The Central Puolanka Group - a Precambrian regressive metasedimentary sequence in northern Finland

Laajoki, K.

doi:10.17741/bgsf/58.1.012

Cited by 10 publications

(4 citation statements)

References 3 publications

(3 reference statements)

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“…Laajoki (1986b) suggests a possible Sariolan age for the Lapponian supergroup, but the basal greywacky conglomerates of the Kumpu association show Sariolan characteristics unless that of glacial drift (Mikkola 1941) despite the glaciation of continental dimension (Ojakangas 1985). The Lapland greenstone belt together with the granulitic belt resembles the Lopian greenstone belts, in adjacent U.S.S.R., which are similarly characterized by bimodal metavolcanic rocks (Musatov et al 1984) and the flysch-like terrigenous metasediments at the middle level (Sokolov and Heiskanen 1985); the Lopian orogenic megacycle occurred between the Saamian and the Karelian, too (Kratz et al 1984).…”

Section: Discussionmentioning

confidence: 99%

“…The Karelian supergroup is composed of the Sariolan and Jatulian deposits (Gaål and Gorbatschev 1987). The Sariolan coarse-clastic rocks are of limited occurrence and record stable platformal, riftal or glacial palaeoenvironments (Pekkarinen 1979;Gaål 1980;Marmo and Ojakangas 1984;Laajoki 1986a;Marmo et al 1986), whereas the Jatulian quartzites were deposited in a shallow epicontinental sea (Ojakangas 1965) and are in turn overlain by the Marine-Jatulian dolomite-black-slate association; the Karelian sequence includes also mafic metavolcanic rocks, (Meriläinen 1980;Simonen 1980).…”

Section: + -F I Rapakivi Granitesmentioning

confidence: 99%

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The Lapland greenstone belt: Stratigraphic and depositional features in northern Finland

Saverikko¹

1987

Bull Geol Soc Finland

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The Lapland greenstone belt formed in a continental environment, as a result of rifting of the 3.1-3.0 Ga Saamian craton. The basin subsided to a depth of five kilometres between 3.0-2.5 Ga and contains a sequence which is subdivided into Lower, Middle and Upper Lapponian groups, with the Middle Lapponian metasediments separating the Lower Lapponian Salla-Jauratsi and Upper Lapponian Kittilä greenstone successions. After a folding episode the Lapponian supergroup was covered with the Kumpu conglomerate-metasandstone-slate suite, occurring as Karelian, i.e. Sariolan-Jatulian, deposits. A few erosional remnants are capped with Svecofennian rocks 1.9 Ga old.The Lower Lapponian consists of basal arkose, the Möykkelmä greenstones, a cratonic quartzite-carbonate-schist suite and the Salla greenstone complex(es) preserving evidence of a lava plateau. The Salla bimodal metavolcanic rocks and the Middle Lapponian metasediments, which, at their thickest, constitute the Oraniemi arkose-slate-quartzite association (incl. redbeds), evidently indicate cratonic rifting that terminated with the growth of isolated lava fields of Fe-rich tholeiitic basalt. In the Upper Lapponian, euxinic-exhalative metasediments underlie the Sattasvaara, Sotkaselkä and Kummitsoiva komatiite complexes and the Kittilä greenstones, which are present as complicated but distinct eruption centres and contain a varying amount of ejecta and volcaniclastic greywacke-slate intercalations. The komatiite-dominant succession evidently represent mantle-activated rifting and the linear mantle upwelling.The Lapland greenstone belt and adjacent granulitic belt appear to constitute a paired metamorphic terrain, where the overthrusting of the granulites is explained by mutual motions of the distinct cratonic megablocks.

