Long-term reaction path modeling of radionuclide fixation in geosphere by spectroscopic methods

As a first step of the reaction path modeling of the long-term behavior of iron during water-rock interactions, visible diffuse reflectance spectroscopy and infrared microspectroscopy have been applied to elucidate chemical forms of iron and water in granitic rocks. These spectroscopic methods revealed that at least a part of dissolved iron in groundwater is finally fixed in granitic rocks as ferric iron hydroxides or oxides. Their chemical forms depend on the geochemical environments; ferric iron hydroxides are precipitated around biotite during the weathering and geothite and hematite are preserved inside feldspars along the fracture after the hydrothermal alteration. The behaviors of iron during these natural processes are expected to provide bases for the evaluation of long-term behaviors of certain radionuclides such as Am