of Västerbotten. Slightly modified from Bark, 2008.
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Figure 2. Left: Geological map of the study area. The studied localities are marked 1-5. 1=Svartliden gold mine, 2=Sjöliden, 3=Grundfors, 4=”The mylonite”, 5=”The granodiorite”. Right: Airborne geomagnetic map of the same area. Three of the localities are located within the anomaly.
7 Geological setting
Regional geology
The study area belongs to the Fennoscandian shield with continental crust formed under four stages of differing age (Gaál and Gorbatschev 1987). The basement is comprised of archean tonalites and trondhjemites formed during the Saamian orogeny at 3.1 2.9 Ga. The next stage includes the formation of high grade gneisses and the intrusion of granitoids as well as greenstones. This stage, the Lopian orogeny, occurred during 2.9 2.6 Ga. The third stage was during the Svecokarelian orogeny and during this stage the bulk of the present crust was formed (Gaál and Gorbatschev 1987). During this period a northward subduction took place south of the present day Skellefte district (Lahtinen et al. 2008; Lahtinen et al. 2005; Nironen 1997; Weihed et al. 1992). According to Nironen (1997) the formation of a passive continental margin occurred at ~1.95 Ga forming the Bothnian basin where sedimentation took place, creating the metasediments, known as the Bothnian supergroup present in the study area and surroundings. The metasediments are locally intercalated with metavolcanics giving time markers within the supracrustal sequence. Two volcanic arcs collided with the archean craton during the Svecofennian orogeny, the Arvidsjaur Kiruna arc at ~1.875 Ga and the Skellefte arc shortly thereafter (Juhlin et al. 2002). After the first collision a northward subduction beneath the Skellefte arc took place (Juhlin et al. 2002). According to Welin (1986) the sedimentation process halted at ~1.86 Ga which complies roughly with Nironen (1997) who considered the closing time of the basin at 1.87 Ga. During subduction the resulting intrusions of granitoids are classified according to Claesson and Lundqvist (1995) and Gaál and Gorbatschev (1987) as early, late or post orogenic depending on the time of emplacement. The early orogenic intrusives spread from 1.89 Ga to 1.85. The Skellefte Härnö granite suite is interpreted as being late orogenic intrusions with emplacement ages between 1.84 1.81 Ga. Post orogenic intrusions include the Revsund granite (1.80 1.77) which is coeval with early formation of the Transscandinavian Igneous Belt (TIB). Early TIB granites include the Revsund, Sorsele, Adak, Edefors and the Ale suite and are by far the most extensive intrusive rocks in this part of Sweden. The fourth stage in crust formation occurred during 1.75 1.5 Ga and is named the Gothian orogeny (Gaál,
8 Gorbatschev, 1987). Rocks formed during this period are present further south in Sweden and are not present where the study was carried out.
Tectonic setting and structural evolution
The Skellefte district, east of the study area, is believed to have formed at a convergent margin. A northward dipping marker was found under the Skellefte district with the aid of magnetotellurics and seismics (Rasmussen et al. 1987; BABEL group 1990). Alongside with this, granites hosting Mo W north of the Skellefte district, which are common for more intra plate subduction related intrusions, all indicate a northward subduction under the Skellefte arc at about 1.9 Ga (Weihed et al. 1992). Weihed et al. (1992) states that the high gold contents in the VMS ore and the primitive I type intrusives all point to an Island arc setting. Figure 3 show a possible tectonic interpretation of the area. Juhlin et al. (2002) created a model for the formation of the Skellefte district and surroundings (figure 4). This model show that at least two volcanic arcs collided with the Karelian craton to the north and a later eastward subduction was initiated after the collision. Two major deformational events have affected the Skellefte district as confirmed by Bergman Weihed (2001). The first event created tight to isoclinal folds with upright axial surfaces generally striking NW SE with fold axes showing a variably plunge. The second event formed open, NNE SSW striking folds with steep axial surfaces and coaxial fold axes relative to the early folds (Weihed et al. 1992; Bergman Weihed 2001). The first event was active between 1.85 1.84 Ga and is believed to be the result of oblique convergence from the southeast (Bergman Weihed 2001). The second deformation is accompanied with reverse dip slip shear zones striking north that indicate a crustal shortening in an east west direction. This event is contemporaneous with the intrusion of the Revsund granites which are believed to have been emplaced during an eastward subduction (Juhlin et al. 2002; Weihed et al. 2005). Gold deposits in the area are mainly orogenic in origin. Fäboliden, Svartliden, Stortjärnhobben and Barsele are known orogenic gold deposits within the gold line (Bark and Weihed 2007). The gold deposits were formed during crustal shortening at 2.72 2.67, 1.90 1.86 and 1.85 1.79 Ga (Weihed et al. 2005). The Björkdal orogenic gold deposit in the easternmost part of the Skellefte
9 district is interpreted to have formed at 1.88 Ga due to a major uplift in the area (Billström et al. 2009) while the Fäboliden orogenic gold deposit formed during the last crustal shortening event (Weihed et al. 2005; Bark and Weihed 2007). The gold line has undergone metamorphism peaking at mid amphibolite facies (Bark and Weihed, 2007)
Figure 3. Tectonic interpretation of the Skellefte district and surroundings. From Weihed et al. 1992.
Regional alterations
Alterations accompanied by shear zones are poorly investigated in the area except for the Skellefte district where the alterations are usually accompanied with ore formation. The most prominent alterations are of feldspar to chlorite and sericite which seem to be present in the Skellefte district as well as in other metavolcanics intercalated in the Bothnian supergroup metasediments (Bergman Weihed, 2001; Hallberg 2001; Kathol and Weihed, 2005; Barrett et al. 2005). As reported by Bergman Weihed (2001) an alteration from feldspar to epidote and calcite are present in shear zones in Bure which is localized approximately 50 km north of Grundfors. The Fäboliden hypozonal orogenic gold
10 deposit, located SE of the study area (figure 1), show a proximal skarn and biotite alteration and a gradual decrease in alteration intensity further away from the shear zone (Bark and Weihed 2007) The same alterations are present in the Svartliden mine.
Figure 4. Tectonic model as interpreted from geophysical data by Juhlin et al. (2002).
11 Studied localities
The Svartliden goldmine is located at point 1 in figure 2. The deposit is classified as a shear zone hosted orogenic gold deposit (Bark and Weihed, 2008). The shear zone is sub vertical and strikes ENE WSW. The main lithologies here are amphibolites intercalated with metagreywackes and Skellefte Härnö granites (Joel Andersson, personal communication 2011). Alterations in the mine include silicification, skarn alteration and biotitization. This locality was used in both the kinematic and alteration study. The Sjöliden outcrops are located at point 2 in figure 2 and both kinematics and alterations was studied in here. The outcrops here expose a N S trending shear zone hosted by a felsic metavolcanics rock surrounded by metagreywackes. In the immediate vicinity of the felsic metavolcanics, a small body of a mafic metavolcanic is present. The area is rich in quartz veins and has experienced some skarn alteration. The road cut in Grundfors (point 3 in figure 2) exposes a NW SE trending shear zone. The shear zone is hosted by a metabasalt surrounded by metagreywackes and Revsund granites. The shear zones are composed of several individual branches with variable dips. Silicified areas are present and are the most prominent type of alteration. A good exposure made it possible to do both kinematic and alteration studies. The mylonite outcrops are located at point 4 in figure 2. The shear zone in this area strikes NW SE and lithologies grade from sandy metasediments to metagreywackes. No prominent alterations are present and the locality was used for the kinematic study only. “The granodiorite” is located at point 5 in figure 2. The shear zones here strikes NW SE and ENE WSW. Poor exposure of the area made it hard to do any field observations regarding alterations and macrostructures so only the kinematic study was performed with the aid of thin sections. The granodiorite has been intruded by two small mafic bodies and is surrounded by metagreywackes.
Methods
Mapping
During field work in the summer of 2010 several promising localities were chosen for the study. Later, during the fall the same year, five days was spent in the field mapping these
12 localities. Two profiles from two outcrops were created from the road cut in Grundfors. The main objective was to map the structures as well as major alteration zones and rock type. The shear zones were examined in detail to find macroscopic shear sense indicators. Sjöliden and the mylonite were mapped in the same sense but due to the shape of the outcrops it was not possible to create any continuous profiles. Photos and sketches were taken/done over interesting features. Foliation and lineation measurements were taken where possible and stereoplots were created using Georient. Structural measurements were collected, as well as shown in the following text, in “strike/dip” format using the right hand rule.
Thin Section studies
The oriented samples were cut with a diamond blade saw parallel to the lineation and across the foliation. If no lineation was determined, two different sections were cut, one parallel to the closest observed lineation and one perpendicular to the first cut. Samples that were not oriented were cut approximately perpendicular to foliation to get an as representative section as possible. 37 thin sections whereof five oriented were manufactured from several lithologies in the Svartliden gold mine. From the road cut in Grundfors 14 thin sections, all oriented, were made. Eight oriented thin sections were made from the Sjöliden samples. Two oriented thin sections from the mylonite and another three from the granodiorite were made which gives a grand total of 64 thin sections. The cut samples were sent to Quality Thin Sections in Arizona US where 24x46mm 30 m polished thin sections were manufactured. The oriented samples were marked with a cut mark in the top right corner as an indicator of the orientation.
Kinematics
The oriented thin sections were analyzed to find out the sense of shear within the shear zones. The sections were examined under polarizing microscope and potential indicators were identified. These include rotated clasts, oblique foliation, en echelon veining and C` type shear bands. Apart from ductile indicators, brittle deformation structures were observed in several thin sections.
13 Alterations
For the alteration study the mineralogy of the thin sections was determined with the aid of a polarizing microscope. Mineralogy combined with textural relationship of the minerals in the thin section was the main principle used to determine alterations. Several different rock types were examined.
Whole-rock geochemistry
Totally 50 samples were sent for whole rock analysis at ALS Minerals, Piteå, including 30 samples from Svartliden in different lithologies, 15 samples from Grundfors and 5 samples from Sjöliden. Elements analyzed can be seen in table 1 (results can be found in Appendix 1). From the resulting data, immobile mobile, discrimination and mass balance diagrams were created. Discrimination diagrams were made using Petrograph 1.0.5. The immobile mobile plots give an indication of possible precursors to the altered rocks while the discrimination diagrams show rock type and possible formation environment. Mass balance diagrams were used to see element and mass changes.
Major Elements Base metals Trace elements REE Volatiles Si Al Ag Cd Ba Cr Y La As Bi Fe Ca Co Cu Cs Ga Ce Pr Hg Sb Mg Na Mo Ni Hf Nb Nd Sm Se Te K Ti Pb Zn Rb Sn Eu Gd Mn P Sr Ta Tb Dy C S Transition metals Th Tl Ho Er LOI Au U V Tm Yb W Zr Lu Table 1. Elements analyzed for whole-rock geochemistry.
14 Svartliden gold mine
Introduction
Among all promising gold prospect within the gold line, Svartliden is currently the only mine in operation. It is classified as a shear zone hosted orogenic gold deposit. The main rock type is amphibolite with intercalated metagreywackes, Skellefte Härnö granite (Joel Andersson, personal communication 2011) and ultramafic rocks. The granitic units will be excluded from this study. The grain size of the amphibolite varies. Therefore the amphibolites are divided into one coarse and one fine grained group. The metagreywackes are separated into biotite schist, quartz biotite schist, and sulphide graphite bearing schist. At surface level the sulphide graphite bearing schist generally occurs north of the mineralization while both the biotite schist and quartz biotite schist occur south of it (Figure 5). The ore itself is composed of a silicified unit with pyrrhotite and arsenopyrite as the main sulphides, along with gold. Skarn alteration and skarn veining occur in the amphibolite and to some extent in the metagreywackes and ore. The shear zone strikes ENE and cuts through the mine. The mine itself is located at the same geophysical anomaly as both Sjöliden and Grundfors to the north and the Fäboliden orogenic gold deposit in the south. This study will be based on samples collected from drill core along a profile from the western part of the mine (Figure 5). Eight samples from the fine grained amphibolite, two samples from the coarse grained amphibolite, two from the ultramafic rocks, three from the quartz biotite schist, four from the biotite schist, six from the sulphide graphite bearing schist, four samples from the ore and one sample from the shear zone was prepared for thin sections and geochemically analyzed.
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Figure 5. Geological map of the western part of the Svartliden gold mine. Data for this project was collected from the marked profile.
Kinematic study
The shear zone is sub vertical striking ENE through the mine. Five oriented thin sections were made, three sections from the biotite schist in contact with the shear zone and two sections from the shear zone itself (Figure 6). Reliable shear sense indicators were scarce which make the confidence in the interpretation low. Sample SV002B show a deformed quartz vein along the sub vertical main foliation (Figure 7). The veins display tension gashes which indicate a compressive regime with a south side up shear sense. Figure 8 display possible stair stepping in sample SV003A, which in this case would indicate a sinistral sense of shear. However the two horizons composed of sulphides might be unrelated which in turn makes this interpretation uncertain.
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Figure 6. Drill holes from the profile chosen with a possible geological interpretation. Underlined samples indicate thin section only. The others are thin section + whole rock analyzed. View towards west.
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Figure 7. Deformed quartz veins along the main foliation indicating a south-side-up sense of movement. Vertical section with north as indicated. Viewed towards west.
Figure 8. Horizontal sample showing a sigma-clast with possible stair stepping. The black horizons are composed of sulphides. The two horizons might be unrelated so the validity of a sinistral sense of shear is uncertain.
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Discussion
The samples collected were not optimal for the kinematic study. The lack of reliable shear sense indicators makes it hard to draw any confident conclusions. The Fäboliden deposit southeast of the mine is reported as being a hypozonal orogenic gold deposit. The appearance of Fäboliden and Svartliden are similar. Both are shear zone hosted, and occur in metagreywackes, the accompanying biotite and skarn alteration is present in both deposits. However the shear zone of Fäboliden strikes roughly N S and is interpreted as a reactivated high angle reverse dip slip zone (Bark, 2008). The shear zone in Svartliden is clearly a sub vertical shear zone but strikes ENE WSW and has reverse kinematics. The gold is quartz vein hosted in Fäboliden whereas in Svartliden it is hosted by a silicified unit. The quartz veins hosting the gold and the shear zone in Fäboliden have, according to Bark (2008) formed during an east west compressive regime at ~1.80. Skyttä et al. (2010) reports from the Skellefte district that ~E W striking reverse dip slip faults formed during the N S compressive regime at ~1.875 1.80 Ga. During the emplacement of the Revsund granite ~N S striking reverse dip slip faults were formed (Bergman Weihed, 2001) with a possible reactivation of the Svartliden shear zone with a strike slip movement. If a strike slip movement occurred during east west compression, the formation of the Svartliden shear zone might be contemporaneous with emplacement of the Revsund granite and not a reactivated older structure. Rutland et al. (2001) reported that the E W compressive event might have started as early as 1.81 Ga creating NNW striking shear zones. Since the emplacement of the Revsund granite occurred at 1.80 1.77 (Claesson and Lundqvist, 1995), the possibility of a E W compression predating the intrusions of the Revsund granites are possible. Since no field data was gathered for this locality no measurements of possible lineations have been done. The thin sections show no reliable shear sense indicators. If figure 7 can be trusted a south side up movement has occurred. The south side up movement, together with the knowledge from the Fäboliden deposit makes the scenario of a reverse dip slip movement plausible which in turn would indicate movement during a compressive regime. Rutland et al. (2001) suggested that older basement structures were reactivated west of the Vindeln lineament (approximately 85 km east of the study area) during the E W compressional event. The shear sense might be
19 unclear of the Svartliden shear zone, but the reactivation of an older structure is deemed most likely and probably with an early reverse dip slip movement (Figure 7) and a possible later dextral strike slip movement (Figure 8).
Geochemistry
Classification
The lithologies of the Svartliden gold mine were plotted in several different classification diagrams. The amphibolites and the ultramafic unit plot as basalt in Cox Bell Pank’s (1979) classification system (Figure 9a). When plotted according to LeBas et al. (1986) the ultramafics plot as picrobasalt while the amphibolite unit plot as basalt (Figure 9b). One sample, SV067, mapped as an amphibolite also plot as picrobasalt. The sample show elevated Cr values (550 ppm) and is interpreted as having a mafic ultramafic composition. In AFM plots based on Irvine and Baragar (1971) and Kuno (1968) they plot in the tholeiitic field (Figure 10a and 10b). Tectonic discrimination diagrams indicate a mid ocean ridge basalt affinity for the majority of samples, however similarities to volcanic arc tholeiites are also indicated (Figure 11a b). The ultramafic unit shows a rather erratic behavior and plots as within plate basalt and as mid ocean ridge basalt in different diagrams. The amphibolite consequently plot as a MORB and island arc tholeiite. The amphibolite is generally sulphide poor and not gold bearing but one sample shows an anomalous Au value of 0.146 ppm (Table 2 and appendix 1).
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Figure 9a. Classification according to Cox-Bell-Pank (1979). Triangles = ultramafic unit, Boxes = fine grained amphibolite, Circles = coarse grained amphibolite.
Figure 9b. Rock classification according to LeBas et al. (1986). Triangles = ultramafic unit, Boxes = fine grained amphibolite, Circles = coarse grained amphibolite.
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Figure 10. Amphibolite samples plotted in AFM diagrams. (a) AFM plot from Irvine-Baragar (1971). (b) AFM plot from Kuno (1968). Both diagrams show a tholeiitic affinity.
Figure 11. Tectonic discrimination diagrams for the amphibolites and the ultramafic unit.
