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Cacoxenite in Miocene Sediments of the Maryland Coastal Plain

Published online by Cambridge University Press:  02 April 2024

Paul P. Hearn Jr.
Affiliation:
U.S. Geological Survey, Reston, Virginia 22092
Lucy McCartan
Affiliation:
U.S. Geological Survey, Reston, Virginia 22092
David R. Soller
Affiliation:
U.S. Geological Survey, Reston, Virginia 22092
M. Dennis Krohn
Affiliation:
U.S. Geological Survey, Reston, Virginia 22092
Virginia M. Gonzalez
Affiliation:
U.S. Geological Survey, Reston, Virginia 22092
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Abstract

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Cacoxenite having the composition (Al4.0Fe22.5O7.1(OH)14.3(PO4)17(H2O)23.7)·50.3H2O was identified in a bed of mature quartz sand in the Miocene Calvert Formation near Popes Creek, Maryland. This is the first reported occurrence of this mineral in Atlantic Coastal Plain sediments north of Florida. The cacoxenite occurs as silt-size to sand-size grains, both as irregularly shaped aggregates and as radiating arrays of delicate acicular crystals. The presence of discrete cores and overgrowths in some grains indicates at least two generations of crystal growth. Electron microprobe analyses reveal excess Si and Al (relative to the ideal composition), which is believed to reflect ultra-fine clay particles within the cacoxenite grains. Admixed clays probably served as a substrate for the formation of ferric oxyhydroxides, which were subsequently converted to cacoxenite through the addition of dissolved phosphorus.

Type
Research Article
Copyright
Copyright © 1988, The Clay Minerals Society

References

Bricker, O. P. and Troup, B. N., 1975 Sediment-water exchange in the Chesapeake Bay Estuarine Research 1 327.Google Scholar
Carroll, D., 1958 Role of clay minerals in the transportation of iron Geochim. Cosmochim. Acta 14 127.CrossRefGoogle Scholar
Hearn, P. P., Parkhurst, D. L. and Callender, E., 1983 Authigenic vivianite in Potomac River sediments: control by ferric oxyhydroxides J. Sed. Petrol. 53 165177.Google Scholar
Hunt, G. R. and Salisbury, J. W., 1970 Visible and nearinfrared spectra of minerals and rocks. I. Silicate minerals Modern Geology 1 283300.Google Scholar
Jackson, M. L., 1975 Soil Chemical Analysis—Advanced Course 2nd ed. Wisconsin University of Wisconsin, Madison.Google Scholar
Johns, W. D., Grim, R. E. and Bradley, W. F., 1954 Quantitative estimations of clay minerals J. Sed. Petrol. 24 242251.Google Scholar
McCartan, L., Lemon, E. M. Jr. and Weems, R. E. (1984) Geology of the area between Charleston and Orangeburg, South Carolina: U.S. Geol. Surv. Map I–1472.Google Scholar
Moore, P. B. and Shen, J., 1983 An X-ray structural study of cacoxenite, a mineral phosphate Nature 306 356358.CrossRefGoogle Scholar
Nriagu, J. O., 1972 Stability of vivianite and ion-pair formation in the system Fe3(PO4)-2H3PO4-H2O Geochim. Cosmochim. Acta 36 459470.CrossRefGoogle Scholar
Nriagu, J. O. and Dell, C. I., 1974 Diagenetic formation of iron phosphates in recent lake sediments Amer. Mineral. 59 934946.Google Scholar
Nriagu, J. O. and Moore, P. B., 1984 Phosphate Minerals New York Springer-Verlag.CrossRefGoogle Scholar
Owens, J. P., Hess, M. M., Denny, C. S. and Dwomik, E. J. (1983) Postdepositional alteration of surface and near-surface minerals in selected Coastal Plain Formations of the middle Atlantic States: U.S. Geol. Surv. Prof. Pap. 1067–F, 45 pp.Google Scholar
Piercey, E. J., 1981 Phosphate sorption on clay-rich channel sediments of the tidal Potomac River and estuary Estuaries 4 251.Google Scholar
Sherman, D. M., Bums, R. C. and Bums, V. M., 1982 Spectral characteristics of the iron oxides with application to Martian bright region mineralogy J. Geophys. Res. 87 1016910180.CrossRefGoogle Scholar