Abstract

The results of a thermal and fluid-dynamical analysis are presented that allow geologists to estimate the critical dyke or fracture width (wc) necessary for the transport of felsic magma through the crust without control by solidification. The principal geological variables required to estimate wc are the magmatic viscosity (μ), the density and temperature contrasts (Δ and ΔT) between magma and country rock, and the height of ascent H. The results show that for typical values of μ and Δ, and for transport distances of 20 to 30 km, the critical dyke width is constrained to lie between about 2 and 20 m.