Hf Isotopes in Zircon from Svecofennian Mag- Matic Rocks and Rapakivi Granites in Sweden

RESEARCH

Ancient and juvenile components in the continental crust and mantle: Hf isotopes in zircon from Svecofennian magmatic rocks and rapakivi granites in Sweden

U.B. Andersson1,4, G.C. Begg2,3, W.L. Grifﬁ n3, and K. Högdahl4 1LABORATORY FOR ISOTOPE GEOLOGY, SWEDISH MUSEUM OF NATURAL HISTORY, BOX 50007, SE-104 05 STOCKHOLM, SWEDEN 2MINERALS TARGETING INTERNATIONAL, 26/17 PROWSE STREET, WEST PERTH, WA 6005, AUSTRALIA 3GEMOC ARC NATIONAL KEY CENTRE, DEPARTMENT OF EARTH AND PLANETARY SCIENCES, MACQUARIE UNIVERSITY, SYDNEY, NSW 2109, AUSTRALIA 4DEPARTMENT OF EARTH SCIENCES, UPPSALA UNIVERSITY, VILLAVÄGEN 16, SE-752 36 UPPSALA, SWEDEN

ABSTRACT

The sources of igneous rocks in the continental crust are elusive, but they may be traced by radiogenic isotopes, which convey a message about the age and composition of the concealed parts of the continent. We investigated the Hf-isotope composition of zircon in ten rocks from central and southern Sweden. Two felsic metavolcanic rocks and two metagabbros (ca. 1.89 Ga) from Bergslagen, southern Sweden, ε − show Hf(t) ranges of 1.8 to +5.1 and +2.6 to +6.8, respectively, suggesting that juvenile sources have contributed to both. A 1.85 Ga granite ε − from southern Bergslagen shows a Hf(t) range of 2.6 to +4.6 for magmatic zircons, but both highly negative and positive values for inherited grains, providing evidence for both Archean and juvenile crustal sources. These and previous data confi rm the existence of juvenile proto-Svecofennian crust (<2.2–1.9 Ga) with a minor Archean component, from which later crustal magmas were generated. The Hf-isotope ε 176 177 evolution curve for this crust can be approximated by Hf(1.90) = 3 ± 3 and Lu/ Hf = 0.018. Similarly, the present data, together with data for ε younger mafi c intrusions, can be used to infer the presence of a “mildly depleted” sub-Svecofennian mantle evolution curve with Hf(1.90) 176 177 ε = 4.5 ± 2.5 and Lu/ Hf = 0.0315. Zircons from four out of fi ve rapakivi intrusions (1.53–1.50 Ga) in central Sweden yield negative Hf(t) in − − ε the range 9.8 to 4.6, suggesting mixed Archean and juvenile Svecofennian sources. One intrusion farther south ranges between Hf(t) of −4.1 and −1.6, and has a larger contribution from Svecofennian crust. The data suggest that the crust in Bergslagen, southern Sweden, is dominantly Paleoproterozoic, while higher proportions of Archean material are present below central Sweden.

LITHOSPHERE; v. 3; no. 6; p. 409–419. doi: 10.1130/L162.1

INTRODUCTION analytical precision), even approaching the Appelquist et al., 2011). Recent in situ zircon- end-member source compositions (e.g., Griffi n Hf data come mainly from the SW part of the The Hf-isotope ratios of individual zircon et al., 2002; Andersen et al., 2002, 2007; Yang shield, where 1.7–0.9 Ga granitoids yield initial ε crystals record heterogeneities in the magmas et al., 2007; Rutanen et al., 2011). In addition, Hf compositions ranging from depleted mantle of various igneous rock types at a much higher U-Pb and Lu-Hf spot analysis by laser ablation– to somewhat below chondritic uniform reservoir spatial resolution than do whole-rock isoto- inductively coupled plasma–mass spectrometry (CHUR) (Andersen and Griffi n, 2004; Ander- pic data (e.g., Griffi n et al., 2002; Kinny and (LA-ICP-MS) on cores and overgrowth zones sen et al., 2004, 2007; Pedersen et al., 2009), Maas, 2003; Belousova et al., 2006; Hawkes- in zircons from igneous rocks yields combined and even to highly negative values for some late worth and Kemp, 2006). Although whole-rock information on the spread in protolith and Sveconorwegian grains (Andersen et al., 2002, data yield information on the characteristics assimilant ages and the isotopic composition of 2009b). Only a few studies have reported such of the magma source(s) at the scale of whole- the magmas from which they crystallized (e.g., data from rocks of the Archean to Paleoprotero- rock samples within a given volume of a rock Belousova et al., 2006; Andersen et al., 2009a; zoic part of the shield (Andersen et al., 2009a; suite, this approach averages out any evidence Kurhila et al., 2010). This provides a powerful Heinonen et al., 2010; Kurhila et al., 2010; of mixed provenance within a single specimen. tool for unraveling the history of crustal tracts. Rutanen et al., 2011; Lauri et al., 2011). Source components of contrasting isotopic There exists a limited volume of whole-rock Here, we present new in situ zircon Hf- composition may be preserved in a magma on and multigrain-zircon Hf-isotope data from isotope data for 1.90–1.85 Ga mafi c and felsic a very local scale (e.g., the size of a hand speci- the Fennoscandian Shield, including various rocks from the Bergslagen region, southern men) within early-crystallized minerals that granitoid (Patchett et al., 1981; Vervoort and Sweden; these data add further constraints on are stable enough to have survived subsequent Patchett, 1996) and mafi c suites (Patchett et the origin of the continental crust in this part of stirring and mixing (e.g., Waight et al., 2000; al., 1981; Söderlund et al., 2005, 2006); these the Fennoscandian Shield. In addition, data are Charlier et al., 2007; Kemp et al., 2007; Qin data essentially replicate the information pro- reported for fi ve 1.53–1.50 Ga rapakivi intru- et al., 2010). Initial Hf-isotope data in zircons vided by the more abundant Nd-isotope data sions in central Sweden, yielding information separated from one sample may thus provide a (see compilations in, e.g., Lahtinen and Huhma, pertaining to the sources for this magmatism. wider spectrum of values than a suite of whole- 1997; Andersson et al., 2002, 2004; Rutanen The results are combined with previous isoto- rock samples (although with a somewhat lower and Andersson, 2009; Rutanen et al., 2011; pic data to build an integrated crustal model for

