Abstract
High spatial resolution (10-30 μm), in situ oxygen isotopic analyses by secondary ion mass spectrometry (SIMS), coupled with high-resolution transmission electron microscopy (HRTEM), were used to show that uraninite from the Oklo-Okélobondo natural fission reactors that occur in near surface environments, have low δ18O values and nanotextures that are consistent with interaction with ground water. These low δ18O values (-14.4 to -8.5‰) suggest that the minerals exchanged with meteoric groundwater. In contrast, reactor zones that occur at depth have largely retained their original O isotopic composition (-10.2 to -5.6‰) and uraninites are well-crystallized and essentially defect-free. These observations clearly demonstrate that by combining both HRTEM and in situ O isotopic analyses by SIMS, it is possible to characterize the nano-scale porosity and postdepositional alteration of U-bearing phases.
© 2015 by Walter de Gruyter Berlin/Boston
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- Synchrotron infrared spectroscopy of OH-chondrodite and OH-clinohumite at high pressure
- Structural deformation mechanisms of zeolites under pressure
- Variation of hydrogen bonded O···O distances in goethite at high pressure
- Pressure-controlled polytypism in hydrous layered materials
- OH– in synthetic and natural coesite
- Pressure-induced phase transformation of kalicinite (KHCO3) at 2.8 GPa and local structural changes around hydrogen atoms
- Potential docking sites and positions of hydrogen in high-pressure silicates
- Contrasting bonding behavior of two hydroxyl-bearing metamorphic minerals under pressure: Clinozoisite and topaz
- Experimental investigation of crystallization kinetics in a haplogranite system
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- On the origin of size-dependent and size-independent crystal growth: Influence of advection and diffusion
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