Sm-Nd isotope systematics of 1.9-1.8-Ga granites from western Bergslagen, Sweden: inferences on a 2.1-2.0-Ga crustal precursor

Valbracht, Peter J.; Oen, I. S.; Beunk, F.F.

doi:10.1016/0009-2541(94)90102-3

Cited by 19 publications

(9 citation statements)

References 49 publications

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“…The upper limit of Archaean crust is the same as in Figure 5. suggested by a number of researchers to have preceded the main, early Svecofennian (1.91-1.86 Ga) magmatic event in many areas of the Shield (e.g. Valbracht et al 1994;Lahtinen & Huhma 1997), a tectonic situation that corresponds to the 'microcontinents' in the tectonic model of Lahtinen et al (2005). This model is based on: (1) the preponderance of juvenile (,2.1 Ga) depleted mantle Nd and Hf model ages (positive å values) of the majority of felsic, early Svecofennian (1.91-1.86 Ga) rocks (e.g.…”

Section: Sources Of Proterozoic Granitoids In Fennoscandiamentioning

confidence: 97%

“…This model is based on: (1) the preponderance of juvenile (,2.1 Ga) depleted mantle Nd and Hf model ages (positive å values) of the majority of felsic, early Svecofennian (1.91-1.86 Ga) rocks (e.g. Patchett & Kuovo 1986;Patchett et al 1987;Valbracht et al 1994;Claesson & Lundqvist 1995;Lahtinen & Huhma 1997;Andersson et al 2002Andersson et al , 2008; (2) the frequent occurrence of 2.1-1.90 Ga inherited zircons and the scarcity of 2.45-2.1 Ga zircon in Svecofennian metasedimentary and metaigneous rocks (e.g. Claesson et al 1993;Kumpulainen et al 1996;Lahtinen et al 2002;Ehlers et al 2004;Sultan et al 2005;Andersson et al 2006a;Bergman et al 2008); (3) the bimodal, felsic-mafic character of the 1.91-1.86 Ga magmatism, implying a preexisting crust (e.g.…”

Section: Sources Of Proterozoic Granitoids In Fennoscandiamentioning

confidence: 99%

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Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon

Andersen

Andersson²,

Graham

et al. 2009

JGS

189

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Zircons from nine Palaeoproterozoic granitoid intrusions within the southern part of the Fennoscandian Shield have been studied by laser ablation inductively coupled plasma source mass spectrometry to obtain U-Pb ages (in the range 1.88-1.68 Ga) and Hf isotope compositions. Six granitoids are from the 1.85-1.65 Ga Transscandinavian Igneous Belt; during that period more than 10 6 km 3 of granitoid magma intruded the pre-existing crust. The large majority of magmatic zircons from the nine granitoids have a limited initial range, 176 Hf/ 177 Hf ¼ 0.2816-0.2818, and define an evolutionary trend given by an initial value of å Hf(1:88Ga) % +2 AE 3 at an average 176 Lu/ 177 Hf ¼ 0.015. These data show that a geographically extensive, long-lived, relatively homogeneous, and dominant magma source resided within 2.1-1.86 Ga Svecofennian juvenile crust between 1.88 and 1.68 Ga. Zircon xenocrysts (1.91-1.98 Ga) with initial å Hf ¼ +0 to +2.5 from one of the intrusions provide additional evidence for such a long-lived crustal source of granitic magmas in central Fennoscandia. The granitoids were emplaced during a period of active mafic underplating that supplied heat to the anatectic zone in the lower-middle crust, but little or no mantle-derived Hf to the granitic magmas, in contrast to many mixed intermediate rocks.

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Section: Sources Of Proterozoic Granitoids In Fennoscandiamentioning

confidence: 97%

Section: Sources Of Proterozoic Granitoids In Fennoscandiamentioning

confidence: 99%

Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon

Andersen

Andersson²,

Graham

et al. 2009

JGS

189

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“…Chapter 8), results in initial 87 Sr/ 86 Sr(t) values between the unrealistically low 0.6977 (sample #5) and 0.7062. All except two samples (#2a and #5) have values higher than that estimated for the uniform reservoir at 1.80 Ga (0.7024;McCulloch and Chappell 1982;Faure 2001; Figure 15), resulting in positive e Sr (t) values (Table 2) The reference data are collected from Martin et al (1983), Wilson et al (1986), Valbracht (1991), O'Brien et al (1993), Valbracht et al (1994), Claesson and Lundqvist (1995), Billström and Weihed (1996), Andersson (1997), Kononova et al (1999Kononova et al ( , 2000, , Andersson et al (2002Andersson et al ( , 2006aAndersson et al ( , 2007, Högdahl et al (2008), Rutanen and Andersson (2009 and references therein), Woodard and Huhma (in review …”

