Hydrogen isotope geochemistry of nominally anhydrous minerals

Mantle derived materials span a range of ~100 ‰ in hydrogen isotopic composition. Nominally anhydrous minerals from mantle xenoliths are the most deuterium depleted of all mantle materials, with δD values 50 ‰ lower than average mid ocean ridge basalt. These variations suggest large hydrogen fractionations within the mantle but available data are limited to large, high quality samples needed for conventional measurement techniques. We have recently developed a continous-flow technique for measuring hydrogen isotopic composition in small (5-50 mg) samples of mantle pyroxenes, making it possible to analyze many more mantle samples.