Age,volume, compositional and spatial relations of small isolated oceanic central volcanoes

The volumes and ages of small isolated seamounts from both fracture zone and normal crust settings are related to the chemical composition of their lavas. Small volcanoes on or near ridge crests are composed of LIL-depleted ocean ridge tholeiite and are later capped successively by alkalic basalt and alkalic differentiated lavas as they drift away from the ridge. In addition, it appears that contemporaneous seamount volcanism is tholeiitic near the ridge crest and alkalic on the ridge flanks. No significant differences are found between the chemical compositions of lavas from small seamounts located on fracture zones and those on normal oceanic crust.