Geochemistry of Lake Michigan manganese nodules

Samples have been analyzed for their iron, manganese, calcium, magnesium, sodium, potassium, inorganic carbon, organic carbon, and total nitrogen content. The nodules average 20% iron and 6% manganese. the trace metal content (copper, zinc, cobalt, and nickel) of the samples is considerably lower than that of marine material.

Interstitial water is one of the major contributors of manganese and iron for the growth of nodules in lake Michigan. Cores of green bay sediment show an inverse relationship between sedimentary and interstitial manganese with the sedimentary manganese increasing to a maximum at or near the sediment-water interface. Sedimentary iron remains fairly constant throughout the length of these cores while interstitial iron decreases slightly toward the sediment-water interface. in addition, lake water may be more than a passive contributor of iron and manganese.