Hydrogen Isotope and Water Content Analysis of Ultralow Volume Volcanic Glass

Hydrogen isotope and H₂O content of hydrated volcanic glass are useful proxies for paleoelevation and paleoclimate reconstruction. However, their analysis remains challenging because conventional bulk methods typically require relatively large amounts (∼10^-3-10^-2 g) of purified and fresh volcanic glass. Volcanic glass from the Mesozoic sediments and scientific drilling core samples is commonly affected by alteration and grain-scale heterogeneity, and the available sample mass is often insufficient for bulk analysis. Here, we present an ultralow sample consumption (∼10^-9 g) in situ method for determining H₂O contents and hydrogen isotope of hydrated volcanic glass from Early Cretaceous tuffs. This approach extends such analyses to older and less-well-preserved materials and provides a practical basis for high-resolution paleoenvironmental reconstruction.