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File:Pelagite (deep seafloor manganese nodule) (Pacific Ocean) 2.jpg

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Summary

Description
English: Pelagite (deep seafloor manganese nodule) from the Pacific Ocean seafloor. (8-9 mm thick)

Some portions of the deepest seafloors of the world have common to abundant, dark-colored, manganese-rich nodules. These are called pelagites. They were first discovered in the 1860s in the Kara Sea. They are composed of various Mn, Fe, Cu, Ni, and Co minerals. Some materials commonly identified in these nodules include todorokite ((Mn,Ca,Mg)Mn3O7·H2O), birnessite (~Na4Mn14O27·9H2O), amorphous hydrous Fe-hydroxyoxides, goethite, detrital volcanic aluminosilicates, zeolites, etc. Pelagites are surprisingly lightweight for their size, and do not have the look & feel of “normal rocks”.

Manganese nodules grow extremely slowly, estimated at ~5 mm per million years. Cross-sections show irregular concentric layering. They appear to form intermittently, rather than by continuous accretion of layers.

Manganese nodule formation is not well understood. Unsolved problems include: 1) explaining how they stay at the seafloor surface, even where sedimentation rates exceed nodule growth rates; and 2) larger nodules appear to grow more quickly. More than one growth mechanism may be involved in the genesis of manganese nodules around the world.

The pelagite specimen shown above is broken so that it shows a cross-section through its center. Irregularly concentric banding is visible, apparently nucleated around an orangish-brown rock fragment.
Date
Source https://www.flickr.com/photos/jsjgeology/14953810507/
Author James St. John

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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/14953810507. It was reviewed on 19 March 2021 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0.

19 March 2021

Captions

Example of manganese nodule that can be founded on the sea floor

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4 September 2014

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current16:51, 19 March 2021Thumbnail for version as of 16:51, 19 March 20211,390 × 666 (224 KB)Joq OliverUploaded a work by James St. John from https://www.flickr.com/photos/jsjgeology/14953810507/ with UploadWizard

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