3rd Floor Meeting Room
Barbara Kleine (Institute of Earth Sciences)
Title: Fluxes, transport, interaction – Tracking fluids through the crust
Date: Friday, 12th October
Place: 3rd Floor meeting room, Askja
Abstract: Fluids play a critical role in the evolution and modification of the Earth’s crust. They control mineral reactions, heat and mass transfer. In subduction zones, large amounts of fluids may be released from the downgoing slab by dehydration and decarbonation reactions. In these systems, fast flowing CO2-bearing fluids provide a unique mechanism of preserving high pressure mineral assemblages. Such fluid fluxes can be extremely fast implying that metamorphic fluid flow might be a short-term phenomenon which is capable of influencing surface systems on societally-relevant timescales.
Large amounts of fluids can be also mobilized in hydrothermal systems along mid-ocean ridges leading to extensive alteration of the crust. Progressive fluid-rock interaction may strongly affect elemental cycles (O, H, S, Si, C) in such systems. While in subduction zones, studying the mineralogy of the rocks is essential to understand fluid flow patterns, stable isotope systematics of thermal fluids and minerals have been found to be a useful tool to unravel alteration processes and origins of fluids in hydrothermal systems. For example, isotope modelling revealed that observed large Si and O isotope variations in quartz are consistent with variable water sources and equilibrium isotope fractionation between fluids and quartz associated with secondary processes occurring in the Icelandic crust including fluid-rock interaction, boiling and cooling.
In this seminar, I will present natural data that is used to constrain fluid movement in mid-ocean ridge systems and subduction zones. In addition, the natural data will be tested by applying thermodynamic and geochemical modelling to investigate fluid-rock interaction processes in the crust. Understanding the processes that occur in these two diverse systems may help us to link elemental cycles from one extreme environment to the other.
All are welcome.