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Abstract

The central Piedmont of South Carolina includes two terranes derived from Neoproterozoic peri-Gondwanan arcs and one that preserves the Cambrian Series 2–Series 3 Carolinian Rheic rift-drift sequence. These are the Charlotte, Silverstreet and Kings Mountain terranes. The central Piedmont shear zone juxtaposes each of these terranes against the Late Silurian Cat Square paragneiss terrane. The Kings Mountain terrane is composed of meta-epiclastic rocks with distinctive metaconglomerate horizons, manganiferous formation, meta-sandstones, and dolomitic marbles. One of the lower metaconglomerate horizons yields detrital zircons of latest Middle Cambrian age. This stratigraphy is interpreted to record the Rheic rift-drift sequence on the trailing edge of an Ediacaran-Cambrian arc terrane as it pulled away from the Amazonian craton in Middle Cambrian–Furongian time. The Charlotte terrane records magmatic activity from before 579 ± 4 until ∼535 ± 4 Ma. Mafic-ultramafic zoned intrusive complexes intruded mafic-ultramafic volcanic piles. Ultramafic dikes cut the volcanic rocks and are interpreted as feeders to stratigraphically higher levels of volcanism. These mafic to ultramafic rocks record arc rifting resulting from subduction of a spreading ridge or bathymetric high. These rocks were metamorphosed to amphibolite facies at about the time of the Cambrian–Precambrian transition. The Silverstreet terrane preserves relict medium temperature eclogites and high-pressure granulites in the lower plate (Charlotte terrane) of an arc-arc collision. Relict high-pressure assemblages record 1.4 GPa, 650–730 °C conditions. High-pressure mineralogy and textures are best preserved in the cores of boudins derived from dikes with Ti-V ratios of 20–50 (i.e., MORB). High-pressure metamorphism may have occurred in Ediacaran-Cambrian time, and must have occurred prior to the intrusion of the 414 ± 8 Ma Newberry granite. The Cat Square basin contains detrital zircons as young as 430 Ma, accepted detritus from both Laurentia and Carolinia, and so is interpreted as a successor basin. The Cat Square terrane underwent peak (upper amphibolite-granulite) metamorphic conditions at the time of the Devonian–Mississippian transition while it was at the latitude of the New York Promontory. The peri-Laurentian-Carolinian suture is either buried under the Blue Ridge Piedmont thrust sheet or was thrust up and eroded away. The central Piedmont shear zone is a younger feature, no older than Visean.

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