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  • Marisa Acosta

Butte Mining and Mineral Symposium 2018


My first day in Butte was gorgeous and clear. The next few days were less so.

I've just returned from another trip to my field area, Butte, America. I went to give a talk on a portion of my research on quartz vein formation, and also ended up meeting an awesome community of Montana geoscientists and rockhounds.


After two days of talks, there was a field trip to the Cable Mine, a skarn gold deposit. Unfortunately, it was very snowy, which made the rocks a bit hard to see.

The Atlantic Cable Lode Gold deposit (Cable Mine, Deer Lodge, MT) is a skarn deposit created by the intrusion of a granodiorite into the marmorized Upper Cambrian Hasmark dolostone. Mineralization occurs as veins in a shear zone with replacement-type mineralization proximal to the fracture network.


Absolutely stunning zones of coarsened calcite crystals in outcrop.

Brecciation of the dolostone from the shearing event.

A scenic, dolomitic, outcrop.

We visited a dump pile to look for ore specimens.

The group did find some nice pyrite-chalcopyrite (-limonite?) specimens though! I grabbed a couple to maybe make a polished section of sometime. It'd be interesting to figure out what made this intricate texture.



References

Holser, W. T. (1950). Metamorphism and associated mineralization in the Philipsburg region, Montana. Geological Society of America Bulletin, 61(10), 1053-1090.

University of Oregon

Department of Earth Sciences

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