Gakkel Ridge, Arctic Ocean

The Gakkel ridge stretches 1,800 km across the Eurasian basin of the Arctic Ocean (Fig. 1), and occupies a unique and important place within the global system of mid-ocean ridges. It is the slowest spreading significant length of ridge; it is the deepest ocean ridge and appears to be the ridge above the coldest upper mantle; it is the sole region where polar mantle compositions can be sampled directly; it has a unique tectonic setting surrounded by continental lithosphere in close proximity; and its strike is perpendicular to spreading direction, resulting in very few transform offsets. Because it contains a combination of many of the "forcing functions" that control the creation of oceanic crust, it thereby provides a unique natural laboratory within which to test numerous hypotheses.

Figure 1. Bathymetric map of the Arctic Ocean Basin, with full length of Gakkel ridge. The AMORE cruise mapped a portion of the ridge (black box). Green/brown = land, white = continentral shelf, yellows to blues = ocean depth. Map generated by GeoMapApp.

            Since the AMORE expedition in 2001, the Langmuir Lab has collected an extensive dataset of major element and trace element rock data. This data, along with isotopic compositions from LDEO (Goldstein), volatile data from Univ. of Tulsa (Michael), and helium isotopic values from Oregon State Univ. (Graham), will serve to help us better understand the petrologic and volcanic evolution of the Arctic Ocean floor, and how this ultraslow spreading environment may or may not be different from other global spreading environments. To date, this expedition has resulted in two published papers regarding rock chemistry. The first is a general overview paper of the Gakkel ridge (Michael et al., 2003), which reports the main observational findings of the 2001 AMORE venture, including three distinct morpho-tectonic sections of the ridge, distinct lava chemistry in each of these three sections, an unexpected abundance of hydrothermal activity, and the overall success of conducting a full-scale sampling expedition in ice covered waters. Recently, the second publication from our working group (Goldstein et al., 2008) uses the isotope data to generate an Arctic Basin evolutionary model that explains the variable basalt isotopic compositions as resulting from a fundamental difference in the generation and mineralogy of the mantle beneath the western versus the eastern part of the Gakkel ridge. The Langmuir group is currently working towards a manuscript that will test this model from the perspective of the major and trace element basalt compositions, and also discuss how the along-strike variations in rock chemistry are generated and why we see distinct geographical groups.

Aside from the scientific achievements of the AMORE cruise, the multi-nation, two-ship expedition was a tremendous adventure for all scientists involved. From the first time we earily entered the Arctic ice, to watching polar bears race across the ice, to visiting 90? N, there was never a dull moment in the two month long trip. Click on this link for a slide show of some of the highlights!


Related Lab Publications

Goldstein, S.L., G. Soffer, C.H. Langmuir, K. Lenhert, D.W. Graham, P.J. Michael, Origin of a "Southern Hemispheric" geochemical signature in the Arctic upper mantle, Nature 453, 89-93 (2008). (pdf)

Michael, P. J., C.H. Langmuir, H.J.B. Dick, J.E. Snow, S.L. Goldstein, D.W. Graham, K. Lenhert, G. Kurras, W. Jokat, R. Muhe, and H.N.Edmonds, Magmatic and amagmatic seafloor generation at the ultraslow spreading Gakkel ridge, Arctic Ocean, Nature 423, 956-961 (2003). (pdf)


Other Related Publications

Baker, E.T., H.N. Edmonds, P.J. Michael, W. Bach, H.J.B. Dick, J.E. Snow, S.L. Walker, N. R. Banerjee, and C.H. Langmuir, Hydrothermal venting in magma deserts: The ultraslow spreading Gakkel and Southwest Indian Ridges, Geochemistry, Geophysics, and Geosystems 5 (8), pp. 29 (2004). (pdf)

Dick, H.J.B., J. Lin, and H. Schouten, An ultraslow spreading class of ocean ridge, Nature 426, 405-412 (2003). (pdf)

Edmonds, H.N., P.J. Michael, E.T. Baker, D.P. Connelly, J.E. Snow, C.H. Langmuir, H.J.B. Dick, R. Muhe, C.R. German and D.W. Graham, Discovery of abundant hydrothermal venting on the ultraslow spreading Gakkel ridge in the Arctic Ocean, Nature 421, 252-256 (2003). (pdf)

Hellebrand, E., J.E. Snow, S. Mostefaoui, and P. Hoppe, Trace element distribution between othropyroxene and clinpyroxene in perodotites from the Gakkel Ridge: a SIMS and NanoSIMS study, Contributions to Mineralogy and Petrology 150(5), 486-504 (2005). (pdf)

Hellebrand, E., J.E. Snow, and R. Muhe, Mantle melting beneath Gakkel Ridge (Arctic Ocean): abyssal peridotite spinel compositions, Chemical Geology 182, 227-235 (2002). (pdf)

Jokat, W. and M.C. Schmidt-Aursch, Geophysical characteristics of the ultraslow spreading Gakkel Ridge, Arctic Ocean, Geophysical Journal International 168 (3), 983-998 (2007). (pdf)

Jokat, W., O. Ritzmann, M.C. Schmidt-Aursch, S. Drachev, S. Gauger, and J. Snow, Geophysical evidence for reduced melt production on the Arctic ultraslow Gakkel mid-ocean ridge, Nature 423, 962-965 (2003). (pdf)

Schlindwein, V., C. Muller, and W. Jokat, Seismoacoustic evidence for volcanic activity on the ultraslow spreading Gakkel Ridge, Arctic Ocean, Geophysical Research Letters 32, doi:10.1029/2005GL023767 (2005). (pdf)


Manuscripts in Prep

Standish, J.J., C.H. Langmuir, P.J. Michael, D.W. Graham, C. Rotman, Melting beneath the coldest and deepest MOR, Gakkel ridge, Journal of Petrology, (in prep).

 

 

NSF

The research listed above is supported by the National Science Foundation, Office of Polar Programs.

 


Copyright © 2008 The Langmuir Group
Last Updated: 10-21-08