Detailed Geochemical Investigations of the East Pacific Rise: 9 Degrees 16' North-9 Degrees 40' North and 13 Degrees 30'-15 Degrees 00' North

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This is a project to carry out trace element and isotopic analyses on samples from the East Pacific Rise at 9> 16' to 9> 40' N and 13> 30' to 15> N that have been obtained by dredging on a fine scale. The objectives are to investigate trace element and isotopic heterogeneity among lavas from a single magma chamber, to study nature of ridge segmentation and its controls on fine scale geochemistry, examine temporal variability and test hypothesis the local Pb-Pb correlations are isochrons recording the age of local mantle heterogeneity. %%% One of the most interesting results of geochemical measurements on rocks dredged from the sea floor in recent years has been fine scale variations of composition along the axis of mid-ocean ridges where the rocks are formed. These compositional variations appear to be related to tectonic segmentation of the ocean ridge axes themselves, but the details are not well understood. This project, being carried out by an established geochemist (White) and a bright young geochemist (Castillo), who was engaged in the initial collection on the sample set, on a suite of rocks from an area where much geophysical data exists, should yield significant insight into the relationship between tectonic and magmatic segmentation of ridge crests.