Butte, MT Field Work
I returned to Butte this summer to collect samples for a new Butte project focused on an early alteration event. Turns out, all of the samples we had here in Eugene were from the wrong areas of the deposit for what we were interested in! This trip was also challenging in that we were searching for rocks which had been partially "biotitized". That is, we were looking for samples in which anhedral clusters of hornblende and biotite in the Butte Granite co-existed with microcrystalline biotite+quartz+anhydrite pseudomorphs of hornblende, all of which have been partially chloritized by subsequent, unrelated alteration events. Definitely a fun exercise in excruciating hand lens work.
Accompanying me were two other students: Ellen Olsen, a PhD candidate in my lab who studies calcite precipitation, and Molly Pickerel, an undergraduate beginning a senior thesis on Butte this year.
We spent several days sampling and mapping in the mine itself, a bit of time doing more of the same around Rampart Mountain just outside of the mine, and also did some classic "sketchy highway outcrop" geology. We then spent several days sampling from the Geological Research Library (GRL) housed at Montana Tech, and ended our trip by accompanying Dr. Chris Gammons and his group to the Little Gem Mine to collect amethysts and ogle GIANT quartz crystals.