Syn-Emplacement Fracturing in the Sandfell Laccolith, Eastern Iceland—Implications for Rhyolite Intrusion Growth and Volcanic Hazards

Tobias Mattsson,Bjarne S G Almqvist,Erika Ronchin,Steffi Burchardt

doi:10.3389/feart.2018.00005

Tobias Mattsson, Bjarne S G Almqvist + Show 2 more

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https://doi.org/10.3389/feart.2018.00005

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Abstract

Felsic magma commonly pools within shallow mushroom-shaped magmatic intrusions, so-called laccoliths or cryptodomes, which can cause both explosive eruptions and collapse of the volcanic edifice. D ...

Highlights

Deformation related to laccolith emplacement has generally been considered to be focused in the host rock, and the host-rock properties are assumed to control laccolith growth (e.g., Pollard and Johnson, 1973; Jackson and Pollard, 1988; Kerr and Pollard, 1998; Bunger and Cruden, 2011)
In order to understand the interplay between emplacement and deformation of intruding magma in laccoliths and cryptodomes, we investigate magma flow, rheological changes, and deformation in the Sandfell laccolith using field observations, measurements of flow indicators, microstructural analysis, anisotropy of magnetic susceptibility (AMS), Finite Element Method (FEM) modeling and a 3D structural model
Magmatic and magnetic fabrics show that the magma flowed in a single intrusive event from a central area beneath the main dome-shaped body toward and parallel to the contacts

Summary

Introduction

Deformation related to laccolith emplacement has generally been considered to be focused in the host rock, and the host-rock properties are assumed to control laccolith growth (e.g., Pollard and Johnson, 1973; Jackson and Pollard, 1988; Kerr and Pollard, 1998; Bunger and Cruden, 2011). Cryptodomes and laccoliths are sub-surface, dome-shaped magma intrusions that uplift and deform their host rocks (Gilbert, 1877; Minakami et al, 1951; Lipman et al, 1981). While a laccolith may form down to depths of ∼3–4 km in the crust, the intrusion can be called a cryptodome if it intrudes a volcanic edifice or close to the surface (cf Gilbert, 1877; Minakami et al, 1951; Pollard and Johnson, 1973; Corry, 1988; Roni et al, 2014). The geological record and geochronology of exposed laccoliths display incremental growth histories ranging over thousands of years (e.g., Michel et al, 2008)

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