Mid‐Ocean Ridges host various types of hydrothermal systems including high‐T black‐smokers found in ultramafic rocks exhumed along slow spreading ridges. These systems are mostly described in two dimensions as their exposure on the present‐day seafloor lacks the vertical dimension. One way to understand these systems at depth is to study their fossilized equivalents preserved on‐land. Such observation can be done in the Platta nappe, Switzerland, where a Jurassic‐aged mineralized system is exposed in 3D. Serpentinites host a Cu‐Fe‐Ni‐Co‐Zn‐rich mineralization made of sulphides, magnetite and Fe‐Ca‐silicates either replacing serpentinites or within stockwork. Fe‐Ca‐silicates, abundant at the deepest levels, vanish in the mineralization close to the palaeo‐detachment. Fluids were channelized along mafic dykes and sills acting as preferential drains. Warm carbonation (~130°C) is the latest hydrothermal record. We propose that this system is an analog to the root zone of present‐day serpentinite‐hosted hydrothermal systems such as those found along the Mid‐Atlantic Ridge.