Department of Earth Sciences, University of Cambridge, UK

The microstructural record of fluid dynamics in igneous intrusions

Perhaps surprisingly, there is still controversy over whether or not bodies of magma intruded into the Earth's crust undergo convection, with some advocating vigorous convection while others suggest that convection is weak and short-lived, or absent entirely. From a detailed microstructural study of a range of ancient, fully solidified, tabular intrusions of basaltic magma, we argue that it is possible to determine whether crystallization took place predominantly in solidification fronts (i.e. the magma was essentially crystal-free and therefore non-convecting or only very weakly convecting) or whether crystals grew suspended in a vigorously convecting magma.