| Mt. Lindsey |
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Geology (Mt. Lindsey)Title: Mt. Lindsey Geology Entered by: rockdoc53 Added: 10/19/2010, Last Updated: 10/19/2010 Sources: Johnson, B.R. and Bruce, R.M., 1991, Reconnaissance geologic map of parts of the Twin Peaks and Blanca Peak Quadrangles, Alamosa, Costilla, and Huerfano counties, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF-2169 Blanca, Ellingwood,Little Bear and Mt. Lindsey are part of a granitic batholith formed over 1.7 billion years ago (Early Proterozoic). The top of Mt. Lindsey is the upper plate of a thrust composed predominantly of Early Proterozoic tonalite gneiss and metagabbro with a few Proterozoic mafic dikes intruding the tonalite gneiss. Metagabbro is a dark gray to very dark green, metamorphosed igneous rock of gabbroic composition, typically with phenocrysts of hornblende and plagioclase. Tonalite gneiss is a white to light gray green metamorphosed igneous rock of tonalite composition, typically 60% plagioclase, 30% quartz 2% potassium feldspar, and 8% percent mafic minerals altered to epidote, chlorite and muscovite. The lower plate, exposed on the north side of Lindsey is composed of Early Proterozoic hornblende gneiss. |
