Exploring the impact of diagenesis on (isotope) geochemical and microstructural alteration features in biogenic aragonite

摘要: For the Quaternary and Neogene, aragonitic biogenic abiogenic carbonates are frequently exploited as archives of their environment. Conversely, pre-Neogene aragonite is often diagenetically altered calcite studied instead. Nevertheless, exact sequence diagenetic processes products difficult to disclose from naturally material. Here, experiments were performed understand alteration products. Shell subsamples bivalve Arctica islandica exposed hydrothermal alteration. Thermal boundary conditions set at 100 degrees C, 175 C 200 C. These comparably high temperatures chosen shorten experimental durations. Subsamples different O-18-depleted fluids for durations between two twenty weeks. Alteration was documented using X-ray diffraction, cathodoluminescence, fluorescence scanning electron microscopy, well conventional clumped isotope analyses. Experiments show redistribution darkening organic matter, but lack evidence alteration, except in Delta(47) which effects annealing processes. At valves undergo significant transformation neomorphism. The delta O-18 signature supports via dissolution reprecipitation, isotopic exchange limited by fluid migration through subsamples. Individual growth increments these exhibit bright orange luminescence. fully transformed purple-blue luminescence with bands. signatures reveal aqueous fluid, whereas C-13 remains unaltered all experiments, indicating a carbonate-buffered system. Clumped high-temperature compositions broad agreement measured temperature. Experimentally induced patterns comparable individual features present Pleistocene shells. This study represents step towards sequential analysis aragonites sheds light on reaction times threshold limits. limitations restricted single test organism acknowledged call refined follow-up experiments.