| The hydrogen and oxygen isotope ratios in hydrous minerals and volcanic glass are used as paleo-proxies to infer isotopic values of meteoric waters and thus paleo-climate conditions. Long-term exposure experiments with Mt Mazama ash reacted with isotopically labeled water (+650‰ delta 2H, +56‰ delta18O) at 70, 40 and 20°C show delta2H increase with time and faster deuterium uptake at higher temperatures. Times ranged in duration from 24 to 14454h. Long duration exposure shows no net increase in water nor delta18O in ash. Ash was analyzed by TC/EA mass spectroscopy, thermogravimetric analysis and infrared spectroscopy (KBr pellets) measuring delta 2H, total water, and OH water peaks. This study demonstrates delta 2H in ash changes by minor diagenesis even at relatively low temperatures of 20°C. A diagenetic history of ash is needed to interpret delta 2H, but delta18O values are more robust.;This thesis includes both previously unpublished and co-authored material. |
