Magnetic fabric and inferred flow direction of dikes, conesheets and sill swarms, Isle of Skye, Scotland

We have measured the AMS of 16 dikes, 35 conesheets and three sills associated with the Cuillin Hills magmatic center of the Isle of Skye in the Inner Hebrides of Scotland and of nine dikes located in the regional dike swarm of Skye. Sixty-three intrusives, totalling 734 samples, were studied to determine the plumbing of the Skye volcanic system. Low-field susceptibility versus temperature (k-T) identified three different mineral phases in the area, namely Ti-rich magnetite, pyrrhotite and titanomaghemite. The petrofabrics of the 63 intrusives yielded coherent how azimuths regardless of their time of emplacement. Three main types of magnetic fabric, (A-C) were found. Fabric Type A (plane K-max-K-int parallel to the dike plane) represents the magma-flow direction within the intrusives and is the dominant fabric (55% of all the intrusives) within the Cuillin Hills magmatic center and its regional dike swarm. The K-max inclinations show that 55% of the intrusives were fed by horizontal to sub-horizontal (AMS inclination of the K-max axis is equal or less than 30 degrees) magma fluxes and the rest of them were fed by inclined to vertical fluxes. Horizontal magma flow means lateral magma injection inside fractures and becomes more probable as the source is located further away. (C) 2001 Elsevier Science B.V. All rights reserved.