Xenoliths of Greyrock Mountain EarthCache
Xenoliths of Greyrock Mountain
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In the wall of pink Silver Plume Granite at this site are some dark colored chunks of rock. These are xenoliths of metamorphic parent material which were incorporated into the magma during the intrusion of the Log Cabin Batholith, about 1.4 billion years ago.
Xenoliths (from xeno meaning “foreign”, and lith meaning “rock”) are pieces of native rock that were picked up by the magma as it passed upward through the native metamorphic rock layers. Pieces of this rock broke off and became incorporated into the granite. After erosion of the parent material and uplift of the batholith, these are now visible in the exposed granite.
To log this cache, complete the following: 1.) Send me the coordinates and size of another xenolith which you have found along the trail. Include in your email the reason you feel this is a xenolith.
Please consider posting photos of yourself, or the local geology, when you log this EarthCache. Photos can be an additional rewarding part of your journey, but posting them is not a requirement for logging this EarthCache, and is strictly optional.
The above information was compiled from the following sources:
2007. Chronic H., and F. Williams. Roadside Geology of Colorado, 2nd Ed.
2004. Hopkins, R.L., and L.B. Hopkins. Hiking Colorado’s Geology
Thanks to the Roosevelt National Forest for allowing placement of this EarthCache!
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