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(NAS Colloquium) Geology, Mineralogy, and Human Welfare (1999) / Chapter Skim
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Illite and Hydrocarbon Exploration
Pages 3440-3446

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From page 3440...
... BOX 2189, HOUStOn' TX 77252-2189 ABSTRACT Illite is a general term for the dioctahedral mica-like clay mineral common in sedimentary rocks, especially shales. Illite is of interest to the petroleum industry because it can provide a K-Ar isotope date that constrains the timing of basin heating events.
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From page 3441...
... This flattening out in the finer fractions permits us to conclude that fine detrital mica is absent in these fractions and that we have measured the mean age of illite formation. Unfortunately, diagenetic illite is not so universally abundant in sandstones as it is in shales, and not all sandstones are clean sandstones.
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From page 3442...
... and WILDFIRE (14) , which permit easy calculation of the complete powder XRD patterns of clay minerals.
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From page 3443...
... suggest. Further discussion is beyond the scope of this review, but the questions raised by the transmission electron microscopy work on illite offer exciting directions for future research.
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From page 3444...
... Certainly, the diagenetic age from IAA is a much better choice for calibrating basin thermal history than a whole rock K-Ar age from shale or the age of an arbitrary fine fraction. The 40/39Ar dating technique has been used as an ~ ~ lL , ~ ~ 1 1 0 5 10 15 20 25 30 35 40 Degrees 2 ~ FIG.
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From page 3445...
... Illite data constrain the burial or heating phase of a basin's thermal history, ~oR records maximum temperature, and apatite fission track analysis constrains timing of uplift and cooling.
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From page 3446...
... Careful mineralogical analysis using new techniques developed by the clay mineral research community permits the extraction of quantitative information on the time and temperature of diagenetic illite formation. In hydrocarbon exploration, these data are used to calibrate the heating history of sedimentary basins to ascertain that oil or gas generation from source shales postdated trap formation.
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Key Terms

  • thermal history
  • clay minerals
  • depositional age
  • diagenetic age
  • illite crystals

  • sedimentary rocks
  • detrital mica
  • xrd patterns
  • size fractions
  • clays clay

  • clay miner
  • clay mineral
  • source rocks
  • growth steps
  • trap formation

  • powder diffraction
  • xrd pattern
  • grain size
  • transmission electron
  • rotational disorder

  • electron microscopy
  • illite formation
  • xrd data
  • discrete illite
  • age analysis

  • detrital micas
  • afm deflection
  • pore fluids
  • petroleum industry
  • deflection image


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