A suite of basic to intermediate-acid marine volcanic rocks related to copper sulfide mineralization are developed along Shexian-Xiuning belt, which were formerly regarded as diabase veins or dikes. They are distributed in Niuwu Formation of Proterozoic Shangxi Group consisting mainly of slate- phyllite series with complete Bouma sequence and typical features of turbidite. The Sm-Nd isochron dating of volcanic and related rocks appears as an ideal straight line with a correlation coefficient 0.998. The isochron age is 1286 Ma, which seems to be the oldest age ever obtained for this area. These data suggest that the volcanic rocks along Shexian-Xiuning belt could not be products of Late proterozoic back-arc extension. According to varnous aspects of studies carried out in this area, it is held that the geotectonic setting for volcanic rocks of this belt is a Middle Proterozoic island arc. The Sm-Nd model age is not remarkably different from the isochron age. This has led us to consider that volcanic rocks were formed in a very active environment during Proterozoic, probably in an island arc along the margin of the Yangtze paleoplatfoxm. Nd isotopic studies of volcanic rocks show Sm/Nd=0.318, (143Nd/144Nd)1=0.51118 and: εNd(t))=3.9±0.44, implying that the marine volcanic rocks along Shexian-Xiuning belt might have been derived from the depleted mantle.