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the western and southern parts of the Svecofen- A nian Domain. s e STRÖMSUND d i n 1526±3 Ma GEOLOGICAL SETTING AND SAMPLES o d MULLNÄSET e 1520±3 Ma l a NORDSJÖ The classical Bergslagen mining region in CaledonidesC eastern southern Sweden (Stephens et al., 2009) consists of 1.91–1.87 Ga ore-bearing interca- lated metavolcanic and metasedimentary rocks. MÅRDSJÖ 1524±3 Ma The (mainly felsic) volcanic rocks dominate in the west and north, while the metasedimentary rocks are dominant in the SE part of the region 1505±12 Ma (e.g., Allen et al., 1996; Lundström et al., 1998) RAGUNDA (Fig. 1). The supracrustal rocks were intruded by an early Svecofennian granite-granodiorite- tonalite-gabbro suite at 1.89–1.86 Ga, and a 1514±5 Ma NORDINGRÅ 1578±17 Ma suite of late Svecofennian, migmatite-related granites and pegmatites at 1.85–1.75 Ga (sum- marized in, e.g., Andersson and Öhlander, 2004; Andersson et al., 2006a; Hermansson et al., 2008). In the south and west, the Svecofennian > 1.87 Ga metasedimentary rocks successions are truncated by 1.85–1.65 Ga gra- Early Svecofennian intrusive rocks Russia nitic-quartz monzonitic-monzodioritic-gabbroic 1.87-1.86 Ga diatexitic migmatite N intrusions of the Transscandinavian Igneous 1.87-1.85 Ga Kfs-megacryst-bearing granite RÖDÖN 1497±6 Ma Belt (e.g., Högdahl et al., 2004). The Transscan- 1.87-1.80 Ga leucogranite dinavian Igneous Belt is commonly subdivided 1.80 Ga Revsund granitoid suite BB into intrusive episodes, of which the earliest 63°N 1.75 Ga Grötingen granite FFinlandinland Norway (ca. 1.85–1.83 Ga) occurred mainly along the 1.58-1.50 Ga rapakivi granite/syenite Major plastic shear zones LjD SW Svecofennian border zone (e.g., Persson Kinematic indicators 1.58-1.50 Ga mafic plutonic rocks BS and Wikström, 1993; Andersson and Wikström, Phanerozoic rocks 1.26 Ga dolerite 0 10 20 30 km Caledonides Southwest 2001; Wikström and Andersson, 2004). The sec- SSwedenweden Scandinavian Domain Rapakivi granite ond, and dominant, episode (1.81–1.75 Ga) fol- TIB lowed mainly farther away from the Svecofen- > 1.87 Ga meta- Revsund suite sedimentary rocks 15°E Svecofennian Domain nian margin (e.g., Mansfeld, 1991; Andersson 1.91-1.86 Ga meta- HighHigh mmetamorphicetamorphic Covered Archean volcanic rocks basement and Wikström, 2004), while the third episode Early Svecofennian gradegrade StrömsbroStrömsbro Archaean basement intrusive rocks (1.71–1.65 Ga) was emplaced even farther to Late Svecofennian GGÄVLEÄVLE intrusive rocks Kfs+SilKfs+Sil 1.85-1.75 Ga Transscandinavian the west and north (e.g., Ahl et al., 1999; Lun- Transscandinavian MMs+Qtzs+Qtzs+Qtz Igneous Belt (TIB) dqvist and Persson, 1999; Söderlund et al., Jotnian sandstone Cambro-Silurian 1999; Brander et al., 2011). sedimentary rocks Approximate outline of Greenschist facies UBUB 998:298:29 arc Five samples from Bergslagen were studied: matic Approximate position of Mag two maﬁ c intrusions, two felsic volcanic rocks, isograd for the reaction c grade ms + qtz Kfs + sil orphi U97:3U97:3 and one sample of the earliest Transscandina- etam Major plastic shear zones m m diu U97:1U97:1 vian Igneous Belt generation. The petrography Kinematic indicators Me and secondary ion mass spectrometry (SIMS) Sample localitiy Uppland Batholith geochronology of these samples are described LowLow mmetamorphicetamorphic UPPSALA gradegrade in Andersson et al. (2006a). All samples have been metamorphosed in middle to upper R 889:149:14 amphibolite facies. The two maﬁ c intrusive Kfs+SilKfs+Sil rocks (R89-14: 1887 ± 5 and UB98-29: 1895 Ms+QtzMs+Qtz

MälarenMälaren STOCKHOLMSTOCKHOLM HjälmarenHjälmaren radMälarenMeälaren phic g Figure 1. Geological overview of central Swe- mor eta den (A) and the Bergslagen region (B), with h m Hig asin sample locations indicated. Upper frame in nd B mla inset map outlines position of A, and lower Sör frame outlines position of B. BB—Bothnian ic FINSPÅNGFINSPÅNG h NYKÖPINGNYKÖPING rp Basin, LjD—Ljusdal domain, BS—Bergslagen FFin2in2 o N il m S z a region, TIB—Transscandinavian Igneous Belt. + t tt VätternVättern s Q e f + Figure is modiﬁ ed from Andersson (1997a), Kfs+SilK s m Ms+QM m grade Andersson et al. (2006a), Högdahl et al. (2008), iu 0 25 50 km B ed and references therein. M

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± 5 Ma) were sampled from western Bergsla- gen, the two felsic volcanic rocks (U97-1: 1888 ± 12 and U97-3: 1892 ± 7 Ma) were sampled from the eastern part, and the early Transscan- dinavian Igneous Belt augen gneiss (Fin2: 1855 ± 6 Ma) came from the southern part (Fig. 1). North of the Bergslagen region, there is a vast and relatively little-studied area (referred to as the Ljusdal domain; Högdahl et al., 2009) of mostly migmatitic supracrustal rocks, and a suite of variably deformed 1.86–1.84 Ga plutonic rocks of the Ljusdal Batholith (e.g., Sjöström and Bergman, 1998; Högdahl et al., 2008). North of the Ljusdal domain, there lies the Bothnian Basin, an area strongly dominated by thick successions of metasedimentary rocks (Lundqvist, 1987), which are intruded by at least two generations of granitoid rocks, including pegmatites, at ca. 1.95–1.86 and 1.82–1.79 Ga (e.g., Claesson and Lundqvist, 1995; Romer and Smeds, 1997; Lundqvist et al., 1998; Rut- land et al., 2001; Weihed et al., 2002; Högdahl et al., 2008; Skiöld and Rutland, 2006). To the west and SW, the Bothnian Basin is intruded by ca. 1.87–1.85 Ga K-feldspar-megacryst–bearing granites and diatexites (Högdahl and Ahl, 2004; Högdahl et al., 2008) and, farther north, by the mainly 1.81–1.77 Ga Revsund granitoid suite (Claesson and Lundqvist, 1995; Weihed et al., 2002), which constitutes the northern continu- ation of the Transscandinavian Igneous Belt (e.g., Andersson, 1997b; Gorbatschev, 2004). Composite rapakivi intrusions, including granites, syenites, gabbros, anorthosites, and numer- ous diverse dikes, intruded the southern part of the Bothnian Basin and the Revsund suite at 1.53–1.50 Ga (Andersson, 1997c; Andersson et al., 2002). One rapakivi intrusion was emplaced at Strömsbro farther south, right at the border between the Bergslagen region and the Ljusdal domain (Andersson, 1997a; Fig. 1B). Descriptions and U-Pb zircon thermal ion- ization mass spectrometry (TIMS) age determinations of the fi ve rapakivi intrusions can be found in Andersson (1997a, 1997b, 2001) and Andersson et al. (2002). These are from south Figure 2. Cathodoluminescence images of analyzed zircons. The 207Pb/206Pb spot ages (Andersson to north (Fig. 1): the Strömsbro granite (1500 et al., 2006a) are given, and the initial ε data are from Table 1. ± 20 Ma), the Rödön granite (1497 ± 6 Ma), Hf the Mårdsjö granite (1524 ± 3 Ma), the Nordsjö syenite (1520 ± 3 Ma), and the Mullnäset gran- of zircon growth was known for each of these lution and Metallogeny of Continents of ite (1526 ± 3 Ma). spots. Crystallization ages for the fi ve rapakivi the Australian Research Council (GEMOC intrusions were previously determined only by ARC), Macquarie University, Australia. The ANALYTICAL METHODS zircon U-Pb TIMS geochronology (Anders- 176Hf/177Hf ratios in zircon were measured son, 1997c; Andersson et al., 2002). The great with a New Wave Research 213 nm laser- The fi ve zircon samples from the Bergsla- majority of crystals from these intrusions show ablation microprobe attached to a Nu Plasma gen area were previously analyzed for U-Th-Pb uncomplicated magmatic growth zoning, and multicollector ICP-MS. The analytical meth- using the SIMS technique (Andersson et al., such crystals were selected both for the previous ods, including extensive data on the analysis 2006a). Our Lu-Hf analyses were obtained in TIMS analysis and for the present Lu-Hf study. of standard solutions and zircons, were dis- the same analytical spots as were used for the Hf-isotope analyses were performed at cussed in detail by Griffi n et al. (2000, 2002). previous U-Pb analyses (Fig. 2). Thus, the age National Key Centre for Geochemical Evo- Data were processed using the Nu Plasma

