Hydrothermal Rhyolitic Alteration the Castle Mountains, California

Hendrik Heystek*
International Pipe and Ceramics Corp.
* 2901 Los Feliz Boulevard, Los Angeles 39, California.

Abstract: X-ray diffraction, differential thermal, chemical analysis and cation exchange data indicate a progressive genesis upon hydrothermal alteration of rhyolitic materials in an extensive fault zone. Kaolinite, a Ca-Mg beidellite, mixed-layer beidellite-hydrous mica and beidellite-vermiculite clay minerals, quartz, cristobalite and feldspar commonly occur in the deposit.

Detailed studies show that the sequence of the 2 : 1 clay mineral alteration is beidellite-hydrous mica mixed-layer → beidellite-vermiculite mixed-layer → beidellite. This mineralogical change parallels a progressive decrease in the layer charge and amount of fixed K+ present and an increase in exchangeable Ca+ and Mg+ respectively.

Clays and Clay Minerals; 1962 v. 11; no. 1; p. 158-168; DOI: 10.1346/CCMN.1962.0110114
© 1962, The Clay Minerals Society
Clay Minerals Society (www.clays.org)