The metasediments are classified as metagreywackes and lithic arkoses (Figure 12a) according to Blatt et al. (1980) and Blatt, 1992. The sulphide, graphite bearing schist plots in the greywacke field while the quartz biotite schist plots in both the greywacke and lithic arkose fields. The biotite schist samples all plot in the lithic arkose field. A second classification diagram (Figure 12b) based on Pettijohn et al. (1973) show that all samples plot within the greywacke field. The sources for the sediments show a nice grouping depending on lithology. Two diagrams by Roser and Korsch (1986) and Maynard et al. (1982) yield the same result for the quartz biotite schist that plots within the active continental margin source field. The sulphide, graphite bearing schist and the biotite schist plot, in the first case, both in the evolved arc setting and in the active
22 continental margin field while in the latter case it plots in the oceanic island arc margin field (Figure 13a and 13b). The discrimination diagram (Figure 14) by Floyd and Leveridge, (1987) indicate that the biotite schist is derived from a tholeiitic oceanic island arc, while both the quartz biotite schist and the sulphide, graphite bearing schist plot within the acid arc source field. The silica content in the quartz biotite schist (64 74%) can be related to a more acid source while the biotite schist, which is more mafic in character, has an oceanic island arc source. The sulphide, graphite bearing schist with its relatively high silica and carbon content indicates a crustal source. Two samples logged as biotite schist has been reclassified. The geochemical data for SV036 suggest a crustal source due to its high SiO 2 content (73.9%) and as it has a close relationship to the quartz biotite schist in the diagrams it was reclassified as that. Abundant sulphides and graphite are generally constrained to the sulphide, graphite bearing schist and sample SV071 have a high carbon (>5%) and sulfur content and plots together with the sulphide, graphite bearing schist samples, hence it is reclassified as an sulphide, graphite bearing schist.
Figure 12. Classification of the metasediments according to Blatt et al. (1980); Blatt, 1992; Pettijohn et al. 1973). Legend for a) Triangles = Sulphide, graphite bearing schist. Circles = Biotite schist. Boxes = Quartz biotite schist.
23 Figure 13. Sources for the metasediments based on Roser and Korsch (1986) and Maynard et al. (1982). The quartz biotite schist plot in the active continental margin in both diagrams indicating an acid source. The sulphide, graphite bearing schist plot both in the evolved arc setting and active continental margin in figure a, while it plots in the oceanic island-arc margin in figure b. The biotite schist plots in the same manner as the sulphide, graphite bearing schist.
Figure 14. Tectonic discrimination diagram from Floyd and Leveridge (1987). The biotite schist plot in the oceanic island-arc field while both the sulphide, graphite bearing schist and the quartz biotite schist plot in the acid-arc source.
Mass balance calculations
The ore in the mine is thought to be a silicified metasedimentary unit based on the data in this study. The immobile element plots (Figure 15) show a clear linear relationship of the ore, shear zone, sulphide, graphite bearing schist and the quartz biotite schist. The amphibolite units and the ultramafics along with the biotite schist form another trend,
24 thus indicating a different source which was clearly seen in the discrimination plots (Figure 12, 13 and 14). One could argue that the biotite schist and amphibolite units could be the source for two of the ore samples and the shear zone sample (Figure 15). When mass balance calculations were done for these samples it clearly show that the immobile elements plot erratically which would mean that the amphibolite and biotite schist can not be the source since the immobile elements are assumed to have been immobile. The mass balance calculations are based on MacLean and Barrett (1993)´s technique but using
Al 2O3 instead of Zr. Table 2 show that the mass gain ranges between 2 48 times the original mass which is extremely high. The average mass gain from this profile is ~1900%. A possible precursor of the ore was determined to be SV036. This is based on the high initial silica content and the homogenous behavior of the immobile elements.
The mass balance diagrams (Figure 16) show a gain of most elements while Na 2O, K 2O, Ba and Rb are the main losses. The losses are probably due to the breakdown of the micas and feldspars present in the precursor. Another visible trend is the increase in rare earth elements when total SiO 2 content decreases. The precipitation of diopside gives the increase in CaO. The strong addition of silica and dilution of immobile elements give an extreme mass gain (Table 2) and hence a big volume increase. The increase in metals and sulfur is due because of sulphide precipitation.
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4 QBS 3,5 SBS 3 SNS 2,5 SSK 2 SZ TiO2 VA 1,5 VB 1 VU 0,5 0 0 50 100 150 200 250 Zr 4 QBS 3,5 SBS 3 SNS 2,5 SSK 2 SZ TiO2 VA 1,5 VB 1 VU 0,5 0 0 2 4 6 8 10 12 Th 250 QBS SBS 200 SNS SSK 150 SZ Zr VA 100 VB
50 VU
0 0 2 4 6 8 10 12 Th Figure 15. Immobile element plots showing the linear trend between the ore, shear zone, quartz biotite schist and the sulphide, graphite bearing schist.
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Figure 16. Mass balance diagrams of the precursor and the ore samples. The immobile elements show a homogenous behavior indicating that SV036 is a possible precursor.
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wt% Table 2. Raw data of the Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 samples and calculated SV059 Altered 92,60 0,01 0,48 0,88 5,09 0,01 0,34 0,01 0,02 0,02 1,18 100,64 Rcex (Al2O3) 2199,25 0,24 11,40 20,90 120,89 0,24 8,08 0,24 0,48 0,48 28,03 reconstituted compositions Mass change 2125,35 -0,29 0,00 19,94 116,67 -2,05 6,48 -3,21 0,44 0,37 26,45 2290,12 SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 based on Maclean and SV055 Altered 75,60 0,19 1,74 11,10 7,44 0,01 1,74 0,06 0,16 0,99 2,08 101,11 Barrett (1993)´s method. Rcex (Al2O3) 495,31 1,24 11,40 72,72 48,74 0,07 11,40 0,39 1,05 6,49 13,63 Mass change 421,41 0,71 0,00 71,76 44,52 -2,22 9,80 -3,06 1,01 6,38 12,05 562,36 The extreme mass gain is SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV050 Altered 40,80 0,16 2,08 16,00 24,80 0,43 7,71 0,08 0,25 0,77 5,53 98,61 evident in sample SV059, Rcex (Al2O3) 135,15 0,53 6,89 53,00 82,15 1,42 25,54 0,27 0,83 2,55 18,32 Mass change 61,25 0,00 -4,51 52,04 77,93 -0,87 23,94 -3,19 0,79 2,44 16,74 226,57 SV048 and SV017. SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV048 Altered 47,50 0,02 0,60 3,87 40,20 0,05 2,43 0,07 0,32 0,76 3,99 99,81 Rcex (Al2O3) 902,50 0,38 11,40 73,53 763,80 0,95 46,17 1,33 6,08 14,44 75,81 Mass change 828,60 -0,15 0,00 72,57 759,58 -1,34 44,57 -2,12 6,04 14,33 74,23 1796,31 SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV017 Altered 86,70 0,01 0,23 6,86 2,76 0,01 1,60 0,02 0,08 0,16 0,60 99,03 Rcex (Al2O3) 4297,30 0,50 11,40 340,02 136,80 0,50 79,30 0,99 3,97 7,93 29,74 Mass change 4223,40 -0,03 0,00 339,06 132,58 -1,79 77,70 -2,46 3,93 7,82 28,16 4808,36 wt% ppm Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV059 Altered 1,70 0,08 4,00 45,10 0,80 0,21 0,58 8,00 0,40 1,60 Rcex (Al2O3) 40,38 1,90 95,00 1071,13 19,00 4,99 13,78 190,00 9,50 38,00 Mass change 39,69 1,33 -514,00 959,13 -186,00 -5,01 10,37 -10,00 4,00 23,40 SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV055 Altered 0,28 2,10 0,80 44,70 0,50 1,58 3,98 39,00 1,40 4,50 Rcex (Al2O3) 1,83 13,76 5,24 292,86 3,28 10,35 26,08 255,52 9,17 29,48 Mass change 1,14 13,19 -603,76 180,86 -201,72 0,35 22,67 55,52 3,67 14,88 SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV050 Altered 5,24 3,16 67,80 58,70 25,90 1,32 25,70 44,00 1,60 5,50 Rcex (Al2O3) 17,36 10,47 224,59 194,44 85,79 4,37 85,13 145,75 5,30 18,22 Mass change 16,67 9,90 -384,41 82,44 -119,21 -5,63 81,72 -54,25 -0,20 3,62 SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV048 Altered 11,75 0,07 17,10 72,90 1,50 0,22 0,46 6,00 0,20 2,00 Rcex (Al2O3) 223,25 1,33 324,90 1385,10 28,50 4,18 8,74 114,00 3,80 38,00 Mass change 222,56 0,76 -284,10 1273,10 -176,50 -5,82 5,33 -86,00 -1,70 23,40 SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV017 Altered 0,25 0,23 0,90 31,40 1,20 0,16 2,98 9,00 0,20 1,00 Rcex (Al2O3) 12,39 11,40 44,61 1556,35 59,48 7,93 147,70 446,09 9,91 49,57 Mass change 11,70 10,83 -564,39 1444,35 -145,52 -2,07 144,29 246,09 4,41 34,97
28
ppm Table 2. Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 Continued. SV059 Altered 1,30 1,60 1,40 0,23 0,80 0,17 0,06 0,19 0,03 0,17 0,04 0,13 0,03 0,14 0,02 Rcex (Al2O3) 30,88 38,00 33,25 5,46 19,00 4,04 1,43 4,51 0,71 4,04 0,95 3,09 0,71 3,33 0,48 Mass change 8,58 8,00 -28,35 -1,72 -6,30 -1,32 0,41 -0,16 0,05 0,06 0,18 0,87 0,37 1,24 0,16 SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV055 Altered 28,10 13,00 19,20 3,91 16,50 4,39 1,03 5,06 0,69 4,13 0,84 2,34 0,32 1,85 0,29 Rcex (Al2O3) 184,10 85,17 125,79 25,62 108,10 28,76 6,75 33,15 4,52 27,06 5,50 15,33 2,10 12,12 1,90 Mass change 161,80 55,17 64,19 18,44 82,80 23,40 5,73 28,48 3,86 23,08 4,73 13,11 1,76 10,03 1,58 SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV050 Altered 27,30 15,60 22,30 3,25 12,30 3,07 0,66 3,86 0,58 3,88 0,80 2,27 0,35 2,22 0,34 Rcex (Al2O3) 90,43 51,68 73,87 10,77 40,74 10,17 2,19 12,79 1,92 12,85 2,65 7,52 1,16 7,35 1,13 Mass change 68,13 21,68 12,27 3,59 15,44 4,81 1,17 8,12 1,26 8,87 1,88 5,30 0,82 5,26 0,81 SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV048 Altered 16,00 7,90 7,20 1,67 6,50 1,62 0,50 2,08 0,30 2,00 0,44 1,30 0,19 1,19 0,19 Rcex (Al2O3) 304,00 150,10 136,80 31,73 123,50 30,78 9,50 39,52 5,70 38,00 8,36 24,70 3,61 22,61 3,61 Mass change 281,70 120,10 75,20 24,55 98,20 25,42 8,48 34,85 5,04 34,02 7,59 22,48 3,27 20,52 3,29 SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV017 Altered 8,20 4,80 8,40 1,23 5,50 1,36 0,24 1,66 0,27 1,69 0,32 0,89 0,11 0,81 0,12 Rcex (Al2O3) 406,43 237,91 416,35 60,97 272,61 67,41 11,90 82,28 13,38 83,77 15,86 44,11 5,45 40,15 5,95 Mass change 384,13 207,91 354,75 53,79 247,31 62,05 10,88 77,61 12,72 79,79 15,09 41,89 5,11 38,06 5,63 ppm Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV059 Altered 70,60 0,06 0,17 3,00 360,00 0,22 109,00 0,40 15,00 2,00 2,10 2,00 0,08 5,00 12,00 Rcex (Al2O3) 1676,75 1,40 4,04 71,25 8550,00 5,23 2588,75 9,50 356,25 47,50 49,88 47,50 1,90 118,75 285,00 Mass change 1672,95 1,39 3,89 60,25 8260,00 -31,78 2553,75 0,20 318,25 34,50 48,68 29,50 1,87 31,75 214,00 SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV055 Altered 64,90 0,01 0,05 14,00 250,00 0,07 49,00 2,50 48,00 2,00 0,90 13,00 0,02 109,00 59,00 Rcex (Al2O3) 425,21 0,08 0,33 91,72 1637,93 0,46 321,03 16,38 314,48 13,10 5,90 85,17 0,13 714,14 386,55 Mass change 421,41 0,06 0,18 80,72 1347,93 -36,54 286,03 7,08 276,48 0,10 4,70 67,17 0,10 627,14 315,55 SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV050 Altered 132,00 1,04 0,96 1,00 180,00 4,87 133,00 1,50 28,00 15,00 12,40 3,00 0,43 94,00 133,00 Rcex (Al2O3) 437,25 3,45 3,18 3,31 596,25 16,13 440,56 4,97 92,75 49,69 41,08 9,94 1,42 311,38 440,56 Mass change 433,45 3,43 3,03 -7,69 306,25 -20,87 405,56 -4,33 54,75 36,69 39,88 -8,06 1,39 224,38 369,56 SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV048 Altered 250,00 0,66 0,78 1,00 130,00 0,44 503,00 0,50 65,00 6,00 13,30 2,00 1,31 27,00 89,00 Rcex (Al2O3) 4750,00 12,48 14,82 19,00 2470,00 8,36 9557,00 9,50 1235,00 114,00 252,70 38,00 24,89 513,00 1691,00 Mass change 4746,20 12,47 14,67 8,00 2180,00 -28,64 9522,00 0,20 1197,00 101,00 251,50 20,00 24,86 426,00 1620,00 SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV017 Altered 61,00 <0,005 0,10 5,00 150,00 0,14 88,00 0,50 12,00 <2 0,70 1,00 0,02 20,00 39,00 Rcex (Al2O3) 3023,48 0,00 4,96 247,83 7434,78 6,94 4361,74 24,78 594,78 0,00 34,70 49,57 0,99 991,30 1933,04 Mass change 3019,68 4,81 236,83 7144,78 -30,06 4326,74 15,48 556,78 33,50 31,57 0,96 904,30 1862,04
29
Raw data
When raw data are plotted over the profile several trends are visible. The amphibolite (Figure 17) show no increase or decrease close to the ore in any of the involved elements. The amphibolite samples occur between the ore samples which give the plot a spiky appearance where the value for an element decrease or increase sharply when an ore sample is plotted. When the neighboring amphibolite sample is plotted the value goes back to the general amphibolite value. The only element that shows an increase closer to the ore is arsenic. The value does not stay consequently high within the amphibolite samples intercalated with the ore. The sediments (Figure 18) on the other hand show both an increase and decrease in different elements closer to the ore. The silica for example show a clear decreasing trend until it hits the ore where it sharply rises. The same goes for sodium, a gradual decrease towards the ore, except here no peak within the ore is present where the sodium concentration is very low. Potassium shows a sharp increase in the metasediments right next to the ore. In the ore however there is a very low concentration of K 2O which is seen in the diagram. Sulfur shows a rather erratic behavior with one pronounced peak in one ore sample. The samples with silica loss close to the ore show a mass loss of up to 43% (Table 3).
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Figure 17. Plots of several major elements along with Au and As from the amphibolite and ore. View towards west.
31
Figure 18. Major elements along with Au and As from the metasediments and ore plotted over the profile. View towards west.
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wt% Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV031 Altered 66,50 0,74 14,15 1,64 7,59 2,97 3,08 2,37 0,06 0,14 1,49 100,73 Rcex (Al2O3) 53,58 0,60 11,40 1,32 6,11 2,39 2,48 1,91 0,05 0,11 1,20 Mass change -20,32 0,07 0,00 0,36 1,89 0,10 0,88 -1,54 0,01 0,00 -0,38 -18,93 Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV025 Altered 47,40 1,62 20,20 4,02 12,95 5,68 3,78 2,60 0,15 0,11 1,79 100,30 Rcex (Al2O3) 26,75 0,91 11,40 2,27 7,31 3,21 2,13 1,47 0,08 0,06 1,01 Mass change -47,15 0,38 0,00 1,31 3,09 0,92 0,53 -1,98 0,04 -0,05 -0,57 -43,48 Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV060 Altered 49,80 1,39 16,90 5,81 8,83 4,45 7,12 0,84 0,10 0,09 3,48 98,81 Rcex (Al2O3) 33,59 0,94 11,40 3,92 5,96 3,00 4,80 0,57 0,07 0,06 2,35 Mass change -40,31 0,41 0,00 2,96 1,74 0,71 3,20 -2,88 0,03 -0,05 0,77 -33,43 Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV063 Altered 49,00 3,70 14,50 5,46 11,70 2,74 7,26 2,76 0,13 0,11 1,39 98,75 Rcex (Al2O3) 38,52 2,91 11,40 4,29 9,20 2,15 5,71 2,17 0,10 0,09 1,09 Mass change -35,38 2,38 0,00 3,33 4,98 -0,14 4,11 -1,28 0,06 -0,02 -0,49 -22,44 Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV035 Altered 57,90 0,64 11,80 2,32 10,85 1,92 3,14 2,54 0,04 0,11 8,10 99,36 Rcex (Al2O3) 55,94 0,62 11,40 2,24 10,48 1,85 3,03 2,45 0,04 0,11 7,83 Mass change -17,96 0,09 0,00 1,28 6,26 -0,44 1,43 -1,00 0,00 0,00 6,25 -4,09 Sample Mass calculation SiO2 TiO2 Al2O3 CaO Fe2O3 K2O MgO Na2O MnO P2O5 LOI Sum SV036 Precursor 73,90 0,53 11,40 0,96 4,22 2,29 1,60 3,45 0,04 0,11 1,58 100,08 SV052 Altered 53,00 0,78 11,45 5,30 9,49 1,07 6,58 2,44 0,12 0,11 4,91 95,25 Rcex (Al2O3) 52,77 0,78 11,40 5,28 9,45 1,07 6,55 2,43 0,12 0,11 4,89 Mass change -21,13 0,25 0,00 4,32 5,23 -1,22 4,95 -1,02 0,08 0,00 3,31 -5,25 Table 3. Raw data and reconstituted composition for the samples close to the ore, indicating a mass loss.
