Application of cathodoluminescence to fine-grained pelitic schists of the Imjingang Belt, Korea

Cathodoluminescence (CL) was used to investigate the mode and compositional zoning of plagioclase in fine-grained metapelites of the Imjingang Belt, K orea. Minute, untwinned grains of plagioclase are indistinguishable from qu artz under the polarized light microscope. However, distinct colour and int ensity of the CL of plagioclase permit not only rapid identification but al so characterisation of its compositional zoning on a thin-section scale wit hout extensive compositional mapping. The abundance of plagioclase in the a nalysed samples suggests that this mineral could be mure common in low- to medium-grade metapelites than previously recognized. CL colours of plagiocl ase vary from dull green through green to bright greenish yellow as the An content increases. Furthermore, CL petrography suggests the syn-kinematic g rowth of outer part of plagioclase (An(51-69)) Hence, CL microscopy can pro vide a wealth of information not only for deciphering P-T-t paths but also for microfabric analysis of fine-grained schists.