The Svecofennian orogeny is a series of related

orogenies Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

that resulted in the formation of much of the

continental crust Continental crust is the layer of igneous, sedimentary, and metamorphic rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called '' sial'' be ...

in what is today

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic countries, Nordic c ...

and

Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders with Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bot ...

plus some minor parts of

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...

. The orogenies lasted from about 2000 to 1800

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago ...

during the Paleoproterozoic Era. The resulting orogen is known as the Svecofennian orogen or Svecofennides. To the west and southwest the Svecofennian orogen limits with the generally younger

Transscandinavian Igneous Belt The Transscandinavian Igneous Belt ( sv, Transskandinaviska magmatiska bältet), abbreviated TIB, is one of the major lithological units of the Baltic Shield. It consists of a series of batholiths in Sweden and Norway forming a ca. 1400 km l ...

. It is assumed that the westernmost fringes of the Svecofennian orogen have been reworked by the Sveconorwegian orogeny just as the western parts of the Transscandinavian Igneous Belt has. The Svecofennian orogeny involved the

accretion Accretion may refer to: Science * Accretion (astrophysics), the formation of planets and other bodies by collection of material through gravity * Accretion (meteorology), the process by which water vapor in clouds forms water droplets around nucl ...

of numerous

island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...

s in such manner that the pre-existing

craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...

grew with this new material from what is today northeast to the southwest. The accretion of the island arcs was also related to two other processes that occurred in the same period; the formation of magma that then cooled to form

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

s and the

metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of ch ...

of rocks.

Development of the orogeny

The Svecofennian orogeny developed as a succession of four orogenies which by chronological order are: the Lapland-Savo orogeny, the Fennian orogeny, the Svecobaltic orogeny and the Nordic orogeny. In broad terms, regardless of details, it has been proposed that the Svecofennian orogeny involved more-less continuous subduction with subduction zones progressively migrating to the southwest. An alternative model postulates subduction included alternating

extension Extension, extend or extended may refer to: Mathematics Logic or set theory * Axiom of extensionality * Extensible cardinal * Extension (model theory) * Extension (predicate logic), the set of tuples of values that satisfy the predicate * Ext ...

and compression cycles, with the orogenic activity ceasing after the collision between the Fennoscandian Craton and the

Sarmatian Craton The Sarmatian Craton or Sarmatia is the southern segment/region of the East European Craton or Baltica, also known as Scythian Plateau. The craton contains Archaean rocks 2.8 to 3.7 billion years old (Ga). During the Carboniferous the craton was ...

Lapland-Savo orogeny

Prior to the onset of orogeny the

Archean The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth during the Arc ...

-aged craton of what is today northeastern Fennoscandia

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

ed creating an ocean basin, the "pre-Svecofennian Ocean", that then closed during the Svecofennian orogeny. The closure of this basin was indebted to

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

and resulted thus both in the formation of

s and the emplacement of the

Jormua Jormua is a very old village ashore the lake of Oulujärvi in the town of Kajaani, Finland Finland ( fi, Suomi ; sv, Finland ), officially the Republic of Finland (; ), is a Nordic country in Northern Europe. It shares land borders wi ...

and Outokumpu

ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found ...

s about 1950 million years ago. In the later stages of the Lapland-Savo orogeny an

, the Knaften arc, accreted to the Keitele-Karelia-Norrbotten

collage Collage (, from the french: coller, "to glue" or "to stick together";) is a technique of art creation, primarily used in the visual arts, but in music too, by which art results from an Assemblage (art), assemblage of different forms, thus creat ...

Fennian orogeny

The stage to the Fennian orogeny was set by a collision between Keitele and Karelia about 1920–1910 million years ago which resulted in a reorganization of the local

plate tectonic Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large te ...

s. As concequence the Bergslagen

microcontinent Continental crustal fragments, partly synonymous with microcontinents, are pieces of continents that have broken off from main continental masses to form distinct islands that are often several hundred kilometers from their place of origin. Caus ...

s collided with the Keitele–Karelia

starting the Fennian orogeny. The until then linear Fennian orogen was "buckled" from 1870 million years ago onwards due to an

orthogonal In mathematics, orthogonality is the generalization of the geometric notion of '' perpendicularity''. By extension, orthogonality is also used to refer to the separation of specific features of a system. The term also has specialized meanings in ...

change in

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

compressive stress In long, slender structural elements — such as columns or truss bars — an increase of compressive force ''F'' leads to structural failure due to buckling at lower stress than the compressive strength. Compressive stress has stress units (fo ...

. This resulted in various oroclines around the

Gulf of Bothnia The Gulf of Bothnia (; fi, Pohjanlahti; sv, Bottniska viken) is divided into the Bothnian Bay and Bothnian Sea, and it is the northernmost arm of the Baltic Sea, between Finland's west coast ( East Bothnia) and the Sweden's east coast ( We ...

Svecobaltic orogeny

Prior to the Svecobaltic orogeny proper there was period of northward-directed subduction at what is now south-central Sweden and southern Finland. The subduction lasted from 1860 to 1840 million years ago and was accompanied by

magmatic activity Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...

. Two trends in the southern Svecofennian orogen variously overlapped in time and space:

(1870 to 1840 million years ago) and continent-continent collision (1870 to 1790 million years ago).

Magmatic activity Magmatism is the emplacement of magma within and at the surface of the outer layers of a terrestrial planet, which solidifies as igneous rocks. It does so through magmatic activity or igneous activity, the production, intrusion and extrusion of ...

and metamorphism in southern Finland ended gradually after 1870 million years ago. The orogen at southern Finland with its presumed mountains and thick

collapsed under the influence of gravity and spread out. By 1850 million years ago this collapse had evolved to a dynamic of

extensional tectonics Extensional tectonics is concerned with the structures formed by, and the tectonic processes associated with, the stretching of a planetary body's crust or lithosphere. Deformation styles The types of structure and the geometries formed depend ...

