Intrusion of Magmatic Bodies Into the Continental Crust: 3‐D Numerical Models

Abstract

Magma intrusion is a major material transfer process in the Earth's continental crust. Yet the mechanical behavior of the intruding magma and its host are a matter of debate. In this study we present a series of numerical thermomechanical simulations on magma emplacement in 3‐D. Our results demonstrate the response of the continental crust to magma intrusion. We observe change in intrusion geometries between dikes, cone sheets, sills, plutons, ponds, funnels, finger‐shaped and stock‐like intrusions, and injection time. The rheology and temperature of the host are the main controlling factors in the transition between these different modes of intrusion. Viscous deformation in the warm and deep crust favors host rock displacement and plutons at the crust‐mantle boundary forming deep‐seated plutons or magma ponds in the lower to middle crust. Brittle deformation in the cool and shallow crust induces cone‐shaped fractures in the host rock and enables emplacement of finger‐ or stock‐like intrusions at shallow or intermediate depth. Here the passage of magmatic and hydrothermal fluids from the intrusion through the fracture pattern may result in the formation of ore deposits. A combination of viscous and brittle deformation forms funnel‐shaped intrusions in the middle crust. Intrusion of low‐density magma may more over result in T‐shaped intrusions in cross section with magma sheets at the surface.

The Magmatic Architecture of Continental Flood Basalts I: Observations From the Deccan Traps

“…Similarly, the higher density of intrusive mafic bodies, especially mafic and ultra‐mafic cumulates, would naturally lead to a signal in the gravity field as well as the change in seismic velocity (Richards et al., 2013; Ridley & Richards, 2010). We note that the high density of the mafic and ultramafic intrusions can lead to post‐emplacement deformation and downward crustal flow and potentially crustal delamination if the surrounding crust has sufficiently low viscosity (Gorczyk & Vogt, 2018; Roman & Jaupart, 2016, 2017). However, the presence of the upper crustal Bushveld complex (Eales & Cawthorn, 1996) and the lower crustal Seiland Igneous Province (R. Larsen et al., 2018) suggests that this process does not completely remove the crustal intrusives.…”

“…We note that the common presence of a thick (∼5–15 km) underplated layer does not necessarily equate to a single magma body of equivalent size. Instead, frequent mafic intrusions(sills) at lower crustal depths along with visco‐elastic deformation of the cumulate bodies can also lead to the formation of a large seismic underplate layer (Galland et al., 2018; Gorczyk & Vogt, 2018; Roman & Jaupart, 2016, 2017; J. D. White et al., 2009). We have observational support for this hypothesis from an exhumed lower crustal LIP section ‐ the Seiland Igneous Province (SIP, R. Larsen et al., 2018, and references therein).…”

Overburden deformation induced by dyke-fed conical sandstone intrusions: insights from numerical experiments

“…Such a design satisfies the generally acknowledged model, in which a relatively thin, vertical dyke acts as the fluid migration pathway and also the feeder of sands for conical sandstone intrusions Cartwright et al, 2008). This model has been adapted for several analogue and numerical modelling studies of sandstone and igneous intrusions (Mathieu et al, 2008;Galland et al, 2009;Bureau et al, 2014;Gorczyk and Vogt, 2018).…”

Intrusion Induced Global Warming Preceding Continental Flood Basalt Volcanism

“…Morgan and Chen 66 were the first to suggest that temperature was critical in controlling the depth of magma lenses at mid-ocean ridges. A recent three-dimensional numerical modeling study of magma intrusion into the continental crust indicates that rheology and temperature of the host rocks are the key controls of how magma is emplaced 67 . Parsons et al 68 first suggested that at large rheology contrasts where lower viscosity ductile layers are adjacent to a higher viscosity elastic layer, the least principal stress can be rotated vertically due to horizontal dike opening.…”