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Quantitative XRD bulk and clay mineralogical determination of paleosol sections of Unayzah and Basal Khuff clastics in Saudi Arabia

  • Shouwen Shen (a1), Syed R. Zaidi (a1), Bader A. Mutairi (a2), Ahmed A. Shehry (a1), Husin Sitepu (a1), Saud A. Hamoud (a1), Fahad S. Khaldi (a1) and Fatimah A. Edhaim (a1)...


Quantitative X-ray diffraction (XRD) analysis is performed on 172 samples mainly containing paleosol sections of Unayzah and Basal Khuff clastics taken from the core of one well drilled by Saudi Aramco. Quantitative XRD bulk mineralogical determination is achieved using the Rietveld refinement method whereas quantitative XRD clay mineralogical determination of clay-size fraction is obtained using the reference intensity ratio method. The XRD results indicate that the samples from paleosol sections consist mainly of quartz and feldspar (microcline and albite) as framework constituents. Cement minerals include dolomite, hematite, anhydrite, siderite, gypsum, calcite, and pyrite. Clay minerals are important constituents in paleosols. The XRD results show that clay minerals in the samples are illite, mixed-layer illite/smectite, kaolinite, and chlorite. No discrete smectite is present in the samples. The clay mineral associations in these samples of paleosol sections can be classified into three types: Type I predominantly consists of illite and a mixed layer of illite/smectite; Type II of kaolinite; and Type III of illite and a mixed layer of illite/smectite, but also significant amounts of kaolinite. The change of clay mineral association type with sample depth can indicate the change of paleoclimate and paleoenvironment. For example, kaolinite usually forms under strongly leaching conditions such as abundant rainfall, good drainage, and acid waters. Therefore, XRD mineralogical data of paleosol sections are important for petroleum geologists to study paleoclimate and paleoenvironment and to predict the reservoir quality of the associated rock formations.


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Bish, D. L. and Howard, S. A. (1988). “Quantitative phase analysis using the Rietveld method,” J. Appl. Cryst. 21, 8691.
Bish, D. L. and Post, J. E. (1993). “Quantitative mineralogical analysis using the Rietveld full-pattern fitting method,” Am. Mineral. 78, 932940.
Blatt, H., Middleton, G., and Murray, R. (1980). “Origin of Sedimentary Rocks,” 2nd edn. (Prentice-Hall, Upper Saddle River, NJ), pp. 112113.
Chung, F. H. (1974a). “Quantitative interpretation of X-ray diffraction patterns of mixtures I. Matrix-flushing method for quantitative multicomponent analysis,” J. Appl. Cryst. 7, 519525.
Chung, F. H. (1974b). “Quantitative interpretation of X-ray diffraction patterns of mixtures II. Adiabatic principle of X-ray diffraction analysis of mixtures,” J. Appl Cryst. 7, 526531.
Gualtieri, A. F. (2000). “Accuracy of XRPD QPA using the combined Rietveld–RIR method,” J Appl. Cryst. 33, 267278.
Hillier, S. (2000). “Accurate quantitative analysis of clay and other minerals in sandstones by XRD: comparison of a Rietveld and a reference intensity ratio (RIR) method and the importance of sample preparation,” Clay Miner. 35, 291302.
Mack, G. H. and James, W. C. (1994). “Paleoclimate and the global distribution of paleosols,” J. Geol. 102, 360366.
McCusker, L. B., Von Dreele, R. B., Cox, D. E., Loüer, D., and Scardi, P. (1999). “Rietveld refinement guidelines,” J. Appl. Cryst. 32, 3650.
O'Connor, B. H. and Raven, M. D. (1988). “Application of the Rietveld refinement procedure in assaying powder mixtures,” Powder Diffr. 3, 26.
Robinson, D. and Wright, V. P. (1987). “Ordered illite-smectite and kaolinite-smectite: pedogenic mineral in a Low Carboniferous paleosol sequence, South Wales,” Clay Miner. 22, 109118.



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