Sm-Nd and Rb-Sr ages and geochemistry of volcanics from the Dingyuan formation in dabie mountains, central China: evidence to the paleozonic magmatic arc

摘要

The meta-basic volcanic rocks from the Dingyuan formation in Beihuaiyang zone of Dabie Mountains have typical island arc geochemical feature: e.g. negative anomalies of Nb, Ti, P in trace elemental spidediagram and high LREE, Ba, Pb abundances as well as high La/Nb, Ba/Nb, Th/Nb ratios. Their Sm- Nd and Rb-Sr whole rock isochrons give the ages of 446 ± 23 Ma and 444 ± 31 Ma respectively. Based On these geochemical feature and ages as well as their tectonic setting at convergent plate boundary, we Suggest that they were formed in a typical island are environment in the late Ordovician to early Silurian. This is the first evidence to the Paleozoic magmatic arc in the Dabie Mountains.