The SUSTAIN-ICDP Drilling Project on Surtsey

Abstract

In 1963, a submarine eruption was observed off the south coast off Iceland. Eruptive activity continued until 1967 and subsequently the island of Surtsey was born. In 1968, the first indications of hydrothermal activity were observed on the surface of the island. In 1969, the first signs of palagonitization of the basaltic glass were spotted. In 1979, a vertical drill hole (SE-01, 181 m) was cored. Studies of the core revealed that the Surtsey tephra had undergone a progressive alteration resulting in advanced lithification. In the seawater-dominated hydrothermal system, primary basaltic glass experiences intensive palagonitization and formation of secondary minerals, including analcime and phillipsite. In 2015, an international research group initiated a new drilling project on Surtsey, where one of the aims was to study the time-lapse evolution of the hydrothermal system and the associated mineralogical, geochemical, and microbiological processes. In July – September 2017, three cored boreholes were drilled on Surtsey by the International Continental Scientific Drilling Program-supported SUSTAIN drilling project. Two vertical holes (SE-02a, SE-02b), 152 and 192 m deep, respectively, are parallel and adjacent ( less than 8 m distance) to the 1979 (SE-01) borehole. In addition, a 35° angled cored borehole (SE-03) was drilled from the same drilling platform to the west, under the Surtur I crater. This core extends to a measured depth of 354 m, which corresponds to a vertical depth of about 290 m. Wireline downhole logging was carried out in SE-02b before installation of a Surtsey Subsurface Observatory for in situ incubations experiments. Core processing took place on the nearby island of Heimaey during the drilling operation in August-September and at the Icelandic Institute of Natural History, near Reykjavík, in October-November. Observation of the newly retrieved core material indicate that the consolidation of the Surtsey tephra has progressed since 1979 by ongoing palagonitization of basaltic glass, alteration of primary magmatic olivine and plagioclase and the formation of secondary minerals including clay minerals and zeolites.