33
wt% ppm Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV031 Altered 0,12 0,55 425,00 138,00 164,50 9,38 3,23 164,00 4,50 18,30 Rcex (Al2O3) 0,10 0,44 342,40 111,18 132,53 7,56 2,60 132,13 3,63 14,74 Mass change -0,59 -0,13 -266,60 -0,82 -72,47 -2,44 -0,81 -67,87 -1,87 0,14 Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV025 Altered 1,66 0,24 830,00 179,00 164,00 0,33 0,17 90,00 2,60 23,50 Rcex (Al2O3) 0,94 0,14 468,42 101,02 92,55 0,19 0,10 50,79 1,47 13,26 Mass change 0,25 -0,43 -140,58 -10,98 -112,45 -9,81 -3,31 -149,21 -4,03 -1,34 Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV060 Altered 0,06 0,43 399,00 139,50 291,00 0,32 0,52 76,00 2,40 22,90 Rcex (Al2O3) 0,04 0,29 269,15 94,10 196,30 0,22 0,35 51,27 1,62 15,45 Mass change -0,65 -0,28 -339,85 -17,90 -8,70 -9,78 -3,06 -148,73 -3,88 0,85 Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV063 Altered 1,67 0,07 1330,00 126,50 88,10 1,02 0,90 158,00 4,90 30,40 Rcex (Al2O3) 1,31 0,06 1045,66 99,46 69,26 0,80 0,71 124,22 3,85 23,90 Mass change 0,62 -0,51 436,66 -12,54 -135,74 -9,20 -2,70 -75,78 -1,65 9,30 Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV035 Altered 3,62 5,36 328,00 217,00 87,30 8,16 13,55 143,00 4,00 15,00 Rcex (Al2O3) 3,50 5,18 316,88 209,64 84,34 7,88 13,09 138,15 3,86 14,49 Mass change 2,81 4,61 -292,12 97,64 -120,66 -2,12 9,68 -61,85 -1,64 -0,11 Sample Mass calculation S C Ba Sr Rb Th U Zr Hf Ga SV036 Precursor 0,69 0,57 609,00 112,00 205,00 10,00 3,41 200,00 5,50 14,60 SV052 Altered 1,45 3,70 171,50 234,00 59,20 6,90 6,30 120,00 3,40 16,20 Rcex (Al2O3) 1,44 3,68 170,75 232,98 58,94 6,87 6,27 119,48 3,39 16,13 Mass change 0,75 3,11 -438,25 120,98 -146,06 -3,13 2,86 -80,52 -2,11 1,53 Table 3. Continued
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ppm Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV031 Altered 23,50 29,80 58,80 6,79 27,20 5,56 1,34 4,93 0,75 4,84 0,87 2,40 0,37 2,39 0,35 Rcex (Al2O3) 18,93 24,01 47,37 5,47 21,91 4,48 1,08 3,97 0,60 3,90 0,70 1,93 0,30 1,93 0,28 Mass change -3,37 -5,99 -14,23 -1,71 -3,39 -0,88 0,06 -0,70 -0,06 -0,08 -0,07 -0,29 -0,04 -0,16 -0,04 Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV025 Altered 19,80 4,00 10,70 1,66 9,00 2,94 0,90 3,35 0,61 4,15 0,80 2,29 0,34 2,34 0,34 Rcex (Al2O3) 11,17 2,26 6,04 0,94 5,08 1,66 0,51 1,89 0,34 2,34 0,45 1,29 0,19 1,32 0,19 Mass change -11,13 -27,74 -55,56 -6,24 -20,22 -3,70 -0,51 -2,78 -0,32 -1,64 -0,32 -0,93 -0,15 -0,77 -0,13 Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV060 Altered 21,70 4,30 11,50 1,80 8,80 3,20 1,35 4,31 0,71 4,39 0,87 2,41 0,36 2,07 0,31 Rcex (Al2O3) 14,64 2,90 7,76 1,21 5,94 2,16 0,91 2,91 0,48 2,96 0,59 1,63 0,24 1,40 0,21 Mass change -7,66 -27,10 -53,84 -5,97 -19,36 -3,20 -0,11 -1,76 -0,18 -1,02 -0,18 -0,59 -0,10 -0,69 -0,11 Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV063 Altered 17,50 13,50 35,00 5,17 22,70 6,33 1,71 6,13 0,81 4,35 0,72 1,75 0,23 1,27 0,18 Rcex (Al2O3) 13,76 10,61 27,52 4,06 17,85 4,98 1,34 4,82 0,64 3,42 0,57 1,38 0,18 1,00 0,14 Mass change -8,54 -19,39 -34,08 -3,12 -7,45 -0,38 0,32 0,15 -0,02 -0,56 -0,20 -0,84 -0,16 -1,09 -0,18 Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV035 Altered 28,50 27,90 55,10 6,59 26,50 5,71 1,30 5,39 0,88 5,64 1,08 3,10 0,47 3,20 0,51 Rcex (Al2O3) 27,53 26,95 53,23 6,37 25,60 5,52 1,26 5,21 0,85 5,45 1,04 2,99 0,45 3,09 0,49 Mass change 5,23 -3,05 -8,37 -0,81 0,30 0,16 0,24 0,54 0,19 1,47 0,27 0,77 0,11 1,00 0,17 Sample Mass calculation Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu SV036 Precursor 22,30 30,00 61,60 7,18 25,30 5,36 1,02 4,67 0,66 3,98 0,77 2,22 0,34 2,09 0,32 SV052 Altered 25,10 23,50 48,70 5,85 21,90 5,29 1,39 5,06 0,72 4,37 0,86 2,44 0,36 2,40 0,36 Rcex (Al2O3) 24,99 23,40 48,49 5,82 21,80 5,27 1,38 5,04 0,72 4,35 0,86 2,43 0,36 2,39 0,36 Mass change 2,69 -6,60 -13,11 -1,36 -3,50 -0,09 0,36 0,37 0,06 0,37 0,09 0,21 0,02 0,30 0,04 Table 3. Continued
35
ppm Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV031 Altered 18,60 0,01 0,27 21,00 280,00 7,68 81,00 10,10 79,00 28,00 0,90 2,00 0,03 134,00 118,00 Rcex (Al2O3) 14,99 0,00 0,22 16,92 225,58 6,19 65,26 8,14 63,65 22,56 0,73 1,61 0,02 107,96 95,07 Mass change 11,19 -0,01 0,07 5,92 -64,42 -30,81 30,26 -1,16 25,65 9,56 -0,47 -16,39 -0,01 20,96 24,07 Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV025 Altered >250 0,01 0,20 84,00 350,00 34,10 255,00 3,80 141,00 15,00 2,70 6,00 0,09 471,00 161,00 Rcex (Al2O3) #VALUE! 0,00 0,11 47,41 197,52 19,24 143,91 2,14 79,57 8,47 1,52 3,39 0,05 265,81 90,86 Mass change #VALUE! -0,01 -0,04 36,41 -92,48 -17,76 108,91 -7,16 41,57 -4,53 0,32 -14,61 0,02 178,81 19,86 Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV060 Altered 219,00 0,02 0,10 68,00 290,00 44,60 111,00 3,50 143,00 <2 0,70 6,00 0,04 482,00 125,00 Rcex (Al2O3) 147,73 0,02 0,07 45,87 195,62 30,09 74,88 2,36 96,46 #VALUE! 0,47 4,05 0,03 325,14 84,32 Mass change 143,93 0,00 -0,08 34,87 -94,38 -6,91 39,88 -6,94 58,46 #VALUE! -0,73 -13,95 0,00 238,14 13,32 Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV063 Altered 156,00 0,01 0,10 73,00 700,00 20,70 123,00 22,80 214,00 2,00 1,20 2,00 0,06 531,00 150,00 Rcex (Al2O3) 122,65 0,00 0,08 57,39 550,34 16,27 96,70 17,93 168,25 1,57 0,94 1,57 0,05 417,48 117,93 Mass change 118,85 -0,01 -0,07 46,39 260,34 -20,73 61,70 8,63 130,25 -11,43 -0,26 -16,43 0,02 330,48 46,93 Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV035 Altered 5,70 0,01 0,43 28,00 310,00 5,85 175,00 9,30 267,00 20,00 10,50 1,00 0,25 311,00 250,00 Rcex (Al2O3) 5,51 0,01 0,42 27,05 299,49 5,65 169,07 8,98 257,95 19,32 10,14 0,97 0,24 300,46 241,53 Mass change 1,71 -0,01 0,27 16,05 9,49 -31,35 134,07 -0,32 219,95 6,32 8,94 -17,03 0,21 213,46 170,53 Sample Mass calculation As Au Bi Co Cr Cs Cu Nb Ni Pb Se Sn Te V Zn SV036 Precursor 3,80 0,02 0,15 11,00 290,00 37,00 35,00 9,30 38,00 13,00 1,20 18,00 0,03 87,00 71,00 SV052 Altered 2,60 0,01 0,30 30,00 590,00 7,03 111,00 8,10 236,00 12,00 4,60 3,00 0,10 228,00 377,00 Rcex (Al2O3) 2,59 0,01 0,30 29,87 587,42 7,00 110,52 8,06 234,97 11,95 4,58 2,99 0,10 227,00 375,35 Mass change -1,21 -0,01 0,15 18,87 297,42 -30,00 75,52 -1,24 196,97 -1,05 3,38 -15,01 0,07 140,00 304,35 Table 3. Continued
36
Discussion
The tectonic discrimination diagrams clearly indicate two different sources for the metasediments. The biotite schist with its more mafic character (less SiO 2 and more biotite) have an oceanic island arc source while both the sulphide, graphite bearing schist and the quartz biotite schist seem to have a crustal margin source. The amphibolite seems to have intruded the metasediments and the presence of intercalated ultramafics indicates formation during an orogeny. This fits well with Svartliden being an orogenic gold deposit and the assumption of arc collisions that is reported to have occurred at ~1.87 Ga (Juhlin et al. 2002) during the Svecofennian orogeny. The linear trend between two of the metagreywackes and the ore indicates that the ore is hosted by a silicified metagreywacke. However, the extreme mass and consequential volume gain is hard to explain. Several studies indicate a mass and volume gain accompanied with silicification (Binns and Appleyard, 1986; Hippertt, 1998; Streit et al. 1998; Manikyamba et al. 2004) but the amount of mass gain generally does not exceed ~90%. In the case of Svartliden the mass gain is indicated to reach as much 4800%. If an average is calculated from the four ore samples including the shear zone (Table 2) the mass gain reaches 1900%. The close relationship to a shear zone might indicate silica being a fault infill giving the ore the necessary volume to expand. The Fäboliden deposit SE of Svartliden has fault fill and extensional quartz veins (Bark, 2008). This process might give an explanation to the volume needed to host the ore in Svartliden. The silicification of the protolith occurs and the expansion of the ore is allowed due to faulting and opening of extensional gashes during shearing. When raw data for the sediments along with the ore is plotted a clear relationship can be seen. SiO 2 seem to decrease in the sediments towards the ore. The ratio between SiO 2/Al 2O3 shows an inverse behavior indicating silica depletion closer to the ore. This relationship is true for Al 2O3 and TiO 2 but not for Zr. This indicates that some of the silica in the ore comes from the sediments. The loss of silica from the metasediments neighboring the ore indicates a volume loss, hence making the volume gain of the ore plausible. Another explanation would be another protolith. An already immobile element diluted sediment from the same source as the quartz biotite schist would give a lower mass gain and hence a lower volume gain.
37
The loss and gain for the different elements are fairly straightforward. Among the major elements the gain of SiO 2 is due because of silicification, gain of Fe 2O3 due to sulphide and iron oxide precipitation. The gain of MgO and MnO might be due to the formation of amphiboles and diopside. The loss of Na 2O and K 2O is primarily from the breakdown of feldspars and biotite. The ore elements along with the sulfur increase are because of sulphide precipitation. Elevated values of REE are common with silicification due to the precipitation of REE bearing minerals (MacLean and Barrett, 1993). The potassium seems to have elevated values in the sediments next to the ore and decreases away from it. The sodium behaves uniform in the sediments and no elevation or reduced concentration is present although the sodium concentration in the ore is very low. Sulfur behaves rather erratically. It is fairly stable throughout the sediments but dips in connection with the ore and then increases drastically to decrease into stable values once again. The relationships of these elements can not be seen in the amphibolite which leads to the conclusion that the amphibolite has not played a major part in the exchange of elements during alteration. This might indicate that the ore is premetamorphic.
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Sjöliden
Introduction
The shear zone outcropped in Sjöliden lies on the same lineament and geophysical anomaly as the shear zone in Grundfors and the Svartliden gold mine. It strikes in a NNW SSE direction and is hosted by a felsic metavolcanic rock. The area is highly interesting in an exploration point of view and several holes were drilled during the spring of 2011 with positive results for gold. The main constituents of the outcrop are quartz with minor amounts of muscovite/sericite, arsenopyrite, feldspar and iron oxides. Quartz veining is abundant and no distinct foliation is present in the host rock. In a small scale the veins have random orientations but in larger scale the general strike is NNW SSE. Several outcrops (Figure 19a) of differing size were investigated and the most interesting ones were mapped in more detail. The area has undergone both ductile and brittle deformation as seen in figure 19b, 20a, 20b, 21a and 21b. The biggest outcrop was sampled at three locations, a vertical cut in the north (PS049), a horizontal sample in the east (PS048) and a ~130cm channel sample cut with a diamond blade saw (PS045) (Figure 19a). Eight thin sections were prepared. Whole rock analysis was performed on five samples, three from the biggest outcrop and one each from the other two.
Figure 19. (a) Spatial relationship of the outcrops. The shear zone cuts through the big outcrop in a NNW-SSE direction (dashed lines). Shape and size of outcrops not to scale. (b) Horizontal view of a couple of semi-brittle deformed quartz veins, just south of PS045. The deflection of the marker (quartz vein) indicates a sinistral sense of shear.
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Structures
The largest outcrop in the area made it possible to get both a horizontal and vertical view across the deformation structures. The vertical view was mapped in detail and can be seen in Figure 20a and 20b. Sheared fabrics as well as abundant quartz veins occurring in tension gashes were found (Figure 21a). Sample PS049 was taken from a quartz filled tension gash with sheared fabrics shown in the centre of figure 20a and 21b. Quartz veins generally strikes in the same direction as the shear zone (NNW SSE). However, younger cutting veins are also frequent. The outcrop showed no reliable foliation due to the abundant quartz veining along with a homogenous fine grained rock appearance. Consequently no structural measurements were carried out. However, a strike/dip measurement in the immediate surrounding metagreywackes yielded 337/81˚. Sample PS048 (Figure 19a) was taken at the rim of the outcrop and no obvious shearing is spotted here. However quartz veins are still abundant. A channel sample (PS045) was taken perpendicular to the general orientation of the quartz veins. In this area the most prominent feature is the brittle deformation displayed by several quartz veins, as can be seen in figure 19b. The other two outcrops show no reliable sheared or fractured fabrics but abundant N S striking quartz veins were still present.
Figure 20. Vertical sections from the area around PS049 in figure 19a. (a) Two convincing tension gashes filled with quartz, indicating a west-side-up movement. (b) Brittle deformation indicating both a east- and west-side-up movements.
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Figure 21. (a) Tension gash filled with quartz indicating a sinistral shear sense. Photo from figure 20b. Sub-horizontal, viewed towards SSW (b) Tension gash filled with sheared quartz indicating a west-side-up movement. Photo of the tension gash from the centre of figure 20a. Sub-vertical, viewed towards SSE.
Thin sections
Eight thin sections were prepared for the structural study with and aim to find good shear sense indicators. However this was not the case. All sections were extremely fine grained and barren of porphyroclasts, which made the interpretations difficult. From the eight sections prepared only one (PS049) gave any good indications for shear sense.
PS049
PS049 unlike the other thin sections, showed shear sense from deformed veins. The vein indicating a dextral sense of shear (Figure 22), has a wider top and bottom and is thinner in the middle. The sample has a matrix of quartz, feldspar and sericite with biotite and some epidote as accessory minerals. The opaque phases include iron hydroxides, magnetite, hematite, pyrrhotite, arsenopyrite and gold, where the gold is located within a larger arsenopyrite grain (Figure 23).
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Figure 22. Deformed vein with a wider top and bottom while it is thinner in middle. This would indicate a dextral sense of shear. Horizontal view with north in the top right corner.
Figure 23. Gold grain within arsenopyrite.
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Discussion
Field observations indicate that a semi brittle west side up sense of shear has occurred. The strike/dip of the surrounding metagreywacke shows a steep east dipping foliation. If the dip is the same in the shear zone, it would indicate a normal movement. However the movement will be referred to as west side up dip slip due to the uncertainty. Field observations indicated a sinistral strike slip component in the tension gashes (Figure 21a). This strike slip movement is interpreted to have occurred during the west side up movement. From thin section a ductile dextral component is evident. This is interpreted as being a later movement due to the brittle sinistral and brittle dextral component (Figure 20b) displayed in the offset of quartz veins. No evidence for the timing between the two was visible in the field. One could argue that the two directions of the brittle movement is a conjugate which would indicate an extensional movement. The brittle dextral component might have formed during the ductile phase which would indicate a semi brittle deformation. The abundant gold bearing quartz veins shows, as with Svartliden, great structural similarities to the Fäboliden deposit. Fäboliden is hosted by a N S trending reverse dip slip high angle shear zone (Bark, 2008). The gold in Fäboliden sits in quartz veins oriented along the shear planes and as extension gashes perpendicular to the shear zone (Bark, 2008). Sjöliden show the same type of fault fill veins striking parallel to the shear zone. Quartz veins perpendicular to the fault fill veins might be there, but no notice was taken of this when the area was sampled. The dextral west side up high angle dip slip sense of movement and the fault fill veins all point to a compressive regime during mineralization. This is in compliance with the supposed formation environment of Fäboliden (Bark, 2008) and the regional tectonic interpretation during this period (Juhlin et al. 2002; Weihed et al. 2005).
