Melt generation beneath ocean islands: a U-Th-Ra isotope study from Lanzarote in the Canary Islands

New major and trace element data, and Sr, Nd, Pb, U, Th and Ra isotopes are presented for prehistoric and historic lavas from Lanzarote in the Canary Islands. These rocks are amongst the most primitive found on intraplate ocean islands ranging in composition from basanite to alkali basalt, with MgO contents >9.3% and Mg numbers >67. The youngest are from two of the three 1824 vents, the largest group of samples is from the best known eruption episode, the 1730–36 Timanfaya eruptions, a smaller group of samples are from the northeast Corona region (∼50 ky) and the oldest samples are from the Famara complex and basement massif. The rocks have some of the characteristics of HIMU OIB, including high Ce/Pb, Nb/Ce and low Nb/U and restricted 87Sr/ 86Sr (0.70209–0.70332). There is significant 230Th/ 238U disequilibrium ( 230Th excesses range from 6–76%) with some of the intermediate silica composition Corona samples showing the greatest disequilibrium. The historic samples exhibit 226Ra excess. The major and trace element data have undergone fractionation corrections to Mg numbers of 70, requiring