UNIVERSITY OF GOTHENBURG Department of Earth Sciences Geovetarcentrum/Earth Science Centre

Zircon dating of

the Uddevalla Granite

Erik Jansson

ISSN 1400-3821 B873 Bachelor of Science thesis Göteborg 2016

Mailing address Address Telephone Telefax Geovetarcentrum Geovetarcentrum Geovetarcentrum 031-786 19 56 031-786 19 86 Göteborg University S 405 30 Göteborg Guldhedsgatan 5A S-405 30 Göteborg SWEDEN Abstract U-Pb and Pb-Pb dating of from a granite massif near Uddevalla, SW Sweden, gives an age indication of a syn-collisional intrusion event. Main domain zircons give a concordia U-Pb age of 1027 ±9 Ma (2σ) which is interpreted to be the crystallization age of the massif which should be called the Uddevalla Granite. Older xenocryst cores and rim overgrowths with ages from 1181 ±62 Ma to 1872 ±50 Ma are derived from older crustal material. The granite is likely to be a product of syntectonic peak metamorphism due to crustal thickening in the Idefjorden Terrane during the Sveconorwegian continental collisional orogeny.

Keywords: Uddevalla Granite, , Sveconorwegian, Western Segment, peak metamorphism, oscillatory growth zoning, U-Pb dating, LA-ICP-MS.

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Abstrakt U-Pb och Pb-Pb-dateringar av zirkoner från ett granitiskt bergsmassiv, situerat nära Udddevalla sydvästra Sverige, ger en åldersindikation av en kollisionsrelaterad intrusion. Zirkonernas huvuddomän ger en concordia U-Pb-ålder på 1027 ±9 Ma (2σ) vilket tolkas vara kristalliseringsåldern för bergsmassivet som bör kallas för Uddevallagraniten. Äldre xenocryster och tillväxtkanter med åldrar från 1181 ±62 Ma till 1872 ±50 Ma, är ett resultat av återanvänt skorpmaterial. Graniten är troligtvis en produkt av syntektonisk peak-metamorfos, genom förtjockning av skorpan, inom Idefjorden Terrane under den Sveconorwegiska orogenesen.

Keywords: Uddevalla Granite, zircon, Sveconorwegian, Western Segment, peak metamorphism, oscillatory growth zoning, U-Pb dating, LA-ICP-MS.

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Contents Abstract ...... 1 Abstrakt ...... 2 Introduction ...... 4 Geological setting ...... 4 Hisingen Suite ...... 5 Stora Le Marstrand formation ...... 5 Samples and methods ...... 6 Samples ...... 7 Methods ...... 8 Results ...... 12 TEN150004 Red granite, Skredsvik ...... 13 DC1501 Red granite, Frölandskrossen ...... 15 TEN150001 Red granite, Kissleberg...... 17 Discussion ...... 19 TEN150004 ...... 19 DC1501 ...... 19 TEN150001 ...... 19 Age correlations ...... 20 Further studies ...... 20 Conclusion ...... 20 Acknowledgements ...... 20 References ...... 21

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Introduction A partly large, pegmatitic granite intrusion is accretion with crust of older ages closer to situated in the Sveconorwegian Province Finland and continuously younger ages (figure 1) near the town Uddevalla, Swedish westwards throughout the Baltic Shield. west coast. The intrusive massif, henceforth However this model is not universally referred to as the Uddevalla Granite, is usually associated with the larger adjacent Bohus accepted and another suggestion is that the Granite at 920 ±5 Ma (e.g. Bingen et al. 2008). Sveconorwegian metamorphic event occurred The Uddevalla granite is categorized as a between 1140 and 900 Ma where exotic . It shows a weak shear terranes are thought to have collided with deformation and is cross cut by undeformed western Baltica (Hegardt, 2010) and formed (Fazic, 2016). This suggests late the Sveconorwegian Province. The peak stages of deformation in the area. The granite metamorphism in the Telemarkia and is oriented in a northwest to southeast direction and stretches for approximately 27,5 Idefjorden Terrane occurred between 1040 km from Ljungskile to Munkedal (figure 2). The and 980 Ma (Romer and Smeds, 1996; Bingen intrusion cross cuts N-S trending rock et al. 2008; Hegardt, 2010). During this period formations such as the Hisingen Suite (or the Telemarkia Terrane experienced a crustal Frölunda Suite) in the eastern part of the thickening and metamorphic facies varying massif and the Stora Le Marstrand Formation from granulite to lower amphibolite. During in the middle and western part of the massif. the same time the Idefjorden Terrane Geochemical data and field observations from Fazic (2016) combined with dating of the underwent amphibolite facies metamorphism massif could provide an age marker (Bingen et al. 2008). Hegardt (2010) used Sm- representing late stage deformation. The aim Nd analyses from amphibolite to date of this study is mainly to date the intrusion the F3 folds from the D3 deformation on and the crystallization of the using Nordön Island which yield the age 1029 ±6 laser ablation microbeam U-Pb zircon dating. Ma. The age represents the peak Geological setting metamorphism in the Western Segment. The Sveconorwegian Province can be divided Granitic intrusions in the Western into four tectonostratigraphic units which are and Eastern segments are associated with the the Telemarkia terrane, the Bamble- peak metamorphism and are indications of Kongsberg Terranes, the Idefjorden Terrane syn-collisional magmatism (summarized by and the Eastern Segment (Bingen et al. 2008) Bingen et al. 2008). Romer and Smeds (1996) which can be seen in figure 1. The Idefjorden dated pegmatites located throughout the Terrane east of the Oslo Rift is also known as Western and Eastern Segment, using the Western and the Median Segment which conventional U-Pb ages on columbite (see is divided from the Eastern Segment by the figure 3). They state that the pegmatites must Mylonite Zone (Bingen et al. 2001). The originate from larger granitic bodies due to Western and the Median Segment, often their high content of rare minerals. Ages of called only the Western Segment, consists of the pegmatites were determined through U- volcanic, plutonic and sedimentary rocks Pb columbite dating and gave ages of 1038.7 produced by a magmatic arc (Andersen et al. ±3.4 Ma, 1041.3 ±1.6 Ma, 1029.7 ±1.4 Ma, 2004) around 1660-1520 Ma (Åhäll and 984.3 ±6.4 Ma and 941.6 ±1.4 Ma (figure 3). Connelly, 2008). According to Åhäll and The Sveconorwegian metamorphic event Connelly (2008) the Western Segment is the resulted in crustal reworking that, with an product of continuous westward growth or orogenic center around the Mylonite Zone, created the gneissic fabric seen in formations

4 throughout the Western Segment such as the intrusions, with intermediate composition, Hisingen Suite (Mell, 2005). The Bohus Granite occurred mainly in the early and late stages of at 920 ±5 Ma is one of the late the Hisingen magmatism, around 1550–1552 Sveconorwegian granitic intrusions which Ma (Åhäll and Connelly, 2008). The rock shows marks the end of a long period of plutonism gneissic features and is mainly granodioritic, (Magnusson, 1960; Eliasson and Schöberg, but also varies from granitic to a tonalitic 1991). composition (Mell, 2005).