Geochemistry
Classification
The rock unit was classified according to Lebas et al. (1986) and Cox Bell Pank (1979) as rhyolite grading into dacite (figure 24). The unit plots in the calc alkaline field as shown in figure 25a and 25b (Kuno, 1968; Irvine Baragar, 1971). Four tectonic
43
discrimination diagrams for granites based on Pearce et al. (1984) and Harris et al. (1986) were used. They all yield the same result. All samples plot at the border between within plate granite and volcanic arc granite (Figure 26a d). In figure 26b and 26d the majority of samples plot in the within plate field. However these diagrams use Rb which is sensitive to alteration and might be misleading. If formed in a volcanic arc environment it indicates formation during subduction but if formed as within plate it indicates an anorogenic formation environment.
Figure 24. Classification of the felsic metavolcanics in Sjöliden. At the top based on LeBas (1986) and the bottom based on Cox-Bell-Pank (1979).
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Figure 25. The samples plot in the calc-alkaline suite. (a) From Kuno (1968). (b) From Irvine Baragar (1971).
Figure 26. Tectonic discrimination plots of the Sjöliden samples. All plot uniformly at the boundary between within plate granites and volcanic-arc granites. The binary diagrams from Pearce et al. (1984) and the triangular plot from Harris et al. (1986).
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Mass balance
The samples from this area plot tight together hence no major alteration intensity difference is present and the samples represent the same rock type. As can be seen on the scales of figure 27a and 27b the samples show small differences in element concentration which in turn might give false trends since the samples plot so close to each other. Figure 27a show two possible groups which would indicate two slightly different rock types while 27b show a trend of all samples indicating alteration. The small amount of data and the small elemental differences between them makes it hard to do any reliable mass balance calculations.
0,8 16,6 PS048 0,7 16,4 0,6 16,2 0,5 16 PS049 PS046 0,4 TiO2 PS048 Al2O3 15,8 0,3 PS049 PS046 15,6 0,2 PS045PS047 PS047 15,4 0,1 PS045
0 15,2 0 0,2 0,4 0,6 0,8 520 540 560 580 600 620 640 Lu a Zr b
Figure 27. Immobile element plots of the Sjöliden samples. The diagram with Lu versus TiO2 shows a possible grouping while the Zr vs Al 2O3 diagram shows a linear trend. PS048 were used as the precursor in the subsequent mass balance calculations.
If PS048 is considered the precursor a possible alteration scenario can be seen in Figure 28. The elements that show the most variations are the ore elements and REE except for sample PS046 where several major elements have decreased accompanied with a small silica increase. The gold shows the biggest variation in the samples ranging from 26 ppm to 0.057 ppm. The arsenic which is closely related to the gold as seen in Figure 23, increases with increasing gold content. The three samples with a gold content >0.5 ppm all show arsenic spikes over detection limit in the analysis. The arsenic is therefore plotted as the maximum 250 ppm which was the maximum detection limit for the analytical technique used. The majority of samples show a loss of CaO and MgO. This is
46
probably due to the presence of diopside in the precursor. Unfortunately no thin section was prepared for this sample so it could not be confirmed.
Figure 28. Mass balance diagrams for the Sjöliden samples. PS045 was used as the precursor.
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Mass balance calculations show that the max mass gain goes up to ~16% for PS046 whereas silica stands for 14 of those 16% (Table 4). The majority of the samples show net mass gain except for PS047 that show a small mass loss. The increase in silica gives the largest contribution to all mass gain. The small increase in mass due to silica gain indicates that the quartz veins increase the silica content, alternatively silicification has affected the area. An already quartz rich and fine grained rock made this hard to see in the field.
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wt% Mass calculations SiO2 Al2O3 TiO2 Fe2O3 CaO MgO Na2O K2O MnO P2O5 SrO BaO C S LOI Sum PS048 Precursor 67,20 16,50 0,34 3,64 1,70 0,82 6,47 1,46 0,08 0,05 0,03 0,04 0,14 0,08 1,39 99,94 PS045 Altered 70,80 15,35 0,21 2,34 0,38 0,12 5,91 3,64 0,04 0,02 0,02 0,04 0,05 0,36 1,69 100,97 Rcex (Zr) 81,33 17,63 0,24 2,69 0,44 0,14 6,79 4,18 0,05 0,02 0,02 0,05 0,06 0,41 1,94 Mass change 14,13 1,13 -0,10 -0,95 -1,26 -0,68 0,32 2,72 -0,03 -0,03 -0,01 0,01 -0,08 0,33 0,55 16,04 PS048 Precursor 67,20 16,50 0,34 3,64 1,70 0,82 6,47 1,46 0,08 0,05 0,03 0,04 0,14 0,08 1,39 99,94 PS046 Altered 70,20 15,95 0,23 1,95 0,43 0,12 8,47 0,85 0,03 0,02 0,02 0,01 0,12 0,16 1,29 99,85 Rcex (Zr) 74,80 17,00 0,25 2,08 0,46 0,13 9,02 0,91 0,03 0,02 0,02 0,01 0,13 0,17 1,37 Mass change 7,60 0,50 -0,09 -1,56 -1,24 -0,69 2,55 -0,55 -0,05 -0,03 -0,01 -0,03 -0,01 0,09 -0,02 6,45 PS048 Precursor 67,20 16,50 0,34 3,64 1,70 0,82 6,47 1,46 0,08 0,05 0,03 0,04 0,14 0,08 1,39 99,94 PS047 Altered 70,80 15,45 0,19 1,80 0,58 0,09 6,62 2,63 0,04 0,02 0,02 0,04 0,06 0,19 0,70 99,23 Rcex (Zr) 70,91 15,48 0,19 1,80 0,58 0,09 6,63 2,63 0,04 0,02 0,02 0,04 0,06 0,19 0,70 Mass change 3,71 -1,03 -0,15 -1,84 -1,12 -0,73 0,16 1,17 -0,04 -0,03 -0,01 0,00 -0,08 0,11 -0,69 -0,55 PS048 Precursor 67,20 16,50 0,34 3,64 1,70 0,82 6,47 1,46 0,08 0,05 0,03 0,04 0,14 0,08 1,39 99,94 PS049 Altered 68,70 15,75 0,42 3,86 1,02 0,54 6,56 1,14 0,14 0,03 0,02 0,02 0,08 0,38 1,80 100,46 Rcex (Zr) 74,75 17,14 0,46 4,20 1,11 0,59 7,14 1,24 0,15 0,03 0,02 0,02 0,09 0,41 1,96 Mass change 7,55 0,64 0,12 0,56 -0,59 -0,23 0,67 -0,22 0,07 -0,02 -0,01 -0,02 -0,05 0,33 0,57 9,36 ppm Mass calculations Ba Rb Sr Zr Th U Ta Ga Hf PS048 Precursor 370,00 75,10 269,00 618,00 32,20 14,15 1,80 29,10 12,60 PS045 Altered 324,00 78,30 156,50 538,00 28,50 14,20 1,50 25,80 11,00 Rcex (Zr) 372,18 89,94 179,77 618,00 32,74 16,31 1,72 29,64 12,64 Mass change 2,18 14,84 -89,23 0,00 0,54 2,16 -0,08 0,54 0,04 PS048 Precursor 370,00 75,10 269,00 618,00 32,20 14,15 1,80 29,10 12,60 PS046 Altered 92,80 25,00 138,00 580,00 29,50 11,80 1,60 28,20 11,80 Rcex (Zr) 98,88 26,64 147,04 618,00 31,43 12,57 1,70 30,05 12,57 Mass change -271,12 -48,46 -121,96 0,00 -0,77 -1,58 -0,10 0,95 -0,03 PS048 Precursor 370,00 75,10 269,00 618,00 32,20 14,15 1,80 29,10 12,60 PS047 Altered 341,00 59,90 173,00 619,00 31,20 11,30 1,20 27,00 12,60 Rcex (Zr) 341,55 60,00 173,28 620,00 31,25 11,32 1,20 27,04 12,62 Mass change -28,45 -15,10 -95,72 2,00 -0,95 -2,83 -0,60 -2,06 0,02 PS048 Precursor 370,00 75,10 269,00 618,00 32,20 14,15 1,80 29,10 12,60 PS049 Altered 153,50 55,10 205,00 568,00 28,30 15,15 2,60 29,60 12,10 Rcex (Zr) 167,01 59,95 223,05 618,00 30,79 16,48 2,83 32,21 13,17 Mass change -202,99 -15,15 -45,95 0,00 -1,41 2,33 1,03 3,11 0,57 Table 4. Mass balance calculations for the Sjöliden samples.
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ppm Mass calculations Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu PS048 Precursor 15,10 37,00 72,20 6,77 21,50 3,21 0,79 2,29 0,35 2,20 0,47 1,52 0,26 2,08 0,35 PS045 Altered 15,00 90,30 157,00 14,90 45,60 6,06 0,99 3,84 0,51 2,67 0,49 1,37 0,23 1,68 0,27 Rcex (Zr) 17,23 103,73 180,35 17,12 52,38 6,96 1,14 4,41 0,59 3,07 0,56 1,57 0,26 1,93 0,31 Mass change 2,13 66,73 108,15 10,35 30,88 3,75 0,35 2,12 0,24 0,87 0,09 0,05 0,00 -0,15 -0,04 PS048 Precursor 15,10 37,00 72,20 6,77 21,50 3,21 0,79 2,29 0,35 2,20 0,47 1,52 0,26 2,08 0,35 PS046 Altered 9,80 20,70 42,90 4,36 13,80 2,23 0,62 1,52 0,24 1,53 0,31 1,00 0,18 1,41 0,23 Rcex (Zr) 10,44 22,06 45,71 4,65 14,70 2,38 0,66 1,62 0,26 1,63 0,33 1,07 0,19 1,50 0,25 Mass change -4,66 -14,94 -26,49 -2,12 -6,80 -0,83 -0,13 -0,67 -0,09 -0,57 -0,14 -0,45 -0,07 -0,58 -0,10 PS048 Precursor 15,10 37,00 72,20 6,77 21,50 3,21 0,79 2,29 0,35 2,20 0,47 1,52 0,26 2,08 0,35 PS047 Altered 12,00 41,30 60,40 5,29 16,10 2,31 0,58 1,60 0,27 1,74 0,37 1,21 0,21 1,66 0,28 Rcex (Zr) 12,02 41,37 60,50 5,30 16,13 2,31 0,58 1,60 0,27 1,74 0,37 1,21 0,21 1,66 0,28 Mass change -3,08 4,37 -11,70 -1,47 -5,37 -0,90 -0,21 -0,69 -0,08 -0,46 -0,10 -0,31 -0,05 -0,42 -0,07 PS048 Precursor 15,10 37,00 72,20 6,77 21,50 3,21 0,79 2,29 0,35 2,20 0,47 1,52 0,26 2,08 0,35 PS049 Altered 23,20 63,20 114,50 12,10 41,90 7,32 1,14 5,36 0,76 4,20 0,75 2,09 0,33 2,49 0,40 Rcex (Zr) 25,24 68,76 124,58 13,17 45,59 7,96 1,24 5,83 0,83 4,57 0,82 2,27 0,36 2,71 0,44 Mass change 10,14 31,76 52,38 6,40 24,09 4,75 0,45 3,54 0,48 2,37 0,35 0,75 0,10 0,63 0,09 ppm Mass calculations Cr Cs Nb Sn V W As Bi Sb Se Te Ag Co Cu Pb Zn Au PS048 Precursor 40,00 2,88 36,70 2,00 41,00 3,00 250,00 0,62 0,82 0,70 0,17 0,80 3,00 24,00 28,00 60,00 0,53 PS045 Altered 10,00 0,57 30,50 2,00 5,00 5,00 110,00 0,26 0,19 0,80 0,07 1,10 1,00 12,00 30,00 127,00 0,10 Rcex (Zr) 11,49 0,65 35,04 2,30 5,74 5,74 126,36 0,30 0,22 0,92 0,08 1,26 1,15 13,78 34,46 145,88 0,11 Mass change -28,51 -2,23 -1,66 0,30 -35,26 2,74 -123,64 -0,32 -0,60 0,22 -0,09 0,46 -1,85 -10,22 6,46 85,88 -0,41 PS048 Precursor 40,00 2,88 36,70 2,00 41,00 3,00 250,00 0,62 0,82 0,70 0,17 0,80 3,00 24,00 28,00 60,00 0,53 PS046 Altered 10,00 0,45 33,50 1,00 6,00 4,00 114,00 0,54 0,21 0,50 0,15 0,70 1,00 9,00 17,00 52,00 0,06 Rcex (Zr) 10,66 0,48 35,69 1,07 6,39 4,26 121,47 0,58 0,22 0,53 0,16 0,75 1,07 9,59 18,11 55,41 0,06 Mass change -29,34 -2,40 -1,01 -0,93 -34,61 1,26 -128,53 -0,04 -0,60 -0,17 -0,01 -0,05 -1,93 -14,41 -9,89 -4,59 -0,47 PS048 Precursor 40,00 2,88 36,70 2,00 41,00 3,00 250,00 0,62 0,82 0,70 0,17 0,80 3,00 24,00 28,00 60,00 0,53 PS047 Altered 10,00 0,57 22,90 1,00 5,00 43,00 250,00 0,22 0,54 0,60 0,17 2,10 <1 6,00 56,00 15,00 26,00 Rcex (Zr) 10,02 0,57 22,94 1,00 5,01 43,07 250,40 0,22 0,54 0,60 0,17 2,10 0,00 6,01 56,09 15,02 26,04 Mass change -29,98 -2,31 -13,76 -1,00 -35,99 40,07 0,40 -0,40 -0,28 -0,10 0,00 1,30 0,00 -17,99 28,09 -44,98 25,52 PS048 Precursor 40,00 2,88 36,70 2,00 41,00 3,00 250,00 0,62 0,82 0,70 0,17 0,80 3,00 24,00 28,00 60,00 0,53 PS049 Altered 60,00 1,19 74,60 6,00 15,00 519,00 250,00 1,15 1,12 1,20 0,75 2,50 5,00 13,00 43,00 505,00 7,72 Rcex (Zr) 65,28 1,29 81,17 6,53 16,32 564,69 272,01 1,25 1,22 1,31 0,82 2,72 5,44 14,14 46,79 549,45 8,40 Mass change 25,28 -1,59 44,47 4,53 -24,68 561,69 22,01 0,63 0,40 0,61 0,65 1,92 2,44 -9,86 18,79 489,45 7,87 Table 4 continued.
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Discussion
The rock unit belongs to the calc alkaline suite and was probably formed in an island arc setting. The tectonic history with accretion of island arcs at ~1.875 Ga from the south and the later east directed subduction (Juhlin et al. 2002) would generate the environments needed for the formation of the felsic metavolcanic unit in Sjöliden. The presence of metagreywackes in the immediate vicinity would indicate formation during the sedimentation of the Bothnian basin supergroup. A possible formation scenario is an extrusive event from either the Arvidsjaur Kiruna arc or the Skellefte arc intercalated with the metasediments. The mass balance diagrams indicate a small mass gain if PS048 is considered the precursor. The gain in silica indicates that the quartz vein increased the silica content or that silicification has altered the rock to some extent. Svartliden has undergone heavy silicification and the same process might have been active in Sjöliden although less intense. Silica content in Fäboliden does not seem to increase towards the ore (Bark and Weihed, 2007) which speaks for silicification in the case of Sjöliden. As with both Svartliden and Fäboliden, Sjöliden contains significant amounts of gold. The previous two are interpreted as being orogenic gold deposits. The similarities between Sjöliden and Fäboliden are striking. Both deposits have quartz vein hosted gold and the mineralization is in contact with a sub vertical shear zone (Bark, 2008). However Sjöliden has not undergone as heavy deformation as Fäboliden and Svartliden. All three deposits lie on the same magnetic geophysical anomaly so it is possible that Sjöliden also should be classified as an orogenic gold deposit. In that case the mineralization would probably have occurred contemporaneous with Fäboliden at ~1.8 Ga.
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Grundfors
Introduction
The Grundfors outcrop is a road cut transecting the NW SE trending shear zone giving two outcrops, one on the southern and one on the northern side of the road (profile 1 in Figure 29 and profile 2 in Figure 30 respectively). The shear zone follows the geomagnetic anomaly which can be seen in figure 2. The outcrop on the south side is about 85 meters long starting at N7206255, E0621840 (SWEREF 99) in the west. The outcrop on the northern side of the road has a length of ~16 meters at N7206250, E0621753 (SWEREF99) starting in the east. Profile 1 reaches a height more than 4.5 meters in places while profile 2 reaches a maximum height at 3.5 meters. The main lithology is a mafic volcanic unit with one altered mafic dike on the southern side at ~80.5 meters on profile 1. Visible alterations comprise of silicification and skarn alteration. The southern unit displays three distinct areas of silicification, in the far west, center and the far east. Silicification is not present on the northern side. Skarn veining is continuous on both sides but differ in intensity throughout the sections. Three vein populations with differing dips were displayed and are composed of skarn, quartz and calcite. Both sides have bands of rust connected to several shear zones. Shear zones are scattered throughout both profiles and may broadly be classified as west dipping, east dipping and sub vertical.
