Geology of the Precambrian Metamorphic Rocks Along South Hardscrabble Creek, Wet Mountains, Colorado

Abstract

Proterozoic metamorphic rocks exposed along South Hardscrabble Creakier typical those in the Wet Mountains on the east side of the Ilse fault, lacking the northeast trending, 1-mr (1 6 km) wavelength folds of rocks to the west They are folded isochronally implying that this IS not a stratigraphic succession, but map units can be described and analyzed Three major units were recognized 1) amphibolite, 2) birotate gneiss, and 3) granitic gneiss Manor rock types include metagabbro and sillimanite-bearing quartzite The amphibolite and metagabbro have compositions suggesting that they originated as tholeiitic basalts The birotate gneiss probably had both shale and greywacke protoliths The mineralogy, textures, and chemistry of the granitic gneisses indicate Igneous origin, probably as late tectonic granitic intrusions of crustal derivation