CONSTRAINTS ON ASSEMBLY OF THE CAROLINA COMPOSITE TERRANE IN THE SOUTHERN APPALACHIAN PIEDMONT: ROLE OF ECLOGITE-HIGH-P GRANULITE FACIES ROCKS IN CENTRAL SOUTH CAROLINA

Relict in situ eclogites and hi-P granulites indicate a terrane boundary internal to the composite Carolina (C) terrane ("Carolina zone") and collisional orogenesis. Preserved hi-P granulites (cpx-plag symplectites) can be reconstituted to yield omphacite (Xjd=0.30). Best preservation occurs in mafic boudins within felsic gneisses near the C slate belt-Charlotte (Ch) belt boundary, south and west of Newberry, SC. Extensive tracts of amphibolite facies rocks (e.g., Parr Shoals; mapped gnt amphibolites) are interpreted to have undergone +/- complete retrogression during the P-T-t path: 660°C/>12 kb; 760-795°C/ 6-10 kb; 700°C/ 6 kb. Rapid uplift is indicated by the preservation of good zoning in gnts and disequilibrium assemblages. Rapid uplift would suggest active denudational faulting, but most ductile recent motion on sz’s at the slate belt-Ch belt boundary is dextral strike-slip.

While the terranes on either side of the boundary are similar there are distinct differences: Ch terrane comprises Neoprot. arc rocks that are generally more mafic, more plutonic, and were metamorphosed (ca. 544 Ma) to upper greenschist to amphibolite facies. The oldest dated plutons were intruded between 579±4 Ma and 571±16 Ma (U/Pb z). A distinctive characteristic of the Ch terrane is the presence of meta- mafic-ultramafic zoned intrusive complexes along its western margin. C slate terrane comprises at least two distinct volcanic and epiclastic sequences: 1) the Virgilina sequence, and Pen Branch & Deep Rock Metaigneous Complexes, with xlln ages between 620-630 Ma, and 2) the Uwharrie Fm-Albemarle Gp, Persimmon Fork Fm-Richtex Fm-Emory Fm and Lincolnton metadacite all at about 550 Ma.

In central SC an angular unconformity is preserved beneath the trilobite-bearing Middle Cambrian Asbill Pond Fm. The unconformity and cleavage of rocks beneath it are folded. The folds are cut by the Clouds Creek pluton (414.9+2.1/-1.7 Ma, U/Pb z). Straight gneisses containing relict eclogite-hi P granulite boudins are cut by the 414±8 (U/Pb, z) Ma Newberry granite. These observations indicate a subduction + collision of the more mafic Neoprot. Ch terrane and the dominantly felsic and coeval C slate terrane. The timing of this event may be at or about 544 Ma, but must occur before ca. 415 Ma.