Structural analysis of the Kiokee belt and its framing elements: Savannah River transect
Allen J. Dennis, 2016. "Structural analysis of the Kiokee belt and its framing elements: Savannah River transect", Gold, Structures, and Landforms in Central South Carolina—Field Guides for the 2016 GSA Southeastern Section Meeting, Columbia, South Carolina, William R. Doar, III
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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 40Ar/39Ar 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.