U-Pb zircon and Sm-Nd whole-rock ages of the plutonic rocks of the Crossnore Complex in the southern Appalachian Blue Ridge: Implications for the timing of Late Proterozoic rifting

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5770666

Su, Qi; Fullagar, P D; Goldberg, S A ^[1]; Martin, M W ^[2]

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1. Univ. of North Carolina, Chapel Hill, NC (United States). Dept. of Geology
2. Univ. of Kansas, Lawrence, KS (United States). Dept. of Geology

The Crossnore Complex, an anorogenic magmatic suite associated with Late Proterozoic rifting of Laurentia, includes Beech, Crossnore, Lansing and Warrensville plutons located in the Blue Ridge of NC and TN. These granitic plutons occur as discrete intrusive bodies within Precambrian basement. Four handpicked, euhedral, prismatic and inclusion-free zircon fractions from the Beech pluton are nearly concordant and lie on a discordia with an upper intercept age of 745 Ma and a lower intercept near 0 Ma. Sm-Nd data for whole-rock samples from different locations in the Beech pluton produce an isochron that yields an age of 755 Ma, consistent with its U-Pb zircon age. Euhedral zircon fractions from the Lansing pluton are discordant. Four unabraded fractions plus one abraded fraction lie on a Pb-loss trajectory and yield an upper intercept age of 739 Ma. Two abraded fractions and two unabraded fractions from Warrensville pluton lie on a discordia with an upper intercept age of 752 Ma. Zircon U-Pb data from the Crossnore pluton indicate complications associated with both inherited-Pb and post-crystallization Pb-loss. The most concordant fraction is only 0.4% discordant with a Pb-207/Pb-206 age of 758 Ma. Four abraded fractions define a discordia with a lower intercept age of 754 Ma, which is interpreted as the crystallization age of the Crossnore pluton. These data indicate that Late Proterozoic granitic magmatism in Blue Ridge of NC and TN occurred during the interval 740--760 Ma. The 740--760 Ma. ages from Crossnore-type plutons are older than Roberson River Suite in the Central Appalachians, suggesting magma emplacement at various stages of Iapetus rifting and possibly diachronous initial rifting.

• OSTI ID: 5770666
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ACTINIDES
AGE ESTIMATION
APPALACHIAN MOUNTAINS
DEVELOPED COUNTRIES
ELEMENTS
GEOLOGIC AGES
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
IGNEOUS ROCKS
ISOTOPE DATING
LEAD
MAGMATISM
METALS
MINERALS
MOUNTAINS
NEODYMIUM
NORTH AMERICA
NORTH CAROLINA
PLATE TECTONICS
PLUTONIC ROCKS
PRECAMBRIAN ERA
RARE EARTHS
RIFT ZONES
ROCKS
SAMARIUM
SILICATE MINERALS
TECTONICS
TENNESSEE
URANIUM
USA
ZIRCON