Hisingen Suite Stora Le Marstrand formation Previously interpreted to be part of the The Stora Le Marstrand (SLM) formation yields Göteborg Suite, the younger Hisingen Suite a minimum depositional age of 1590 Ma (Åhäll (also referred as the Frölunda Suite by Mell, et al. 1998) and originates from volcanic 2005) intruded the Stora Le Marstrand basalts, volcanoclastic rocks and greywackes Formation at 1588–1522 Ma. It consists of (Åhäll and Connelly, 2008). According to Åhäll mainly granitoid intrusions, but it also includes and Connelly (2008) and Åhäll (1989) the mafic to felsic bodies (Åhäll and Connelly, lithology of SLM is derived from a mature 2008). Many of the intrusive bodies formed back-arc setting where sediment shows during late to final stages of the Gothian similarities to that of Svecofennian crust and (around 1620-1550 Ma) and intruded due to mafic volcanics. Due to the Sveconorwegian subduction related magmatism (Åhäll and metamorphic event, the SLM has undergone Larsson, 2000; Mell, 2005). The granitoid crustal reworking.

Figure 1 Modified map from Hegardt (2010), showing the major terranes of the Sveconorwegian Province. Western & Median Segment also known as Idefjorden Terrane.

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Figure 2 Simplified geological map showing sampling site in the Uddevalla Granite. The map is modified with data from SGU and originally compiled by Thomas Eliasson, SGU.

Figure 3 Modified map from Romer and Smeds (1996). The figure shows locations of pegmatites dated by Romer and Smeds (1996) and the location of the Uddevalla Granite, also showing the post-orogenic Bohus Granite.

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Samples and methods minerals. Garnet occurs as an accessory mineral. The sample site shows frequent Samples occurrences of pegmatite veins. Samples labelled TEN were collected by DC1502 Red granite, Frölandskrossen Thomas Eliasson (SGU). For sample location, see figure 2. N6470714 E316376

TEN150001 Red granite, Kissleberg The sample was collected at Frölandskrossen. At this site, the intrusion is a coarse-grained (2 N 6472731 E 315395 to 100 mm) granitic pegmatite. Muscovite, The sample was collected at Kissleberg. This is and alkali are the major a red medium to fine grained (2-4 mm) minerals. Garnet occurs as an accessory homogenous granite. Biotite, quartz, mineral. muscovite and alkali feldspar are the major DC1506 Gray granite, Torp, Uddevalla minerals. The sample site shows minor occurrences of pegmatitic and aplitic veins. N6472786 E313343

TEN150003 Grey granite, Kallsås The sample was collected at a roadcut, Torp. This is a light grey, fine grained (2-4 mm in N6478429 E309159 size) granite. Muscovite, quartz, , The sample was collected at Kallsås, NCC Rads garnet and alkali feldspar are the major AB. It is a grey medium to fine grained (2-5 minerals. mm) granite with a vague foliation. Biotite DC1507 Gray granite, Torp, Uddevalla quartz, alkali feldspar, plagioclase and garnet are the major minerals. The sample site shows N6472786 E313343 occurrences of pegmatite veins. The sample was collected at a roadcut, Torp. TEN150004 Red granite, Skredsvik This is a light grey, fine grained (2-4 mm) granite. Muscovite, quartz, plagioclase and N6480736 E306970 alkali feldspar are the major minerals. Garnet The sample was collected at Skaveröd, occurs as a major accessory mineral. The Skredsvik. This is a red fine to medium grained sample site shows intercalated pegmatitic to (1-3 mm in size) homogenous granite with a aplitic bands. weak foliation. Biotite, quartz and alkali feldspar are the major minerals. The sample site shows largely homogenously granite and no apparent pegmatite veins.

DC1501 Red granite, Frölandskrossen

N6470714 E316376

The sample was collected at Frölandskrossen. This is a red medium grained (5 mm) homogenous granite. Muscovite, biotite, quartz and alkali feldspar are the major

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Methods (See figure 4, 6, 8, 10, 14, 16 and 20). The Sample preparation overgrowth rims were identified as CL grey main domains lacking oscillatory growth Samples and hand specimen were collected at zoning or as CL dark rim overgrowths. The different location of the massif. Each sample images were also used for determining viable consisted of a larger hand specimen and six of spots for the analysis. The spots were selected the samples also comprised of 2 – 4 kg of cm- in terms of cores, rims and mains. Cracks seen sized fragments. The smaller rock material in the BSE images were avoided. The analyses was crushed to pass a 400 µm sieve. Heavy were done using a laser ablation sampler minerals (i.e. zircon, garnet and magnetite) connected to an inductively coupled plasma were extracted from the samples by panning. mass spectrometer (LA- ICP-MS). The laser is a Magnetic separation was used with an model ESI 213 NWR with a TV2 sample intensity of 0.5 ampere and 1.0 ampere to chamber (fast washout) and with a He flow of remove the majority of magnetic minerals 0.9 ml/min and a N2 flow of 4 ml/min. The ICP- from the samples. Zircons with size ranging MS is a model Agilant 8800 QQQ, simple quad from 50 µm up to 400 µm were handpicked mode. The LA-ICP-MS was set to 50% output under a microscope. The extracted zircons with 20 µm spot size at 5 Hz and a fluence of from sample TEN150001, TEN150003, 4.3 J/cm2. TEN150004, DC1501 and DC1502 were cast into an epoxy puck and polished for imaging The zircon grains were analyzed using the and analysis. Three of the original six different 91500 zircon as a primary standard and the samples were used in dating the Uddevalla GJ, KVT and Temora as control standards. Four Granite. Sample TEN150003, DC1502 and primary standard and four control standard DC1507 suffered a loss of grains during spots were taken after every six zircon spots polishing of the puck and contained too few that were analyzed. Each spot was analyzed zircons to be properly analyzed. for 50 seconds and a total of 252 spots were analyzed including the standards. Due to a loss Spot selection and LA-ICP-MS of zircons during polishing of the puck the only samples analyzed were TEN150001, The mineralogy of the samples was confirmed TEN150004 and DC1501. The data obtained using a scanning electron microscope (SEM). from the LA-ICP-MS analysis were processed The SEM was also used in making Cathodo- in an in-house Microsoft Excel spreadsheet luminescence (CL) and back-scatter electron and ages were calculated using Isoplot 4.15 (BSE) images of the samples which were used (Ludwig 1991, 1998). The measured Th/U for interpreting age domains seen in the ratios and the occurrence of growth zoning zircons (See figure 4 to 21). The CL and BSE were used to confirm the metamorphic or images were also used to recognize metamict magmatic origins of the age domains. parts of the zircons which appear dark in both Magmatic zircons show high Th/U (usually CL and BSE images. Main magmatic domains >0.4) and metamorphic zircon show low Th/U in zircon were identified through growth (e.g. Wu and Zheng, 2004). The resulting data zoning textures in CL images which reflect was plotted and dates calculated with U-Pb growth from a magma (See figure 10, 12 and discordia regression plots, U-Pb concordia 18). Xenocryst cores were identified as ages and Pb-Pb weighted average ages. domains in which the zonation is usually truncated and overgrown by main domains

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Figure 4 Cathodo-luminescence image of the analyzed Figure 5 Back scatter image of the analyzed grains 18, 19, 20 grains 18, 19, 20 and 22 from sample TEN150001 showing and 22 from sample TEN150001. Red and yellow circles xenocryst cores (18a and 20b) with grey main domain rims show the spots analyzed. (20a) and CL dark rim (18b).

