The He-Ne-Ar-H2O-CO2 isotope and abundance systematics of the Reykjanes Ridge: Constraints on plume-ridge interaction and the degassing history of the Icelandic hotspot

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This proposal addressees fundamental questions related to the origin of the earth's mantle and atmosphere, the history of mantle flow and present mantle processes, and the nature of mantle melting and the interaction of mantle plumes with ambient mantle. More specifically, the goals of the proposal are to understand the processes of mixing and mantle flow that accompany the interaction of a mantle plume with the normal mantle below mid-ocean ridges. The approach of this proposal is to look at volatile abundances and isotope ratios, especially H, He, Ne, Ar, and CO2 and H2O. Well-characterized dredged samples are available from UK investigators for the Reykjanes Ridge between 57 and 63 degrees north. Preliminary 3He/4He and He abundance data show that degassing is an important process north of 61 degrees, where shoaling eruption depth results in extensive degassing and low He abundances. There are five individual hypotheses that can be tested with the data to be collected, most having to do with the intrinsic processes that happen in combination with apparent 2-component mixing of plume and MORB mantle seen with other components. The noble gas data will be collected by crushing, stepped combustion and with a laser probe, a new and promising method.