|Rugged terrain in the upper Del Puerto Canyon just beyond the Tesla-Ortigalita fault (on the right near the people)|
|Volcanic rocks in Del Puerto Canyon. These are either pillow basalts or highly jointed rocks.|
An ophiolite sequence is a unique series of rocks that are usually understood to represent a cross-section of oceanic crust. The top of an ophiolite is composed of pillow lavas, lumpy chunks of basalt that form as molten rock encounters cold ocean water (see some forming in this short video). Those might be some pillow basalts in the picture above, but I've never been able to get close enough to confirm it. It could also be highly jointed volcanic rocks.
There is a prominent dike in the canyon, but it is not actually part of the ophiolite. The rugged ridge is composed almost entirely of quartz. It probably formed millions of years after the others as hot hydrothermal fluids flowed through cracks and fractures. It's been investigated for gold mineralization, but I don't think anyone has found any ores worth mining (not that they wouldn't try; it's still under claim).
|Quartz vein and gabbro outcrops in Del Puerto Canyon|
|Highly jointed gabbro and diorite in Del Puerto, rocks of the lowest part of the oceanic crust|
|Diorite in Del Puerto Canyon|
And that's what we'll do in the next post!
|Gabbro near the quartz vein in Del Puerto Canyon|