Figure 6 Cathodo-luminescence image of the analyzed grain Figure 7 Back scatter image of the analyzed grain 38 from 38 from sample TEN150001 showing a xenocryst core (b), sample TEN150001. Red circles show the spots analyzed. grey main domain without oscillatory zoning (a) and CL dark rim (c).

Figure 8 Cathodo-luminescence image of the analyzed Figure 9 Back scatter image of the analyzed grain 39 from grain 39 from sample TEN150001 showing a xenocryst core sample TEN150001. Red and yellow circles show the spots with oscillatory growth zoning (b, c, e, f), bright main analyzed. domain (d and e) and a CL dark rim surrounding the main domain.

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Figure 10 Cathodo-luminescence image of the analyzed Figure 11 Back scatter image of the analyzed grains 120, grains 120, 123, 124 and 125 from sample TEN150004 123, 124 and 125 from sample TEN150004. Red and yellow showing main domain oscillatory growth zoning (120a – d circles shows the spots analyzed. and 124a, b) and CL dark rims (125a, b).

Figure 12 Cathodo-luminescence image of the analyzed Figure 13 Back scatter image of the analyzed grains 155 and grain 155 and 157 from sample TEN150004 showing main 157 from sample TEN150004. Red circles show the spots domain zircons with oscillatory growth zoning (157b-e, analyzed. 155a, b). 157a shows a CL dark rim.

Figure 14 Cathodo-luminescence image of the analyzed Figure 15 Back scatter image of the analyzed grains 159 and grains 159 and 162 from sample TEN150004 showing main 162 from sample TEN150004. Red circles show the spots domain CL grey (159) and xenocryst core (162a) with a CL analyzed. grey rim separating the core from a main domain CL bright rim (162b),.

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Figure 16 Cathodo-luminescence image of the analyzed Figure 17 Back scatter image of the analyzed grains 159 and grains 52, 55 and 56, from sample DC1501 showing 52, 55 and 56 from sample DC1501. Red and yellow circles xenocryst cores (55c, 56 and 52), main domain grey without show the spots analyzed. oscillatory growth zoning (a, b and d) and CL dark rims.

Figure 18 Cathodo-luminescence image of the analyzed FigurFiguree 1919 BackBack scatterscatter imageimage ofof thethe analyzedanalyzed graingrain 6060 fromfrom grain 60 from sample DC1501 showing main domain samplesample DC1501.DC1501. RedRed circlecircle showshow thethe spotspots analyzed. analyzed. zircon with oscillatory growth zoning and no xenocryst core.

Figure 20 Cathodo-luminescence image of the analyzed Figure 21 Back scatter image of the analyzed grains 70 and grains 70 and 73 from sample DC1501 showing bright 73 from sample TEN150004. Red and yellow circles show the xenocryst cores (a) with surrounding grey main domain(b spots analyzed. and c) and a CL dark rim.

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Results The resulting ages from the three samples analyzed are shown in table 1.

domains,than discordance) discordance 5% ages, of calculation. (lower and type Table1 TEN150001 DC1501 TEN150004

Sample

Summaryof the

20b 22 39(b,c,e,f) 28b 39d 39a 42b 42c 42(b,c) 70 53 42a 42d, 50b 46b 60, 55(a,b), 75, 115 162a 146b 162b 157b, 169(b,c) 157(c,d,e), 155(a,b), 152(a,b), 136(a,b), 132(a,b), 124(a,b), 123, 120(a,b,c,d), 107a, 124a 123, 120(a,b,c,d),

three

samples analyzed. The sample analyses are samplesare analyzed. The groupedsample in analyses of terms Spot number Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Pb-Pb Concordia Age

Calculation

Age 1623 1546 1312 1180 1183 1055 1872 1759 1683 1527 1308 1625 1232 1028 1754 1312 1196 1061 1023 1027 Error 2 Error ±118 ±122 ±14 ±76 ±74 ±50 ±76 ±50 ±50 ±44 ±42 ±82 ±37 ±68 ±29 ±48 ±70 ±52 ±49 ±9 σ MSWD 0,0023 0,044 0,095 0,66 0,19 0,96 1,2 0 0 0 0 0 0 0 0 0 0 0 0 Prob 0,99 0,42 0,96 0,94 0,76 0,33 0,2 1 1 1 1 1 1 1 1 1 1 1 1 1 Points 21 1 1 4 1 1 1 1 1 2 1 1 2 1 5 1 1 1 2 6 <1400 Pb-Pb <1400 Pb-Pb <1100 >1500Pb-Pb Pb-Pb >1300 Pb-Pb <1300 <5% Discordant Comments Xenocryst Xenocryst Xenocryst Rim Main Domain Main Domain Xenocryst Xenocryst Xenocryst Xenocryst Xenocryst Rim Rim Main Domain Xenocryst Xenocryst Xenocryst Rim Main domain Main domain

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TEN150004 Red granite, Skredsvik TEN150004 consists of 42 analyses from 21 oscillatory growth zoning (black ellipses figure different zircon grains. 16 of the analyses are 22). A Concordia age for six main domain discarded due to inhomogeneous data or high points, that are <5% discordant, yields 1027 common lead. Figure 22 shows the remaining ±8.7 Ma (see table 2). Sample TEN150004 has 26 analyses. 14 of the zircon grains analyzed in two rim analyses from grains 162 and 157 sample TEN150004 are main domains and (green ellipses in figure 22). Analysis 162b is a have oscillatory growth zoning textures in the CL bright rim (see figure 14) with Pb-Pb age of zircons and a dark rim which can be seen in 1049 ±88 Ma and analysis 157b is a CL dark cathodo-luminescence images (see figure 10 rim (see figure 12) and gives a Pb-Pb age of and 12). Four analyzed zircons can be seen in 1066 ±60 Ma. The sample also has three figure 10 and 11 which shows three of the xenocryst core analyses (red ellipses in figure main zircons (grains 120, 123 and 124) and 22) with Pb-Pb ages 1196 ±52 Ma, 1312 ±70 one of the relic xenocryst cores with CL dark Ma and 1753 ±48 Ma (see table 1). rim overgrowth (grain 125). The Pb-Pb mean age for 21 points is 1023 ±14 Ma (see table 2). These are all in main domains showing

Figure 22 Sample TEN150004. Concordia plot showing xenocryst cores as red ellipses, rim overgrowths as green ellipses and main domain zircons as black ellipses. The blue ellipse shows the calculated 1027 ±8.7 Ma concordia age for six points. The 21 black ellipses give a Pb-Pb age of 1023 ±14 Ma.

