EGU2020-5893, updated on 02 Jan 2023
EGU General Assembly 2020
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Tracking the Magmatic Flow in a Dyke-Sill Hybrid System using a Multi-Method Approach (AMS, SPO, X-ray micro-CT) for Petrofabrics Characterization (Lessines, Belgium)

Antoine Triantafyllou1,2, Jean-Marc Baele3, Hervé Diot4,5, Veerle Cnudde6,7, Redouane Meftah6, Sara Vandycke8, and Koen Van Noten9
Antoine Triantafyllou et al.
  • 1University of Arizona, Department of Geosciences, Tucson, United States of America (
  • 2Department of Geology, University of Liège, Sart Tilman, Liège, Belgium
  • 3Department of Geology and Applied Geology, Université de Mons, 20, Place du Parc, B-7000, Belgium
  • 4Université de La Rochelle, av. M. Crépeau, 17042 La Rochelle Cedex 1, France
  • 5Laboratoire de Planétologie et Géodynamique - Nantes (LPGN), UFR Sciences et Techniques, Université de Nantes, UMR-CNRS 6112, 2, Rue de la Houssinière, BP92208, 44322 Nantes Cedex 3, France
  • 6PProGRess-UGCT, Department of Geology, Ghent University, Krijgslaan 281 S8, B-9000 Ghent, Belgium
  • 7Environmental Hydrogeology group, Department of Earth Sciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, The Netherlands
  • 8University of Mons, UMONS, Mining Geology Engineering, 20 place du Parc, 7000 Mons
  • 9Royal Observatory of Belgium, Avenue Circulaire 3, B1180 Brussels, Belgium

Understanding how magmas are transported and collected within the crust is crucial for constraining the dynamic of shallow plumbing volcanic systems and associated hydrothermal activity. This study focuses on the Lessines dioritic intrusion exposed in the SW margin of the Brabant Massif in Belgium. The kilometric subvolcanic body was emplaced around 419 Ma and is thought to result from the emplacement of multiple sills which intruded a lithostratigraphic discontinuity within Upper Ordovician sedimentary units. Our study aims to constrain how magmatic flow is recorded through different fabrics, how this flow varies across the solidified magmatic intrusion and how primary fabrics can be affected by subsequent hydrothermal overprint.

The petrofabric of 40 oriented diorite samples was investigated with a multi-methods approach: (i) Anisotropy of Magnetic Susceptibility (AMS) along with K-temperature curves determined using low field KLY-4S Kappabridge susceptibilimeter (at LIENS lab, University of La Rochelle, France), (ii) Shape Preferred Orientations (SPO) of melanocratic phenocrysts (pseudomorphosed amphibole and biotite) as well as leucocratic phenocrysts (quartz and sericitized felspars s.l.) determined by the Intercepts method applied on optical scans of three adjacent cut faces of each sample, (iii) X-ray micro-CT scanning of five selected samples using the HECTOR device at UGCT lab (Ghent University, Belgium).

AMS and melanocratic fabrics SPO are mainly marked by prolate shaped ellipsoids. Both subsets show similar and homogeneous orientation of their structures through the studied area, with E-W striking foliations dipping 70° to the North to subvertical. Leucocratic petrofabric SPO shows more heterogeneous distribution with a similar E-W to N120-striking foliations but generally subhorizontal to low dipping structures (< 30°). This discrepancy is thought to be due to differential record of the subvolcanic phenocrysts during the ultimate emplacement and solidification of the Lessines magmatic body. These results combined to field observations (e.g., enclave orientations, columnar joints, borehole logs) suggest that the Lessines intrusion is a complex dyke-sill hybrid system, made of a main subvertical dyke-like structure that fed lateral sills bodies.

How to cite: Triantafyllou, A., Baele, J.-M., Diot, H., Cnudde, V., Meftah, R., Vandycke, S., and Van Noten, K.: Tracking the Magmatic Flow in a Dyke-Sill Hybrid System using a Multi-Method Approach (AMS, SPO, X-ray micro-CT) for Petrofabrics Characterization (Lessines, Belgium), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5893,, 2020.