Magma Supply Dynamics at Slow Spreading Rates: South Atlantic at 26 Degrees South

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This is a project to test whether central or multiple supply is dominant (e.g., as a function of spreading rate, or regionally at the same spreading rate), by carrying out a laboratory petrologic and geochemical study of closely-spaced (7 km) samples from a well-mapped 100 km-long segment of the slow spreading (35-40 mm/yr) Mid-Atlantic Ridge (MAR) at 26 degrees S. The 26 degrees S segment is ideal for such a test because of its simple along-axis morphology (typical of many MAR segments), the absence of hot spot influence, the existence of dense Seabeam, gravity, and magnetic data, and the availability of closely-spaced axial basalt samples an samples from nearby seamounts, Preliminary chemical data for the samples show remarkably regular and systematic patterns of along-axis chemical variations, indication that continued, more detailed petrologic and chemical studies are justified. %%% Process that supply basalt melt to active mid-ocean ridges are of current interest because melt supply dynamics play a key role in the formation of oceanic crust. Dr. Batiza possesses an important set of closely spaced samples at a slow spreading ridge axis. The results will improve our understanding of magma supply dynamics at a slow spreading ridge, and the data will be useful for comparison with similar data sets for fast- spreading ridges.