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zircon ages. White marker s zirconWhite marker ages. Table2 C B A Batch TEN150004

Analyzed spots Analyzed sample shows from TEN150004. removedRed samples marker 169c 169b 169a 162b 162a 159 157e 157d 157c 157b 157a 155b 155a 152b 152a 146b 146a 145 136b 136a 132b 132a 125b 125a 124b 124a 123 120d 120c 120b 120a 118 116 115 108 107c 107b 107a 105b 105a 104b 104a Skredsvik. from Skaveröd, size, 1 with granite Red 4mm- grain Main Main Main Rim Core Rim Main Main Main Rim Rim Main Main Main Main Core Main Rim Main Main Main Main Rim Rim Main Main Main Main Main Main Main Core Main Core Main Main Main Main Rim Core Main Main Analysis

PbC PbC PbC Inhomogenous PbC PbC PbC PbC Inhomogenous Inhomogenous PbC PbC Inhomogenous Inhomogenous PbC PbC Comments howsanalysesto used obtain determinations age U 1484,42 1151,48 4588,01 143,65 138,74 162,95 688,53 123,04 181,40 166,70 597,72 501,20 515,67 883,43 383,86 399,90 642,28 557,44 976,66 875,30 297,27 306,24 268,51 297,27 306,24 283,44 357,46 224,60 198,86 213,81 779,41 691,00 234,23 116,60 348,68 19,75 13,74 87,56 75,07 77,66 66,97 37,77 Th 324,85 156,83 131,15 238,64 176,62 139,51 119,11 127,44 465,72 51,40 48,57 58,19 12,16 25,00 38,06 35,50 34,58 10,86 48,90 85,70 89,15 93,87 51,46 66,36 92,04 29,30 30,82 57,43 58,88 52,85 57,43 58,88 54,32 24,29 34,01 19,79 37,39 4,49 5,46 7,14 0,25 7,03 Th/U 0,36 0,35 0,36 0,23 0,89 0,04 0,43 0,47 0,45 0,04 0,06 0,29 0,14 0,18 0,11 0,22 0,18 0,18 0,13 0,17 0,20 0,17 0,03 0,04 0,19 0,19 0,21 0,20 0,19 0,19 0,19 0,49 0,00 0,70 0,11 0,15 0,18 0,15 0,19 0,17 0,10 0,11 208/232 Ratio #DIV/0! #DIV/0! #DIV/0! -22,1311 0,0552 0,0494 0,0489 0,0477 0,0681 0,6191 0,0490 0,0509 0,0485 0,0819 0,5264 0,0582 0,0587 0,0558 0,0529 0,0705 0,0493 0,0522 0,0550 0,0549 0,0514 0,0567 0,1754 0,3444 0,0533 0,0495 0,0493 0,0534 0,0482 0,0512 0,0548 0,1136 0,0899 0,1141 0,0528 0,0551 0,6710 0,1324 1 Error #DIV/0! #DIV/0! #DIV/0! σ -8,0774 0,0024 0,0022 0,0023 0,0084 0,0038 0,0279 0,0022 0,0024 0,0023 0,0051 0,0289 0,0028 0,0037 0,0032 0,0048 0,0044 0,0031 0,0029 0,0032 0,0031 0,0028 0,0030 0,0117 0,0188 0,0033 0,0032 0,0033 0,0037 0,0033 0,0035 0,0037 0,0082 0,0059 0,0074 0,0035 0,0040 0,1362 0,0104 207/235 Ratio #DIV/0!

1,6423 1,6254 1,5760 1,5192 2,4961 0,8935 1,5650 1,5776 1,5376 1,5925 2,1462 1,7033 1,8242 1,6618 1,5823 1,6220 1,4822 1,5805 1,6011 1,6381 1,5976 1,6128 1,8581 2,3391 1,8005 1,7437 1,7662 1,7806 1,7341 1,7320 1,7145 3,2155 1,7786 4,0827 1,9559 2,1071 1,6972 1,7480 2,4982 2,1359 1,4367

of the Uddevalla G ofUddevalla the 1 Error #DIV/0! σ

0,0813 0,0807 0,0786 0,0800 0,1267 0,0453 0,0777 0,0783 0,0764 0,0792 0,1085 0,0855 0,0778 0,0718 0,0706 0,0737 0,0644 0,0671 0,0682 0,0702 0,0682 0,0684 0,0800 0,0995 0,0649 0,0651 0,0660 0,0661 0,0644 0,0642 0,0640 0,1193 0,0663 0,1537 0,1009 0,0781 0,0630 0,0649 0,1874 0,1679 0,0576

duelead to analyses inhomogeneous or common 206/238 Ratio #DIV/0! 0,1601 0,1609 0,1553 0,1478 0,2130 0,0593 0,1539 0,1531 0,1505 0,1536 0,1588 0,1615 0,1748 0,1608 0,1585 0,1463 0,1427 0,1529 0,1574 0,1593 0,1583 0,1601 0,1657 0,1818 0,1800 0,1745 0,1742 0,1769 0,1738 0,1736 0,1718 0,2105 0,1756 0,2750 0,1856 0,1643 0,1656 0,1754 0,2264 0,1341 0,1045 1 Error #DIV/0!

σ ranite. 0,0094 0,0095 0,0092 0,0088 0,0126 0,0035 0,0091 0,0090 0,0088 0,0090 0,0094 0,0095 0,0077 0,0072 0,0071 0,0068 0,0064 0,0068 0,0070 0,0071 0,0070 0,0071 0,0073 0,0081 0,0060 0,0060 0,0060 0,0060 0,0059 0,0059 0,0059 0,0076 0,0060 0,0094 0,0079 0,0056 0,0056 0,0060 0,0119 0,0089 0,0040 rho

#DIV/0!

