Unusual Mineral Deposits Record the Unique History of the Arctic Ocean

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Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by shallow areas of continental shelf and deep basins with limited circulation. USGS scientists and their colleagues have published the first comprehensive paper on this subject.

This article is part of the November-December 2017 issue of the Sound Waves newsletter

The paper, titled “Deep water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean,” was published in the American Geophysical Union (AGU) journal Geochemistry, Geophysics, Geosystems (G-cubed).

Eleven coauthors contributed to this interdisciplinary study of ferromanganese (Fe-Mn) deposits from the Amerasia Basin in the Arctic Ocean. Their paper integrates geology, geochemistry, oceanography, seawater chemistry, regional tectonics, history of the Arctic, and more.

The authors analyzed Fe-Mn crusts and nodules collected in 2008, 2009, and 2012, and found them unusually enriched in the rare metal scandium. The researchers also analyzed water-column samples collected in 2015, focusing on scandium in both particulate and dissolved form. The Arctic Fe-Mn crusts and nodules are the only ones in the global ocean highly enriched in this rare metal, for which there is no land-based mine. Scandium is in great demand to amalgamate with aluminum to make light, fuel-efficient aircraft.

Bathymetry of the Arctic Ocean, with black rectangle delineating the study area.

Bathymetry of the Arctic Ocean, with black rectangle delineating the study area. White star marks site where sample in photograph was collected. Its cut surfaces show layers in Fe-Mn crust. Each square in scale beneath sample is 1 centimeter (cm). Base map from International bathymetric chart of the Arctic Ocean (IBCAO). Image credit: James Hein, USGS

The Arctic Fe-Mn crusts have many unique characteristics besides high scandium, all unlike any other crusts found elsewhere, and those characteristics reflect the history of the Arctic Ocean. For example, the Arctic crusts have unique mineral and chemical compositions compared with deposits found elsewhere: atypically high growth rates, high detrital contents, high Fe/Mn ratios, and low silicon/aluminum (Si/Al) ratios. High detritus reflects erosion of underwater outcrops and onshore rocks in North America and Siberia, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. High Fe/Mn ratios are attributed to the Arctic Ocean’s broad continental shelves, where chemical reactions release Fe to bottom waters that flow to the deeper basins.

Analyses of crust growth layers that accreted over the past 15 million years revealed changes in the crusts over time, such as a decrease in scandium concentration. The changes indicate that the Arctic crusts are becoming more like crusts from elsewhere in the global ocean as the Fe/Mn ratio and amount of detritus decrease.

To learn more, read the new paper, “Arctic Deep Water Ferromanganese-Oxide Deposits Reflect the Unique Characteristics of the Arctic Ocean.”

The full citation is:
Hein, J.R., Konstantinova, N., Mikesell, M., Mizell, K., Fitzsimmons, J.N., Lam, P., Jensen, L.T., Xiang, Y., Gartman, A., Cherkashov, G., Hutchinson, D.R., and Till, C.P., 2017, Arctic deep water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean: Geochemistry, Geophysics, Geosystems, https://doi.org/10.1002/2017GC007186.

 

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Date published: December 1, 2017

Sound Waves Newsletter - November-December 2017

Detailed new USGS study of a Hurricane Sandy-created breach at Fire Island, three new oceanographic time-series datasets released, San Clemente Dam removal field trip to the Carmel River for graduate students, WHCMSC participates in a variety of outreach opportunities, USGS scientists participate in annual SACNAS conference, and more in this November-December 2017 issue of Sound Waves....