Isotopic evidence for Cambrian tectonism in the crystalline southern Appalachians: The Carolinian, not the Taconian

Conference · Tue Mar 01 00:00:00 EST 1994 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6786606

Gates, A E ^[1]; Lanzirotti, A ^[2]; Glover, L III ^[3]; Mose, D ^[4]

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1. Rutgers Univ., Newark, NJ (United States). Dept. of Geology
2. State Univ. of New York, Stony Brook, NY (United States). Dept. of Earth and Space Sciences
3. Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences
4. George Mason Univ., Fairfax, VA (United States). Dept. of Chemistry

Newly developed geochronologic techniques that use U/Pb in staurolite yield concordant ages of 534 [+-] 5 Ma for amphibolite facies metamorphism of Evington Group metapelites within the northern extension of the Inner Piedmont belt, Altavista, VA. These ages probably represent the timing of slaurolite growth in these rocks and thus the timing of metamorphism. This result is supported by Rb/Sr whole rock ages on spaced samples of Evington Group metapelites of uniform composition which yield a 546 Ma age. The Evington Group rocks form the western side of the suture zone with the volcanic arc deposits of the Carolina terrane. The suturing of Carolina terrane with Laurentia (Evington Group) caused the tectonism recorded by these ages. The new ages are consistent with U/Pb zircon ages of 525 Ma from the youngest dated volcanic rocks within the Carolina terrane and the 510 Ma U/Pb zircon age on the Melrose Granite which intrudes the suture zone and contains foliated and metamorphosed xenoliths of both Carolina terrane and Evington Group rocks. The tectonism in Altavista reflects westward directed nappe emplacement during the peak of a major orogeny and continues through the entire Inner Piedmont belt to the south. The new ages indicate that this tectonism is not Taconian as previously proposed but is 75 Ma older.

• OSTI ID: 6786606
• Report Number(s): CONF-9404221-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 26:4; Conference: 43. annual meeting of the Southeastern Section of the Geological Society of America, Blacksburg, VA (United States), 7-8 Apr 1994; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
AMPHIBOLITES
ISOTOPE DATING
PETROGENESIS
GEOLOGIC FORMATIONS
TECTONICS
NORTH CAROLINA
SOUTH CAROLINA
GEOCHEMISTRY
ISOTOPE RATIO
LEAD ISOTOPES
URANIUM ISOTOPES
ACTINIDE ISOTOPES
AGE ESTIMATION
CHEMISTRY
DEVELOPED COUNTRIES
GEOLOGY
ISOTOPES
METAMORPHIC ROCKS
NORTH AMERICA
PETROLOGY
ROCKS
USA
580000* - Geosciences