The hydrothermal contribution to the oceanic strontium budget : insights from the Oman ophiolite

• Main Author: Davis, A. C.
• Published: University of Cambridge 2004
• Subjects: 551.9
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598391

This study uses the strontium isotope tracer system to constrain hydrothermal flux estimates and investigate the hydrothermal contribution to the oceanic strontium budget. This is achieved through a multi-directional approach. Firstly, strontium isotope data for ocean and ophiolite crust are compiled to investigate the degree of isotopic alteration displayed by modern and ancient crustal profiles; and calculate the cumulative hydrothermal contribution to the oceanic strontium budget. This reveals an apparent imbalance in the oceanic strontium budget, because the hydrothermal contribution calculated is only a third of that required to balance a revised riverine input and the buffering effect of carbonate digenesis. Secondly, a multi-phase hydrothermal system in the northern Oman ophiolite is investigated as an analogue for understanding modern oceanic process and the magnitude of hydrothermal fluxes in arc-related environments. Field mapping and trace elements discrimination methods are combined to identify three hydrothermal regimes which correlate with the complex magmatic-tectonic evolution of the area. The first regime is associated with formation and cooling of the crustal sequence within an oceanic spreading environment; the second and third regimes are associated with later magmatism in an off-axis environment. Strontium isotope geochemistry is used to investigate the character of each regime and predict a time-integrated high-temperature fluid flux of ~4.5±1.1 x 10⁷ kg m^-2 for the initial spreading related hydrothermal event and lower estimates for the later regimes. The flux calculated is significantly higher than a similar prediction made for mid-ocean ridge systems (eg. Teagle et al, 2003), supporting previous suggestion that oceanic spreading systems in supra-subduction settings support greater hydrothermal fluxes than normal oceanic environments.