The Protogine Zone is a

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

boundary zone in western

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

. There are two slightly different definitions of the Protogine Zone. In the lithological definition it forms the limit between the

gneiss Gneiss (pronounced ) 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. This rock is formed under p ...

es of western Sweden and the relatively underformed eastern

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, 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 coo ...

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

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

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 of Sweden, provinces () of Sweden. Located in the south tip of the geographical region of Götaland, the province is roughly conterminous w ...

across

Lake Vättern A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

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 l ...

and then into

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

. The tectonic Protogine Zone has anastomosing branches and splits south of Lake Vättern into various diverging arms. The two westernmost of these arms follow the valleys of the

Nissan is a Japanese multinational Automotive industry, automobile manufacturer headquartered in Yokohama, Kanagawa, Japan. The company sells its vehicles under the ''Nissan'' and ''Infiniti'' brands, and formerly the ''Datsun'' brand, with in-house ...

and Lagan rivers. A more eastern branch is reflected in the alignment of the lakes Rusken, Rymmen and Möckeln. 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 include ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

during the same time spans as Rapakivi granites intruded more easterly domains in

Fennoscandia __NOTOC__ Fennoscandia (Finnish language, Finnish, Swedish language, Swedish and ; ), or the Fennoscandian Peninsula, is a peninsula in Europe which includes the Scandinavian Peninsula, Scandinavian and Kola Peninsula, Kola peninsulas, mainland ...

. 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 Tectonics, tectonic processes associated with, the stretching of a planetary body's Crust (geology), crust or lithosphere. Deformation styles The types of structure and the ...

perhaps being a

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

. 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