Unravelling the root zone of ultramafic‐hosted black smokers‐like hydrothermalism from an Alpine analog

Rémi Coltat (1) , Yannick Branquet (1, 2, 3) , Pierre Gautier (1) , H. Campos Rodriguez (1) , Marc Poujol (1) , Ewan Pelleter (4) , Sean Mcclenaghan (5) , Gianreto Manatschal (6) , Philippe Boulvais (1)

1 GR - Géosciences Rennes
2 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
3 Métallogénie - UMR7327
4 IFREMER - Institut Français de Recherche pour l'Exploitation de la Mer
5 Trinity College Dublin
6 IPGS - Institut de physique du globe de Strasbourg

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 Accepted Article This article is protected by copyright. All rights reserved Jurassic-aged mineralized system is exposed in 3D. Serpentinites host a Cu-Fe-Ni-Co-Zn-rich mineralization made of sulfides, 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 paleo-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.

Domains: Geochemistry; Mineralogy

Rémi Coltat, Yannick Branquet, Pierre Gautier, H. Campos Rodriguez, Marc Poujol, et al.. Unravelling the root zone of ultramafic‐hosted black smokers‐like hydrothermalism from an Alpine analog. Terra Nova, 2019, 31 (6), pp.549-561. ⟨10.1111/TER.12427⟩. ⟨insu-02294388⟩