REEVALUATING THE CHARLOTTE AND CAROLINA TERRANE BOUNDARY: BEDROCK MAPPING,GEOCHEMICAL ANALYSES, AND U/PB AGE-DATING IN THE GREENSBORO 100K

This study presents a geologic map of the McLeansville quadrangle, contributing to the Greensboro 100k map, used by the North Carolina Geological Survey (NCGS) for USGS Geoframework Initiative efforts. The McLeansville area, part of the Carolina terrane, is heavily intruded by the Greensboro Intrusive Suite, with reconnaissance mapping revealing an ultramafic body in the northwest. The study aims to classify host-rock lithologies as low- or high-grade metamorphic rocks to determine their association with the Carolina or Charlotte terrane. Secondary objectives include documenting shear strain in the bedrock and analyzing the ultramafic body’s petrology and geochemistry for evidence of a suture zone between these terranes.

The McLeansville area, along with parts of Greensboro, offers a key setting to study island arc accretion to Laurentia during Appalachian Mountain formation. This is essential for understanding regional rock types, deformation, and mineral resource potential. Field investigations identified major lithologic units and structural fabrics, and samples were collected for laboratory analysis to interpret original geologic processes.

Preliminary results suggest lithologies are inconsistent with established Carolina or Charlotte terrane characteristics. Notable outcrops near the ultramafic body feature amphiboles resembling amphibolite facies rocks of the Charlotte terrane. The dominant felsic unit of the Greensboro Intrusive Suite was confirmed, but scattered mafic rocks suggest additional ultramafic bodies or mafic dikes. Some felsic lithologies have unusual quartz- and feldspar-rich compositions. Evidence of foliation in several outcrops provides critical insights into the extent of deformation in the region.

This work emphasizes the value of field mapping and petrologic analysis in understanding terrane boundaries and tectonic evolution in the southeastern Appalachians, guiding future geologic and economic exploration.