Section: Sr Isotopesmentioning

confidence: 99%

1.8 Ga magmatism in southern Finland: strongly enriched mantle and juvenile crustal sources in a post-collisional setting

Rutanen

Andersson

Väisänen

et al. 2010

International Geology Review

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“…Evidence for a pre-1.9 Ga component in both the volcanic and plutonic 1.90-1.87 Ga suites has steadily accumulated (e.g. Lahtinen, 1994;Lahtinen & Huhma, 1997;Vaasjoki & Huhma, 1999, for Finland;Valbracht et al, 1994;Andersen & Sundvoll 1995;Claesson & Lundqvist 1995;Billström & Weihed, 1996;Lundqvist et al, 1998, for Sweden).…”

Section: Introductionmentioning

confidence: 99%

Pre-1.91 Ga deformation and metamorphism in the Palaeoproterozoic Vammala Migmatite Belt, southern Finland, and implications for Svecofennian tectonics

Rutland¹,

Williams²,

Korsman³

2004

Bull Geol Soc Finland

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A metamorphic event in the Vammala Migmatite Belt (VMB) at ~1.92 Ga, revealed by SHRIMP U-Pb analyses of both zircon overgrowths and monazite,is interpreted as post-depositional and is correlated with the development of the early high-grade schistosity.Neither this Early Svecofennian deformation and metamorphism, nor the associated complex folding, is present in the overlying Ta mpere Schist Belt (TSB) sequence, consistent with the VMB being part of a pre-1.91 Ga basement complex. The ~1.92 Ga event provides a maximum deposition age for the TSB,confirming earlier age estimates. Earlier stratigraphic correlations between parts of the VMB and TSB,and associated tectonic interpretations, can no longer be sustained.The crustal thickening seen in the VMB,and previously attributed to arc accretion at ~1.89 Ga, is now attributed to accretion of a large Svionian marginal basin during the 'Early Svecofennian' orogenic phase at ~1.92 Ga.This is of similar age to the deformation and metamorphism associated with collision in the Lapland-Kola Orogen to the north of the Karelian Province. The well-known post-TSB orogenic phase was also identified in the VMB by a monazite age of 1881±6 Ma. A granitoid intrusion gave an emplacement age of 1888±5 Ma, comparable to the age of granitoid clasts in the upper part of the TSB succession.The detrital zircon data are interpreted to suggest that deposition of the precursor VMB sediments probably took place soon after an earlier pre-depositional metamorphism at ~1.98 Ga, which affected igneous source complexes dated at ~1.99 Ga and ~2.01 Ga. Mafic rocks in the southern part of the VMB,and probably also the Haveri basalts, represent a renewed episode of extensional magmatism, which might correlate with the 1.96-1.95 Ga Jormua and Outokumpu ophiolites. A pre-1.96 Ga older stage basin has an expression in Sweden and complexes of similar age occur in the concealed Palaeoproterozoic basement south of the Gulf of Finland. Similar rocks, deformed and metamorphosed before ~1.96 Ga, might be present beneath the Central Finland granitoid complex and the late Svecofennian granite-migmatite zone,and were possibly more local sources for both the younger stage Svionian basin sediments and the post-1.91 Ga Bothnian Basin sediments.The TSB and other post-accretionary volcanic sequences, and the associated plutonism, are interpreted to reflect a ~40 m.y.extensional period, inboard of the contemporaneous active margin, between orogenic phases at ~1.92 Ga and ~1.88 Ga.This interpretation provides a more satisfactory explanation of the major heat input to the crust over a very wide area than does the arc accretion hypothesis.The tectonic evolution of the Svecofennian Province has strong similarities to that of the Palaeozoic Lachlan Fold Belt in eastern Australia.

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Sm-Nd isotope systematics of 1.9-1.8-Ga granites from western Bergslagen, Sweden: inferences on a 2.1-2.0-Ga crustal precursor

Cited by 19 publications

References 49 publications

Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon

Granitic magmatism by melting of juvenile continental crust: new constraints on the source of Palaeoproterozoic granitoids in Fennoscandia from Hf isotopes in zircon

1.8 Ga magmatism in southern Finland: strongly enriched mantle and juvenile crustal sources in a post-collisional setting

Pre-1.91 Ga deformation and metamorphism in the Palaeoproterozoic Vammala Migmatite Belt, southern Finland, and implications for Svecofennian tectonics

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