27 Recent Advances in Western Blue Ridge Geology

Friday, 24 March 2006
8:00 AM - 12:00 PM

THE CHATTAHOOCHEE-HOLLAND MOUNTAIN FAULT: A TERRANE BOUNDARY IN THE BLUE RIDGE OF WESTERN NORTH CAROLINA

Paper number: 27-9
Program: THEME SESSIONS
Time: 10:15 AM – 10:35 AM

Authors

Abstract

The Chattahoochee-Holland Mountain (CHM) fault, south and east of Sylva, NC, marks the transition from the central and eastern Blue Ridge and separates paragneisses of the Dahlonega gold belt (DGB) and Tugaloo terranes. The footwall is composed of middle amphibolite facies metasandstone and schist of the DGB, in the Great Balsam Mountains window. Hanging-wall rocks of the Tugaloo terrane consist of migmatitic, sillimanite I grade Tallulah Falls-Ashe Formation of metagraywacke and schist with interlayered amphibolite that has been subdivided into the standard stratigraphic succession of lower, middle and upper Tallulah Falls. This terrane is locally intruded by two granitic plutons: the Mississippian (355 Ma) Walnut Creek granodiorite (WCG) and an unnamed granitic body. Both terranes also contain ultramafic rocks varying from soapstone to peridotite, including a large, and partly altered ultramafic body in the Tugaloo terrane. Preliminary estimates of peak metamorphism indicate temperatures of 650 C and pressures ranging from 4-5 kbar.

Recent field, petrologic, and geochronologic data collected from this area reveal new information regarding the structure and metamorphism of the DGB and Tugaloo terranes as well as timing of emplacement of the CHM fault. Field data reveal three fold geometries: early isoclinal, intermediate closed, and later open folds, indicated by overprinting relationships. The CHM fault is tightly folded in the SW part of the field area and the dominant NE trending foliation appears to cross the fault. Southwest of the field area the CHM fault truncates the 335 Ma Rabun Granodiorite indicating that the fault is Alleghanian. In addition, tight folding of the CHM fault and high temperature, axial planar fabrics suggest a late Paleozoic high temperature event affected the Tugaloo and DGB terranes.