Geochemistry of dike rocks in Dun Mountain Ophiolite, Nelson, New Zealand

Abstract Basaltic dikes of the Lee River Group (Permian) at Roding River and in the Red Hills ultramafic body, both parts of the Dun Mountain Ophiolite, were analysed for major and trace elements. The dikes in the Lee River Group change into massive and pillowed lava towards the uppermost part of the sequence. The dikes in the Red Hills occur parallel to the layering of host ultramafic rocks. The Red Hills ultramafic body corresponds to the mantle‐crust transition zone. The age of Red Hills dikes has been determined at c. 280 Ma. Hence, the Lee River Group and Red Hills dike complexes are about the same age. There are contrasting differences, however, between major and trace element compositions in those two dike rock groups. Lee River Group basalts show an increase in FeO∗/MgO with increase in SiO‐ 2; high field strength elements and REE concentrations are higher in the Lee River Group than those in the Red Hills basalts; and eNd values are +7.5 to +8.3, suggesting the source to be depleted mantle. On th...