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time-resolved analysis software, which allows RESULTS from the early Svecofennian felsic volcanic selection of the most stable part of the abla- rocks fall in the range −1.8 to +5.1. The ini- ε tion signal. Analyses were carried out at 5 The results of all analyses are given in tial Hf results from the rapakivi zircons range μ ε − − Hz frequency with a beam diameter 55 m Table 1 and plotted in Hf versus time diagrams between 9.8 and 1.6 and differ signifi cantly and energies around 0.1 mJ per pulse. Back- in Figure 3. Even though the 207Pb/206Pb age was among the intrusions. The zircons from the ground was measured for 60 s prior to abla- known for each individual spot for the Bergsla- Strömsbro granite in the south show distinctly ε ε − tion. The length of the analysis varied between gen zircons, the initial Hf value for each analy- less-negative initial Hf values between 4.0 and 30 and 140 s, depending on the thickness of sis from the magmatic parts of crystals is plotted −1.6 and do not overlap with those from the the grains. Repeated analyses of the Mud Tank at the calculated crystallization age of the rock. northern samples (−9.8 to −4.6), in accordance zircon (long-term running average 176Hf/177Hf This is because of the relatively large error in with the whole-rock Nd-isotope data from these = 0.282523 ± 43; Griffi n et al., 2007) and the individual SIMS analyses, variable degrees complexes (Andersson et al., 2002). The north- the 91500 zircon (long-term running average of discordance, and possible nonzero lower ern samples show overlapping initial ratios, but 176Hf/177Hf = 0.282307 ± 58; Griffi n et al., intercepts. However, inherited cores and over- with a tendency for higher values in Nordsjö and 2006) were used to monitor data quality, trans- growths are plotted at their individual 207Pb/206Pb lower ones in Mullnäset. The range within each ε ε ε lating to about ±2 units. ages. The initial Hf values of the rapakivi zir- rapakivi intrusion does not exceed 3.5 units. For the decay constant of 176Lu, a value of cons are plotted at the calculated TIMS age of Including the previous analyses from the 1.867 × 10−11 yr−1 (Scherer et al., 2001, 2007) crystallization. The homogeneous zoning of the 1.85 Ga Finspång augen gneiss (Andersen et ε was applied. The present-day chondritic values zircons and the coherency of the Hf isotopic al., 2009a), magmatic crystals yielded initial Hf used were 176Lu/177Hf = 0.0336 and 176Hf/177Hf = results support a magmatic origin for the ana- values between −2.6 and +4.6, while analyses 0.282785 (Bouvier et al., 2008). For the depleted lyzed crystals. In reference to the data and dis- of inherited cores show a considerable range in ε mantle reference curve, the straight-line model cussion, one should bear in mind the analytical ages and initial Hf (Fig. 3). Analytical spots giv- of Griffi n et al. (2000) was adopted, updated precision of ≤2 ε units, which, however, will not ing apparent 207Pb/206Pb ages between 1.91 and ε − by the more recent values for CHUR and the alter the interpretations and conclusions. 2.24 Ga range in Hf from 16.1 to +9.8, i.e., 176 ε decay constant of Lu, which yields a present- The initial Hf values from the early Sveco- from the Archean crust to depleted mantle (DM). 176 177 ε day value of Hf/ Hf = 0.28325 ( Hf = +16.4), fennian mafi c intrusive rocks range from +2.6 However, seven out of ten fall in the narrow similar to mid-ocean-ridge basalt (MORB), and to +6.8, including a few slightly older cores and range +0.6 to +3.6. Those with apparent ages in 176 177 ε a Lu/ HfDM value of 0.0388. slightly younger overgrowths, while the data the range 2.35 to 2.95 Ga yielded Hf in the range

TABLE 1. Lu-Hf DATA ON ZIRCONS FROM SVECOFENNIAN AND RAPAKIVI ROCKS IN SWEDEN

176 177 176 177 176 177 176 177 ε † Sample no. Age Hf/ Hf 2se Lu/ Hf Yb/ Hf Hf/ Hf Hf 2se T(DM)* T(DM) crustal Coordinates, RT90 2.5 gon V (Ma) initial initial (Ga) (Ga)

