4 Magmatism in the Eastern US and Beyond: A Symposium in Honor of Paul C. Ragland

Thursday, 23 March 2006
8:00 AM - 12:00 PM

VOLCANISM OF THE CAROLINA SLATE BELT IN NORTH CAROLINA

Paper number: 4-3
Program: SYMPOSIA SESSIONS
Time: 8:30 AM – 8:50 AM

Authors

Abstract

The Virgilina and Uwharrie sequences of the Carolina Slate Belt appear to have evolved in very different tectonic environments. Although volcanism in both suites occurred in the general age range of 600 Ma, the rocks produced show significant compositional and isotopic differences.

Uwharrie volcanic rocks have TDM ages several hundred million years older than eruption ages, suggesting derivation from continental lithosphere. Na/K ratios in Uwharrie rocks are in the range of rocks found in continental rifts. These combined data suggest that the Uwharrie suite formed in an embryonic rift in a microcontinent.

By contrast , Virgilina rocks have TDM values only slightly older than eruption ages and have very high Na/K ratios. These data are consistent with evolution of the Virgilina suite in a primitive (young) island arc in oceanic lithosphere.

A preliminary model for the Slate Belt is that the Uwharrie suite formed in a microcontinent rifted from western Amazonia. This microcontinent then accreted to an intra-oceanic island arc as it crossed the ocean between Amazonia and North America. This accretion completed the assembly of the Slate Belt before it collided with the eastern margin of North America.