GeoScienceWorld
GeoRef Record 1995-070966

Nd isotopic evidence for juvenile crust in the Carolina terrane, Southern Appalachians

Nd isotopic evidence for juvenile crust in the Carolina terrane, Southern Appalachians

Abstract

Nd isotopic analyses of whole-rock samples from the older portion of the Carolina terrain, one of the oldest in the Appalachian orogen, show that part of this terrain is composed of juvenile, mantle-derived crust. These data suggest that the terrain may not have originally been built upon old, evolved basement material, but upon oceanic crust. A recent study by other workers demonstrates a more crustally evolved Nd isotopic signature for younger components of the Carolina terrain. These data may indicate that the terrain interacted with evolved crust at a later time, possibly by amalgamation with a more evolved crustal fragment before final accretion to Laurentia, rather than indicating a primary old basement. It is suggested that Carolina is a chemically evolved crustal fragment that formed in a continental margin setting for an unusually long time. In this regard the Carolina terrain is similar to some of the large accreted terrains in the Canadian Cordillera. The presence of juvenile crust in the Carolina terrain shows that at least part of the S Appalachian orogen is not composed solely of reactivated pre-existing continental crust. The importance of this part of the orogen in terms of the volume of juvenile Phanerozoic crustal material in N America may be greater than previously thought.