Magmatism and Rifting in Oceanic Intraplate Environments: The Evolution of the Azores Plateau

• Main Author: Romer, René
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2021
• Subjects: ddc:550; North Atlantic
• Online Access: https://opus4.kobv.de/opus4-fau/frontdoor/index/index/docId/16966; https://nbn-resolving.org/urn:nbn:de:bvb:29-opus4-169661; https://opus4.kobv.de/opus4-fau/files/16966/RomerRHWDissertation.pdf

The interaction between intraplate volcanism and extensional tectonic movements yields important insights into the initial formation and evolution of oceanic and continental magmatic systems. Intraplate magmatic systems commonly form by the emplacement of a melting anomaly from the upper or lower mantle at the base of the lithosphere, leading to the formation of ocean islands, flood basalt provinces or the initiation of continental breakup. In some cases, mantle melting anomalies interact with diverging plate margins or lead to the formation of rift systems. In these environments the composition and distribution of magmas is significantly influenced by regional tectonic stresses. Lithospheric extension significantly affects the melt pathways in the crust as well as the morphology of volcanoes. In the oceanic environment the lithosphere is thin and less complex compared to the continents which allows to better understand the principal processes of melt transport through the lithosphere and volcano formation. There is, however, little information on how extension in the lithosphere affects the formation and evolution of oceanic intraplate volcanoes. The Azores archipelago in the central North Atlantic Ocean formed by a mantle melting anomaly in the vicinity of a plate triple junction. The young volcanic activity (<2 Ma) in the Azores is dominated by volcanism along rift structures, i.e. the ultraslow diverging Terceira Rift and other subparallel rift structures. This makes this region an ideal target location to improve our understanding of interacting magmatic and tectonic processes and their role in the initial formation and evolution of oceanic volcanoes and oceanic rift systems. This thesis focuses on a) the causes and processes of initial formation of oceanic intraplate volcanoes; b) the spatial and temporal geochemical and structural variability that occurs during the evolution of oceanic volcanic system that are significantly influenced by slow extensional tectonic stresses; and c) the characteristics of ...