Doesn't sound so picky to me, to distinguish between sedimentary/metamorphic sedimentary and granitic. Especially in a skarn formation, which will tend to collect a lot of water at the granitic/metamorphic contact zone, which appears to be the case at Pine Creek. ("skarns found at and near the contacts between a septum of Paleozoic metasedimentary rocks and a mid-Cretaceous quartz monzonite pluton"). Most of the Sierra (Including the Whitney trail area) is not like this, but is truly granitic and a lot less porous than your mine experience suggests. Sure there are cracks and fissures, but the suggestion of "underground lakes and rivers" can be misleading to those who may visualize these as massive bodies of pure water, like regular rivers and lakes only in big caves. Even areas that are more sponge like, these aquifers are basically saturated rock, or very solid rock with small discrete fissures and cracks, more like cracked pottery than either a sponge or a lake. I would say that the truly granitic nature of the Sierra means that the vast majority of the water is on or near the surface, especially at the higher elevation such as at SB23, and that the groundwater emerges if at all for the most part at much lower elevations, not locally.
In other words, deep source springs (maybe OC?) are pretty rare, and most springs we find, are very shallow and local.
In any event as for SB23, the fact that it can freeze in a hard frost indicates that it does not originate very far below the surface, where temperatures would be a pretty steady mid fifties, but on or just under the surface, where soil temps pretty much go up and down with air temps.
