- 1Universidade da Beira Interior, IDL-UBI, Computer Sciences, Covilhã, Portugal (jaime.almeida@segal.ubi.pt)
- 2Instituto Dom Luiz (IDL) - Universidade da Beira Interior, Covilhã, Portugal
- 3Departamento de Geologia, Faculdade de Ciências da Universidade de Lisboa, Lisbon, 1749-016, Portugal
- 4Instituto Dom Luiz (IDL) - Faculdade de Ciências da Universidade de Lisboa, Lisbon, 1749-016, Portugal
- 5School of Earth and Environmental Sciences, Cardiff University, Cardiff, CF10 3AT, UK
Title:
Insights into plume-ridge-transform fault interactions as derived from 3D numerical geodynamic modelling of the Azores Triple Junction
Authors: J. Almeida; J. Duarte; F. Rosas; R. Fernandes; R. Ramalho
The Azores archipelago is located at the centre of the Northern Atlantic Ocean and is characterized by a large bathymetric plateau bisected by the Mid Atlantic Ridge (MAR). Over the last 10 Myr, the interaction between the Azores plume, the MAR, and the Gloria Fault zone has led to a complex tectonic history, namely the transition from a R-R-T to a diffuse R-R-R triple junction. The implied tectonic stresses are presently accommodated along several right-lateral oblique extensional structures, which includes the Terceira intra-oceanic rift. To this day, a full understanding of the geodynamic mechanisms behind this change in triple junction configuration is still lacking.
With the present work, we explore how the Azores system was shaped by the complex plume-ridge-transform-fault interactions by conducting 3D viscoelastoplastic geodynamic models. Prior publications concerning this region argued that most NW-SE oriented features – such as the Terceira Rift – form due to the onset of the right-lateral motion between Eurasia and Nubia during the Early Miocene. We thus designed an initial model setup which follows plate reconstructions for Azores and implemented a complying shift from extensional to right-lateral shear tectonic conditions. We further assessed the role of the Azores plume by imposing a thermal anomaly close to the MAR to gain additional insight on the main geodynamic processes which govern this system.
Our results suggest that the primary controlling mechanism behind the formation of the Terceira Rift is the change in tectonic forcing imposed by the change in motion between Eurasia and Nubia during the Early Miocene, acting in tandem with the strain localization effects of the Azores Plateau. The shift towards a relative right-lateral motion between these plates induces a rotation of the local stress field, promoting the localization of transtensional shear along the NE edge of the plateau, closely mirroring the present-day location of the Terceira Rift.
This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through projects GEMMA (https://doi.org/10.54499/PTDC/CTA-GEO/2083/2021) and through national funds (PIDDAC) – UID/50019/2025 and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020).
How to cite: Almeida, J., Duarte, J., Rosas, F., Fernandes, R., and Ramalho, R.: Insights into plume-ridge-transform fault interactions as derived from 3D numerical geodynamic modelling of the Azores Triple Junction, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18844, https://doi.org/10.5194/egusphere-egu25-18844, 2025.
