Isotopic investigations of metasedimentary and igneous rocks in the Palaeoproterozoic Bothnian Basin, central Sweden

Welin, Eric; Christansson, K.; Kähr, Ann-Marie

doi:10.1080/11035899309453915

Cited by 46 publications

(29 citation statements)

References 26 publications

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“…Possible candidates include the 1.92-1.93 Ga rocks near the Archaean-Proterozoic boundary in east-central Finland (e.g. Kousa et al 1994), the 1.95 Ga Knaften granitoid in northern Sweden (Wasström 1993) and the 2.03 Ga Njurunda granite in central Sweden (Welin et al 1993). The ca.…”

Section: Discussionmentioning

confidence: 99%

Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

Kähkönen¹

1999

Bull Geol Soc Finland

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Section: Discussionmentioning

confidence: 99%

Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

Kähkönen¹

1999

Bull Geol Soc Finland

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“…The existence of minor U, Mo, Ni and V occurrences in the Alum Shale [48] proves that mobilisation of fluids was an integral part of this evolution. Further evidence for hydrothermal event(s) preceding the Caledonian orogeny were presented by Sherlock et al [49] who suggested, on the basis of 40 Ar- 39 Ar data on K-feldspar overgrowths, that hydrothermal processes affected the ore-bearing sandstones at Laisvall at around 570-530 Ma ago.…”

Section: Constraints On the Timing Of Ore Formationmentioning

confidence: 99%

Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

et al. 2012

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Abstract:The epigenetic Zn-Pb deposits in the Lycksele-Storuman ore district, northern Sweden, are hosted by Paleoproterozoic basement near the margin of the Caledonian mountains. A paleogeographic reconstruction suggests that platform sediments, including Cambrian shales, overlaid the mineralised basement. The mineralisation type, containing sphalerite, galena, calcite and fluorite, is confined to veins and breccias and interpreted to be of Mississippi Valley Type (MVT) style. There is no appreciable wall rock alteration. Fluid inclusion work reveals coexisting aqueous and hydrocarbon fluids. Ore deposition is interpreted to have occurred during mixing of two fluids; a cool (<70 °C) brine with a salinity of 30 eq. mass% CaCl 2 and a hot (~200 °C) brine with about 18 eq. mass% CaCl 2 . The mixing led to complex Sr isotope systematics in the analysed minerals. A tentative sphalerite Rb-Sr isochron age of a 534 ± 13 Ma probably dates mineralisation. The isotope systematics of Pb and Nd are less complex and both elements were essentially leached OPEN ACCESSMinerals 2012, 1 170 from basement rocks and transported by the hot fluid. Ore formation is considered to have taken place during rifting, related to the opening of the Iapetus Ocean.

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“…Studies of detrital zircons in post-1.9 Ga metasediments have revealed that source areas with ages of 2.1-1.9 Ga were available for erosion ~1.9 Ga ago (Huhma et al, 1991;Claesson et al, 1993;Welin et al, 1993), although no such areas could be identified. Lundqvist et al (1998) considered that, in Sweden, sediments were deposited in the Bothnian Basin ( Fig.…”

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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Isotopic investigations of metasedimentary and igneous rocks in the Palaeoproterozoic Bothnian Basin, central Sweden

Cited by 46 publications

References 26 publications

Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

Stratigraphy of the central parts of the Palaeoproterozoic Tampere Schist Belt, southern Finland: review and revision

Zn-Pb Ores of Mississippi Valley Type in the Lycksele-Storuman District, Northern Sweden: A Possible Rift-Related Cambrian Mineralisation Event

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

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