0,9787 0,9786 0,9781 0,9296 0,9578 0,9569 0,9756 0,9746 0,9731 0,9759 0,9726 0,9770 0,9520 0,9565 0,9108 0,9599 0,9209 0,9558 0,9531 0,9555 0,9577 0,9571 0,9539 0,9575 0,9465 0,9366 0,9370 0,9320 0,9302 0,9319 0,9332 0,9152 0,9310 0,9350 0,9095 0,9358 0,9353 0,9317 0,7004 0,9613 0,8835 207/206 Ratio 0,0741 0,0730 0,0733 0,0743 0,0848 0,1088 0,0736 0,0746 0,0739 0,0749 0,0972 0,0760 0,0754 0,0746 0,0724 0,0800 0,0753 0,0748 0,0737 0,0743 0,0729 0,0729 0,0809 0,0930 0,0723 0,0723 0,0733 0,0728 0,0722 0,0722 0,0722 0,1122 0,0733 0,1073 0,0761 0,0927 0,0741 0,0722 0,4932 0,0821 0,1043 0,1019 1 Error 0,0011 0,0011 0,0011 0,0016 0,0015 0,0020 0,0011 0,0011 0,0011 0,0011 0,0015 0,0011 0,0010 0,0010 0,0014 0,0010 0,0013 0,0010 0,0010 0,0010 0,0009 0,0009 0,0011 0,0012 0,0008 0,0009 0,0010 0,0010 0,0010 0,0010 0,0010 0,0017 0,0010 0,0014 0,0017 0,0012 0,0010 0,0010 0,1690 0,0044 0,0025 0,0019 σ 208/232 Age #DIV/0! #DIV/0! #DIV/0! #NUM! 10372 1085 1331 9735 1003 1591 8544 1143 1153 1098 1042 1377 1028 1081 1079 1013 1113 3264 5979 1049 1051 1009 1078 2173 1740 2182 1039 1084 2511 973 965 941 966 956 973 976 973 951 1 Error #DIV/0! #DIV/0! #DIV/0! #NUM! σ 1717 164 351 386 202 285 149 109 135 187 47 43 45 72 43 46 44 95 54 70 61 92 83 60 55 60 59 53 58 63 62 63 70 63 67 72 67 76 207/235 Age

#DIV/0! . Yellow . 1271 1164 1010 1054 1066 1224 1046 1025 1033 1038 1021 1020 1014 1461 1038 1651 1100 1151 1007 1026 1272 1161 987 980 961 938 648 956 961 946 967 994 963 979 923 963 971 985 969 975 904 1 Error #DIV/0!

σ

32 32 31 33 37 25 31 31 31 31 36 33 28 28 28 29 27 27 27 27 27 27 29 31 24 24 25 24 24 24 24 29 25 31 35 26 24 24 56 56 24 marker show with analyses marker older 206/238 Age #DIV/0! 1245 1039 1077 1067 1037 1035 1050 1033 1032 1022 1231 1043 1566 1097 1042 1315 957 962 930 889 371 923 918 904 921 950 965 961 948 880 860 917 942 953 948 957 989 981 988 811 641 1 Error #DIV/0! σ 53 53 51 49 67 21 51 51 50 51 52 53 42 40 39 39 36 38 39 39 39 39 41 44 33 33 33 33 32 32 32 40 33 48 43 31 31 33 63 51 24 207/206 Age 1045 1015 1024 1049 1312 1779 1029 1057 1040 1066 1571 1096 1080 1058 1196 1076 1062 1034 1050 1012 1011 1218 1489 1022 1008 1835 1023 1754 1098 1482 1044 4221 1247 1702 1659 997 994 994 990 992 991 991 1 Error σ 506 105 29 30 30 44 35 33 30 31 31 30 29 29 27 26 38 26 35 26 27 26 26 26 26 24 24 27 26 27 28 27 27 27 28 24 44 25 27 27 43 35 % Discordance #DIV/0! 16,1 81,2 10,9 13,9 13,8 14,2 42,0 12,4 27,9 21,3 14,4 19,9 29,8 36,8 11,8 36,3 50,8 65,2

8,8 5,4 9,4 5,5 3,8 9,5 5,2 9,4 9,6 6,5 5,5 8,4 4,9 1,7 4,8 5,0 4,5 3,7 2,3 0,4 5,5 5,7 3,4

14

DC1501 Red granite, Frölandskrossen The data from sample DC1501 consists of 26 cores. Figure 23 show 15 xenocryst and rim analyses from 14 different zircon grains. spots with Pb-Pb ages from about 1300 to Eleven of the analyses are discarded due to 1870 Ma. The data does not yield a reliable inhomogeneous data or high common lead. concordia age. However a Pb-Pb weighted The sample contains three age domains, seen average of five main domain analyses gives as CL bright cores, CL grey main domain and 1028 ±29 Ma with MSWD 0.19 and probability CL dark rims (see grain 55 in figure 16). Four of 0.94 (Black ellipses in figure 23). There are the analyzed spots in sample DC1501 are CL also two Pb-Pb rim ages of 1232 ±68 Ma and grey main domain zircons without oscillatory 1625 ±37 Ma (green ellipses in figure 23). growth zoning surrounding CL bright cores. Xenocryst cores from DC1501 (red ellipses in Grain 60 (figure 18) shows oscillatory growth figure 23) yield 1308 ±82 Ma, 1527 ±42 Ma, zoning and lacks a xenocryst CL bright core. 12 1683 ±44 Ma, 1759 ±50 Ma and 1872 ±50 Ma of the analyzed points are from xenocryst (table 3).

Figure 23 Sample DC1501. Concordia plot showing xenocryst cores as red ellipses, rim overgrowths as green ellipses and magmatic main domain zircons as black ellipses. The mean weighted Pb-Pb age is calculated from main domain zircons (black ellipses).

15

shows analyses used to obtain age determinations showsanalysesto used obtain age Table3 E D Batch DC1501

An

76 75 73c 73b 73a 70 60 56 55d 55c 55b 55a 53 52 50c 50b 50a 49 46c 46b 46a 45 42d 42c 42b 42a Spot from frölandskrossen. size, 5 with granite Red mm grain alyzed spots from sample DC1501. Red marker shows spots removedsample from sam marker Red DC1501. alyzed Core Main Rim Rim Core Core Main Core Main Core Main Main Core Core Core Rim Rim Core Main Main Core Core Rim Core Core Rim Analysis Inhomogenous PbC PbC PbC PbC Inhomogenous PbC PbC PbC Inhomogenous PbC Comments U 1028,3 2019,5 1271,5 277,8 846,2 482,0 188,0 288,4 286,1 126,4 289,8 574,1 157,2 266,5 509,0 197,1 345,8 388,6 298,0 229,5 440,1 68,6 69,9 26,4 77,4 0,9 Th 111,1 154,2 118,5 122,9 351,3 225,1 22,1 21,8 65,8 74,8 44,3 13,9 92,6 36,8 97,1 25,5 29,0 11,1 15,9 9,1 0,3 9,3 9,5 5,0 9,1 0,1 Th/U