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Figure 29. Profile 1 mirrored for easier correlation, now viewed to the north. For higher resolution see Appendix 2.
Figure 30. Profile 2 viewed north. For high resolution picture see Appendix 2.
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Veins
Three populations of veins were present in the outcrops composed of quartz, skarn and calcite.
Population 1 veins
Population 1 veins are composed of mainly skarn and calcite. Their mean orientation is 145/68˚, calculated from 23 measurements (Figure 31a). These veins are located as clusters or individual veins throughout both profiles. Section 0 3 m along Profile 1 comprises only population 1 veins. Clusters of these veins also occur at ~19 meters, ~53 57 meters and ~65 67 meters. Thin quartz veins with random orientations cut through the population and occur throughout the whole profile. In the eastern part of profile 1, brecciated zones occur with population 1 veins along shear bands dipping to the west. In the immediate vicinity of certain shear zones, this vein population undulate along the structure and gradually straighten out further away (at 65 m on profile 1). A close spatial relationship between the clusters of veins and westerly dipping shear zones are present. Many of the observed shear zones (at 17, 55, 60, 65 and 85 meters on profile 1) also show the same strike/dip as the population 1 veins. Several lineation measurements were taken from these veins and show moderate southerly plunges (Figure 33).
Population 2 veins
These veins are thin and composed of quartz. They are gently NE dipping with a mean orientation of 322/28˚ based on 7 measurements (Figure 31b). Population 2 veins occur in a similar fashion as population 1, as clusters and as individual veins throughout both profiles. Clusters occur at ~13 meters, ~16 18 meters, ~57 meters and ~69 meters in profile 1. Clusters of population 2 veins occur in silicified and/or rusty areas in profile 1 while this is not visible in profile 2. The veins are often in connection with the sub vertical shear zones along both profiles. Locally, population 2 veins are arranged in an “en echelon” pattern (17 and 57 meters in profile 1).
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Population 3 veins
Measurements of these veins have been taken on profile 2. The mean orientation is 309/81˚ based on 6 measurements (Figure 31c). Even though no measurements from profile 1 is done, they are present but in smaller amounts. As with population 1 these are composed of skarn and calcite. They always occur with either population 1 or 2 and never alone. They are concentrated in the center of profile 2 starting at ~4 meters and continue to ~12 meters.
Figure 31. Strike/dip of the different vein populations. a) population 1, b) population 2, c) population 3.
Structures
Three variably dipping populations of shear zones are present, west dipping, east dipping and sub vertical. The three different types occur through both profiles with the majority being westerly dipping. The mineralogy of the shear zones is generally similar to the mafic volcanic host rock with a few exceptions that shows calcite precipitation and skarn alteration (at 6 meters on profile 2) and silicification (at 17 and 85 meters on profile 1). Both profiles show heavy alterations directly in contact with the shearing, the most prominent being silicification, only visible on profile 1, but also rusty surfaces visible on both profiles and abundant skarn veining. The distribution of population 1 and 2 veins is strongly related to the variably dipping shear zones. Population 1 occurs with the west dipping shear zones and has roughly the same orientation (at 19, 55 and 66 meters on profile 1). Sense of shear with lineation of population 1 can be seen in figure 33. Population 2 veins occur in certain cases in “en echelon” patterns in connection to the sub vertical shear zones (at 17 and 57 meters on profile 1). The westerly dipping zones
55
have a systematic normal west side down shear sense (Figure 32a, 34, 35) with a sinistral strike slip component, seen in Figure 36, while the sub vertical ones show both normal and reverse sense of shear (Field observations, Figure 32b and Figure 36). Generally the different dipping shear zones occur individually with one exception, at 16.5 meters on profile 1, where all three variable dipping shear zones occur together. The mafic dyke at ~80.5 meters on profile 1 display shearband boudins (as defined by Goscombe and Passchier, 2003) indicating a reverse west side up movement. Brecciation of the mafic volcanic host rock is present at certain shear zones which would indicate deformation under ductile brittle conditions (at 3, 12.5 and 19 meters on profile 1 and Thin section PS019A).
Figure 32. (a) Rotated clast indicating normal west-side-down shear sense (at 12 meters on profile 1) Viewed roughly towards SSE. (b) Shearband boudins displayed in a sub-vertical mafic dyke indicating reverse west-side-up sense of movement (at 80 meters on profile 1). Viewed roughly towards SSE.
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Figure 33. Lineations for population 1 veins with interpreted shear sense giving an east-side-up sinistral strike-slip dominated movement.
Thin sections
The locations of the thin sections are marked on Profile 1 and 2.
PS013A
A pure quartz sample was collected in the eastern silicified mylonitic part. The main foliation is an intense sub vertical mylonitic foliation with extremely fine grained quartz (Figure 34) giving it a cherty appearance in the field. Oblique foliation developed in dynamically recrystallized quartz, as well as asymmetric porphyroclasts of quartz, (Figure 35) all pointing towards a west side down shear sense.
Figure 34. Section PS013A showing oblique foliation indicating west-side- down sense of shear. Sub-vertical section viewed to the north.
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Figure 35. Section PS013A showing an asymmetric quartz porphyroclast indicating west-side-down shear sense. Sub-vertical section viewed towards north.
PS014A
This sample was taken from an intensely sheared mafic dyke classified as a sub vertical shear zone. It is composed of hornblende, quartz and pyrrhotite. Quartz is the major constituent in both matrix and as porphyroclasts. A distinct sub vertical main foliation defined by elongated quartz grains is present. Similar to the section PS013A these sections contain an oblique foliation defined by recrystallized quartz (Figure 36). However the sense of shear is opposite, showing a northeast side down sense of shear.
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Figure 36. Section PS014A showing oblique foliation indicating a northeast-side-down movement. The main foliation is vertical and can be seen slightly tilted on the upper right side of the image. Sub- vertical section viewed towards north west.
PS018B
A horizontal section with a matrix composed of hornblende, quartz and biotite. Opaque minerals include hematite, pyrite and pyrrhotite. No porphyroclasts are present but development of C´ type shear bands in the domain of opaque minerals gives a clear indication of a sinistral sense of shear (figure 37).
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Figure 37. Horizontal view with north at the top right corner and south at the lower left. The main foliation has a N-S strike. As seen in the centre of the image, C`-type shear bands associated with grain size reduction cut the main foliation with a counter clockwise symmetry indicating a sinistral sense of shear.
PS019A
This section is composed of quartz, amphiboles, zoizite, diopside and chlorite. Opaque minerals include pyrrhotite, pyrite and iron hydroxides. The rock has undergone brittle deformation and as can be seen in figure 38, the conjugate pattern would indicate a ~E W directed extensional environment.
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Figure 38. Section PS019A. Brittle deformation can be seen through the offset of diopside veins. The conjugate pattern would indicate an extensional environment. Horizontal view, north upwards in the figure.
Discussion
From field observations and thin section study it is determined that the shear zones have a sinistral normal slip sense of movement, except for one shear zone that has a reverse dip slip sense of movement. The majority of shear zones are dipping to the west or east with a few exceptions of a couple of sub vertical shear zones. It is one of the sub vertical shear zones that show a reverse dip slip sense of shear. No sense of shear was determined for the east dipping shear zones but the geometry and relation to the west dipping ones might indicate a conjugate system (Profile 1 and figure 38). Population 2 veins are interpreted as being of en echelon type, formed perpendicular to σ3. Conjugate shear zones, en echelon veining and the formation of C´ shear bands all indicate an E W extension. The exception being the sub vertical reverse dip slip shear zone which indicate a compressive regime. Bergman Weihed (2001) studied several N S and NW SE striking shear zones in
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the surrounding area and the majority showed a reverse dip slip sense of movement. Bergman Weihed (2001) further states that the reverse N S striking shear zones were formed during the intrusion of the Revsund granite and that the NW SE striking shear zones from the Skellefte field formed prior to that event. This indicates that the tectonic regime during the emplacement of the Revsund granite would have been compressive. Bark and Weihed (2003) also reports a steep reverse dip slip shear zone in Fäboliden which lies along the same geomagnetic anomaly and with roughly the same strike as the shear zones in Grundfors. The timing between the reverse dip slip and sinistral normal dip slip shear zones in Grundfors was not determined in field. Though it would be easy to imagine that the normal slip would have occurred after the reverse slip since no signs of reactivation in the normal slip shear zones are present. Population 1 and 2 veins are considered to have formed contemporaneous with the normal movement while population 3 seems to pre date these veins and are related to a supposedly older reverse movement. One of the sub vertical shear zones of the outcrop however, show signs of being reactivated and normal slip have occurred (in the far east of profile 1). The timing of the normal shearing is based on the presence of en echelon type veining in the immediate vicinity of several sub vertical shear zones and the cutting relationship between the en echelon veins and sub vertical shear zones. Söderlund et al. (2006) propose that the formation of the 1.26 Ga dolerite sills in the area was formed during an extensional event. The dolerites strike NNE to NNW and would be related to an E W extension. This would mean that a compressive regime formed or reactivated an older structure as a sub vertical reverse dip slip shear zone during the intrusion of the Revsund granite, and that a later extensional event created the west and east dipping sinistral normal dip slip shear zones. It is also possible that a transpressive regime during the emplacement of the Revsund granite was active. This indicates that the sub vertical shear zones might have formed just before the sinistral normal slip shear zones during a transpressive regime that later switched to transtensional, creating the sinistral normal slip movement present. The assumption that the normal shearing occurred synchronous with the sinistral strike slip movement is probable since the lineations (Figure 33) plunges moderately south while a ~W block down sinistral strike slip movement has occurred. The scenario of transpression and transtension is deemed most likely since not all NW SE striking shear
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zones in the study area have been affected by normal shearing. Population 1 veins has the same strike/dip as the majority of the west dipping shear zones and are interpreted as being formed at the same time as the normal slip shearing occurred. Population 3 veins present in profile 2 might be related to the formation of the sub vertical shear zones. The veins show roughly the same strike/dip as the sub vertical shear zones. Population 2 veins are interpreted as being of “en echelon” character and composed of quartz.
Geochemistry
Alterations visible in the field include silicification, skarn alteration and calcite vein precipitation. The silicified zones occur on profile 1 at 0, 17, 80 and 85 meters and seem to be related to sub vertical shear zones, except at 0 meters where no exposure further east was present. The skarn alteration is present as veins throughout both outcrops. Calcite generally occurs within the shear zones but veining is present as well. Rusty areas occur at several shear zones. Alterations visible in thin section include biotite grains partially transformed into chlorite. Silica occurs with diopside grains while diopside seems to have precipitated within feldspar grains. The mafic metavolcanic unit is composed of quartz, biotite, hornblende, zoisite and epidote in the matrix. Accessory minerals are diopside, muscovite and chlorite. The opaque phases include hematite, pyrite, pyrrhotite and magnetite. The veins that occur throughout the outcrops are composed of quartz, diopside and calcite. The silicified parts are almost pure quartz with some minor amounts of iron hydroxides, pyrite, pyrrhotite and magnetite.
Classification
The mafic volcanic unit is classified according to Cox Bell Pank (1979) as basalt (figure 39) and as basalt and picrobasalt (figure 40), according to LeBas et al. (1986). In AFM plots, the bulk of the samples plot in the tholeiitic field which fits well with the presence of picrobasalt which is common with a tholeiitic source (figure 41). Three samples, PS013, PS014 and PS029 that were collected within the silicified areas plot either as rhyolite or do not plot at all due to high SiO2 content (>75%). This might be due to silicification or a second rock type in the road cut.
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Figure 39. Classification diagram by Cox-Bell-Pank 1979 showing the bulk of the samples plotting as basalt. Sample PS013, PS014 and PS029 plot outside the fields.
Figure 40. LeBas et al. 1986 classification diagram. The bulk of the samples plot as basalt and picro basalt. The sample plotting in the rhyolite field is PS029. Sample PS013 and PS014 plot outside the fields.
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Figure 41. The left image is an AFM classification by Irvine Baragar (1971). The majority of the samples clearly plot in the tholeiitic field. The right hand picture is an AFM diagram by Kuno (1968) and as with the previous picture the bulk of the samples plot in the tholeiitic field. Sample PS029 is displayed in the bottom left of both pictures which displays a calc-alkaline character. PS013 and PS014 do not plot.
To determine tectonic environment during formation several diagrams (figure 42a b and 43a c) were used based on Pearce and Cann (1973), Wood (1980), Pearce (1982) and Meschede (1986). The diagrams all show conclusive results that indicate a MORB and an Island Arc Tholeiitic affinity.
Figure 42. (a) Discrimination diagram using Y and Cr. From Pearce (1982). VAB=Volcanic-arc basalt, WPB=Within plate basalt, MORB=Mid-ocean ridge basalt. (b) Discrimation diagram using Zr and Ti. From Pearce and Cann (1973).
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Figure 43. Three tectonic environment discrimination diagrams. All samples plot either in Island-Arc Tholeiites or in MORB. (a) The sample at the bottom corresponds to PS029 while PS013 and PS014 do not plot. From Pearce and Cann (1973). (b) The samples plotting below the fields are PS014 and PS029. PS013 do not plot. From Pearce and Cann (1973). (c) Here PS014 plot within the field of N- type MORB while PS029 plots in field AII. PS013 do not plot. From Meschede (1986).
Mass Balance
Immobile elements were plotted against each other to be used in mass balance calculations. As can be seen in figure 44a c, there is a positive correlation for the immobile elements indicating a common source for the samples, except for sample PS029 (Figure 44d). This sample has either another source or the immobile elements have been mobile. The non diluted character of PS029 indicates a second rock type, rhyolitic in composition, intercalated with the mafic metavolcanic.
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1,8 25
1,6
1,4 20 1,2 15 1 TiO2
0,8 Al2O3 10 0,6
0,4 5 0,2
0 0 0 0,2 0,4 0,6 0,8 0 10 20 30 40 Lu a Y b
20 20 18 18 16 16 14 14 PS029 12 12 10 10 Al2O3 Al2O3 8 8 6 6 4 4 2 2 0 0 0 0,5 1 1,5 2 0 0,5 1 1,5 2 TiO2 c Lu d
Figure 44. Immobile element plots with sample PS029 omitted in diagram a-c. a) TiO2 plotted against Lu. b) Al2O3 plotted against Y. c) Al2O3 plotted against TiO2. d) Al2O3 plotted against Lu with sample PS029 incorporated.
The mass balance plots show no good possible precursor for the silicified parts. It seems like the immobile elements have been mobile. A problem with PS013 is that several immobile elements were under detection limit during analysis so the scarcity of data inhibits the chances of finding a reasonable precursor. The silicified part in the center of profile 1 (PS029) show no linear relationship in the immobile element plots, probably because it constitutes a second rock type. The assumed mobility of the immobile elements inhibits any reliable mass balance calculations. Below, PS010 has been used as a precursor for the mass balance diagrams (Figure 45) while the calculations (Table 5) are based on an average 16% Al2O3 content from the cluster of samples in the diagrams above.
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Figure 45. If Al 2O3 and TiO 2 have been immobile it seems that the majority of elements has increased in concentration.
wt% Mass calculations SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O TiO2 MnO LOI Sum PS010 Precursor 41,2 16,3 8,67 16,9 3,78 2,19 1,42 1,4 0,13 5,1 97,09 PS013 Altered 94,4 0,05 3,07 0,04 0,01 0 0 0,01 0,01 0,5 98,09 Rcex (avg Al2O3) 28320 15 921 12 3 0 0 3 3 150 Mass change 28278,8 -1,3 912,33 -4,9 -0,78 -2,19 -1,42 1,6 2,87 144,9 29329,91 PS010 Precursor 41,2 16,3 8,67 16,9 3,78 2,19 1,42 1,4 0,13 5,1 97,09 PS014 Altered 79,6 0,15 10,75 0,44 0,43 0,01 0,01 0,02 0,02 7,96 99,39 Rcex (avg Al2O3) 7960 15 1075 44 43 1 1 2 2 796 Mass change 7918,8 -1,3 1066,33 27,1 39,22 -1,19 -0,42 0,6 1,87 790,9 9841,91 Table 5. Mass balance calculation for the major elements in Grundfors. The mass gain displayed is not possible. This indicates that the immobile elements have been mobile and no reliable calculations can be performed. Another possible is that the precursor of the silicified samples do not occur in the outcrop. For complete table of raw data see Appendix 1.
Discussion
The samples plot in both the island arc and mid ocean ridge basalt fields in the tectonic discrimination diagram. In AFM plots the majority of samples plot in the tholeiitic field while a few plots in the calc alkaline field. This signature indicates a mantle source grading in to a more evolved environment. This environment complies with the tectonic history of the area. The Bothnian supergroup and the intercalated metavolcanics are
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believed to have formed during the Svecokarelian orogeny. The sediments were deposited in a basin formed by an active continental margin and a volcanic arc. The presence of samples plotting in the calc alkaline field indicates assimilation of more evolved material in the magma. This implies that a volcanic arc is the most likely source for the metavolcanic. PS029 plots as a rhyolite and in the calc alkaline field. This indicates a more crustal source which might be the active continental margin north of the volcanic arc. From immobile element plots it is clearly seen that PS029 is not a silicified unit since no dilution of the immobile elements is present (Figure 44d). However for PS013 and PS014 there is a positive correlation in the immobile element plots (Figure 44a c). This implies that the samples are silicified zones of the mafic metavolcanics rock. During mass balance calculations it was discovered that the immobile elements have either been mobile or the precursor of the silicified unit was not present in the outcrop. The mass balance diagrams (Figure 45) indicates an increase of all elements which results in a mass gain of 28000% for PS013 while it is 900% for PS014 (Table 4). While a 900% mass gain might be possible, the uncertainties due to the immobile elements being mobile make any reliable interpretations difficult. One sample shows a mass increase of 28000% which makes the assumption of immobile elements being mobile or a completely different precursor plausible.
