Seamount phosphorites

Parker and Siesser, 1972). (b)-(f) Scatter diagrams of selected elements for additional samples from Namibia (Watkins et ah, 1995), East Australia (O Brien et ah, 1990), Peru and Chili (Burnett, 1977), as well as seamount phosphorites from the equatorial Pacific (Hein et al., 1993). The dotted lines in (b) and (c) are the slopes for shale. The dotted lines in (d) and (e) are slopes for carbonate fluorapatites with possible formulas of Nao.5Ca5(P04)2.s (C03)F... 

CFA is omnipresent in pelagic sediments, ferromanganese nodules, and seamount crusts, and marine phosphorites on continental margins and seamounts. Supply of phosphate by oxidation of organic matter and pre-concentration of phosphate by iron oxyhy dr oxides, supply of calcium by dissolution of carbonates or carbonates acting as substrates, and supply of fluorine from seawater are all important factors in the formation of marine phosphorites. 

Figure 5 Photograph of a ferromanganese crust on a phosphorite substrate recovered from the summit of Schumann seamount, north of Kauai, Hawaii. Note the inclusions of altered basalt clasts from the seamount within the phosphorite, which has likely replaced limestone. (From G. McMurtry and D. L. VonderHaar, unpublished data.)...

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