Geochemistry of gases in spring waters along the Alpine Fault, South Island of New Zealand

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The Alpine Fault on the South Island of New Zealand is a major feature, showing a NE movement of 27 mm/yr and rapid uplift although no major earthquakes have occurred in historic time. In the context of the ICDP project for scientific drilling into the Alpine Fault, we propose a regional investigation of the composition of gases emanating from spring waters on both sides of the fault. The study aims at characterizing the gas sources in both the mantle and the crust and at revealing the processes that may have modified the gas compositions. In particular, we plan to explore whether there are any systematic compositional differences on the northwest and southeast sides of the Alpine Fault, respectively. To do this, we will determine the abundances of major and trace gas components (CO2, N2, CH4, Ar, He etc.) and the elemental and isotopic compositions of the noble gases (He, Ne, Ar, Kr, Xe) in free or dissolved spring gases. Our data will serve as a basis of comparison for results obtained during drilling.