9526594 Shervais The object of this proposal is to investigate connections between the dynamics of mantle plumes and continental basalts. The proposed connection between mantle plumes, flood basalts, and intraplate seamount chains implies that volcanic rocks which form by passage of lithosphere over a mantle plume will display chemical and isotopic compositions which vary in response to plume dynamics and interactions between the plume and the overlying lithosphere. The P.I.s propose to investigate this process by examining spatial and temporal variations in the chemistry of basaltic lavas found in the Snake River Plain along a transect between Mountain Home and Twin Falls, Idaho. Selected samples from each will be analyzed for major and trace element geochemistry by XRF spectrometry (USC); a representative subset of these will be chosen for analysis of additional trace elements ICP-MS (Centenary),and radiogenic isotopes (SDSU). The P.I.s plan to date 14 lava flows using 39Ar/40Ar (Berkeley Geochronology Laboratory). These data will allow us to assess changes in the mantle source regions of the basalts, and to identify the effects of lithospheric and crustal assimilation.
