On the anatomy and structural control of a dyke swarm that fed caldera-forming ignimbrite eruptions

0574886 - GLÚ 2024 RIV GB eng J - Journal Article
Tomek, Filip - Olšanská, I. - Trubač, J. - Černý, Jan - Rejšek, Jan - Ackerman, Lukáš
On the anatomy and structural control of a dyke swarm that fed caldera-forming ignimbrite eruptions.
Journal of the Geological Society. Roč. 180, č. 5 (2023), č. článku jgs2022-119. ISSN 0016-7649. E-ISSN 2041-479X
R&D Projects: GA ČR(CZ) GJ19-02177Y
Institutional support: RVO:67985831
Keywords : Anisotropy of Magnetic Susceptibility * Ignimbrite Caldera * Pyroclastic Density Current * Volcano Feeder Dyke * Volcano Tectonics
OECD category: Geology
Impact factor: 2.7, year: 2022
Method of publishing: Limited access
https://www.lyellcollection.org/doi/10.1144/jgs2022-119

The evolution of eruptive vents related to calderas is not fully understood. We focus on a structural, rock-magnetic and geochemical investigation of a 314 Ma rhyolite dyke swarm associated with the late-orogenic Altenberg–Teplice Caldera, Bohemian Massif, eastern Variscan belt. The whole-rock major element, trace element and Nd–Pb isotope geochemistry along with the published U–Pb zircon geochronology link the extra-caldera dyke swarm with intra-caldera ignimbrites. The magnetic fabrics determined using the anisotropy of magnetic susceptibility are interpreted to record a continuum from magma ascent to emplacement and eruption during sinistral shearing. The latter evidences an interplay with regional tectonics associated with the activity of crustal-scale shear zones. The sinistral kinematics and strike of the dyke swarm, the elongation of caldera intrusive units, and the kinematics of major caldera faults are consistent with the dextral Riedel shear system, where the dykes correspond to antithetic R’ or X shears. Such a kinematic configuration implies that the maximum and minimum principal stresses were oriented roughly north–south and east–west, respectively. The relation between the stress field and the caldera elongation and orientation is not typical. We suggest that a pre-existing mutually perpendicular set of cross-cutting structural lineaments largely controlled the magma chamber and caldera formation.
Permanent Link: https://hdl.handle.net/11104/0344938