Evidence of recent, off-axis volcanism on Gakkel Ridge, Arctic Ocean

In 1998 and 1999 the Science and Ice Exercise (SCICEX) programs used interferometric sonars installed on a U.S. Navy nuclear-powered submarine to map the morphology, texture and crustal structure of Gakkel Ridge from 6° E to 96° E with coverage out to ~50 km from the ridge axis (Edwards et al., 2001; Cochran et al., 2003). This effort represented the most comprehensive, systematic survey of this important end-member ridge on the spreading rate spectrum (Cochran et al., 2003). The SCICEX programs were followed by the Arctic Mid-Ocean Ridge Expedition (AMORE) in 2001 which used both the USCGC Healy and PFS Polarstern to map the axial valley floor and walls along Gakkel Ridge at high resolution (Michael et al., 2003; Jokat et al., 2003) from the Lena Trough to an inferred active volcanic construrct at 85°E (Müller and Jokat, 2000; Edwards et al., 2001). We have used the GPS-navigated AMORE data to refine the navigation of the SCICEX data, extending the coverage of both the SCICEX and AMORE datasets and improving the resolution and positional accuracy of the SCICEX data. The integrated dataset allows identification of several reflective, and thus relatively recent, off-axis lava flows. These flows are analogous to off-axis eruptions that have been reported on the Southwest Indian Ridge [Standish and Sims, 2010]. Several of the flows on Gakkel Ridge originate along fissures located at or near the top of the axial valley walls and spill down onto the axial valley floors. Other flows are associated with small (a few hundred meter or less in diameter) constructs contained entirely within the axial valley. We present a comparison of the integrated topographic and textural data with the results of dredge samples recovered during the AMORE expedition to document the petrology and relative age of these flow features. We further use the morphology of the reflective flow features, in combination with tectonic interpretations of the local terrain, to demonstrate the eruptive source.