Tectonic implications from U-Pb dating of detrital zircons from the early Proterozoic terrane of the Central Rocky Mountains

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6697952

Aleinikoff, J N; Reed, Jr, J C; Pallister, J S

Detrital zircons from four metasedimentary rocks were analyzed to determine the age of detritus deposited during formation of the Early Proterozoic Central Rocky Mountains (CRM) accreted-arc terrane. The Medicine Peak Quartzite, a unit within the Snowy Pass Supergroup interpreted as a shelf sequence on the southern edge of the Wyoming Archean craton, contains four distinct morphologic populations of zircon that form a discordia indicating a provenance age of 2721 +/- 30 Ma. A metagraywacke from Big Thompson Canyon, northern Colorado, contains detrital zircons with /sup 207/Pb//sup 206/Pb ages between approx. = 1850 and 2000 Ma. These are the oldest known zircons in the CRM. A quartzite from Coal Creek Canyon, north-central Colorado, contains clear, round zircons whose /sup 207/Pb//sup 206/Pb ages suggest a provenance of approx. = 1800 Ma. A quartzite from San Cristobal Canyon, Taos Range, northern New Mexico contains two populations of zircon: (1) dark pink and round, with a /sup 207/Pb//sup 206/Pb age of 1775 Ma; and (2) light pink and euhedral, with a /sup 207/Pb//sup 206/Pb age of 1713 Ma--consistent with field relations. These results suggest that while sediments at the edge of the Wyoming Province craton were derived from the adjacent Archean rocks, detritus deposited onto the newly forming CRM terrane contained zircons at most only about 250 million years older than the Early Proterozoic sedimentation. No obvious isotopic evidence exists for an Archean component in the CRM. Possible sources for the 1800-2000-Ma detrital zircons are the Trans-Hudson and Penokean orogens of north-central North America.

• Research Organization: Geological Survey, Denver, CO (USA)
• OSTI ID: 6697952
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
ACTINIDE ISOTOPES
AGE ESTIMATION
COLORADO
FEDERAL REGION VIII
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
ISOTOPE DATING
ISOTOPES
LEAD ISOTOPES
METAMORPHIC ROCKS
MINERALOGY
MINERALS
MOUNTAINS
NORTH AMERICA
OXYGEN COMPOUNDS
PETROGENESIS
QUARTZITES
ROCKS
ROCKY MOUNTAINS
SANDSTONES
SEDIMENTARY ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TECTONICS
TRANSITION ELEMENT COMPOUNDS
URANIUM ISOTOPES
USA
WYOMING
ZIRCON
ZIRCONIUM COMPOUNDS
ZIRCONIUM SILICATES