Different rates of smectite illitization in mudstones and sandstones from the Niigata Basin, Japan

Abstract

The different rates of smectite illitization have been investigated in interbedded sandstone and mudstone samples from the Neogene to Lower Pleistocene stratigraphy of the Niigata sedimentary basin. For samples of approximately the same age and under the same temperature and pressure conditions, the analytical results of XRD and EDS show that differences in the transformation from R = 1 I-S to R≥3 I-S at a temperature of ~30–40°C and 1000 m in depth are determined by the initial smectite composition and the relative ion concentration of pore-fluid in the sedimentary rock system. The ordered I-S and illite in the mudstone have inherited compositional characteristics from the initial detrital smectite and illite. In the sandstone, the I-S composition was changed by interaction with pore-fluids and by precipitation and crystal growth during diagenesis.

Clay mineral diagenesis in alternating mudstone‐sandstone beds from Late Palaeozoic strata of the Anadarko Basin, United States

“…Clay mineral diagenetic reactions are numerous; however, in sedimentary basins the illitization of smectite and mixed‐layer illite–smectite is the most common mechanism of clay conversion mechanism (Hoffman and Hower, 1979; Merriman, 2005; Reynolds, 1980; Środoń, 1999; Weaver, 1956). As a result, smectite‐to‐illite transformation has been utilized to compare the rate of diagenesis in adjacent lithologies (Boles & Franks, 1979; Crossey & Larsen, 1992; Gier et al, 2015; Huggett, 1996; Howard, 1981; McKinley et al, 2003; Niu et al, 2000; Niu & Ishida, 2000). Clay mineral distribution and degree of illitization is typically driven by time, temperature, and fluid chemistry (Altaner & Bethke, 1988; Bjorlykke, 1998; Moore & Reynolds, 1997).…”

“…However, the water/rock ratio may exercise further control on the rate of illitization (Ramseyer & Boles, 1986; Uysal, Golding, & Audsley, 2000; Uysal, Golding, & Baublys, 2000), where higher degrees of illitization occur in more permeable rocks at similar depths (Crossey & Larsen, 1992; Gier et al, 2015; Hillier et al, 1996; Ko & Hesse, 1998; McKinley et al, 2003). Conversely, more advanced stages of illitization also occur in less permeable rocks (Boles & Franks, 1979; Howard, 1981; Niu et al, 2000; Niu & Ishida, 2000). Comparable rates of illitization in interbedded sandstone and mudstone have also been reported (Huggett, 1996).…”

“…By studying Tertiary strata of the Northern Sea, Huggett (1996) suggested that illitization operates at similar rates in both lithologies. Other studies, however, suggest slower rates of illitization in sandstone compared to neighbouring mudstone, which is attributed to the differences in thermal stability of smectitic precursors and variation in pore fluid compositions between sandstone and mudstone Niu & Ishida, 2000). Alternatively, others argue for Enhanced illitization in sandstone, facilitated by elevated flow rates linked to higher values of porosity and permeability in sandstone relative to mudstone (Crossey & Larsen, 1992;Gier et al, 2015;Hillier et al, 1996;Huggett, 1986).…”