Major and trace element data are presented for 33 greenstones of Ordovician and Silurian age from Stord, west Norway. The Ordovician greenstones contain relatively high concentrations of incompatible trace elements, whereas the Silurian greenstones have extremely low abundances. This feature is thought to be due to generation by low and high degrees of partial melting, respectively. The Ordovician greenstones are variable in their chemistry, and may represent an intermediate to evolved island are. On the other hand, the Ordovician sequence could include slices of ocean floor/oceanic island basalt, in tectonic contact with island are rocks. It is tentatively suggested that the Silurian greenstones, comparable to ocean floor tholeiites, have been generated in an actively evolving back-are basin.
Interpretation of preliminary trace element data from Lower Palaeozoic greenstone sequences on Stord, west Norway