Radiation-enhanced fluid diffusion and alteration around uraniferous inclusions in Cenomanian resinite from North Bohemia

Abstract

Advanced analytical methods including SEM/EDX and μ-PIXE/RBS microanalyses were used to investigate chemical alterations around uraniferous inclusions in a Cenomanian fossil resin (resinite). Studied alterations related to several types of discontinuities in resinite matrix are a model example of the phase interface between solid polymeric hydrocarbon and aqueous fluids exposed to long-term irradiation by heavy energetic ions resulting mostly from the natural decay of uranium. Computational models of ion ranges correspond well with the observed range of alterations about 35 μm from uraniferous inclusions. The major alteration is found within a 20 μm inner zone. It is characterized by distinct sulfur enrichment and an increase in the O/C ratio. No sulfur enrichment in the resinite matrix occurs apart from the uraniferous phases. Proton beam-induced alterations of the resinite were investigated and compared with the natural ones. The differences indicate the importance of aqueous fluids in the natural radiation-induced alteration process. It is concluded that radiation-enhanced mass transfer and reactions occur at solid-fluid interfaces during the long-term energy deposition by alphas, alpha recoils, and fission fragments combined. The role of thermal effects and and formation of radical species by radiolysis of aqueous fluids on a microscale is discussed.