Skip to Main Content
Book Chapter

Sources of Silica from the Illite to Muscovite Transformation During Late-Stage Diagenesis of Shales

By
Matthew W. Totten
Matthew W. Totten
Department of Geology and Geophysics, University of New Orleans, New Orleans, Louisiana 70148
Search for other works by this author on:
Harvey Blatt
Harvey Blatt
School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019
Search for other works by this author on:
Published:
January 01, 1996

Abstract

The nature of clay-mineral diagenesis in shales has received much attention because of its possible role in providing material to interbedded sandstones. In particular, the smectite to illite transformation has been cited by many authors as a source of silica during mudrock diagenesis. We suggest that illite is not an end-member itself but a transition between smectite and muscovite. This is supported by chemical and physical differences between the two minerals from the literature.

Mudrocks from the Stanley Formation (Mississippian) of the Ouachita Mountains of Oklahoma and Arkansas were investigated both chemically and petrographically to test the hypothesis that illite undergoes a continuous transformation to muscovite. Results were related to thermal maturity as determined from vitrinite reflectance data of Houseknecht and Matthews (1985) on the same samples. Within the phyllosilicate fraction, the concentration of silica was found to decrease with increasing thermal maturity. Loss of water from interlayer positions also showed a linear decrease across the same interval. This is consistent with the change of illite into muscovite mica.

Coincident with the observed changes in the phyllosilicate fraction, a corresponding increase in the amount, grain-size and percentage of composite grains was found in the non-phyllosilicate fraction. This is interpreted as the result of authigenic growth of solid silica released during clay-mineral transformations. This is consistent with reported increases in the amount of polycrystalljne quartz in metapelites compared to their precursors. Because of the increase in the percentage of quartz in metapelites, they are a likely source of abundant silt-size quartz. The approximate mass-balance of silica between the phyllosilicate and non-phyllosilicate fractions also suggests that the Stanley mudrocks behaved as closed systems during diagenesis.

You do not currently have access to this article.

Figures & Tables

Contents

SEPM Special Publication

Siliciclastic Diagenesis and Fluid Flow: Concepts and Applications

Laura J. Crossey
Laura J. Crossey
University of New Mexico Albuquerque NM
Search for other works by this author on:
Robert Loucks
Robert Loucks
ARCO Exploration Production Technology Piano TX
Search for other works by this author on:
Matthew W. Totten
Matthew W. Totten
University of New Orleans New Orleans LA
Search for other works by this author on:
Peter A Scholle
Peter A Scholle
Editor of Special Publications Special Publication No 55
Search for other works by this author on:
SEPM Society for Sedimentary Geology
Volume
55
ISBN electronic:
9781565761780
Publication date:
January 01, 1996

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal