U-Pb zircon ages and Rb-Sr whole-rock isotope studies of early Proterozoic volcanic and plutonic rocks near Tampere, southern Finland

Kähkönen, Y.; Huhma, Hannu; Aro, Kristiina

doi:10.1016/0301-9268(89)90029-6

Cited by 41 publications

(23 citation statements)

References 40 publications

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“…In addition, they resemble the cross-bedded Kalkku arenites in petrography and geochemistry (unpublished data of the author). The Kalkku "porphyry", dated at 1889+19 Ma by Kähkönen et al (1989), is also evidently a massive arenite. Therefore, this date gives the age of the rocks in the source area.…”

Section: Tohloppi-tesoma-kalkku Areamentioning

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: Tohloppi-tesoma-kalkku Areamentioning

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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“…Most of the ages quoted haveb een measured by ID-TIMS zircon U-Pb. The stratigraphic profiles in the syncline (Kähkönen et al, 1989;Kähkönen, 1999) showa nu pwardt ransition from turbidite-dominated submarine environments to volcanic-dominated, in part subaerial, environments. The turbidites below the volcanics occur mainly in the southern limb of the main syncline, where they are named the Myllyniemi formation (Fig.…”

Section: 1the Ta Mpere Schist Beltmentioning

confidence: 99%

“…makes some analogy with Stromboli shoshonitic lavas. Localities in the N limb of the main syncline givez ircon ages of 1904±4 and 1898±4 Ma; ~1.89 Ga (Kähkönen et al, 1989). A unit considered to represent the lowermost major volcanic unit among the turbidites in the southern limb has yielded a SIMS age of 1898±8 Ma, and a high-K rhyolite near the top of this succession has given a TIMS age of 1892±3 Ma (Kähkönen et al, 2004).…”

Section: 1the Ta Mpere Schist Beltmentioning

confidence: 99%

“…One conglomerate (the Veittijärvic onglomerate) contains plutonic clasts dated at~1.88-1.89 Ga (Nironen, 1989b), and provides evidence of syn-depositional uplift and erosion. The deposition age of this conglomerate must lie between the age of the underlying rhyolite (1892±3 Ma) and thea ge of overlying volcanics int he core of the main syncline (1889±5 Ma, Kähkönen et al, 1989). The latter date also further constrains the age of the intrusion from which the granitoid pebbles originated.…”

Section: 1the Ta Mpere Schist Beltmentioning

confidence: 99%

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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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“…The belt is bordered in the south by the Granite Migmatite Belt, where the age of metamorphism is 1.810-1.830 Ga, and in the north by the Central Finland Granitoid Complex in which the granitoids are 1.888-1.870 Ga old (Korsmän et al 1997b). The granitoid complex is separated from the trondhjemite migmatites by the Tampere Schist Belt largely composed of 1.904-1.889 Ga old arc-type volcanic rocks (Kähkönen et al 1989). The Tonalite-Trondhjemite Migmatite Belt includes mafic and ultramafic metalavas that are possibly close to the Haveri metabasalts of the Tampere Schist Belt in age; Vaasjoki and Huhma (1999) yielded whole rock Pb-Pb model ages of 1.9-2.0 Ga for the latter.…”

Section: Introduction and Geological Features Of The Study Areamentioning

confidence: 99%

Tectono-metamorphic evolution and timing of the melting processes in the Svecofennian Tonalite-Trondhjemite Migmatite Belt: An example from Luopioinen, Tampere area, southern Finland

Mouri¹,

Korsman²,

Huhma³

1999

Bull Geol Soc Finland

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which is characterized by Kfs-poor leucosomes and borders the former belt in the north. The present paper deals with selected migmatitic rocks from the latter belt. It is aimed to study the temporal and structural relationships of the different leucosome generations, and to establish the pressure-temperature-time paths of this belt.The Tonalite-Trondhjemite Migmatite Belt consists mainly of migmatitic rocks with various types of synorogenic granitoids and minor mafic and ultramafic rocks. The mesosome of the migmatites consist of garnet-sillimanite-biotite-plagioclase-cordierite-quartz assemblages with rare K-feldspar and late andalusite. The oldest leucosomes are dominated by plagioclase and quartz, and the content of K-feldspar increases in later leucosomes. Microtextural analysis in conjunction with THERMOCALC calculations and geothermometry shows that these rocks were metamorphosed at peak conditions of 700-750°C at 4-5 kbar and aH,0 = 0.4-0.7. The formation of cordierite coronas around garnet and the late crystallization of andalusite suggest that the final stage of the P-T history was characterized by decompression and cooling within the andalusite stability field, estimated at 500-650°C and 3-4 kbar.Detailed isotopic dating of mesosome and leucosomes of the migmatites was undertaken by conventional U-Pb analyses on monazite and zircon, Sm-Nd analyses on garnet, and ion probe dating on zircon. The monazites are nearly concordant with an average age of 1878.5±1.5 Ma, and garnet-whole rock analyses show that the concordant leucosomes and the mesosome are coeval within error margins having ages of 1893±40 and 1871114 Ma, respectively. However, garnet in the discordant vein leucosome provides an age of 1843±11 Ma, which is marginally younger than the age of the adjacent mesosome and the concordant leucosome (1877+18 and 1880±23 Ma, respectively) and the age of monazite. Zircons from the studied migmatites display complex zoning structures using SEM-based CL-imaging. Most grains have distinct cores, clearly remnants of original grains. The cores display various types of zoning but oscillatory zon-32 H. Mouri, K. Korsman and H. Huhma ing dominates. The cores are overgrown by one or two thin outer rims that are of two types: i) unzoned outer rim, considered as overgrowth of new zircon during a metamorphic event, and ii) weakly oscillatory zoned rim, considered as typical of magmatic recrystallization. Ion probe dating of cores yielded slightly discordant 207 Pb/ 206 Pb ages of between 2866-2002 Ma, which are interpreted as protolith age. Rims yielded two major age groups: the unzoned rims gave ages of 1872-1886 Ma, whereas the rims with oscillatory zoning yielded ages of 1951-1959 Ma. The youngest age group is consistent with the conventional Sm-Nd dating on garnet and U-Pb dating on monazite and we suggest that the migmatites were metamorphosed at granulite facies conditions at ca. 1880 Ma. The 1951-1959 Ma age group yielded by magmatic zircon rims remains difficult to interpret, but may reflect a magmatic eve...

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U-Pb zircon ages and Rb-Sr whole-rock isotope studies of early Proterozoic volcanic and plutonic rocks near Tampere, southern Finland

Cited by 41 publications

References 40 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

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

Tectono-metamorphic evolution and timing of the melting processes in the Svecofennian Tonalite-Trondhjemite Migmatite Belt: An example from Luopioinen, Tampere area, southern Finland

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