Strontium distribution and origins in a natural clayey formation (Callovian-Oxfordian, Paris Basin, France): A new sequential extraction procedure

摘要: Abstract Strontium is a good monitor of geochemical processes in natural clayey formations. In the Callovian-Oxfordian formation Bure France, strontium sorbed on clay minerals and carried by carbonates, detrital accessory celestite. order to determine distribution among these different phases, four-step sequential extractions (1. cobalt hexamine trichloride, 2. acetic acid, 3. EDTA 4. tri-acid) were performed samples from levels formation. The leachates also analyzed for isotopes, origins. This procedure well suited determining claystones, although it less efficient clay-rich limestones celestite-rich samples. carbonates (38–47% total strontium) show 87Sr/86Sr ratios (0.7070–0.7071) that have recorded isotopic composition seawater. Diagenetic (dolomite, ankerite siderite) almost not incorporated any strontium, which has been trapped celestite during late diagenesis. major part shows (0.7069–0.7070) quite close primary carbonates. However, second generation (0.7074) slight 87Sr-enrichment isotopically equilibrium with exchangeable (27–48% mean value 0.70745) present-day porewater (0.7074). very low could be explained partial destabilisation (feldspars, micas, clays) exhibit consistent their pristine Hercynian origin (0.7229–0.7350). Diffusion subjacent Dogger aquifers (0.7076–0.7082) invoked explain 87Sr-enrichment.