Thin section analysis to determine magma flow directions in a silicic dike at Summer Coon volcano

A significant number of people throughout the world live in areas with active volcanism, creating a geologic hazard to contend with. Stratovolcanoes pose a unique threat to nearby populations due
to their generally more explosive nature. Because dikes are volcanic plumbing systems responsible for transporting magma, studying the extinct Oligocene age stratovolcano, Summer Coon, provided meaningful data in understanding how dike systems propagate and how magma migrated as it approached the surface to erupt. A part of the San Juan Volcanic Complex in Southern Colorado, erosion and uplift has exposed the radial dike system at the surface where it can be studied. Previous work has been done on magma flow directions of basaltic/andesitic dikes of Summer Coon, but further work was needed for longer silicic dikes to recreate magma flow directions at the time of dike emplacement. Samples were taken from twelve locations along “Dike A” both at the center and margins of the dike. These samples were then made into thin sections, scanned into Photoshop and edited for size requirements. Using ImageJ, the thin sections were edited further to identify and isolate the minerals that showed shear. Various parameters were documented for each thin section using ImageJ and compiled into an excel document. Finally, statistical analysis was done to produce the resultant vector angle that represents the dominant direction of flow specific to each sample taken and to find the R-value.