0,03 0,03 0,05 0,06 1,09 0,63 0,07 0,39 0,05 0,01 0,03 0,03 0,77 0,03 0,01 0,06 0,33 0,58 0,16 0,06 0,60 0,36 0,03 1,18 0,98 0,04

ofUddevalla the G 208/232 Ratio -17,4268 #DIV/0! 0,1409 0,0819 1,8091 0,2141 0,0844 0,0780 0,0568 0,2229 0,1768 0,0706 0,0522 0,0651 0,1370 1,6162 0,1102 0,7134 0,1197 0,0555 0,0794 0,3207 0,0942 0,0868 0,0944 0,0836 1 Error #DIV/0! -6,1029 σ 0,0052 0,0068 0,0879 0,0179 0,0037 0,0036 0,0038 0,0188 0,0096 0,0039 0,0028 0,0027 0,0526 0,1094 0,0146 0,0442 0,0157 0,0040 0,0048 0,0295 0,0080 0,0048 0,0052 0,0071 207/235 Ratio -107,3583

13,7355 ranite. 3,1248 1,7234 7,5619 2,6707 3,8032 3,2585 1,6518 4,4755 1,4715 2,1300 1,5865 1,6444 2,3493 1,9426 2,2856 1,8048 5,2869 1,5303 3,5051 5,8603 3,2951 3,9490 4,2578 3,0748

1 Error

-63,4308 σ

0,0816 0,0489 0,2257 0,0751 0,1094 0,0920 0,0468 0,1294 0,0406 0,0907 0,0440 0,0519 0,0674 0,0671 0,0761 0,0603 0,4810 0,8134 0,0513 0,1183 0,3324 0,1090 0,1288 0,1373 0,1081 ples due to common lead or inhomogeneous analyses. Yellow marker shows Yellow plesolder lead due to inhomogeneous or marker common analyses. 206/238 Ratio -5,6754 0,1418 0,1682 0,2936 0,1606 0,2711 0,2490 0,1631 0,2531 0,1205 0,1878 0,1540 0,1627 0,2005 0,1731 0,1682 0,1609 0,3191 0,2290 0,1511 0,2444 0,1794 0,2385 0,2657 0,2698 0,2224 1 Error -1,5054 0,0050 0,0062 0,0106 0,0060 0,0100 0,0090 0,0059 0,0092 0,0043 0,0079 0,0056 0,0058 0,0073 0,0063 0,0061 0,0058 0,0120 0,0097 0,0055 0,0091 0,0066 0,0087 0,0096 0,0098 0,0086 σ rho -2,9507 0,8483 0,8409 0,7919 0,7610 0,8237 0,8037 0,8108 0,8253 0,8052 0,6310 0,8372 0,9367 0,8182 0,8604 0,9237 0,8814 0,8765 0,4680 0,9181 0,9155 0,5369 0,9261 0,9288 0,9266 0,9195 207/206 Ratio 0,1899 0,0741 0,1856 0,1209 0,1018 0,0950 0,0733 0,1276 0,0886 0,0832 0,0744 0,0732 0,0847 0,0814 0,0982 0,0814 0,3120 0,1633 0,0752 0,0732 0,1039 0,2392 0,1000 0,1076 0,1145 0,1001 1 Error 0,0036 0,0015 0,0041 0,0029 0,0021 0,0021 0,0016 0,0026 0,0019 0,0030 0,0015 0,0009 0,0018 0,0015 0,0014 0,0014 0,0057 0,0227 0,0872 0,0011 0,0016 0,0116 0,0014 0,0014 0,0016 0,0015 σ 208/232 Age #DIV/0! #NUM! 20866 19429 10878 2662 1589 3920 1637 1517 1116 4065 3289 1378 1028 1274 2594 2112 2285 1091 1544 5619 1820 1682 1822 1621 1 Error #DIV/0! #NUM! σ 128 642 300 313 165 958 863 268 529 286 457 148 133 93 68 67 72 73 54 52 76 90 90 97 207/235 Age #NUM! 1439 1017 2180 1320 1593 1471 1726 1159 1227 1096 1208 1047 2732 1867 1528 1955 1480 1624 1685 1426 990 919 965 987 943 1 Error #NUM! σ 141 20 18 27 21 23 22 18 24 17 30 17 20 21 23 24 22 34 21 27 50 26 27 27 27 206/238 Age #NUM! 1002 1660 1546 1433 1455 1110 1178 1029 1002 1785 1329 1409 1063 1379 1519 1540 1295 855 960 974 733 923 972 962 907 1 Error #NUM!

σ

zircon ages. White marker zirconWhite marker ages. 28 34 53 34 51 47 33 48 25 43 31 32 39 35 34 32 59 51 31 47 36 45 49 50 45 207/206 Age 2741 1044 2703 1969 1657 1527 1022 2065 1395 1273 1053 1019 1308 1231 1590 1232 3531 2490 1073 1020 1695 3115 1624 1759 1872 1626 1 Error 2329 σ 235 32 40 37 44 39 41 43 36 41 71 40 25 41 37 26 34 28 29 28 77 26 25 25 28 % Discordance 5799,5 77,5 43,3 55,2 32,6 50,1 14,9 12,9 10,5 17,8 39,7 23,7 56,2 50,2 11,6 18,7 71,4 16,6 15,2 19,9 22,3 4,0 7,5 6,9 4,9 4,8

16

TEN150001 Red granite, Kissleberg The data from sample TEN150001 consists of any concordant data (see figure 24) for 25 analyses from 10 different zircon grains. 16 plotting the age of the Uddevalla granite (See of the analyses are discarded due to table 1). Spot 39a (figure 4, 5 and table 1) is an inhomogeneous data or high common lead. analysis done on a CL bright main domain The sample contains three age domains which which yields a Pb-Pb age of 1055 ±122 Ma. are shown as Cl bright cores, Cl grey main The most concordant data from TEN150001 domain and CL dark rims (see figure 4), except are from CL bright xenocryst cores and CL dark for grain 39 (figure 8) which shows an rims that yield ages that range between 1200- oscillatory growth zoning in the core with CL 1300 Ma and 1500-1600 Ma (see figure 24 and bright main domain and a CL dark rim. The table 4). analyses from sample TEN150001 do not yield

Figure 24 Sample TEN150001. Concordia plot showing xenocryst cores as red ellipses, rim overgrowths as the green ellipse and magmatic main domain zircons as black ellipses. Grain 39a shows a main domain zircon with the age of 1055 ±122 Ma. The other ellipses give rim, main domain and xenocryst core ages above 1100 Ma.

