26 June 2012
After our “pre-honeymoon” sojourn to the Canadian Rockies last summer, Lily and I returned to the U.S. via Porthill, and then drove over to a place I’ve been wanting to visit for a long time: Yaak, Montana. Yaak (or “the Yaak“) is way up in the Kootenai National Forest, in way-way-way-northwesternmost Montana. We camped out nearby, and then in the morning, we rolled into “town,” and had breakfast (“make your own waffles”) at the Dirty Shame Saloon.
If you’ve read anything by Rick Bass, you’ve doubtless heard of the Dirty Shame. It’s what they call “an institution” in this rural, wild corner of a rural, wild state. I regretted that our visit came in the morning rather than at dusk, but at least I got to visit. The proprietress was gracious and welcoming, and took our photo for the “Wall of Shame” collage of customer portraits.
We headed off on the road to Libby (site of the infamous tremolite-laden vermiculite mine) on a backroad, and on the way, we saw something that looked a lot like the “leopard rock” we had seen a month earlier on the Beartooth Highway: porphyritic, mafic rock, with some new features beyond what I showed you from the classic “leopard rock” locality.
It’s a little greener than the Cooke City “leopard rock,” but there are those same pale chunky feldspars in the fine-grained matrix…
Here, however, you can see there are also acicular phenocrysts thrown into the mix:
And not only that… but these rocks also host xenoliths:
And some of those xenoliths are vesicle-bearing:
Lastly, I noticed in places small veins or “dikelets” were present, cutting across everything else:
Mostly, the route was forest. These shots are representative of the very few outcrops we saw along the way.
I have no idea if this rock is actually the same age as the true Proterozoic “leopard rock” – but if so, it’s an indication that Yaak was part of ancestral North America during the Proterozoic, and did not have its origin as an accreted terrane like much of nearby western Idaho.