Clays and Clay Minerals

, Volume 14, Issue 1, pp 235–240 | Cite as

Clay Mineral Formation in Sea Water by Submarine Weathering of K-Feldspar

  • R. W. Rex
  • B. D. Martin
Symposium on Genesis and Synthesis of Clay


A suite of granodiorite samples was collected by dredging from depths of about 1000 m from the walls of Carmel and Monterey submarine canyons, Monterey Bay, California. One surface of each of the various granodiorite slabs was weathered and encrusted with marine organisms. The weathering is maximum at the surface and penetrates to a depth of about 20 cm and selectively alters the feldspars to clay. Potassium feldspars are most severely altered. Mineral selective attack, shallow depth of weathering, restriction of biological growth to weathered surfaces, and regional geological setting are interpreted to mean that the samples were broken from bedrock and that this granodiorite probably weathered in the marine environment.

Authigenic clays formed as a result of the submarine weathering of the granodiorite are kaolinite, K-mica, montmorillonite, and halloysite.

These data suggest that the assemblage K-mica, montmorillonite, and kaolinite have a phase join that may lie on or close to the composition of sea water. Furthermore, kaolinite may be unstable in sea water and gradually break up to form halloysite tubes. The possible influence of biologie agents is suggested in the formation of marine halloysite.


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  1. Martin, Bruce D. (1964) Monterey submarine canyon, California: Genesis and relationship to continental geology: Unpub. Ph.D., diss., University of Southern California, Los Angeles, 249 pp.Google Scholar
  2. Rex, R. W. (1965) Authigenic kaolinite and mica as evidence for phase equilibria at low temperatures: Clays and Clay Minerals, Proc. 13th Conf., Pergamon Press, London, 95–104.Google Scholar

Copyright information

© Clay Minerals Society 1966

Authors and Affiliations

  • R. W. Rex
    • 1
  • B. D. Martin
    • 2
  1. 1.Chevron Research CompanyLa HabraUSA
  2. 2.U.S. Navy Oceanographic OfficeWashington, D.C.USA

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