Electronically conducting brittle-ductile shear zones in the crystalline basement of Rittsteig (Bohemian Massif,Germany): Evidence from self potential and hole-to-surface electrical measurements |
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Authors: | Jürgen?Bigalke Andreas?Junge Email author" target="_blank">Gernold?ZulaufEmail author |
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Institution: | (1) Institut für Meteorologie und Geophysik, Universität Frankfurt am Main, Feldbergstr. 47, 60323 Frankfurt am Main, Germany;(2) Institut für Geologie und Mineralogie, Universität Erlangen-Nürnberg, Schloßgarten 5, 91054 Erlangen, Germany |
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Abstract: | Crustal-scale shear zones may act as prominent electrical conductors given that sufficient amounts of graphite or fluids are present. There are several graphite-enriched shear zones within the 583-m-deep Rittsteig drilling (Bavaria, Germany), two of which are of major importance. One shear zone cuts through Moldanubian biotite-muscovite schists at 320 m depth. The other shear zone separates Teplá-Barrandian amphibolites from Moldanubian biotite-muscovite schists at 460 m depth. To detect these shear zones adjacent to the drilling, the self-potential method and the non-linear impedance spectroscopy have been applied. From the new data, obtained from hole-to-surface and surface measurements, we conclude that (1) graphite is pervasively distributed within the Rittsteig shear zones resulting in powerful electronic conductors, (2) the graphite-bearing shear zones are dipping moderately towards the S, and (3) the shear zone drilled at 320 m depth extends to the Earths surface where it has been detected ca. 400 m to the N of the drilling. As the graphite-bearing shear zones of both the Rittsteig drilling and the German Continental Deep Drilling (KTB) developed in the brittle-ductile regime of quartzofeldspathic rocks, we argue that the brittle-ductile boundary layer may act as a significant graphite attractor in the continental crust. |
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Keywords: | Self-potential measurements Non-linear impedance spectroskopy Brittle-ductile shear tones Graphite Rittsteig drill hole Central Bohemian shear zone |
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