GEOCHRONOLOGICAL, GEOCHEMICAL, AND PETROLOGICAL CONSTRAINTS ON THE ORIGIN OF THE CARTOOGECHAYE TERRANE, CLYDE-DELLWOOD AREA, WESTERN NORTH CAROLINA: IMPLICATIONS FOR THE LATE PRECAMBRIAN TO EARLY PALEOZOIC EVOLUTION OF THE EASTERN LAURENTIAN MARGIN

The Cartoogechaye terrane (CT) is an enigmatic migmatite terrane within the Central Blue Ridge province of the southern Appalachians. The eastern Laurentian margin grew and evolved through terrane transfer, pluton emplacement, and crustal recycling from the Mesoproterozoic through the Paleozoic via two Wilson cycles (Dalziel et al., 1994). Episodic orogenies associated with both cycles resulted in regional high-grade metamorphism that overprinted original features typically used to discriminate terranes, thus obscuring the affinity of the CT. Previous research on the CT indicates that it could have one of three origins: (1) Laurentian (North America) basement: (2) syn-to late Grenvillian (ca. 1.0 Ga) cover sequence; or (3) late Neoproterozoic (ca. 650 Ma) distal Laurentian margin-oceanic transitional terrane (Hatcher 2004). Detrital zircon U-Pb geochronology and whole rock geochemistry of metasedimentary lithologies, and comparison with existing detrital zircon geochronology from other bedrock map units in the region, will provide further constraints on the crustal affinity of the CT. The Clyde quadrangle consists of four distinct lithologic packages which include: the CT, Ashe metamorphic suite, Great Smoky Group, and Grenville basement. Detrital zircon from the Trimont Ridge Complex displays a variety of textures and grain shapes. Preliminary SIMS U-Pb geochronology show dominant zircon age peaks at ca. 1075, 1100, and 1225 Ma, with a youngest date at ~650 Ma and the oldest date at ~1465 Ma. A mean age for the majority of the grains that define the major age mode is 1150 ± 8 M, consistent with a Mesoproterozoic Grenville (Shawinigan) provenance. The range of SIMS ages suggest that the Cartoogechaye terrane is most likely a Grenville-sourced metasediment, and not an orthogneiss. Additional ages and geochemical data for the CT and associated rock units in the Clyde quadrangle will help to determine the provenance of the CT and its role in the evolution of the Laurentian margin.