Auxiliary Material for Paper 2012GC004187


Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85degE

Claire W. Pontbriand
MIT-WHOI Joint Program in Oceanography, Woods Hole, Massachusetts, USA

S. Adam Soule, Robert A. Sohn, Susan E. Humphris, Clayton Kunz, and Hanumant Singh
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA

Ko-ichi Nakamura
Institute of Geology and Geoinformation, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

Martin Jakobsson
Department of Geological Sciences, Stockholm University, Stockholm, Sweden

Timothy Shank
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA


Pontbriand, C. W., S. A. Soule, R. A. Sohn, S. E. Humphris, C. Kunz, H. Singh, K. Nakamura, M. Jakobsson, and T. Shank (2012), Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85degE, Geochem. Geophys. Geosyst., 13, QXXXXX, doi:10.1029/2012GC004187.


Introduction:

The supplementary files present information and analyses from of near-seafloor video and geologic
samples collected on the Arctic Gakkel Vents Expedition in 2007. Near-bottom imaging surveys were
conducted with the deep-towed Camera-Sampler (CAMPER) vehicle, a fiber-optic, wire-line vehicle that
is towed at nominal altitudes of 1.5 to 3 m above the seafloor. The CAMPER vehicle collected digital
video and still imagery, measurements of near-bottom water properties, and geologic and biological
samples on thirteen deployments at the 85°E site. Because the vehicle is operated from an idle ship
within the pack ice, its trajectory over the bottom is controlled by the direction and flow of the
local ice pack, with typical drift speeds of 0.15 to 0.3 knots. The multi-purpose vehicle was
outfitted with five standard and high-definition video cameras that streamed real-time video to the
ship via a fiber-optic cable. Conductivity-Temperature-Depth (CTD) and an Eh sensor for measuring the
oxidation-reduction potential of seawater were also mounted on the vehicle in order to identify the
presence of reduced (i.e., fresh) hydrothermal fluids. The Eh values presented in this paper are the
measured Pt electrode voltage against the Ag/AgCl reference electrode in saturated KCl solution. Eh
measurements can be converted to the redox potential of sweater, i.e., against the standard or normal
hydrogen electrode (SHE or NHE) by applying a temperature correction, but we do not make the
conversion because the electrodes on the moving CAMPER platform never reach equilibrium with seawater
[Nakamura et al., 2000].

1. 2012gc004187-fs01.pdf
Figure S1. Distance along the seafloor logged on each seafloor feature.

2. 2012gc004187-fs02.pdf
Figure S2. Distance along the seafloor of logged deposit type by seafloor feature.

3. 2012gc004187-fs03.pdf
Figure S3. Distance along the seafloor of logged lava surface coloration by seafloor feature.

4. 2012gc004187-fs04.pdf
Figure S4. Distance along the seafloor of logged lava surface texture by seafloor feature.

5. 2012gc004187-fs05.pdf
Figure S5. Distance along the seafloor of logged lava surface ornamentation by seafloor feature.

6. 2012gc004187-fs06.pdf
Figure S6. Distance along the seafloor of logged pyroclastic deposit coverage by seafloor feature.

7. 2012gc004187-fs07.pdf
Figure S7. Distance along the seafloor of logged microbial mat coverage by seafloor feature.

8. 2012gc004187-fs08.pdf
Figure S8. Bar graphs depict the clast morphologies observed through the sorting of ~1200 clasts
from slurp-sampled volcaniclastic deposits, for Sample 12-1. Approximately 4
kg of unconsolidated volcaniclastic deposits were sampled from two sites on the axial valley seafloor
at 4000 m and 4116 m water depths respectively using a suction sampler on CAMPER.

9. 2012gc004187-fs09.pdf
Figure S9. Same as Figure S8 but for Sample 13-1.

10. 2012gc004187-fs10.pdf
Figure S10. A diagram of the model space for calculations of melt accumulation timescales as presented in
Appendix A.

11. 2012gc004187-ts01.docx
Table S1. Temperature and Eh anomalies detected by the CAMPER vehicle. Measured thermal anomalies represent potential temperature anomalies derived from absolute temperature, pressure and salinity measurements adjusted for an adiabatic displacement to a reference pressure of 3000 dbars [Bryden, 1973; Fofonoff & Millard, 1983; Baker et al., 1994].

12. 2012gc004187-ms01.mp4
Animation S1. Short clips of near-seafloor video collected on the Arctic Gakkel Vents Expedition in 2007. The position of CAMPER on the seafloor indicated on maps shown on the video was determined from ship GPS navigation, corrected for ship heading, and assuming an essentially vertical wire-line.


References

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Bryden, H. L. (1973), New polynomials for thermal expansion, adiabatic temperature gradient and
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Fofonoff, N. P., and R. C. Millard, Jr. (1983), Algorithms for computation of fundamental properties
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Nakamura, K., S. Veirs, C. P. Sarason, R. E. McDuff, F. Stahr, D. R. Yoerger, and A. M. Bradley
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