Bramscher Pluton

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The Bramscher Pluton (also Bramscher Massif ) is a hypothetical pluton made of gabbroid rock, the highest point of which is said to be below the town of Bramsche northwest of Osnabrück . Its existence has so far been supported exclusively by the results of geophysical investigations with the help of geomagnetics , gravimetry and seismics . The comparatively high temperature to which the rocks in this area were demonstrably exposed in the geological past (“high temperature diagenesis ”) is also attributed to the Bramscher Pluton. However, all geological anomalies can also be explained by an unusually deep sinking and a later rise of the rock formation in the Bramsch area. Similar phenomena in other places around Osnabrück are also explained by hypothetical plutons, each of which has its own name: Massiv von Vlotho , Massiv von Uchte , Massiv von Loccum , etc.

intrusion

According to the model of an intrusion developed in the second half of the 20th century, magma rose under the southwest Lower Saxony basin during the Cretaceous and solidified in a magma chamber that was 150 km by 50 km in size. The magma penetrated between the Mesozoic of the layers and the layers Altpaläozoikums in the earth's crust before. It rose to a height of 5 km below the earth's surface and solidified there as a laccolite . This makes it heated the overlying rock layers and underwent such a metamorphosis . The temperatures reached values ​​of around 400 ° C in the central area of ​​the uplift , which is now around 1.5 km below Bramsche, and around 250 ° C in the Vehre area (today around 40 ° C).

Coalification and uplift

The heating changed the properties and compositions of the surrounding rocks. The coal seams that occur in the upper carbon strata of the region ( Ibbenbürener Steinkohlenrevier ) were heavily coaled . Also the coals that are more recent geologically, such as the Wealden coal and other organic residues in the rocks, show a high degree of coalification compared to the Ruhr and Saar areas.

Furthermore, the layers were raised, as happened at the Piesberg , Ibbenbürener Bergplatte and Hüggel . Iron , lead , and zinc ores were formed. They were mobilized from different rock layers and precipitated hydrothermally in faults and fissures. The sandstones of the red sandstone were given a particularly high strength by the intensive pebbles of the feldspars . The Posidonia slate near Vehre was created by the action of heat from layers of oil shale .

literature

  • Geological State Office Hanover: Großblatt 59 - Haselünne-Vechta-Rheine-Osnabrück , Hanover, 1946
  • H. Bartenstein, M. Teichmüller, and R. Teichmüller: The transformation of organic matter in the roof of the Bramscher massif. Advances in the geology of Rhineland and Westphalia. Vol. 18, 1971, pp. 501-538.
  • Roland Walter et al .: Geology of Central Europe . 5., completely rework. Edition. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart 1992, ISBN 3-510-65149-9 , pp. 89 .

Individual evidence

  1. ^ Yvonne Adriasola Muñoz: The thermal history of the western Lower Saxony Basin, Germany . Dissertation RWTH Aachen, 2006, p. 122 ff . ( rwth-aachen.de [PDF; 3.3 MB ]).

Coordinates: 52 ° 26 '53.2 "  N , 7 ° 57' 44.6"  E