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Illite K–Ar dating and crystal growth processes in diagenetic environments: a critical review
Author(s) -
Meunier Alain,
Velde Bruce,
Zalba Patricia
Publication year - 2004
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.2004.00563.x
Subject(s) - diagenesis , authigenic , illite , nucleation , k–ar dating , geology , isotopes of argon , mineralogy , radiometric dating , argon , geochemistry , clay minerals , chemistry , organic chemistry
K–Ar dating of illitic minerals is commonly used in studies of diagenetic series applied to oil prospecting. In spite of a great number of specialized papers, some problems remain unresolved. These are mostly due to a misunderstanding of the argon accumulation process during illitization. Criteria for identifying detrital–authigenic mineral mixtures, crystal ripening, fast precipitation or continuous nucleation‐growth processes are discussed using K–Ar data available in the literature. Using different parameters, such as Δ age (age K–Ar − age strati ), Δ cryst (diagenetic age K–Ar − age strati ) or Δ frac (age K–Arfraction −age K–Arfinest ), it is shown that the K–Ar age significance depends on the illite nucleation–growth processes. A ‘diagenetic age’ is obtained when these processes are rapid (the K 2 O accumulation period is shorter than 2σ). If lower than this value, the K–Ar ratio depends on the proportions of new and old particles, respectively, which are controlled by the relative rates of nucleation, crystal growth and ripening.