Inelastic deformation during sill and laccolith emplacement: Insights from an analytic elastoplastic model

By J. Scheibert, O. Galland, A. Hafver.

(a) Schematic drawing of the clamped plastic model. A plate of thickness h is attached to a rigid foundation and is subject to the lithostatic stress q0 =𝜌gh. An axisymmetric sill of radius a applies a (possibly heterogeneous) pressure distribution P(r) at the bottom of the plate and lifts it up. Between the tip of the sill (x = a) and the clamped region (plastic zone tip; x = b), a cohesive crack tip of size b − a defines a plastic zone. The failure of the interface along which the sill propagates is defined by a critical displacement 𝛿c . (b) Schematic diagram representing the rigid-perfectly-plastic law used within the plastic zone illustrated in Figure 2a. Plasticity is here defined by a constant stress value 𝜎Y , i.e., the yield stress of the interface between the rigid foundation and the overlying elastic plate, when the plate displacement w is between w=0 (at x=b) and w=𝛿c (at x=a). 

We present an analytical model of igneous sill and laccolith emplacement accounting for inelastic deformation at intrusion tips The size of the inelastic zone scales with the inverse of (1) the intrusion radius and (2) the square root of the magma overpressure Our model shows that the effect of the inelastic zone can be substantial for small intrusions, whereas it decreases with large intrusions We present an analytical model of igneous sill and laccolith emplacement accounting for inelastic deformation at intrusion tips The size of the inelastic zone scales with the inverse of (1) the intrusion radius and (2) the square root of the magma overpressure Our model shows that the effect of the inelastic zone can be substantial for small intrusions, whereas it decreases with large intrusions.

By J. Scheibert, O. Galland, A. Hafver.
Published Aug. 22, 2017 1:43 PM - Last modified Aug. 22, 2017 1:43 PM