Svecofennian rocks Amphibolitic gabbro (663060/144590) R8914.n746-02a 1920 0.281772 0.000022 0.001658 0.049513 0.281711 5.4 0.8 2.09 2.23 R8914.n746-03a 1910 0.281820 0.000048 0.002675 0.087205 0.281723 5.6 1.7 2.08 2.21 R8914.n746-04a 1887 0.281861 0.000036 0.003130 0.094545 0.281749 6.0 1.3 2.05 2.17 R8914.n746-05a 1887 0.281878 0.000032 0.002943 0.089731 0.281772 6.8 1.1 2.01 2.11 R8914.n746-06a 1887 0.281776 0.000032 0.002857 0.084956 0.281674 3.3 1.1 2.15 2.36 R8914.n746-07a 1887 0.281811 0.000042 0.002085 0.064981 0.281736 5.5 1.5 2.06 2.20 R8914.n746-08a 1887 0.281746 0.000030 0.002410 0.067628 0.281660 2.8 1.1 2.17 2.40 R8914.n746-09a 1887 0.281763 0.000054 0.001614 0.043031 0.281705 4.4 1.9 2.10 2.28 Amphibolitic gabbro (668110/149230) UB9829.n743-01a 1895 0.281811 0.000028 0.002036 0.054184 0.281738 5.8 1.0 2.06 2.19 UB9829.n743-02a 1895 0.281715 0.000024 0.000382 0.009193 0.281701 4.5 0.8 2.10 2.28 UB9829.n743-04a 1944 0.281711 0.000040 0.001402 0.041414 0.281659 4.1 1.4 2.16 2.35 UB9829.n743-05a 1895 0.281834 0.000038 0.003245 0.091660 0.281717 5.0 1.3 2.09 2.24 UB9829.n743-06a 1895 0.281873 0.000030 0.004394 0.123039 0.281715 5.0 1.1 2.10 2.25 UB9829.n743-07b 1870 0.281744 0.000026 0.001121 0.029425 0.281704 4.0 0.9 2.10 2.30 UB9829.n743-08a 1895 0.281658 0.000032 0.000234 0.006407 0.281650 2.6 1.1 2.17 2.42 UB9829.n743-09a 1895 0.281719 0.000030 0.000251 0.006604 0.281710 4.8 1.1 2.09 2.26 Felsic metavolcanic rock (666635/161850) U971.n744-01a 1888 0.281744 0.000036 0.001529 0.042854 0.281689 3.9 1.3 2.12 2.32 U971.n744-04a 1888 0.281650 0.000030 0.001098 0.030511 0.281611 1.1 1.1 2.23 2.52 U971.n744-05a 1888 0.281752 0.000030 0.002129 0.060470 0.281676 3.4 1.1 2.14 2.36 U971.n744-06a 1888 0.281796 0.000040 0.002107 0.066129 0.281720 5.0 1.4 2.08 2.24 U971.n744-07a 1888 0.281765 0.000028 0.001714 0.048575 0.281704 4.4 1.0 2.10 2.28 U971.n744-08a 1888 0.281756 0.000028 0.001515 0.043266 0.281702 4.3 1.0 2.10 2.29 U971.n744-09a 1888 0.281802 0.000024 0.002390 0.075790 0.281716 4.9 0.8 2.09 2.25 U971.n744-11a 1888 0.281796 0.000024 0.002016 0.060486 0.281724 5.1 0.8 2.08 2.23 U971.n744-12a 1888 0.281766 0.000022 0.001969 0.064395 0.281695 4.1 0.8 2.12 2.31 U971.n744-16a 1888 0.281711 0.000040 0.001476 0.042279 0.281658 2.8 1.4 2.16 2.40 (continued )

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TABLE 1. Lu-Hf DATA ON ZIRCONS FROM SVECOFENNIAN AND RAPAKIVI ROCKS IN SWEDEN (continued )

176 177 176 177 176 177 176 177 ε † Sample no. Age Hf/ Hf 2se Lu/ Hf Yb/ Hf Hf/ Hf Hf 2se T(DM)* T(DM) crustal Coordinates, RT90 2.5 gon V (Ma) initial initial (Ga) (Ga)

Svecofennian rocks Felsic supracrustal rock (668180/163190) U973.n748-01a 1892 0.281762 0.000032 0.002013 0.059823 0.281690 4.0 1.1 2.12 2.32 U973.n748-02a 1892 0.281696 0.000030 0.001376 0.037623 0.281647 2.5 1.1 2.18 2.43 U973.n748-03a 1892 0.281608 0.000030 0.002246 0.070395 0.281527 –1.8 1.1 2.35 2.73 U973.n748-04a 1892 0.281746 0.000028 0.001304 0.036757 0.281699 4.3 1.0 2.11 2.29 U973.n748-05a 1892 0.281629 0.000024 0.000897 0.024384 0.281597 0.7 0.8 2.24 2.55 U973.n748-06a 1892 0.281696 0.000022 0.001681 0.046906 0.281636 2.1 0.8 2.20 2.45 U973.n748-07a 1892 0.281642 0.000022 0.001050 0.028307 0.281604 1.0 0.8 2.23 2.53 U973.n748-08a 1892 0.281682 0.000028 0.001685 0.050814 0.281621 1.6 1.0 2.22 2.49 Finspång augen gneiss (650975/149720) Fin2.n747-01a 1855 0.281665 0.000034 0.000925 0.033777 0.281632 1.1 1.2 2.20 2.50 Fin2.n747-02a 1855 0.281667 0.000024 0.000449 0.014316 0.281651 1.8 0.8 2.17 2.45 Fin2.n747-03a 1855 0.281801 0.000034 0.002020 0.067225 0.281730 4.6 1.2 2.07 2.25 Fin2.n747-04a 1855 0.281757 0.000022 0.001816 0.055941 0.281693 3.3 0.8 2.12 2.34 Fin2.n747-05a 2447 0.281098 0.000034 0.000402 0.012339 0.281079 –4.8 1.2 2.92 3.36 Fin2.n747-06a 1855 0.281664 0.000030 0.000330 0.010295 0.281652 1.8 1.1 2.16 2.44 Fin2.n747-10a 1855 0.281719 0.000026 0.001097 0.033543 0.281680 2.8 0.9 2.13 2.37 Fin2.n920-10b 2474 0.280803 0.000022 0.000381 0.010876 0.280785 –14.6 0.8 3.31 4.07 Fin2.n747-11a 2032 0.281563 0.000028 0.000660 0.019340 0.281537 1.8 1.0 2.32 2.58 Fin2.n747-12a 1967 0.281655 0.000024 0.000694 0.020725 0.281629 3.6 0.8 2.20 2.40 Rapakivi complexes Strömsbro granite (673225/157457) Sbro7-01 1500 0.281745 0.000016 0.000616 0.021097 0.281728 –3.7 0.6 2.07 2.57 Sbro7-02 1500 0.281794 0.000015 0.001101 0.038836 0.281763 –2.4 0.5 2.03 2.48 Sbro7-03 1500 0.281831 0.000015 0.002041 0.078796 0.281773 –2.0 0.5 2.03 2.46 Sbro7-04 1500 0.281762 0.000013 0.000781 0.025651 0.281740 –3.2 0.5 2.06 2.54 Sbro7-05 1500 0.281857 0.000030 0.002534 0.107815 0.281785 –1.6 1.1 2.02 2.43 Sbro7-06 1500 0.281767 0.000014 0.000612 0.019307 0.281750 –2.9 0.5 2.04 2.52 Sbro7-07 1500 0.281750 0.000016 0.001187 0.040643 0.281716 –4.1 0.6 2.09 2.60 Rödö granite (692031/159275) Rodo-01 1497 0.281639 0.000015 0.000333 0.012451 0.281630 –7.2 0.5 2.20 2.82 Rodo-02 1497 0.281684 0.000018 0.001597 0.063722 0.281639 –6.9 0.6 2.21 2.80 Rodo-03 1497 0.281678 0.000015 0.001331 0.055973 0.281640 –6.8 0.5 2.20 2.79 Rodo-04 1497 0.281626 0.000013 0.000429 0.014658 0.281614 –7.8 0.5 2.22 2.86 Rodo-05 1497 0.281648 0.000014 0.000796 0.028869 0.281625 –7.4 0.5 2.21 2.83 Rodo-06 1497 0.281640 0.000020 0.001050 0.046314 0.281610 –7.9 0.7 2.24 2.87 Rodo-07 1497 0.281620 0.000016 0.000708 0.028593 0.281600 –8.3 0.6 2.24 2.90 Nordsjö syenite (706214/151693) N12-01 1520 0.281715 0.000028 0.001483 0.054240 0.281672 –5.2 1.0 2.16 2.69 N12-02 1520 0.281716 0.000022 0.000994 0.037644 0.281687 –4.6 0.8 2.13 2.66 N12-03 1520 0.281682 0.000026 0.000944 0.034549 0.281655 –5.8 0.9 2.17 2.74 N12-04 1520 0.281602 0.000015 0.000387 0.013174 0.281591 –8.1 0.5 2.25 2.90 N12-05 1520 0.281665 0.000019 0.000490 0.016220 0.281651 –5.9 0.7 2.17 2.75 N12-06 1520 0.281637 0.000020 0.000739 0.025589 0.281616 –7.2 0.7 2.22 2.84 N12-07 1520 0.281692 0.000016 0.001067 0.037335 0.281661 –5.6 0.5 2.17 2.72 Mårdsjö granite (702589/149466) M14a-01 1524 0.281632 0.000017 0.000303 0.010074 0.281623 –6.8 0.6 2.21 2.81 M14a-02 1524 0.281634 0.000022 0.000594 0.020865 0.281617 –7.0 0.8 2.22 2.83 M14a-03 1524 0.281596 0.000013 0.000394 0.012993 0.281585 –8.2 0.4 2.26 2.91 M14a-04 1524 0.281642 0.000019 0.000736 0.024928 0.281621 –6.9 0.7 2.22 2.82 M14a-05 1524 0.281630 0.000020 0.000743 0.023603 0.281609 –7.3 0.7 2.23 2.85 M14a-06 1524 0.281665 0.000019 0.000825 0.025795 0.281641 –6.2 0.7 2.19 2.77 M14a-07 1524 0.281638 0.000016 0.000792 0.025741 0.281615 –7.1 0.6 2.22 2.83 Mullnäset granite (707200/149208) Mu7-01 1526 0.281618 0.000020 0.001132 0.045500 0.281585 –8.1 0.7 2.27 2.91 Mu7-02 1526 0.281575 0.000014 0.001338 0.053424 0.281536 –9.9 0.5 2.34 3.03 Mu7-03 1526 0.281565 0.000017 0.000333 0.012464 0.281555 –9.2 0.6 2.30 2.98 Mu7-04 1526 0.281589 0.000024 0.000619 0.021182 0.281571 –8.6 0.8 2.28 2.94 Mu7-05 1526 0.281609 0.000017 0.001392 0.052236 0.281569 –8.7 0.6 2.30 2.95 Mu7-06 1526 0.281562 0.000016 0.000478 0.016345 0.281548 –9.4 0.6 2.31 3.00 Mu7-07 1526 0.281614 0.000017 0.000606 0.022267 0.281596 –7.7 0.6 2.25 2.88 *Minimum depleted mantle (DM) age, calculated using the measured 176Lu/177Hf of the zircon. †Depleted mantle age, calculated using a bulk crust 176Lu/177Hf value of 0.018.

