Mineralogic and chemical alterations during burial in illite/smectite from Wilcox shales

Conference · Sat Sep 01 04:00:00 EDT 1984 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6426954

Whynot, J D; Moore, D W; Tieh, T T

Burial diagenesis has resulted in structural and chemical changes in mixed-layer illite/smectite from shales of the Eocene Wilcox Group, Texas. Randomly interstratified illite/smectite high in expandable layers has been converted to regularly interstratified illite/smectite low in expandable layers with increased depth of burial. This change is reflected in the K/sub 2/O content and cation exchange capacity (CEC) of the mixed-layer clay-rich fine clay size fraction. Samples high in expandable layers have a low K/sub 2/O content and high CEC; samples low in expandable layers have a high K/sub 2/O content and low CEC. Infrared spectra suggest a progressive substitution of Al/sup 3 +/ for Si/sup 4 +/ in the tetrahedral sheets of the smectite layers and preferential conversion of iron-poor smectite layers to illite. Concentrations of extractable cations over a 60 m (200 ft) thick shale sequence indicate that fluid has moved from the center to the margins of the sequence.

• Research Organization: Texas A and M Univ., College Station
• OSTI ID: 6426954
• Report Number(s): CONF-8410143-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 68:9
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
58 GEOSCIENCES
580100 -- Geology & Hydrology-- (-1989)
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CENOZOIC ERA
CHEMICAL COMPOSITION
CLAYS
DIAGENESIS
GEOLOGIC AGES
GEOLOGIC FORMATIONS
ILLITE
MINERALOGY
MINERALS
OXYGEN COMPOUNDS
RESERVOIR ROCK
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SMECTITE
TERTIARY PERIOD