Neoproterozoic Magmatism in the Suwannee Terrane: Implications for Terrane Correlation


Heatherington, A.L., Mueller, P.M., and Nutman, A., in Nance, R.D. and Thompson, M., eds., Avalonian and related peri-Gondwanan terranes of the circum-North Atlantic, GSA Special Paper 304, p. 257-268, 1996

Abstract


The Suwannee terrane in northeastern Florida contains a group of calc-alkaline volcanic rocks (basaltic andesites to rhyolites) with elemental and isotopic signatures indicative of eruption within a continental arc environment. U-Pb zircon geochronology indicates a crystallization age of 552 ± 8 Ma for a dacite from this sequence, equivalent to crystallization ages of 551 Ma determined for samples of Osceola granite in central Florida, but younger than a 625 ± 2 Ma age determined for a granodiorite in the northwestern Suwannee terrane (southern Alabama). Suwannee terrane magmatism is generally coeval with magmatism in the Avalon and Carolina terranes as well as with Neoproterozoic orogenic events in West Africa and northern South America. Sm-Nd depleted mantle model ages for Suwannee terrane volcanic rocks range from 1040 to 1580 Ma with initial epsilon Nd values of +1.1 to -4.1, suggesting the magmas were derived from lithosphere of similar composition to that of the Grenville orogenic belt, although evidence also exists for Archean basement within an adjacent portion of the Suwannee terrane to the south.


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