Morphology, Abundance, and Chemistry of Near-Ridge Seamounts in the Vicinity of the Mid-Atlantic Ridge (Approximately) 26 deg S

摘要

Small (<150 m high) volcanic cones and larger oceanic central volcanoes (seamounts) up to 600 m high are abundant near the Mid-Atlantic Ridge approx. 26 S. They are present along the axis, within the rift valley floor, and also on the ridge flanks. Seabeam mapping of approx. 16,500 sq.km within about 130 km of the axis (approx 7 Ma) shows up to 118 seamounts and cones for a normalized abundance of approx. 7000/1,000,000 sq.km. Their abundance is highest near the axis and decreases outward on the flanks of the ridge. Small cones and seamounts are much more abundant than large ones. They range in shape from simple cones with flat summits to more complex flat-topped volcanoes with summit summit craters, arcuate summit benches, and satellite cones. Volcanic rocks dredged from nine of these seamounts are all depleted mid-ocean ridge basalt (N-MORB). Keywords: Seamounts, Morphology, Abundance, Chemistry, Seabeam, Mid Atlantic Ridge, Reprints. (MJM)