A major emphasis of recent marine geological studies has been to relate the detailed geochemistry and petrology of crustal rocks to the fine-scale features present along mid-ocean ridges. Initial models of the sea-floor spreading process had assumed that crust was created from long, fairly continuous, axial magma chambers. Although minor variations in chemistry were allowed in these models, the composition of the erupted lavas was assumed to be fairly constant. With the advent of detailed mapping systems such as Seabeam and Seamarc, a whole new class of processes were revealed in ridge crest bathymetry. New models emerging from these data indicate that the ridge axis is composed of a series of small, discrete magmatic segments or individual volcanoes. The lavas produced from these volcanoes appears in many cases to be chemically distinct. The objective of the present project is to examine the chemistry of basalts in several of these segments along the East Pacific Rise using the research submersible Alvin. Previous surface ship sampling has defined the gross changes in basalt chemistry related to features such as overlapping spreading centers, off-set ridge axis, and transform faults. Alvin will now be used to sample in detail at boundaries between such features. These data will be used to constrain the nature and distribution of subsurface magma chambers and their relation to the individual morphological segments along the ridge axis. The principal investigators are well qualified to complete the proposed project.
