Estimation of the diagenetic smectite to illite transformation

Journal Article · · American Mineralogist; (United States)

OSTI ID:6991558

Velde, B ^[1]; Vasseur, G ^[2]

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1. Ecole Normale Superieure, Paris (France)
2. Centre de Geologie et Geophysique, Cedex (France)

A model is proposed to estimate the change in expandability of illite/smectite (I/S) minerals during burial diagenesis. The model uses a classical, first-order kinetic formulation. The values of activation energy and the preexponential constant are derived empirically by fitting the expandability of I/S minerals in samples from six deep wells in three sedimentary basins (USA and Japan) that had various burial rates. The series range in age at greatest depth from 4 to 150 Ma. Present thermal gradients are assumed to have pertained during the burial history of the sediments investigated, i.e., the upper three-fourths of the basin history. The derived kinetic values were tested on a seventh, older well (France, 210 Ma at greatest depth). A one-step reaction model cannot be fitted to all of the different wells. Following mineralogical, crystallographic indications and the results of experimental studies, the I/S series was divided into two reactions: one involving the disordered R = 0 structure minerals (100 - 50% expanding layers) and the other ordered R = 1 I/S (50-0% expanding layers). Reduction of expandability of the R = 0 minerals is assumed to determine the initiation of the second reaction. The second reaction shows progressive illitization of the ordered, R = 1 mineral that initially contained 50% smectite.

• OSTI ID: 6991558
• Journal Information: American Mineralogist; (United States), Journal Name: American Mineralogist; (United States) Vol. 77:9-10; ISSN AMMIAY; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152002 -- Geothermal Data & Theory-- Properties of Minerals & Rocks
58 GEOSCIENCES
580000* -- Geosciences
ACTIVATION ENERGY
CLAYS
CRYSTAL-PHASE TRANSFORMATIONS
DIAGENESIS
ENERGY
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
ILLITE
KINETICS
MATHEMATICAL MODELS
MINERALS
ORDER-DISORDER TRANSFORMATIONS
PARTICLE MODELS
PHASE TRANSFORMATIONS
SEDIMENTARY BASINS
SILICATE MINERALS
SMECTITE
STATISTICAL MODELS
THERMODYNAMIC MODEL