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The mylonite
Introduction
A zone of mylonitic metasediments occur ENE of Grundfors within a larger NE SW striking lineament. However, at this specific location, there is no geophysical anomaly present. The area consists of a number of small outcrops with a foliation that varies (figure 46a). The host rocks have quartz and biotite as the main constituents. Two thin sections were prepared from the coarser grained sandy lithological unit occurring in the area. Two foliation directions are present, population 1 with a mean orientation of 292/59˚ based on four measurements. The second population has a mean orientation of 306/80˚ based on four measurements. Two differently dipping lineations were measured (Figure 46b), one with a plunge of 40˚ with the same strike as population 1 while the second lineation plunges 24˚ with the same strike as population 2. The lithology of the outcrops is composed of folded layers of a sandy metasediment in the north east (outcrop 1 and 6 in figure 46a) grading into a finer grained metaargillite towards south west.
Figure 46. (a) Numbers in circles correspond to outcrop number. Dotted field = metasandstone, blank field = metaargillite. Scale in meters. (b) Stereoplot showing two distinct foliation directions (great circles) with lineations (open dots).
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Structures
Several generations of quartz veins are present cutting the main foliation. Deformed quartz veins along the main foliation were also present. No reliable macroscopic structures to determine shear sense were found. Two thin sections were cut parallel and orthogonal to the measured lineation. The sub horizontal thin section shows two convincing shear sense indicators, oblique foliation in quartz and a delta shaped recrystallized porphyroclast of quartz (Figure 47). Both indicate a dextral sense of shear. The sub vertical section (Figure 48) shows a rotated quartz porphyroclast indicating a S block up movement. The foliation is refracted in map scale between the two different lithologies (Figure 46a). Outcrop 1 in figure 46a showed both foliations indicating the possible lithological contact. Undulating quartz veins along the foliation were present in outcrop 4 while this was not present in the other outcrops indicating folding in the area.
Figure 47. Sub-horizontal section showing oblique foliation at point 1 and a delta shaped porphyroclast of quartz at point 2, both indicating a dextral sense of shear.
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Figure 48. Sub-vertical section showing a rotated quartz porphyroclast indicating a south-side-up movement. Viewed towards ~west.
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Discussion
Since no field observations made it possible to determine the sense of shear the conclusion is based on the thin sections. The first impression of the movement is a dextral strike slip with a minor S block up movement. However, when lineations are plotted with the sense of shear, the movements are contradictive (Figure 49). Instead it seems that two movements have occurred, one S block up movement and one dextral strike slip movement. The dextral strike slip movement might have formed during N S compression, thus indicating a structure pre dating the emplacement of the Revsund granite. The timing between the two possible movements is unknown. The interpretation of a rotated quartz porphyroclast (Figure 48) might also be wrong. The structure is quite diffuse and it is possible that the clast show an asymmetric porphyroclast which would give an opposite shear sense. The refracted foliation is probably due to one rock unit being more competent, hence withstanding deformation better.
Figure 49. Contradictive shear senses in the mylonite indicating two separate movements or a misinterpretation of the structure seen in Figure 48.
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The granodiorite
Introduction
“The granodiorite” outcrop is located approximately 10 km NW of the Grundfors road cut. It lies on the same lineament as Grundfors but outside the geophysical anomaly. This outcrop borders an area that shows both NW SE and ENE WSW striking deformation zones. The outcrop is small and lots of vegetation both on and beside made field observations challenging. The shearing seems to have occurred in very local bands and no penetrative foliation is present. Two thin sections were prepared, with neither of them showing any reliable shear sense indicators. However, one macrostructure displaying a quartz filled tension gash was present (Figure 50).
Structures
The outcrop had two differently oriented shear bands. One had a strike/ dip of 150/38˚ while the other had an orientation of 230/30˚. From the band striking 230˚ a macrostructure composed of a tension gash filled with quartz gives an indication of a W block up movement (Figure 50). From the shear band striking 150˚ no reliable shear sense indicators were found. The thin section prepared from this sample showed a microscopic cataclastic flow, indicating low temperature deformation.
Figure 50. Quartz filled tension gash indicating a W-block-up sense of shear. Sub-vertical picture viewed roughly towards NW.
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Discussion
The area where “the granodiorite” is located, borders the large geophysical anomaly that the Svartliden, Sjöliden and Grundfors lineament joins to the north. The area displays mainly two differently striking lineaments, one striking ~NW SE and the other~ ENE WSW. The macrostructure in figure 48 was displayed within a shear band striking NE SW. The W block up indicates a reverse movement during a E W compressive regime. The low temperature deformation evident in the thin section from the shear band with a NW SE strike might indicate a temperature gradient over the area.
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Discussion structures
Sjöliden with its NNW SSE striking shear zone indicated two deformational events. One semi brittle west side up dip slip with a sinistral strike slip movement formed during a E W compressive regime and a second brittle conjugate system indicating a E W extension (figure 51). The cutting relationship between the brittle and the ductile deformation indicates that the brittle event post dates the ductile deformation. Grundfors with its NW SE striking shear zones showed two different shear senses depending on the dip, sinistral normal dip slip for the conjugate system and reverse dip slip for the sub vertical shear zones. Based on the shear indicators and the relationship of the different vein populations to the shear zones from Grundfors, it is interpreted that the reverse sub vertical shear zones formed prior the normal sinistral strike slip shear zones (figure 51). The sub vertical shear zones, unless reactivated during normal slip, indicates E W compression while the sinistral normal slip shear zones point to an E W extensional event. This indicates that a transpressive regime switched over to transtension in Grundfors or, alternatively, an orogenic collapse causing extensional deformation affecting the area subsequent to compression. The granitic body west of the shear zone in Grundfors might have acted as a rigid body. During the E W compression the granitic body might have rotated counter clockwise creating a local zone of transtension in the north west corner of the intrusion. Högdahl and Sjöström (2001) analyzed an area in central Sweden related to the intrusion of the Revsund granite and found evidence for a transpressive regime. The presence of a transpressive regime in Grundfors might indicate that the same regime has been active in Sjöliden, which would explain the relationship between the compressive and extensional indications. However the granitic body shielding Grundfors would not create a transtensional zone in Sjöliden. If a transpressive regime has affected the area it seems to have been regional and not related to the granitic body immediately west of the studied localities. The extension might also be related to an orogenic collapse. “The granodiorite” displayed a reverse W block up sense of shear which seems to be related to a third deformational event (figure 51). Weihed (2002) states that ENE WSW trending shear zones might have formed during E W compression at ~1.79 Ga. In Svartliden the only certain shear sense indicator points to a reverse S block up movement. This in turn
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indicates a N S compressive regime. The presence of a possible stair stepping structure might indicate a dextral strike slip movement but due to uncertainties this is left out of the discussion. The shear zones in both “the mylonite” and the Svartliden gold mine indicate formation during N S compression. When compared to the Skellefte district the N S compression occurs prior the E W compression (Juhlin et al. 2002; Skyttä et al. 2010). If the deformation in “the mylonite” and the Svartliden gold mine are related to the same event, which is deemed probable, the deformation would have occurred prior the intrusion of the Revsund granite. If the timing of mineralization in Svartliden occurred during this N S compressive event it would pre date the mineralization of Fäboliden. Fäboliden was mineralized during the later E W compression at ~1.80 Ga (Bark and Weihed, 2007). The mineralization of Sjöliden seems to be related to the E W compressive event contemporaneous with the mineralization of Fäboliden. The similarities between the two mineralizations are striking. Both are hosted by a sub vertical shear zone formed during E W compression and the gold sits in quartz veins parallel to the shear zones. However, the intensity in deformation differs a lot with ductile deformation in “the mylonite” and ductile brittle in Grundfors, Svartliden and Sjöliden. “The granodiorite” with its cataclastic flow band indicates low temperature brittle deformation. During N S compression no brittle phase is present. Both Svartliden and “the mylonite” that are considered to have formed during this event show no signs of any brittle deformation. Later, during the E W compression and the emplacement of the Revsund granite, there seems to be a brittle component present. Sjöliden showed a semi brittle behavior during the reverse movement and a brittle behavior during the formation of the possible conjugate system. Grundfors also show this behavior. Although no semi brittle indications are present during the reverse movement in the sub vertical shear zones, a brittle deformation have definitely occurred during the transtensional regime creating the conjugate system. In “the granodiorite” the NW SE trending shear band shows a microscopic cataclastic flow which indicates a low temperature deformation. The first deformational event during N S compression, with its ductile shear zones, seems to have had a higher temperature during deformation. The second deformational event with its E W compression forming the sub vertical shear zones, seem to have had a somewhat lower
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temperature and the following formation of conjugate systems even lower. The assumed third deformational event during E W compression creating the cataclastic flow in “the granodiorite” indicates deformation at the lowest temperature. The timing of the deformational events fits well with the regional peak metamorphism at 1.85 1.80 Ga (Weihed et al. 1992; Weihed et al. 2002). N S compression was active during 1.85 Ga (Juhlin et al. 2002) creating the ductile shear zones. Later during E W compression the deformation temperature declines as time progresses and the semi brittle, brittle shear zones and the cataclastic flow forms in that succession.
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Figure 51. A possible scenario to explain the structural evolution of the area. Deformation characterized by N-S compression occurred first. Thereafter shear zones related to a E-W compression were formed, and finally, an extensional/transtensional regime created the normal faults. A possible later deformation in “the granodiorite” was possibly due to E-W compression.
Discussion geochemistry
The three localities, Grundfors, Svartliden and Sjöliden, used for geochemistry show a rather uniform behavior. Grundfors and Svartliden show a MORB and volcanic arc
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affinity while Sjöliden show a volcanic arc affinity. These environments were present during the Svecofennian orogeny, hence it implies that the rock types were formed during this event. The sources for the metasediments in Svartliden show both a tholeiitic island arc and more evolved arc setting source. The ore show an undisputable linear relationship to the quartz biotite schist and sulphide, graphite bearing schist. These two sediment types both had a more acidic source indicating that the silicification occurred in the more acid sediments. The mass gain and accompanying volume gain due to silicification is hard to explain. Even though silica depletion in the sediments close to the ore is present it cannot compensate for the extreme mass gain present. One could argue that the volume loss in the sediments along with the formation related to a shear zone might be able to compensate for the volume gain but the data in this study cannot confirm nor dismiss this possible scenario. An easier to explain scenario would be a different precursor. Maybe an already immobile element diluted rock type was present. The silicification of this unit would not result in an as extreme mass gain as reported here. Grundfors show the same extreme dilution due to silicification. However the immobile element plots show that either the immobile elements have been mobile or the precursor of the silicified areas was not present in the outcrop. The discovery that PS029 actually were a rhyolitic unit intercalated in the metabasalt speaks for the different precursor scenario. The small amount of data from Sjöliden gave no conclusive results regarding mass and volume gain. There might be a small silica alteration present but this study cannot confirm this. Grundfors was the only locality in this study that showed chloritization to some degree. This indicates that the area has undergone greenschist facies metamorphism. Svartliden, Sjöliden and Fäboliden all have gold mineralizations. This would confirm the notion by Bark (2008) that areas with sub vertical NW to NE striking shear zones should be the main target for exploration.
Conclusions
The studied area show signs of deformation due to both N S and E W compression. A possible transpressive regime might have created the extensional movements although an orogenic collapse or later extensional event can not be dismissed. Signs of differing deformation temperatures might indicate successive creation of the different shear zone
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types, starting with the ductile movements during peak metamorphism and with more brittle movements as time progressed. Immobile element plots indicate that the ore in Svartliden is a silicified metasedimentary unit with an acid source but the precursor used in this study may not be the correct one due to extreme mass gain. Grundfors, Svartliden and Sjöliden all show a volcanic arc affinity indicating rock formation during the Svecofennian orogeny.
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Acknowledgements
I would like to thank Dragon Mining Sweden AB for funding and initial idea for this project. I would also like to thank my supervisors Pietari Skyttä and Olof Martinsson for help and support during the course of my thesis.
References
BABEL Working Group, (1990). Evidence for Early Proterozoic plate tectonic from seismic reflection profiles in the Baltic Shield. Nature, 348, pp 34 38.
BARK, G., and WEIHED, P., (2007). Orogenic gold in the new Lycksele-Storuman ore province, northern Sweden; the Palaeoproterozoic Fäboliden deposit. Ore Geology Reviews, 32, pp 431 451.
BARK, G., 2008. On the origin of the Fäboliden orogenic gold deposit, northern Sweden (2008:72). Doctoral thesis, Luleå University of Technology, 142p. ISSN 1402 1544.
BARRETT, T. J., MACLEAN, W.H., and ÅREBÄCK, H., (2005). The Palaeoproterozoic Kristineberg VMS deposit, Skellefte district, northern Sweden. Part II: chemostratigraphy and aleration. Mineralium Deposita, 40, pp 368 395.
BERGMAN WEIHED, J., (2001). Palaeoproterozoic deformation zones in the Skellefte and Arvidsjaur areas, northern Sweden. In: WEIHED, P., (Ed.), Economic Geology Research 1999 2000. Sveriges Geologiska undersökning, C833, pp 46 68.
BILLSTRÖM, K., BROMAN, C., JONSSON, E., RECIO, C., BOYCE, A.J., and TORSSANDER, P., (2009). Geochronological, stable isotopes and fluid inclusion constraints for a premetamorphic development of the intrusice-hosted Björkdal Au deposit, northern Sweden. International Journal of Earth Sciences, 98, pp 1027 1052.
BINNS, R.A., and APPLEYARD, E.C., (1986). Wallrock alteration at the Western System of the CSA Mine, Cobar, New South Wales. Australia. Applied Geochemistry, 1, pp 211 225.
BJÖRK, L., and KERO, L., (2001). Bedrock Map 22H Järvsjö NO, scale 1:50000. Sveriges Geologiska Undersökning, Ai 145.
82
BLATT, H., MIDDLETON, G.V., and MURRAY, R., (1980). Origin of sedimentary rocks: Englewood Cliffs. NJ, Prentice Hall, 782p.
BLATT, H., (1992). Sedimentary Petrology. W.H Freeman and Company, New York, 514p.
CLAESSON, S., and LUNDQVIST, T., (1995). Origins and ages of Proterozoic granitoids in the Bothnian basin, central Sweden; isotopic and geochemical constraints. Lithos, 36, pp 115 140.
ELIASSON, T., GREILING, R.O., STRÄNG, T., and TRIMUF, C.A., (2001). Bedrock Map 23H Stensele SO, scale 1:50000. Sveriges Geologiska Undersökning, Ai 129.
FLOYD, P.A., and LEVERIDGE, B.E., (1987). Tectonic environment of the Devonian Gramscatho basin, south Cornwall: framework mode and geochemical evidence from turbiditic sandstone. Journal of Geological Society (of London), 144, pp 531 542.
GAAL, G., and GORBATSCHEV, R., 1987. An outline of the Precambrian Evolution of the Baltic Shield. Precambrian Research, 35, pp 15 52.
GOSCOMBE, B.D., and PASSCHIER, C.W., (2003). Asymmetric boudins as shear sense indicators-an assessment from field data. Journal of Structural Geology, 25, pp 575 589.
HALLBERG, A., (2001). Rock classification, magmatic affinity, and hydrothermal alteration at Boliden, Skellefte district, Sweden – a desk-top approach to whole rock geochemistry. In: WEIHED, P., (Ed.), Economic Geology Research 1999 2000. Sveriges Geologiska undersökning, C833, pp 93 131.
HARRIS, N.B.W., PEARCE, J.A., and TINDLE, A.G., (1986). Geochemical characteristics of collision- zone magmatism. Geological Society, London, Special Publication 19, pp 67 81.
HIPPERTT, J.F., (1998). Breakdown of feldspar, volume gain and lateral mass transfer during mylonitization of granitoids in a low metamorphic grade shear zone. Journal of Structural Geology, 20, pp 175 193.
HÖGDAHL, K., and SJÖSTRÖM H., (2001). Evidence for 1.82 Ga transpressive shearing in a 1.85 Ga granitoids in central Sweden: implications for the regional evolution. Precambrian Research, 105, pp 37 56.
83
JUHLIN, C., ELMING, S. Å., MELLQVIST C., ÖHLANDER, B., WEIHED, P., and WIKSTRÖM, A., (2002). Crustal reflectivity near the Archena-Proterozoic boundary in northern Sweden and implications for the tectonic evolution in the area. Geophysical Journal International , 150, pp 180 197.
KATHOL, B., and WEIHED, P., (2005). (Eds.) Description of regional geological and geophysical maps of the Skellefte District and surrounding areas. Sveriges Geologiska Undersökning, Uppsala. pp. 197.
LAHTINEN, R., KORJA, A. and NIRONEN, M., (2005). Palaeoproterozoic tectonic evolution of the Fennoscandian shield, in LEHTINEN, M., NURMI, P., and RÄMÖ, T., The Precambrian Bedrock of Finland – Key to the evolution of the Fennoscandian Shield. Elsevier Science B.V, pp 418 532. WELIN, E., (1986). The Depositional Evolution of the Svecofennian Supracrustal Sequence in Finland and Sweden. Precambrian Research, 35, pp 95 113.