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Fin2

R89:14

A 10 U97:1

Mafic rocks DM U97:3 5 SJPC UB98:29 M14a

0 CHUR Mu7 ε Figure 3. (A–C) Hf versus time diagram for N12 B) the present samples and other relevant Rödö –5 data. Chondritic uniform reservoir (CHUR) Early Svecofennian granites Sbro is after Bouvier et al. (2008). Depleted Epsilon Hf Late Svecofennian granites mantle (DM) is after Griffi n et al. (2000), Fin2 (Andersen et al., 2009a) –100 C) modifi ed by the CHUR data of Bouvier et Rap. granitoids SE Finl. al. (2008). Upper limit of Fennoscandian Rap. granitoids SW Finl. Archean crust is as defi ned by Andersen –15 Rap.-ass. mafic rocks SE Finl. et al. (2009a). Green ellipse in A encom-

Rap.-ass. mafic rocks SW Finl. passes the zircon data for early Sveco- –20 fennian mafi c rocks of this study and Rap. granitoids 900 1100 1300 1500 1700 1900 2100 2300 2500 2700 2900 (Patchett et al., 1981) includes the data of Patchett et al. (1981). Age (Ma) The ellipse for early Svecofennian gran- 10 ites includes data from Bergslagen and B DM south-central Finland (Andersen et al., 2009a; Heinonen et al., 2010). The ellipse 8 for late Svecofennian granites includes data from Vervoort and Patchett (1996), Andersen et al. (2009a), and Kurhila et al. 6 (2010). Violet diamonds—Transscandina- vian Igneous Belt (TIB) granitoids (Ander- sen et al., 2009a). Various red and green 4 squares—Finnish rapakivi granites and their associated mafi c rocks, respectively (Patchett et al., 1981; Heinonen et al., 2 2010). Crosses—various suites of younger mafi c intrusions in the central part of the Epsilon Hf Fennoscandian Shield (Söderlund et al., 0 CHUR 2005). The latter data are broadly encompassed by the evolutionary fi eld for the Early Svecofennian granites Paleoproterozoic Fennoscandian “mildly –2 depleted” subcontinental mantle (MDM), Late Svecofennian granites ε approximated by: Hf(1.90) = 4.5 ± 2.5 and 176Lu/177Hf = 0.0315. SJPC—Sveco- –4 fennian juvenile protocrust, represent- 1750 1800 1850 1900 1950 2000 2050 ing new crust formed after 2.2 Ga in the Age (Ma) Svecofennian Domain, partly by mixing 1 with Archean material (indicated by large C arrows). Post–2.0 Ga felsic crust in the CHUR southern Svecofennian province is largely SW Finland rapakivi formed from this juvenile crust and lies –1 within an evolutionary fi eld defi ned by: ε 176 177 SE Finland rapakivi Hf(1.90) = 3 ± 3 and Lu/ Hf = 0.018, Strömsbro including Transscandinavian Igneous Belt –3 granitoids and Finnish rapakivi granites. Frames in A outline areas enlarged in B and C. Blue arrow in B indicates minor Archean contributions to Svecofennian –5 granitoids plotting below the juvenile Nordsjö crust, supplied mainly through melting

Epsilon Hf of metasediments. Arrows in C indicate Mårdsjö –7 Svecofennian and Archean contributions Rödön to the rapakivi granitoids from various local mixtures of meta-igneous sources.

