Hostname: page-component-77c89778f8-vpsfw Total loading time: 0 Render date: 2024-07-22T00:06:54.071Z Has data issue: false hasContentIssue false
  • English
  • Français

Microstructure, Mineralogy and Chemistry of Cambrian Glauconite Pellets and Glauconite, Central U.S.A.

Published online by Cambridge University Press:  01 July 2024

I. Edgar Odom
I. Edgar Odom*
Affiliation:
Department of Geology, Northern Illinois University, DeKalb, IL 60115, U.S.A.
Get access Rights & Permissions [Opens in a new window]

Abstract

Glauconite pellets in the Cambrian of the central U.S.A. frequently contain two textural forms of glauconite–aggregate and oriented—which differ in both mineralogy and chemistry. The aggregate glauconite composes the bulk of most pellets and consists of crystals in a nearly random arrangement. The oriented glauconite occurs primarily as rims on the periphery of pellets. It has a honeycomb-like structure—the crystals are oriented with their c-axes tangent to the aggregate-textured cores. Scanning electron photomicrographs show that the aggregate and oriented textures grade one into the other.

The aggregate glauconite has a 1 M structure and less than 5% expandable layers, whereas the oriented form has a 1 Md structure and ∼ 10% expandable layers. The aggregate glauconite contains 5–8% more total iron oxides and 2–3% less Al2O3 than the oriented glauconite. The b-cell dimension of individual samples increases nearly linearly with increasing octahedral Fe3+ + F2+ + Mg content. Chemical and crystallographic variations among various samples are, for the most part, related to the ratio of aggregate to oriented glauconite.

The transition between the texture of the aggregate and oriented glauconite suggests that some glauconite pellets may form by concretionary growth. It is proposed that Cambrian glauconite pellets grew through the repetitive development of a smectite-like clay at the margin of pellets. The smectite was later altered, both chemically and texturally, first to the oriented and then to the aggregate-textured glauconite.

Type
Research Article
Information
Clays and Clay Minerals , Volume 24 , Issue 5 , October 1976 , pp. 232 - 238
Copyright
Copyright © 1976 The Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

Footnotes

In this paper the term "glauconite" is used in a mineralogical sense to indicate an iron-rich illite-smectite of all proportions of interlayering, and the term "glauconite pellets" is used to refer to the morphological occurrences of glauconite. The term "mineral glauconite" is used to indicate glauconite containing less than 5% expandable layers and a 1 M structure.

References

Benton, Y. K. and Kastner, M. (1965) Notes on the mineralogy and origin of glauconite: J. sedim. Petrol. 35, 155–166.Google Scholar
Burst, J. F. (1958) Mineral heterogeneity in “glauconite” pellets: Am. Miner. 43, 481–497.Google Scholar
Carozzi, A. V. (1960) Microscope Sedimentary Petrology, 485 pp. Wiley, N.Y.Google Scholar
Ehlmann, H. J., Hulings, N. C. and Glover, E. D. (1963) Stages of glauconite formation in modern foraminiferal sediments: J. sedim. Petrol. 33, 87–96.Google Scholar
Hein, J. R., Allwardt, A. O. and Griggs, G. B. (1974) The occurrence of glauconite in Monterey Bay, California, diversity, origins, and sedimentary environmental significance: J. sedim. Petrol. 44, 562–571.Google Scholar
Hower, J. (1961) Some factors concerning the nature and origin of glauconite: Am. Miner. 46, 313–334.Google Scholar
McRae, S. G. (1972) Glauconite: Earth Sci. Rev. 8, 397–440.CrossRefGoogle Scholar
Shutov, V. D., Katz, M. Ya., Orits, V. A., Sokolova, A. L. and Kazakov, G. A. (1973) Crystallochemical heterogeneity of glauconite as depending on the conditions of its formation and post-sedimentary change: Proc. Int. Clay Minerals Conf., Madrid, p. 327–339.Google Scholar
Smulikowski, K. (1954) The problem of glauconite: Arch. Miner. 18, 21–120.Google Scholar
Thompson, G. R. and Hower, J. (1975) The mineralogy of glauconite: Clays & Clay Minerals 23, 289–300.CrossRefGoogle Scholar
Tripplehorn, D. N. (1966) Morphology, internal structure and origin of glauconite pellets: Sedimentology 6, 247–266.CrossRefGoogle Scholar
Warshaw, C. M. (1957) The mineralogy of glauconite: Thesis, Penn. State Univ., Univ. Park, Pa., 155 pp.Google Scholar
Wermund, E. C. (1961) Glauconite in early Tertiary sediments of the Gulf Coastal Province: Bull. Am. Ass. Pet. Geol. 45, 1667–1696.Google Scholar
Zumpe, H. H. (1971) Microstructure in Cenomanian glauconite from the Isle of Wight, England: Miner. Mag. 38, 215–224.CrossRefGoogle Scholar