Geologica Belgica

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Simon DEPOORTER, Dominique JACQUES, Kris PIESSENS, Philippe MUCHEZ & Manuel SINTUBIN

The Mousny massive quartz occurrence – the vestige of a late-orogenic dilational jog in the High-Ardenne slate belt (Belgium)

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Abstract

Near the village of Mousny, Belgium, a peculiar massive quartz occurrence, composed of multiple large, >m³-size, bodies of milky quartz can be found at the locality known as “Les Blancs Cailloux”. Strikingly, the quartz bodies contain elongated, cleaved, host-rock fragments, still oriented parallel to the regional cleavage attitude.

A detailed petrographical, microstructural and mineralogical study of the vein quartz and a geochemical analysis of fluid inclusions has revealed that the Mousny massive quartz occurrence is genetically linked to the regionally common cleavage-parallel quartz veins. They both show a fluid evolution typical of the metamorphic fluids in the central, epizonal part of the High-Ardenne slate belt.

While the cleavage-parallel veins can be considered to result from mode I extensional fracturing, the genetically linked massive quartz occurrence is seen as being formed in a dilational jog. Within the late-orogenic context of the High-Ardenne slate belt, we favour a model in which the dilational jog is comprised within a weakly south-dipping, extensional shear zone, related to the late-orogenic extensional destabilization of the slate belt, causing a transient enhancement of the structural permeability in this low-permeability mid-crustal environment. The Mousny massive quartz occurrence may in this respect be exemplary for massive quartz occurrences throughout the High-Ardenne slate belt.

Keywords : Microthermometry, Raman microspectroscopy, Variscan orogeny, fluid inclusion, optical microscopy, cathodoluminescence, tectonic inversion, orogenic collapse

To cite this article

Simon DEPOORTER, Dominique JACQUES, Kris PIESSENS, Philippe MUCHEZ & Manuel SINTUBIN, «The Mousny massive quartz occurrence – the vestige of a late-orogenic dilational jog in the High-Ardenne slate belt (Belgium)», Geologica Belgica [En ligne], volume 17 (2014), number 3-4, 293-310 URL : http://popups.ulg.ac.be/1374-8505/index.php?id=4660.

About: Simon DEPOORTER

Geodynamics and Geofluids Research Group, Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium; now at GEOS constructive testing, Hertenstraat 30, B-3830 Wellen, Belgium

About: Dominique JACQUES

Geodynamics and Geofluids Research Group, Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium

About: Kris PIESSENS

Geological Survey of Belgium, Royal Belgian Institute of Natural Sciences, Jennerstraat 13, B-1000 Brussels, Belgium

About: Philippe MUCHEZ

Geodynamics and Geofluids Research Group, Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium

About: Manuel SINTUBIN

Geodynamics and Geofluids Research Group, Department of Earth and Environmental Sciences, KU Leuven, Celestijnenlaan 200E, B-3001 Leuven, Belgium ; corresponding author: manuel.sintubin@ees.kuleuven.be