–9 Mullnäset

–11 1460 1500 1540 1580 1620 1660

Age (Ma)

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−14.6 to +2.7, where all but one fall within the higher proportions of older material compared early Paleoproterozoic inherited grains with both evolution of the Fennoscandian Archean crust. with the meta-igneous rocks (see summary DM and Archean initial Hf isotopic compositions The true ages of the analyses older than 2.2 Ga in Andersson et al., 2002). The total range of suggests that the earliest Svecofennian protocrust are poorly constrained, particularly those from values is ~7 ε units of the ~16 ε units between formed from a mixture of these components after Andersen et al. (2009a), because of discordance DM and the upper limit of the evolution for the 2.2 Ga (Fig. 3). This protocrust probably was and large analytical errors. However, the pres- Fennoscandian Archean crust, and they all fall created in early arc systems of variable maturity ence of zircon that crystallized in early Paleo- entirely on the depleted (high-ε) side of CHUR. from a depleted to increasingly enriched mantle, proterozoic and Archean time is clear. The present data corroborate previous mixed with subordinate amounts of components juvenile bulk-rock Hf-isotope data from Sve- derived from the Archean craton (cf. Patchett and DISCUSSION cofennian granites in Bergslagen and southern Bridgwater, 1984; Patchett et al., 1987; Anders- Finland (Patchett et al., 1981; Vervoort and son, 1991). The development of this protocrust Svecofennian Juvenile Crust Patchett, 1996) and zircon Hf-isotope data from involved the creation and accretion of several Svecofennian and Transscandinavian Igneous arc systems, as well as reworking of early arcs Following rifting of the Archean craton Belt granites in Sweden (Andersen et al., 2009a; into mature arcs (microcontinents), and colli- margin in the NE, new crust started to form Fig. 3). This restricted range of positive initial sions with the pre-accreted continent over such in several arc systems in successive stages ratios does not lend support to a model of mixing extended time (see, e.g., Nironen, 1997; Lahtinen outboard of the craton from ca. 2.1 Ga (Gaál between Archean and DM sources, which would et al., 2005, 2009a, 2009b). and Gorbatschev, 1987; Lahtinen and Huhma, tend to generate a larger spread in initial ratios, During the proto-Svecofennian (ca. 2.1– 1997; Nironen, 1997), creating early “micro- but rather suggests a dominance of sources sep- 1.91 Ga; Andersson et al., 2006a), and the follow- continents” in the period 2.1–1.93 Ga (Lahtinen arated from the mantle in early Paleoproterozoic ing early Svecofennian (1.91–1.86 Ga) period of et al., 2005, 2009a); little of this older crust is time (cf. Andersen et al., 2009a). Similarly, Hf major juvenile crust formation (a major world- exposed at the present erosion level. This proto- data for zircons from Svecofennian granitoids wide crustal growth episode; e.g., Condie, 2000), Svecofennian crust was strongly reworked from in southern Finland tend to be relatively juve- Fennoscandia became included in an assembled 1.91 to 1.86 Ga, when most of the presently nile in the west but carry higher proportions of Paleoproterozoic supercontinent (e.g., Rogers exposed rocks in the domain were formed. Archean signatures toward the craton margin in and Santosh, 2002; Zhao et al., 2004, 2006). The preexistence of the proto-Svecofennian the east (Kurhila et al., 2010; Heinonen et al., The 1.85–1.65 Ga Transscandinavian Igneous crust is substantiated by a few outcropping 2010; Rutanen et al., 2011). Belt formed part of a long-lived active continen- 1.95–1.91 Ga igneous rocks, and especially by Inherited cores of zircons from the Trans- tal margin along one side of the supercontinent, the dominance of juvenile (<2.1 Ga) depleted- scandinavian Igneous Belt augen gneiss span stretching from SW Baltica all through southern ε mantle Nd model ages in the 1.91–1.86 Ga fel- large ranges in both age and initial Hf (Fig. 3). Laurentia (e.g., Gower et al., 1990; Karlstrom et sic rocks, as well as in the felsic Transscandi- However, most of those in the age range 2.1 to al., 2001; Johansson, 2009). ε navian Igneous Belt rocks (e.g., Patchett et al., 1.9 Ga have initial Hf values on the juvenile side The Hf-isotopic evolution of the Svecofen- 1987; Valbracht et al., 1994; Andersson, 1997b; (+0.6 to +3.6). Only one originally crystallized at nian protocrust can be broadly constrained ε 176 177 ≈ Lahtinen and Huhma, 1997). Even stronger ca. 1.97 Ga from a magma derived from Archean to Hf(1.89) = +3 ± 3 and Lu/ Hf 0.018, ε − 207 206 evidence comes from the zircon record. Large crust ( Hf = 16.1). The fi ve cores with Pb/ Pb based on the presently available Svecofennian ε numbers of Svecofennian metasedimentary ages in the range 2.39 to 2.95 Ga show initial Hf data, and data from Transscandinavian Igneous rocks carry detrital zircons (60%–70%) in the in the range −2.4 to −14.6, and these values are Belt granitoids that are considered to be derived age range 2.1 to 1.86 Ga; the remainder mostly typical for Fennoscandian Archean crust. Even if from the Svecofennian crust (Fig. 3). This are Archean, and a very few grains fall in the age the exact ages of these grains are uncertain, due 176Lu/177Hf ratio is higher than that of estimates range 2.45 to 2.1 Ga (e.g., Claesson et al., 1993; to discordance, they most certainly contain domi- for the average continental crust (0.010–0.015), Lahtinen et al., 2002, 2009b, 2010; Sultan et al., nantly Archean Hf. Similarly, the ages are uncer- but it is in the range estimated for the lower 2005; Andersson et al., 2006a; Bergman et al., tain for the two juvenile analyses at 2.24 and crust (0.015–0.020) (e.g., Taylor and McLen- 2008; Skiöld and Rutland, 2006; Williams et 2.35 Ga, and they may also in reality be Archean. nan, 1995; Wedepohl, 1995; Rudnick and Gao, al., 2008). Inherited grains and cores in igneous One of these has a very radiogenic Hf-isotope 2003). A relatively mafi c composition, similar rocks also follow this distribution (e.g., Kum- composition. Due to the low Lu/Hf ratio in zir- to that of the lower crust, would be anticipated pulainen et al., 1996; Ehlers et al., 2004). These con, this depleted character will be present in this for such a juvenile mantle–derived protocrust. data clearly suggest major formation of crust sample irrespective of age, and it thus shows the This evolution trend is slightly revised from that ca. 2.1–1.91 Ga; the available Nd-isotope data existence of very juvenile material in the crustal of Andersen et al. (2009a), taking into account and zircon-Hf isotopic data indicate that much mixture at the time of its formation. the additional data. of this crust was juvenile. Andersen et al. (2009a) suggested that the lim- ε Except for one grain, the present data for ited spread in initial Hf data for zircons from Sve- Sub-Svecofennian Mantle zircons from the felsic metavolcanic rocks, and cofennian and Transscandinavian Igneous Belt most of the igneous zircons of the Transscandi- granitoids could be explained by derivation from The data for the two mafi c samples are the navian Igneous Belt granite, show positive initial preexisting juvenile Svecofennian crust that is fi rst reported for zircons in early Svecofennian ε ε Hf values. Sample U97-3 shows slightly lower approximately defi ned by the evolution Hf(1.88) mafi c rocks. Even if the overlap with zircons ε 176 177 ≈ ε Hf values, compared with U97-1, including one = 2 ± 3 and Lu/ Hf 0.015. The presence of from the felsic rocks is substantial, their Hf in slightly below CHUR. This may be correlated a juvenile Svecofennian protocrust is supported general ranges to higher values (Fig. 3). The ε with its inferred character as a redeposited vol- by the positive Hf values of 2.2–1.9 Ga inher- range indicates mildly to relatively strongly canogenic sediment (Andersson et al., 2006a); ited zircons in granites (Fig. 3; Andersen et al., depleted sources, though not as depleted as ε Svecofennian metasediments typically contain 2009a; Kurhila et al., 2010). The coexistence of the DM. Initial Nd data for early Svecofennian