17

ages. Table4 G F Batch TEN150001

Analyzed spots Analyzed sample shows from TEN150001. removedRed samples marker 39f 39e 39d 39c 39b 39a 38c 38b 38a 35c 35b 35a 28c 28b 28a 22 20b 20a 19 18b 18a 14 2c 2b 2a Spot from Kissleberg. size, 2-4granite Red mm grain Core Core Main Core Core Main Rim Core Main Core Rim Rim Core Rim Rim Core Core Rim Core Rim Core Core Rim Core Rim Analysis PbC PbC PbC Inhomogenous Inhomogenous Inhomogenous PbC PbC PbC PbC Inhomogenous Inhomogenous Inhomogenous Inhomogenous Inhomogenous Inhomogenous Comments U -2452,8 -7537,7 1331,3 1829,1 1401,7 1275,4 1245,0 3378,2 -131,8 200,7 102,2 344,1 304,5 907,1 844,6 173,4 285,7 611,6 194,5 109,3 317,6 50,5 56,3 64,1 0,0 Th -187,3 -343,8 -543,3 177,2 241,7 286,8 176,2 137,3 360,0 288,2 157,5 277,8 -72,8 63,7 56,3 63,2 88,0 77,9 88,3 65,6 3,9 0,3 9,5 6,1 0,0 Th/U -1,08 0,88 0,62 0,08 0,70 0,94 0,01 0,13 0,08 0,26 0,32 0,07 0,05 0,51 0,03 0,13 0,81 0,81 0,05 0,08 0,10 0,55 0,08 0,07 0,00 208/232 Ratio #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! -0,0060 0,0793 0,0941 0,0775 0,0799 0,2405 0,0407 0,0540 0,1095 0,1247 0,0915 0,0733 0,0782 0,1407 0,0787 0,2148 0,0335 0,0272 0,0491 1 Error #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! -0,0123 σ 0,0039 0,0054 0,0041 0,0042 0,0175 0,0031 0,0049 0,0066 0,0072 0,0048 0,0038 0,0041 0,0077 0,0042 0,0238 0,0086 0,0166 0,0027 207/235 Ratio -702,4437 -0,3712 2,5747 2,5552 1,7466 2,5201 2,4486 1,6084 3,9307 2,1159 3,7327 1,2401 0,7376 0,9168 2,8379 1,7930 3,4623 3,1202 3,2993 1,1349 0,7922 1,9128 0,4457 5,5238 0,3419 1 Error -308,8388 σ -0,9768

0,1068 0,1082 0,0766 0,1065 0,1027 0,0713 0,2975 0,0889 0,2837 0,0609 0,0370 0,0571 0,1253 0,0840 0,1626 0,1491 0,1576 0,0545 0,0374 0,1004 0,1412 4,1941 0,0227

duelead to analyses inhomogeneous or common 206/238 Ratio -0,0122 -6,9230 0,2182 0,2183 0,1596 0,2143 0,2097 0,1561 0,2415 0,1464 0,1340 0,1078 0,0708 0,0908 0,1608 0,1634 0,2504 0,2351 0,2386 0,0881 0,0616 0,1180 0,0571 0,4473 0,0462 1 Error -0,0884 -3,9275 0,0124 0,0124 0,0091 0,0123 0,0120 0,0089 0,0183 0,0084 0,0106 0,0065 0,0042 0,0060 0,0093 0,0104 0,0160 0,0151 0,0153 0,0057 0,0039 0,0077 0,0045 0,3375 0,0030 σ rho 0,9069 0,8930 0,8556 0,9138 0,9113 0,8497 0,9378 0,9024 0,9160 0,8945 0,8275 0,8760 0,7876 0,9874 0,9870 0,9810 0,9760 0,9837 0,9797 0,9007 1,5633 2,0908 0,9995 0,6610 0,0445 207/206 Ratio -0,1385 0,0854 0,0847 0,0794 0,0851 0,0843 0,0745 0,1158 0,1052 0,2037 0,0822 0,0747 0,0733 0,1316 0,0793 0,0999 0,0959 0,0999 0,0930 0,0929 0,1177 0,1036 0,0756 0,0866 0,0533 1 Error -0,0972 0,0022 0,0023 0,0024 0,0022 0,0022 0,0023 0,0031 0,0028 0,0065 0,0023 0,0025 0,0024 0,0047 0,0015 0,0019 0,0019 0,0020 0,0018 0,0019 0,0034 0,0047 0,0038 0,0021 0,0029 σ 208/232 Age #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! 1543 1817 1508 1552 4354 1063 2099 2374 1768 1430 1521 2660 1530 3931 -122 806 666 542 968 1 Error #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! #DIV/0! σ -248 100 286 121 130 137 400 170 329 74 78 79 59 93 88 72 77 78 52

207/235 Age . Yellow . #NUM! 1293 1288 1026 1278 1257 1620 1154 1578 1366 1043 1519 1438 1481 1086 1904 -471 973 819 561 661 770 592 374 299 1 Error

#NUM!

σ marker show with analyses marker older 1046 -952 104 31 31 29 31 31 28 63 29 63 28 22 31 34 31 38 37 38 26 21 36 17 206/238 Age #NUM! 1272 1273 1252 1227 1394 1441 1361 1379 2383 954 935 881 811 660 441 560 961 976 544 385 719 358 291 -79 1 Error #NUM! σ 1712 -552 66 66 51 66 64 50 96 48 61 38 25 36 52 58 83 79 80 34 24 45 27 18 207/206 Age #NUM! 1324 1308 1183 1317 1299 1055 1892 1717 2856 1251 1060 1023 2119 1180 1622 1546 1623 1489 1486 1922 1689 1084 1351 342 1 Error #NUM! σ 100 122 50 52 59 50 50 61 48 49 52 54 67 65 63 38 36 37 38 37 38 52 84 48

% Discordance

zircon #NUM! 108,7 20,9 11,9 27,8 52,2 76,2 49,0 59,9 47,3 59,8 18,3 12,1 12,9 16,4 65,9 76,1 66,1 76,6 98,4 14,6 4,0 2,8 5,2 5,6

18

Discussion The undeformed textures of the granite apart However the Pb-Pb age 1028 ±29 Ma from the from a vague foliation found in samples five spots interpreted to be main domain TEN150003 and TEN150004, suggests that the zircon (figure 18), supports the age estimate intrusion should not be older than the from sample TEN150004. In sample DC1501 Sveconorwegian peak metamorphism which two groups of rim ages from different grains according to Hegardt (2010) occurred at 1029 showed 1232 ±68 Ma and 1625 ±37 Ma and ±6 Ma. The xenocryst cores from all three are interpreted to be metamorphic rims from samples show a large variety of ages and one older source rocks. The xenocryst cores from can only speculate what the protolith might DC1501 give a wide range of Pb-Pb ages (See have been. In this case, ages from both rims table 1). Some can possibly be correlated to and cores that are older than the either the 1590 Stora Le Marstrand Sveconorwegian peak metamorphism are not Formation, the 1550 Hisingen Suite or considered to be relevant in dating the surrounding orthogneisses. Uddevalla Granite. TEN150001 TEN150004 From sample TEN150001 the two main Sample TEN150004 gives the most promising domain spots 39a (figure 8 and 9), which yield age estimate for the granite. A concordia age the Pb-Pb age 1055 ±122 Ma, probably reflect of 1027 ±8.7 Ma from six main domain spots the intrusive age. Other data show ages of that are <5% discordant is consistent with the xenocryst cores and older rims which did not Pb-Pb age of 1023 ±14 Ma from all 21 main originate from the Uddevalla Granite. The age domain spots. This indicates that it is not a of the rim analysis from this sample gives an post metamorphic intrusion like the 920 Ma age around 1180 Ma and the xenocryst cores Bohus Granite. The age supports field ranges from 1200-1600 Ma. Though the data relationships implying that the Uddevalla have mostly discordant ages, the older rim Granite is a syn-collisional granite intrusion. It and xenocryst cores could originate from could have been formed due to crustal surrounding bedrock. When dating the Bohus thickening during the Sveconorwegian peak Granite, Eliasson and Schöberg (1991) metamorphism. The Pb-Pb age 1061 ±49 from interpreted zircons with an age around 1700 rim analyses 162b and 157b (see table 1 and Ma to be inherited. This could also be the case 2) are within error of the same age and may for the older zircon ages dated from the reflect either late-magmatic or metamorphic Uddevalla Granite. Xenocryst cores dated to zircon growth. The three Pb-Pb core ages from be 1546 ±74 Ma and 1623 ±76 Ma are possibly xenocrysts (1196 ±52 Ma, 1312 ±70 Ma and inherited zircons from surrounding 1754 ±48 Ma) suggests that there are three orthogneisses. Sources could be the 1550 Ma different events that formed these zircons. Hisingen Suite, the 1620 Kallebäck Suite or the They likely originate from surrounding >1590 Ma Stora Le Marstrand orthogneisses. metasedimentary Formation. There is also a possibility that the xenocrysts are a relic from DC1501 previously overlying formations or gneisses Sample DC1501 contained a majority of relic deeper down under the granite intrusion. zircon ages thought to represent xenocrysts.

