Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85°E
Figure S3: Distance along the seafloor of logged lava surface coloration by seafloor feature. (116.7Kb)
Figure S4: Distance along the seafloor of logged lava surface texture by seafloor feature. (117.4Kb)
Figure S5: Distance along the seafloor of logged lava surface ornamentation by seafloor feature. (121.2Kb)
Figure S6: Distance along the seafloor of logged pyroclastic deposit coverage by seafloor feature. (119.8Kb)
Figure S7: Distance along the seafloor of logged microbial mat coverage by seafloor feature. (116.7Kb)
Figure S8: Bar graphs depict the clast morphologies observed through the sorting of ∼1200 clasts from slurp-sampled volcaniclastic deposits, for Sample 12-1. (122.7Kb)
Figure S10: A diagram of the model space for calculations of melt accumulation timescales as presented in Appendix A. (7.943Kb)
Pontbriand, Claire W.
Soule, Samuel A.
Sohn, Robert A.
Humphris, Susan E.
Kunz, Clayton G.
Shank, Timothy M.
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We use high-definition seafloor digital imagery and multibeam bathymetric data acquired during the 2007 Arctic Gakkel Vents Expedition (AGAVE) to evaluate the volcanic characteristics of the 85°E segment of the ultraslow spreading Gakkel Ridge (9 mm yr−1 full rate). Our seafloor imagery reveals that the axial valley is covered by numerous, small-volume (order ~1000 m3) lava flows displaying a range of ages and morphologies as well as unconsolidated volcaniclastic deposits with thicknesses up to 10 cm. The valley floor contains two prominent volcanic lineaments made up of axis-parallel ridges and small, cratered volcanic cones. The lava flows appear to have erupted from a number of distinct source vents within the ~12–15 km-wide axial valley. Only a few of these flows are fresh enough to have potentially erupted during the 1999 seismic swarm at this site, and these are associated with the Oden and Loke volcanic cones. We model the widespread volcaniclastic deposits we observed on the seafloor as having been generated by the explosive discharge of CO2 that accumulated in (possibly deep) crustal melt reservoirs. The energy released during explosive discharge, combined with the buoyant rise of hot fluid, lofted fragmented clasts of rapidly cooling magma into the water column, and they subsequently settled onto the seafloor as fall deposits surrounding the source vent.
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q10005, doi:10.1029/2012GC004187.
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