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mafi c rocks range from DM to values slightly mafi c rocks were derived from depleted mantle encompasses the composition of the Strömsbro below CHUR, but most are “mildly depleted” sections that acquired their variably mildly zircons, but not that of the northern complexes (see compilations in Andersson et al., 2004; depleted characters through additions of fl uids (Fig. 3). Thus, the Lu-Hf isotopic system also Rutanen and Andersson, 2009). These data, and and melts carrying an Archean isotopic imprint supports the presence of signifi cant Archean ε particularly the dominant initial Nd (+1 to +2) into the mantle wedge by subduction during arc components in these rocks. of mafi c Transscandinavian Igneous Belt rocks and microcontinent assembly and reworking in As with the Nd isotopes (e.g., Rämö, 1991), ε in southern Sweden (e.g., Andersson, 1997b; proto-Svecofennian time (<2.3–1.9 Ga). The the Hf evolution of the Svecofennian crust Claeson, 2001; Andersson et al., 2007; Rutanen associated felsic crustal rocks derived their over- encompasses the compositional range of zir- and Andersson, 2009), suggest the widespread lapping isotopic signature through reworking of cons from rapakivi granites from SE and SW occurrence of “mildly depleted” mantle sources the juvenile mafi c crust and further minor addi- Finland (Fig. 3), suggesting juvenile crustal in this part of the shield. Similarly, in southern tions of Archean crustal components (Fig. 3). sources for this magmatism. However, the vari- Finland, mafi c 1.9–1.8 Ga rocks have chondritic With the accumulation of more data on early able presence of small amounts of Archean com- ε ε to mildly positive Nd values (e.g., Lahtinen and Svecofennian mafi c rocks, initial Hf values are ponents in the Svecofennian meta-igneous crust Huhma, 1997; Andersson et al., 2006b; Rutanen likely to show an increased spread, refl ecting (cf. e.g., Andersen et al., 2009a; Kurhila et al., et al., 2011). This, together with MORB-like, or variously enriched sections of the sub-Svecofen- 2010) should also have affected the younger lower, contents of high fi eld strength elements nian mantle. This is tentatively demonstrated by igneous rocks derived from it. In the Strömsbro and enrichments in light rare earth and large Hf-isotope data from 2.15 to 1.97 Ga mafi c intru- complex, the presence of Archean components ε − ion lithophile elements relative to MORB, led sions in Finland (Patchett et al., 1981), some of is indicated by the equally low Nd values ( 5) Andersson et al. (2006b, 2007) to suggest that which refl ect increased contributions of Archean for the associated mafi c rocks, suggesting either the sources for this magmatism represent pre- crustal components toward the craton in the east. Archean enriched-mantle sources or contamina- viously depleted mantle that became enriched However, if the Hf-isotope data remain similar to tion by Archean material in the crust (Anders- ε during Svecofennian (<2.1 Ga) arc development the Nd-isotope data, most of the data are expected son, 1997c). The variation in the ranges of Hf (cf. refertilization of the subcontinental litho- to be “mildly depleted,” roughly coinciding with among the individual rapakivi complexes in spheric mantle discussed by, e.g., Griffi n et al., the evolution sketched in Figure 3. central Sweden is most likely related to local 2000, 2009, and references therein). variations of the Archean/Svecofennian ratio in Rutanen et al. (2011) suggested a hetero- Source Variations in Fennoscandian their respective source areas. However, the pre- geneous distribution of such mantle sections Rapakivi Complexes viously reported presence of Archean zircons to explain the variation from slightly subchon- in the 1.52 Ga Nordsjö syenite (Claesson et al., ε dritic to strongly depleted initial Nd values in The zircon data for the central Swedish 1997) has not been possible to reaffi rm as yet the early Svecofennian mafi c rocks. An evolu- rapakivi granitoids show an overall range in ini- (Andersson and Claesson, personal commun.). ε ε − − tion of the sub-Svecofennian mantle defi ned by tial Hf values of ~9 units ( 10 to 1.5), and a In any case, the zircon Hf-isotope data provide 147Sm/144Nd = 0.155 ± 0.015 would encompass within-sample variation of less than 3.5 ε units, additional independent evidence for the presence ε the initial Nd ranges for most post-Svecofennian while the total spread between DM and the Fen- of a buried Archean basement beneath central mafi c suites in the Svecofennian Domain, and it noscandian Archean crust at 1.5 Ga is ~22 units Sweden (cf. Andersson et al., 2002). is compatible with the 147Sm/144Nd ratios mea- (Fig. 3). Thus, the Hf data allow an interpreta- This basement has been interpreted to rep- sured in enriched mantle xenoliths from else- tion that the zircons crystallized from thoroughly resent the core of the Bothnia microcontinent where (e.g., McDonough and McCulloch, 1987; mixed magmas with variable proportions of that docked with the craton around 1.90 Ga in Voshage et al., 1987; Gorring and Kay, 2000; crustal- and mantle-derived material, or from the orogenic collage of Lahtinen et al. (2005). Schmidberger et al., 2001). magmas with an origin entirely within a strongly The appearance of anorthosite-mangerite-char- ε Although the initial Hf values of various enriched mantle. However, the dominantly gra- nockite-granite suites, rapakivi granites, and 1.6–0.28 Ga mafi c rock suites in southern Fen- nitic compositions (cf. Andersson, 1997a, 1997c, associated dike swarms at ca. 1.6–1.5 Ga has noscandia show variations in detail, compat- 2001), relatively unradiogenic Hf isotopes, and been related to the initiation of breakup of the ible with variable degrees of source enrichment small and characteristic within-sample Hf iso- Paleoproterozoic supercontinent (e.g., Rogers (Söderlund et al., 2005), they broadly follow a topic variations favor distinct crustal sources for and Santosh, 2002; Zhao et al., 2004). ε common evolution that was defi ned by Andersen the granitoids of each complex. Initial Hf data for zircons from the rapa kivi- ε 176 177 et al. (2009a) as Hf(1.60) = 3 ± 3 and Lu/ Hf The distinctly more radiogenic zircons of the associated mafi c rocks in southern Finland ≈ 0.033 (excluding the more depleted Central Strömsbro granite, compared with those from (Heinonen et al., 2010) are largely encompassed Svecofennian Dolerite Group), i.e., essentially the complexes farther north, strengthen the case by the evolution of the “mildly depleted” Fen- parallel to CHUR. However, the present early made from whole-rock Nd isotopes (Anders- noscandian lithospheric mantle (Fig. 3), sug- Svecofennian data show slightly more depleted son, 1997c) that this complex contains signifi - gesting that this represents a possible major initial values and constrain, together with the cantly less of a much older crustal component. source also for these magmas. However, excur- younger intrusions from southern Fennoscan- In fact, the initial Nd-isotope composition of the sions to both more and less radiogenic compo- ε dia, an evolution of approximately: Hf(1.89) Strömsbro granite is encompassed by the evo- sitions indicate magma components from the = 4.5 ± 2.5 and 176Lu/177Hf ≈ 0.0315 (Fig. 3), lutionary fi eld of the early Svecofennian meta- crust as well as a more depleted mantle. representing an early Svecofennian “mildly igneous crust (even if within its lowest range), depleted mantle,” similar to the one suggested while the compositions of those farther north CONCLUSIONS by Nd isotopes for the Transscandinavian Igne- range to lower values, suggesting involvement ε ous Belt and many early Svecofennian rocks of up to 40% Archean components (Anders- 1. Initial Hf values in zircon from early Sve- (e.g., Andersson et al., 2004, 2007; Rutanen and son et al., 2002). Similarly, the proposed Hf- cofennian (ca. 1.89 Ga) felsic volcanic rocks Andersson, 2009). Thus, the early Svecofennian isotopic evolution of the Svecofennian crust range from −1.8 to +5.1, similar to the range in

