A combined petrological, geochemical and geochronological study of the magmatic rocks surrounding the Logatchev hydrothermal field.

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For the last period of the SPP we suggest a joint research project of (experimental) petrology and igneous geochemistry in order to study the magmatic rocks in the region of the Logatchev hydrothermal field. A large number of samples is accessible or will be collected which we can use to study the transport of magmas (and energy) from the mantle to the crust, the formation of the crust, and the interaction between the magmatic rocks and hydrothermal fluids. Petrological, geochemical and isotopic analysis of plutonic and volcanic rocks from the Logatchev field will establish their relationship and depth of crystallization. To achieve these goals, different approaches are used: (1) phase equilibria are modeled in a wide range of αH2O and fD2 and include equilibrium, fractional, and polybaric crystallization calculations; (2) glass inclusions in minerals are investigated to understand the behavior and importance of volatiles in differentiation processes and during ascent; (3) gabbros are investigated to constrain depth and temperature of the differentiation process based on natural samples in comparison with the results from the theoretical simulations. Petrologic and geochemical studies of the magmatic rocks will reveal reactions with hydrothermal fluids, which may have led to crustal remelting and assimilation. Uranium series dating will yield age estimates of the volcanic processes and thus of the timing of magma ascent to the surface as possible heat sources. This project will thus represent an essential link within the SPP between the magmatic processes in the mantle and crust and the hydrothermal processes at the seafloor and the shallow crust.