by Marie Dolores Jackson, Magnús Tumi Gudmundsson, Wolfgang Bach, Andri Stefánsson, Viggó Thór Marteinsson, Steffen Leth Jørgensen, Piergiulio Cappelletti

Surtsey volcano, an isolated oceanic island and UNESCO World Heritage site, is a uniquely well-documented natural laboratory for investigating processes of rift zone volcanism, hydrothermal alteration and biological colonization of basaltic tephra, and development of industrial resources using palagonitic tuff as a prototype for sustainable, high performance concretes. The 181 m hole drilled in 1979 (Jakobsson & Moore 1986) provides a petrological, mineralogical, and thermal framework to understand early eruptive and hydrothermal processes in tephra and feeder dikes and the structure of the volcano above and below sea level. Subsurface microbiota have now been observed in fluids extracted below the 120 °C thermal barrier of microbial life. The SUSTAIN drilling program (Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative Concretes) will be based on two cored holes, designed to protect the sensitive wildlife and vegetative habitats of the Surtsey Natural Reserve. A clean 200-meter-deep vertical hole with anodized aluminum casing would explore pore water chemistry, microbiota-water-rock interactions, and seawater compositional modifications over time. After drilling, a "Surtsey Subsurface Observatory" would be installed in this hole for long term monitoring and in situ experiments. A 300-meter-long angle hole with steel casing inclined west toward the eastern volcanic vent axis would intersect dike intrusions, provide additional information on deep stratigraphy and structure, and investigate higher temperature zones of the hydrothermal system. The SUSTAIN drilling program would be the first to sample microbial colonization of tephra, together with its pore water, through a neo-volcanic island from the surface to the seafloor with all precautions taken to avoid contamination from the surroundings. Investigations of cores would further clarify the internal structure and facies architecture of the type locality of Surteysan volcanism, and provide a reference for thermal granulation experiments to refine models for explosive magmatic and phreatomagmatic fragmentation and production of airborne ash clouds. Time lapse monitoring of live hydrothermal system and its fluid geochemistry, permeability and microbial activity would describe the evolution of microstructures and rock physics properties of tobermorite and zeolite tuffs, and provide a geological analog for highly durable Roman seawater-pyroclastic rock concrete. The unique and distinguishing feature of the drilling program is to apply volcanological, geochemical, mineralogical, microbiological and geoarchaeological perspectives to create a new diagenetic and biogenetic paradigm for pyroclastic rock concretes with cation-exchange properties and long term societal benefits for human and earth ecology. Jakobsson, S., and Moore, J. G. (1986) Hydrothermal minerals and alteration rates at Surtsey volcano, Iceland. GSA Bulletin, 97, 648–659.

• The principal scientific objective of new drilling of Surtsey is to describe how hydrothermal diagenetic and biogenetic seawater-rock processes evolve in an extremely well-constrained basaltic system that has great relevance to the growth, lithification, and longevity of rift zone islands, the processes of indigenous microbial colonization and succession in the subsurface geobiosphere, and the cementitious systems of concretes for waste encapsulations and harsh environmental applications. Specific objectives include:
• 1) To refine the original structure of the volcano and heat transfer in the 50-year-old hydrothermal system to clarify processes of tephra lithification, since it is progressive formation of tuff, rather than capping lavas, that harden Surtsey against incessant marine erosion;
• 2) To use volcanic facies, grain size and vesicularity analysis as a reference for thermal granulation experiments to refine models for explosive magmatic and phreatomagmatic fragmentation and production of airborne ash clouds;
• 3) To precisely describe hydrothermal-seawater-rock interactions – palagonitization, microbial interaction, and authigenic mineral crystallization – as a function of proximity to the dike swarm heat source, and to determine how time, temperature variation, and aqueous environment influence a) the evolving material and physical properties of altered tephra and lithified tuff, and b) the compositions, crystal chemistry, and cation-exchange properties of Al-tobermorite and zeolite assemblages above and below sea level;
• 5) To explore how processes of chemosynthetic life evolve in extreme temperature conditions through coupled microbiological and pore fluid geochemical sampling and analysis during drilling, and through eventual development of the "Surtsey Subsurface Observatory" for monitoring, sampling and in situ experimental research describing the long term evolution of microbiological-seawater-rock-interactions.

Basalt, Europe, Hydrothermal Alteration, Iceland, Microbial Life, Rift Zone Volcanism, Surtsey, SUSTAIN, Tuff

Latitude: 63.30219, Longitude: -20.61002