Abstract
Abstract. The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963–1967. Two vertically cored boreholes, to 152 and 192 m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181 m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181 m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25–124 ∘C. A third cored borehole, inclined 55∘ in a 264∘ azimuthal direction to 354 m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100 m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25–141 ∘C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve.
Highlights
In late summer 2017, International Continental Scientific Drilling Program (ICDP) expedition 5059, the Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative Concretes (SUSTAIN) project, drilled three cored boreholes through the basaltic tuff, tephra, and minor intrusions of Surtsey volcano, an oceanic island on the insular shelf 32 km from the south coast of Iceland
The scientific and societal benefits of the SUSTAIN project will result from i. investigating explosive Surtseyan eruptive processes as a means to refine the predictions of hazards associated with the subaerial phases and rapid edifice growth of island-forming seafloor volcanoes; ii. describing chemical, magnetic, and material changes in the Surtsey deposits produced by hydrothermal– microbial–rock interactions, as a means to refine geophysical monitoring of thermal and chemical stimulation in hydrothermal reservoirs and the potential for fluid waste disposal and storage sites in pyroclastic rocks; and www.sci-dril.net/25/35/2019/
Every effort was made to fully preserve the sensitive surface and subsurface environments of the Surtsey Nature Reserve and to follow all guidelines set by the Iceland Environment Agency and Surtsey Research Society to avoid any risk to the vegetation, birds, and sea life that inhabit the island and the marine preserve that surrounds it. This special protection has been in place since 1965, with amendments made in 2006 and 2011, to ensure that the island and its geological formations, flora, and fauna evolve without human intervention
Summary
In late summer 2017, International Continental Scientific Drilling Program (ICDP) expedition 5059, the Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative Concretes (SUSTAIN) project (http: //surtsey.icdp-online.org, last access: 30 March 2019), drilled three cored boreholes through the basaltic tuff, tephra, and minor intrusions of Surtsey volcano, an oceanic island on the insular shelf 32 km from the south coast of Iceland. Initial results of 16S rDNA tag sequencing analysis of fluids extracted in 2009 from the submarine zone of the 1979 borehole contain unique sequences of bacteria, archaea, and viruses with icosahedral symmetry below a 140 ◦C (1980) temperature maxima at 100 m depth below the ground surface (Marteinsson et al, 2015) These indicate methanomicrobia-related sequences at 172 m (54 ◦C in 2009) and archaeoglobus-like sequences at 145 m (80 ◦C in 2009) (Fig. 2). Zones of the hydrothermal system (Türke et al, 2019); and (4) further investigate the deep structure of the volcano with a cored borehole inclined below Surtur, the eastern crater, which could potentially intersect the pre-eruption seafloor (Fig. 5)
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