The Sr isotope geochemistry of oceanic ultramafic-hosted mineralizations

The source of metals involved in the formation oceanic ultramafic-hosted hydrothermal Cu-Fe-Co-Zn-Ni mineralization remains poorly constrained. Here, we focus on a fossil mineralized system preserved Platta nappe (SE Switzerland), where mantle rocks were exhumed along detachment faults to seafloor during Jurassic rifting. mineralization, associated with Fe-Ca-metasomatism (ilvaite-hydroandradite-diopside), represents an analogue root zone present-day systems formed at mid-ocean ridges (e.g., Rainbow field Mid-Atlantic Ridge). We apply Sr isotope geochemistry Fe-Ca silicates and secondary, alteration products that include serpentinites, altered mafic carbonated constrain source(s) characterize plumbing system. carbonates have ratios close seawater, suggesting near seafloor, seawater-dominated high fluid/rock ratios. 87Sr/86Sr lower than those seawater. In contrast, serpentinites display large range ratios, including values higher indicating long lived interactions multi-stage fluid infiltrations. These results suggest activity started final crustal thinning, when seawater percolated normal through hyper-thinned crust, acquiring before penetrating initiating serpentinization subcontinental rocks. At this early stage, was rock-dominated (i.e., low ratios), leading serpentinites. On their way-back uprising, serpentinization-derived fluids mixed resulting precipitation metal sulfides silicates, subsequent carbonation fluid-dominated Our study shows can be used identify reservoirs mineral deposits for characterization mineralizations.