High Sierra Topix

Bill wrote:

The aphanitic dike had a lower [or a similar] melting temperature than the granitic rock it intruded.

There you are, Hello Bill, and thanks for the explanation. That "Bowen's Reaction Series" stuff is now just a pretty vague memory. So the dike minerals- Si02, et al, stay in a viscous fluid state at temps where the existing granite remains happily hard, and so, it shoots into the cracks and forms these dikes. The 2nd rock photo was equally interesting to me, as it looked as though different minerals had formed very planar bands. I recalled some geology discussion about the relationship between gneiss and granitic rock, and wondered if I were seeing it there? [I don't mean those nice light veins, but the feint banding seen in the parent rock.]

Harlen wrote: ↑Sat Nov 16, 2019 10:54 am The 2nd rock photo was equally interesting to me, as it looked as though different minerals had formed very planar bands. I recalled some geology discussion about the relationship between gneiss and granitic rock, and wondered if I were seeing it there? [I don't mean those nice light veins, but the feint banding seen in the parent rock.]

Layers that are similar to structures in sedimentary rock form in igneous rocks now and then. J. G. Moore discusses them in his book, Exploring the Highest Sierra, published in 2000 by Stanford University Press. The generally dark color of the rock tells me it cooled at relatively higher temperatures than the dikes that cut it, leaving sharp contacts between the dikes and the host rock. Layers in a gneiss are usually not as continuous as those seen in this rock.
Here's a link to a recent article documenting the dynamic nature of magma which produces layers over the course of millions of years of cooling - https://pubs.geoscienceworld.org/gsa/ge ... eren-zones

Hi Bill, and thanks again for your input.

associated magmatic faults and folds within schlieren packages suggest that the crystal mush was deformed magmatically in a highly dynamic environment. Faults affecting both planar and multiply folded schlieren packages attest to several distinct deformation events during both formation and collapse of the crystal mush

Patterson, et al, from the above paper.

The above quote, along with the deformed nature of the Schlieren examples seen in the report's photos, make me wonder if this is what occurred in the boulder I found by Hidden Lake. Does this boulder I found appear related to the KNG- Kinney Lakes granodiorite, that they key in on in the study? It was seen at the southern end of the KNG occurrence map.

Doesn't the layering in my boulder seem too uniform, and not deformed enough to be an example of schlieren? Mightn't it just be an errant gneiss?
Anyhow, I appreciate your help. Feel free to shoot me a PM if you want to continue my geology ed.

Wandering Daisy wrote:

I bet Bearzy takes baths.

Bearzy swimming in lower Twin Lake.

I have seen your photos of Bearzy on winter trips without a coat- was that a new winter coat for him? How did his paws do on Sky Pilot Col?

You're right Nancy; a friend passed on a former dog's coat. It is open at the underside, so he'll still accumulate ice on his poor belly, but it's good for pissing- so it won't be "yellow ice" at least. A coat that is tight enough might avoid piss too, and be warmer- Russ, what do your winter hunting dogs use?