Major and trace elements of the saline fluids at the Outokumpu deep drilling site - the role of the hydrolysis of rocks and of fluid inclusions

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Deep saline fluids are a common feature of cratons. One aim of the new, already completed Finnish research borehole at Outokumpu, which is an approved project of the International Continental Drilling Program, is the understanding of sources, flow dynamics, chemical composition and evolution, and the biosphere of deep, saline fluids of the Scandinavian shield. This proposed project consists of a work package, which is agreed between the Outokumpo research group, to the overall project by studing the involvement and relative importance of two possible fluid sources. One source may be due to the leakage of fluid inclusions, of which in-situ trace and major element compositions will be analysed by Laser-ICP-MS. Additional fluid inclusion fingerprints, namely oxygen and carbon isotopes will be determined with the aid of a coupled online-pyrolysis-GC-MS technique. The chemical characteristics together with micro-thermometry data will be used to gain information on the origin and physico-chemical conditions of the fluid inclusions. As a further source, the hydrolysis of the rock minerals will be investigated employing diffusion cells and column experiments at constant temperatures up to 90°C on cored samples. Overall rate constants of the release of major and trace elements will be calculated from those experiments.