This is my guess for Silver Fox's current edition of her occasional game, Where In The West.However, note the word 'guess.' There are some important features I simply cannot get into the right perspective, so I'm not positive. The GE Image would be an enlargement of the 2nd and 3rd peaks descending toward the valley floor from the right in SF's photo.
The geology in this area is so varied, I'm not sure where to start. There is a metamorphic complex that I think dates back to late Paleozoic(?), which is intruded by some Mesozoic plutons (see this post). During the Cenezoic, there were two major episodes of volcanism. First was the Miocene Steens Mountain basalt (correlative to the CRB, but smaller in scale, and more southern vent/fissure locations). Later came the Pliocene McDermitt Caldera silicic volcanics. The eponymous caldera is some distance from this location, I'm thinking 40-50 miles to the ENE, but there are large volumes of tuff, both sedimentary and welded, and rhyolite flows associated with this episode in the area. One of the few places in the US that has gem-quality opal is Virgin Valley, maybe 10 miles west (as the crow flies, not as the road drives) from the GoogleEarth image location. Many of the gemmy opals are a replacement of wood buried in tuffaceous sediment, which gives added beauty with the wood grain. Wood that has been replaced with common opal is pretty abundant and easy to find, and quite beautiful even without the opalesence. Virigin Valley also happens to be my favoritest camping area evar.
Finally, since the McDermitt volcanics, basin and range spreading has ripped the area apart, allowing some relatively minor basaltic volcanism. There is also some mineralization, the age of which I don't know- given the complex history of the area, my initial supposition would be mutliple episodes. There are/have been claims for gold, copper and molybdenum that I know of. There are many, many abandoned mines in the area, and last I knew, one medium-sized one in operation. The latter was after moly, but was picking up some chalcopyrite as frosting, in a large quartz vein. It was actually on the road across the valley from 140 to that mine that I first guessed this photo might have been shot.
That's my story, and I'm sticking with it. But if I'm right, I'll feel pushed to do a bigger spread on this absolutely wonderful area. Also if I'm right, Silver, where the dickens were you standing?
GSA Fresno: One More Day
1 day ago