Day #65 Outcrop: Rhyolite Dikes, Homestake Open Pit

We’ve seen a streak of sedimentary deskcrops and outcrops and I’m feeling the strong urge to bring back some igneous goodness. We’ll start with a weekend of outcrops from the Black Hills. Well, not technically an outcrop today, since the exposure is not exactly naturally occurring, but hey, how often does nature make a spectacular exposure of intrusive igneous relations on her own? (Callan found a spectacular one, but that one’s a bit farther afield than I’ve had the opportunity to venture, at least to this point in my life.)

The Homestake Open Pit Mine in Lead, South Dakota beautifully exposes a lovely set of Tertiary rhyolite dikes which intruded the Precambrian metabasic rocks of the northern Black Hills, initiating a hydrothermal system that concentrated gold in sufficient quantities for humans to blast this massive hole in the ground. I’ve got both a standard photograph and a GigaPan of the view from the observation deck of the little museum perched on the edge of the pit. Zoom in on that 2.91 gigapixel Gigapan and be amazed at the detail that you can see!

Rhyolite Dikes, Homestake Open Pit (standard photo)

Rhyolite Dikes, Homestake Open Pit (GigaPan)
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