An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

Poppe, Sam; Holohan, Eoghan P.; Galland, Olivier; Buls, Nico; Gompel, Gert Van; Keelson, Benyameen; Tournigand, Pierre-Yves; Brancart, Joost; Hollis, David; Nila, Alex; Kervyn, Matthieu

doi:10.3389/feart.2019.00062

Cited by 50 publications

(79 citation statements)

References 87 publications

(158 reference statements)

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“…Our study supports recent physical model experiments by demonstrating dome-shaped forced folds can form, and be expressed at the free surface, above both dyke-and sill-like sheet intrusions (Fig. 2) (e.g., Galland, 2012a;Guldstrand et al, 2017;Poppe et al, 2019;Schmiedel et al, 2017). We also show the forced folds developed above the cone sheets and saucer-shaped sills widen and decrease in amplitude upwards ( Figs 2B, C, and 3), consistent with previous suggestions that contemporaneous compaction of the overburden can partly accommodate strain (e.g., Hansen and Cartwright, 2006;Jackson et al, 2013;Morgan et al, 2008;Pollard and Johnson, 1973;Withjack et al, 1990); i.e.…”

Section: Forced Fold Developmentsupporting

confidence: 91%

“…These observations indicate the intruded magma volume was not purely accommodated by elastic bending, supporting an array of previous physical modelling studies that have shown the translation of magma emplacement into surface deformation is complex (e.g., Galland, 2012a;Galland et al, 2019;Poppe et al, 2019;Schmiedel et al, 2019). Here, we discuss how our results contribute to our understanding of specific relationships between magma emplacement style, host rock behaviour during deformation, and intrusion geometry.…”

supporting

confidence: 86%

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Control of heterogeneous, layered successions on shallow-level magma emplacement and host rock deformation

Magee¹,

Montanari²,

Corti³

2019

Preprint

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Host rock deformation in active volcanic settings can signal and be used to constrain magma emplacement. Yet it is difficult to evaluate the accuracy of intrusion parameters derived from inversion of deformation signals because we cannot test estimates by directly accessing the magma body. Physical modelling is thus critical to understanding how intrusion translates into host rock deformation, particularly surface uplift and/or subsidence, because we can use transparent materials or excavate models to view the actual intrusion geometry. However, few physical models have investigated how a heterogeneous, layered host material impacts magma emplacement, despite evidence suggesting the presence of weak layers can control intrusion style and geometry. We conduct several models that simulate emplacement of a felsic magma at ~6 km depth within a granular (sand) host rock; in two of our models we incorporate two, thin, weak microbead layers into the layered host material. We show that intrusion solely within the granular material is primarily accommodated by lateral contraction (compaction and folding) of the host material, resulting in a dyke-like intrusion that erupted. When the microbead layers were present, a cone sheet and saucer-shaped sill preferentially formed, without erupting, accommodated by forced folding. Furthermore, we demonstrate that surface deformation does not simply reflect the complexity of the intrusion geometry or internal host material deformation. Overall, our results indicate that physical models should further explore the role of host material heterogeneity on magma emplacement.

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Section: Forced Fold Developmentsupporting

confidence: 91%

supporting

confidence: 86%

Control of heterogeneous, layered successions on shallow-level magma emplacement and host rock deformation

Magee¹,

Montanari²,

Corti³

2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Evidence is found in blunt and finger-shaped geometries of fossilized intrusion fronts and shear-mode fracturing of host rock in natural outcrops (e.g., Delcamp et al, 2014;Galland et al, 2019;Magee, Muirhead, et al, 2018;Spacapan et al, 2017) or even ductile fluidization of often organic-rich host rocks (Kjøll et al, 2019;Schofield et al, 2012). Shear-mode deformation has been documented also in laboratory experiments of analog magma intrusion that use granular materials as host medium (Abdelmalak et al, 2012;Bertelsen et al, 2018;Guldstrand et al, 2017;Mathieu et al, 2008;Poppe et al, 2019) and in recent numerical models (Haug et al, 2017;Souche et al, 2019;Vachon & Hieronymus, 2017).…”

