The Northern Charlotte belt North Carolina and South Carolina: A deformed composite batholith

Abstract

AbstractThe Charlotte belt in North Carolina and South Carolina, U.S.A. is characterized by numerous plutons with granitic to gabbroic composition that have intruded gneiss, schist, metavolcanic rocks, and metamorphosed mafic complexes (basalt, gabbro, and ultramafic rocks). The exposed rock constitutes a composite batholith which contains three superunits: (1) the Old Plutonic (metaquartz diorite, metagranodiorite, and metagabbro) approximately 550 my old; (2) the Concord‐Salisbury (gabbro and granodiorite) approximately 400 my old; (3) the Landis ('big feldspar') granite approximately 300 my old. Geophysical and geologic studies suggest small bodies of granodiorite and mafic complexes intruding metavolcanic rocks, schist, and gneiss form the upper level of the batholith; a thick metagabbro sill penetrated by gabbro stocks and underlain by poikilitic gabbro and small bodies of syenite form the middle level; and a complex of metaquartz diorite and metagranodiorite intruded by Landis granites form the lowest level. Outcrop patterns and structural profiles based on gravity suggest the batholith forms an east‐dipping monocline. The bimodal suite of gabbro and granodiorite plutons suggest a tensional tectonic environment ∼ 400 my ago, and negates subduction as the only mode of formation for the batholith.