Chapter 10 Buoyancy-Driven Fracture and Magma Transport through the Lithosphere: Models and Experiments

Abstract

This chapter presents the results of experiments on buoyancy-driven fluid transport by fracture propagation using various fluids injected into gelatin. Fracture propagation is a mechanism by which positively buoyant magmas, generated in mantle upwellings, are transported through the lithosphere. Buoyancy-driven magma fracture has been investigated from several points of view. First, there is the quasi-static fracture model that utilizes the two-dimensional shape of a static volume of fluid embedded in an elastic solid. The second model is based on the stress-corrosion theory of materials science as applied to magma fracture; in this model, cracking is controlled by environmental factors—such as temperature, chemical-reaction kinetics, and the fluid viscosity near the crack tip—and the stress intensity is assumed to be less than the fracture toughness. The resulting crack propagation velocities vary over four orders of magnitude. The chapter discusses a new model in which fracture at the tip and closure at the tail are coupled by elastic wave propagation down the crack surface. The experimental-data-bound fracture velocities derived from this model and the predicted velocities of buoyancy-driven magma fracture in the lithosphere are consistent with velocities inferred for magmatic systems. The crack-tip fracture and the consequent production of seismic radiation from propagating dikes are consistent with this model.