Trans-crustal magma storage in contrasting tectonic settings

• Main Author: Geiger, Harri
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Uppsala universitet, Mineralogi, petrologi och tektonik 2019
• Subjects: magma plumbing systems; thermobarometry; oxygen isotope analysis; shallow arc storage systems; Geochemistry; Geokemi; Iceland
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-383081

Magmatic plumbing systems comprise magma chambers, sheet intrusions, and conduits which link the Earth’s deep interior with the Earth’s surface. As such, they are the structural framework of magma transport and storage that is governed by complex physical and chemical processes in magma reservoirs and through the interaction of magma bodies with surrounding crustal rocks over timescales from hours to millions of years. These geological processes, in turn, play a vital role in controlling eruptive behaviour and the magnitude of associated volcanic eruptions that impact the environment as well as human society. Our understanding of the nature and location of magmatic processes and plumbing system architecture remains, however, fragmentary. This lack of knowledge can partly be attributed to limits regarding the spatial resolution of geophysical methods and partly to geochemical uncertainties and errors in associated models. Ongoing advances in analytical techniques increase spatial, temporal, and chemical resolution, hence enabling us to gather more detailed knowledge on the structure and dynamics of magmatic systems, especially for individual volcanoes, but also in respect to the long-term evolution of magmatic provinces and ultimately the Earth as a whole. This process-oriented thesis examines fossil and active magmatic plumbing systems in Iceland, Indonesia, Cameroon, and the Canary Islands by applying a combination of traditional and state-of-the-art petrological and geochemical methods, mineral(-melt) thermobarometric modelling, and isotopic analytical techniques. The results add valuable insights to the growing body of evidence for multi-tiered plumbing systems in a number of volcano-tectonic settings and underline the importance of shallow-level magma storage and its influence on magma evolution and hazardous volcanic eruptions.