Ruin marble : a record of fracture-controlled fluid flow and precipitation

The ruin marble structure of the Cretaceous/Paleogene fine-grained marly limestone from the Outer Flysch Belt of the Western Carpathians has a non-tectonic origin, according to structural and sedimentological evidence. Distinctive offsets of coloured red-brownish ferric oxyhydroxide bands are not due to displacements along rock-cutting fractures, as they superficially appear to be. Evidences for shear movement along these pseudo-faults were not observed. Band offsets result from different velocities of pervasively diffusing fluids, precipitating ferric oxyhydroxides in corridors bounded by sets of mineralised systematic joints. During rock weathering, calcite-filled joints operated as barriers for lateral fluid diffusion, but enabled longitudinal diffusion along healed joints. Simple laboratory experiments have been performed to simulate the formation of natural ruin marble structure.