Diabase

from Wikipedia, the free encyclopedia
Silurian , shaped as pillow lava diabase of the Barrande rock in Prague, Bohemian Massif , Czech Republic

Various basic rocks are referred to as diabase ( ancient Greek διαβάς diabás 'passed through', from the infinitive διαβαίνειν diabaínein 'through') .

Is traditionally called diabase one by slight metamorphosis greenish colored ( "vergrüntes"), originally basaltic , pre- Permian (mainly Paleozoic) volcanic rock meant that in Europe, particularly in Variscan can be found rock complexes and due to its coloring and greenstone called . In this sense, the name can be found in numerous older geological writings and maps. Another basic rock, also defined as Pre-Permian, is the melaphyr . Together with the diabase, which is traditionally understood, it is placed in the group of so-called paleobasalts .

In the US geological literature, a basaltic, medium-grain sub-volcanic (hypabyssal) rock is called diabase , which essentially corresponds to the dolerite according to traditional German understanding.

Wimmenauer (1985) also uses the term for a basaltic rock of sub-volcanic origin, but distinguishes the diabase from the dolerite in that the latter does not show any transformations of the original mineral stock.

The International Association of Geological Sciences (IUGS) advises against the continued use of the term diabase in the traditional German understanding and recommends that the name diabase be viewed as a synonym for dolerite ("micro gabbro "). In geological maps, therefore, found in the rock names traditionally called "diabase" declared formations now terms such Spilit , picrite basalt or Metabasalt .

Due to the long-term use in the German-speaking area, the term diabase is discussed in the following in the sense of the traditional view. With this in mind, the Diabase was voted “Rock of the Year 2017” by the Association of German Geoscientists .

Structure and mineral composition

Diabase have a dense, fine to medium-grain structure . In some varieties , larger feldspar injections can be formed, which give the rock a porphyry structure . In this case, a mixture of bulky feldspar strips ( ophitic or intersertal structure) is characteristic.

The original rocks of the diabase were originally of tholeiite - basaltic composition. The typical greenish color goes back to the anchimetamorphosis of the rock, a preliminary stage of the metamorphosis . It arises from the formation of chlorite and hornblende from augite and the conversion of parts of the feldspars into epidote . The calcium of some plagioclases is also partially converted into calcite .

Diabase has an unusually high density, which can be up to 3,000 kg / m³, and is considered to be particularly weather-resistant.

Occurrence

Pillow lava ( stone rose ) near Saalburg in Thuringia, East Thuringian Slate Mountains .

Diabase occur as effluent rocks in numerous Paleozoic rock units, especially in the Variscides of Central and Western Europe. They represent the submarine volcanism in the Paleozoic sea ​​basins , which were subsequently pushed together during the Variscan mountainous formation and incorporated into the European continental block (Baltica). In Germany they are widespread in the Devonian and Lower Carboniferous of the slate mountains, either massive, u. a. in the form of pillow lavas , or as diabase breccias and diabase tuff (e.g. the slate - shaped , so-called scarf stone ). Often associated with the diabase is intrusive dolerite in the form of passages and sticks .

In the Thuringian-Franconian-Vogtland Slate Mountains , the diabase are all Devonian in age. There they form the hilly landscapes typical of the Vogtland in particular . A geotouristic attraction is the stone rose near Saalburg , a natural monument whose current shape goes back to the typical weathering of lava pillows.

In the Rhenish Slate Mountains , the Middle and Upper Devonian diabase represent the most important volcanic phase of the Dill and Lahn basins . The diabase of the Central and Upper Devonian Sauerland are known as the main green entry . In the Lower Carboniferous , submarine pillow lavas were also produced to a greater extent with the deck diabase in the Rhenish Slate Mountains and in the Harz Mountains .

Diabase are also common in the Devonian and Carboniferous of southern England. Further European diabase occurrences are described from the Silurian region of the Prague Mulde. Other occurrences include a. in Finland, India and Turkey.

Economic importance and use

Diabase mining northwest of Ramsbeck in the Sauerland
Diabase quarry near Dörtendorf in the Thuringian Slate Mountains
"Hahnkopf" diabase quarry between Hartenrod and Wommelshausen , Lahn-Dill area
The large disused diabase quarry near Gladenbach - Rachelshausen , Lahn-Dill area

Diabase was already in the Stone Age to tools such as axes , hatchets processed, blades, drills or scrapers. Nowadays it is used in road construction, for gravestones or stone carving work and less often as polished natural stone in floor coverings and facade panels.

