Self accommodating shear strain

The viscosity of magma varies over many orders of magnitude, depending on, e.g., temperature, volatile content and composition (e.g., Dingwell et al., 1993; Scaillet et al., 1997), while crustal rocks exhibit a wide range of visco-elasto-plastic rheologies (e.g., Ranalli, 1995).Consequently, depending on magma viscosity and host rock rheology, the magma/host mechanical systems can exhibit distinct and/or mixed physical behaviors, which lead to (1) intrusions of significantly diverse shapes (e.g., sheets to “blobs”) and (2) contrasting deformation patterns in the host (Galland et al., 2018).The mechanics of magma transport and emplacement in the Earth's crust generally corresponds to the flow of a viscous fluid into a solid, which deforms to accommodate the incoming volume of magma.

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The mechanics of magma emplacement in the Earth's crust corresponds to the flow of a viscous fluid into a deforming solid.(C) A dyke (elastic end-member) fractures and intrudes the host rock with negligible host rock displacement, thus, the ascent rate is primarily controlled by host rock fracture strength and magma viscosity. (D) Interpreted field photograph of outcrop exposing a sheet-like sill, magmatic fingers, and the associated structures in the shale-carbonate host rock, Cuesta del Chihuido, Mendoza Province, Argentina (Spacapan et al., 2017).The outcrop shows that the sill tip is round or blunt, and that both ductile deformation of the shale layers, brittle shear faulting of thin carbonate layers and elastic bending of thick carbonate layers accommodate the emplacement and propagation of the sill.The extent to which a body is distorted when it is subjected to a deforming force, as when under stress.The distortion can involve a change both in shape and in size.

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