Conversion of carbonaceous material to graphite within the Greywacke Zone of the Eastern Alps |
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| Authors: | Email author" target="_blank">Gerd?RantitschEmail author Werner?Grogger Christian?Teichert Fritz?Ebner Christian?Hofer Eva-Maria?Maurer Bernhard?Schaffer Michael?Toth |
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| Institution: | (1) Department of Applied Geological Sciences and Geophysics, Montanuniversität Leoben, 8700 Leoben, Austria;(2) Research Institute for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria;(3) Institute for Physics, University of Leoben, 8700 Leoben, Austria |
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| Abstract: | Morphology and reflectance of carbonaceous material (CM) in Late Carboniferous metasediments of the eastern Greywacke Zone (Eastern Alps) indicate a mixture of vitrinite, grainy textured and lamellar shaped particles. As imaged by high-resolution atomic-force microscopy, vitrinite and the grainy textured particles show mesophase structures which can be described as facetted nanocrystals within the carbon matrix. High-resolution transmission electron microscopy has revealed two types of microtextures representing different degrees of graphitization. The first type is characterized by elongated ring-shaped microtextures, whereas the second type is characterized by graphite lamellae and polygonal flakes with long-range ordered aromatic layers. In spite of the heterogeneity of the CMs, the geographical distribution of quantitative metamorphic parameter (Raman spectra parameter, X-ray diffraction pattern, microscopic reflectance) suggests a graphitization process which is promoted by advective heat transport during post-collisional processes. In a tentative pressure-time path, Late Cretaceous thrusting results in a turbostratic ordering of the aromatic layer. Ordering to long-range ordered aromatic layers was achieved during the Late Cretaceous-Paleogene exhumation of mid-crustal rocks beneath the eastern Greywacke Zone. |
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| Keywords: | Carbonaceous material Graphitization Low-grade metamorphism Raman micro-spectroscopy X-ray diffraction Vitrinite reflectance High-resolution transmission electron microscopy High-resolution atomic-force microscopy Eastern Alps |
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