. In this extensional milieu short-lived

sedimentary basin Sedimentary basins are region-scale depressions of the Earth's crust where subsidence has occurred and a thick sequence of sediments have accumulated to form a large three-dimensional body of sedimentary rock. They form when long-term subsiden ...

s formed. The Svecobaltic orogeny developed when subduction bought the Fennoscandian Craton into an oblique collision with the

. The mentioned sedimentary basins were destroyed by basin inversion 1830 million years ago. This last event of basin inversion was associated with a period of metamorphism in southern Finland that peaked about 1820 million years ago.

Nordic orogeny and later development

Two models exist regarding the origin of the Nordic orogeny: one proposes it as an Andean-type orogeny with

but no

continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains produ ...

and the other poses it might have resulted from the collision of the Fennoscandian Craton with the Amazonia continent. The Svecofennian orogen underwent a

gravitational collapse Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of gravity. Gravitational collapse is a fundamental mechanism for structure formatio ...

from 1790 to 1770 million years ago. The late magmatism following the orogeny overlaps in time with the early magmatism of the Transscandinavian Igneous Belt. This magmatism was largely the result of

anatexis Anatexis (via Latin from Greek roots meaning "to melt down") is the partial melting of rocks. Traditionally, anatexis is used specifically to discuss the partial melting of crustal rocks, while the generic term " partial melting" refers to the pa ...

forming migmatites and large

pluton In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

s. Another characteristic of the late magmatism is the apparent lack of

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks in ...

and

intermediate composition In igneous petrology, an intermediate composition refers to the chemical composition of a rock that has 5263 wt% SiO2 being an intermediate between felsic and mafic compositions. Typical intermediate rocks include andesite, dacite, and trachyan ...

s among the magmas, which are nearly all

felsic In geology, felsic is a modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted with mafic rocks, wh ...

Features of the orogen

Tectonostratigraphic units

Geologist Baltybaev (2013) have identified the following

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its ow ...

s as composing the Svecofennian orogen (parenthesis indicate location): ''Skellefteå Terrane'' ( Skellefte River Basin), ''Bothnian Terrane'' ( Västernorrland and Ostrobothnia), ''Pyhäsalmi Terrane'' (

Northern Savonia North Savo (or Northern Savonia; fi, Pohjois-Savo; sv, Norra Savolax) is a region in eastern Finland. It borders the regions of South Savo, Central Finland, North Ostrobothnia, Kainuu, and North Karelia. Kuopio is the largest city in the r ...

), ''Central Terrane'' (Central Finland), ''Western Terrane'' ( Gävleborg), ''Ladoga Terrane'' (southern Finland–Russia border) and the ''Southern Terrane'' ( Bergslagen and Southern Finland). Baltybaev further distinguishes between an ''outer zone'' in the northeast and an ''inner zone'' in the southwest. The ''inner zone'' is characterized by I-type calc-alkaline granitoids. In contrast the ''outer zone'' contains more S-type granitoids. There are differences between the metamorphosed sediments found in the two zones while the outer zone contains metagreywackes the inner zone hosts

metapelite A pelite ( Greek: ''pelos'', "clay") or metapelite is a metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone. The term was earlier used by geologists to describe a clay-rich, fine-grained clastic sediment or sedimentary roc ...

s. Rocks of the outer zone are estimated to have formed 1890–1860 million years ago and granitoids of the inner zone 1840–1790 million years ago. In addition to those two zones Baltybaev identifies a narrow ''zone of conjugation with Archean complexes'' between the ''outer zone'' and the Archean craton to the north and east. Nironen and Mänttäri (2012) uses the terms ''Central Svecofennian terrane'' and ''Southern Svecofennian terrane'' for approximately the same areas Baltybaev calls ''outer'' and ''inner zone'' respectively. The ''Oskarshamn-Jönköping belt'' is a granitoid region of the Svecofennian orogen completely surrounded by rocks of

. As the name implies the ''Oskarshamn-Jönköping belt'' runs as sliver from the vicinity of Oskarshamn northwest to the

Jönköping Jönköping (, ) is a city in southern Sweden with 112,766 inhabitants (2022). Jönköping is situated on the southern shore of Sweden's second largest lake, Vättern, in the province of Småland. The city is the seat of Jönköping Municipa ...

area. It has been proposed that the Oskarshamn-Jönköping belt continues beneath the

East European Platform East European Platform or Russian Platform is a large and flat area covered by sediments in Eastern Europe spanning from the Ural Mountains to the Tornquist Zone and from the Peri-Caspian Basin to the Barents Sea. Over geological time the platfo ...

Lithuania Lithuania (; lt, Lietuva ), officially the Republic of Lithuania ( lt, Lietuvos Respublika, links=no ), is a country in the Baltic region of Europe. It is one of three Baltic states and lies on the eastern shore of the Baltic Sea. Lithuania ...

Major faults and sutures

The boundary of the Svecofennian orogen with the Archean "Kola-Karelian orogen" to the northwest is made up by the ''Luleå-Kuopio suture zone''. The

dextral Sinistral and dextral, in some scientific fields, are the two types of chirality (" handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use differe ...

''South Finland Shear Zone'' runs across much of southern Finland in a west–east direction.

Notes

References

Cited book * {{Geology of Fennoscandia Orogenies of Europe Geology of Finland Geology of European Russia Geology of Sweden Paleoproterozoic orogenies