The Westland dike swarm of South Island, New Zealand, consists of a variety of ultrabasic, alkaline rock types including camptonite lamprophyres, ouachitite peridotites, and carbonatites. At least part of the swarm is as young as Oligocene-Miocene age. The majority of Nd and Sr isotope analyses for 16 dikes ε_Nd = +3.5 to +5.2, ⁸⁷Sr/⁸⁶Sr_i = 0.7028 to 0.7035) fall to the left of the mantle array in Nd-Sr isotope correlation diagram. The data are similar to the ocean islands St. Helena and Tubuai and to some continental volcanics and mantle nodules (Menzies and Wass, 1983)....