Initial Publication Date: December 12, 2013

The Petrogenesis and Tectonic Implications of Blue Ridge Mafic-Ultramafic Rocks: The Buck Creek and Carroll Knob complexes, and rocks of the Addie-Willets region

Virginia L. Peterson, Grand Valley State University
Jeffrey G. Ryan, University of South Florida
Steven P. Yurkovich, Western Carolina University



Blue Ridge Mtn photo 1

Intended Audience:This trip was designed for faculty and researchers, and was offered at both the 2006 and 2007 GSA Southeastern Section Meetings, though it was canceled both years due to low enrollment. The organizers have run this trip in parts or as a whole for their own undergraduate geology courses as well. The actual field data collection and much of the primary interpretation was done by undergraduates.

Location:

Central Blue Ridge province in western North Carolina.

Summary:

This field trip examines the unusual and highly metamorphosed mafic and ultramafic rock associations of the central Blue Ridge province in western North Carolina. The aim of the trip is to show attendees the variability and common features among these units, and their use as tectonic indicators for the latest Precambrian geologic history of the Blue Ridge mountains. It was also a way to highlight the scientific results of four years of the Blue Ridge REU Site research program run jointly by Western Carolina University and by USF.

Context:

The trip is intended to be somewhat self-contained, with detailed explanatory text that synthesizes the results from several field research sites. For GSA we were assuming an audience of faculty and students. Access is straightforward (NFS land or highway roadcuts) save for the stops at Chestnut Gap, Balsam, and Addie, which are on private land and permission is required.

Goals:

The metamorphic evolution and igneous petrogenesis of mafic and ultramafic rocks; Assessing metamorphic protoliths based on petrography and chemistry; Sharing professional research results; Documenting the potential of student team research.

Blue Ridge Mtn photo 2

Design:

The trip was designed to highlight the differences in groupings of mafic and ultramafic rocks, and to demonstrate that these can't be easily attributed to variations in metamorphic grade. The protoliths for both the mafic and the ultramafic rocks do, in fact, vary markedly, and these differences can be fingerprinted to a first order by mineral assemblages.

Notes and Tips:

You do need to get permission from the landowners to go into the old Chestnut, Balsam, and Addie quarries. Of the three, the Chestnut quarry is the best for "fresh" outcrops, while the other two are now partly or wholly covered by housing developments.

Assessment and Evaluation:

As we didn't get to run the trip, we didn't assess it in total. Ryan has been using parts of this trip as the field basis for a CCLI-funded classroom project. From the standpoint of seeding further work, the trip has been a success for us.

Materials and Handouts:

Download the field guide and roadlog (Acrobat (PDF) 4MB Feb16 09), as submitted for the 2006 and 2007 GSA Southeastern Section meetings.

References:

Extensive references to Blue Ridge geology are included in the materials and handouts. Aside from these, the following papers have been published from the REU Site program:

  • Peterson, V.L., J.G. Ryan, and the 1997-1998 Blue Ridge Research Experiences for Undergraduates Site Program (2008) Geochemistry and petrogenesis of the Buck Creek mafic/ultramafic suite, western North Carolina. Geological Society of America Bulletin, v. 121, pp. 615-629.
  • Ryan, J.G., S.P. Yurkovich, V.L. Peterson, J. Burr, S. Kruse, and the 2001 REU Site Program Participants. (2005) Geology and petrogenesis of mafic and ultramafic rocks of the Willets-Addie area, Central Blue Ridge, NC. In Hatcher, R.D. and Merschatt, A.J (eds.) Blue Ridge Geology Geotraverse East of the Great Smoky Mountains National Park, Western North Carolina. Guidebook of the 2005 Carolina Geological Society annual field trip, pp. 91-98.
  • Lang, H., Lee, A., Peterson, V. and J.G. Ryan (2004) Coexisting clinpyroxene/spinel and amphibole/spinel symplectites in metatroctolites from the Buck Creek ultramafic body, North Carolina Blue Ridge, USA. American Mineralogist, v. 89, pp. 20-30.
  • Berger, S, Cochrane, D., Simons, K. Savov I., J.G. Ryan, and V.L Peterson (2001) Insights from rare earth elements into the genesis of the Buck Creek Complex and other Blue Ridge ultramafic bodies. Southeastern Geology, 40, p. 201-212.