THE NORTHERN ROLESVILLE BATHOLITH AND ADJACENT PIEDMONT STRUCTURES AND TERRANES

Detailed NCGS STATEMAP mapping in the Henderson 1:100K sheet over the past ten years has brought to light some magmatic and structural features of the northern portion of the Pennsylvanian Rolesville granitoid batholith and its relationships to neighboring wall-rock terranes and fault zones. The mapping, in the Kittrell, Henderson, Middleburg, Townsville, Gold Sand, and Ingleside 7.5-minute Quadrangles, has led to the following observations.

(1) In the manner applied by Speer (1994) in the Raleigh 1:100K sheet, several plutonic granitoid phases of the Rolesville batholith may be distinguished in the Henderson sheet, based upon petrographic features, enclaves, and field relationships. (2) A much more extensive plutonic compositional range than heretofore recognized is indicated by the occurrence of a number of small pods of granodiorite, quartz diorite, diorite, and gabbronorite within the western (deeper?) portion of the batholith. (3) The Castalia and Gupton plutons are satellitic to the main part of the Rolesville batholith along its northeastern margin. Deformed phases of the Gupton pluton highlight the Alleghanian Macon fault zone and are in contact to the east with metamorphic rocks of the volcanogenic Spring Hope terrane, there locally raised to amphibolite facies. (4) Between the Gupton pluton and the main part of the Rolesville batholith, the Louisburg re-entrant contains sillimanite-zone gneiss and schist of the newly named Warren terrane, considered distinct from the Raleigh terrane to the south and west. (5) Alleghanian strain ascribed to the Lake Gordon mylonite zone overprints granitoid rocks at the northern and northwestern margins of the Rolesville batholith across a corridor several km in width. (6) Undeformed granite crosscuts mylonitic granitoid gneiss, indicating that pulses of magma intruded both syn- and post-kinematically with respect to Alleghanian dextral shear strain. (7) The western margin of the batholith is in contact with the Raleigh terrane, structurally overprinted along its western flank by the Lake Gordon mylonite zone. We infer that south of Henderson the Nutbush Creek fault lies along the western side of the Crabtree terrane.