Kinetic and equilibrium controls of the diagenetic illitization of smectite

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6070161

Thompson, G R; Jennings, S

X-ray diffraction, chemical, petrographic and SEM analyses of mudrock samples from borehole Borchard A-2, drilled in Plio-Pleistocene Colorado River delta mudrocks of the Imperial Valley, southern California, show a continuous mineralogical sequence from 20 to 100 percent illite layers in mixed-layer illite/smectite (M-L I/S) over the temperature range 70/sup 0/ to 210/sup 0/C. K-spar progressively decreases, but does not disappear, over the same interval. Diagenetic chlorite appears at 190/sup 0/C and kaolinite is lost at 210/sup 0/C. Ordering of the M-L I/S changes from R=0 to R=1 at 145/sup 0/C and from R=1 to Rgreater than or equal to 3 at 175/sup 0/C. There are no systematic chemical variations in the bulk fraction with depth and temperature. The <0.1 um fraction shows increases in K/sub 2/O, Al/sub 2/O/sub 3/, and decreases in SiO/sub 2/ and Fe/sub 2/O/sub 3/ with depth and temperature, variations which are compatible with progressive low-grade metamorphic illitization of smectite. Comparison of temperatures and mineral assemblages in this Plio-Pleistocene Borchard A-2 with similar low-grade metamorphic sequences of earlier Tertiary and Mesozoic ages indicate that the illitization reaction is kinetically controlled up to 175/sup 0/C and the development of Rgreater than or equal to 3 ordering, but is equilibrium controlled beyond that point.

• Research Organization: Univ. of Montana, Missoula (USA)
• OSTI ID: 6070161
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
&amp; Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CALIFORNIA
CENOZOIC ERA
CHEMISTRY
CHLORITE MINERALS
CLAYS
COHERENT SCATTERING
DIAGENESIS
DIFFRACTION
DRILL CORES
ELECTRON MICROSCOPY
EQUILIBRIUM
FEDERAL REGION IX
FELDSPARS
GEOCHEMISTRY
GEOLOGIC AGES
ILLITE
KINETICS
MICROSCOPY
MINERALOGY
MINERALS
NORTH AMERICA
OXYGEN COMPOUNDS
PETROGRAPHY
PLEISTOCENE EPOCH
PLIOCENE EPOCH
QUATERNARY PERIOD
REACTION KINETICS
SCANNING ELECTRON MICROSCOPY
SCATTERING
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SMECTITE
TEMPERATURE EFFECTS
TERTIARY PERIOD
USA
X-RAY DIFFRACTION