Fluid focusing and back-reactions in the uplifted shoulder of the Rhine rift system: a clay mineral study along the Schauenburg Fault zone (Heidelberg, Germany)

摘要: A retrograde sequence of fluid-controlled, low- temperature mineral reactions has been preserved along an east-west striking, dextral-oblique-slip fault in the uplifted Rhine Graben shoulder. This (the Schau- enburg Fault, near Heidelberg), juxtaposes Permian rhyolite against Carboniferous (Variscan) granite and shows syn- or post-rift displacement north-south trending, eastern boundary rift basin. Both texture rock fabric indicate that forms a site high permeability fluid flow, records exhumation fluid-rock history shoulder since Mesozoic. The reaction compositions clay minerals within cataclasite, adjacent lithologies, document progressively decreasing temperatures, with back-reactions pure 2M1 illite to 1Md (R3) illite-smectite, eventually smectite kaolinite assemblages. Compositional variations are attributed Tertiary Recent flushing zone associ- ated flank uplift, progressive dilution electrolyte-rich, acidic neutral hydrothermal brines by down-flowing electrolyte-poor, meteoric waters.