U-Pb evidence for ca. 166 Ga metamorphism and deformation in the Hartville uplift, southeastern Wyoming
- Univ. of Wyoming, Laramie, WY (United States)
- Geological Survey, Denver, CO (United States)
The Hartville uplift is the southeasternmost exposure of the Precambrian Wyoming province and is situated near the proposed junction of the Cheyenne Belt, Trans Hudson, and Central Plains orogens. Consequently, it is uncertain which orogen was responsible for the apparent metamorphism and N-S trending deformation in the Hartville uplift. Field relationships combined with U-Pb data from zircon, monazite, and apatite suggest an episode of regional metamorphism and deformation ca. 1.66 Ga. Based on U-Pb zircon data, the crystallization age of a gray gneissic phase of the Rawhide Buttes granite is [ge]2.4 Ga which is consistent with Rb/Sr data from similar granites by Z. Peterman. Monazite ages from the gray gneiss are nearly concordant at 1.66 Ga, and discordant apatite data yield a Pb/Pb age of 1.60 Ga. Metapelite assemblages adjacent to the Rawhide Buttes granite record second sillimanite facies metamorphism, which other workers have shown to be of sufficient grade to either reset monazite or recrystallize it below its closure temperature. The monazite age is thus interpreted to document the timing of a metamorphic event. Apatite ages from Rawhide Buttes and two other Proterozoic intrusions in the Hartville uplift are also consistent with resetting ca. 1.66 Ga. Regional deformation near the Rawhide Buttes post-dates crystallization of 1.69 Ga zircons from a strongly boudinaged pegmatitic dike. This episode of deformation may have accompanied the regional thermal resetting of apatite and monazite ca. 1.66 Ga. This age is distinctly younger than both the Cheyenne Belt and Trans Hudson orogenies but may be correlative with the Central Plains orogen.
- OSTI ID:
- 5098333
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GEOLOGIC FORMATIONS
ISOTOPE DATING
GNEISSES
PETROGENESIS
GRANITES
WYOMING
APATITES
DEFORMATION
GEOLOGIC HISTORY
LEAD ISOTOPES
METAMORPHISM
PRECAMBRIAN ERA
URANIUM ISOTOPES
ZIRCON
ACTINIDE ISOTOPES
AGE ESTIMATION
DEVELOPED COUNTRIES
GEOLOGIC AGES
GEOLOGY
IGNEOUS ROCKS
ISOTOPES
METAMORPHIC ROCKS
MINERALS
NORTH AMERICA
PETROLOGY
PHOSPHATE MINERALS
PLUTONIC ROCKS
ROCKS
SILICATE MINERALS
USA
580000* - Geosciences