T116 Gondwanan Terranes along Laurentian Margins

Monday, 28 October 2013
8:00 AM - 12:00 PM
Room 505

ONE ARC, TWO ARCS, OLD ARC, NEW ARC: THE CAROLINA TERRANE IN THE SOUTHERN APPALACHIANS OF NORTH CAROLINA

Paper number: T116-1
Program: Technical Sessions
Time: 8:00 AM – 8:20 AM

Authors

Abstract

The Carolina terrane forms the heart of Carolinia, one of the largest accreted peri-Gondwanan crustal tracts within the Appalachian Orogen. The terrane consists of two major lithotectonic elements, the older Neoproterzoic Hyco magmatic arc, ca. 633-612 Ma, and the younger Neoproterozoic-early Paleozoic Albemarle magmatic arc, ca. 555-<528 Ma. Both formed in suprasubduction zone magmatic arc settings; the Hyco arc is interpreted to have formed mainly on an oceanic basement, whereas isotopic and geochronological data indicate that a more evolved crustal component was present beneath the Albemarle arc. The arc sequences are separated by an unconformity, and in places, a third lithotectonic unit consisting of clastic sedimentary rocks with subordinate volcanics, the Virgilina sequence, intervenes between them. The tectonic setting of the Virgilina rocks is unclear. Combined Sm-Nd and U-Pb databases are consistent with Carolina having formed proximal to Amazonia and its peripheral orogenic belts. The Carolina terrane appears to have departed from its peri-Gondwanan source area in the Early to Middle Cambrian; the c. 545 Ma Stony Mountain gabbro likely heralded this event and the Middle Cambrian or younger Kings Mountain sequence may represent a sedimentary record of this rifting.

Two major tectonothermal events have overprinted rocks of the Carolina terrane. The Neoproterozoic Virgilina deformation, ca. 578-545 Ma, is heterogeneously developed in the Hyco arc and Virgilina sequence. This event appears to overlap in time with the stitching of the two largest components of Carolinia, the Carolina and Charlotte terranes at ca. 550 Ma. Eclogite metamophism in the Charlotte terrane of South Carolina may be related to this event. The second event, the Cherokee orogeny, has penetratively overprinted rocks of the Carolina terrane with a steeply northwest-dipping cleavage that is axial planar to southeast vergent folds, locally associated with southeast vergent thrust faults. Multiple thermochronologic studies on micas defining cleavage indicate that this event started in the Late Ordovician and likely continued into the Early Silurian. The Cherokee orogeny most likely marks the accretion of Carolinia to Laurentia.