19

Age correlations Romer and Smeds (1996) dated pegmatites red and grey pegmatites would be of further from the Sveconorwegian terranes in interest, to test the idea that they are coeval southwestern Sweden. They suggested that with the finer granites. crustal thickening would have started in the west and later progressed further east. The Conclusion dating of Högsbo, Timmerhult, Skantorp and The Uddevalla Granite yields a U-Pb age of Skuleboda pegmatites are suggested to be a 1027 ±9 Ma and Pb-Pb ages of 1023 ±14 Ma result of the syn-collisional Sveconorwegian and 1028 ±29 Ma. The age of the intrusion is metamorphic event. The close proximity of likely to be within 1018-1036 Ma. This means the Uddevalla granite to the Skantorp (1041 that the Uddevalla Granite should be a syn- ±2 Ma) and Timmerhult (1039 ±4 Ma) collisional intrusion as a result of the pegmatites (see figure 3) means that the Sveconorwegian metamorphic event in the Uddevalla Granite could possibly correlate Idefjorden Terrane. with them and support the interpretation of Romer and Smeds (1996). However the Acknowledgements Uddevalla Granite is the first example of a large granite body of the type which Romer This work was made possible through the and Smeds envisaged to lie beneath the supervision of Professor David Cornell. I want to thank him for advising and seeing this pegmatites which they dated. As a support to the theory of a syn-collisional event, Fazic project through to the end. I also want to (2016) found that the granite yields thank Thomas Eliasson from Sveriges Geologiska Undersökning for acting as co- characteristics of an S-type granite which would mean that the intrusion formed by advisor and supplying samples and maps for melting of metasedimentary material. This this project. I am thankful for Eric Ackevall who provided the macro that was used to implies a magma origin by partial melting and transfer raw data into batches and Johan a recycling of older crustal material, which would explain the large number of zircon Hogmalm who supervised SEM work and the LA-ICP-MS session. Finally I want to thank xenocryst cores identified in the samples. Thomas Zack for being the examiner for this Further studies project. Further studies could aim to date the different colored granites. An attempt to date both the

20

References

Åhäll, K. I. (1989). Crustal growth and Fazic, A. (2016). Petrological and mineralogical evolution of the Proterozoic Östfold – description of the Sweconorwegian Uddevalla Marstrand belt, SW Sweden (Doctoral Thesis, Granite, southwestern Sweden (Bachelor’s Department of Geology, A61). Gothenburg: Essay). Gothenburg: Department of Earth Chalmers University of Technology and Sciences, Gothenburg University. University of Gothenburg.

Åhäll, K. I., Cornell, D.H., Armstrong, R. (1998). Hegardt, E. A. (2010). Pressure, temperature Ion probe zircon dating of metasedimentary and time constraints on tectonic models for units across the Skagerrak: new constraints Southwestern Sweden (Doctoral thesis, for early Mesoproterozoic growth of the Baltic Department of earth science, A134). Shield. Precambrian Research, 87, 117-134. Gothenburg: Gothenburg University.

Åhäll, K. I., Larson, Å. (2000). Growth-related 1.85-1.55 Ga magmatism in the Baltic Shield; a Ludwig, K.R. 1991. Isoplot: a plotting and review addressing the tectonic characteristics regression program for radiogenic isotope of Svecofennian, TIB 1 -related, and Gothian data. USGS Open file report, 91-445 events. GFF, 122, 193-206. Ludwig, K.R. 1998. On the treatment of Åhäll, K. I., Connelly, J. (2008). Long-term concordant uranium-lead ages. Geochimica et convergence along SW fennoscandia: 330 m.y. Cosmochimica Acta, 62, 665-676 of proterozoic crustal growth. Precambrian Research, 161, 452–474. Magnusson, N. H. (1960). Age determination of Swedish Precambrian rocks. Geologiska Andersen, T., Griffin, W.L., Jackson, S.E., Föreningen i Stockholm Förhandlingar, 82, Knudsen, T.L., Pearson, N.J. (2004). Mid- 407-432. Proterozoic magmatic arc evolution at the southwest margin of the Baltic shield. Lithos, Mell, S. (2005). A geochemical investigation of 73, 289-318. 1600 Ma and 1560 Ma Granitoids, Western Segment, SW Sweden (Master’s thesis). Bingen, B., Bikerland, A., Nordgulen, Ø., Gothenburg: Department of Earth Science, Sigmond, E.M.O. (2001). Correlation of Gothenburg University, 36pp. supracrustal sequneces and origen of terranes in the Sveconorwegian orogen of SW Romer, R. L., Smeds, S. A. (1996). U-Pb Scandinavia: SIMS data on zircon in clastic columbite ages of pegmatites from sediments. Precambrian Research, 108, 293- Sveconorwegian terranes in Southwestern 318. Sweden. Precambrian Research, 76, 15-30.

Bingen, B., Nordgulen, Ø., Viola, G. (2008). A Wu, Y. B., Zheng, Y. F. (2004). Genesis of zircon fourphase model for the Sveconorwegian and its constraints on interpretation of U–Pb orogeny, SW Scandinavia. Norwegian Journal age. Chinese Science Bulletin. Vol. 49, No. 15, of Geology, 88, 43-72. 1554 – 1569.

Eliasson, T., Schöberg, H. (1991). U-Pb dating of the post-kinematic Sveconorwegian (Grenvillian) Bohus granite, SW Sweden: evidence of restitic zircon. Precambrian Research, 51, 337-350.

21