THE STRUCTURE AND PETROLOGY OF THE PEDEN METAULTRAMAFIC BODY, NW NORTH CAROLINA, USA
Petrologically, the body consists of two main rock types — chlorite+Ca-amphibole schist and talc+Mg-amphibole schist. The contact between the two is abrupt and is marked petrographically by 1) a change in groundmass from chlorite to talc, 2) a decrease in amphibole size and character, and 3) an increase in amphibole abundance. Amphiboles vary in size from 5mm to 0.07mm, and with similarly oriented chlorite and talc, define the dominant foliation. Locally, the chlorite-amphibole schist is porphyroclastic, with larger (older) zoned amphiboles enclosed by a matrix of smaller amphiboles and chlorite. Three generations of amphiboles likely represent three amphibolite to greenschist facies metamorphic assemblages (modified equivalents of Raymond’s A3, A4, and A5 assemblages; Raymond, 1995 p.669; Swanson and Raymond, 2010): A3 = hornblende cores with abundant ilmenite and magnetite inclusions + biotite, A4 = clear amphibole rims + chlorite, and A5 = finer-grained matrix amphiboles + chlorite. The Peden body is polylithologic and has a polyphase metamorphic and deformational history, the clarification of which requires integrated field and petrologic study.