LAHTINEN, R., GARDE, A.A., and MELEZHIK, V.A., (2008). Paleoproterozoic evolution of Fennoscandia and Greenland. Episodes, 31, 1, pp 20 28.
MACLEAN, W.H., and BARRETT, T.J., (1993). Lithogeochemical techniques using immobile elements. Journal of Geochemical Exploration, 48, pp 109 133.
MANIKYAMBA, C., NAQVI, S.M., RAM MOHAN, M., and GNANESHWAR RAO, T., (2004). Gold mineralization and alteration of Penakacherla schist belt, India, constraints on Archean subduction and fluid processes. Ore Geology Reviews, 24, pp 199 227.
MAYNARD, J.B., VALLONI, R., and YU, H., (1982). Composition of modern deep sea sands from arc- island basin. Geological Society (of London), Special Publication 10, pp 551 561.
NIRONEN, M., 1997. The Svecofennian Orogen: a tectonic model (1997). Precambrian Research, 86, pp 21 44.
PEARCE, J.A., HARRIS, N.B.W., and TINDLE, A.G., (1984). Trace-Element discrimination Diagrams for the Tectonic Interpretation of Granitic-Rocks. Journal of Petrology, 25, pp 956 983.
PETTIJOHN, E.J., PATTER, P.E., and SIEVER, R., (1973). Sand and Sandstone. Wiley, New York, 618p.
RASMUSSEN, T.,M., ROBERTS, R., G., and PEDERSEN, L., G., (1987). Magnetotellurics along the Fennoscandian long range profile. Royal Astronomical Society Geophysical Journal, 89, pp 790 820.
84
ROSER, B.P., and KORSCH, R.J., (1986). Determination of tectonic setting of sandstone-mudstone suites using SiO 2 content and K 2O/Na 2O ratio. Journal of Geology, 94, pp 635 650.
RUTLAND, R.W.R., SKIÖLD, T., and PAGE, R.W., (2001). Age of deformation episodes in the Palaeoproterozoic domain of northern Sweden, and evidence for a pre-1.9 Ga crustal layer. Precambrian Research, 112, pp 239 259.
SKYTTÄ, P., HERMANSSON, T., ELMING, S Å., and BAUER, T., (2010). Magnetic fabrics as constraints on the kinematic history of a pre-tectonic granitoids intrusion, Kristineberg, northen Sweden. Journal of Structural Geology, 32, pp 1125 1136.
STREIT, J.E., and COX, S.F., (1998). Fluid infiltration and volume change during mid-crustal mylonitization of Proterozoic granite, King Island, Tasmania. Journal of Metamorphic Geology, 16, pp 197 212.
SÖDERLUND, U., ELMING, S Å., ERNST, R.E., and SCHISSEL, D., (2006). The Central Scandinavian Dolerite Group-Protracted hotspot activity or back-arc magmatism? Constraints from U-Pb baddeleyite geochronology and Hf isotopic data. Precambrian Research, 150, 136 152.
WEIHED, P., BERGMAN, J., and BERGSTRÖM, U., (1992). Metallogeny and tectonic evolution of the Early Proterozoic Skellefte district, northern Sweden. Precambrian research, 58, pp 143 167.
WEIHED, P., BILLSTRÖM, K., PERSSON, P.O., and BERGMAN WEIHED, J., (2002). Relationship between 1.90-1.85 Ga accretionary processes and 1.82-1.82 Ga oblique subduction at the Karelian craton margin, Fennoscandian Shield. GFF 123.
WEIHED, P., ARNDT, N., BILLSTRÖM, K., DUCHESNE, J C., EILU, P., MARTINSSON, O., PAPUNEN, H., and LAHTINEN, R., (2005). 8: Precambrian geodynamics and ore formation: The Fenooscandian Shield. Ore Geology Reviews, 27, pp 273 322.
Software Georient 9.5.0, HOLCOMBE, R., (2011). School of Earth Sciences, University of Queensland, Autralia.
Petrograph 1.0.5, PETRELLI, M., Department of Earth Sciences, University of Perugia, Italy.
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Appendices
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Appendix 1, Whole rock data Method (%) SV008 SV016 SV017 SV018 SV019 SV022 SV025 SV026 SV029 SV030 SV031 SV035 SV036 SV038 SV045 SV047 SV048 SV050 SV052 SV054 SV055 SV057 SV059 SV060 SV061 SV063 SV067 SV069 ME-ICP06 SiO2 49,3 51,7 86,7 44,6 49 51,1 47,4 56,5 65,6 64,4 66,5 57,9 73,9 46 43,2 50,3 47,5 40,8 53 49,9 75,6 51,6 92,6 49,8 51,8 49 46,2 65,9 ME-ICP06 TiO2 1,08 0,95 0,01 1,36 1,26 0,94 1,62 0,66 0,71 0,79 0,74 0,64 0,53 1,21 1,46 1,28 0,02 0,16 0,78 1,22 0,19 1,29 0,01 1,39 0,93 3,7 2,38 0,62 ME-ICP06 Al2O3 13,95 17,55 0,23 14,15 13,25 14 20,2 12,25 13,1 15,15 14,15 11,8 11,4 6,88 7,62 13,3 0,6 2,08 11,45 12,75 1,74 13,4 0,48 16,9 13,9 14,5 11 13,75 ME-ICP06 CaO 10,15 8,35 6,86 12 9,92 11,3 4,02 3,11 2,49 1,36 1,64 2,32 0,96 8,88 9,39 10 3,87 16 5,3 8,26 11,1 9,66 0,88 5,81 13,9 5,46 13,3 3,27 ME-ICP06 Fe2O3 14,4 7,23 2,76 13,4 14,25 11,85 12,95 11,5 7,64 7,83 7,59 10,85 4,22 13,05 12,8 13,7 40,2 24,8 9,49 13,75 7,44 14,1 5,09 8,83 11,65 11,7 14,4 5,42 ME-ICP06 K2O 0,23 3,46 0,01 0,42 0,12 0,5 5,68 2,16 2,54 2,95 2,97 1,92 2,29 0,09 0,08 0,11 0,05 0,43 1,07 0,19 0,01 0,16 0,01 4,45 0,37 2,74 0,55 2,09 ME-ICP06 MgO 8,14 6,33 1,6 7,34 7,21 6,54 3,78 3,98 2,91 3,19 3,08 3,14 1,6 18,95 19 7,26 2,43 7,71 6,58 8,07 1,74 7,68 0,34 7,12 4,6 7,26 7,06 2,45 ME-ICP06 Na2O 1,88 1,46 0,02 2,13 2,25 2,34 2,6 1,94 2,56 2,32 2,37 2,54 3,45 0,51 0,32 2,49 0,07 0,08 2,44 2,67 0,06 1,81 0,01 0,84 1,82 2,76 1,78 3,44 ME-ICP06 MnO 0,2 0,1 0,08 0,17 0,2 0,19 0,15 0,13 0,12 0,07 0,06 0,04 0,04 0,19 0,17 0,19 0,32 0,25 0,12 0,17 0,16 0,23 0,02 0,1 0,21 0,13 0,17 0,08 ME-ICP06 Cr2O3 0,03 0,06 0,02 0,03 0,02 0,02 0,05 0,04 0,04 0,04 0,04 0,05 0,04 0,26 0,26 0,03 0,02 0,03 0,09 0,03 0,04 0,04 0,05 0,04 0,03 0,1 0,08 0,03 ME-ICP06 P2O5 0,07 0,08 0,16 0,12 0,08 0,11 0,11 0,11 0,15 0,13 0,14 0,11 0,11 0,09 0,14 0,1 0,76 0,77 0,11 0,09 0,99 0,09 0,02 0,09 0,1 0,11 0,14 0,18 ME-ICP06 SrO 0,02 0,02 <0.01 0,03 0,02 0,02 0,02 0,01 0,01 0,01 0,02 0,02 0,01 <0.01 0,02 0,02 0,01 0,01 0,03 0,02 <0.01 0,02 <0.01 0,02 0,02 0,02 0,03 0,03 ME-ICP06 BaO <0.01 0,05 <0.01 0,01 <0.01 0,01 0,1 0,04 0,05 0,06 0,05 0,04 0,07 <0.01 <0.01 <0.01 <0.01 0,01 0,02 <0.01 <0.01 <0.01 <0.01 0,05 0,01 0,15 0,03 0,05 OA-GRA05 LOI 1,57 3,99 0,6 3,9 2,3 1,39 1,79 6,6 1,78 1,78 1,49 8,1 1,58 4,33 4,87 0,78 3,99 5,53 4,91 0,9 2,08 0,5 1,18 3,48 1,38 1,39 1,19 1,69 TOT-ICP06 Total 101 101,5 99,1 99,7 99,9 100,5 100,5 99 99,7 100 101 99,5 100 100,5 99,3 99,6 99,8 98,7 95,4 98 101 100,5 100,5 98,9 100,5 99 98,3 99 C-IR07 C 0,1 0,08 0,23 0,79 0,52 0,07 0,24 3,79 0,8 0,59 0,55 5,36 0,57 0,15 0,35 0,02 0,07 3,16 3,7 0,1 2,1 0,08 0,08 0,43 0,15 0,07 0,18 0,26 S-IR08 S 0,66 0,02 0,25 0,13 0,61 0,59 1,66 3,77 0,6 0,06 0,12 3,62 0,69 0,13 0,43 0,12 11,75 5,24 1,45 0,31 0,28 0,02 1,7 0,06 0,51 1,67 0,57 1,3 ppm ME-MS81 Ba 20,4 439 0,9 69,1 15,8 82,6 830 328 465 528 425 328 609 5,5 5,7 31,6 17,1 67,8 171,5 31,8 0,8 27 4 399 75,9 1330 258 458 ME-MS81 Ce 7,9 8,4 8,4 11,2 9,1 7,1 10,7 42 58,4 62,9 58,8 55,1 61,6 19,8 28,7 11,1 7,2 22,3 48,7 10,1 19,2 11,9 1,4 11,5 8,3 35 26,9 73,1 ME-MS81 Cr 170 410 150 230 150 130 350 280 300 270 280 310 290 1830 1850 220 130 180 590 220 250 260 360 290 230 700 550 230 ME-MS81 Cs 4,04 36 0,14 4,44 2,37 14,55 34,1 27,2 6,25 5,29 7,68 5,85 37 1,06 0,93 0,29 0,44 4,87 7,03 1,34 0,07 1,51 0,22 44,6 10,35 20,7 3,97 11,15 ME-MS81 Dy 3,69 3,13 1,69 4,95 4,46 3,79 4,15 4,67 4,22 4,75 4,84 5,64 3,98 2,78 2,93 4,52 2 3,88 4,37 4,22 4,13 4,42 0,17 4,39 3,71 4,35 3,75 5,98 ME-MS81 Er 2,09 1,62 0,89 2,73 2,48 2,13 2,29 2,57 2,2 2,4 2,4 3,1 2,22 1,36 1,28 2,46 1,3 2,27 2,44 2,42 2,34 2,66 0,13 2,41 2,3 1,75 1,75 3,3 ME-MS81 Eu 0,86 0,75 0,24 1,09 1,07 0,92 0,9 1,15 1,28 1,26 1,34 1,3 1,02 0,85 1,22 1,01 0,5 0,66 1,39 0,98 1,03 1,57 0,06 1,35 0,97 1,71 1,48 1,33 ME-MS81 Ga 17,8 18,2 1 18,8 17,5 16,5 23,5 16,9 16,8 18,9 18,3 15 14,6 14,6 16 17,4 2 5,5 16,2 16,9 4,5 19,1 1,6 22,9 19 30,4 21,6 18,7 ME-MS81 Gd 2,95 2,82 1,66 3,95 3,52 2,94 3,35 4,17 4,19 4,93 4,93 5,39 4,67 3,4 3,97 3,69 2,08 3,86 5,06 3,35 5,06 4,04 0,19 4,31 3,44 6,13 5,17 6,76 ME-MS81 Hf 1,7 1,7 0,2 2,2 1,9 1,6 2,6 3,1 4,8 4,7 4,5 4 5,5 2,4 3 2,1 0,2 1,6 3,4 2,4 1,4 2,2 0,4 2,4 1,6 4,9 4,1 4,4 ME-MS81 Ho 0,74 0,6 0,32 0,96 0,89 0,74 0,8 0,9 0,78 0,87 0,87 1,08 0,77 0,5 0,51 0,88 0,44 0,8 0,86 0,84 0,84 0,93 0,04 0,87 0,78 0,72 0,68 1,17 ME-MS81 La 3,1 3,4 4,8 4,5 3,5 2,8 4 21,4 29,7 31,9 29,8 27,9 30 7,9 11,6 4,4 7,9 15,6 23,5 3,8 13 4,4 1,6 4,3 3,3 13,5 10,4 36,2 ME-MS81 Lu 0,31 0,21 0,12 0,39 0,36 0,31 0,34 0,43 0,33 0,36 0,35 0,51 0,32 0,14 0,13 0,37 0,19 0,34 0,36 0,36 0,29 0,38 0,02 0,31 0,33 0,18 0,2 0,46 ME-MS81 Nb 2,6 2,2 0,5 3,9 3 2,4 3,8 7,4 9,7 10,7 10,1 9,3 9,3 7,9 14,1 3,7 0,5 1,5 8,1 3,5 2,5 4 0,4 3,5 2,6 22,8 18,1 10,8 ME-MS81 Nd 6,5 6,8 5,5 9,1 7,8 6 9 20,8 26,3 28,8 27,2 26,5 25,3 12,2 16,3 8,8 6,5 12,3 21,9 8,2 16,5 8,4 0,8 8,8 6,2 22,7 17,8 31,1 ME-MS81 Pr 1,22 1,26 1,23 1,7 1,42 1,13 1,66 5,14 6,81 7,34 6,79 6,59 7,18 2,81 3,94 1,67 1,67 3,25 5,85 1,54 3,91 1,78 0,23 1,8 1,29 5,17 3,94 8,53 ME-MS81 Rb 35,3 173 1,2 36,8 11,6 80 164 166,5 108 138,5 164,5 87,3 205 3 3,2 3 1,5 25,9 59,2 7,8 0,5 6,3 0,8 291 40,9 88,1 18,3 150 ME-MS81 Sm 2,26 2,13 1,36 3,04 2,7 2,2 2,94 4,41 5,27 5,62 5,56 5,71 5,36 3,39 4,33 2,9 1,62 3,07 5,29 2,61 4,39 2,98 0,17 3,2 2,37 6,33 5,06 6,94 ME-MS81 Sn 6 5 1 13 1 1 6 4 1 2 2 1 18 4 5 1 2 3 3 1 13 2 2 6 8 2 3 4 ME-MS81 Sr 148,5 209 31,4 287 138 199 179 111 119,5 106,5 138 217 112 27,7 152,5 184 72,9 58,7 234 156 44,7 158,5 45,1 139,5 204 126,5 232 243 ME-MS81 Ta 0,2 0,1 <0.1 0,2 0,2 0,2 0,2 0,9 0,7 0,8 0,8 0,8 0,7 0,4 0,9 0,2 <0.1 <0.1 0,7 0,2 0,2 0,2 0,8 0,2 0,1 1,7 1,2 0,8 ME-MS81 Tb 0,53 0,48 0,27 0,73 0,66 0,57 0,61 0,72 0,66 0,76 0,75 0,88 0,66 0,5 0,54 0,68 0,3 0,58 0,72 0,63 0,69 0,68 0,03 0,71 0,55 0,81 0,68 0,98 ME-MS81 Th 0,32 0,28 0,16 0,38 0,28 0,22 0,33 5,58 9,41 10,1 9,38 8,16 10 0,69 1,14 0,34 0,22 1,32 6,9 0,35 1,58 0,33 0,21 0,32 0,23 1,02 0,81 9,92 ME-MS81 Tl <0.5 0,8 <0.5 <0.5 <0.5 <0.5 1,3 1,3 0,6 0,5 0,6 0,6 1,6 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 2,2 <0.5 <0.5 <0.5 1,1 ME-MS81 Tm 0,32 0,23 0,11 0,4 0,38 0,32 0,34 0,4 0,32 0,37 0,37 0,47 0,34 0,18 0,17 0,38 0,19 0,35 0,36 0,36 0,32 0,41 0,03 0,36 0,34 0,23 0,23 0,49 ME-MS81 U 0,2 1,12 2,98 0,94 0,1 0,08 0,17 7,11 3,28 3,39 3,23 13,55 3,41 0,23 0,27 0,12 0,46 25,7 6,3 0,15 3,98 0,12 0,58 0,52 0,34 0,9 0,22 3,56 ME-MS81 V 327 342 20 385 347 282 471 294 140 140 134 311 