Upper crustal fluids in a large fault system: microstructural, trace element and oxygen isotope study on multi-phase vein quartz at the Bavarian Pfahl, SE Germany

Journal article


Publication Details

Author(s): Schaarschmidt A, Haase K, de Wall H, Bestmann M, Krumm S, Regelous M
Journal: International Journal of Earth Sciences
Publication year: 2018
ISSN: 1437-3254
Language: English


Abstract

Fault systems are zones of crustal weakness and are used as pathways for
ascending hydrothermal fluids. One impressive example is the more than
150 km long Bavarian Pfahl system at the SW boundary of the Bohemian
Massif. Dextral ductile shearing of Moldanubian basement has shaped a
several hundred meter wide zone of mylonites and ultramylonites. This
setting was reactivated under brittle conditions and infiltrated by
fluids resulting in a multi-phase quartz lode. Structural analysis using
scanning electron microscopy cathodoluminescence (SEM–CL) images has
been carried out in combination with trace element and oxygen isotope
analysis on quartz along the system. Three successive quartz phases have
been distinguished due to their structural details and trace element
contents. Cryptocrystalline quartz fabric in the first quartz phase
results from crystallization from a silica gel, whereas in phases II and
III, quartz precipitation is characterized by repeated fragmentation
and sealing, visible due to strongly varying CL intensities. The δ18O
of Bavarian Pfahl quartz decreases from 13.8‰ in the NW to 8.5‰ in the
SE, whereas quartz from the close-by-situated Wölsendorf fluorite
deposit shows δ18O between 15.9 and 18.5‰ (vs. SMOW). Flat
shale-normalized rare earth element patterns point towards an upper
crustal origin of the hydrothermal fluids. The southeastern part of the
Bavarian Pfahl is interpreted to represent a deeper crustal level with
higher mineralization temperatures (about 350 °C) compared to the rest
of the Pfahl (< 250 °C).


FAU Authors / FAU Editors

Bestmann, Michel Dr.
Krumm, Stefan Dr.
Professur für Geologie unter besonderer Berücksichtigung der Strukturgeologie [Tektonik] und Photogeologie
Lehrstuhl für Endogene Geodynamik
de Wall, Helga Prof. Dr.
Professur für Geologie unter besonderer Berücksichtigung der Strukturgeologie [Tektonik] und Photogeologie
Haase, Karsten Prof. Dr.
Lehrstuhl für Endogene Geodynamik
Regelous, Marcel PD Dr.
Geozentrum Nordbayern
Schaarschmidt, Anna
Professur für Geologie unter besonderer Berücksichtigung der Strukturgeologie [Tektonik] und Photogeologie


How to cite

APA:
Schaarschmidt, A., Haase, K., de Wall, H., Bestmann, M., Krumm, S., & Regelous, M. (2018). Upper crustal fluids in a large fault system: microstructural, trace element and oxygen isotope study on multi-phase vein quartz at the Bavarian Pfahl, SE Germany. International Journal of Earth Sciences. https://dx.doi.org/10.1007/s00531-018-1666-y

MLA:
Schaarschmidt, Anna, et al. "Upper crustal fluids in a large fault system: microstructural, trace element and oxygen isotope study on multi-phase vein quartz at the Bavarian Pfahl, SE Germany." International Journal of Earth Sciences (2018).

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Last updated on 2019-07-01 at 09:10