T208 Emplacement of Upper Crustal Magmatic Intrusions: Field Studies of Laccoliths, Sills, and Subvolcanic Plugs (Posters)

Tuesday, 21 October 2014
9:00 AM - 6:30 PM
Exhibition Hall C

3-D SHAPE PREFERRED ORIENTATION OF 16 SAMPLES ACROSS MT. HILLERS DIKE CONSISTENT WITH GREATER MAGMA FLOW IN THE CENTER

Paper number: T208-7
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The program Intercepts 2003 (Launeau) was used to conduct shape fabric analysis across the dike. 16 samples collected across 8m wide dike were cubed giving three perpendicular faces on each sample which were then photographed. Samples showed no obvious macroscopic fabric. Using Image J photos were contrasted using constant threshold in order to show large plagioclase phenocrysts. Particles were then analyzed and masked to show only phenocrysts larger than 5000 pixels^2. 2-D images were combined using Intercepts 2003 to produce 3-D ellipsoids at the shape preferred orientations of the plagioclase crystals.

Data reveals that the strength of the SPO (long to short axis ratio) is high at the margins, drops off near the margins, and increases to a maximum in the middle of the dike. Initial fabric orientation reveals that at the margins the fabric is parallel to the dike margins and rotates to become sub-perpendicular towards the center. The initial 3-D results are consistent with greater magma flow in the center of the dike.