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Helium and neon isotopes in the Imnaha Basalt, Columbia River Basalt Group: Evidence for a Yellowstone plume source |
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| Authors: | Allen Dodson B Mack Kennedy Donald J DePaolo |
| Institution: | aBerkeley Center for Isotope Geochemistry, University of California, Berkeley, CA 94720-4767, USA bDepartment of Geology and Geophysics, University of California, Berkeley, CA 94720-4767, USA cEarth Sciences Division, Ernest Orlando Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA |
| Abstract: | Helium, neon, and argon isotopic compositions were measured in two flows of the Columbia River flood basalt. The Imnaha Basalt has a 3He/4He ratio of 11.4 times atmospheric and 20Ne/22Ne and 21Ne/22Ne ratios characteristic of a plume component. The measured 3He/4He is a lower limit, due to possible preferential 3He loss and/or addition of radiogenic 4He. A Wanapum Basalt flow, erupted approximately 2 Ma later in the waning stages of volcanism, has more MORB-like noble gases. The He, Nd and Sr isotopic compositions of these lavas suggest that the Columbia River basalts were derived from the Yellowstone plume head which contained both ‘high-helium’ plume material and entrained depleted mantle. As the eruptions progressed the plume component in the melting region was gradually diluted or replaced. |
| Keywords: | Columbia River Basalt Group He-4/He-3 Ne-22/Ne-21 Ne-22/Ne20 plumes geochemistry flood basalts |
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