U-Pb Detrital Zircon Geochronological Constraints on the Depositional and Tectonic Setting of the Albemarle Sequence, North Carolina: Implications for the Neoproterozoic- Palaeozoic Evolution of Gondwana

Carolinia comprises a collection of Neoproterozoic-early Paleozoic magmatic arc and sedimentary terranes that were amalgamated and accreted to Laurentia in the early to middle Paleozoic. LA-ICP-MS U-Pb ages of more than 500 detrital zircons from the Neoproterozoic-early Paleozoic clastic sequences of Carolinia range from ca. 528 Ma (Early Cambrian) to ca. 2600 (Archean). The majority (>80%) of analyzed zircon grains are late Neoproterozoic (Ediacaran), with minor amounts of Mesoproterozoic/Paleozoic and accessory Archean grains. The overall distribution of age populations of detrital zircons is consistent with sediment derivation from the Amazonian craton and its peripheral orogenic belts on the margin of west Gondwana.

On the basis of the age of the youngest detrital zircon populations, the Uwharrie, Tillery, Cid and Yadkin formations are no older than Ediacaran. The minimum deposition ages of the Uwharrie and Cid formations are constrained by ages of contemporaneous volcanism (554 ± 15 Ma and 540 ± 1.2 Ma, respectively). Thus, the Uwharrie, Tillery, and Cid formations were deposited between ca. 554 and 528 Ma. The dominance of Ediacaran and early Paleozoic zircons in the Albemarle Group suggests an underlying local protosource for the sediments. Mesoproterozoic and older detrital grains constitute a minor component and suggest provenance from an adjacent Mesoproterozoic terrane. Collectively, Albemarle Group samples yield similar detrital zircon U-Pb age populations consistent with a common provenance for the entire group. These data illustrate that sedimentation in the Albemarle sequence is a manifestation of active tectonics and was contemporaneous with felsic magmatism. These relationships coupled with lithogeochemical and isotopic data suggest that magmatism, tectonism and deposition were broadly coeval and important regional-scale mechanisms consistent with formation in a late Neoproterozoic-early Paleozoic back-arc rift to back-arc basin tectonic setting in the Rheic Ocean.