The Protogine Zone is a

geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Eart ...

boundary zone in western Sweden. There are two slightly different definitions of the Protogine Zone. In the lithological definition it forms the limit between the

gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures a ...

es of western Sweden and the relatively underformed eastern

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...

s. As such it makes up the limit of deformation and

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 ...

attributed to the

Sveconorwegian orogeny The Sveconorwegian orogeny was an orogenic system active 1140 to 960 million years ago and currently exposed as the Sveconorwegian orogenic belt in southwestern Sweden and southern Norway. In Norway the orogenic belt is exposed southeast of the f ...

. In the tectonic definition it is a zone of strong deformation that follows roughly the same course as the lithological Protogine Zone. In the two definitions of the Protogine Zone it runs from

Scania Scania, also known by its native name of Skåne (, ), is the southernmost of the historical provinces (''landskap'') of Sweden. Located in the south tip of the geographical region of Götaland, the province is roughly conterminous with Skå ...

across

Lake Vättern A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much larger ...

into the upper course of

Klarälven Klarälven ("The clear river" in Swedish) is a river flowing through Norway and Sweden. Together with Göta älv, which it is called as the river has passed through the lake Vänern, thus regarded as an entity, Göta älv—Klarälven is the lon ...

and then into

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

. The tectonic Protogine Zone has

anastomosing An anastomosis (, plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Such a connection may be norma ...

branches and splits south of Lake Vättern into various diverging arms. The two westernmost of these arms follow the valleys of the Nissan and Lagan rivers. A more eastern branch is reflected in the alignment of the lakes Rusken, Rymmen and

Möckeln Möckeln is a lake in Karlskoga and Degerfors Municipalities in Örebro County, Sweden. Except for the settlements surrounding the lake, Degernäs Manor is situated at the southernmost tip of the lake and Valåsen Manor just north of the ...

. The origin of the Protogine Zone has been traced to the

Mesoproterozoic The Mesoproterozoic Era is a geologic era that occurred from . The Mesoproterozoic was the first era of Earth's history for which a fairly definitive geological record survives. Continents existed during the preceding era (the Paleoproterozoic ...

when it was a zone of weakness in the crust. About 1575–1562 Ma ago the Progine Zone was intruded by

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 includ ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...

during the same time spans as

Rapakivi granite Rapakivi granite is a hornblende-biotite granite containing large round crystals of orthoclase each with a rim of oligoclase (a variety of plagioclase). The name has come to be used most frequently as a textural term where it implies plagioclase r ...

intruded Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form '' intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: March ...

more easterly domains in

Fennoscandia __NOTOC__ Fennoscandia ( Finnish, Swedish and no, Fennoskandia, nocat=1; russian: Фенноскандия, Fennoskandiya) or the Fennoscandian Peninsula is the geographical peninsula in Europe, which includes the Scandinavian and Kola penins ...

. Later 1224–1215 and ca. 1204 Ma ago the progine zone was subject to

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 ...

perhaps being a

back-arc basin A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most ...

. The Protogine Zone obtained its final configuration during the Sveconorwegian orogeny 1130–950 Ma ago.

References

{{Geology of Fennoscandia Geography of Halland County Geography of Jönköping County Geography of Kronoberg County Geography of Skåne County Geography of Värmland County Geography of Västra Götaland County Geology of Norway Geology of Sweden Neoproterozoic geology Neoproterozoic Europe Mesoproterozoic geology Mesoproterozoic Europe