Travertines from the Troll thermal springs, Svalbard

The Troll and Jotun hot springs are located along the Bockfjorden fault zone at 79°23’N on Svalbard and represent the northernmost thermal springs documented on land. They are recharged through subpermafrost aquifers supplied mainly by glacial meltwater and derive their Ca and CO 2 contents from Proterozoic marbles. Gases exsolved from the 25-28°C hot spring waters are N 2 and CO 2 -dominated with high contents of He (reaching 1.5% in the Jotun springs) and Ar. The temperature distribution and temporal variation in the main Troll spring have been constrained by IR-photography and by temperature loggers embedded in the springs and associated, water-filled travertine pools over a period of one year. High-resolution micro-drilling techniques have allowed detailed stable isotope profiles to be obtained from selected travertine cross-sections. The data reflect seasonal fluctuations in temperatures during travertine growth and constrain the travertine growth rate. Most of the travertine growth occurs during the summer season as most of the flooded travertine pools were probably frozen for about 6 months per year. Oxygen isotope variations among the travertine terraces partly reflect fluctuations in the spring source composition. These fluctuations have been used to constrain the temporal evolution of the terrace system.