Economical meaning

In the Lahn and Dill areas , the diabase associated with the scarf stone and the cover diabase of the lower carbon are mined in numerous quarries. In the area on the eastern border of the former Dill district and in particular in the adjoining former Biedenkopf district ( Hessian hinterland ) in Central Hesse , large and profitable quarries were operated at the beginning of the 20th century, providing a total of 650 employees with work and bread. The Paläopikrit diabase found there, even Hinterländer greenstone called, is a very silicate-poor type of unterkarbonischen magmatism . It is not connected to the basic diabase and olivine diabase of the deck diabase by transitions and is intrusive in Devonian rocks. Its black-brown, irregularly grained weathering bark is characteristic (the color of the fresh rock is black-green). Flaming or drawing is caused by the accumulation of plagioclases (calcareous alkali feldspars ), which can be up to 54% in these areas.

Diabass quarries are also used in the Harz, Vogtland and Sauerland regions, primarily to produce gravel.

use

Diabase, as a stone, was used more often in the building industry to make columns, monuments and tombstones. Stone sculptors like to work, grind and polish sculptures out of diabase, because surface processing creates a tension between polishing and rough surfaces. Diabase can be processed relatively easily by hand. If diabase is touched with the palms of the hands, it absorbs the sebum and the so - called hand flatterers are created , which are pleasant to the touch and shine.

Sculpture Diabase by the sculptor Katharina Szelinski-Singer

Nowadays in Germany only the diabass variety Hessisch-Neugrün is processed into tombstones. Diabase can be used for crushed stone, paving stones and road construction material. Every now and then, diabase is used in construction for facade panels, floor and stair coverings. In addition to finely ground basalt, diabase is used as what is known as primary rock flour to improve garden soil.

Occasionally, diabase is also used as an aggregate for high-density concrete.

Natural stone types

A selection of diabases that were or are used as natural stone:

Web links

Commons : Diabase  - collection of images, videos and audio files

Individual evidence

  1. ^ A b Hans Murawski, Wilhelm Meyer: Geological dictionary. 12th edition. Spektrum Akademischer Verlag, 2010, ISBN 978-3-8274-1810-4 , p. 30.
  2. ↑ Martin Okrusch, Siegfried Matthes: Mineralogie - An introduction to special mineralogy, petrology and geology. 8th edition, Springer Verlag, 2010, ISBN 978-3-540-78200-1 , p. 205.
  3. ^ Wolfhardt Wimmenauer: Petrography of igneous and metamorphic rocks. Enke-Verlag, Stuttgart 1985, ISBN 3-432-94671-6 , p. 106 ff.
  4. ↑ RW Le Maitre (Eds.), A. Fahrtisen, B. Zanettin, MJ Le Bas, B. Bonin, P. Bateman, G. Bellieni, A. Dudek, S. Efermova, J. Keller, J. Lameyre, PA Sabine, R. Schmid, H. Sørensen, AR Woolley: Igneous Rocks: A Classification and Glossary of Terms. Recommendations of the International Union of Geological Sciences, Subcommission on the Systematics of Igneous Rocks. Cambridge University Press, 2002, ISBN 978-0-521-66215-4 , pp. 5 u. 72/73.
  5. ↑ Rainer Brauer, Manuel Lapp: Diabas - Rock of the Year 2017. Leaflet. Saxon State Office for Environment, Agriculture and Geology, Dresden 2017 ( online )
  6. ^ Dierk Henningsen, Gerhard Katzung: Introduction to the geology of Germany . 7th edition. Spektrum Akademischer Verlag, Munich 2006, ISBN 3-8274-1586-1 , p. 69.
  7. ↑ a b J.-D. Thews: Explanations for the geological overview map of Hessen 1: 300,000. Geologische Abhandlungen Hessen, Vol. 96. Hessisches Landesamt für Bodenforschung, Wiesbaden 1996, ISBN 3-89531-800-0 , p. 189 ff.
  8. ↑ Diabase on the website of the Geo-Dienst Dillmann, Gelsenkirchen .
  9. ^ Names partly after Friedrich Müller: Internationale Natursteinkartei (INSK). 10 vol. 3rd edition 1989, Ebner Verlag, Ulm.