Department or Program



This study presents structural and textural examinations as well as bulk chemical analyses for five felsic to intermediate composition dikes from Mt. Jasper, including one previously undiscovered rhyolite dike. The analyzed samples collectively display well to poorly pronounced flow banding, ranging from under 0.25 to 4 mm in thickness. The flow banding structures exhibit a range of morphologies including straight, curved, wavy, and nonuniformly thick banding as well as several instances of sheared flow banding. Multiple samples possess rounded, irregularly shaped spherules that are exclusively confined within the darker flow bands. Many of these spherules are enclosed by white or dark mineral rims. Chemical analyses deduced a range of SiO2 contents from 54 to 84% and revealed variations in bulk chemistries observed in different areas of each of the individual samples. Structural, textural and chemical observations indicate that the flow banding in the Mt. Jasper dikes is likely to have resulted from one or more of the following processes: 1) shearinduced fragmentation and reannealing of magma in the volcanic conduit, 2) shear-induced production of fracture networks and subsequent oxide microlite nucleation, 3) mingling of two compositionally distinct magmas, or 4) flow-induced stretching of magma containing zones of varying water concentrations. Further microtextural and chemical investigation is required to reach a more specific conclusion about which of these mechanisms is responsible for the flow banding in these dikes.

Level of Access

Open Access

First Advisor

Genevieve Robert

Date of Graduation


Degree Name

Bachelor of Arts

Number of Pages


Open Access

Available to all.