Petrography and Petrology of the KTB Location Schwarzwald

Abstract

The metamorphic massif of the Central Schwarzwald has been chosen as a possible site of a deep continental research drilling. Apart from the outstanding results of the geophysical and geological investigations carried out in that region, the petrographic conditions and petrological aspects known so far, cause far-reaching expectations from the materials encountered in the drilling. The target area is a typical section of the pre-Variscan metamorphic basement with pre-dominant paragneisses, orthogneisses, and various specialized intercalations. The paragneiss complex, of Proterozoic age, has been divided in several lithostratigraphic units, which can partly be correlated with certain members of the Proterozoic sequence in Bohemia, Numerous geochemical analyses of certain paragneiss sequences and their statistical evaluation are useful means for further distinctions and correlations.- A high-pressure phase of the metamorphism is clearly expressed in many eclogites and accompanying intermediate and acid (former supracrustal) rocks. Several narrow belts with mylonitic granulites are interpreted as deep-seated shear zones of a pre-Variscan tectonic event. In the Haslach area, a granulite zone seems to mark the border between a gneiss unit with HP relics and another one where those are lacking.- The problem raised by the tonalitic-trondhjemitic-granodioritic orthogneisses is whether they were intrusive (originating from the lower crust) or subautochthonous formations by anatexis of their paragneiss environment,- For the completion of the general view, some paragraphs on the metamorphic units north and south of the Central Schwarzwald are briefly discussed.KeywordsShear ZoneMagnetic AnomalyAmphibolite FaciesDuctile Shear ZoneMetamorphic UnitThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.