The thermotectonic evolution of a Proterozoic, low pressure, granulite dome, West Uusimaa, SW Finland

Schreurs, J. W. H.; Westra, L.

doi:10.1007/bf00371326

Cited by 83 publications

(35 citation statements)

References 38 publications

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“…1), including N-S striking planar structures. Schreurs and Westra (1986) described mesoscopic and macroscopic folding (their F 3 ) with subvertical N-S striking axial surfaces in the Suomusjärvi-Mustio area (Fig. 1) and concluded that granulite grade metamorphism preceded F 3 folding.…”

Section: Discussionmentioning

confidence: 97%

Structural and magmatic evolution in the Loimaa area, southwestern Finland

Nironen¹

1999

Bull Geol Soc Finland

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Section: Discussionmentioning

confidence: 97%

Structural and magmatic evolution in the Loimaa area, southwestern Finland

Nironen¹

1999

Bull Geol Soc Finland

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“…Theses data, with apparent clusters at c. 1850 − 1840, 1830 − 1820, 1815 and 1795 Ma, suggest that high heat flow events may have been episodic rather than continuous, in accordance with the view of Kurhila et al (2005) who stated that the heat flow took place in separate pulses. Successive intrusion of mafic magmas into mid-crustal levels could account for the episodic heat pulses (Schreurs & Westra, 1986). Metamorphism at c. 1795 Ma was evidently more widespread in the deeper crust and can now only be sporadically detected at the present erosion level.…”

Section: Regional Implicationsmentioning

confidence: 97%

U-Th-Pb zircon geochronology on igneous rocks in the Toija and Salittu Formations, Orijärvi area, southwestern Finland: Constraints on the age of volcanism and metamorphism

Väisänen¹,

Kirkland²

2008

Bull Geol Soc Finland

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Zircons from a felsic volcanic rock in the Toija Formation and a synvolcanic gabbro intrusion in the Salittu Formation within the Orijärvi area were dated by U-Th-Pb SIMS in order to provide depositional constraints on these formations. Zircon crystals from the felsic rock preserve a two-stage crystallisation history with zoned core domains and homogeneous rim domains. Inner domains yield a 1878 ± 4 Ma concordia age, interpreted to determine the crystallisation of this rock. Rims yield a 1815 ± 3 Ma concordia age interpreted to determine the regional metamorphism. Small rounded zircon grains from the Salittu gabbro, located within the Jyly shear zone, yield a concordia age of 1792 ± 5 Ma. We interpret the grain textures to suggest that they recrystallised from inherited zircon seeds during the heat and fluid flow into the shear zone. Although no direct ages for the Salittu Formation have been recovered, field relationships imply that it was deposited between 1878 − 1875 Ma.

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“…Generation of the 1.84-1.81 Ga microcline granites is suggested to predate the end of recumbent F 1 folding (Shreurs & Westra, 1986) and the early stage of the recumbent, thrustrelated D 2 of Ehlers et al (1993). Thus, it also predates the peak metamorphic main folding, characterized by E-W trending upright folds (Schreurs & Westra, 1986;Bleeker & Westra, 1987;Ploegsma & Westra, 1990;Levin et al, 2005). In addition, Ploegsma & Westra (1990) recognized the Orijärvi triangle as a non-migmatized low tectonic strain area with preserved early deformation structures.…”

Section: Geological Settingmentioning

confidence: 99%

“…The older event is bracketed between U-Pb ages at 1882±6 Ma and 1877±6 Ma on sphenes and monazites, respectively (Hopgood et al, 1983). The younger event is characterized by high-temperature, low-pressure (HTLP) conditions (Korsman et al, 1999), P estimates ranging from 3 to 5 kbar and T from 550°C to 825°C (Schreurs & Westra, 1986), thus locally reaching granulite facies conditions. Peak metamorphic conditions of the younger event prevailed at ~1.830-1.815 Ga (Levin et al, 2005;Mouri et al, 2005).…”

Section: Geological Settingmentioning

confidence: 99%

“…Resolution of the original tectonic environment of these rocks, their geometry and kinematic history, and the relationship between deformation, magmatic events and metamorphism provide important constraints on understanding the Svecofennian orogeny. As a non-migmatized area with preserved deformation structures related to Simplified after Schreurs &Westra (1986). SSAC = Southern Svecofennian Arc Complex of .…”

Section: Introductionmentioning

confidence: 99%

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Supracrustal rocks in the Kuovila area, Southern Finland: Structural evolution, geochemical characteristics and the age of volcanism

Skyttä¹,

Käpyaho²,

Mänttäri³

2005

Bull Geol Soc Finland

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The supracrustal rocks of the Kuovila area in the Palaeoproterozoic Svecofennian Uusimaa Belt, southern Finland, consist mainly of volcaniclastic rocks associated with banded iron formations (BIFs) and marbles. Small ZnS and PbS mineralizations are occasionally located within the marbles. Some primary features are well preserved in the sedimentary and volcanic rocks, including lamination in tuffites and banded iron formations.Geochemical results show that the volcanism was bimodal and it mainly had volcanic arc affinity. Specific geochemical indicators suggesting a volcanic arc origin for the Kuovila volcanic rocks include: 1) Enrichment of LILE over the HFSE elements and 2) Distinctly low Nb and Ta contents in relation to Th, Ce and LREE. Geochemistry of the Kuovila area volcanic rocks is very similar to those of the Orijärvi and Kisko formations, located ~15 km NE of Kuovila. Felsic tuff in the Kuovila area was dated at 1891±4 Ma by the U-Pb system on zircons. Consequently volcanism was contemporaneous with magmatism in the adjacent Orijärvi area, thus representing the earliest identified volcanic stage in the southern Svecofennian Uusimaa Belt.Early deformation structures within the Kuovila area are suggested to relate to lowmetamorphic or localized low-angle thrusting during D 1 . F 1 folds were recumbent and the S 1 cleavages are generally weak. Thrusting was followed by approximately N-S contraction with upright, peak-metamorphic F 2 folding overprinting D 1 structures and defining the Kuovila synform. Two separate intrusive phases include a synvolcanic granodiorite-dioritegabbro association and a weakly S 2 -foliated syn-D 2 granodiorite. Anatectic granites and associated migmatizing veins are absent, therefore suggesting that D 2 pre-dates the ~1.84-1.82 Ga metamorphic event in the Southern Svecofennian Arc Complex (SSAC). D 2 structures in the Kuovila area are suggested to correlate with the early structures with associated axial planar cleavages in the Orijärvi area. D 2 strain is localized into axial planar high strain zones and the curvilinear patterns of the B 2 fold axes probably result from vertical stretching during D 2 .

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The thermotectonic evolution of a Proterozoic, low pressure, granulite dome, West Uusimaa, SW Finland

Cited by 83 publications

References 38 publications

Structural and magmatic evolution in the Loimaa area, southwestern Finland

Structural and magmatic evolution in the Loimaa area, southwestern Finland

U-Th-Pb zircon geochronology on igneous rocks in the Toija and Salittu Formations, Orijärvi area, southwestern Finland: Constraints on the age of volcanism and metamorphism

Supracrustal rocks in the Kuovila area, Southern Finland: Structural evolution, geochemical characteristics and the age of volcanism

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