Lead
Ultramafic rocks are tectonically emplaced along major, large-scale offset normal faults (detachment faults) and are important components of the seafloor at slow spreading ridges. In these environments oceanic detachment faults lead to the formation of oceanic core complexes, which are characterized by extensive exposure of gabbro and serpentinized mantle rocks. Detachment faults zones also provide conditions for fluid flow and hydrothermal systems with varying temperatures of venting.

Lay summary

The interaction of seawater with mantle rocks exposed on the seafloor results in serpentinization, which is a fundamental process that has geophysical, geochemical and biological importance for the global marine system and for subduction zone processes. A number of the Tethyan ophiolites in the Alps and northern Apennines are now considered relicts of oceanic lithosphere and contain lower crustal and upper mantle sequences that are believed to have been exposed by detachment faults onto the seafloor. This project is a continuation of SNF project No 200021-134947 (2011-2013) to complete the PhD thesis work of Monica Vogel. The aim of this project is to study the links among fluid-rock interaction, hydrothermal deposits and deformation processes recorded in the Jurassic Bracco-Levanto and Val Graveglia ophiolite complexes in Liguria (Italy) and to compare these processes to modern oceanic hydrothermal systems hosted in ultramafic and gabbroic rocks along the Mid-Atlantic Ridge (MAR). We will conduct petrological, major element, trace element and isotopic (O, C, Sr) analyses of basement rocks and the hydrothermal deposits in Liguria to investigate fluid flow paths, mass transfer, and fluid fluxes during high and low temperature hydrothermal activity, with emphasis on processes leading to the formation of carbonate-vein systems in serpentinites, so-called ophicalcites. We will compare these data to new and published data from the MAR and from the Lost City hydrothermal field. This comparative study will provide a better understanding of evolving, subsurface processes in serpentinite-hosted hydrothermal systems and will contribute to a comprehensive, integrated model of end-member hydrothermal systems in oceanic sequences formed at slow spreading ridge environments.