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Section: Discussionmentioning

confidence: 99%

Section: + -F I Rapakivi Granitesmentioning

confidence: 99%

The Lapland greenstone belt: Stratigraphic and depositional features in northern Finland

Saverikko¹

1987

Bull Geol Soc Finland

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“…The PjF is the stratigraphically lowest unit of the westernmost non-gneissic supracrustal unit, the Central Puolanka Group (CPG) (Laajoki, 1986a). and occupies the eastern limb of an east-verging refolded anticline.…”

Section: T H E G E O L O G I C a L S E T T I N G O F T H E P U O L A mentioning

confidence: 99%

“…Within the above subareas (Figs 1, 2, 4 and 7) four main primary sedimentary facies can be distinguished (Laajoki, 1986a;Laajoki & Korkiakoski, 1988): (1) massive or graded sandstones, metamorphosed to monotonous arkose-quartzite and consisting mainly of quartz and plagioclase with subordinate biotite and muscovite; (2) graded sandstones and mudstones, the latter being metamorphosed to quartz-two-mica-plagioclase schist with abundant porphyroblasts of staurolite, garnet, biotite and andalusite and segregations of sillimanite and cordierite; (3) cross-bedded or rippled fine sandstones or siltstones (semipelites). metamorphosed to assemblages of quartz, plagioclase and micas with rare staurolite porphyroblasts, and (4) cross-bedded sandstones metamorphosed to arkosequartzite.…”

Section: Metasedimentsmentioning

confidence: 99%

Metamorphic and structural evolution of the Early Proterozoic Puolankajärvi Formation, Finland – I. Structural and textural relations

Laajoki

Tuisku

1990

Journal Metamorphic Geology

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The amphibolite facies PuolankajZuvi Formation (PjF) occupies the western margin of the Early Proterozoic Kainuu Schist Belt (KSB) of northern Finland. The lower and middle parts of the PjF consist of turbiditic psammites and pelites and tempestitic semipelites. This report concentrates on the pelitic lithologies which include quartz-two-mica-plagioclase schists with variable amounts of garnet, staurolite, andalusite and biotite porphyroblasts as well as sillimanite and cordierite segregations. The KSB forms a major north-south-trending synclinorium between two Archaean blocks. It contains both autochthonous and allochthonous units and is cut by faults and shear zones. The PjF lies on the western side of the KSB and is probably allochthonous. The formation has undergone six major deformation phases (D,, Dzr D,.. D3,. D, and DS). During D,-D, the maximum principal stress (a,) changed in a clockwise direction from south-west to northeast. Between Dz and D, the intermediate principal stress (uz) changed from horizontal to vertical and the interval between D, and D, marks a transition from thrust to strike-slip tectonics. Relict structures in the porphyroblasts indicate the following mineral growth-deformation evolution in the PjF. (1) Throughout the PjF there was a successive crystallization of garnet (syn-D,). poryphyroblastic biotite (inter-D,) and staurolite (inter-Dy,) during the pre-D, stage. (2) A syn-D,-inter-D,, crystallization of kyanite, sillimanite (fibrolite), porphyroblastic tourmaline, magnetite, rutile, cordierite and muscovite-biotite-plagioclase pseudomorphs after staurolite was most localized at and near D, shear zones. (3) A syn-to post-D, generation of andalusite, ilmenohematite and sheet silicates after staurolite and after cordierite occurred near D5 faults.The evolution outlined here permits the relative dating of the PjF parageneses, which is used in the second part of the study (Tuisku & Laajoki, 1990). and, together with the knowledge of the pressure-temperature conditions during various growth events, makes it possible to compile pressuretemperature-deformation paths for the PjF.

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The metamorphic behaviour and petrogenetic significance of zinc in amphibolite facies, staurolite-bearing mica schists, Puolankajärvi Formation, Central Finland

Tuisku

Ruosresuo

Häkkinen

1987

Geochimica et Cosmochimica Acta

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The Central Puolanka Group - a Precambrian regressive metasedimentary sequence in northern Finland

Cited by 10 publications

References 3 publications

The Lapland greenstone belt: Stratigraphic and depositional features in northern Finland

The Lapland greenstone belt: Stratigraphic and depositional features in northern Finland

Metamorphic and structural evolution of the Early Proterozoic Puolankajärvi Formation, Finland – I. Structural and textural relations

The metamorphic behaviour and petrogenetic significance of zinc in amphibolite facies, staurolite-bearing mica schists, Puolankajärvi Formation, Central Finland

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