A geochronological study of the Lincolnton metadacite, a prominent unit in the slate belt along the Georgia-South Carolina border, provides indicated primary ages of 554 ± 20 m.y. (Rb-Sr) and 568 m.y. (U-Pb, zircon). On the basis of both lithological and geochronological data, the Lincolnton metadacite and associated felsic pyroclastic sequence are interpreted to be correlative with the Uwharrie Formation in the Albemarle-Denton-Asheboro area of North Carolina. On the basis of lithologic comparison alone, the Lincolnton metadacite and associated felsic pyroclastic sequence are also interpreted to be equivalent to the Persimmon Fork Formation near Columbia, South Carolina. Prominent argillite units that overlie felsic metavolcanics in all three areas are likewise considered correlative. These units include the Tillery Formation (Albemarle-Denton-Asheboro area), the Richtex Formation (Columbia, South Carolina, area), and the upper sedimentary sequence (Lincolnton, Georgia-McCormick, South Carolina, area). Available data suggest a Cambrian age for most of these units, although some of the lowermost formations could actually be of very late Precambrian age.

Abstract The Haile gold mine is located in southern Lancaster County, South Carolina, near the town of Kershaw. Gold was discovered at the site in 1827, and four periods of mining have yielded 360,000 ounces of gold. The mine is located between the past producing Ridgeway and Brewer mines that, when all are combined, constitute a significant amount of historical gold production in the southeastern United States. These mines are hosted within Neoproterozoic to lower Cambrian Carolina terrane rocks and are dominated by volcanic and epiclastic units that have experienced greenschist facies metamorphism. Saprolitic weathering is present in the near-surface portions of the deposit and is locally covered by Cretaceous-aged Coastal Plain sediments. The gold mineralization at the Haile mine is hosted within silicified meta-sediments containing fine-grained disseminated pyrite and pyrrhotite and is a replacement type-epithermal deposit. Re-Os ages from molybdenite associated with the mineralization indicate that the deposit formed shortly after major, arc-related volcanic activity. Haile currently has a measured and indicated resource of 4.03 million ounces at an average grade of 1.77 g/t Au with an additional inferred resource of 801,000 ounces at an average grade of 1.24 g/t Au. Included in the resource is a reserve of 2.02 million ounces of gold at an average grade of 2.06 g/t. Mine construction began in May 2015, and gold production is expected by the end of 2016. The construction cost is expected to be US$380 million. Ore will be extracted from eight open pits with mill extraction and the current mine life is 14 years.

Abstract Eight stops on a one-day field trip along the Savannah River corridor between Plum Branch, South Carolina, and Augusta, Georgia, review the Ediacaran–Cambrian and Pennsylvanian–Permian history of several terranes that comprise Carolinia in the eastern Piedmont. The foliation of ca. 550 Ma andesitic metatuffs of the Persimmon Fork is isoclinally folded. This event may be related to other recognized events in Carolinia at the Cambrian-Precambrian boundary or the folding of the sub–Asbill Pond angular unconformity before the intrusion of the Clouds Creek pluton. Three stops illustrate features of the Modoc zone in the eastern Piedmont. Variably mylonitized Modoc zone orthogneisses were intruded between 300 and 310 Ma. Mylonitic Modoc zone orthogneisses are parasitically folded around the northwest-vergent Kiokee antiform. Monazites from the core of the Kiokee antiform yield TIMS (thermal ionization mass spectrometry) U-Pb ages of ca. 306–308 Ma, and hornblende yields 40 Ar/ 39 Ar plateaus of ca. 288 and 296 Ma. Favorably oriented near-vertical segments of the steeply dipping to overturned limb of the Kiokee antiform are reactivated with dextral strike-slip sense and locally preserve spectacular composite planar fabric. The serpentinites at Burks Mountain include serpentinized orthopyroxene and chromite. The origin of these ultramafic rocks may have been at the base of an ophiolite or an ultramafic layered intrusion in the lower continental crust. The ca. 294 Ma Appling granite is undeformed and intrudes the trailing limb of the Kiokee antiform. The Augusta fault frames the southeastern margin of the Kiokee belt schists and gneisses. The fault is known from a single quarry exposure that places low-grade metavolcanics and epiclastic rocks in the hanging wall against footwall gneisses and schists of the Kiokee belt. The most distinctive rocks in the quarry are K-silica-metasomatized mylonites interleaved with chlorite schists. The origin of K and Group I cations is thought to be the retrogression of biotite. Furthermore this metasomatism is thought to have accompanied Triassic rifting. These metasomatic effects are heterogeneously developed in the footwall Kiokee belt gneisses, and are well known in the footwall of the Triassic border fault of the Dunbarton basin, underlying the U.S. Department of Energy (DOE) Savannah River Site. It is thought that no differential rotation of the eastern Piedmont in this area occurred after ca. 275 Ma. A final stop is made to observe the low-grade metavolcanic rocks of the Belair belt south of the Augusta fault.

Abstract Upper-plate and lower-plate asymmetric passive margin fragments are preserved within Carolinia, one of several terranes that rifted from Gondwana in the Furongian (late Cambrian) to form the Rheic Ocean. In the upper plate, 1–2 km of preserved rocks are middle Cambrian (Drumian, Ptychagnostus atavus zone) trilobite-bearing mudstones that lie above an angular unconformity and are the youngest stratified rocks in Carolinia. In the lower plate, 4–5 km of stratigraphy preserved in the Kings Mountain terrane are particularly interesting, because a 4 km thick Cambrian Series 2 clastic sedimentary section increasingly dominated by western Amazonian detritus lies above a Carolinian volcanic arc basement. Here, we describe for the first time the origin and setting of the youngest rocks in the Appalachians of wholly Gondwanan origin.

Abstract Phanerozoic reactivations of basement fault zones are documented in 5000 m of basement core recovered from beneath the updip Atlantic Coastal Plain underlying the US Department of Energy Savannah River Site (SRS) in South Carolina. These basement fault zones are adjacent to the excised Rheic Ocean suture. Meta-intrusive rocks from c. 620 and 625 Ma contain a mylonitic fabric and intrude foliated mafic metavolcanic rocks. At c. 305 Ma, granulite facies orthogneisses were thrust over amphibolite facies meta-igneous rocks in the transpressive Tinker Creek Nappe. The overturned limb of the nappe localizes the Triassic Dunbarton Basin Border Fault. The border fault acted as a conduit for fluids in the Mesozoic and Cenozoic. At c. 220 ± 5 Ma, a potassium and silica metasomatic event affected the SRS basement. A propylitic event flushed reducing fluids through rocks as young as the Santonian. The remains of a Triassic sub-basin were identified in the northwesten part of the site. A Cretaceous and younger vein paragenesis overprints the previous events. More than 30 pseudotachylytes are found in the SRS basement and are preferentially localized on metasomatized Alleghanian chloritic fractures. Pseudotachylyte post-dates mineralized fractures. The Pen Branch Fault offsets the basement–Cretaceous unconformity and is present in c. 242 m of core between PBF-7-419 m and PBF-7-660.8 m. The Pen Branch Fault cross-cuts mineralized fractures and must post-date strike-normal zeolites.

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.