A numerical approach to sill emplacement in isotropic media: Do saucer-shaped sills represent ‘natural’ intrusive tendencies in the shallow crust?

Hansen, Jógvan

doi:10.1016/j.tecto.2015.09.006

Cited by 15 publications

(27 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While these thin, mafic and intermediate to felsic sills will both subsequently undergo a phase of inflation, their final growth stage varies (e.g., Johnson and Pollard, 1973;Kavanagh et al, 2006Kavanagh et al, , 2015Currier and Marsh, 2015). For example, observations presented here indicate that mafic sills commonly transition into inclined sheets at their lateral tips (e.g., Malthe-Sørenssen et al, 2004;Thomson and Hutton, 2004;Polteau et al, 2008b;Magee et al, 2013c;Hansen, 2015). In contrast, laccoliths form through sill thickening in response to continued magma injection and overburden bending Cruden and McCaffrey, 2001;Menand, 2011), suggesting that inclined sheet intrusion at the lateral sill tips is largely inhibited .…”

Section: Influence Of Magma Rheology and The Growth Of Sill Complexesmentioning

confidence: 70%

“…16C; Thomson and Schofield, 2008;Bunger and Cruden, 2011); (3) intrusion along preexisting faults (e.g., Fig. 14A; Bedard et al, 2012;Magee et al, 2013c;McClay et al, 2013); (4) the intrusion of magma along inclined unconformity surfaces (C. McLean, personal observations); or (5) the upward deflection, along a curved trajectory, of a propagating fracture beyond the lateral tip of a sill in response to the asymmetrical emplacement of magma above the initial level of the extension fracture (Hansen, 2015). In summary, magma ascent along inclined sheets in sill complexes is likely facilitated by multiple processes, and therefore resolving the key controls on transgression is challenging.…”

Section: Inclined Sheet Formationmentioning

confidence: 99%

See 1 more Smart Citation

Lateral Magma Flow in Mafic Sill‐complexes

Magee

Muirhead

Karvelas

et al. 2016

Acta Geologica Sinica (Eng)

View full text Add to dashboard Cite

The structure of upper crustal magma plumbing systems controls the distribution of volcanism and influences tectonic processes. However, delineating the structure and volume of plumbing systems is difficult because (1) active intrusion networks cannot be directly accessed; (2) field outcrops are commonly limited; and (3) geophysical data imaging the subsurface are restricted in areal extent and resolution. This has led to models involving the vertical transfer of magma via dikes, extending from a melt source to overlying reservoirs and eruption sites, being favored in the volcanic literature. However, while there is a wealth of evidence to support the occurrence of dike-dominated systems, we synthesize field-and seismic reflection-based observations and highlight that extensive lateral magma transport (as much as 4100 km) may occur within mafic sill complexes. Most of these mafic sill complexes occur in sedimentary basins (e.g., the Karoo Basin, South Africa), although some intrude crystalline continental crust (e.g., the Yilgarn craton, Australia), and consist of interconnected sills and inclined sheets. Sill complex emplacement is largely controlled by host-rock lithology and structure and the state of stress. We argue that plumbing systems need not be dominated by dikes and that magma can be transported within widespread sill complexes, promoting the development of volcanoes that do not overlie the melt source. However, the extent to which active volcanic systems and rifted margins are underlain by sill complexes remains poorly constrained, despite important implications for elucidating magmatic processes, melt volumes, and melt sources.

show abstract

Section: Influence Of Magma Rheology and The Growth Of Sill Complexesmentioning

confidence: 70%

Section: Inclined Sheet Formationmentioning

confidence: 99%

Lateral Magma Flow in Mafic Sill‐complexes

Magee

Muirhead

Karvelas

et al. 2016

Acta Geologica Sinica (Eng)

View full text Add to dashboard Cite

show abstract

“…Vaz et al 2007). The existence of several L-Ti and H-Ti in the study area as depicted by the geochemical modelling is somehow expected considering that, the Parnaíba diabases are predominantly saucer-shaped (Porto & Pereira 2014) and that, the emplacement mechanisms of such intrusions would prevent them to spread over large areas (Hansen 2015). Different L-Ti and H-Ti suites can be discriminated by comparing trace element ratios of samples with the same degree of evolution (ie., same MgO contents).…”