Section: Magma Emplacement Modelsmentioning

confidence: 92%

Structural and Geochemical Interactions Between Magma and Sedimentary Host Rock: The Hovedøya Case, Oslo Rift, Norway

Poppe

Galland

Winter

et al. 2020

Geochem Geophys Geosyst

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Two end‐member conceptual models are used to describe deformation of the Earth's crust induced by magma intrusion. “Mode I” fracturing assumes tensile or opening‐mode, elastic deformation, while “Mode II” fracturing assumes plastic shear‐mode deformation around a viscous indenter. Field observations of both mechanisms exist, but it remains unclear which mechanism dominates in which conditions. We describe intrusion geometries, host rock deformation, and geochemical magma‐host rock interactions around 53 exceptionally preserved, tephrite‐basanite Permian dike segments of 0.5‐ to 30‐cm thickness. These thin dikes, that is, “dikelets,” intruded Late‐Ordovician carbonate‐rich sedimentary rocks on Hovedøya island, Oslo Rift, Norway. Dikelets emplaced in preexisting fractures dominantly created cavities ahead of their narrow, tapering tips and are associated with bent host rock, broken bridges, and stepped segmented geometries. Other tips are blunt with dense brittle fracturing around them. Also, cross‐sectional intrusion segment opening profiles deviate from parabola‐shaped profiles typical for elastic media. The observations demonstrate that dominant opening‐mode host rock deformation can coexist with shear‐mode deformation locally. Alignment of most dikelet segments along the dominant host rock fracture directions highlights the control of local structural orientations on magma emplacement. Analysis of bulk major and trace element compositions, in situ micro‐XRF sample analysis and carbon and oxygen stable isotope compositions, suggests that thermochemical interactions between magma and the carbonate‐rich host rock produced a low‐viscosity mixture of magma, pore water, and gas. We propose that such low‐viscosity hybrid fluid may assist in the intrusion of magma in sedimentary rocks by filling the cavity ahead of propagating sheet intrusion tips.

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“…Our modelled tips are blunt, which is less efficient at concentrating stress. Tip bluntness also has the effect of offsetting the maximum stress concentration from in--plane, to the positions of maximum tip curvature, i.e., the corners of a rectangular tip (Poppe et al, 2019); as noted though, such non--physical stresses are not resolved at the square corners of our modelled sill tips (Gill and Walker, in review). In a dike model, tip blunting could result in different deformation styles above shallow intrusions; extensional grabens above bladed dikes (Mastin and Pollard, 1988), versus fold--and--thrust systems above rectangular tips (Hardy, 2016).…”

Section: Methodsmentioning

confidence: 95%

Tectonic stress controls saucer-shaped sill geometry

Walker¹,

Gill²

2019

Preprint

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Saucer-shaped sills are common in sedimentary basins worldwide. The saucer shape relates to asymmetric stress distributions at the sill-tip during intrusion caused by bending of the overburden. Most saucer-shaped sill models are conducted without tectonic stress. Model results are poorly correlated with natural sills in that: (1) modelled saucers are much steeper than natural sills; and (2) natural sill inclines are convex in profile whereas modelled saucer inclines are concave. We present finite element simulation of initially horizontal sill emplacement for a range of tectonic stress (sigma_r) conditions, from mild horizontal tension (sigma_r<0), to horizontal compression (0

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An Inside Perspective on Magma Intrusion: Quantifying 3D Displacement and Strain in Laboratory Experiments by Dynamic X-Ray Computed Tomography

Cited by 50 publications

References 87 publications

Control of heterogeneous, layered successions on shallow-level magma emplacement and host rock deformation

Control of heterogeneous, layered successions on shallow-level magma emplacement and host rock deformation

Structural and Geochemical Interactions Between Magma and Sedimentary Host Rock: The Hovedøya Case, Oslo Rift, Norway

Tectonic stress controls saucer-shaped sill geometry

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