87 236 251 346 27 94 228 333 109 399 5 482 341 531 394 106 ME-MS81 W 1 1 1 1 <1 1 1 2 1 2 1 2 3 2 2 1 <1 3 1 <1 14 1 2 1 1 2 2 186 ME-MS81 Y 19,8 14,6 8,2 25,5 23,5 20 19,8 24,3 20,8 23,2 23,5 28,5 22,3 14,5 13,6 23,2 16 27,3 25,1 21,3 28,1 25,6 1,3 21,7 21,7 17,5 18,9 35,8 ME-MS81 Yb 2,07 1,45 0,81 2,7 2,46 2,08 2,34 2,74 2,22 2,41 2,39 3,2 2,09 1,04 0,93 2,49 1,19 2,22 2,4 2,42 1,85 2,51 0,14 2,07 2,14 1,27 1,32 2,99 ME-MS81 Zr 58 59 9 74 66 55 90 119 183 167 164 143 200 89 108 70 6 44 120 81 39 71 8 76 50 158 135 155 ME-MS42 As >250 173,5 61 88,6 >250 >250 >250 126,5 7,4 45,9 18,6 5,7 3,8 >250 76,6 33,5 >250 132 2,6 28,7 64,9 >250 70,6 219 >250 156 9,8 20 ME-MS42 Bi 0,12 0,15 0,1 0,18 0,07 0,12 0,2 0,8 0,11 0,3 0,27 0,43 0,15 0,5 0,18 0,02 0,78 0,96 0,3 0,03 0,05 0,13 0,17 0,1 0,16 0,1 0,15 0,88 ME-MS42 Hg <0.005 0,006 <0.005 0,005 <0.005 <0.005 <0.005 0,009 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 <0.005 0,007 0,009 0,006 <0.005 0,026 <0.005 <0.005 0,029 0,013 0,023 0,012 0,246 ME-MS42 Sb 0,43 0,61 0,42 0,14 0,5 0,35 0,17 0,1 0,05 0,13 0,05 0,06 <0.05 16,95 4,36 0,23 0,25 0,14 0,05 0,24 0,24 0,54 0,11 0,22 0,36 0,1 0,05 <0.05 ME-MS42 Se 0,8 0,6 0,7 0,7 0,8 0,8 2,7 10,7 2 0,7 0,9 10,5 1,2 0,3 0,6 0,5 13,3 12,4 4,6 0,6 0,9 0,2 2,1 0,7 0,7 1,2 0,9 1,3 ME-MS42 Te 0,04 0,02 0,02 0,02 0,05 0,06 0,09 0,3 0,05 0,03 0,03 0,25 0,03 0,04 0,02 0,02 1,31 0,43 0,1 0,02 0,02 0,02 0,08 0,04 0,08 0,06 0,01 0,06 ME-4ACD81 Ag <0.5 <0.5 <0.5 <0.5 <0.5 0,5 0,7 1,5 0,6 <0.5 <0.5 0,9 <0.5 <0.5 <0.5 0,5 2,8 1,6 0,6 0,5 0,5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 0,7 ME-4ACD81 Cd <0.5 <0.5 <0.5 0,8 <0.5 <0.5 0,7 4,7 <0.5 <0.5 <0.5 2,2 <0.5 <0.5 <0.5 <0.5 1 1,6 1,8 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 ME-4ACD81 Co 53 67 5 44 44 35 84 24 19 21 21 28 11 84 85 45 <1 1 30 43 14 46 3 68 47 73 63 15 ME-4ACD81 Cu 183 49 88 114 185 119 255 307 190 37 81 175 35 26 100 199 503 133 111 178 49 3 109 111 187 123 285 36 ME-4ACD81 Mo <1 <1 1 <1 <1 <1 <1 18 1 1 1 26 1 <1 1 <1 <1 3 8 <1 1 <1 1 <1 <1 <1 <1 <1 ME-4ACD81 Ni 105 221 12 110 64 59 141 145 69 76 79 267 38 1005 989 102 65 28 236 100 48 101 15 143 99 214 211 46 ME-4ACD81 Pb <2 <2 <2 4 6 2 15 16 17 16 28 20 13 <2 6 2 6 15 12 7 2 5 <2 <2 <2 2 <2 5 ME-4ACD81 Zn 104 103 39 127 94 91 161 442 138 100 118 250 71 76 98 110 89 133 377 94 59 96 12 125 100 150 104 93 Au-AA23 Au ppm 0,058 0,02 <0.005 0,014 0,151 0,015 0,007 <0.005 0,005 0,006 0,006 0,009 0,015 0,064 0,007 0,02 0,657 1,04 0,006 0,007 0,012 0,146 0,059 0,023 0,022 0,005 <0.005 0,037
87
Appendix 1, cont. Method % SV071 SV072 PS010 PS011 PS012 PS013 PS014 PS015 PS016 PS017 PS018 PS019 PS021 PS023 PS025 PS026 PS029 PS045 PS046 PS047 PS048 PS049 ME-ICP06 SiO2 53,1 47,9 41,2 43,9 42,3 94,4 79,6 46,7 38,3 34,9 42 44,5 45,6 50,1 46 41,3 76,8 70,8 70,2 70,8 67,2 68,7 ME-ICP06 TiO2 0,64 1,24 1,4 1,55 1,28 0,01 0,02 1,5 1,26 1,21 1,58 1,16 1,33 1,03 1,3 1,39 0,03 0,21 0,23 0,19 0,34 0,42 ME-ICP06 Al2O3 12 13,15 16,3 17,95 15,05 0,05 0,15 17,75 14,95 13,8 17,9 15,3 14,75 14,8 15,9 17,05 13 15,35 15,95 15,45 16,5 15,75 ME-ICP06 CaO 2,92 14,4 16,9 11,15 18,6 0,04 0,44 11,6 18,4 19,45 12,15 13,8 6,81 7,88 12,65 14,35 1,6 0,38 0,43 0,58 1,7 1,02 ME-ICP06 Fe2O3 10,35 13,4 8,67 12,7 11 3,07 10,75 7,92 8,58 10,75 14,25 15,4 14,95 12,15 13,8 14,15 1,05 2,34 1,95 1,8 3,64 3,86 ME-ICP06 K2O 1,68 0,14 1,42 0,3 0,14 <0,01 0,01 0,26 0,71 0,29 0,29 0,9 0,07 0,14 0,37 0,26 0,37 3,64 0,85 2,63 1,46 1,14 ME-ICP06 MgO 3,4 6,28 3,78 5,67 4,73 0,01 0,43 4,56 4,76 6,41 6,58 4,88 8,38 6,94 3,31 6,65 0,1 0,12 0,12 0,09 0,82 0,54 ME-ICP06 Na2O 3,64 1,76 2,19 2,66 1,57 <0,01 0,01 3,56 2,42 1,72 1,67 1,52 2,82 2,43 2,24 1,58 6,28 5,91 8,47 6,62 6,47 6,56 ME-ICP06 MnO 0,05 0,19 0,13 0,22 0,19 0,01 0,02 0,17 0,21 0,24 0,21 0,22 0,26 0,18 0,19 0,22 0,02 0,04 0,03 0,04 0,08 0,14 ME-ICP06 Cr2O3 0,03 0,02 0,03 0,04 0,03 <0,01 0,01 0,04 0,03 0,03 0,04 0,03 0,03 0,03 0,03 0,04 <0,01 <0,01 <0,01 <0,01 0,01 0,01 ME-ICP06 P2O5 0,13 0,08 0,25 0,11 0,1 <0,01 <0,01 0,12 0,15 0,34 0,21 0,06 0,06 0,04 0,07 0,12 <0,01 0,02 0,02 0,02 0,05 0,03 ME-ICP06 SrO 0,02 0,03 0,02 0,02 0,02 <0,01 <0,01 0,02 0,02 0,01 0,02 0,02 <0,01 0,01 0,02 0,02 0,01 0,02 0,02 0,02 0,03 0,02 ME-ICP06 BaO 0,05 <0,01 0,05 0,01 <0,01 <0,01 <0,01 0,01 0,02 0,01 0,01 0,01 <0,01 <0,01 <0,01 0,01 <0,01 0,04 0,01 0,04 0,04 0,02 OA-GRA05 LOI 7,88 0,5 5,1 1,89 3,7 0,5 7,96 3,19 9,27 10,05 1,9 2,18 4,09 3,49 2,29 2,79 0,7 1,69 1,29 0,7 1,39 1,8 TOT-ICP06 Total 95,9 99,1 97,4 98,2 98,7 98,1 99,4 97,4 99,1 99,2 98,8 100 99,2 99,2 98,2 99,9 100 100,5 99,6 99 99,7 100 C-IR07 C 5,68 0,09 1,43 0,19 1,02 0,04 2,35 0,26 2,22 2,23 0,18 0,25 0,1 0,06 0,04 0,45 0,11 0,05 0,12 0,06 0,14 0,08 S-IR08 S 3,25 0,17 1,23 0,38 0,08 0,38 8 0,1 0,22 0,39 0,31 0,23 0,05 0,01 0,35 0,28 0,16 0,36 0,16 0,19 0,08 0,38 ppm ME-MS81 Ba 499 24,1 390 93,3 33 1 12 57 193,5 50,8 86,3 120,5 9,4 17,3 39,8 84,8 9,6 324 92,8 341 370 153,5 ME-MS81 Ce 57,6 11,8 10 10,9 9 <0,5 0,7 11,1 8,7 7,4 11,2 8,3 6,8 5,5 8 7,2 15 157 42,9 60,4 72,2 114,5 ME-MS81 Cr 270 180 220 250 210 30 40 260 200 190 260 250 220 200 230 250 10 10 10 10 40 60 ME-MS81 Cs 25,3 3,91 3,69 1,93 0,81 0,04 0,16 1,14 1,52 1,24 1,16 2,89 0,28 0,92 1,6 1,41 0,5 0,57 0,45 0,57 2,88 1,19 ME-MS81 Dy 5,65 4,22 5,04 5,73 4,63 0,08 0,46 5,85 4,7 4,16 6,14 5,38 4,62 3,7 4,98 5,41 12,95 2,67 1,53 1,74 2,2 4,2 ME-MS81 Er 3,5 2,67 3,15 3,47 2,82 0,05 0,28 3,61 2,84 2,68 3,75 3,4 2,76 2,24 3,01 3,4 8,45 1,37 1 1,21 1,52 2,09 ME-MS81 Eu 1,23 1,1 1,02 1,24 0,97 <0,03 0,05 1,26 1 0,84 1,22 1,58 0,76 0,73 0,95 0,99 0,27 0,99 0,62 0,58 0,79 1,14 ME-MS81 Ga 18,9 18,8 17,2 21,6 16,4 0,6 0,9 22,4 17,4 19 20,8 21,1 16,1 16,3 17,7 19,3 21,7 25,8 28,2 27 29,1 29,6 ME-MS81 Gd 5,97 3,96 3,58 3,99 3,38 0,1 0,38 4,1 3,37 3,03 4,36 3,56 3,36 2,76 3,58 3,7 7,75 3,84 1,52 1,6 2,29 5,36 ME-MS81 Hf 4,3 2,1 2,1 2,3 1,8 <0,2 0,3 2,5 1,8 1,9 2,3 1,9 1,5 1,1 1,8 1,7 11,3 11 11,8 12,6 12,6 12,1 ME-MS81 Ho 1,17 0,9 1,05 1,19 0,96 0,02 0,09 1,22 0,97 0,88 1,28 1,14 0,93 0,75 1,03 1,13 2,66 0,49 0,31 0,37 0,47 0,75 ME-MS81 La 28,3 4,7 3,9 4,2 3,4 <0,5 <0,5 4,2 3,3 2,9 4,5 2,9 2,5 1,9 3,1 2,6 4,7 90,3 20,7 41,3 37 63,2 ME-MS81 Lu 0,57 0,4 0,49 0,55 0,44 0,01 0,06 0,57 0,48 0,47 0,61 0,56 0,42 0,34 0,47 0,56 1,58 0,27 0,23 0,28 0,35 0,4 ME-MS81 Nb 9 3,8 5 5,5 4,4 <0,2 0,6 5,4 4,5 4,5 5,5 3,9 3,6 2,3 3,7 4,3 63,6 30,5 33,5 22,9 36,7 74,6 ME-MS81 Nd 28,8 9,3 8,3 9 7,5 0,4 1 9 7,1 6,2 9,5 7,8 6,6 5,3 7,2 6,7 12,1 45,6 13,8 16,1 21,5 41,9 ME-MS81 Pr 7,08 1,79 1,56 1,67 1,4 0,06 0,17 1,75 1,34 1,13 1,76 1,39 1,13 0,92 1,31 1,15 2,48 14,9 4,36 5,29 6,77 12,1 ME-MS81 Rb 71,7 4,5 70,5 21,7 9,3 0,2 0,7 18 51,1 17,4 17,6 48 2,4 7,1 30,4 15,7 25,3 78,3 25 59,9 75,1 55,1 ME-MS81 Sm 6,41 3,01 2,8 3,07 2,51 0,08 0,33 3,06 2,43 2,15 3,2 2,75 2,49 2 2,58 2,48 6,06 6,06 2,23 2,31 3,21 7,32 ME-MS81 Sn 2 1 1 1 1 <1 <1 1 4 6 1 4 1 <1 4 <1 1 2 1 1 2 6 ME-MS81 Sr 175,5 268 145 188,5 203 0,5 1 222 169 65,9 192 236 27,6 78,8 185 157,5 75,2 156,5 138 173 269 205 ME-MS81 Ta 0,8 0,3 0,3 0,3 0,3 <0,1 <0,1 0,3 0,3 0,3 0,3 0,3 0,2 0,1 0,2 0,2 9,2 1,5 1,6 1,2 1,8 2,6 ME-MS81 Tb 0,98 0,69 0,69 0,81 0,63 0,01 0,06 0,81 0,65 0,58 0,86 0,72 0,63 0,51 0,68 0,74 1,78 0,51 0,24 0,27 0,35 0,76 ME-MS81 Th 8,63 0,42 0,36 0,38 0,29 0,09 0,1 0,38 0,33 0,31 0,45 0,21 0,17 0,14 0,24 0,2 32,3 28,5 29,5 31,2 32,2 28,3 ME-MS81 Tl 0,7 <0,5 <0,5 <0,5 <0,5 <0,5 0,8 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 ME-MS81 Tm 0,54 0,42 0,48 0,52 0,42 0,01 0,05 0,55 0,45 0,42 0,59 0,51 0,41 0,34 0,46 0,5 1,48 0,23 0,18 0,21 0,26 0,33 ME-MS81 U 11,9 0,2 15,35 1,1 1,13 3,36 1,36 2,28 5,93 29 16,7 0,13 0,12 0,07 0,73 6,74 34,3 14,2 11,8 11,3 14,15 15,15 ME-MS81 V 314 380 243 288 240 21 222 294 249 235 318 305 274 215 265 275 <5 5 6 5 41 15 ME-MS81 W 1 2 1 <1 1 2 1 2 2 2 <1 2 2 2 10 1 <1 5 4 43 3 519 ME-MS81 Y 31,6 24,6 28,1 30,9 25,6 0,5 2,4 31,4 26,4 24,4 34,4 30,2 24,9 20,9 27,6 30 65,1 15 9,8 12 15,1 23,2 ME-MS81 Yb 3,46 2,53 3,27 3,62 2,9 0,06 0,35 3,84 3,13 2,95 4,16 3,62 2,82 2,33 3,04 3,48 10,55 1,68 1,41 1,66 2,08 2,49 ME-MS81 Zr 154 77 69 77 59 <2 9 85 62 62 75 58 46 35 61 54 165 538 580 619 618 568 ME-MS42 As 4,1 22,8 9,7 4,6 1,5 47,2 18,3 15,3 32,9 81,5 2,7 20,9 15 2,7 42 4,9 3 110 114 >250 >250 >250 ME-MS42 Bi 0,7 0,04 0,12 0,03 0,01 0,11 1,93 0,05 0,1 0,15 0,02 0,06 0,04 0,02 0,06 0,03 3,34 0,26 0,54 0,22 0,62 1,15 ME-MS42 Hg 0,006 <0,005 <0,005 <0,005 <0,005 <0,005 0,006 <0,005 <0,005 <0,005 <0,005 <0,005 0,005 0,006 0,02 <0,005 <0,005 0,012 0,007 0,099 0,007 0,916 ME-MS42 Sb 0,1 0,16 0,16 0,19 0,14 0,46 0,41 0,24 0,28 0,37 0,16 0,41 0,39 0,14 0,61 0,22 0,16 0,19 0,21 0,54 0,82 1,12 ME-MS42 Se 9,1 1 1,1 0,9 0,6 2,5 32,4 0,8 0,8 0,8 1 0,7 0,6 0,5 1,2 0,9 2 0,8 0,5 0,6 0,7 1,2 ME-MS42 Te 0,26 0,04 0,03 0,02 0,02 0,01 0,29 0,02 0,02 0,02 0,02 0,02 0,02 0,01 0,01 0,01 0,04 0,07 0,15 0,17 0,17 0,75 ME-4ACD81 Ag 0,6 <0,5 0,5 <0,5 <0,5 <0,5 2,2 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 <0,5 1,1 0,7 2,1 0,8 2,5 ME-4ACD81 Cd 1,8 <0,5 <0,5 <0,5 <0,5 <0,5 4,9 <0,5 <0,5 <0,5 <0,5 <0,5 0,8 <0,5 <0,5 <0,5 <0,5 1,4 0,6 <0,5 <0,5 4,6 ME-4ACD81 Co 31 45 45 49 43 2 22 54 40 47 52 50 52 41 52 51 2 1 1 <1 3 5 ME-4ACD81 Cu 168 259 120 179 122 34 197 108 64 90 118 144 88 98 173 97 70 12 9 6 24 13 ME-4ACD81 Mo 24 <1 <1 <1 <1 4 35 <1 <1 <1 2 <1 <1 <1 <1 <1 <1 1 <1 1 11 6 ME-4ACD81 Ni 230 94 104 89 80 11 148 87 77 76 141 114 124 97 111 125 1 2 <1 <1 9 15 ME-4ACD81 Pb 15 2 7 2 <2 6 16 6 8 17 6 3 6 <2 4 4 62 30 17 56 28 43 ME-4ACD81 Zn 342 98 92 162 87 19 280 143 130 189 157 107 116 97 131 115 72 127 52 15 60 505 Au-AA23 Au 0,013 0,008 <0,005 <0,005 0,005 <0,005 0,007 0,005 0,005 0,009 <0,005 0,007 0,008 <0,005 0,005 <0,005 0,035 0,1 0,057 >10,0 0,527 7,72 Au-GRA21 Au ------26 - -
88
Appendix 2, Grundfors profiles Profile 1
Profile 2
89
90