Abstract

Granitic gneisses from the Inner Piedmont belt of northwest North Carolina have Rb-Sr whole-rock ages of 427 ± 9 m.y., 460 ± 9 m.y. and possibly 534 m.y. Initial 87Sr/86Sr ratios for these rocks are approximately 0.704. Rb-Sr data for granitic gneisses from the Inner Piedmont belt of southwestern South Carolina and adjacent Georgia suggest a whole-rock age of approximately 423 m.y. and an initial 87Sr/ 86Sr ratio of 0.7069. These ages are tentatively interpreted as times of igneous crystallization. Together with previously published results, these data suggest that 460 to 420 m.y. ago was a time of significant igneous activity in the Inner Piedmont of North and South Carolina; igneous activity also occurred 545 to 525 and 350 to 335 m.y. ago.

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