Editorial: Recent Advancements in X-Ray and Neutron Imaging of Dynamic Processes in Earth Sciences
Frontiers in Earth Science
Earth is a dynamic system; therefore, the study of geological processes in function of time is of paramount importance. Also, geological systems often evolve at non-ambient conditions, thus limiting the applications of the most common imaging techniques. Many processes in different scenarios: volcanic, metamorphic, and reservoirs, but also man-made cement-based materials and ceramics, are inherently dynamic and require an investigation in 4D (three-dimensions, 3D + time) to be fully understood.
... e fully understood. These processes are subject to changes due to mechanical stress, reactive transport, heating, etc. The high-penetrating power of hard X-rays and neutrons, coupled with the recent advances in instrumentation and computational methods, fostered the growth of novel imaging approaches, making microradiography and computed microtomography (microCT) unique tools to observe internal structures of materials undergoing different processes. This Research Topic is focused on hard X-ray and neutron-based imaging studies carried out under controlled conditions, representing the next generation of in-situ time-resolved experiments, with applications in different fields of Earth Sciences, as shown in this Research Topic. A large number of contributions are related to the investigation of fluid flow and transport properties in porous rocks. The high sensitivity of neutrons to hydrogen-based fluids has been exploited by Cordonnier et al. to investigate the subsurface transport of pollutants, such as cadmium, in limestone samples by using in-situ neutron imaging. Their experiments allow constraining parameters such as local hydraulic conductivity and sorption properties of the dissolved cadmium by the solid matrix, showing that cadmium transport follows preferential pathways. Dynamic neutron imaging has been also used by Zambrano et al. to characterize the geometrical properties of the pore network in carbonate reservoirs. In this study, the complementary results provided by neutron and X-ray imaging are used as an input for computational fluid dynamics simulation. This integrated approach provided novel information about fluid storage and migration in reservoir rocks. The mineral dissolution in porous diamond has been analyzed by Eckley and Ketcham using laboratory-based X-ray microCT during a sequential acid leaching procedure. The formation of fluorides during acid digestion, which can persist throughout acid leaching procedures, is observed. This can drastically affect yields for geochemical measurements of certain elements. Different segmentation procedures are tested showing that the utilization of CT number information to discern partial porosity below the resolution limit is more reliable than purely binary segmentation.