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Carbon isotopes in pelites of the Precambrian Uncompahgre Formation, Needle Mountains, Colorado

July 1, 1969

Carbon isotopic ratios and weight percentages of carbon were measured in 15 samples of slate, phyllite, and schist of the approximately 1500- to 1600-m.y.-old Uncompahgre Formation of the Needle Mountains, southwestern Colorado. Rocks with less than 1 percent total carbon, all of which is reduced, have δC13 values of −23 to −28 per mil, whereas those with 1 to 6.4 percent carbon have δC13 from −29 to −31 per mil. In general, the slates and phyllites contain more carbon and isotopically lighter carbon than do the schists of higher metamorphic rank. Increasing loss of C12-enriched methane with increasing intensity of metamorphism is suggested to account for these differences.

Publication Year 1969
Title Carbon isotopes in pelites of the Precambrian Uncompahgre Formation, Needle Mountains, Colorado
DOI 10.1130/0016-7606(1969)80[1403:CIIPOT]2.0.CO;2
Authors Fred Barker, Irving Friedman
Publication Type Article
Publication Subtype Journal Article
Series Title Geological Society of America Bulletin
Index ID 70223870
Record Source USGS Publications Warehouse
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