Section: Geochemical Modelling Of Evolutionary Processesmentioning

confidence: 80%

The petrogenesis of tholeiitic diabases in eastern Parnaíba Basin: evidence for geochemical heterogeneities in the subcontinental lithospheric mantle in NE Brazil

et al. 2017

View full text Add to dashboard Cite

show abstract

“…In the latter case, the characteristic saucer shape, with transition from a flat to inclined sill, is typically related to asymmetry in sill‐tip stress during propagation, due to inflation‐induced bending of the overburden (Galland et al, 2009; Malthe‐Sørenssen et al, 2004). Other proposed mechanisms for saucer‐shaped sill formation include the depth‐dependent increase in Young's Modulus E (Hansen, 2015) or shear failure of the overburden (Haug et al, 2017, 2018). Analog models (Galland et al, 2009; Galland & Scheibert, 2013) and numerical simulations of sill growth (Chen et al, 2017) using isotropic host materials have demonstrated that the saucer shape is a fundamental geometry.…”

Section: Introductionmentioning

confidence: 99%

“…Axes of sill radius r and depth h are normalized to the depth of emplacement H of the initial sill, for comparison (see Bunger et al, 2008). Profiles shown are for analog experiments of (a) Galland et al (2009) and (b) Bunger et al (2008) and numerical result of (c) Hansen (2015) and Haug et al (2017). Panel (d) shows all data sets together.…”

Section: Introductionmentioning

confidence: 99%

The Roles of Elastic Properties, Magmatic Pressure, and Tectonic Stress in Saucer‐Shaped Sill Growth

Gill

Walker

2020

JGR Solid Earth

View full text Add to dashboard Cite

Near-surface igneous sills commonly exhibit saucer-like shapes, formed due to interaction with the Earth's surface once some critical sill length is reached relative to its depth. Sill geometry has been strongly linked to the host material conditions, particularly in terms of the elastic properties and shear cohesion of the host rock, operating as primary controls on sill geometry. Here we conduct dynamic numerical simulations for sill growth in the near surface, in which we vary the host rock properties, magma pressure profile internal to the sill ΔP, and the externally applied tectonic stress σ r , to consider their contributions to sill geometry. We find that elastic properties alone have little impact on sill geometry. Saucer shapes reflect the additive stress components of the magma overpressure within the sill, and the tectonic stress, controlled by the locus of the maximum energy release rate G max . Initially, G max is in-plane with the sill but deflects to~25°at a critical base length r c relative to depth, due to interaction between the sill and the free surface. Increasing σ r decreases this angle and increases r c of the sill. ΔP controls sill growth rate but has little effect on overall geometry. Host rock cohesion and elastic properties control the absolute magnitudes of σ r required to effect a change in sill geometry.Plain Language Summary Horizontal magma pathways-sills-are a crucial part of volcanic plumbing systems, acting as potential feeder conduits to volcanic eruptions, and as magma storage systems. Saucer-shaped sills, which exhibit a flat inner region and inclined outer region, are a common type of magma pathway in the shallow crust. Models for saucer-shaped sills, both as physical analog models or numerical simulations, typically underpredict the length of the inner flat region and overpredict the outer inclined region; models are typically too short and too steep. Here we use numerical simulation to investigate parameters that may control sill shape. We find that the dominant controls on sill shape are the competing effects of (1) bending of the rocks above the sill, which promotes a transition to inclined growth, typically at~25°, and (2) plate tectonic shortening, which serves to decrease the angle of incline, toward 0°when the horizontal force is high. Increasing the applied horizontal tectonic force can produce sills that are up to five times longer in the inner region, before growing as inclined sills at~5°. This matches very closely with observations of natural sills, indicating that tectonic forces are an important consideration in the growth of sills.

show abstract

A numerical approach to sill emplacement in isotropic media: Do saucer-shaped sills represent ‘natural’ intrusive tendencies in the shallow crust?

Cited by 15 publications

References 56 publications

Lateral Magma Flow in Mafic Sill‐complexes

Lateral Magma Flow in Mafic Sill‐complexes

The petrogenesis of tholeiitic diabases in eastern Parnaíba Basin: evidence for geochemical heterogeneities in the subcontinental lithospheric mantle in NE Brazil

The Roles of Elastic Properties, Magmatic Pressure, and Tectonic Stress in Saucer‐Shaped Sill Growth

Contact Info

Product

Resources

About