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Our transcription: Manganese nodules are not composed purely of manganese. Only about 20 percent of a nodule contains manganese. Another 15 percent or so may contain iron with traces of cobalt, nickel, and other metals, but most of the nodules are made up of calcium carbonate and volcanic fragments. Where the manganese comes from has been a mystery, a problem for science. Two possibilities are that the manganese is extracted from waters washing off the continents, or from exhalations through undersea hot springs in the mid-ocean ridges. The mid-ocean ridge origin is favored, but how the manganese is transferred through the water to very slowly accumulate as these nodules nucleate in the sea floor is in detail unknown.
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