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early Svecofennian granitoids, supporting a dom- ivi complexes of central Sweden: Implications from U-Pb zircon ages, Nd, Sr and Pb isotopes: Transactions inance of juvenile Proterozoic sources for such REFERENCES CITED of the Royal Society of Edinburgh, Earth Sciences, magmas in the southern Svecofennian province. v. 92, p. 201–228. 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The conclusion, drawn earlier from Nd- Swedish occurrences: Sveriges Geologiska Under- lution of granitoids in the central Eastern Segment, isotope data, that central Sweden is underlain by sökning, v. ca 87, p. 33–49. southern Sweden: International Geology Review, iFirst lithosphere that contains Archean components, Andersson, U.B., 1997b, Petrogenesis of some Proterozoic article, doi:10.1080/00206814.2010.543785. granitoid suites and associated basic rocks in Sweden Charlier, B.L.A., Bachmann, O., Davidson, J.P., Dungan, is further supported by the new Hf data. In con- (geochemistry and isotope geology): Sveriges Geolo- M.A., and Morgan, D.J., 2007, Upper crustal evolution trast, the Svecofennian in Bergslagen is domi- giska Undersökning, Rapporter och Meddelanden, of a large silicic magma body: Evidence from crystal- v. 91, p. 1–216. scale Rb-Sr isotopic heterogeneities in the Fish Can- nated by juvenile (<2.2 Ga) crustal additions Andersson, U.B., 1997c, The sub-Jotnian Strömsbro granite yon magmatic system, Colorado: Journal of Petrology, with only minor Archean components, presum- complex at Gävle, Sweden: GFF, v. 119, p. 159–167. v. 48, p. 1875–1894. ably mostly derived from the metasediments. Andersson, U.B., 2001, An overview of the geochemical Claeson, D.T., 2001, Investigation of gabbroic rocks associ- evolution in the Mesoproterozoic (1.58–1.50 Ga) anoro- ated with the Småland-Värmland granitoid batholith genic complexes of central Sweden: Zeitschrift für of the Transscandinavian Igneous Belt [Ph.D. thesis], ACKNOWLEDGMENTS Geologische Wissenschaften, v. 29, p. 455–470. A64: Earth Sciences Centre, Gothenburg University, Andersson, U.B., and Öhlander, B., 2004, The late Svecofen- Sweden, 11 p. and 7 appendixes. nian magmatism, in Högdahl, K., Andersson, U.B., and Claesson, S., and Lundqvist, Th., 1995, Origins and ages of This work was supported by ARC (Australian Eklund, O., eds., The Transscandinavian Igneous Belt Proterozoic granitoids in the Bothnian Basin, central Research Council) Linkage project LP0776637 (TIB) in Sweden: A Review of its Character and Evo- Sweden: Isotopic and geochemical constraints: Lithos, lution: Geological Survey of Finland Special Paper 37, v. 36, p. 115–140. to S.Y. O’Reilly. The analytical work at the ARC p. 100–102. Claesson, S., Huhma, H., Kinny, P.D., and Williams, I.S., National Key Centre for Geochemical Evolu- Andersson, U.B., and Wikström, A., 2001, Growth-related 1993, Svecofennian detrital zircon ages—Implications tion and Metallogeny of Continents (GEMOC) 1.85–1.55 Ga magmatism in the Baltic Shield: A review for the Precambrian evolution of the Baltic shield: Pre- addressing the tectonic characteristics of Svecofen- cambrian Research, v. 64, p. 109–130. used instrumentation purchased and supported nian, TIB 1-related, and Gothian events—A discussion: Claesson, S., Andersson, U.B., Schuhmacher, M., Sunde, T., with funding from ARC, DEST, Macquarie GFF, v. 123, p. 55–58. Whitehouse, M., and Vestin, J., 1997, Inherited Archaean University, and industry. This is publication Andersson, U.B., and Wikström, A., 2004, The Småland components in a Mesoproterozoic rapakivi complex Värmland belt (SVB): Overview, in Högdahl, K., Ander- from central Sweden: Implications from SIMS U-Pb 782 from ARC National Key Centre GEMOC, sson, U.B., and Eklund, O., eds., The Transscandinavian imaging and spot analysis of zircon: EUG 9 meeting and publication 12 of the ARC Centre of Excel- Igneous Belt (TIB) in Sweden: A Review of its Charac- (European Union of Geosciences), Strasbourg, 23–27/3 ter and Evolution: Geological Survey of Finland Spe- 1997, Abstract Supplement 1: Terra Nova, v. 9, p. 356. lence for Core to Crust Fluid Systems (CCFS). cial Paper 37, p. 15–20. Condie, K.C., 2000, Episodic continental growth models: The reviews of P.J. Patchett and one anonymous Andersson, U.B., Neymark, L.A., and Billström, K., 2002, Afterthoughts and extensions: Tectonophysics, v. 322, reviewer helped to improve the paper. Petrogenesis of Mesoproterozoic (sub-Jotnian) rapak- p. 153–162.

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