Fractionation, partial melting, and mixing in normal basalts from 22~25˚ N, mid-atlantic ridge

International Symposium on the Activity of Oceanic Volcanoes. Ponta Delgada, 4-9 August 1980.Much of the recent work on ocean ridge basalts has been directed toward supposedly «abnormal» sections of spreading ridges associated with inferred «mantle plumes». Such samples are especially well represented in the successful deep drilling accomplished by DSDP leg 37 (Aumento, Melson, et al., 1977) and in the data set from FAMOUS (White and Bryan, 1977; Langmuir et al., 1977; Bryan, 1979). The Mid-Atlantic Ridge near 22° N has been the source of many of the basalt samples on which our concepts of «normal» sea floor are based. As a result of a series of cruises associated with study of a «normal» oceanic crustal section in and near the Kane Fracture Zone at 24° N, about 150 new glass and whole rock major element analyses and trace element analyses of selected samples have been completed, representing dredge stations between 22° and 25° N. The data are discussed in detail by Bryan et al., 1981. These dredge data are supplemented by extensive published data for DSDP sites 395 and 396 located nearby (Melson, Rabinowitz et al., 1978; Dmitriev, Heirtzler et al., 1978). In both quantity and compositional diversity, these samples approach those from leg 37 and FAMOUS. However, some important differences do exist, both in absolute element abundances and in the nature of inter-element co-variances of both major and trace element data.