St Andrews Research Repository

St Andrews University Home
View Item 
  •   St Andrews Research Repository
  • Earth & Environmental Sciences and Geography & Sustainable Development (Schools of)
  • School of Earth & Environmental Sciences
  • Earth & Environmental Sciences Theses
  • View Item
  •   St Andrews Research Repository
  • Earth & Environmental Sciences and Geography & Sustainable Development (Schools of)
  • School of Earth & Environmental Sciences
  • Earth & Environmental Sciences Theses
  • View Item
  •   St Andrews Research Repository
  • Earth & Environmental Sciences and Geography & Sustainable Development (Schools of)
  • School of Earth & Environmental Sciences
  • Earth & Environmental Sciences Theses
  • View Item
  • Login
JavaScript is disabled for your browser. Some features of this site may not work without it.

The interplay between deformation and magma transport in southeast Iceland

Thumbnail
View/Open
Thesis-Vincent-Twomey-complete-version.pdf (12.37Mb)
Thesis-Vincent-Twomey-complete-version.docx (53.58Mb)
Date
06/2023
Author
Twomey, Vincent
Supervisor
McCarthy, William
Raub, Timothy David
Funder
University of St Andrews
NERC Isotope Geosciences Laboratories (NIGL)
Geological Society
CASP
Metadata
Show full item record
Altmetrics Handle Statistics
Altmetrics DOI Statistics
Abstract
Igneous intrusions are of fundamental importance to society's ability to source critical metals, predict major natural hazards and, understand how Earth’s crust evolved. However, the factors that control how magma transits through Earth’s crust and the variables that determine if magma will arrest during the process of ascent or erupt at the surface remains a challenge. This study investigates the interface between key tectonic, host rock and magma parameters to advance our understanding of how these variables influence magma transport processes in sub-volcanic plumbing systems. Specifically, this thesis assesses the interplay of magma flow dynamics and i) deformation structures associated with the ambient extensional stress regime of SE Iceland and ii) host rock deformation processes caused by the process of laccolith intrusion. The first part of the thesis investigates how surface and overburden deformation (forced folds, faults, and fractures) correlate with the mechanism of magma emplacement. In a case study on the Sandfell Laccoith, eastern Iceland, this chapter presents new palaeomagnetic data and a modified fold test to assess the formation of a forced fold. The results show that the formation of the forced fold occurred in two distinct processes that required the temporal break between the initial injection of magma and the later inflation of the laccolith. An evolutionary model is proposed whereby the continuous forceful emplacement of magma involved initial lateral propagation of a sill-like body preferentially towards the SSW resulting in forced folding with a relatively simple geometry. Continuous addition of magma at the base of the laccolith resulted in subsequent ‘bulldozing’ of magma underlying the cooled, viscously stalled initial magma. Magma that was subsequently injected into the laccolith caused inflation facilitated by further displacement of host rock and the formation of a prominent forced fold that is today observed in outcrop. This study demonstrates the utility of a new modified fold test that provides an effective means to track the style and location of transient shallow-level magma movement associated with forced folding. Through detailed structural mapping, ²⁰⁶Pb/²³⁸U zircon dating and, anisotropy of magnetic susceptibility (AMS) analyses, the second data chapter of this thesis investigates the relationship between pre-existing fault/fracture networks and magma flow processes in the Reyðarártindur intrusion in southeast Iceland is investigated. The intrusion is interpreted as a sub-volcanic laccolith where magma propagated laterally along a NE-SW primary axis over a timeframe of 10⁴ – 10⁵ years. Pre-existing NNE-striking, faults/fractures in the host rock accommodated intrusive sheets which themselves facilitated upward and outward evacuation of magma from the laccolith. This study elucidates on how the process of magma transport is influenced by pre-existing fault/fracture networks caused by ambient extensional tectonic regimes and shows that lateral offset of eruptive edifices can be controlled by these fracture networks. The final data chapter uses fracture modelling to provide a revised regional tectonic framework for southeast Iceland. Fracture analysis of fault and joint populations identified within the structural aureole of the Reyðarártindur intrusion and across the southeast Iceland to identify different generations of Riedel shear structures that in turn define a sinistral Riedel shear system. The inferred Riedel shear system is interpreted to have formed within a Neogene WSW-ENE trending transfer zone that linked at least two rift segments. This investigation posits a new interpretation of the contemporaneous stress regime for southeast Iceland and discusses how the associated deformation influenced the transport and storage of magma. The works of this thesis highlight that investigating the interplay between magma movement and host-rock properties aids in our understanding of magma transport in sub-volcanic systems.
DOI
https://doi.org/10.17630/sta/318
Type
Thesis, PhD Doctor of Philosophy
Collections
  • Earth & Environmental Sciences Theses
URI
http://hdl.handle.net/10023/27086

Items in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.

Advanced Search

Browse

All of RepositoryCommunities & CollectionsBy Issue DateNamesTitlesSubjectsClassificationTypeFunderThis CollectionBy Issue DateNamesTitlesSubjectsClassificationTypeFunder

My Account

Login

Open Access

To find out how you can benefit from open access to research, see our library web pages and Open Access blog. For open access help contact: openaccess@st-andrews.ac.uk.

Accessibility

Read our Accessibility statement.

How to submit research papers

The full text of research papers can be submitted to the repository via Pure, the University's research information system. For help see our guide: How to deposit in Pure.

Electronic thesis deposit

Help with deposit.

Repository help

For repository help contact: Digital-Repository@st-andrews.ac.uk.

Give Feedback

Cookie policy

This site may use cookies. Please see Terms and Conditions.

Usage statistics

COUNTER-compliant statistics on downloads from the repository are available from the IRUS-UK Service. Contact us for information.

© University of St Andrews Library

University of St Andrews is a charity registered in Scotland, No SC013532.

  • Facebook
  • Twitter