Elemental and isotopic tracing of mineral infillings from various microstructures of a fault system into fine-grained sediments: which interacting fluids?

Elemental contents and Sr isotopic data of calcite celestite infillings from various tectonic microstructures the so-called “Main Fault” that occurs in Opalinus Clay Formation (Switzerland) were used to elaborate on geochemical impact this structural system fine-grained host sediments. The chemical leachates vein, slickenside gouge are significantly different those diffuse undeformed highly deformed rock matrix called scaly clays. For instance, fluids flowing within microstructural veins slickensides could not derive pore waters sediments, as show diffused into matrix. fluid/rock interactions gouges also slickensides, probably due an additional pressure-solution former, complemented by a further local supply organics very close vein micro-features some clays precipitated bi-carbonated and/or sulfated yield almost constant 87Sr/86Sr ratio 0.70774 ± 0.00001 (2 $$\upsigma$$ ). This constrained value points unique homogeneous external source for tectonic-related probable marine origin, signing early, but late faulting event. Notably seeping presently throughout rocks, initial apparently related late-Eocene invasion Delémont Basin occurred during contemporaneous rifting Rhine-Graben system. induced Main-Fault obviously used, at least, if most these earlier microstructures, they signature their infillings. regional evolution includes then episode with resulting flooding deposited sediments faults active seawater. These precisely remained unaffected until renewed activation Eocene Mont Terri its fault new tectonic–thermal created generation thin-skinned deformation Jura Belt around Main Fault, addition event already existed rocks. Connections between two generations be observed wall gallery laboratory. involved belt moved along newly well older ones when accessible. duality allowed preservation same partial dissolution about 30 million years drains